Science.gov

Sample records for aerodynamic force production

  1. Aerodynamic Lifting Force.

    ERIC Educational Resources Information Center

    Weltner, Klaus

    1990-01-01

    Describes some experiments showing both qualitatively and quantitatively that aerodynamic lift is a reaction force. Demonstrates reaction forces caused by the acceleration of an airstream and the deflection of an airstream. Provides pictures of demonstration apparatus and mathematical expressions. (YP)

  2. How wing kinematics affect power requirements and aerodynamic force production in a robotic bat wing.

    PubMed

    Bahlman, Joseph W; Swartz, Sharon M; Breuer, Kenneth S

    2014-06-01

    Bats display a wide variety of behaviors that require different amounts of aerodynamic force. To control and modulate aerodynamic force, bats change wing kinematics, which, in turn, may change the power required for wing motion. There are many kinematic mechanisms that bats, and other flapping animals, can use to increase aerodynamic force, e.g. increasing wingbeat frequency or amplitude. However, we do not know if there is a difference in energetic cost between these different kinematic mechanisms. To assess the relationship between mechanical power input and aerodynamic force output across different isolated kinematic parameters, we programmed a robotic bat wing to flap over a range of kinematic parameters and measured aerodynamic force and mechanical power. We systematically varied five kinematic parameters: wingbeat frequency, wingbeat amplitude, stroke plane angle, downstroke ratio, and wing folding. Kinematic values were based on observed values from free flying Cynopterus brachyotis, the species on which the robot was based. We describe how lift, thrust, and power change with increases in each kinematic variable. We compare the power costs associated with generating additional force through the four kinematic mechanisms controlled at the shoulder, and show that all four mechanisms require approximately the same power to generate a given force. This result suggests that no single parameter offers an energetic advantage over the others. Finally, we show that retracting the wing during upstroke reduces power requirements for flapping and increases net lift production, but decreases net thrust production. These results compare well with studies performed on C. brachyotis, offering insight into natural flight kinematics.

  3. How wing kinematics affect power requirements and aerodynamic force production in a robotic bat wing.

    PubMed

    Bahlman, Joseph W; Swartz, Sharon M; Breuer, Kenneth S

    2014-06-01

    Bats display a wide variety of behaviors that require different amounts of aerodynamic force. To control and modulate aerodynamic force, bats change wing kinematics, which, in turn, may change the power required for wing motion. There are many kinematic mechanisms that bats, and other flapping animals, can use to increase aerodynamic force, e.g. increasing wingbeat frequency or amplitude. However, we do not know if there is a difference in energetic cost between these different kinematic mechanisms. To assess the relationship between mechanical power input and aerodynamic force output across different isolated kinematic parameters, we programmed a robotic bat wing to flap over a range of kinematic parameters and measured aerodynamic force and mechanical power. We systematically varied five kinematic parameters: wingbeat frequency, wingbeat amplitude, stroke plane angle, downstroke ratio, and wing folding. Kinematic values were based on observed values from free flying Cynopterus brachyotis, the species on which the robot was based. We describe how lift, thrust, and power change with increases in each kinematic variable. We compare the power costs associated with generating additional force through the four kinematic mechanisms controlled at the shoulder, and show that all four mechanisms require approximately the same power to generate a given force. This result suggests that no single parameter offers an energetic advantage over the others. Finally, we show that retracting the wing during upstroke reduces power requirements for flapping and increases net lift production, but decreases net thrust production. These results compare well with studies performed on C. brachyotis, offering insight into natural flight kinematics. PMID:24851830

  4. Aerodynamic Forces on a Vibrating Unstaggered Cascade

    NASA Technical Reports Server (NTRS)

    Soehngen, H.

    1957-01-01

    The unsteady aerodynamic forces, [based on two-dimensional incompressible flow considerations], are determined for an unstaggered cascade, the blades of which are vibrating in phase in an approach flow parallel to the blades.

  5. Wing inertia and whole-body acceleration: an analysis of instantaneous aerodynamic force production in cockatiels (Nymphicus hollandicus) flying across a range of speeds.

    PubMed

    Hedrick, Tyson L; Usherwood, James R; Biewener, Andrew A

    2004-04-01

    We used a combination of high-speed 3-D kinematics and three-axis accelerometer recordings obtained from cockatiels flying in a low-turbulence wind tunnel to characterize the instantaneous accelerations and, by extension, the net aerodynamic forces produced throughout the wingbeat cycle across a broad range of flight speeds (1-13 m s(-1)). Our goals were to investigate the variation in instantaneous aerodynamic force production during the wingbeat cycle of birds flying across a range of steady speeds, testing two predictions regarding aerodynamic force generation in upstroke and the commonly held assumption that all of the kinetic energy imparted to the wings of a bird in flapping flight is recovered as useful aerodynamic work. We found that cockatiels produce only a limited amount of lift during upstroke (14% of downstroke lift) at slower flight speeds (1-3 m s(-1)). Upstroke lift at intermediate flight speeds (7-11 m s(-1)) was moderate, averaging 39% of downstroke lift. Instantaneous aerodynamic forces were greatest near mid-downstroke. At the end of each half-stroke, during wing turnaround, aerodynamic forces were minimal, but inertial forces created by wing motion were large. However, we found that the inertial power requirements of downstroke (minimum of 0.29+/-0.10 W at 7 m s(-1) and maximum of 0.56+/-0.13 W at 1 m s(-1)) were consistent with the assumption that nearly all wing kinetic energy in downstroke was applied to the production of aerodynamic forces and therefore should not be added separately to the overall power cost of flight. The inertial power requirements of upstroke (minimum of 0.16+/-0.04 W at 7 m s(-1) and maximum of 0.35+/-0.11 W at 1 m s(-1)) cannot be recovered in a similar manner, but their magnitude was such that the power requirements for the upstroke musculature (minimum of 54+/-13 W kg(-1) at 7 m s(-1) and maximum of 122+/-35 W at 1 m s(-1)) fall within the established range for cockatiel flight muscle (<185 W kg(-1)).

  6. Wing inertia and whole-body acceleration: an analysis of instantaneous aerodynamic force production in cockatiels (Nymphicus hollandicus) flying across a range of speeds.

    PubMed

    Hedrick, Tyson L; Usherwood, James R; Biewener, Andrew A

    2004-04-01

    We used a combination of high-speed 3-D kinematics and three-axis accelerometer recordings obtained from cockatiels flying in a low-turbulence wind tunnel to characterize the instantaneous accelerations and, by extension, the net aerodynamic forces produced throughout the wingbeat cycle across a broad range of flight speeds (1-13 m s(-1)). Our goals were to investigate the variation in instantaneous aerodynamic force production during the wingbeat cycle of birds flying across a range of steady speeds, testing two predictions regarding aerodynamic force generation in upstroke and the commonly held assumption that all of the kinetic energy imparted to the wings of a bird in flapping flight is recovered as useful aerodynamic work. We found that cockatiels produce only a limited amount of lift during upstroke (14% of downstroke lift) at slower flight speeds (1-3 m s(-1)). Upstroke lift at intermediate flight speeds (7-11 m s(-1)) was moderate, averaging 39% of downstroke lift. Instantaneous aerodynamic forces were greatest near mid-downstroke. At the end of each half-stroke, during wing turnaround, aerodynamic forces were minimal, but inertial forces created by wing motion were large. However, we found that the inertial power requirements of downstroke (minimum of 0.29+/-0.10 W at 7 m s(-1) and maximum of 0.56+/-0.13 W at 1 m s(-1)) were consistent with the assumption that nearly all wing kinetic energy in downstroke was applied to the production of aerodynamic forces and therefore should not be added separately to the overall power cost of flight. The inertial power requirements of upstroke (minimum of 0.16+/-0.04 W at 7 m s(-1) and maximum of 0.35+/-0.11 W at 1 m s(-1)) cannot be recovered in a similar manner, but their magnitude was such that the power requirements for the upstroke musculature (minimum of 54+/-13 W kg(-1) at 7 m s(-1) and maximum of 122+/-35 W at 1 m s(-1)) fall within the established range for cockatiel flight muscle (<185 W kg(-1)). PMID:15073202

  7. Unsteady Aerodynamic Force Sensing from Measured Strain

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi

    2016-01-01

    A simple approach for computing unsteady aerodynamic forces from simulated measured strain data is proposed in this study. First, the deflection and slope of the structure are computed from the unsteady strain using the two-step approach. Velocities and accelerations of the structure are computed using the autoregressive moving average model, on-line parameter estimator, low-pass filter, and a least-squares curve fitting method together with analytical derivatives with respect to time. Finally, aerodynamic forces over the wing are computed using modal aerodynamic influence coefficient matrices, a rational function approximation, and a time-marching algorithm. A cantilevered rectangular wing built and tested at the NASA Langley Research Center (Hampton, Virginia, USA) in 1959 is used to validate the simple approach. Unsteady aerodynamic forces as well as wing deflections, velocities, accelerations, and strains are computed using the CFL3D computational fluid dynamics (CFD) code and an MSC/NASTRAN code (MSC Software Corporation, Newport Beach, California, USA), and these CFL3D-based results are assumed as measured quantities. Based on the measured strains, wing deflections, velocities, accelerations, and aerodynamic forces are computed using the proposed approach. These computed deflections, velocities, accelerations, and unsteady aerodynamic forces are compared with the CFL3D/NASTRAN-based results. In general, computed aerodynamic forces based on the lifting surface theory in subsonic speeds are in good agreement with the target aerodynamic forces generated using CFL3D code with the Euler equation. Excellent aeroelastic responses are obtained even with unsteady strain data under the signal to noise ratio of -9.8dB. The deflections, velocities, and accelerations at each sensor location are independent of structural and aerodynamic models. Therefore, the distributed strain data together with the current proposed approaches can be used as distributed deflection

  8. In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.

    PubMed

    Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers

    2015-03-01

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing.

  9. In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds

    PubMed Central

    Lentink, David; Haselsteiner, Andreas F.; Ingersoll, Rivers

    2015-01-01

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier–Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing. PMID:25589565

  10. In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.

    PubMed

    Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers

    2015-03-01

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing. PMID:25589565

  11. Vortical sources of aerodynamic force and moment

    NASA Technical Reports Server (NTRS)

    Wu, J. Z.; Wu, J. M.

    1989-01-01

    It is shown that the aerodynamic force and moment can be expressed in terms of vorticity distribution (and entropy variation for compressible flow) on near wake plane, or in terms of boundary vorticity flux on the body surface. Thus the vortical sources of lift and drag are clearly identified, which is the real physical basis of optimal aerodynamic design. Moreover, these sources are highly compact, hence allowing one to concentrate on key local regions of the configuration, which have dominating effect to the lift and drag. A detail knowledge of the vortical low requires measuring or calculating the vorticity and dilatation field, which is however still a challenging task. Nevertheless, this type of formulation has some unique advantages; and how to set up a well-posed problem, in particular how to establish vorticity-dilatation boundary conditions, is addressed.

  12. Force measurements in aerodynamics using piezoelectric multicomponent force transducers

    NASA Astrophysics Data System (ADS)

    Schewe, G.

    The present paper is concerned with a device for the measurement of steady and unsteady aerodynamic forces in a wind tunnel test. The paper represents a continuation of an article written by Schewe (1982) about a multicomponent balance consisting of piezoelectric force transducers for a high-pressure wind tunnel. Advantages of the piezoelectric force-measuring technique compared to other techniques are related to the high rigidity of the quartz crystal sensor elements, taking into account low interference (cross talk) for multicomponent measurements, high natural frequency, and broad dynamic range. It is pointed out that the limitations with respect to quasi-static measurements imposed by the drift of the zero point are not as extensive as generally believed, while drift correction methods improve the measurement accuracy.

  13. Fluidic Control of Aerodynamic Forces on an Axisymmetric Body

    NASA Astrophysics Data System (ADS)

    Abramson, Philip; Vukasinovic, Bojan; Glezer, Ari

    2007-11-01

    The aerodynamic forces and moments on a wind tunnel model of an axisymmetric bluff body are modified by induced local vectoring of the separated base flow. Control is effected by an array of four integrated aft-facing synthetic jets that emanate from narrow, azimuthally-segmented slots, equally distributed around the perimeter of the circular tail end within a small backward facing step that extends into a Coanda surface. The model is suspended in the wind tunnel by eight thin wires for minimal support interference with the wake. Fluidic actuation results in a localized, segmented vectoring of the separated base flow along the rear Coanda surface and induces asymmetric aerodynamic forces and moments to effect maneuvering during flight. The aerodynamic effects associated with quasi-steady and transitory differential, asymmetric activation of the Coanda effect are characterized using direct force and PIV measurements.

  14. Aeroacoustics. [analysis of properties of sound generated by aerodynamic forces

    NASA Technical Reports Server (NTRS)

    Goldstein, M., E.

    1974-01-01

    An analysis was conducted to determine the properties of sound generated by aerodynamic forces or motions originating in a flow, such as the unsteady aerodynamic forces on propellers or by turbulent flows around an aircraft. The acoustics of moving media are reviewed and mathematical models are developed. Lighthill's acoustic analogy and the application to turbulent flows are analyzed. The effects of solid boundaries are calculated. Theories based on the solution of linearized vorticity and acoustic field equations are explained. The effects of nonuniform mean flow on the generation of sound are reported.

  15. Aerodynamic side-force alleviator means

    NASA Technical Reports Server (NTRS)

    Rao, D. M. (Inventor)

    1980-01-01

    An apparatus for alleviating high angle of attack side force on slender pointed cylindrical forebodies such as fighter aircraft, missiles and the like is described. A symmetrical pair of helical separation trips was employed to disrupt the leeside vortices normally attained. The symmetrical pair of trips starts at either a common point or at space points on the upper surface of the forebody and extends along separate helical paths along the circumference of the forebody.

  16. The Aerodynamic Forces on Airship Hulls

    NASA Technical Reports Server (NTRS)

    Munk, M. M.

    1979-01-01

    The new method for making computations in connection with the study of rigid airships, which was used in the investigation of Navy's ZR-1 by the special subcommittee of the National Advisory Committee for Aeronautics appointed for this purpose is presented. The general theory of the air forces on airship hulls of the type mentioned is described and an attempt was made to develop the results from the very fundamentals of mechanics.

  17. Notes on aerodynamic forces 1 : rectilinear motion

    NASA Technical Reports Server (NTRS)

    Munk, Max M

    1922-01-01

    The study of the motion of perfect fluids is of paramount importance for the understanding of the chief phenomena occurring in the air surrounding an aircraft, and for the numerical determination of their effects. The author recently successfully employed some simple methods for the investigation of the flow of a perfect fluid that have never been mentioned in connection with aeronautical problems. These methods appeal particularly to the engineer who is untrained in performing laborious mathematical computations, as they do away with these and allow one to obtain many interesting results by the mere application of some general and well-known principles of mechanics. Discussed here are the kinetic energy of moving fluids, the momentum of a body in a perfect fluid, two dimensional flow, three dimensional flow, and the distribution of the transverse forces of very elongated surfaces of revolution.

  18. Calculation of subsonic and supersonic steady and unsteady aerodynamic forces using velocity potential aerodynamic elements

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.; Yoo, Y. S.

    1976-01-01

    Expressions for calculation of subsonic and supersonic, steady and unsteady aerodynamic forces are derived, using the concept of aerodynamic elements applied to the downwash velocity potential method. Aerodynamic elements can be of arbitrary out of plane polygon shape, although numerical calculations are restricted to rectangular elements, and to the steady state case in the supersonic examples. It is suggested that the use of conforming, in place of rectangular elements, would give better results. Agreement with results for subsonic oscillating T tails is fair, but results do not converge as the number of collocation points is increased. This appears to be due to the form of expression used in the calculations. The methods derived are expected to facilitate automated flutter analysis on the computer. In particular, the aerodynamic element concept is consistent with finite element methods already used for structural analysis. The method is universal for the complete Mach number range, and, finally, the calculations can be arranged so that they do not have to be repeated completely for every reduced frequency.

  19. Kinematic control of aerodynamic forces on an inclined flapping wing with asymmetric strokes.

    PubMed

    Park, Hyungmin; Choi, Haecheon

    2012-03-01

    In the present study, we conduct an experiment using a one-paired dynamically scaled model of an insect wing, to investigate how asymmetric strokes with different wing kinematic parameters are used to control the aerodynamics of a dragonfly-like inclined flapping wing in still fluid. The kinematic parameters considered are the angles of attack during the mid-downstroke (α(md)) and mid-upstroke (α(mu)), and the duration (Δτ) and time of initiation (τ(p)) of the pitching rotation. The present dragonfly-like inclined flapping wing has the aerodynamic mechanism of unsteady force generation similar to those of other insect wings in a horizontal stroke plane, but the detailed effect of the wing kinematics on the force control is different due to the asymmetric use of the angle of attack during the up- and downstrokes. For example, high α(md) and low α(mu) produces larger vertical force with less aerodynamic power, and low α(md) and high α(mu) is recommended for horizontal force (thrust) production. The pitching rotation also affects the aerodynamics of a flapping wing, but its dynamic rotational effect is much weaker than the effect from the kinematic change in the angle of attack caused by the pitching rotation. Thus, the influences of the duration and timing of pitching rotation for the present inclined flapping wing are found to be very different from those for a horizontal flapping wing. That is, for the inclined flapping motion, the advanced and delayed rotations produce smaller vertical forces than the symmetric one and the effect of pitching duration is very small. On the other hand, for a specific range of pitching rotation timing, delayed rotation requires less aerodynamic power than the symmetric rotation. As for the horizontal force, delayed rotation with low α(md) and high α(mu) is recommended for long-duration flight owing to its high efficiency, and advanced rotation should be employed for hovering flight for nearly zero horizontal force. The

  20. Kinematic control of aerodynamic forces on an inclined flapping wing with asymmetric strokes.

    PubMed

    Park, Hyungmin; Choi, Haecheon

    2012-03-01

    In the present study, we conduct an experiment using a one-paired dynamically scaled model of an insect wing, to investigate how asymmetric strokes with different wing kinematic parameters are used to control the aerodynamics of a dragonfly-like inclined flapping wing in still fluid. The kinematic parameters considered are the angles of attack during the mid-downstroke (α(md)) and mid-upstroke (α(mu)), and the duration (Δτ) and time of initiation (τ(p)) of the pitching rotation. The present dragonfly-like inclined flapping wing has the aerodynamic mechanism of unsteady force generation similar to those of other insect wings in a horizontal stroke plane, but the detailed effect of the wing kinematics on the force control is different due to the asymmetric use of the angle of attack during the up- and downstrokes. For example, high α(md) and low α(mu) produces larger vertical force with less aerodynamic power, and low α(md) and high α(mu) is recommended for horizontal force (thrust) production. The pitching rotation also affects the aerodynamics of a flapping wing, but its dynamic rotational effect is much weaker than the effect from the kinematic change in the angle of attack caused by the pitching rotation. Thus, the influences of the duration and timing of pitching rotation for the present inclined flapping wing are found to be very different from those for a horizontal flapping wing. That is, for the inclined flapping motion, the advanced and delayed rotations produce smaller vertical forces than the symmetric one and the effect of pitching duration is very small. On the other hand, for a specific range of pitching rotation timing, delayed rotation requires less aerodynamic power than the symmetric rotation. As for the horizontal force, delayed rotation with low α(md) and high α(mu) is recommended for long-duration flight owing to its high efficiency, and advanced rotation should be employed for hovering flight for nearly zero horizontal force. The

  1. Concentrating reflector for solar radiation of low aerodynamic friction force and high aerodynamic buoyancy force

    SciTech Connect

    Radebold, R.

    1984-03-27

    Solar energy is focused by a paraboloidally curved, specularly reflective foil inside the wing of an aircraft having a transparent upper surface in whose rudder structure is disposed the radiation receiver. This particular reflector offers very low resistance to ambient wind forces.

  2. Predicted and experimental aerodynamic forces on the Darrieus rotor

    NASA Astrophysics Data System (ADS)

    Paraschivoiu, I.

    1983-12-01

    The present paper compares the aerodynamic loads predicted by a double-multiple-streamtube model with wind tunnel measurements for a straight-bladed Darrieus rotor. Thus the CARDAA computer code uses two constant-interference factors in the induced velocity for estimating the aerodynamic loads. This code has been improved by considering the variation in the upwind and downwind induced velocities as a function of the blade position, and, in this case, the CARDAAV code is used. The Boeing-Vertol dynamic-stall model is incorporated in both the CARDAA and CARDAAV codes, and a better approach is obtained. The transient normal- and tangential-force coefficients predicted with and without dynamic-stall effects are compared with wind tunnel data for one and two NACA 0018 straight-bladed rotors. The results are given for a rotor with a large solidity (chord-to-radius ratio of 0.20) at two tip-speed ratios (X = 1.5 and 3.0) and at a low Reynolds number of 3.8 x 10 to the 4th. The comparisons between experimental data and theoretical results show the CARDAAV predictions to be more accurate than those estimated by the CARDAA code.

  3. Estimation of unsteady aerodynamic forces using pointwise velocity data

    NASA Astrophysics Data System (ADS)

    Gómez, F.; Sharma, A. S.; Blackburn, H. M.

    2016-10-01

    A novel method to estimate unsteady aerodynamic force coefficients from pointwise velocity measurements is presented. The methodology is based on a resolvent-based reduced-order model which requires the mean flow to obtain physical flow structures and pointwise measurement to calibrate their amplitudes. A computationally-affordable time-stepping methodology to obtain resolvent modes in non-trivial flow domains is introduced and compared to previous existing matrix-free and matrix-forming strategies. The technique is applied to the unsteady flow around an inclined square cylinder at low Reynolds number. The potential of the methodology is demonstrated through good agreement between the fluctuating pressure distribution on the cylinder and the temporal evolution of the unsteady lift and drag coefficients predicted by the model and those computed by direct numerical simulation.

  4. Aerodynamic forces and vortical structures in flapping butterfly's forward flight

    NASA Astrophysics Data System (ADS)

    Yokoyama, Naoto; Senda, Kei; Iima, Makoto; Hirai, Norio

    2013-02-01

    Forward flights of a bilaterally symmetrically flapping butterfly modeled as a four-link rigid-body system consisting of a thorax, an abdomen, and left and right wings are numerically simulated. The joint motions of the butterflies are adopted from experimental observations. Three kinds of the simulations, distinguished by ways to determine the position and attitude of the thorax, are carried out: a tethered simulation, a prescribed simulation, and free-flight simulations. The upward and streamwise forces as well as the wake structures in the tethered simulation, where the thorax of the butterfly is fixed, reasonably agree with those in the corresponding tethered experiment. In the prescribed simulation, where the thoracic trajectories as well as the joint angles are given by those observed in a free-flight experiment, it is confirmed that the butterfly can produce enough forces to achieve the flapping flights. Moreover, coherent vortical structures in the wake and those on the wings are identified. The generation of the aerodynamic forces due to the vortical structures are also clarified. In the free-flight simulation, where only the joint angles are given as periodic functions of time, it is found that the free flight is longitudinally unstable because the butterfly cannot maintain the attitude in a proper range. Focusing on the abdominal mass, which largely varies owing to feeding and metabolizing, we have shown that the abdominal motion plays an important role in periodic flights. The necessity of control of the thoracic attitude for periodic flights and maneuverability is also discussed.

  5. Force balance in the take-off of a pierid butterfly: relative importance and timing of leg impulsion and aerodynamic forces.

    PubMed

    Bimbard, Gaëlle; Kolomenskiy, Dmitry; Bouteleux, Olivier; Casas, Jérôme; Godoy-Diana, Ramiro

    2013-09-15

    Up to now, the take-off stage has remained an elusive phase of insect flight that was relatively poorly explored compared with other maneuvers. An overall assessment of the different mechanisms involved in force production during take-off has never been explored. Focusing on the first downstroke, we have addressed this problem from a force balance perspective in butterflies taking off from the ground. In order to determine whether the sole aerodynamic wing force could explain the observed motion of the insect, we have firstly compared a simple analytical model of the wing force with the acceleration of the insect's center of mass estimated from video tracking of the wing and body motions. Secondly, wing kinematics were also used for numerical simulations of the aerodynamic flow field. Similar wing aerodynamic forces were obtained by the two methods. However, neither are sufficient, nor is the inclusion of the ground effect, to predict faithfully the body acceleration. We have to resort to the leg forces to obtain a model that best fits the data. We show that the median and hind legs display an active extension responsible for the initiation of the upward motion of the insect's body, occurring before the onset of the wing downstroke. We estimate that legs generate, at various times, an upward force that can be much larger than all other forces applied to the insect's body. The relative timing of leg and wing forces explains the large variability of trajectories observed during the maneuvers.

  6. Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.

    PubMed

    Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

    2013-09-01

    The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff

  7. Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.

    PubMed

    Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

    2013-09-01

    The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff.

  8. Wind Tunnel Testing on Crosswind Aerodynamic Forces Acting on Railway Vehicles

    NASA Astrophysics Data System (ADS)

    Kwon, Hyeok-Bin; Nam, Seong-Won; You, Won-Hee

    This study is devoted to measure the aerodynamic forces acting on two railway trains, one of which is a high-speed train at 300km/h maximum operation speed, and the other is a conventional train at the operating speed 100km/h. The three-dimensional train shapes have been modeled as detailed as possible including the inter-car, the upper cavity for pantograph, and the bogie systems. The aerodynamic forces on each vehicle of the trains have been measured in the subsonic wind tunnel with 4m×3m test section of Korea Aerospace Research Institute at Daejeon, Korea. The aerodynamic forces and moments of the train models have been plotted for various yaw angles and the characteristics of the aerodynamic coefficients has been discussed relating to the experimental conditions.

  9. Flutter and forced response of turbomachinery with frequency mistuning and aerodynamic asymmetry

    NASA Astrophysics Data System (ADS)

    Miyakozawa, Tomokazu

    This dissertation provides numerical studies to improve bladed disk assembly design for preventing blade high cycle fatigue failures. The analyses are divided into two major subjects. For the first subject presented in Chapter 2, the mechanisms of transonic fan flutter for tuned systems are studied to improve the shortcoming of traditional method for modern fans using a 3D time-linearized Navier-Stokes solver. Steady and unsteady flow parameters including local work on the blade surfaces are investigated. It was found that global local work monotonically became more unstable on the pressure side due to the flow rollback effect. The local work on the suction side significantly varied due to nodal diameter and flow rollback effect. Thus, the total local work for the least stable mode is dominant by the suction side. Local work on the pressure side appears to be affected by the shock on the suction side. For the second subject presented in Chapter 3, sensitivity studies are conducted on flutter and forced response due to frequency mistuning and aerodynamic asymmetry using the single family of modes approach by assuming manufacturing tolerance. The unsteady aerodynamic forces are computed using CFD methods assuming aerodynamic symmetry. The aerodynamic asymmetry is applied by perturbing the influence coefficient matrix. These aerodynamic perturbations influence both stiffness and damping while traditional frequency mistuning analysis only perturbs the stiffness. Flutter results from random aerodynamic perturbations of all blades showed that manufacturing variations that effect blade unsteady aerodynamics may cause a stable, perfectly symmetric engine to flutter. For forced response, maximum blade amplitudes are significantly influenced by the aerodynamic perturbation of the imaginary part (damping) of unsteady aerodynamic modal forces. This is contrary to blade frequency mistuning where the stiffness perturbation dominates.

  10. Aerodynamic forces induced by controlled transitory flow on a body of revolution

    NASA Astrophysics Data System (ADS)

    Rinehart, Christopher S.

    The aerodynamic forces and moments on an axisymmetric body of revolution are controlled in a low-speed wind tunnel by induced local flow attachment. Control is effected by an array of aft-facing synthetic jets emanating from narrow, azimuthally segmented slots embedded within an axisymmetric backward facing step. The actuation results in a localized, segmented vectoring of the separated base flow along a rear Coanda surface and induced asymmetric aerodynamic forces and moments. The observed effects are investigated in both quasi-steady and transient states, with emphasis on parametric dependence. It is shown that the magnitude of the effected forces can be substantially increased by slight variations of the Coanda surface geometry. Force and velocity measurements are used to elucidate the mechanisms by which the synthetic jets produce asymmetric aerodynamic forces and moments, demonstrating a novel method to steer axisymmetric bodies during flight.

  11. Wing and body motion and aerodynamic and leg forces during take-off in droneflies.

    PubMed

    Chen, Mao Wei; Zhang, Yan Lai; Sun, Mao

    2013-12-01

    Here, we present a detailed analysis of the take-off mechanics in droneflies performing voluntary take-offs. Wing and body kinematics of the insects during take-off were measured using high-speed video techniques. Based on the measured data, the inertia force acting on the insect was computed and the aerodynamic force of the wings was calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. In take-off, a dronefly increases its stroke amplitude gradually in the first 10-14 wingbeats and becomes airborne at about the 12th wingbeat. The aerodynamic force increases monotonously from zero to a value a little larger than its weight, and the leg force decreases monotonously from a value equal to its weight to zero, showing that the droneflies do not jump and only use aerodynamic force of flapping wings to lift themselves into the air. Compared with take-offs in insects in previous studies, in which a very large force (5-10 times of the weight) generated either by jumping legs (locusts, milkweed bugs and fruit flies) or by the 'fling' mechanism of the wing pair (butterflies) is used in a short time, the take-off in the droneflies is relatively slow but smoother. PMID:24132205

  12. Wing and body motion and aerodynamic and leg forces during take-off in droneflies.

    PubMed

    Chen, Mao Wei; Zhang, Yan Lai; Sun, Mao

    2013-12-01

    Here, we present a detailed analysis of the take-off mechanics in droneflies performing voluntary take-offs. Wing and body kinematics of the insects during take-off were measured using high-speed video techniques. Based on the measured data, the inertia force acting on the insect was computed and the aerodynamic force of the wings was calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. In take-off, a dronefly increases its stroke amplitude gradually in the first 10-14 wingbeats and becomes airborne at about the 12th wingbeat. The aerodynamic force increases monotonously from zero to a value a little larger than its weight, and the leg force decreases monotonously from a value equal to its weight to zero, showing that the droneflies do not jump and only use aerodynamic force of flapping wings to lift themselves into the air. Compared with take-offs in insects in previous studies, in which a very large force (5-10 times of the weight) generated either by jumping legs (locusts, milkweed bugs and fruit flies) or by the 'fling' mechanism of the wing pair (butterflies) is used in a short time, the take-off in the droneflies is relatively slow but smoother.

  13. Wing and body motion and aerodynamic and leg forces during take-off in droneflies

    PubMed Central

    Chen, Mao Wei; Zhang, Yan Lai; Sun, Mao

    2013-01-01

    Here, we present a detailed analysis of the take-off mechanics in droneflies performing voluntary take-offs. Wing and body kinematics of the insects during take-off were measured using high-speed video techniques. Based on the measured data, the inertia force acting on the insect was computed and the aerodynamic force of the wings was calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. In take-off, a dronefly increases its stroke amplitude gradually in the first 10–14 wingbeats and becomes airborne at about the 12th wingbeat. The aerodynamic force increases monotonously from zero to a value a little larger than its weight, and the leg force decreases monotonously from a value equal to its weight to zero, showing that the droneflies do not jump and only use aerodynamic force of flapping wings to lift themselves into the air. Compared with take-offs in insects in previous studies, in which a very large force (5–10 times of the weight) generated either by jumping legs (locusts, milkweed bugs and fruit flies) or by the ‘fling’ mechanism of the wing pair (butterflies) is used in a short time, the take-off in the droneflies is relatively slow but smoother. PMID:24132205

  14. Hovering flight in the honeybee Apis mellifera: kinematic mechanisms for varying aerodynamic forces.

    PubMed

    Vance, Jason T; Altshuler, Douglas L; Dickson, William B; Dickinson, Michael H; Roberts, Stephen P

    2014-01-01

    During hovering flight, animals can increase the wing velocity and therefore the net aerodynamic force per stroke by increasing wingbeat frequency, wing stroke amplitude, or both. The magnitude and orientation of aerodynamic forces are also influenced by the geometric angle of attack, timing of wing rotation, wing contact, and pattern of deviation from the primary stroke plane. Most of the kinematic data available for flying animals are average values for wing stroke amplitude and wingbeat frequency because these features are relatively easy to measure, but it is frequently suggested that the more subtle and difficult-to-measure features of wing kinematics can explain variation in force production for different flight behaviors. Here, we test this hypothesis with multicamera high-speed recording and digitization of wing kinematics of honeybees (Apis mellifera) hovering and ascending in air and hovering in a hypodense gas (heliox: 21% O2, 79% He). Bees employed low stroke amplitudes (86.7° ± 7.9°) and high wingbeat frequencies (226.8 ± 12.8 Hz) when hovering in air. When ascending in air or hovering in heliox, bees increased stroke amplitude by 30%-45%, which yielded a much higher wing tip velocity relative to that during simple hovering in air. Across the three flight conditions, there were no statistical differences in the amplitude of wing stroke deviation, minimum and stroke-averaged geometric angle of attack, maximum wing rotation velocity, or even wingbeat frequency. We employed a quasi-steady aerodynamic model to estimate the effects of wing tip velocity and geometric angle of attack on lift and drag. Lift forces were sensitive to variation in wing tip velocity, whereas drag was sensitive to both variation in wing tip velocity and angle of attack. Bees utilized kinematic patterns that did not maximize lift production but rather maintained lift-to-drag ratio. Thus, our data indicate that, at least for honeybees, the overall time course of wing angles is

  15. Hovering flight in the honeybee Apis mellifera: kinematic mechanisms for varying aerodynamic forces.

    PubMed

    Vance, Jason T; Altshuler, Douglas L; Dickson, William B; Dickinson, Michael H; Roberts, Stephen P

    2014-01-01

    During hovering flight, animals can increase the wing velocity and therefore the net aerodynamic force per stroke by increasing wingbeat frequency, wing stroke amplitude, or both. The magnitude and orientation of aerodynamic forces are also influenced by the geometric angle of attack, timing of wing rotation, wing contact, and pattern of deviation from the primary stroke plane. Most of the kinematic data available for flying animals are average values for wing stroke amplitude and wingbeat frequency because these features are relatively easy to measure, but it is frequently suggested that the more subtle and difficult-to-measure features of wing kinematics can explain variation in force production for different flight behaviors. Here, we test this hypothesis with multicamera high-speed recording and digitization of wing kinematics of honeybees (Apis mellifera) hovering and ascending in air and hovering in a hypodense gas (heliox: 21% O2, 79% He). Bees employed low stroke amplitudes (86.7° ± 7.9°) and high wingbeat frequencies (226.8 ± 12.8 Hz) when hovering in air. When ascending in air or hovering in heliox, bees increased stroke amplitude by 30%-45%, which yielded a much higher wing tip velocity relative to that during simple hovering in air. Across the three flight conditions, there were no statistical differences in the amplitude of wing stroke deviation, minimum and stroke-averaged geometric angle of attack, maximum wing rotation velocity, or even wingbeat frequency. We employed a quasi-steady aerodynamic model to estimate the effects of wing tip velocity and geometric angle of attack on lift and drag. Lift forces were sensitive to variation in wing tip velocity, whereas drag was sensitive to both variation in wing tip velocity and angle of attack. Bees utilized kinematic patterns that did not maximize lift production but rather maintained lift-to-drag ratio. Thus, our data indicate that, at least for honeybees, the overall time course of wing angles is

  16. A Basic Study on Countermeasure Against Aerodynamic Force Acting on Train Running Inside Tunnel Using Air Blowing

    NASA Astrophysics Data System (ADS)

    Suzuki, Masahiro; Nakade, Koji

    A basic study of flow controls using air blowing was conducted to reduce unsteady aerodynamic force acting on trains running in tunnels. An air blowing device is installed around a model car in a wind tunnel. Steady and periodic blowings are examined utilizing electromagnetic valves. Pressure fluctuations are measured and the aerodynamic force acting on the car is estimated. The results are as follows: a) The air blowing allows reducing the unsteady aerodynamic force. b) It is effective to blow air horizontally at the lower side of the car facing the tunnel wall. c) The reduction rate of the unsteady aerodynamic force relates to the rate of momentum of the blowing to that of the uniform flow. d) The periodic blowing with the same frequency as the unsteady aerodynamic force reduces the aerodynamic force in a manner similar to the steady blowing.

  17. The roles of aerodynamic and inertial forces on maneuverability in flapping flight

    NASA Astrophysics Data System (ADS)

    Vejdani, Hamid; Boerma, David; Swartz, Sharon; Breuer, Kenneth

    2015-11-01

    We investigate the relative contributions of aerodynamic and the whole-body dynamics in generating extreme maneuvers. We developed a 3D dynamical model of a body (trunk) and two rectangular wings using a Lagrangian formulation. The trunk has 6 degrees of freedom and each wing has 4 degrees of actuation (flapping, sweeping, wing pronation/supination and wing extension/flexion) and can be massless (like insect wings) or relatively massive (like bats). To estimate aerodynamic forces, we use a blade element method; drag and lift are calculated using a quasi-steady model. We validated our model using several benchmark tests, including gliding and hovering motion. To understand the roles of aerodynamic and inertial forces, we start the investigation by constraining the wing motion to flapping and wing length extension/flexion motion. This decouples the trunk degrees of freedom and affects only roll motion. For bats' dynamics (massive wings), the model is much more maneuverable than the insect dynamics case, and the effect of inertial forces dominates the behavior of the system. The role of the aerodynamic forces increases when the wings have sweeping and flapping motion, which affects the pitching motion of the body. We also analyzed the effect of all wing motions together on the behavior of the model in the presence and in the absence of aerodynamic forces.

  18. Modeling of Aerodynamic Force Acting in Tunnel for Analysis of Riding Comfort in a Train

    NASA Astrophysics Data System (ADS)

    Kikko, Satoshi; Tanifuji, Katsuya; Sakanoue, Kei; Nanba, Kouichiro

    In this paper, we aimed to model the aerodynamic force that acts on a train running at high speed in a tunnel. An analytical model of the aerodynamic force is developed from pressure data measured on car-body sides of a test train running at the maximum revenue operation speed. The simulation of an 8-car train running while being subjected to the modeled aerodynamic force gives the following results. The simulated car-body vibration corresponds to the actual vibration both qualitatively and quantitatively for the cars at the rear of the train. The separation of the airflow at the tail-end of the train increases the yawing vibration of the tail-end car while it has little effect on the car-body vibration of the adjoining car. Also, the effect of the moving velocity of the aerodynamic force on the car-body vibration is clarified that the simulation under the assumption of a stationary aerodynamic force can markedly increase the car-body vibration.

  19. Modal forced vibration analysis of aerodynamically excited turbosystems

    NASA Technical Reports Server (NTRS)

    Elchuri, V.

    1985-01-01

    Theoretical aspects of a new capability to determine the vibratory response of turbosystems subjected to aerodynamic excitation are presented. Turbosystems such as advanced turbopropellers with highly swept blades, and axial-flow compressors and turbines can be analyzed using this capability. The capability has been developed and implemented in the April 1984 release of the general purpose finite element program NASTRAN. The dynamic response problem is addressed in terms of the normal modal coordinates of these tuned rotating cyclic structures. Both rigid and flexible hubs/disks are considered. Coriolis and centripetal accelerations, as well as differential stiffness effects are included. Generally non-uniform steady inflow fields and uniform flow fields arbitrarily inclined at small angles with respect to the axis of rotation of the turbosystem are considered sources of aerodynamic excitation. The spatial non-uniformities are considered to be small deviations from a principally uniform inflow. Subsonic and supersonic relative inflows are addressed, with provision for linearly interpolating transonic airloads.

  20. Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions.

    PubMed

    Varshney, Kapil; Chang, Song; Wang, Z Jane

    2013-05-01

    Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card. PMID:23767634

  1. Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions.

    PubMed

    Varshney, Kapil; Chang, Song; Wang, Z Jane

    2013-05-01

    Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card.

  2. Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions

    NASA Astrophysics Data System (ADS)

    Varshney, Kapil; Chang, Song; Wang, Z. Jane

    2013-05-01

    Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card.

  3. Optimal flapping wing for maximum vertical aerodynamic force in hover: twisted or flat?

    PubMed

    Phan, Hoang Vu; Truong, Quang Tri; Au, Thi Kim Loan; Park, Hoon Cheol

    2016-01-01

    This work presents a parametric study, using the unsteady blade element theory, to investigate the role of twist in a hovering flapping wing. For the investigation, a flapping-wing system was developed to create a wing motion of large flapping amplitude. Three-dimensional kinematics of a passively twisted wing, which is capable of creating a linearly variable geometric angle of attack (AoA) along the wingspan, was measured during the flapping motion and used for the analysis. Several negative twist or wash-out configurations with different values of twist angle, which is defined as the difference in the average geometric AoAs at the wing root and the wing tip, were obtained from the measured wing kinematics through linear interpolation and extrapolation. The aerodynamic force generation and aerodynamic power consumption of these twisted wings were obtained and compared with those of flat wings. For the same aerodynamic power consumption, the vertical aerodynamic forces produced by the negatively twisted wings are approximately 10%-20% less than those produced by the flat wings. However, these twisted wings require approximately 1%-6% more power than flat wings to produce the same vertical force. In addition, the maximum-force-producing twisted wing, which was found to be the positive twist or wash-in configuration, was used for comparison with the maximum-force-producing flat wing. The results revealed that the vertical aerodynamic force and aerodynamic power consumption of the two types of wings are almost identical for the hovering condition. The power loading of the positively twisted wing is only approximately 2% higher than that of the maximum-force-producing flat wing. Thus, the flat wing with proper wing kinematics (or wing rotation) can be regarded as a simple and efficient candidate for the development of hovering flapping-wing micro air vehicle. PMID:27387833

  4. Optimal flapping wing for maximum vertical aerodynamic force in hover: twisted or flat?

    PubMed

    Phan, Hoang Vu; Truong, Quang Tri; Au, Thi Kim Loan; Park, Hoon Cheol

    2016-07-08

    This work presents a parametric study, using the unsteady blade element theory, to investigate the role of twist in a hovering flapping wing. For the investigation, a flapping-wing system was developed to create a wing motion of large flapping amplitude. Three-dimensional kinematics of a passively twisted wing, which is capable of creating a linearly variable geometric angle of attack (AoA) along the wingspan, was measured during the flapping motion and used for the analysis. Several negative twist or wash-out configurations with different values of twist angle, which is defined as the difference in the average geometric AoAs at the wing root and the wing tip, were obtained from the measured wing kinematics through linear interpolation and extrapolation. The aerodynamic force generation and aerodynamic power consumption of these twisted wings were obtained and compared with those of flat wings. For the same aerodynamic power consumption, the vertical aerodynamic forces produced by the negatively twisted wings are approximately 10%-20% less than those produced by the flat wings. However, these twisted wings require approximately 1%-6% more power than flat wings to produce the same vertical force. In addition, the maximum-force-producing twisted wing, which was found to be the positive twist or wash-in configuration, was used for comparison with the maximum-force-producing flat wing. The results revealed that the vertical aerodynamic force and aerodynamic power consumption of the two types of wings are almost identical for the hovering condition. The power loading of the positively twisted wing is only approximately 2% higher than that of the maximum-force-producing flat wing. Thus, the flat wing with proper wing kinematics (or wing rotation) can be regarded as a simple and efficient candidate for the development of hovering flapping-wing micro air vehicle.

  5. Analysis of the aerodynamic force in an eye-stabilized flapping flyer.

    PubMed

    Su, Jian-Yuan; Yang, Jing-Tang

    2013-12-01

    Experimental methods and related theories to evaluate the lift force for a flyer are established, but one can traditionally acquire only the magnitude of that lift. We here proffer an analysis based on kinematic theory and experimental visualization of the flow to complete a treatment of the aerodynamic force affecting a hovering flyer that generates a lift force approximately equal to its weight, and remains nearly stationary in midair; the center and direction of the aerodynamic force are accordingly determined with some assumptions made. The principal condition to resolve the problem is the stabilization of the vision of a flyer, which is inspired by a hovering passerine that experiences a substantial upward swing during downstroke periods while its eye remains stabilized. Viewing the aerodynamic force with a bird's eye, we find that the center and direction of this aerodynamic force vary continuously with respect to the lift force. Our results provide practical guidance for engineers to enhance the visual stability of surveillance cameras incorporated in micro aerial vehicles.

  6. Analysis of the aerodynamic force in an eye-stabilized flapping flyer.

    PubMed

    Su, Jian-Yuan; Yang, Jing-Tang

    2013-12-01

    Experimental methods and related theories to evaluate the lift force for a flyer are established, but one can traditionally acquire only the magnitude of that lift. We here proffer an analysis based on kinematic theory and experimental visualization of the flow to complete a treatment of the aerodynamic force affecting a hovering flyer that generates a lift force approximately equal to its weight, and remains nearly stationary in midair; the center and direction of the aerodynamic force are accordingly determined with some assumptions made. The principal condition to resolve the problem is the stabilization of the vision of a flyer, which is inspired by a hovering passerine that experiences a substantial upward swing during downstroke periods while its eye remains stabilized. Viewing the aerodynamic force with a bird's eye, we find that the center and direction of this aerodynamic force vary continuously with respect to the lift force. Our results provide practical guidance for engineers to enhance the visual stability of surveillance cameras incorporated in micro aerial vehicles. PMID:24200672

  7. Transitory Aerodynamic Forces on a Body of Revolution using Synthetic Jet Actuation

    NASA Astrophysics Data System (ADS)

    Rinehart, Christopher; McMichael, James; Glezer, Ari

    2002-11-01

    The aerodynamic forces and moments on axisymmetric bodies at subsonic speeds are controlled by exploiting local flow attachment using fluidic (synthetic jet) actuation and thereby altering the apparent aerodynamic shape of the surface. Control is effected upstream of the base of the body by an azimuthal array of individually-controlled, aft-facing synthetic jets emanating along an azimuthal Coanda surface. Actuation produces asymmetric aerodynamic forces and moments, with ratios of lift to average jet momentum approaching values typical of conventional jet-based circulation control on two-dimensional airfoils. Momentary forces are achieved using transient (pulsed) actuation and are accompanied by the formation and shedding of vorticity concentrations as a precursor to the turning of the outer flow into the wake region.

  8. Direct measurements of controlled aerodynamic forces on a wire-suspended axisymmetric body

    NASA Astrophysics Data System (ADS)

    Abramson, Philip; Vukasinovic, Bojan; Glezer, Ari

    2011-06-01

    A novel in-line miniature force transducer is developed for direct measurements of the net aerodynamic forces and moments on a bluff body. The force transducers are integrated into each of the eight mounting wires that are utilized for suspension of an axisymmetric model in a wind tunnel having minimal wake interference. The aerodynamic forces and moments on the model are altered by induced active local attachment of the separated base flow. Fluidic control is effected by an array of four integrated aft-facing synthetic jet actuators that emanate from narrow, azimuthally segmented slots, equally distributed around the perimeter of the circular tail end. The jet orifices are embedded within a small backward-facing step that extends into a Coanda surface. The altered flow dynamics associated with both quasi-steady and transitory asymmetric activation of the flow control effect is characterized by direct force and PIV measurements.

  9. Aerodynamic forces acting on a rough rotating cylinder in a cross-flow

    NASA Astrophysics Data System (ADS)

    Bychkov, N. M.; Kovalenko, V. M.

    1981-06-01

    The forces are investigated experimentally for two values of the degree of turbulence. The experiments are carried out in a low-turbulence, subsonic wind tunnel; the Reynolds number varies between 100,000 and 600,000, and the rotation parameter, between 0 and 1 radian. The apparatus permits the registration of instantaneous forces with relatively high precision. The desired roughness is produced by covering the surface of the cylinder with emery paper. The magnitude and type of changes in the aerodynamic forces for the case of a rough cylinder are found to differ in a fundamental way from that of a smooth cylinder, a difference related to features of the flow near the wall and to the position of the separation points of the boundary layer. Increasing the degree of turbulence of the flow does not noticeably affect the aerodynamic forces of a rough cylinder in the supercritical region of Reynolds numbers.

  10. Maximum Aerodynamic Force on an Ascending Space Vehicle

    NASA Astrophysics Data System (ADS)

    Backman, Philip

    2012-03-01

    The March 2010 issue of The Physics Teacher includes a great article by Metz and Stinner on the kinematics and dynamics of a space shuttle launch. Within those pages is a brief mention of an event known in the language of the National Aeronautics and Space Administration (NASA) as "maximum dynamic pressure" (called simply "Max.AirPressure" in the article), where the combined effect of air density and the shuttles speed produce the greatest aerodynamic stress on the vehicle as it ascends through the atmosphere toward orbit. Official commentary during a launch2 refers to this point in the ascent with language such as "space shuttle main engines throttling back as vehicle enters area of maximum dynamic pressure" and occurs in a range between 45 and 60 s after launch. (In dealing with this stress, the space shuttles main engines reduce their thrust at approximately 45 s to reduce acceleration, and return to normal levels again some 15 s later as maximum dynamic pressure is traversed.) This paper presents an analysis, accessible to introductory-level students, that predicts the time of Max. AirPressure for a given ascending spacecraft.

  11. Semiempirical method for prediction of aerodynamic forces and moments on a steadily spinning light airplane

    NASA Technical Reports Server (NTRS)

    Pamadi, Bandu N.; Taylor, Lawrence W., Jr.

    1987-01-01

    A semi-empirical method is presented for the estimation of aerodynamic forces and moments acting on a steadily spinning (rotating) light airplane. The airplane is divided into wing, body, and tail surfaces. The effect of power is ignored. The strip theory is employed for each component of the spinning airplane to determine its contribution to the total aerodynamic coefficients. Then, increments to some of the coefficients which account for centrifugal effect are estimated. The results are compared to spin tunnel rotary balance test data.

  12. Dynamic control of aerodynamic forces on a moving platform using active flow control

    NASA Astrophysics Data System (ADS)

    Brzozowski, Daniel P.

    The unsteady interaction between trailing edge aerodynamic flow control and airfoil motion in pitch and plunge is investigated in wind tunnel experiments using a two degree-of-freedom traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the trailing edge of the airfoil using hybrid synthetic jet actuators. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and particle image velocimetry (PIV) measurements that are taken phase-locked to the commanded actuation waveform. The effect of the unsteady motion on the model-embedded flow control is assessed in both trajectory tracking and disturbance rejection maneuvers. The time-varying aerodynamic lift and pitching moment are estimated from a PIV wake survey using a reduced order model based on classical unsteady aerodynamic theory. These measurements suggest that the entire flow over the airfoil readjusts within 2--3 convective time scales, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.

  13. Aerodynamic force measurement on a large-scale model in a short duration test facility

    SciTech Connect

    Tanno, H.; Kodera, M.; Komuro, T.; Sato, K.; Takahasi, M.; Itoh, K.

    2005-03-01

    A force measurement technique has been developed for large-scale aerodynamic models with a short test time. The technique is based on direct acceleration measurements, with miniature accelerometers mounted on a test model suspended by wires. Measuring acceleration at two different locations, the technique can eliminate oscillations from natural vibration of the model. The technique was used for drag force measurements on a 3 m long supersonic combustor model in the HIEST free-piston driven shock tunnel. A time resolution of 350 {mu}s is guaranteed during measurements, whose resolution is enough for ms order test time in HIEST. To evaluate measurement reliability and accuracy, measured values were compared with results from a three-dimensional Navier-Stokes numerical simulation. The difference between measured values and numerical simulation values was less than 5%. We conclude that this measurement technique is sufficiently reliable for measuring aerodynamic force within test durations of 1 ms.

  14. The Transient Aerodynamic Forces Effected by Trailing Edge Active Flow Control

    NASA Astrophysics Data System (ADS)

    Brzozowski, Dan; Culp, John; Glezer, Ari

    2012-11-01

    The transient aerodynamic forces effected by trailing edge flow control are investigated in wind tunnel experiments using a 2-DOF traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the surface using hybrid synthetic jet actuators. The time-histories of surface pressure and aerodynamic lift and pitching moment immediately following the application of flow control are measured using simultaneous pressure, force and velocity measurements that are taken phase-locked to the commanded actuation waveform. Circulation time history that is estimated from a PIV wake survey shows that the entire flow over the airfoil readjusts within about 1 . 5TCONV , which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.

  15. Successive smoothing algorithm for constructing the semiempirical model developed at ONERA to predict unsteady aerodynamic forces. [aeroelasticity in helicopters

    NASA Technical Reports Server (NTRS)

    Petot, D.; Loiseau, H.

    1982-01-01

    Unsteady aerodynamic methods adopted for the study of aeroelasticity in helicopters are considered with focus on the development of a semiempirical model of unsteady aerodynamic forces acting on an oscillating profile at high incidence. The successive smoothing algorithm described leads to the model's coefficients in a very satisfactory manner.

  16. Estimating unsteady aerodynamic forces on a cascade in a three-dimensional turbulence field

    NASA Technical Reports Server (NTRS)

    Norman, T.; Johnson, W.

    1985-01-01

    An analytical method has been developed to estimate the unsteady aerodynamic forces caused by flow field turbulence on a wind tunnel turning vane cascade system (vane set). This method approximates dynamic lift and drag by linearly perturbing the appropriate steady state force equations, assuming that the dynamic loads are due only to free stream turbulence and that this turbulence is homogeneous, isotropic, and Gaussian. Correlation and unsteady aerodynamic effects are also incorporated into the analytical model. Using these assumptions, equations relating dynamic lift and drag to flow turbulence, mean velocity, and vane set geometry are derived. From these equations, estimates for the power spectra and rms (root mean squared value, delta) loading of both lift and drag can be determined.

  17. Estimating unsteady aerodynamic forces on a cascade in a three-dimensional turbulence field

    NASA Technical Reports Server (NTRS)

    Norman, T. R.; Johnson, W.

    1986-01-01

    An analytical method has been developed to estimate tne unsteady aerodynamic forces caused by flow field turbulence on a wind tunnel turning vane cascade system (vane set). This method approximates dynamic lift and drag by linearly perturbing the appropriate steady state force equations, assuming that the dynamic loads are due only to free stream turbulence and that this turbulence is homogeneous, isotropic, and Gaussian. Correlation and unsteady aerodynamic effects are also incorporated into the analytical model. Using these assumptions, equations relating dynamic lift and drag to flow turbulence, mean velocity, and vane set geometry are derived. From these equations, estimates for the power spectra and rms (root mean squared value, delta) loading of both lift and drag can be determined.

  18. Structural effects of unsteady aerodynamic forces on horizontal-axis wind turbines

    SciTech Connect

    Miller, M.S.; Shipley, D.E.

    1994-08-01

    Due to its renewable nature and abundant resources, wind energy has the potential to fulfill a large portion of this nation`s energy needs. The simplest means of utilizing wind energy is through the use of downwind, horizontal-axis wind turbines (HAWT) with fixed-pitch rotors. This configuration regulates the peak power by allowing the rotor blade to aerodynamically stall. The stall point, the point of maximum coefficient of lift, is currently predicted using data obtained from wind tunnel tests. Unfortunately, these tests do not accurately simulate conditions encountered in the field. Flow around the tower and nacelle coupled with inflow turbulence and rotation of the turbine blades create unpredicted aerodynamic forces. Dynamic stall is hypothesized to occur. Such aerodynamic loads are transmitted into the rotor and tower causing structural resonance that drastically reduces the design lifetime of the wind turbine. The current method of alleviating this problem is to structurally reinforce the tower and blades. However, this adds unneeded mass and, therefore, cost to the turbines. A better understanding of the aerodynamic forces and the manner in which they affect the structure would allow for the design of more cost effective and durable wind turbines. Data compiled by the National Renewable Energy Laboratory (NREL) for a downwind HAWT with constant chord, untwisted, fixed-pitch rotors is analyzed. From these data, the actual aerodynamic characteristics of the rotor are being portrayed and the potential effects upon the structure can for the first time be fully analyzed. Based upon their understanding, solutions to the problem of structural resonance are emerging.

  19. Structural effects of unsteady aerodynamic forces on horizontal-axis wind turbines

    NASA Astrophysics Data System (ADS)

    Miller, M. S.; Shipley, D. E.

    1994-08-01

    Due to its renewable nature and abundant resources, wind energy has the potential to fulfill a large portion of this nation's energy needs. The simplest means of utilizing wind energy is through the use of downwind, horizontal-axis wind turbines (HAWT) with fixed-pitch rotors. This configuration regulates the peak power by allowing the rotor blade to aerodynamically stall. The stall point, the point of maximum coefficient of lift, is currently predicted using data obtained from wind tunnel tests. Unfortunately, these tests do not accurately simulate conditions encountered in the field. Flow around the tower and nacelle coupled with inflow turbulence and rotation of the turbine blades create unpredicted aerodynamic forces. Dynamic stall is hypothesized to occur. Such aerodynamic loads are transmitted into the rotor and tower causing structural resonance that drastically reduces the design lifetime of the wind turbine. The current method of alleviating this problem is to structurally reinforce the tower and blades. However, this adds unneeded mass and, therefore, cost to the turbines. A better understanding of the aerodynamic forces and the manner in which they affect the structure would allow for the design of more cost effective and durable wind turbines. Data compiled by the National Renewable Energy Laboratory (NREL) for a downwind HAWT with constant chord, untwisted, fixed-pitch rotors is analyzed. From these data, the actual aerodynamic characteristics of the rotor are being portrayed and the potential effects upon the structure can for the first time be fully analyzed. Based upon their understanding, solutions to the problem of structural resonance are emerging.

  20. A computational study of the aerodynamic forces and power requirements of dragonfly (Aeschna juncea) hovering.

    PubMed

    Sun, Mao; Lan, Shi Long

    2004-05-01

    Aerodynamic force generation and mechanical power requirements of a dragonfly (Aeschna juncea) in hovering flight are studied. The method of numerically solving the Navier-Stokes equations in moving overset grids is used. When the midstroke angles of attack in the downstroke and the upstroke are set to 52 degrees and 8 degrees, respectively (these values are close to those observed), the mean vertical force equals the insect weight, and the mean thrust is approximately zero. There are two large vertical force peaks in one flapping cycle. One is in the first half of the cycle, which is mainly due to the hindwings in their downstroke; the other is in the second half of the cycle, which is mainly due to the forewings in their downstroke. Hovering with a large stroke plane angle (52 degrees ), the dragonfly uses drag as a major source for its weight-supporting force (approximately 65% of the total vertical force is contributed by the drag and 35% by the lift of the wings). The vertical force coefficient of a wing is twice as large as the quasi-steady value. The interaction between the fore- and hindwings is not very strong and is detrimental to the vertical force generation. Compared with the case of a single wing in the same motion, the interaction effect reduces the vertical forces on the fore- and hindwings by 14% and 16%, respectively, of that of the corresponding single wing. The large vertical force is due to the unsteady flow effects. The mechanism of the unsteady force is that in each downstroke of the hindwing or the forewing, a new vortex ring containing downward momentum is generated, giving an upward force. The body-mass-specific power is 37 W kg(-1), which is mainly contributed by the aerodynamic power.

  1. Dynamical systems analysis of electrostatic and aerodynamic forced vibrations of a thin flexible electrode

    NASA Astrophysics Data System (ADS)

    Madanu, Sushma Bala

    Transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow is studied using both experiments and numerical modeling. In the experiments the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. The maximum voltage applied varies from 1 - 9 kV and air flow speeds range from 0.224 - 3.58 m/s (0.5 - 8 mile/hr). The Reynolds numbers for these speeds lie in the range of 1000 - 20000. A range of control parameters leading to stable vibrations are established using the Strouhal number as the operating parameter whose inverse values change from 100 - 2500. The Numerical results are validated with experimental results. Assuming the amplitude of vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the vibrations of the dynamical system. Aerodynamic forcing is modeled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to square of air flow velocity by obtaining relationship between the experimental amplitude of vibrations and air flow velocity. Numerical results strongly agree with those of experiments predicting accurate vibration amplitudes, displacement frequency and quasi-periodic displacements of the cantilever tip.

  2. Electrostatic and aerodynamic forced vibrations of a thin flexible electrode: Quasi-periodic vs. chaotic oscillations.

    PubMed

    Madanu, Sushma B; Barbel, Stanley I; Ward, Thomas

    2016-06-01

    In this paper, transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow are studied using both experiments and numerical modeling. In the experiments, the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. A range of control parameters leading to stable vibrations are established using a dimensionless operating parameter that is the ratio of the induced and the free stream velocities. Numerical results are validated with experimental data. Assuming the amplitude of vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the equation of motion. Aerodynamic forcing is modelled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to the square of the air flow velocity. Numerical results strongly agree with the experiments predicting accurate vibration amplitude, displacement frequency, and quasi-periodic displacement of the cantilever tip. PMID:27368778

  3. Electrostatic and aerodynamic forced vibrations of a thin flexible electrode: Quasi-periodic vs. chaotic oscillations.

    PubMed

    Madanu, Sushma B; Barbel, Stanley I; Ward, Thomas

    2016-06-01

    In this paper, transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow are studied using both experiments and numerical modeling. In the experiments, the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. A range of control parameters leading to stable vibrations are established using a dimensionless operating parameter that is the ratio of the induced and the free stream velocities. Numerical results are validated with experimental data. Assuming the amplitude of vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the equation of motion. Aerodynamic forcing is modelled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to the square of the air flow velocity. Numerical results strongly agree with the experiments predicting accurate vibration amplitude, displacement frequency, and quasi-periodic displacement of the cantilever tip.

  4. Electrostatic and aerodynamic forced vibrations of a thin flexible electrode: Quasi-periodic vs. chaotic oscillations

    NASA Astrophysics Data System (ADS)

    Madanu, Sushma B.; Barbel, Stanley I.; Ward, Thomas

    2016-06-01

    In this paper, transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow are studied using both experiments and numerical modeling. In the experiments, the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. A range of control parameters leading to stable vibrations are established using a dimensionless operating parameter that is the ratio of the induced and the free stream velocities. Numerical results are validated with experimental data. Assuming the amplitude of vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the equation of motion. Aerodynamic forcing is modelled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to the square of the air flow velocity. Numerical results strongly agree with the experiments predicting accurate vibration amplitude, displacement frequency, and quasi-periodic displacement of the cantilever tip.

  5. MIST - MINIMUM-STATE METHOD FOR RATIONAL APPROXIMATION OF UNSTEADY AERODYNAMIC FORCE COEFFICIENT MATRICES

    NASA Technical Reports Server (NTRS)

    Karpel, M.

    1994-01-01

    Various control analysis, design, and simulation techniques of aeroservoelastic systems require the equations of motion to be cast in a linear, time-invariant state-space form. In order to account for unsteady aerodynamics, rational function approximations must be obtained to represent them in the first order equations of the state-space formulation. A computer program, MIST, has been developed which determines minimum-state approximations of the coefficient matrices of the unsteady aerodynamic forces. The Minimum-State Method facilitates the design of lower-order control systems, analysis of control system performance, and near real-time simulation of aeroservoelastic phenomena such as the outboard-wing acceleration response to gust velocity. Engineers using this program will be able to calculate minimum-state rational approximations of the generalized unsteady aerodynamic forces. Using the Minimum-State formulation of the state-space equations, they will be able to obtain state-space models with good open-loop characteristics while reducing the number of aerodynamic equations by an order of magnitude more than traditional approaches. These low-order state-space mathematical models are good for design and simulation of aeroservoelastic systems. The computer program, MIST, accepts tabular values of the generalized aerodynamic forces over a set of reduced frequencies. It then determines approximations to these tabular data in the LaPlace domain using rational functions. MIST provides the capability to select the denominator coefficients in the rational approximations, to selectably constrain the approximations without increasing the problem size, and to determine and emphasize critical frequency ranges in determining the approximations. MIST has been written to allow two types data weighting options. The first weighting is a traditional normalization of the aerodynamic data to the maximum unit value of each aerodynamic coefficient. The second allows weighting the

  6. The aerodynamic forces and pressure distribution of a revolving pigeon wing

    PubMed Central

    Usherwood, James R.

    2012-01-01

    The aerodynamic forces acting on a revolving dried pigeon wing and a flat card replica were measured with a propeller rig, effectively simulating a wing in continual downstroke. Two methods were adopted: direct measurement of the reaction vertical force and torque via a forceplate, and a map of the pressures along and across the wing measured with differential pressure sensors. Wings were tested at Reynolds numbers up to 108,000, typical for slow-flying pigeons, and considerably above previous similar measurements applied to insect and hummingbird wing and wing models. The pigeon wing out-performed the flat card replica, reaching lift coefficients of 1.64 compared with 1.44. Both real and model wings achieved much higher maximum lift coefficients, and at much higher geometric angles of attack (43°), than would be expected from wings tested in a windtunnel simulating translating flight. It therefore appears that some high-lift mechanisms, possibly analogous to those of slow-flying insects, may be available for birds flapping with wings at high angles of attack. The net magnitude and orientation of aerodynamic forces acting on a revolving pigeon wing can be determined from the differential pressure maps with a moderate degree of precision. With increasing angle of attack, variability in the pressure signals suddenly increases at an angle of attack between 33° and 38°, close to the angle of highest vertical force coefficient or lift coefficient; stall appears to be delayed compared with measurements from wings in windtunnels. PMID:22736891

  7. The aerodynamic forces and pressure distribution of a revolving pigeon wing

    NASA Astrophysics Data System (ADS)

    Usherwood, James R.

    The aerodynamic forces acting on a revolving dried pigeon wing and a flat card replica were measured with a propeller rig, effectively simulating a wing in continual downstroke. Two methods were adopted: direct measurement of the reaction vertical force and torque via a forceplate, and a map of the pressures along and across the wing measured with differential pressure sensors. Wings were tested at Reynolds numbers up to 108,000, typical for slow-flying pigeons, and considerably above previous similar measurements applied to insect and hummingbird wing and wing models. The pigeon wing out-performed the flat card replica, reaching lift coefficients of 1.64 compared with 1.44. Both real and model wings achieved much higher maximum lift coefficients, and at much higher geometric angles of attack (43°), than would be expected from wings tested in a windtunnel simulating translating flight. It therefore appears that some high-lift mechanisms, possibly analogous to those of slow-flying insects, may be available for birds flapping with wings at high angles of attack. The net magnitude and orientation of aerodynamic forces acting on a revolving pigeon wing can be determined from the differential pressure maps with a moderate degree of precision. With increasing angle of attack, variability in the pressure signals suddenly increases at an angle of attack between 33° and 38°, close to the angle of highest vertical force coefficient or lift coefficient; stall appears to be delayed compared with measurements from wings in windtunnels.

  8. The aerodynamic forces and pressure distribution of a revolving pigeon wing

    NASA Astrophysics Data System (ADS)

    Usherwood, James R.

    2009-05-01

    The aerodynamic forces acting on a revolving dried pigeon wing and a flat card replica were measured with a propeller rig, effectively simulating a wing in continual downstroke. Two methods were adopted: direct measurement of the reaction vertical force and torque via a forceplate, and a map of the pressures along and across the wing measured with differential pressure sensors. Wings were tested at Reynolds numbers up to 108,000, typical for slow-flying pigeons, and considerably above previous similar measurements applied to insect and hummingbird wing and wing models. The pigeon wing out-performed the flat card replica, reaching lift coefficients of 1.64 compared with 1.44. Both real and model wings achieved much higher maximum lift coefficients, and at much higher geometric angles of attack (43°), than would be expected from wings tested in a windtunnel simulating translating flight. It therefore appears that some high-lift mechanisms, possibly analogous to those of slow-flying insects, may be available for birds flapping with wings at high angles of attack. The net magnitude and orientation of aerodynamic forces acting on a revolving pigeon wing can be determined from the differential pressure maps with a moderate degree of precision. With increasing angle of attack, variability in the pressure signals suddenly increases at an angle of attack between 33° and 38°, close to the angle of highest vertical force coefficient or lift coefficient; stall appears to be delayed compared with measurements from wings in windtunnels.

  9. Analysis of Dynamic Stability of Space Launch Vehicles under Aerodynamic Forces Using CFD Derived Data

    NASA Astrophysics Data System (ADS)

    Trikha, M.; Gopalakrishnan, S.; Mahapatra, D. Roy

    2011-09-01

    A computational framework is developed to investigate the dynamic stability of space launch vehicles subjected to aerodynamic forces. A detailed mechanics based mathematical model of a moving flexible vehicle is used. The aerodynamic forces on the vehicle are obtained from simulation using Computational Fluid Dynamics (CFD) package. The objective behind this investigation is to analyze the problem of aeroelastic instability in blunt/conical nose slender space launch vehicles. Coupling among the rigid-body modes, the longitudinal vibration modes, and the transverse vibrational modes are considered. The effect of propulsive thrust as a follower force is also considered. A one-dimensional finite element model is developed to investigate the occurrence of aeroelastic instabilities of various types. Eigenvalues of the vehicle are determined in order to analyze the stable regimes. As a special case, we show numerical simulations by considering a typical vehicle configuration, for a vehicle Mach number of 0.8. Phenomenon of flutter is observed at this Mach number. The proposed analysis is suitable for different launch events such as vehicle take-off, maximum dynamic pressure regime, thrust transients, stage separation etc. The approach developed in this paper can be utilized for preliminary design of launch vehicles and establishing the stability boundaries for different trajectory parameters.

  10. Investigation on the forced response of a radial turbine under aerodynamic excitations

    NASA Astrophysics Data System (ADS)

    Ma, Chaochen; Huang, Zhi; Qi, Mingxu

    2016-04-01

    Rotor blades in a radial turbine with nozzle guide vanes typically experience harmonic aerodynamic excitations due to the rotor stator interaction. Dynamic stresses induced by the harmonic excitations can result in high cycle fatigue (HCF) of the blades. A reliable prediction method for forced response issue is essential to avoid the HCF problem. In this work, the forced response mechanisms were investigated based on a fluid structure interaction (FSI) method. Aerodynamic excitations were obtained by three-dimensional unsteady computational fluid dynamics (CFD) simulation with phase shifted periodic boundary conditions. The first two harmonic pressures were determined as the primary components of the excitation and applied to finite element (FE) model to conduct the computational structural dynamics (CSD) simulation. The computed results from the harmonic forced response analysis show good agreement with the predictions of Singh's advanced frequency evaluation (SAFE) diagram. Moreover, the mode superposition method used in FE simulation offers an efficient way to provide quantitative assessments of mode response levels and resonant strength.

  11. An integrated CFD/experimental analysis of aerodynamic forces and moments

    NASA Technical Reports Server (NTRS)

    Melton, John E.; Robertson, David D.; Moyer, Seth A.

    1989-01-01

    Aerodynamic analysis using computational fluid dynamics (CFD) is most fruitful when it is combined with a thorough program of wind tunnel testing. The understanding of aerodynamic phenomena is enhanced by the synergistic use of both analysis methods. A technique is described for an integrated approach to determining the forces and moments acting on a wind tunnel model by using a combination of experimentally measured pressures and CFD predictions. The CFD code used was FLO57 (an Euler solver) and the wind tunnel model was a heavily instrumented delta wing with 62.5 deg of leading-edge sweep. A thorough comparison of the CFD results and the experimental data is presented for surface pressure distributions and longitudinal forces and moments. The experimental pressures were also integrated over the surface of the model and the resulting forces and moments are compared to the CFD and wind tunnel results. The accurate determination of various drag increments via the combined use of the CFD and experimental pressures is presented in detail.

  12. Aerodynamic design of a Coanda induced force and thruster anti-torque system

    NASA Technical Reports Server (NTRS)

    Velkoff, Henry R.; Tung, Chee

    1991-01-01

    A general method of analysis of the external and internal aerodynamics of a generic Coanda induced circulation anti-torque system is presented. The technique gives moment about the yaw axis and download induced on the boom as well as the force developed by an aft jet. The external flows including downwash, wake swirl and the boom circulation are considered. The internal flow and losses through the duct, fan, blown slots, cascades and nozzle are considered on a step-by-step basis. Limited comparison is made with open data where available.

  13. Analysis of preflutter and postflutter characteristics with motion-matched aerodynamic forces

    NASA Technical Reports Server (NTRS)

    Cunningham, H. J.

    1978-01-01

    The development of the equations of dynamic equilibrium for a lifting surface from Lagrange's equation is reviewed and restated for general exponential growing and decaying oscillatory motion. Aerodynamic forces for this motion are obtained from the three-dimensional supersonic kernel function that is newly generalized to complex reduced frequencies. Illustrative calculations were made for two flutter models at supersonic Mach numbers. Preflutter and postflutter motion isodecrement curves were obtained. This type of analysis can be used to predict preflutter behavior during flutter testing and to predict postflutter behavior for use in the design of flutter suppression systems.

  14. Potential impacts of advanced aerodynamic technology on air transportation system productivity

    NASA Technical Reports Server (NTRS)

    Bushnell, Dennis M. (Editor)

    1994-01-01

    Summaries of a workshop held at NASA Langley Research Center in 1993 to explore the application of advanced aerodynamics to airport productivity improvement are discussed. Sessions included discussions of terminal area productivity problems and advanced aerodynamic technologies for enhanced high lift and reduced noise, emissions, and wake vortex hazard with emphasis upon advanced aircraft configurations and multidisciplinary solution options.

  15. Simultaneous measurement of aerodynamic forces and kinematics in flapping wings of tethered locust.

    PubMed

    Shkarayev, Sergey; Kumar, Rajeev

    2015-12-01

    Aerodynamic and inertial forces and corresponding kinematics of flapping wings of locusts, Schistocerca americana, were investigated in a low-speed wind tunnel. The experimental setup included live locusts mounted on microbalance synchronized with a high-speed video system. Simultaneous measurements of wing kinematics and forces were carried out on three locusts at 7° angle of attack and velocities of 0 m s(-1) and 4 m s(-1). Time variations of flapping and pitching angles exhibit similar patterns in fore- and hindwings and among the animals. Significant tip to root variations in pitching angle are found in both wings. The locusts have much larger flapping and pitching amplitudes in still air causing larger oscillations in inertial forces. Inertial forces are added to the lift and thrust on one part of the stroke, resulting in higher reaction forces and subtracted on the other part. Plots of the lift demonstrate similar trends with and without the wind. The global maxima and peak-to-peak amplitudes in lift are about the same in both tests. However, local minima are significantly lower in still air, resulting in much smaller stroke-averaged lift. Amplitudes of thrust force oscillations are much higher in still air; consequently, the stroke-averaged thrust is higher compared to the non-zero freestream velocity case. PMID:26496206

  16. Simultaneous measurement of aerodynamic forces and kinematics in flapping wings of tethered locust.

    PubMed

    Shkarayev, Sergey; Kumar, Rajeev

    2015-10-23

    Aerodynamic and inertial forces and corresponding kinematics of flapping wings of locusts, Schistocerca americana, were investigated in a low-speed wind tunnel. The experimental setup included live locusts mounted on microbalance synchronized with a high-speed video system. Simultaneous measurements of wing kinematics and forces were carried out on three locusts at 7° angle of attack and velocities of 0 m s(-1) and 4 m s(-1). Time variations of flapping and pitching angles exhibit similar patterns in fore- and hindwings and among the animals. Significant tip to root variations in pitching angle are found in both wings. The locusts have much larger flapping and pitching amplitudes in still air causing larger oscillations in inertial forces. Inertial forces are added to the lift and thrust on one part of the stroke, resulting in higher reaction forces and subtracted on the other part. Plots of the lift demonstrate similar trends with and without the wind. The global maxima and peak-to-peak amplitudes in lift are about the same in both tests. However, local minima are significantly lower in still air, resulting in much smaller stroke-averaged lift. Amplitudes of thrust force oscillations are much higher in still air; consequently, the stroke-averaged thrust is higher compared to the non-zero freestream velocity case.

  17. Analysis of Dragonfly Take-off Mechanism: Initial Impulse Generated by Aerodynamic Forces

    NASA Astrophysics Data System (ADS)

    Zhu, Ruijie; Bode-Oke, Ayodeji; Ren, Yan; Dong, Haibo; Flow Simulation Research Team

    2013-11-01

    Take-off is a critical part of insect flight due to not only that every single flight initiates from take-off, but also that the take-off period, despite its short duration, accounts for a relatively large fraction of the total energy consumption. Thus, studying the mechanism of insect take-off will help to improve the design of Micro Air Vehicles (MAVs) in two major properties, the success rate and the energy efficiency of take-off. In this work, we study 20 cases in which dragonflies (species including Pachydiplax longipennis, Epitheca Cynosura, Epitheca princeps etc.) take off from designed platform. By high-speed photogrammetry, 3-d reconstruction and numerical simulation, we explore how dragonflies coordinate different body parts to help take-off. We evaluate how aerodynamic forces generated by wing flapping create the initial impulse, and how these forces help save energy consumption. Supported by NSF CBET-1343154.

  18. Nonlinear programming extensions to rational function approximation methods for unsteady aerodynamic forces

    NASA Technical Reports Server (NTRS)

    Tiffany, Sherwood H.; Adams, William M., Jr.

    1988-01-01

    The approximation of unsteady generalized aerodynamic forces in the equations of motion of a flexible aircraft are discussed. Two methods of formulating these approximations are extended to include the same flexibility in constraining the approximations and the same methodology in optimizing nonlinear parameters as another currently used extended least-squares method. Optimal selection of nonlinear parameters is made in each of the three methods by use of the same nonlinear, nongradient optimizer. The objective of the nonlinear optimization is to obtain rational approximations to the unsteady aerodynamics whose state-space realization is lower order than that required when no optimization of the nonlinear terms is performed. The free linear parameters are determined using the least-squares matrix techniques of a Lagrange multiplier formulation of an objective function which incorporates selected linear equality constraints. State-space mathematical models resulting from different approaches are described and results are presented that show comparative evaluations from application of each of the extended methods to a numerical example.

  19. Theoretical and Experimental studies of aerodynamic interference effects. [aerodynamic forces on winglets and on wing nacelle configurations for the YC-14 and KC-135 aircraft

    NASA Technical Reports Server (NTRS)

    Rettie, I. H.

    1980-01-01

    Theoretical studies of aerodynamic forces on winglets shed considerable light on the mechanism by which these devices can reduce drag at constant total lift and on the necessity for proper alignment and cambering to achieve optimum favorable interference. Results of engineering studies, wind tunnel tests and performance predictions are reviewed for installations proposed for the AMST YC-14 and the KC-135 airplanes. The other major area of aerodynamic interference discussed is that of engine nacelle installations. Slipper and overwing nacelles have received much attention because of their potential for noise reduction, propulsive lift and improved ground clearance. A major challenge is the integration of such nacelles with the supercritical flow on the upper surface of a swept wing in cruise at high subsonic speeds.

  20. Force production of a hovering hummingbird

    NASA Astrophysics Data System (ADS)

    Luo, Haoxiang; Song, Jialei; Hedrick, Tyson

    2013-11-01

    A three-dimensional numerical study is performed for a hovering Ruby-throated hummingbird (Archilochus colubris) based on an immersed-boundary method. To accurately model the unsteady aerodynamics, realistic 3D wing kinematics is reconstructed from high-speed images of the wing motion filmed at 1000 frames per second, resulting in 25 frames per flapping cycle. A high-resolution grid is employed to resolve the vortices shed from the wing. The results are validated by comparing the spanwise vorticity and circulation with the previous PIV data and also by calculating the average lift. The force production shows significant asymmetry with the downstroke producing lift 2.6 times as high as the upstroke, despite a nearly horizontal stroke plane. The total power consumption is around 55 W/kg, which is twice of previous estimate. In this presentation, we will discuss several mechanisms that lead to the force asymmetry, including the drag-based lift and the leading-edge vortex behavior. We will also address the role of wing-wake interaction, which appears to be different for the hummingbird than some of the insects such as fruit flies. Supported by NSF (No. CBET-0954381).

  1. Transient aerodynamic forces on a fighter model during simulated approach and landing with thrust reversers

    NASA Technical Reports Server (NTRS)

    Humphreys, A. P.; Paulson, J. W., Jr.; Kemmerly, G. T.

    1988-01-01

    Previous wind tunnel tests of fighter configurations have shown that thrust reverser jets can induce large, unsteady aerodynamic forces and moments during operation in ground proximity. This is a concern for STOL configurations using partial reversing to spoil the thrust while keeping the engine output near military (MIL) power during landing approach. A novel test technique to simulate approach and landing was developed under a cooperative Northrop/NASA/USAF program. The NASA LaRC Vortex Research Facility was used for the experiments in which a 7-percent F-18 model was moved horizontally at speeds of up to 100 feet per second over a ramp simulating an aircraft to ground rate of closure similar to a no-flare STOL approach and landing. This paper presents an analysis of data showing the effect of reverser jet orientation and jet dynamic pressure ratio on the transient forces for different angles of attack, and flap and horizontal tail deflection. It was found, for reverser jets acting parallel to the plane of symmetry, that the jets interacted strongly with the ground, starting approximately half a span above the ground board. Unsteady rolling moment transients, large enough to cause the probable upset of an aircraft, and strong normal force and pitching moment transients were measured. For jets directed 40 degrees outboard, the transients were similar to the jet-off case, implying only minor interaction.

  2. Aerodynamic levitator for large-sized glassy material production.

    PubMed

    Yoda, Shinichi; Cho, Won-Seung; Imai, Ryoji

    2015-09-01

    Containerless aerodynamic levitation processing is a unique technology for the fabrication of bulk non-crystalline materials. Using conventional aerodynamic levitation, a high reflective index (RI) material (BaTi2O5 and LaO3/2-TiO2-ZrO2 system) was developed with a RI greater than approximately 2.2, which is similar to that of diamond. However, the glass size was small, approximately 3 mm in diameter. Therefore, it is essential to produce large sized materials for future optical materials applications, such as camera lenses. In this study, a new aerodynamic levitator was designed to produce non-crystalline materials with diameters larger than 6 mm. The concept of this new levitator was to set up a reduced pressure at the top of the molten samples without generating turbulent flow. A numerical simulation was also performed to verify the concept. PMID:26429456

  3. Aerodynamic levitator for large-sized glassy material production.

    PubMed

    Yoda, Shinichi; Cho, Won-Seung; Imai, Ryoji

    2015-09-01

    Containerless aerodynamic levitation processing is a unique technology for the fabrication of bulk non-crystalline materials. Using conventional aerodynamic levitation, a high reflective index (RI) material (BaTi2O5 and LaO3/2-TiO2-ZrO2 system) was developed with a RI greater than approximately 2.2, which is similar to that of diamond. However, the glass size was small, approximately 3 mm in diameter. Therefore, it is essential to produce large sized materials for future optical materials applications, such as camera lenses. In this study, a new aerodynamic levitator was designed to produce non-crystalline materials with diameters larger than 6 mm. The concept of this new levitator was to set up a reduced pressure at the top of the molten samples without generating turbulent flow. A numerical simulation was also performed to verify the concept.

  4. Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps).

    PubMed

    Bishop, Kristin L

    2007-08-01

    Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a

  5. Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps).

    PubMed

    Bishop, Kristin L

    2007-08-01

    Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a

  6. Behavior of precipitating water drops under the influence of electrical and aerodynamical forces

    NASA Astrophysics Data System (ADS)

    Coquillat, Sylvain; Chauzy, Serge

    1993-06-01

    The present work performs a realistic modeling of precipitating charged water drops under the influence of electrical and dynamical forces in the vertical and downward electric field of a thundercloud. The following factors which control the shape of an individual raindrop are taken into account: surface tension, internal hydrostatic pressure, aerodynamic pressure, and electrostatic pressure. Unlike a recent and notable work by Chuang and Beard (1990) in which this problem is approached by adjusting an empirical pressure distribution for the distortion, our model considers simple local pressure balance to determine the drop shape. This computation aims at characterizing drop distortion, falling speed modification, and disruption. The overall present results are similar to those of Chuang and Beard's more sophisticated model, and the predicted critical fields are even closer to wind tunnel measurements by Richards and Dawson (1971). The disruption of positively charged drops requires lower ambient fields than that of the negatively charged drops, and for highly charged and large drops they are of the order of those commonly measured within thunderclouds. At last, the terminal velocity is highly affected by net charge and ambient field. These processes are probably important in lightning initiation during drop disruption.

  7. Countermeasures for Reducing Unsteady Aerodynamic Force Acting on High-Speed Train in Tunnel by Use of Modifications of Train Shapes

    NASA Astrophysics Data System (ADS)

    Suzuki, Masahiro; Nakade, Koji; Ido, Atsushi

    As the maximum speed of high-speed trains increases, flow-induced vibration of trains in tunnels has become a subject of discussion in Japan. In this paper, we report the result of a study on use of modifications of train shapes as a countermeasure for reducing an unsteady aerodynamic force by on-track tests and a wind tunnel test. First, we conduct a statistical analysis of on-track test data to identify exterior parts of a train which cause the unsteady aerodynamic force. Next, we carry out a wind tunnel test to measure the unsteady aerodynamic force acting on a train in a tunnel and examined train shapes with a particular emphasis on the exterior parts identified by the statistical analysis. The wind tunnel test shows that fins under the car body are effective in reducing the unsteady aerodynamic force. Finally, we test the fins by an on-track test and confirmed its effectiveness.

  8. Computer subroutine for estimating aerodynamic blade loads on Darrieus vertical axis wind turbines. [FORCE code

    SciTech Connect

    Sullivan, W. N.; Leonard, T. M.

    1980-11-01

    An important aspect of structural design of the Darrieus rotor is the determination of aerodynamic blade loads. This report describes a load generator which has been used at Sandia for quasi-static and dynamic rotor analyses. The generator is based on the single streamtube aerodynamic flow model and is constructed as a FORTRAN IV subroutine to facilitate its use in finite element structural models. Input and output characteristics of the subroutine are described and a complete listing is attached as an appendix.

  9. Classical Aerodynamic Theory

    NASA Technical Reports Server (NTRS)

    Jones, R. T. (Compiler)

    1979-01-01

    A collection of papers on modern theoretical aerodynamics is presented. Included are theories of incompressible potential flow and research on the aerodynamic forces on wing and wing sections of aircraft and on airship hulls.

  10. A study of the nonlinear aerodynamics of bodies in nonplanar motion. Ph.D. Thesis - Stanford Univ., Calif.; [numerical analysis of aerodynamic force and moment systems during large amplitude, arbitrary motions

    NASA Technical Reports Server (NTRS)

    Schiff, L. B.

    1974-01-01

    Concepts from the theory of functionals are used to develop nonlinear formulations of the aerodynamic force and moment systems acting on bodies in large-amplitude, arbitrary motions. The analysis, which proceeds formally once the functional dependence of the aerodynamic reactions upon the motion variables is established, ensures the inclusion, within the resulting formulation, of pertinent aerodynamic terms that normally are excluded in the classical treatment. Applied to the large-amplitude, slowly varying, nonplanar motion of a body, the formulation suggests that the aerodynamic moment can be compounded of the moments acting on the body in four basic motions: steady angle of attack, pitch oscillations, either roll or yaw oscillations, and coning motion. Coning, where the nose of the body describes a circle around the velocity vector, characterizes the nonplanar nature of the general motion.

  11. Increased ephemeris accuracy using attitude-dependent aerodynamic force coefficients for inertially stabilized spacecraft

    NASA Technical Reports Server (NTRS)

    Folta, David C.; Baker, David F.

    1991-01-01

    The FREEMAC program used to generate the aerodynamic coefficients, as well as associated routines that allow the results to be used in other software is described. These capabilities are applied in two numerical examples to the short-term orbit prediction of the Gamma Ray Observatory (GRO) and Hubble Space Telescope (HST) spacecraft. Predictions using attitude-dependent aerodynamic coefficients were made on a modified version of the PC-based Ephemeris Generation Program (EPHGEN) and were compared to definitive orbit solutions obtained from actual tracking data. The numerical results show improvement in the predicted semi-major axis and along-track positions that would seem to be worth the added computational effort. Finally, other orbit and attitude analysis applications are noted that could profit from using FREEMAC-calculated aerodynamic coefficients, including orbital lifetime studies, orbit determination methods, attitude dynamics simulators, and spacecraft control system component sizing.

  12. The production of 'aerodynamically equivalent' drug and excipient inhalable powders using a novel fractionation technique.

    PubMed

    Taki, Mohammed; Marriott, Christopher; Zeng, Xian-Ming; Martin, Gary P

    2011-02-01

    Inhalation particles can be produced by various techniques such as milling, controlled crystallisation and spray-drying, but current methods cannot, to-date, precisely control the aerodynamic size distribution of produced powders. The aim of this study was to develop and validate a novel preparative technique whereby the efficient and reproducible aerodynamic fractionation of drug and excipient powders could be achieved. Salmeterol xinafoate (SX), fluticasone propionate (FP) and fine α-lactose monohydrate (FL) were chosen as model compounds. Powders were aerosolised using a dry powder feeder into a Next Generation Impactor operated at 60 L min(-1). Powders deposited on NGI stages were then collected and analysed. The fractionation process was successful for all powders producing significant linear correlations between the pre-set aerodynamic cut-off limits and geometric size measurements. For each of SX, FP and FL, sufficient powder quantities were recovered from NGI stages 1-6 producing six fractions with sequential aerodynamic and geometric particle size distributions. The fractionation technique was efficient and reproducible for all powders studied. The method can be equally applied to various drugs and excipients regardless of their previous production/processing history. Therefore, the aerodynamic fractionation technique may be used to compare and contrast samples produced by different processes. PMID:21185373

  13. Flight Test Determined Aerodynamics Force and Moment Characteristics of the X-43A Research Vehicle at Mach 7.0

    NASA Technical Reports Server (NTRS)

    Davis, Mark C.; White, J. Terry

    2006-01-01

    The second flight of the HYPER-X Program afforded a unique opportunity to determine the aerodynamic force and moment characteristics of an airframe integrated scramjet powered aircraft in hypersonic flight. These data were gathered via a repeated series of pitch, yaw, and roll doublets, frequency sweeps, and pull-up/push-over maneuvers performed throughout the X-43A cowl-closed descent phase. The subject flight research maneuvers were conducted in a Mach number range of 6.8 to 0.95 at altitudes from 92,000 ft to sea level. In this flight regime, the dynamic pressure varied from 1300 psf to 400 psf with angle-of-attack ranging from 0 deg to 14 deg. The flight-extracted aerodynamics were compared with pre-flight predictions based on wind tunnel test data. The X-43A flight-derived axial force was found to be 10 to 15 percent higher than prediction. Under-predictions of similar magnitude were observed for the normal force. For Mach numbers greater than 4, the X-43A flight-derived stability and control characteristics resulted in larger than predicted static margins, with the largest discrepancy approximately 5-inches forward along the X(CG) at Mach 6. This would result in less static margin in pitch. The X-43A predicted lateral-directional stability and control characteristics matched well with flight data when allowance was made for the high uncertainty in angle-of-sideslip.

  14. X-43A Flight-Test-Determined Aerodynamic Force and Moment Characteristics at Mach 7.0

    NASA Technical Reports Server (NTRS)

    Davis, Mark C.; White, J. Terry

    2008-01-01

    The second flight of the Hyper-X program afforded a unique opportunity to determine the aerodynamic force and moment characteristics of an airframe-integrated scramjet-powered aircraft in hypersonic flight. These data were gathered via a repeated series of pitch, yaw, and roll doublets, frequency sweeps, and pushover-pullup maneuvers performed throughout the X-43A cowl-closed descent. Maneuvers were conducted at Mach numbers of 6.80-0.95 and at altitudes from 92,000 ft mean sea level to sea level. The dynamic pressure varied from 1300 to 400 psf with the angle of attack ranging from 0 to 14 deg. The flight-extracted aerodynamics were compared with preflight predictions based on wind-tunnel test data. The X-43A flight-derived axial force was found to be 10-15%higher than prediction. Underpredictions of similar magnitude were observed for the normal force. For Mach numbers above 4.0, the flight-derived stability and control characteristics resulted in larger-than-predicted static margins, with the largest discrepancy approximately 5 in. forward along the x-axis center of gravity at Mach 6.0. This condition would result in less static margin in pitch. The predicted lateral-directional stability and control characteristics matched well with flight data when allowance was made for the high uncertainty in angle of sideslip.

  15. Flight-Test-Determined Aerodynamic Force and Moment Characteristics of the X-43A at Mach 7.0

    NASA Technical Reports Server (NTRS)

    Davis. Marl C.; White, J. Terry

    2006-01-01

    The second flight of the Hyper-X program afforded a unique opportunity to determine the aerodynamic force and moment characteristics of an airframe-integrated scramjet-powered aircraft in hypersonic flight. These data were gathered via a repeated series of pitch, yaw, and roll doublets; frequency sweeps; and pushover-pullup maneuvers performed throughout the X-43A cowl-closed descent. Maneuvers were conducted at Mach numbers of 6.80 to 0.95 and altitudes from 92,000 ft msl to sea level. The dynamic pressure varied from 1300 psf to 400 psf with the angle of attack ranging from 0 deg to 14 deg. The flight-extracted aerodynamics were compared with preflight predictions based on wind-tunnel-test data. The X-43A flight-derived axial force was found to be 10 percent to 15 percent higher than prediction. Under-predictions of similar magnitude were observed for the normal force. For Mach numbers above 4.0, the flight-derived stability and control characteristics resulted in larger-than-predicted static margins, with the largest discrepancy approximately 5 in. forward along the x-axis center of gravity at Mach 6.0. This condition would result in less static margin in pitch. The predicted lateral-directional stability and control characteristics matched well with flight data when allowance was made for the high uncertainty in angle of sideslip.

  16. PROP3D: A Program for 3D Euler Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Propellers. Version 1.0

    NASA Technical Reports Server (NTRS)

    Srivastava, R.; Reddy, T. S. R.

    1996-01-01

    This guide describes the input data required, for steady or unsteady aerodynamic and aeroelastic analysis of propellers and the output files generated, in using PROP3D. The aerodynamic forces are obtained by solving three dimensional unsteady, compressible Euler equations. A normal mode structural analysis is used to obtain the aeroelastic equations, which are solved using either time domain or frequency domain solution method. Sample input and output files are included in this guide for steady aerodynamic analysis of single and counter-rotation propellers, and aeroelastic analysis of single-rotation propeller.

  17. Attentional Focusing Instructions and Force Production

    PubMed Central

    Marchant, David C.

    2010-01-01

    Research progress assessing the role of attentional focusing instructions on skill acquisition and performance has lead researchers to apply this approach to force production tasks. Initial converging evidence indicates that force production tasks are sensitive to verbal instruction; externally focused instructions (onto movement outcomes, or onto the object force is being exerted against) are shown to be more beneficial than internally focused instructions (focusing attention onto the movements being executed). These benefits are observed for maximal and accurate force production, as well as the maintenance of force production in prolonged tasks. A range of mechanisms are identified supporting the proposal that an external focus promotes movement efficiency in line with energy and effort conservation. Future research is required to assess how this developing body of work interacts with the broader understanding of psychological and physiological factors implicated in the effective production, maintenance, and limitation of maximal or sub-maximal forces. PMID:21833266

  18. An Aerodynamic Force Estimation Method for Winged Models at the JAXA 60cm Magnetic Suspension and Balance System

    NASA Astrophysics Data System (ADS)

    澤田, 秀夫

    The aerodynamic performance of an AGARD-B model, as an example of a winged model, was measured in a low-speed wind tunnel equipped with the JAXA 60cm Magnetic Suspension and Balance System (MSBS). The flow speed was in the range between 25m/s and 35m/s, and the angle of attack and the yaw angle were in the range of [- 8, 4] and [- 3, 3] degrees, respectively. Six components of the aerodynamic force were evaluated by using the control coil currents of the MSBS. In evaluating the drag, the effect of the lift on the drag must be evaluated at MSBS when the lift is much larger than drag. A new evaluation method for drag and lift was proposed and was examined successfully by subjecting the model to the same loads as in the wind tunnel test. The drag coefficient at zero lift and the derivatives of the lift and pitching moment coefficient with respect to the angle of attack were evaluated and compared with other source data sets. The obtained data agreed well with the corresponding values of the other sources. The side force, yawing moment and rolling moment coefficients were also evaluated on the basis of corresponding calibration test results, and reasonable results were obtained, although they could not be compared due to the lack of reliable data sets.

  19. The effect of the nonlinear velocity and history dependencies of the aerodynamic force on the dynamic response of a rotating wind turbine blade

    NASA Astrophysics Data System (ADS)

    van der Male, Pim; van Dalen, Karel N.; Metrikine, Andrei V.

    2016-11-01

    Existing models for the analysis of offshore wind turbines account for the aerodynamic action on the turbine rotor in detail, requiring a high computational price. When considering the foundation of an offshore wind turbine, however, a reduced rotor model may be sufficient. To define such a model, the significance of the nonlinear velocity and history dependency of the aerodynamic force on a rotating blade should be known. Aerodynamic interaction renders the dynamics of a rotating blade in an ambient wind field nonlinear in terms of the dependency on the wind velocity relative to the structural motion. Moreover, the development in time of the aerodynamic force does not follow the flow velocity instantaneously, implying a history dependency. In addition, both the non-uniform blade geometry and the aerodynamic interaction couple the blade motions in and out of the rotational plane. Therefore, this study presents the Euler-Bernoulli formulation of a twisted rotating blade connected to a rigid hub, excited by either instantaneous or history-dependent aerodynamic forces. On this basis, the importance of the history dependency is determined. Moreover, to assess the nonlinear contributions, both models are linearized. The structural response is computed for a stand-still and a rotating blade, based on the NREL 5-MW turbine. To this end, the model is reduced on the basis of its first three free-vibration mode shapes. Blade tip response predictions, computed from turbulent excitation, correctly account for both modal and directional couplings, and the added damping resulting from the dependency of the aerodynamic force on the structural motion. Considering the deflection of the blade tip, the history-dependent and the instantaneous force models perform equally well, providing a basis for the potential use of the instantaneous model for the rotor reduction. The linearized instantaneous model provides similar results for the rotating blade, indicating its potential

  20. HRD and Productivity: Allied Forces.

    ERIC Educational Resources Information Center

    Nadler, Leonard

    1988-01-01

    The author defines productivity and discusses ways to increase productivity in the workplace, with emphasis on human resource development (HRD). He discusses the use of quality circles, participative management, and layoffs to increase productivity. (CH)

  1. Variance Components in Discrete Force Production Tasks

    PubMed Central

    SKM, Varadhan; Zatsiorsky, Vladimir M.; Latash, Mark L.

    2010-01-01

    The study addresses the relationships between task parameters and two components of variance, “good” and “bad”, during multi-finger accurate force production. The variance components are defined in the space of commands to the fingers (finger modes) and refer to variance that does (“bad”) and does not (“good”) affect total force. Based on an earlier study of cyclic force production, we hypothesized that speeding-up an accurate force production task would be accompanied by a drop in the regression coefficient linking the “bad” variance and force rate such that variance of the total force remains largely unaffected. We also explored changes in parameters of anticipatory synergy adjustments with speeding-up the task. The subjects produced accurate ramps of total force over different times and in different directions (force-up and force-down) while pressing with the four fingers of the right hand on individual force sensors. The two variance components were quantified, and their normalized difference was used as an index of a total force stabilizing synergy. “Good” variance scaled linearly with force magnitude and did not depend on force rate. “Bad” variance scaled linearly with force rate within each task, and the scaling coefficient did not change across tasks with different ramp times. As a result, a drop in force ramp time was associated with an increase in total force variance, unlike the results of the study of cyclic tasks. The synergy index dropped 100-200 ms prior to the first visible signs of force change. The timing and magnitude of these anticipatory synergy adjustments did not depend on the ramp time. Analysis of the data within an earlier model has shown adjustments in the variance of a timing parameter, although these adjustments were not as pronounced as in the earlier study of cyclic force production. Overall, we observed qualitative differences between the discrete and cyclic force production tasks: Speeding-up the cyclic

  2. Aerodynamic force generation and power requirements in forward flight in a fruit fly with modeled wing motion.

    PubMed

    Sun, Mao; Wu, Jiang Hao

    2003-09-01

    Aerodynamic force generation and power requirements in forward flight in a fruit fly with modeled wing motion were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the vorticity wake structure and the unsteady aerodynamic forces and torques were obtained (the inertial torques due to the acceleration of the wing-mass were computed analytically). From the flow-structure and force information, insights were gained into the unsteady aerodynamic force generation. On the basis of the aerodynamic and inertial torques, the mechanical power was obtained, and its properties were investigated. The unsteady force mechanisms revealed previously for hovering (i.e. delayed stall, rapid acceleration at the beginning of the strokes and fast pitching-up rotation at the end of the strokes) apply to forward flight. Even at high advance ratios, e.g. J=0.53-0.66 (J is the advance ratio), the leading edge vortex does not shed (at such advance ratios, the wing travels approximately 6.5 chord lengths during the downstroke). At low speeds (J approximately equal to 0.13), the lift (vertical force) for weight support is produced during both the down- and upstrokes (the downstroke producing approximately 80% and the upstroke producing approximately 20% of the mean lift), and the lift is contributed mainly by the wing lift; the thrust that overcomes the body drag is produced during the upstroke, and it is contributed mainly by the wing drag. At medium speeds (J approximately equal to 0.27), the lift is mainly produced during the downstroke and the thrust mainly during the upstroke; both of them are contributed almost equally by the wing lift and wing drag. At high speeds (J approximately equal to 0.53), the lift is mainly produced during the downstroke and is mainly contributed by the wing drag; the thrust is produced during both the down- and upstrokes, and in

  3. NASTRAN supplemental documentation for modal forced vibration analysis of aerodynamically excited turbosystems

    NASA Technical Reports Server (NTRS)

    Elchuri, V.; Pamidi, P. R.

    1985-01-01

    This report is a supplemental NASTRAN document for a new capability to determine the vibratory response of turbosystems subjected to aerodynamic excitation. Supplements of NASTRAN Theoretical, User's, Programmer's, and Demonstration Manuals are included. Turbosystems such as advanced turbopropellers with highly swept blades, and axial-flow compressors and turbines can be analyzed using this capability, which has been developed and implemented in the April 1984 release of the general purpose finite element program NASTRAN. The dynamic response problem is addressed in terms of the normal modal coordinates of these tuned rotating cyclic structures. Both rigid and flexible hubs/disks are considered. Coriolis and centripetal accelerations, as well as differential stiffness effects are included. Generally nonuniform steady inflow fields and uniform flow fields arbitrarily inclined at small angles with respect to the axis of rotation of the turbosystem are considered as the sources of aerodynamic excitation. The spatial nonuniformities are considered to be small deviations from a principally uniform inflow. Subsonic relative inflows are addressed, with provision for linearly interpolating transonic airloads.

  4. Perceived Submaximal Force Production in Young Adults

    ERIC Educational Resources Information Center

    Jackson, Allen W.; Ludtke, Andrew W.; Martin, Scott B.; Koziris, L. (Perry); Dishman, Rod K.

    2006-01-01

    The purpose of this investigation was to examine the force production patterns using perceived stimulus cues from 10% to 90% of maximal force. In Experiment 1, 54 men (age: 19-34 years) and 53 women (age: 18-37 years) performed leg extensions on a dynamometer at a speed of 60 degrees/s. Participants produced actual forces perceived to be 10-90% of…

  5. Calculation of aerodynamic forces on a propeller in pitch or yaw

    NASA Technical Reports Server (NTRS)

    Crigler, John L; Gilman, Jean, Jr

    1952-01-01

    An analysis was made to determine the applicability of existing propeller theory and the theory of oscillating airfoils to the problem of determining the magnitude of the forces on propellers in pitch or yaw. Strip calculations using compressible airfoil characteristics were first made as though steady-state conditions existed successively at several blade positions of the propeller blades during one revolution. A theory of oscillating airfoils in pulsating incompressible potential flow was then considered from which it was possible to determine factors which would modify the steady-state forces.

  6. Apparatus for experimental investigation of aerodynamic radiation with absorption by ablation products

    NASA Technical Reports Server (NTRS)

    Wells, W. L.; Snow, W. L.

    1977-01-01

    A description is given and calibration procedures are presented for an apparatus that is used to simulate aerodynamic radiant heating during planetary entry. The primary function of the apparatus is to simulate the spectral distribution of shock layer radiation and to determine absorption effects of simulated ablation products which are injected into the stagnation region flow field. An electric arc heater is used to heat gas mixtures that represent the planetary atmospheres of interest. Spectral measurements are made with a vacuum ultraviolet scanning monochromator.

  7. Numerical Study on the Flow Mechanism of Base Aerodynamic Force Acting on the Vertical Landing Rocket

    NASA Astrophysics Data System (ADS)

    Fujimatsu, Nobuyoshi; Suzuki, Kojiro

    The base flow field of a vertical landing rocket in ground effect is numerically studied to clarify the mechanism of downward force acting on the body. Two characteristic patterns in the pressure distribution on the base surface are successfully captured as observed in the experiments. When the distance between the base and the ground surface is small, vorticies generated in the shear layer of the jet boundary interact with both the ground and base surfaces. The base pressure near the axis of the base is significantly reduced and large downward force appears due to vortical structure in the base region. When the distance is large, the vorticies are convected along the ground surface and the base pressure near the edge of the vehicle base is reduced due to suction of the ambient air. The numerical results indicate that unsteady motion of such vortices plays an important role in formation of the flow patterns described above.

  8. The Aerodynamic Forces on Slender Plane- and Cruciform-Wing and Body Combinations

    NASA Technical Reports Server (NTRS)

    Spreiter, John R

    1950-01-01

    The load distribution, forces, and moments are calculated theoretically for inclined slender wing-body combinations consisting of a slender body of revolution and either a plane or cruciform arrangement of low-aspect-ratio pointed wings. The results are applicable at subsonic and transonic speeds, and at supersonic speeds, provided the entire wing-body combination lies near the center of the Mach cone.

  9. The mechanical forces in katydid sound production

    NASA Astrophysics Data System (ADS)

    Xiao, Huaping; Chiu, Cheng-Wei; Zhou, Yan; He, Xingliang; Epstein, Ben; Liang, Hong

    2013-10-01

    Katydids and crickets generate their characteristic calling sound by rubbing their wings together. The mechanisms of the rubbing force, however, have not been extensively studied. The change of mechanical force with external parameters (speed and applied load) in the stridulation process has not been reported. Our current study aims to investigate the mechanical forces of katydid stridulation. Four pairs of files and plectrums from a katydid, which are responsible for the katydid's sound production, were examined with a specially designed experimental configuration. Due to the asymmetric nature of the wing motion in their opening and closing, the contact between the plectrum and file resembles that of a ratchet. Multiple frequencies were generated during experimental wing rubbing so that a calling-like sound was produced. Results showed that the morphology of the plectrum/file contact has significant effects on mechanical forces induced on the wings and resulting sound production. The roles of the mechanical forces include sound generation, tone modification, and energy consumption. The findings in this work reveal the variation trend of mechanical force with sliding speed and applied load. The frequency and amplitude of the sound wave produced in tribo-test are close to those in natural condition. By mimicking the microstructure of the plectrum and file teeth, acoustic instruments with high mechanical energy conversion rate can be developed. Our results provide new approaches in the design and improvement of micro-machines for acoustic applications, as well as in hybrid robotic systems.

  10. Vortexlet models of flapping flexible wings show tuning for force production and control.

    PubMed

    Mountcastle, A M; Daniel, T L

    2010-12-01

    Insect wings are compliant structures that experience deformations during flight. Such deformations have recently been shown to substantially affect induced flows, with appreciable consequences to flight forces. However, there are open questions related to the aerodynamic mechanisms underlying the performance benefits of wing deformation, as well as the extent to which such deformations are determined by the boundary conditions governing wing actuation together with mechanical properties of the wing itself. Here we explore aerodynamic performance parameters of compliant wings under periodic oscillations, subject to changes in phase between wing elevation and pitch, and magnitude and spatial pattern of wing flexural stiffness. We use a combination of computational structural mechanics models and a 2D computational fluid dynamics approach to ask how aerodynamic force production and control potential are affected by pitch/elevation phase and variations in wing flexural stiffness. Our results show that lift and thrust forces are highly sensitive to flexural stiffness distributions, with performance optima that lie in different phase regions. These results suggest a control strategy for both flying animals and engineering applications of micro-air vehicles.

  11. Vortexlet models of flapping flexible wings show tuning for force production and control.

    PubMed

    Mountcastle, A M; Daniel, T L

    2010-12-01

    Insect wings are compliant structures that experience deformations during flight. Such deformations have recently been shown to substantially affect induced flows, with appreciable consequences to flight forces. However, there are open questions related to the aerodynamic mechanisms underlying the performance benefits of wing deformation, as well as the extent to which such deformations are determined by the boundary conditions governing wing actuation together with mechanical properties of the wing itself. Here we explore aerodynamic performance parameters of compliant wings under periodic oscillations, subject to changes in phase between wing elevation and pitch, and magnitude and spatial pattern of wing flexural stiffness. We use a combination of computational structural mechanics models and a 2D computational fluid dynamics approach to ask how aerodynamic force production and control potential are affected by pitch/elevation phase and variations in wing flexural stiffness. Our results show that lift and thrust forces are highly sensitive to flexural stiffness distributions, with performance optima that lie in different phase regions. These results suggest a control strategy for both flying animals and engineering applications of micro-air vehicles. PMID:21098955

  12. User's Guide for MSAP2D: A Program for Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Multistage Compressors and Turbines. 1.0

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.; Srivastava, R.

    1996-01-01

    This guide describes the input data required for using MSAP2D (Multi Stage Aeroelastic analysis Program - Two Dimensional) computer code. MSAP2D can be used for steady, unsteady aerodynamic, and aeroelastic (flutter and forced response) analysis of bladed disks arranged in multiple blade rows such as those found in compressors, turbines, counter rotating propellers or propfans. The code can also be run for single blade row. MSAP2D code is an extension of the original NPHASE code for multiblade row aerodynamic and aeroelastic analysis. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The aeroelastic equations are solved in time domain. For single blade row analysis, frequency domain analysis is also provided to obtain unsteady aerodynamic coefficients required in an eigen analysis for flutter. In this manual, sample input and output are provided for a single blade row example, two blade row example with equal and unequal number of blades in the blade rows.

  13. Bilateral synergies in foot force production tasks.

    PubMed

    Sarabon, Nejc; Markovic, Goran; Mikulic, Pavle; Latash, Mark L

    2013-05-01

    We analysed the effects of task symmetry during bilateral accurate force production tasks performed by the two feet. In particular, we tested a hypothesis that bilateral deficit would lead to higher indices of synergies defined as co-varied adjustments in the two forces across trials that reduced total force variability. The subjects produced steady-state force followed by a quick force pulse into the target. The two feet could be acting both into plantar flexion and into dorsiflexion (symmetrical tasks), or in opposite directions (asymmetrical task). We used the framework of the uncontrolled manifold hypothesis to quantify two variance components, one of which did not change total force (V UCM), while the other did (V ORT). Synergy indices during the asymmetrical task were higher than in either symmetrical task. The difference was due to higher V UCM (compared to the symmetrical plantar flexion task) or lower V ORT (compared to the symmetrical dorsiflexion task). The synergy index showed a drop (anticipatory synergy adjustment, ASA) starting 100-150 ms prior to the force pulse initiation. The ASA tended to be shorter and of a smaller magnitude for the asymmetrical task. This is the first demonstration of bilateral synergies during accurate force production by the legs. We conclude that bilateral deficit has no or weak effects on two-leg synergies. The results fit the earlier introduced scheme with two groups of neural variables defining average performance of a redundant system and patterns of co-variation among its elemental variables, respectively. PMID:23568657

  14. The effect of solar forcing induced atmospheric perturbations on LEO satellites' nominal aerodynamic drag

    NASA Astrophysics Data System (ADS)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar; Weigel, Robert

    2016-07-01

    Atmospheric drag is the strongest force perturbing the motion of satellites in low Earth orbits LEO, and could cause re-entry of satellites, difficulty in identifying and tracking of the satellites and other space objects, manuvering and prediction of lifetime and re-entry. Solar activities influence the temperature, density and composition of the upper atmosphere. These effects thus strongly depend on the phase of a solar cycle. The frequency of intense flares and storms increase during solar maximum. Heating up of the atmosphere causes its expansion eventually leading to accelerated drag of orbiting satellites, especially those in LEO. In this paper, we present the model of the atmospheric drag effect on the trajectory of hypothetical LEO satellites of different ballistic coefficients. We investigate long-term trend of atmospheric drag on LEO satellites due to solar forcing induced atmospheric perturbations and heating at different phases of the solar cycle, and during interval of strong geomagnetic disturbances or storms. We show the dependence of orbital decay on severity of both the solar cycle and phase, and the extent of geomagnetic perturbations. The result of the model compares well with the observed decay profile of existing LEO satellites and provides a better understanding of the issue of the orbital decay. Our result may also be useful for selection of launch window of satellites for an extended lifetime in the orbit.

  15. Sensitivity of aerodynamic forces in laminar and turbulent flow past a square cylinder

    NASA Astrophysics Data System (ADS)

    Meliga, Philippe; Boujo, Edouard; Pujals, Gregory; Gallaire, François

    2014-10-01

    We use adjoint-based gradients to analyze the sensitivity of the drag force on a square cylinder. At Re = 40, the flow settles down to a steady state. The quantity of interest in the adjoint formulation is the steady asymptotic value of drag reached after the initial transient, whose sensitivity is computed solving a steady adjoint problem from knowledge of the stable base solution. At Re = 100, the flow develops to the time-periodic, vortex-shedding state. The quantity of interest is rather the time-averaged mean drag, whose sensitivity is computed integrating backwards in time an unsteady adjoint problem from knowledge of the entire history of the vortex-shedding solution. Such theoretical frameworks allow us to identify the sensitive regions without computing the actually controlled states, and provide a relevant and systematic guideline on where in the flow to insert a secondary control cylinder in the attempt to reduce drag, as established from comparisons with dedicated numerical simulations of the two-cylinder system. For the unsteady case at Re = 100, we also compute an approximation to the mean drag sensitivity solving a steady adjoint problem from knowledge of only the mean flow solution, and show the approach to carry valuable information in view of guiding relevant control strategy, besides reducing tremendously the related numerical effort. An extension of this simplified framework to turbulent flow regime is examined revisiting the widely benchmarked flow at Reynolds number Re = 22 000, the theoretical predictions obtained in the frame of unsteady Reynolds-averaged Navier-Stokes modeling being consistent with experimental data from the literature. Application of the various sensitivity frameworks to alternative control objectives such as increasing the lift and reducing the fluctuating drag and lift is also discussed and illustrated with a few selected examples.

  16. 'Psyching-up' and muscular force production.

    PubMed

    Tod, David; Iredale, Fiona; Gill, Nicholas

    2003-01-01

    Psyching-up refers to self-directed cognitive strategies used immediately prior to or during skill execution that are designed to enhance performance. This review focuses on research that has investigated the effect of psyching-up on force production; specifically, strength, muscular endurance and power. Although firm conclusions are not possible, the research tentatively suggests that psyching-up may enhance performance during dynamic tasks requiring strength and/or muscular endurance. However, more research is required. Power has received scant empirical attention and there are not enough data to support any conclusions. Preparatory arousal appears to be the most effective strategy although other strategies like imagery, self-talk and attentional focus also have empirical support. The range of tasks that have been used to measure force production have been limited to movements such as handgrip, leg extension, bench press, sit-ups, press-ups, pull-ups, and the standing broad jump. Additionally, most studies have used undergraduate and/or untrained samples. Only a very small number of studies have examined well-trained individuals. Currently, no explanation for why psyching-up may influence force production has any substantive support. Although a small number of studies have examined moderating and mediating variables, few consistent patterns have emerged and knowledge in this area is somewhat restricted. Given the importance that many athletes place on their mental preparation just prior to performance this is an area that warrants further examination. Research needs to examine a range of complex sport-specific tasks and use well-trained samples. Additionally, research needs to further examine why psyching-up may enhance force production. PMID:12477377

  17. Propulsion and airframe aerodynamic interactions of supersonic V/STOL configurations. Volume 2: Wind tunnel test force and moment data report

    NASA Technical Reports Server (NTRS)

    Zilz, D. E.

    1985-01-01

    A wind tunnel model of a supersonic V/STOL fighter configuration has been tested to measure the aerodynamic interaction effects which can result from geometrically close-coupled propulsion system/airframe components. The approach was to configure the model to represent two different test techniques. One was a conventional test technique composed of two test modes. In the Flow-Through mode, absolute configuration aerodynamics are measured, including inlet/airframe interactions. In the Jet-Effects mode, incremental nozzle/airframe interactions are measured. The other test technique is a propulsion simulator approach, where a sub-scale, externally powered engine is mounted in the model. This allows proper measurement of inlet/airframe and nozzle/airframe interactions simultaneously. This is Volume 2 of 2: Wind Tunnel Test Force and Moment Data Report.

  18. Projectiles and Aerodynamic Forces.

    ERIC Educational Resources Information Center

    Armstrong, H. L.

    1984-01-01

    Discusses the air resistance on projectiles, examining (in separate sections) air resistance less than gravity and air resistance greater than gravity. Also considers an approximation in which a trajectory is divided into two parts, the first part neglecting gravity and the second part neglecting the air resistance. (JN)

  19. The effects on propulsion-induced aerodynamic forces of vectoring a partial-span rectangular jet at Mach numbers from 0.40 to 1.20

    NASA Technical Reports Server (NTRS)

    Capone, F. J.

    1975-01-01

    An investigation was conducted in the Langley 16-foot transonic tunnel to determine the induced lift characteristics of a vectored thrust concept in which a rectangular jet exhaust nozzle was located in the fuselage at the wing trailing edge. The effects of nozzle deflection angles of 0 deg to 45 deg were studied at Mach numbers from 0.4 to 1.2, at angles of attack up to 14 deg, and with thrust coefficients up to 0.35. Separate force balances were used to determine total aerodynamic and thrust forces as well as thrust forces which allowed a direct measurement of jet turning angle at forward speeds. Wing pressure loading and flow characteristics using oil flow techniques were also studied.

  20. Force production in the rugby union scrum.

    PubMed

    Quarrie, K L; Wilson, B D

    2000-04-01

    In this study, we examined the relationship between anthropometric, strength and power characteristics of rugby forwards, their body position when scrummaging, and their ability to apply force when scrummaging. Force applied to an instrumented scrum machine was measured for 56 players, both individually and as scrum packs. Measurements of body position for individuals were made by digitizing videotape records of the trials. Forty players subsequently had their anthropometry assessed and completed several strength and power tests. Body mass, each component of somatotype, maximal anaerobic power developed on a cycle ergometer, and isokinetic knee extension strength correlated significantly with individual scrummaging force. A regression model (P < 0.001) including body mass, mesomorphy, maximal anaerobic power and hip angle while in the scrummaging position accounted for 45% of the variance in individual scrummaging force. The packs that produced the largest scrummaging forces were, in general, characterized by a greater pack force to sum of individual force ratio than the packs producing lower forces. Our results emphasize the need for a scrum pack to develop technique and coordination as a unit to maximize scrummaging force. PMID:10824640

  1. Effects of Force Requirements on Pinch Force Production in Healthy Adults.

    PubMed

    Khan, Aisha; Gorniak, Stacey L

    2016-07-01

    Previous studies of fine motor control have focused on the ability of participants to match their grip force production to a visually provided template. We investigated differences exhibited in pinch force control during variable force production templates, including sine-, sawtooth-, and square-wave templates. Our results indicate that increased force requirements are associated with increased error rates and a noisier frequency spectrum, consistent with previous studies. Our results also indicate that visual feedback, in the form of template shape, directly affect pinch force production features and motor unit firing patterns, despite the use of consistent baseline force requirements, amplitude changes, and visual signal frequency. This suggests that CNS modulation of motor unit responses can be triggered by basic changes in visual feedback unrelated to force requirements. The potential implications of error compensation based on this study due to aging are also discussed.

  2. Aerodynamics of a Party Balloon

    ERIC Educational Resources Information Center

    Cross, Rod

    2007-01-01

    It is well-known that a party balloon can be made to fly erratically across a room, but it can also be used for quantitative measurements of other aspects of aerodynamics. Since a balloon is light and has a large surface area, even relatively weak aerodynamic forces can be readily demonstrated or measured in the classroom. Accurate measurements…

  3. Aerodynamic potpourri

    NASA Technical Reports Server (NTRS)

    Wilson, R. E.

    1981-01-01

    Aerodynamic developments for vertical axis and horizontal axis wind turbines are given that relate to the performance and aerodynamic loading of these machines. Included are: (1) a fixed wake aerodynamic model of the Darrieus vertical axis wind turbine; (2) experimental results that suggest the existence of a laminar flow Darrieus vertical axis turbine; (3) a simple aerodynamic model for the turbulent windmill/vortex ring state of horizontal axis rotors; and (4) a yawing moment of a rigid hub horizontal axis wind turbine that is related to blade coning.

  4. Aerodynamic potpourri

    NASA Astrophysics Data System (ADS)

    Wilson, R. E.

    1981-05-01

    Aerodynamic developments for vertical axis and horizontal axis wind turbines are given that relate to the performance and aerodynamic loading of these machines. Included are: (1) a fixed wake aerodynamic model of the Darrieus vertical axis wind turbine; (2) experimental results that suggest the existence of a laminar flow Darrieus vertical axis turbine; (3) a simple aerodynamic model for the turbulent windmill/vortex ring state of horizontal axis rotors; and (4) a yawing moment of a rigid hub horizontal axis wind turbine that is related to blade coning.

  5. The nature of constant and cyclic force production: unintentional force-drift characteristics.

    PubMed

    Ambike, Satyajit; Mattos, Daniela; Zatsiorsky, Vladimir M; Latash, Mark L

    2016-01-01

    We explored unintentional changes in forces during performance of constant and cyclic force-production tasks (F-tasks) after visual feedback removal. Based on earlier studies, we expected all force parameters to drop exponentially with time. We also explored possible role of working memory in the force drop phenomena. Healthy subjects performed constant or cyclic isometric F-tasks with the index finger under visual feedback. The cyclic task was paced by a metronome. Removing visual feedback resulted in a consistent force drop in constant F-tasks and a qualitatively similar drift in the mean force in the cyclic F-task. Both were slow with characteristic times of about 10-20 s. In contrast, force amplitude in the cyclic F-task increased quickly (within 1-2 s). When the subjects were asked to stop producing force for 5 s after the visual feedback disappeared and then resume force production, no downward force drift was seen in constant F-tasks, while in cyclic F-tasks, the drift of the mean force was present and an exaggerated increase in force amplitude was also observed. We conclude that while working memory limitations may influence cyclic F-tasks, their role in determining the force drift in constant F-tasks is limited. The results of both experiments are interpreted within the referent configuration hypothesis supplemented with an idea of unintentional drift of referent coordinates (RC-back-coupling) induced by differences between the referent and actual body configurations. PMID:26419663

  6. Women's employment and the production force.

    PubMed

    Li, S

    1990-01-01

    The economic problem of women in China is discussed in terms of the diversification of women's jobs, the growth in women's employment rate, and improvements in women's employment structure. Any change in women's employment status must be compatible with social production forces of labor organization patterns and the demand in professional fields. Fields of employment that are suitable for women need to be expanded. The division of labor is such that men are predominately in heavy industry and women in light industry. The physical makeup of women puts them at a disadvantage, as well as their role in child rearing. The service industry is open to women. The number of new jobs is rapidly increasing in occupations that require more mental work and hence open to women, such as, office maintenance, computer services' technician, computer programmer, and law associates or electrical engineer. The semiconductor industry statistics in southeast Asia reveal that 90% of unmarried women 16-23 years are employed in this industry. Improvement in women's educational levels also provide opportunities. The largest proportion of jobs are still in agriculture, while the country is changing from a natural economy to a market-oriented one. More women are engaged in employment in developed countries, and there is regional variation in female employment patterns. Comparisons are made for countries in southeast Asia in the % of working women. The increase in working women is attributed to increases in very young (16-23 years) and very old (65 years) women. Women's employment has grown on an annual average of 23.7% vs. 15% for the world. During times of economic recession, women's employment grew but in low level jobs. Women in state-owned enterprises rose from 7.5% in 1949 to 32.0% in 1984. Growth for women was fastest in the service industry (4.1%-39.8%), followed closely by scientific research institutions and health services (11.4%-38.2%). Women in agriculture and forestry rose from 2

  7. Investigating the Force Production of Functionally-Graded Flexible Wings in Flapping Wing Flight

    NASA Astrophysics Data System (ADS)

    Mudbhari, Durlav; Erdogan, Malcolm; He, Kai; Bateman, Daniel; Lipkis, Rory; Moored, Keith

    2015-11-01

    Birds, insects and bats oscillate their wings to propel themselves over long distances and to maneuver with unprecedented agility. A key element to achieve their impressive aerodynamic performance is the flexibility of their wings. Numerous studies have shown that homogeneously flexible wings can enhance force production, propulsive efficiency and lift efficiency. Yet, animal wings are not homogenously flexible, but instead have varying material properties. The aim of this study is to characterize the force production and energetics of functionally-graded flexible wings. A partially-flexible wing composed of a rigid section and a flexible section is used as a first-order model of functionally-graded materials. The flexion occurs in the spanwise direction and it is affected by the spanwise flexion ratio, that is, the ratio of the length of the rigid section compared to the total span length. By varying the flexion ratio as well as the material properties of the flexible section, the study aims to examine the force production and energetics of flapping flight with functionally-graded flexible wings. Supported by the Office of Naval Research under Program Director Dr. Bob Brizzolara, MURI grant number N00014-14-1-0533.

  8. Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach.

    PubMed

    Nakata, Toshiyuki; Liu, Hao

    2012-02-22

    Insect wings are deformable structures that change shape passively and dynamically owing to inertial and aerodynamic forces during flight. It is still unclear how the three-dimensional and passive change of wing kinematics owing to inherent wing flexibility contributes to unsteady aerodynamics and energetics in insect flapping flight. Here, we perform a systematic fluid-structure interaction based analysis on the aerodynamic performance of a hovering hawkmoth, Manduca, with an integrated computational model of a hovering insect with rigid and flexible wings. Aerodynamic performance of flapping wings with passive deformation or prescribed deformation is evaluated in terms of aerodynamic force, power and efficiency. Our results reveal that wing flexibility can increase downwash in wake and hence aerodynamic force: first, a dynamic wing bending is observed, which delays the breakdown of leading edge vortex near the wing tip, responsible for augmenting the aerodynamic force-production; second, a combination of the dynamic change of wing bending and twist favourably modifies the wing kinematics in the distal area, which leads to the aerodynamic force enhancement immediately before stroke reversal. Moreover, an increase in hovering efficiency of the flexible wing is achieved as a result of the wing twist. An extensive study of wing stiffness effect on aerodynamic performance is further conducted through a tuning of Young's modulus and thickness, indicating that insect wing structures may be optimized not only in terms of aerodynamic performance but also dependent on many factors, such as the wing strength, the circulation capability of wing veins and the control of wing movements. PMID:21831896

  9. Human capacity for explosive force production: neural and contractile determinants.

    PubMed

    Folland, J P; Buckthorpe, M W; Hannah, R

    2014-12-01

    This study assessed the integrative neural and contractile determinants of human knee extension explosive force production. Forty untrained participants performed voluntary and involuntary (supramaximally evoked twitches and octets - eight pulses at 300 Hz that elicit the maximum possible rate of force development) explosive isometric contractions of the knee extensors. Explosive force (F0-150 ms) and sequential rate of force development (RFD, 50-ms epochs) were measured. Surface electromyography (EMG) amplitude was recorded (superficial quadriceps and hamstrings, 50-ms epochs) and normalized (quadriceps to Mmax, hamstrings to EMGmax). Maximum voluntary force (MVF) was also assessed. Multiple linear regressions assessed the significant neural and contractile determinants of absolute and relative (%MVF) explosive force and sequential RFD. Explosive force production exhibited substantial interindividual variability, particularly during the early phase of contraction [F50, 13-fold (absolute); 7.5-fold (relative)]. Multiple regression explained 59-93% (absolute) and 35-60% (relative) of the variance in explosive force production. The primary determinants of explosive force changed during the contraction (F0-50, quadriceps EMG and Twitch F; RFD50-100, Octet RFD0-50; F100-150, MVF). In conclusion, explosive force production was largely explained by predictor neural and contractile variables, but the specific determinants changed during the phase of contraction.

  10. Numerical investigation on the flow characteristics and aerodynamic force of the upper airway of patient with obstructive sleep apnea using computational fluid dynamics.

    PubMed

    Jeong, Soo-Jin; Kim, Woo-Seung; Sung, Sang-Jin

    2007-07-01

    Developing a mathematical model to predict the abnormal flow characteristics that are produced by obstructive sleep apnea is an important step in learning the pathophysiology of the obstructive sleep apnea (OSA) disease. The present study provides detailed calculations of flow in the pharyngeal airway of a patient with obstructive sleep apnea. To achieve this goal, a computational fluid dynamics model was constructed using raw data from three-dimensional computed tomogram (CT) images of an OSA patient. To reproduce the important transition from laminar to turbulent flow in the pharyngeal airway, the low Reynolds number k-epsilon model was adopted and successfully validated using previous open literature. The results show that the flow in the pharyngeal airway of patients with OSA comprises a turbulent jet formed by area restriction at the velopharynx. This turbulent jet causes higher shear and pressure forces in the vicinity of the velopharynx. From the results, It may be deduced that the most collapsible area in the pharyngeal airway of OSA patients is the velopharynx where minimum intraluminal pressure and maximum aerodynamic force lie.

  11. Evaluation of the Hinge Moment and Normal Force Aerodynamic Loads from a Seamless Adaptive Compliant Trailing Edge Flap in Flight

    NASA Technical Reports Server (NTRS)

    Miller, Eric J.; Cruz, Josue; Lung, Shun-Fat; Kota, Sridhar; Ervin, Gregory; Lu, Kerr-Jia; Flick, Pete

    2016-01-01

    A seamless adaptive compliant trailing edge (ACTE) flap was demonstrated in flight on a Gulfstream III aircraft at the NASA Armstrong Flight Research Center. The trailing edge flap was deflected between minus 2 deg up and plus 30 deg down in flight. The safety-of-flight parameters for the ACTE flap experiment require that flap-to-wing interface loads be sensed and monitored in real time to ensure that the structural load limits of the wing are not exceeded. The attachment fittings connecting the flap to the aircraft wing rear spar were instrumented with strain gages and calibrated using known loads for measuring hinge moment and normal force loads in flight. The safety-of-flight parameters for the ACTE flap experiment require that flap-to-wing interface loads be sensed and monitored in real time to ensure that the structural load limits of the wing are not exceeded. The attachment fittings connecting the flap to the aircraft wing rear spar were instrumented with strain gages and calibrated using known loads for measuring hinge moment and normal force loads in flight. The interface hardware instrumentation layout and load calibration are discussed. Twenty-one applied calibration test load cases were developed for each individual fitting. The 2-sigma residual errors for the hinge moment was calculated to be 2.4 percent, and for normal force was calculated to be 7.3 percent. The hinge moment and normal force generated by the ACTE flap with a hinge point located at 26-percent wing chord were measured during steady state and symmetric pitch maneuvers. The loads predicted from analysis were compared to the loads observed in flight. The hinge moment loads showed good agreement with the flight loads while the normal force loads calculated from analysis were over-predicted by approximately 20 percent. Normal force and hinge moment loads calculated from the pressure sensors located on the ACTE showed good agreement with the loads calculated from the installed strain gages.

  12. Aerodynamic effects of flexibility in flapping wings.

    PubMed

    Zhao, Liang; Huang, Qingfeng; Deng, Xinyan; Sane, Sanjay P

    2010-03-01

    Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re approximately 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small

  13. Aerodynamic effects of flexibility in flapping wings

    PubMed Central

    Zhao, Liang; Huang, Qingfeng; Deng, Xinyan; Sane, Sanjay P.

    2010-01-01

    Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re ≈ 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small robotic

  14. Force production and mechanical accommodation during convergent extension

    PubMed Central

    Zhou, Jian; Pal, Siladitya; Maiti, Spandan; Davidson, Lance A.

    2015-01-01

    Forces generated within the embryo during convergent extension (CE) must overcome mechanical resistance to push the head away from the rear. As mechanical resistance increases more than eightfold during CE and can vary twofold from individual to individual, we have proposed that developmental programs must include mechanical accommodation in order to maintain robust morphogenesis. To test this idea and investigate the processes that generate forces within early embryos, we developed a novel gel-based sensor to report force production as a tissue changes shape; we find that the mean stress produced by CE is 5.0±1.6 Pascal (Pa). Experiments with the gel-based force sensor resulted in three findings. (1) Force production and mechanical resistance can be coupled through myosin contractility. The coupling of these processes can be hidden unless affected tissues are challenged by physical constraints. (2) CE is mechanically adaptive; dorsal tissues can increase force production up to threefold to overcome a stiffer microenvironment. These findings demonstrate that mechanical accommodation can ensure robust morphogenetic movements against environmental and genetic variation that might otherwise perturb development and growth. (3) Force production is distributed between neural and mesodermal tissues in the dorsal isolate, and the notochord, a central structure involved in patterning vertebrate morphogenesis, is not required for force production during late gastrulation and early neurulation. Our findings suggest that genetic factors that coordinately alter force production and mechanical resistance are common during morphogenesis, and that their cryptic roles can be revealed when tissues are challenged by controlled biophysical constraints. PMID:25670794

  15. Aerodynamic excitation and sound production of blown-closed free reeds without acoustic coupling: the example of the accordion reed.

    PubMed

    Ricot, Denis; Caussé, René; Misdariis, Nicolas

    2005-04-01

    The accordion reed is an example of a blown-closed free reed. Unlike most oscillating valves in wind musical instruments, self-sustained oscillations occur without acoustic coupling. Flow visualizations and measurements in water show that the flow can be supposed incompressible and potential. A model is developed and the solution is calculated in the time domain. The excitation force is found to be associated with the inertial load of the unsteady flow through the reed gaps. Inertial effect leads to velocity fluctuations in the reed opening and then to an unsteady Bernoulli force. A pressure component generated by the local reciprocal air movement around the reed is added to the modeled aerodynamic excitation pressure. Since the model is two-dimensional, only qualitative comparisons with air flow measurements are possible. The agreement between the simulated pressure waveforms and measured pressure in the very near-field of the reed is reasonable. In addition, an aeroacoustic model using the permeable Ffowcs Williams-Hawkings integral method is presented. The integral expressions of the far-field acoustic pressure are also computed in the time domain. In agreement with experimental data, the sound is found to be dominated by the dipolar source associated by the strong momentum fluctuations of the flow through the reed gaps. PMID:15898668

  16. Steady, Oscillatory, and Unsteady Subsonic and Supersonic Aerodynamics, production version (SOUSSA-P 1.1). Volume 1: Theoretical manual. [Green function

    NASA Technical Reports Server (NTRS)

    Morino, L.

    1980-01-01

    Recent developments of the Green's function method and the computer program SOUSSA (Steady, Oscillatory, and Unsteady Subsonic and Supersonic Aerodynamics) are reviewed and summarized. Applying the Green's function method to the fully unsteady (transient) potential equation yields an integro-differential-delay equation. With spatial discretization by the finite-element method, this equation is approximated by a set of differential-delay equations in time. Time solution by Laplace transform yields a matrix relating the velocity potential to the normal wash. Premultiplying and postmultiplying by the matrices relating generalized forces to the potential and the normal wash to the generalized coordinates one obtains the matrix of the generalized aerodynamic forces. The frequency and mode-shape dependence of this matrix makes the program SOUSSA useful for multiple frequency and repeated mode-shape evaluations.

  17. On Wings: Aerodynamics of Eagles.

    ERIC Educational Resources Information Center

    Millson, David

    2000-01-01

    The Aerodynamics Wing Curriculum is a high school program that combines basic physics, aerodynamics, pre-engineering, 3D visualization, computer-assisted drafting, computer-assisted manufacturing, production, reengineering, and success in a 15-hour, 3-week classroom module. (JOW)

  18. A preliminary study of using a strain-gauged balance and parameter estimation techniques for the determination of aerodynamic forces on a model in a very short duration wind tunnel

    NASA Astrophysics Data System (ADS)

    Brown, A. P.; Feik, R. A.

    1983-12-01

    This memo presents a preliminary study of a proposed method of measuring the aerodynamic forces on a supported model in an intermittent very short duration wind tunnel with a relatively high airflow dynamic pressure (of the orders of 200 microsec and 1/3 atmosphere respectively). A semiconductor strain gauged cantilever beam balance is used to record strain time histories associated with model displacement in response to aerodynamic force. The practical feasibility of obtaining sufficiently resolvable strains for the prescribed tunnel conditions with the given strain gauge configuration is established. The proposed method uses a system identification procedure to determine the system dynamic response characteristics using a known calibration force input. Subsequently, aerodynamic forces during a tunnel run follow from the recorded strain gauge time histories. The procedure has been demonstrated successfully using simulated data. However, the experimental situation did not lead to a successful analysis in the way proposed. Reasons for this are discussed and recommendations made for improvements. A brief series of shots in the ANU free piston shock tunnel also highlights the need to isolate as much as possible the model/balance from external vibrations.

  19. Aerodynamic drag in cycling: methods of assessment.

    PubMed

    Debraux, Pierre; Grappe, Frederic; Manolova, Aneliya V; Bertucci, William

    2011-09-01

    When cycling on level ground at a speed greater than 14 m/s, aerodynamic drag is the most important resistive force. About 90% of the total mechanical power output is necessary to overcome it. Aerodynamic drag is mainly affected by the effective frontal area which is the product of the projected frontal area and the coefficient of drag. The effective frontal area represents the position of the cyclist on the bicycle and the aerodynamics of the cyclist-bicycle system in this position. In order to optimise performance, estimation of these parameters is necessary. The aim of this study is to describe and comment on the methods used during the last 30 years for the evaluation of the effective frontal area and the projected frontal area in cycling, in both laboratory and actual conditions. Most of the field methods are not expensive and can be realised with few materials, providing valid results in comparison with the reference method in aerodynamics, the wind tunnel. Finally, knowledge of these parameters can be useful in practice or to create theoretical models of cycling performance.

  20. A note on the stochastic nature of particle cohesive force and implications to threshold friction velocity for aerodynamic dust entrainment

    NASA Astrophysics Data System (ADS)

    Shao, Yaping; Klose, Martina

    2016-09-01

    There is considerable interest to determine the threshold for aeolian dust emission on Earth and Mars. Existing schemes for threshold friction velocity are all deterministic in nature, but observations show that in the dust particle size range the threshold friction velocity scatters strongly due to stochastic inter-particle cohesion. In the real world, there always exists a certain amount of free dust which can be easily lifted from the surface by weak winds or even turbulence, as exemplified by dust devils. It has been proposed in the dust-devil research community, that the pressure drop at dust-devil center may be a major mechanism for dust-devil dust emission, known as the Δp effect. It is questioned here whether the Δp effect is substantial or whether the elevated dust concentration in dust devils is due to free dust emission. A simple analysis indicates that the Δp effect appears to be small and the dust in dust devils is probably due to free dust emission and dust convergence. To estimate free dust emission, it is useful to define a lower limit of dust-particle threshold friction velocity. A simple expression for this velocity is proposed by making assumptions to the median and variance of inter-particle cohesive force. The simple expression is fitted to the data of the Arizona State University Vortex Generator. While considerable uncertainty remains in the scheme, this note highlights the need for additional research on the stochastic nature of dust emission.

  1. Force production during maximal effort bend sprinting: Theory vs reality.

    PubMed

    Churchill, S M; Trewartha, G; Bezodis, I N; Salo, A I T

    2016-10-01

    This study investigated whether the "constant limb force" hypothesis can be applied to bend sprinting on an athletics track and to understand how force production influences performance on the bend compared with the straight. Force and three-dimensional video analyses were conducted on seven competitive athletes during maximal effort sprinting on the bend (radius 37.72 m) and straight. Left step mean peak vertical and resultant force decreased significantly by 0.37 body weight (BW) and 0.21 BW, respectively, on the bend compared with the straight. Right step force production was not compromised in the same way, and some athletes demonstrated substantial increases in these variables on the bend. More inward impulse during left (39.9 ± 6.5 Ns) than right foot contact (24.7 ± 5.8 Ns) resulted in 1.6° more turning during the left step on the bend. There was a 2.3% decrease in velocity from straight to bend for both steps. The constant limb force hypothesis is not entirely valid for maximal effort sprinting on the bend. Also, the force requirements of bend sprinting are considerably different to straight-line sprinting and are asymmetrical in nature. Overall, bend-specific strength and technique training may improve performance during this portion of 200- and 400-m races.

  2. Ontogeny of aerodynamics in mallards: comparative performance and developmental implications.

    PubMed

    Dial, Terry R; Heers, Ashley M; Tobalske, Bret W

    2012-11-01

    Wing morphology correlates with flight performance and ecology among adult birds, yet the impact of wing development on aerodynamic capacity is not well understood. Recent work using chukar partridge (Alectoris chukar), a precocial flier, indicates that peak coefficients of lift and drag (C(L) and C(D)) and lift-to-drag ratio (C(L):C(D)) increase throughout ontogeny and that these patterns correspond with changes in feather microstructure. To begin to place these results in a comparative context that includes variation in life-history strategy, we used a propeller and force-plate model to study aerodynamic force production across a developmental series of the altricial-flying mallard (Anas platyrhynchos). We observed the same trend in mallards as reported for chukar in that coefficients of vertical (C(V)) and horizontal force (C(H)) and C(V):C(H) ratio increased with age, and that measures of gross-wing morphology (aspect ratio, camber and porosity) in mallards did not account for intraspecific trends in force production. Rather, feather microstructure (feather unfurling, rachis width, feather asymmetry and barbule overlap) all were positively correlated with peak C(V):C(H). Throughout ontogeny, mallard primary feathers became stiffer and less transmissive to air at both macroscale (between individual feathers) and microscale (between barbs/barbules/barbicels) levels. Differences between species were manifest primarily as heterochrony of aerodynamic force development. Chukar wings generated measurable aerodynamic forces early (<8 days), and improved gradually throughout a 100 day ontogenetic period. Mallard wings exhibited delayed aerodynamic force production until just prior to fledging (day 60), and showed dramatic improvement within a condensed 2-week period. These differences in timing may be related to mechanisms of escape used by juveniles, with mallards swimming to safety and chukar flap-running up slopes to take refuge. Future comparative work should test

  3. Ontogeny of aerodynamics in mallards: comparative performance and developmental implications.

    PubMed

    Dial, Terry R; Heers, Ashley M; Tobalske, Bret W

    2012-11-01

    Wing morphology correlates with flight performance and ecology among adult birds, yet the impact of wing development on aerodynamic capacity is not well understood. Recent work using chukar partridge (Alectoris chukar), a precocial flier, indicates that peak coefficients of lift and drag (C(L) and C(D)) and lift-to-drag ratio (C(L):C(D)) increase throughout ontogeny and that these patterns correspond with changes in feather microstructure. To begin to place these results in a comparative context that includes variation in life-history strategy, we used a propeller and force-plate model to study aerodynamic force production across a developmental series of the altricial-flying mallard (Anas platyrhynchos). We observed the same trend in mallards as reported for chukar in that coefficients of vertical (C(V)) and horizontal force (C(H)) and C(V):C(H) ratio increased with age, and that measures of gross-wing morphology (aspect ratio, camber and porosity) in mallards did not account for intraspecific trends in force production. Rather, feather microstructure (feather unfurling, rachis width, feather asymmetry and barbule overlap) all were positively correlated with peak C(V):C(H). Throughout ontogeny, mallard primary feathers became stiffer and less transmissive to air at both macroscale (between individual feathers) and microscale (between barbs/barbules/barbicels) levels. Differences between species were manifest primarily as heterochrony of aerodynamic force development. Chukar wings generated measurable aerodynamic forces early (<8 days), and improved gradually throughout a 100 day ontogenetic period. Mallard wings exhibited delayed aerodynamic force production until just prior to fledging (day 60), and showed dramatic improvement within a condensed 2-week period. These differences in timing may be related to mechanisms of escape used by juveniles, with mallards swimming to safety and chukar flap-running up slopes to take refuge. Future comparative work should test

  4. CFD research, parallel computation and aerodynamic optimization

    NASA Technical Reports Server (NTRS)

    Ryan, James S.

    1995-01-01

    Over five years of research in Computational Fluid Dynamics and its applications are covered in this report. Using CFD as an established tool, aerodynamic optimization on parallel architectures is explored. The objective of this work is to provide better tools to vehicle designers. Submarine design requires accurate force and moment calculations in flow with thick boundary layers and large separated vortices. Low noise production is critical, so flow into the propulsor region must be predicted accurately. The High Speed Civil Transport (HSCT) has been the subject of recent work. This vehicle is to be a passenger vehicle with the capability of cutting overseas flight times by more than half. A successful design must surpass the performance of comparable planes. Fuel economy, other operational costs, environmental impact, and range must all be improved substantially. For all these reasons, improved design tools are required, and these tools must eventually integrate optimization, external aerodynamics, propulsion, structures, heat transfer and other disciplines.

  5. NASP aerodynamics

    NASA Technical Reports Server (NTRS)

    Whitehead, Allen H., Jr.

    1989-01-01

    This paper discusses the critical aerodynamic technologies needed to support the development of a class of aircraft represented by the National Aero-Space Plane (NASP). The air-breathing, single-stage-to-orbit mission presents a severe challenge to all of the aeronautical disciplines and demands an extension of the state-of-the-art in each technology area. While the largest risk areas are probably advanced materials and the development of the scramjet engine, there remains a host of design issues and technology problems in aerodynamics, aerothermodynamics, and propulsion integration. The paper presents an overview of the most significant propulsion integration problems, and defines the most critical fluid flow phenomena that must be evaluated, defined, and predicted for the class of aircraft represented by the Aero-Space Plane.

  6. Aerodynamic Simulation of the MARINTEK Braceless Semisubmersible Wave Tank Tests

    NASA Astrophysics Data System (ADS)

    Stewart, Gordon; Muskulus, Michael

    2016-09-01

    Model scale experiments of floating offshore wind turbines are important for both platform design for the industry as well as numerical model validation for the research community. An important consideration in the wave tank testing of offshore wind turbines are scaling effects, especially the tension between accurate scaling of both hydrodynamic and aerodynamic forces. The recent MARINTEK braceless semisubmersible wave tank experiment utilizes a novel aerodynamic force actuator to decouple the scaling of the aerodynamic forces. This actuator consists of an array of motors that pull on cables to provide aerodynamic forces that are calculated by a blade-element momentum code in real time as the experiment is conducted. This type of system has the advantage of supplying realistically scaled aerodynamic forces that include dynamic forces from platform motion, but does not provide the insights into the accuracy of the aerodynamic models that an actual model-scale rotor could provide. The modeling of this system presents an interesting challenge, as there are two ways to simulate the aerodynamics; either by using the turbulent wind fields as inputs to the aerodynamic model of the design code, or by surpassing the aerodynamic model and using the forces applied to the experimental turbine as direct inputs to the simulation. This paper investigates the best practices of modeling this type of novel aerodynamic actuator using a modified wind turbine simulation tool, and demonstrates that bypassing the dynamic aerodynamics solver of design codes can lead to erroneous results.

  7. Aerodynamics of sports balls

    NASA Technical Reports Server (NTRS)

    Mehta, R. D.

    1985-01-01

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  8. Aerodynamics of sports balls

    NASA Astrophysics Data System (ADS)

    Mehta, R. D.

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  9. Motor equivalence during multi-finger accurate force production

    PubMed Central

    Mattos, Daniela; Schöner, Gregor; Zatsiorsky, Vladimir M.; Latash, Mark L.

    2014-01-01

    We explored stability of multi-finger cyclical accurate force production action by analysis of responses to small perturbations applied to one of the fingers and inter-cycle analysis of variance. Healthy subjects performed two versions of the cyclical task, with and without an explicit target. The “inverse piano” apparatus was used to lift/lower a finger by 1 cm over 0.5 s; the subjects were always instructed to perform the task as accurate as they could at all times. Deviations in the spaces of finger forces and modes (hypothetical commands to individual fingers) were quantified in directions that did not change total force (motor equivalent) and in directions that changed the total force (non-motor equivalent). Motor equivalent deviations started immediately with the perturbation and increased progressively with time. After a sequence of lifting-lowering perturbations leading to the initial conditions, motor equivalent deviations were dominating. These phenomena were less pronounced for analysis performed with respect to the total moment of force with respect to an axis parallel to the forearm/hand. Analysis of inter-cycle variance showed consistently higher variance in a subspace that did not change the total force as compared to the variance that affected total force. We interpret the results as reflections of task-specific stability of the redundant multi-finger system. Large motor equivalent deviations suggest that reactions of the neuromotor system to a perturbation involve large changes of neural commands that do not affect salient performance variables, even during actions with the purpose to correct those salient variables. Consistency of the analyses of motor equivalence and variance analysis provides additional support for the idea of task-specific stability ensured at a neural level. PMID:25344311

  10. Motor equivalence during multi-finger accurate force production.

    PubMed

    Mattos, Daniela; Schöner, Gregor; Zatsiorsky, Vladimir M; Latash, Mark L

    2015-02-01

    We explored stability of multi-finger cyclical accurate force production action by analysis of responses to small perturbations applied to one of the fingers and inter-cycle analysis of variance. Healthy subjects performed two versions of the cyclical task, with and without an explicit target. The "inverse piano" apparatus was used to lift/lower a finger by 1 cm over 0.5 s; the subjects were always instructed to perform the task as accurate as they could at all times. Deviations in the spaces of finger forces and modes (hypothetical commands to individual fingers) were quantified in directions that did not change total force (motor equivalent) and in directions that changed the total force (non-motor equivalent). Motor equivalent deviations started immediately with the perturbation and increased progressively with time. After a sequence of lifting-lowering perturbations leading to the initial conditions, motor equivalent deviations were dominating. These phenomena were less pronounced for analysis performed with respect to the total moment of force with respect to an axis parallel to the forearm/hand. Analysis of inter-cycle variance showed consistently higher variance in a subspace that did not change the total force as compared to the variance that affected total force. We interpret the results as reflections of task-specific stability of the redundant multi-finger system. Large motor equivalent deviations suggest that reactions of the neuromotor system to a perturbation involve large changes in neural commands that do not affect salient performance variables, even during actions with the purpose to correct those salient variables. Consistency of the analyses of motor equivalence and variance analysis provides additional support for the idea of task-specific stability ensured at a neural level. PMID:25344311

  11. Aerodynamic lift effect on satellite orbits

    NASA Technical Reports Server (NTRS)

    Karr, G. R.; Cleland, J. G.; Devries, L. L.

    1975-01-01

    Numerical quadrature is employed to obtain orbit perturbation results from the general perturbation equations. Both aerodynamic lift and drag forces are included in the analysis of the satellite orbit. An exponential atmosphere with and without atmospheric rotation is used. A comparison is made of the perturbations which are caused by atmospheric rotation with those caused by satellite aerodynamic effects. Results indicate that aerodynamic lift effects on the semi-major axis and orbit inclination can be of the same order as the effects of atmosphere rotation depending upon the orientation of the lift vector. The results reveal the importance of including aerodynamic lift effects in orbit perturbation analysis.

  12. Missile Aerodynamics for Ascent and Re-entry

    NASA Technical Reports Server (NTRS)

    Watts, Gaines L.; McCarter, James W.

    2012-01-01

    Aerodynamic force and moment equations are developed for 6-DOF missile simulations of both the ascent phase of flight and a tumbling re-entry. The missile coordinate frame (M frame) and a frame parallel to the M frame were used for formulating the aerodynamic equations. The missile configuration chosen as an example is a cylinder with fixed fins and a nose cone. The equations include both the static aerodynamic coefficients and the aerodynamic damping derivatives. The inclusion of aerodynamic damping is essential for simulating a tumbling re-entry. Appended information provides insight into aerodynamic damping.

  13. Growth cone behavior and production of traction force

    PubMed Central

    1990-01-01

    The growth cone must push its substrate rearward via some traction force in order to propel itself forward. To determine which growth cone behaviors produce traction force, we observed chick sensory growth cones under conditions in which force production was accommodated by movement of obstacles in the environment, namely, neurites of other sensory neurons or glass fibers. The movements of these obstacles occurred via three, different, stereotyped growth cone behaviors: (a) filopodial contractions, (b) smooth rearward movement on the dorsal surface of the growth cone, and (c) interactions with ruffling lamellipodia. More than 70% of the obstacle movements were caused by filopodial contractions in which the obstacle attached at the extreme distal end of a filopodium and moved only as the filopodium changed its extension. Filopodial contractions were characterized by frequent changes of obstacle velocity and direction. Contraction of a single filopodium is estimated to exert 50-90 microdyn of force, which can account for the pull exerted by chick sensory growth cones. Importantly, all five cases of growth cones growing over the top of obstacle neurites (i.e., geometry that mimics the usual growth cone/substrate interaction), were of the filopodial contraction type. Some 25% of obstacle movements occurred by a smooth backward movement along the top surface of growth cones. Both the appearance and rate of movements were similar to that reported for retrograde flow of cortical actin near the dorsal growth cone surface. Although these retrograde flow movements also exerted enough force to account for growth cone pulling, we did not observe such movements on ventral growth cone surfaces. Occasionally obstacles were moved by interaction with ruffling lamellipodia. However, we obtained no evidence for attachment of the obstacles to ruffling lamellipodia or for directed obstacle movements by this mechanism. These data suggest that chick sensory growth cones move forward by

  14. Reentry aerodynamics forces and moments on the engine nozzle of the 146-inch solid rocket booster model 473 tested in MSFC 14 by 14 inch trisonic wind tunnel (SA30F)

    NASA Technical Reports Server (NTRS)

    Johnson, J. D.; Braddock, W. F.

    1975-01-01

    A test of a model of the Space Shuttle Solid Rocket Boosters (SRB's) was performed in a 14 x 14 inch Trisonic Wind Tunnel to determine the aerodynamic forces and moments imposed on the nozzle of the SRB during reentry. The model, with scale dimensions equal to 0.5479 of the actual SRB dimensions, was instrumented with a six-component force balance attached to the model nozzle so that only forces and moments acting on the nozzle were measured. A total of 137 runs (20 deg pitch polars) were performed during this test. The angle of attack ranged from 60 to 185 deg, the Reynolds number from 5.2 million to 7.6 million. The Mach numbers investigated were 1.96, 2.74, and 3.48. Five external protuberances were simulated. The effective roll angle simulated was 180 deg. The effects of three different heat shield configurations were investigated.

  15. Improving the aerodynamics of top fuel dragsters

    SciTech Connect

    Winn, R.C.; Kohlman, D.L.; Kenner, M.T.

    1998-07-01

    The standard drag race is a straight ahead quarter mile race from a standing stop. As engine technology has improved, the speeds attained at the end of the quarter mile have increased. As the speed has increased, the importance of aerodynamic effects on the dragster has also increased. Lift and drag are the two primary aerodynamic effects. Lift is produced vertically downward to increase the normal force on the rear wheels, thereby increasing the ability to transmit energy from the engine through the wheels to the racetrack. Drag is an unwanted aerodynamic effect. Drag is produced by viscous interaction between the dragster and the air, by separation causing profile drag, and as a result of the lift being produced. This paper addresses the mechanisms of lift and drag production by a high speed dragster and proposes some design changes that can decrease the drag while maintaining the necessary negative lift. Preliminary wind tunnel tests on dragster models confirm that reductions in drag can be achieved. The effects of these changes on the elapsed time and final speed are estimated using a computer simulation of a quarter mile drag race. The simulation predicts a decrease in elapsed time of almost 0.1 seconds and an increase in top speed of approximately 10 miles per hour.

  16. In vivo measurement of aerodynamic weight support in freely flying birds

    NASA Astrophysics Data System (ADS)

    Lentink, David; Haselsteiner, Andreas; Ingersoll, Rivers

    2014-11-01

    Birds dynamically change the shape of their wing during the stroke to support their body weight aerodynamically. The wing is partially folded during the upstroke, which suggests that the upstroke of birds might not actively contribute to aerodynamic force production. This hypothesis is supported by the significant mass difference between the large pectoralis muscle that powers the down-stroke and the much smaller supracoracoideus that drives the upstroke. Previous works used indirect or incomplete techniques to measure the total force generated by bird wings ranging from muscle force, airflow, wing surface pressure, to detailed kinematics measurements coupled with bird mass-distribution models to derive net force through second derivatives. We have validated a new method that measures aerodynamic force in vivo time-resolved directly in freely flying birds which can resolve this question. The validation of the method, using independent force measurements on a quadcopter with pulsating thrust, show the aerodynamic force and impulse are measured within 2% accuracy and time-resolved. We demonstrate results for quad-copters and birds of similar weight and size. The method is scalable and can be applied to both engineered and natural flyers across taxa. The first author invented the method, the second and third authors validated the method and present results for quadcopters and birds.

  17. Computational aerodynamics and supercomputers

    NASA Technical Reports Server (NTRS)

    Ballhaus, W. F., Jr.

    1984-01-01

    Some of the progress in computational aerodynamics over the last decade is reviewed. The Numerical Aerodynamic Simulation Program objectives, computational goals, and implementation plans are described.

  18. Rarefied-flow aerodynamics

    NASA Technical Reports Server (NTRS)

    Potter, J. Leith

    1992-01-01

    Means for relatively simple and quick procedures are examined for estimating aerodynamic coefficients of lifting reentry vehicles. The methods developed allow aerospace designers not only to evaluate the aerodynamics of specific shapes but also to optimize shapes under given constraints. The analysis was also studied of the effect of thermomolecular flow on pressures measured by an orifice near the nose of a Space Shuttle Orbiter at altitudes above 75 km. It was shown that pressures corrected for thermomolecular flow effect are in good agreement with values predicted by independent theoretical methods. An incidental product was the insight gained about the free molecular thermal accommodation coefficient applicable under 'real' conditions of high speed flow in the Earth's atmosphere. The results are presented as abstracts of referenced papers. One reference paper is presented in its entirety.

  19. Surgical force detection probe

    NASA Technical Reports Server (NTRS)

    Tcheng, Ping; Roberts, Paul; Scott, Charles; Prass, Richard

    1991-01-01

    The development progress of a precision electro-mechanical instrument which allows the detection and documentation of the forces and moment applied to human tissue during surgery (under actual operation room conditions), is reported. The pen-shaped prototype probe which measures 1/2 inch in diameter and 7 inches in length was fabricated using an aerodynamic balance. The aerodynamic balance, a standard wind tunnel force and moment sensing transducer, measures the forces and the moments transmitted through the surgeon's hand to the human tissue during surgery. The prototype probe which was fabricated as a development tool was tested successfully. The final version of the surgical force detection probe will be designed based on additional laboratory tests in order to establish the full scale loads. It is expected that the final product will require a simplified aerodynamic balance with two or three force components and one moment component with lighter full scale loads. A signal conditioner was fabricated to process and display the outputs from the prototype probe. This unit will be interfaced with a PC-based data system to provide automatic data acquisition, data processing, and graphics display. The expected overall accuracy of the probe is better than one percent full scale.

  20. Rotor/body aerodynamic interactions

    NASA Technical Reports Server (NTRS)

    Betzina, M. D.; Smith, C. A.; Shinoda, P.

    1983-01-01

    A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in velocity, thrust, tip-path-plane angle of attack, body angle of attack, rotor/body position, and body geometry were determined. The results show that the body longitudinal aerodynamic characteristics are significantly affected by the presence of a rotor and hub, and that the hub interference may be a major part of such interaction. The effects of the body on the rotor performance are presented.

  1. Rotor/body aerodynamic interactions

    NASA Technical Reports Server (NTRS)

    Betzina, M. D.; Smith, C. A.; Shinoda, P.

    1985-01-01

    A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in velocity, thrust, tip-path-plane angle of attack, body angle of attack, rotor/body position, and body geometry were determined. The results show that the body longitudinal aerodynamic characteristics are significantly affected by the presence of a rotor and hub, and that the hub interference may be a major part of such interaction. The effects of the body on the rotor performance are presented.

  2. TAD- THEORETICAL AERODYNAMICS PROGRAM

    NASA Technical Reports Server (NTRS)

    Barrowman, J.

    1994-01-01

    This theoretical aerodynamics program, TAD, was developed to predict the aerodynamic characteristics of vehicles with sounding rocket configurations. These slender, axisymmetric finned vehicle configurations have a wide range of aeronautical applications from rockets to high speed armament. Over a given range of Mach numbers, TAD will compute the normal force coefficient derivative, the center-of-pressure, the roll forcing moment coefficient derivative, the roll damping moment coefficient derivative, and the pitch damping moment coefficient derivative of a sounding rocket configured vehicle. The vehicle may consist of a sharp pointed nose of cone or tangent ogive shape, up to nine other body divisions of conical shoulder, conical boattail, or circular cylinder shape, and fins of trapezoid planform shape with constant cross section and either three or four fins per fin set. The characteristics computed by TAD have been shown to be accurate to within ten percent of experimental data in the supersonic region. The TAD program calculates the characteristics of separate portions of the vehicle, calculates the interference between separate portions of the vehicle, and then combines the results to form a total vehicle solution. Also, TAD can be used to calculate the characteristics of the body or fins separately as an aid in the design process. Input to the TAD program consists of simple descriptions of the body and fin geometries and the Mach range of interest. Output includes the aerodynamic characteristics of the total vehicle, or user-selected portions, at specified points over the mach range. The TAD program is written in FORTRAN IV for batch execution and has been implemented on an IBM 360 computer with a central memory requirement of approximately 123K of 8 bit bytes. The TAD program was originally developed in 1967 and last updated in 1972.

  3. Prediction of forces and moments for flight vehicle control effectors. Part 2: An analysis of delta wing aerodynamic control effectiveness in ground effect

    NASA Technical Reports Server (NTRS)

    Maughmer, Mark D.; Ozoroski, L.; Ozoroski, T.; Straussfogel, D.

    1990-01-01

    Many types of hypersonic aircraft configurations are currently being studied for feasibility of future development. Since the control of the hypersonic configurations throughout the speed range has a major impact on acceptable designs, it must be considered in the conceptual design stage. Here, an investigation of the aerodynamic control effectiveness of highly swept delta planforms operating in ground effect is presented. A vortex-lattice computer program incorporating a free wake is developed as a tool to calculate aerodynamic stability and control derivatives. Data generated using this program are compared to experimental data and to data from other vortex-lattice programs. Results show that an elevon deflection produces greater increments in C sub L and C sub M in ground effect than the same deflection produces out of ground effect and that the free wake is indeed necessary for good predictions near the ground.

  4. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  5. Embryo mechanics: balancing force production with elastic resistance during morphogenesis.

    PubMed

    Davidson, Lance A

    2011-01-01

    Morphogenesis requires the spatial and temporal control of embryo mechanics, including force production and mechanical resistance to those forces, to coordinate tissue deformation and large-scale movements. Thus, biomechanical processes play a key role in directly shaping the embryo. Additional roles for embryo mechanics during development may include the patterning of positional information and to provide feedback to ensure the success of morphogenetic movements in shaping the larval body and organs. To understand the multiple roles of mechanics during development requires familiarity with engineering principles of the mechanics of structures, the viscoelastic properties of biomaterials, and the integration of force and stress within embryonic structures as morphogenesis progresses. In this chapter, we review the basic engineering principles of biomechanics as they relate to morphogenesis, introduce methods for quantifying embryo mechanics and the limitations of these methods, and outline a formalism for investigating the role of embryo mechanics in birth defects. We encourage the nascent field of embryo mechanics to adopt standard engineering terms and test methods so that studies of diverse organisms can be compared and universal biomechanical principles can be revealed.

  6. 76 FR 24025 - Information Collection; Prohibition on Acquisition of Products Produced by Forced or Indentured...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-29

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  7. 76 FR 42709 - Submission for OMB Review; Prohibition on Acquisition of Products Produced by Forced or...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-19

    ...; Prohibition on Acquisition of Products Produced by Forced or Indentured Child Labor AGENCY: Department of... acquisition of products produced by forced or indentured child labor. DATES: Submit comments on or before... on Acquisition of Products Produced by Forced or Indentured Child Labor, by any of the...

  8. A CFD-informed quasi-steady model of flapping wing aerodynamics

    PubMed Central

    Nakata, Toshiyuki; Liu, Hao; Bomphrey, Richard J.

    2016-01-01

    Aerodynamic performance and agility during flapping flight are determined by the combination of wing shape and kinematics. The degree of morphological and kinematic optimisation is unknown and depends upon a large parameter space. Aimed at providing an accurate and computationally inexpensive modelling tool for flapping-wing aerodynamics, we propose a novel CFD (computational fluid dynamics)-informed quasi-steady model (CIQSM), which assumes that the aerodynamic forces on a flapping wing can be decomposed into the quasi-steady forces and parameterised based on CFD results. Using least-squares fitting, we determine a set of proportional coefficients for the quasi-steady model relating wing kinematics to instantaneous aerodynamic force and torque; we calculate power with the product of quasi-steady torques and angular velocity. With the quasi-steady model fully and independently parameterised on the basis of high-fidelity CFD modelling, it is capable of predicting flapping-wing aerodynamic forces and power more accurately than the conventional blade element model (BEM) does. The improvement can be attributed to, for instance, taking into account the effects of the induced downwash and the wing tip vortex on the force generation and power consumption. Our model is validated by comparing the aerodynamics of a CFD model and the present quasi-steady model using the example case of a hovering hawkmoth. It demonstrates that the CIQSM outperforms the conventional BEM while remaining computationally cheap, and hence can be an effective tool for revealing the mechanisms of optimization and control of kinematics and morphology in flapping-wing flight for both bio-flyers and unmanned air systems. PMID:27346891

  9. 77 FR 9267 - Child Labor, Forced Labor, and Forced or Indentured Child Labor in the Production of Goods in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-16

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Child Labor, Forced Labor, and Forced or Indentured Child Labor in the Production of Goods in Foreign Countries and Efforts by Certain Countries To Eliminate the Worst Forms of Child Labor AGENCY: The Bureau...

  10. Modeling of aerodynamic interaction between vocal folds and vocal tract during production of a vowel-voiceless plosive-vowel sequence.

    PubMed

    Delebecque, Louis; Pelorson, Xavier; Beautemps, Denis

    2016-01-01

    The context of this study is the physical modeling of speech production. The objective is, by using a mechanical replica of the vocal tract, to test quantitatively an aerodynamic model of the interaction between the vocal folds and the vocal tract during the production of a vowel-voiceless plosive-vowel sequence. The first step is to realize acoustic and aerodynamic measurements on a speaker during the production of an /apa/ sequence. The aperture and width of the lips are also derived from a high-speed video recording of the subject's face. Theoretical models to describe the flow through the lips and the effect of an expansion of the supraglottal cavity are proposed and validated by comparison with measurements made using a self-oscillating replica of the phonatory system. Finally, using these models, numerical simulations of an /apa/ sequence are performed using the measured lip parameters as the only time-varying input parameters. The results of these simulations suggest that the realization of an occlusion of the vocal tract produces a passive increase in glottal area associated with a voice offset and that the expansion of the supraglottal cavity is responsible for the extension of the phonation up to 40 ms after closure of the lips.

  11. Kinematics and aerodynamics of avian upstrokes during slow flight.

    PubMed

    Crandell, Kristen E; Tobalske, Bret W

    2015-08-01

    Slow flight is extremely energetically costly per unit time, yet highly important for takeoff and survival. However, at slow speeds it is presently thought that most birds do not produce beneficial aerodynamic forces during the entire wingbeat: instead they fold or flex their wings during upstroke, prompting the long-standing prediction that the upstroke produces trivial forces. There is increasing evidence that the upstroke contributes to force production, but the aerodynamic and kinematic mechanisms remain unknown. Here, we examined the wingbeat cycle of two species: the diamond dove (Geopelia cuneata) and zebra finch (Taeniopygia guttata), which exhibit different upstroke styles - a wingtip-reversal and flexed-wing upstroke, respectively. We used a combination of particle image velocimetry and near-wake streamline measures alongside detailed 3D kinematics. We show that during the middle of the wingtip-reversal upstroke, the hand-wing has a high angular velocity (15.3±0.8 deg ms(-1)) and translational speed (8.4±0.6 m s(-1)). The flexed-wing upstroke, in contrast, has low wingtip speed during mid-upstroke. Instead, later in the stroke cycle, during the transition from upstroke to downstroke, it exhibits higher angular velocities (45.5±13.8 deg ms(-1)) and translational speeds (11.0±1.9 m s(-1)). Aerodynamically, the wingtip-reversal upstroke imparts momentum to the wake, with entrained air shed backward (visible as circulation of 14.4±0.09 m(2) s(-1)). In contrast, the flexed-wing upstroke imparts minimal momentum. Clap and peel in the dove enhances the time course for circulation production on the wings, and provides new evidence of convergent evolution on time-varying aerodynamic mechanisms during flapping in insects and birds. PMID:26089528

  12. Kinematics and aerodynamics of avian upstrokes during slow flight.

    PubMed

    Crandell, Kristen E; Tobalske, Bret W

    2015-08-01

    Slow flight is extremely energetically costly per unit time, yet highly important for takeoff and survival. However, at slow speeds it is presently thought that most birds do not produce beneficial aerodynamic forces during the entire wingbeat: instead they fold or flex their wings during upstroke, prompting the long-standing prediction that the upstroke produces trivial forces. There is increasing evidence that the upstroke contributes to force production, but the aerodynamic and kinematic mechanisms remain unknown. Here, we examined the wingbeat cycle of two species: the diamond dove (Geopelia cuneata) and zebra finch (Taeniopygia guttata), which exhibit different upstroke styles - a wingtip-reversal and flexed-wing upstroke, respectively. We used a combination of particle image velocimetry and near-wake streamline measures alongside detailed 3D kinematics. We show that during the middle of the wingtip-reversal upstroke, the hand-wing has a high angular velocity (15.3±0.8 deg ms(-1)) and translational speed (8.4±0.6 m s(-1)). The flexed-wing upstroke, in contrast, has low wingtip speed during mid-upstroke. Instead, later in the stroke cycle, during the transition from upstroke to downstroke, it exhibits higher angular velocities (45.5±13.8 deg ms(-1)) and translational speeds (11.0±1.9 m s(-1)). Aerodynamically, the wingtip-reversal upstroke imparts momentum to the wake, with entrained air shed backward (visible as circulation of 14.4±0.09 m(2) s(-1)). In contrast, the flexed-wing upstroke imparts minimal momentum. Clap and peel in the dove enhances the time course for circulation production on the wings, and provides new evidence of convergent evolution on time-varying aerodynamic mechanisms during flapping in insects and birds.

  13. Aerodynamic challenges of ALT

    NASA Technical Reports Server (NTRS)

    Hooks, I.; Homan, D.; Romere, P. O.

    1985-01-01

    The approach and landing test (ALT) of the Space Shuttle Orbiter presented a number of unique challenges in the area of aerodynamics. The purpose of the ALT program was both to confirm the use of the Boeing 747 as a transport vehicle for ferrying the Orbiter across the country and to demonstrate the flight characteristics of the Orbiter in its approach and landing phase. Concerns for structural fatigue and performance dictated a tailcone be attached to the Orbiter for ferry and for the initial landing tests. The Orbiter with a tailcone attached presented additional challenges to the normal aft sting concept of wind tunnel testing. The landing tests required that the Orbiter be separated from the 747 at approximately 20,000 feet using aerodynamic forces to fly the vehicles apart. The concept required a complex test program to determine the relative effects of the two vehicles on each other. Also of concern, and tested, was the vortex wake created by the 747 and the means for the Orbiter to avoid it following separation.

  14. Distributed Aerodynamic Sensing and Processing Toolbox

    NASA Technical Reports Server (NTRS)

    Brenner, Martin; Jutte, Christine; Mangalam, Arun

    2011-01-01

    A Distributed Aerodynamic Sensing and Processing (DASP) toolbox was designed and fabricated for flight test applications with an Aerostructures Test Wing (ATW) mounted under the fuselage of an F-15B on the Flight Test Fixture (FTF). DASP monitors and processes the aerodynamics with the structural dynamics using nonintrusive, surface-mounted, hot-film sensing. This aerodynamic measurement tool benefits programs devoted to static/dynamic load alleviation, body freedom flutter suppression, buffet control, improvement of aerodynamic efficiency through cruise control, supersonic wave drag reduction through shock control, etc. This DASP toolbox measures local and global unsteady aerodynamic load distribution with distributed sensing. It determines correlation between aerodynamic observables (aero forces) and structural dynamics, and allows control authority increase through aeroelastic shaping and active flow control. It offers improvements in flutter suppression and, in particular, body freedom flutter suppression, as well as aerodynamic performance of wings for increased range/endurance of manned/ unmanned flight vehicles. Other improvements include inlet performance with closed-loop active flow control, and development and validation of advanced analytical and computational tools for unsteady aerodynamics.

  15. Freight Wing Trailer Aerodynamics

    SciTech Connect

    Graham, Sean; Bigatel, Patrick

    2004-10-17

    Freight Wing Incorporated utilized the opportunity presented by this DOE category one Inventions and Innovations grant to successfully research, develop, test, patent, market, and sell innovative fuel and emissions saving aerodynamic attachments for the trucking industry. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck's fuel consumption. However, significant design challenges have prevented past concepts from meeting industry needs. Market research early in this project revealed the demands of truck fleet operators regarding aerodynamic attachments. Products must not only save fuel, but cannot interfere with the operation of the truck, require significant maintenance, add significant weight, and must be extremely durable. Furthermore, SAE/TMC J1321 tests performed by a respected independent laboratory are necessary for large fleets to even consider purchase. Freight Wing used this information to create a system of three practical aerodynamic attachments for the front, rear and undercarriage of standard semi trailers. SAE/TMC J1321 Type II tests preformed by the Transportation Research Center (TRC) demonstrated a 7% improvement to fuel economy with all three products. If Freight Wing is successful in its continued efforts to gain market penetration, the energy and environmental savings would be considerable. Each truck outfitted saves approximately 1,100 gallons of fuel every 100,000 miles, which prevents over 12 tons of CO2 from entering the atmosphere. If all applicable trailers used the technology, the country could save approximately 1.8 billion gallons of diesel fuel, 18 million tons of emissions and 3.6 billion dollars annually.

  16. The Adaptive Range of 1/f Isometric Force Production

    ERIC Educational Resources Information Center

    Sosnoff, Jacob J.; Valantine, Andrew D.; Newell, Karl M.

    2009-01-01

    The adaptive range of 1/f dynamics in isometric force output was investigated. Participants produced isometric force to targets with predictable demands (constant and sinusoidal) and 1/f noise waveforms (white, pink, brown, and black) that also varied in the frequency bandwidth represented in the force signal (0-4 Hz, 0-8 Hz, and 0-12 Hz). The…

  17. A program to compute three-dimensional subsonic unsteady aerodynamic characteristics using the doublet lattic method, L216 (DUBFLX). Volume 1: Engineering and usage

    NASA Technical Reports Server (NTRS)

    Richard, M.; Harrison, B. A.

    1979-01-01

    The program input presented consists of configuration geometry, aerodynamic parameters, and modal data; output includes element geometry, pressure difference distributions, integrated aerodynamic coefficients, stability derivatives, generalized aerodynamic forces, and aerodynamic influence coefficient matrices. Optionally, modal data may be input on magnetic file (tape or disk), and certain geometric and aerodynamic output may be saved for subsequent use.

  18. NASA aerodynamics program

    NASA Technical Reports Server (NTRS)

    Williams, Louis J.; Hessenius, Kristin A.; Corsiglia, Victor R.; Hicks, Gary; Richardson, Pamela F.; Unger, George; Neumann, Benjamin; Moss, Jim

    1992-01-01

    The annual accomplishments is reviewed for the Aerodynamics Division during FY 1991. The program includes both fundamental and applied research directed at the full spectrum of aerospace vehicles, from rotorcraft to planetary entry probes. A comprehensive review is presented of the following aerodynamics elements: computational methods and applications; CFD validation; transition and turbulence physics; numerical aerodynamic simulation; test techniques and instrumentation; configuration aerodynamics; aeroacoustics; aerothermodynamics; hypersonics; subsonics; fighter/attack aircraft and rotorcraft.

  19. Fourier functional analysis for unsteady aerodynamic modeling

    NASA Technical Reports Server (NTRS)

    Lan, C. Edward; Chin, Suei

    1991-01-01

    A method based on Fourier analysis is developed to analyze the force and moment data obtained in large amplitude forced oscillation tests at high angles of attack. The aerodynamic models for normal force, lift, drag, and pitching moment coefficients are built up from a set of aerodynamic responses to harmonic motions at different frequencies. Based on the aerodynamic models of harmonic data, the indicial responses are formed. The final expressions for the models involve time integrals of the indicial type advocated by Tobak and Schiff. Results from linear two- and three-dimensional unsteady aerodynamic theories as well as test data for a 70-degree delta wing are used to verify the models. It is shown that the present modeling method is accurate in producing the aerodynamic responses to harmonic motions and the ramp type motions. The model also produces correct trend for a 70-degree delta wing in harmonic motion with different mean angles-of-attack. However, the current model cannot be used to extrapolate data to higher angles-of-attack than that of the harmonic motions which form the aerodynamic model. For linear ramp motions, a special method is used to calculate the corresponding frequency and phase angle at a given time. The calculated results from modeling show a higher lift peak for linear ramp motion than for harmonic ramp motion. The current model also shows reasonably good results for the lift responses at different angles of attack.

  20. Recent advances in computational aerodynamics

    NASA Astrophysics Data System (ADS)

    Agarwal, Ramesh K.; Desse, Jerry E.

    1991-04-01

    The current state of the art in computational aerodynamics is described. Recent advances in the discretization of surface geometry, grid generation, and flow simulation algorithms have led to flowfield predictions for increasingly complex and realistic configurations. As a result, computational aerodynamics is emerging as a crucial enabling technology for the development and design of flight vehicles. Examples illustrating the current capability for the prediction of aircraft, launch vehicle and helicopter flowfields are presented. Unfortunately, accurate modeling of turbulence remains a major difficulty in the analysis of viscosity-dominated flows. In the future inverse design methods, multidisciplinary design optimization methods, artificial intelligence technology and massively parallel computer technology will be incorporated into computational aerodynamics, opening up greater opportunities for improved product design at substantially reduced costs.

  1. NASA aerodynamics program

    NASA Technical Reports Server (NTRS)

    Holmes, Bruce J.; Schairer, Edward; Hicks, Gary; Wander, Stephen; Blankson, Isiaiah; Rose, Raymond; Olson, Lawrence; Unger, George

    1990-01-01

    Presented here is a comprehensive review of the following aerodynamics elements: computational methods and applications, computational fluid dynamics (CFD) validation, transition and turbulence physics, numerical aerodynamic simulation, drag reduction, test techniques and instrumentation, configuration aerodynamics, aeroacoustics, aerothermodynamics, hypersonics, subsonic transport/commuter aviation, fighter/attack aircraft and rotorcraft.

  2. Physiological, aerodynamic and geometric constraints of flapping account for bird gaits, and bounding and flap-gliding flight strategies.

    PubMed

    Usherwood, James Richard

    2016-11-01

    Aerodynamically economical flight is steady and level. The high-amplitude flapping and bounding flight style of many small birds departs considerably from any aerodynamic or purely mechanical optimum. Further, many large birds adopt a flap-glide flight style in cruising flight which is not consistent with purely aerodynamic economy. Here, an account is made for such strategies by noting a well-described, general, physiological cost parameter of muscle: the cost of activation. Small birds, with brief downstrokes, experience disproportionately high costs due to muscle activation for power during contraction as opposed to work. Bounding flight may be an adaptation to modulate mean aerodynamic force production in response to (1) physiological pressure to extend the duration of downstroke to reduce power demands during contraction; (2) the prevention of a low-speed downstroke due to the geometric constraints of producing thrust; (3) an aerodynamic cost to flapping with very low lift coefficients. In contrast, flap-gliding birds, which tend to be larger, adopt a strategy that reduces the physiological cost of work due both to activation and contraction efficiency. Flap-gliding allows, despite constraints to modulation of aerodynamic force lever-arm, (1) adoption of moderately large wing-stroke amplitudes to achieve suitable muscle strains, thereby reducing the activation costs for work; (2) reasonably quick downstrokes, enabling muscle contraction at efficient velocities, while being (3) prevented from very slow weight-supporting upstrokes due to the cost of performing 'negative' muscle work.

  3. Physiological, aerodynamic and geometric constraints of flapping account for bird gaits, and bounding and flap-gliding flight strategies.

    PubMed

    Usherwood, James Richard

    2016-11-01

    Aerodynamically economical flight is steady and level. The high-amplitude flapping and bounding flight style of many small birds departs considerably from any aerodynamic or purely mechanical optimum. Further, many large birds adopt a flap-glide flight style in cruising flight which is not consistent with purely aerodynamic economy. Here, an account is made for such strategies by noting a well-described, general, physiological cost parameter of muscle: the cost of activation. Small birds, with brief downstrokes, experience disproportionately high costs due to muscle activation for power during contraction as opposed to work. Bounding flight may be an adaptation to modulate mean aerodynamic force production in response to (1) physiological pressure to extend the duration of downstroke to reduce power demands during contraction; (2) the prevention of a low-speed downstroke due to the geometric constraints of producing thrust; (3) an aerodynamic cost to flapping with very low lift coefficients. In contrast, flap-gliding birds, which tend to be larger, adopt a strategy that reduces the physiological cost of work due both to activation and contraction efficiency. Flap-gliding allows, despite constraints to modulation of aerodynamic force lever-arm, (1) adoption of moderately large wing-stroke amplitudes to achieve suitable muscle strains, thereby reducing the activation costs for work; (2) reasonably quick downstrokes, enabling muscle contraction at efficient velocities, while being (3) prevented from very slow weight-supporting upstrokes due to the cost of performing 'negative' muscle work. PMID:27418386

  4. Molecular model for force production and transmission during vertebrate gastrulation.

    PubMed

    Pfister, Katherine; Shook, David R; Chang, Chenbei; Keller, Ray; Skoglund, Paul

    2016-02-15

    Vertebrate embryos undergo dramatic shape changes at gastrulation that require locally produced and anisotropically applied forces, yet how these forces are produced and transmitted across tissues remains unclear. We show that depletion of myosin regulatory light chain (RLC) levels in the embryo blocks force generation at gastrulation through two distinct mechanisms: destabilizing the myosin II (MII) hexameric complex and inhibiting MII contractility. Molecular dissection of these two mechanisms demonstrates that normal convergence force generation requires MII contractility and we identify a set of molecular phenotypes correlated with both this failure of convergence force generation in explants and of blastopore closure in whole embryos. These include reduced rates of actin movement, alterations in C-cadherin dynamics and a reduction in the number of polarized lamellipodia on intercalating cells. By examining the spatial relationship between C-cadherin and actomyosin we also find evidence for formation of transcellular linear arrays incorporating these proteins that could transmit mediolaterally oriented tensional forces. These data combine to suggest a multistep model to explain how cell intercalation can occur against a force gradient to generate axial extension forces. First, polarized lamellipodia extend mediolaterally and make new C-cadherin-based contacts with neighboring mesodermal cell bodies. Second, lamellipodial flow of actin coalesces into a tension-bearing, MII-contractility-dependent node-and-cable actin network in the cell body cortex. And third, this actomyosin network contracts to generate mediolateral convergence forces in the context of these transcellular arrays.

  5. Foot force production and asymmetries in elite rowers.

    PubMed

    Buckeridge, Erica M; Bull, Anthony M J; McGregor, Alison H

    2014-03-01

    The rowing stroke is a leg-driven action, in which forces developed by the lower limbs provide a large proportion of power delivered to the oars. In terms of both performance and injury, it is important to initiate each stroke with powerful and symmetrical loading of the foot stretchers. The aims of this study were to assess the reliability of foot force measured by footplates developed for the Concept2 indoor ergometer and to examine the magnitude and symmetry of bilateral foot forces in different groups of rowers. Five heavyweight female scullers, six heavyweight female sweep rowers, and six lightweight male (LWM) rowers performed an incremental step test on the Concept2 ergometer. Vertical, horizontal, and resultant forces were recorded bilaterally, and asymmetries were quantified using the absolute symmetry index. Foot force was measured with high consistency (coefficient of multiple determination > 0.976 +/- 0.010). Relative resultant, vertical, and horizontal forces were largest in LWM rowers, whilst average foot forces significantly increased across stroke rates for all three groups of rowers. Asymmetries ranged from 5.3% for average resultant force to 28.9% for timing of peak vertical force. Asymmetries were not sensitive to stroke rate or rowing group, however, large inter-subject variability in asymmetries was evident.

  6. Bifurcations in unsteady aerodynamics

    NASA Technical Reports Server (NTRS)

    Tobak, M.; Unal, A.

    1986-01-01

    Nonlinear algebraic functional expansions are used to create a form for the unsteady aerodynamic response that is consistent with solutions of the time dependent Navier-Stokes equations. An enumeration of means of invalidating Frechet differentiability of the aerodynamic response, one of which is aerodynamic bifurcation, is proposed as a way of classifying steady and unsteady aerodynamic phenomena that are important in flight dynamics applications. Accomodating bifurcation phenomena involving time dependent equilibrium states within a mathematical model of the aerodynamic response raises an issue of memory effects that becomes more important with each successive bifurcation.

  7. Aerodynamics model for a generic ASTOVL lift-fan aircraft

    NASA Technical Reports Server (NTRS)

    Birckelbaw, Lourdes G.; Mcneil, Walter E.; Wardwell, Douglas A.

    1995-01-01

    This report describes the aerodynamics model used in a simulation model of an advanced short takeoff and vertical landing (ASTOVL) lift-fan fighter aircraft. The simulation model was developed for use in piloted evaluations of transition and hover flight regimes, so that only low speed (M approximately 0.2) aerodynamics are included in the mathematical model. The aerodynamic model includes the power-off aerodynamic forces and moments and the propulsion system induced aerodynamic effects, including ground effects. The power-off aerodynamics data were generated using the U.S. Air Force Stability and Control Digital DATCOM program and a NASA Ames in-house graphics program called VORVIEW which allows the user to easily analyze arbitrary conceptual aircraft configurations using the VORLAX program. The jet-induced data were generated using the prediction methods of R. E. Kuhn et al., as referenced in this report.

  8. Particle Production by Tidal Forces, and the Energy - Tensor

    NASA Astrophysics Data System (ADS)

    Massacand, Christophe Maurice Jean-Baptiste

    The quantum production of spinless particles, < n_{k}(t)>, and of energy-momentum-stress, < T^{{a}{b}}(P) >, by the tidal forces of classical curved space-time are investigated in this thesis. In a first part we consider the test case of 1+1 dimensions. Our computations are finite step by step, the predicted evolution of the energy-momentum tensor < T^{ a b} > and of the spectral energy density e_{k}< n_{k }> are consistent with each other throughout curved space-time, < T^ { a b}> is covariantly conserved and has the standard trace anomaly R/24 pi for massless particles. The two chiralities, right-goers versus left-goers, are decoupled, the total < T^{{a} {b}}> is the sum of the chiral parts. We apply our methods to four problems: (1) The Rindler problem. (2) An inhomogeneous patch of curvature produces a burst of energy-momentum and of particles. (3) We compute the quantum production of energy density and pressure for a quantum field in external Friedmann-Robertson -Walker space-times in 1+1 dimensions. (4) We consider the gravitational field of a collapsing shell of classical matter in 3+1 dimensions, and we compute the production of Hawking radiation everywhere inside a linear wave guide in the radial direction. In a second part, we compute the energy density and pressures from a quantum scalar field propagating in the external field of a (3+1)-dimensional, spherically symmetric, static geometry with flat spatial sections. We consider only the (l = 0)-sector of the scalar field. The initial state of the quantum field is the gauge invariant vacuum on one of these hypersurface. Our computations are finite step by step. For the pressures we use the covariant conservation of T^{mu nu} and its four-dimensional trace. We apply our results to the case of the gravitational potential due to an homogeneous spherical body. At late times, i.e. when all switch-on effects are far away from the body, the results are that a static cloud of energy and pressure is formed inside

  9. Velocity associated characteristics of force production in college weight lifters

    PubMed Central

    Kanehisa, H.; Fukunaga, T.

    1999-01-01

    OBJECTIVE: To determine velocity specific isokinetic forces and cross sectional areas of reciprocal muscle groups in Olympic weight lifters. METHODS: The cross sectional area of the flexor or extensor muscles of the elbow or knee joint was determined by a B-mode ultrasonic apparatus in 34 college weight lifters and 31 untrained male subjects matched for age. Maximum voluntary force produced in the flexion and extension of the elbow and knee joints was measured on an isokinetic dynamometer at 60, 180, and 300 degrees/s. RESULTS: The average cross sectional area was 31-65% higher, and the force was 19-62% higher in weight lifters than in the untrained subjects. The ratio of force to cross sectional area was the same in both groups. The weight lifters showed a lower velocity associated decline in force than untrained subjects in the elbow and knee flexors but not in the extensors. CONCLUSIONS: These results indicate that for muscle contractions with velocities between 60 degrees/s and 300 degrees/s the difference in isokinetic force between weight lifters and untrained subjects can be primarily attributed to the difference in the muscle cross sectional area. However, the lower velocity associated decline in force implies that weight lifters may have a higher force per cross sectional area than untrained subjects at velocities above 300 degrees/s. 




 PMID:10205693

  10. Aerodynamic analysis of a tumbling American football

    NASA Astrophysics Data System (ADS)

    Hare, Daniel Edmundson

    In this study, the aerodynamic effects on an American football are characterized, especially in a tumbling, or end-over-end, motion as seen in a typical kickoff or field goal attempt. The objective of this study is to establish aerodynamic coefficients for the dynamic motion of a tumbling American football. A subsonic wind tunnel was used to recreate a range of air velocities that, when coupled with rotation rates and differing laces orientations, would provide a test bed for aerodynamic drag, side, and lift coefficient analysis. Test results quantify effect of back-spin and top-spin on lift force. Results show that the presence of laces imposes a side force in the opposite direction of the laces orientation. A secondary system was installed to visualize air flow around the tumbling ball and record high-speed video of wake patterns, as a qualitative check of measured force directions.

  11. Functional muscle synergies constrain force production during postural tasks

    PubMed Central

    McKay, J. Lucas; Ting, Lena H.

    2015-01-01

    We recently demonstrated that a set of five functional muscle synergies were sufficient to characterize both hindlimb muscle activity and active forces during automatic postural responses in cats standing at multiple postural configurations. This characterization depended critically upon the assumption that the endpoint force vector (synergy force vector) produced by the activation of each muscle synergy rotated with the limb axis as the hindlimb posture varied in the sagittal plane. Here, we used a detailed, 3D static model of the hindlimb to confirm that this assumption is biomechanically plausible: as we varied the model posture, simulated synergy force vectors rotated monotonically with the limb axis in the parasagittal plane (r2 = 0.94 ± 0.08). We then tested whether a neural strategy of using these five functional muscle synergies provides the same force-generating capability as controlling each of the 31 muscles individually. We compared feasible force sets (FFS) from the model with and without a muscle synergy organization. FFS volumes were significantly reduced with the muscle synergy organization (F = 1556.01, p ≪ 0.01), and as posture varied, the synergy-limited FFSs changed in shape, consistent with changes in experimentally-measured active forces. In contrast, nominal FFS shapes were invariant with posture, reinforcing prior findings that postural forces cannot be predicted by hindlimb biomechanics alone. We propose that an internal model for postural force generation may coordinate functional muscle synergies that are invariant in intrinsic limb coordinates, and this reduced-dimension control scheme reduces the set of forces available for postural control. PMID:17980370

  12. Characterization of Flapping Wing Aerodynamics and Flight Dynamics Analysis using Computational Methods

    NASA Astrophysics Data System (ADS)

    Rege, Alok Ashok

    Insect flight comes with a lot of intricacies that cannot be explained by conventional aerodynamics. Even with their small-size, insects have the ability to generate the required aerodynamic forces using high frequency flapping motion of their wings to perform different maneuvers. The maneuverability obtained by these flyers using flapping motion belies the classical aerodynamics theory and calls for a new approach to study this highly unsteady aerodynamics. Research is on to find new ways to realize the flight capabilities of these insects and engineer a micro-flyer which would have various applications, ranging from autonomous pollination of crop fields and oil & gas exploration to area surveillance and detection & rescue missions. In this research, a parametric study of flapping trajectories is performed using a two-dimensional wing to identify the factors that affect the force production. These factors are then non-dimensionalized and used in a design of experiments set-up to conduct sensitivity analysis. A procedure to determine an aerodynamic model comprising cycle-averaged force coefficients is described. This aerodynamic model is then used in a nonlinear dynamics framework to perform flight dynamics analysis using a micro-flyer with model properties based on Drosophila. Stability analysis is conducted to determine different steady state flight conditions that could achieved by the micro-flyer with the given model properties. The effect of scaling the mass properties is discussed. An LQR design is used for closed-loop control. Open and closed-loop simulations are performed. The results show that nonlinear dynamics framework can be used to determine values for model properties of a micro-flyer that would enable it to perform different flight maneuvers.

  13. Influence of Emotion on the Control of Low-Level Force Production

    ERIC Educational Resources Information Center

    Naugle, Kelly M.; Coombes, Stephen A.; Cauraugh, James H.; Janelle, Christopher M.

    2012-01-01

    The accuracy and variability of a sustained low-level force contraction (2% of maximum voluntary contraction) was measured while participants viewed unpleasant, pleasant, and neutral images during a feedback occluded force control task. Exposure to pleasant and unpleasant images led to a relative increase in force production but did not alter the…

  14. Motor control hierarchy in joint action that involves bimanual force production

    PubMed Central

    Masumoto, Junya

    2015-01-01

    The concept of hierarchical motor control has been viewed as a means of progressively decreasing the number of variables manipulated by each higher control level. We tested the hypothesis that turning an individual bimanual force-production task into a joint (two-participant) force-production task would lead to positive correlation between forces produced by the two hands of the individual participant (symmetric strategy) to enable negative correlation between forces produced by two participants (complementary strategy). The present study consisted of individual and joint tasks that involved both unimanual and bimanual conditions. In the joint task, 10 pairs of participants produced periodic isometric forces, such that the sum of forces that they produced matched a target force cycling between 5% and 10% of maximum voluntary contraction at 1 Hz. In the individual task, individuals attempted to match the same target force. In the joint bimanual condition, the two hands of each participant adopted a symmetric strategy of force, whereas the two participants adopted a complementary strategy of force, highlighting that the bimanual action behaved as a low level of a hierarchy, whereas the joint action behaved as an upper level. The complementary force production was greater interpersonally than intrapersonally. However, whereas the coherence was highest at 1 Hz in all conditions, the frequency synchrony was stronger intrapersonally than interpersonally. Moreover, whereas the bimanual action exhibited a smaller error and variability of force than the unimanual action, the joint action exhibited a less-variable interval and force than the individual action. PMID:25904710

  15. Measurement of Aerodynamic Forces for Various Mean Angles of Attack on an Airfoil Oscillating in Pitch and on Two Finite-span Wings Oscillating in Bending with Emphasis on Damping in the Stall

    NASA Technical Reports Server (NTRS)

    Rainey, A Gerald

    1957-01-01

    The oscillating air forces on a two-dimensional wing oscillating in pitch about the midchord have been measured at various mean angles of attack and at Mach numbers of 0.35 and 0.7. The magnitudes of normal-force and pitching-moment coefficients were much higher at high angles of attack than at low angles of attack for some conditions. Large regions of negative damping in pitch were found, and it was shown that the effect of increasing the Mach number 0.35 to 0.7 was to decrease the initial angle of attack at which negative damping occurred. Measurements of the aerodynamic damping of a 10-percent-thick and of a 3-percent-thick finite-span wing oscillating in the first bending mode indicate no regions of negative damping for this type of motion over the range of variables covered. The damping measured at high angles of attack was generally larger than that at low angles of attack. (author)

  16. Control of helicopter rotorblade aerodynamics

    NASA Technical Reports Server (NTRS)

    Fabunmi, James A.

    1991-01-01

    The results of a feasibility study of a method for controlling the aerodynamics of helicopter rotorblades using stacks of piezoelectric ceramic plates are presented. A resonant mechanism is proposed for the amplification of the displacements produced by the stack. This motion is then converted into linear displacement for the actuation of the servoflap of the blades. A design which emulates the actuation of the servoflap on the Kaman SH-2F is used to demonstrate the fact that such a system can be designed to produce the necessary forces and velocities needed to control the aerodynamics of the rotorblades of such a helicopter. Estimates of the electrical power requirements are also presented. A Small Business Innovation Research (SBIR) Phase 2 Program is suggested, whereby a bench-top prototype of the device can be built and tested. A collaborative effort between AEDAR Corporation and Kaman Aerospace Corporation is anticipated for future effort on this project.

  17. Aerodynamics of dynamic wing flexion in translating wings

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Cheng, Bo; Sane, Sanjay P.; Deng, Xinyan

    2015-06-01

    We conducted a systematic experimental study to investigate the aerodynamic effects of active trailing-edge flexion on a high-aspect-ratio wing translating from rest at a high angle of attack. We varied the timing and speed of the trailing-edge flexion and measured the resulting aerodynamic effects using a combination of direct force measurements and two-dimensional PIV flow measurements. The results indicated that the force and flow characteristics depend strongly on the timing of flexion, but relatively weakly on its speed. This is because the force and vortical flow structure are more sensitive to the timing of flexion relative to the shedding of starting vortex and leading-edge vortex. When the trailing-edge flexion occurred slightly before the starting vortex was shed, the lift production was greatly improved with the instantaneous peak lift increased by 54 % and averaged lift increased by 21 % compared with the pre-flexed case where the trailing-edge flexed before wing translation. However, when the trailing-edge flexed during or slightly after the leading-edge vortex shedding, the lift was significantly reduced by the disturbed development of leading-edge vortex. The force measurement results also imply that the trailing-edge flexion prior to wing translation does not augment lift but increases drag, thus resulting in a lower lift-drag ratio as compared to the case of flat wing.

  18. Direct use of linear time-domain aerodynamics in aeroservoelastic analysis: Aerodynamic model

    NASA Technical Reports Server (NTRS)

    Woods, J. A.; Gilbert, Michael G.

    1990-01-01

    The work presented here is the first part of a continuing effort to expand existing capabilities in aeroelasticity by developing the methodology which is necessary to utilize unsteady time-domain aerodynamics directly in aeroservoelastic design and analysis. The ultimate objective is to define a fully integrated state-space model of an aeroelastic vehicle's aerodynamics, structure and controls which may be used to efficiently determine the vehicle's aeroservoelastic stability. Here, the current status of developing a state-space model for linear or near-linear time-domain indicial aerodynamic forces is presented.

  19. Exploring the Aerodynamic Drag of a Moving Cyclist

    ERIC Educational Resources Information Center

    Theilmann, Florian; Reinhard, Christopher

    2016-01-01

    Although the physics of cycling itself is a complex mixture of aerodynamics, physiology, mechanics, and heuristics, using cycling as a context for teaching physics has a tradition of certainly more than 30 years. Here, a possible feature is the discussion of the noticeable resistant forces such as aerodynamic drag and the associated power…

  20. Correlation of Force Production with Apoptosis in Tissue Dynamics

    NASA Astrophysics Data System (ADS)

    Toyama, Yusuke; Peralta, Xomalin; Venakides, Stephanos; Kiehart, Daniel; Edwards, Glenn

    2007-03-01

    To understand embryo morphogenesis, it is necessary to know the force distribution in the various tissues. Since cells are largely inaccessible to mechanical probes in vivo, measurements of the net forces exerted by cells are challenging. The combination of experimental and theoretical approaches has proven to improve our understanding of these forces. A steerable UV-laser microbeam was used to probe the forces and the resulting kinematics were monitored with confocal microscopy. Dorsal closure is a developmental stage in Drosophila embryogenesis, where the dynamics are a consequence of four biological processes [1]. During this stage, cells that have outlived their usefulness undergo apoptosis, a biological process also known as programmed cell death for cells. Apoptotic events were decreased with genetic techniques or increased by irradiation with a UV-C lamp. We present experimental evidence for force generation correlating with apoptosis. This research has been supported by the NIH (GM33830 and GM61240). [1] M. S. Hutson, et al. Science, 300, 145 (2003).

  1. Radial force distribution changes associated with tangential force production in cylindrical grasping, and the importance of anatomical registration

    PubMed Central

    Pataky, Todd C.; Slota, Gregory P.; Latash, Mark L.; Zatsiorsky, Vladimir M.

    2011-01-01

    Radial force (Fr) distributions describe grip force coordination about a cylindrical object. Recent studies have employed only explicit Fr tasks, and have not normalized for anatomical variance when considering Fr distributions. The goals of the present study were (i) to explore Fr during tangential force production tasks, and (ii) to examine the extent to which anatomical registration (i.e. spatial normalization of anatomically analogous structures) could improve signal detectability in Fr data. Twelve subjects grasped a vertically-oriented cylindrical handle (diameter = 6 cm) and matched target upward tangential forces of 10, 20, and 30 N. Fr data were measured using a flexible pressure mat with an angular resolution 4.8 deg, and were registered using piecewise-linear interpolation between five manually identified points-of-interest. Results indicate that Fr was primarily limited to three contact regions: the distal thumb, the distal fingers, and the fingers’ metatacarpal heads, and that, while increases in tangential force caused significant increases in Fr for these regions, they did not significantly affect the Fr distribution across the hand. Registration was found to substantially reduce between-subject variability, as indicated by both accentuated Fr trends, and amplification of the test statistic. These results imply that, while subjects focus Fr primarily on three anatomical regions during cylindrical grasp, inter-subject anatomical differences introduce a variability that, if not corrected for via registration, may compromise one’s ability to draw anatomically relevant conclusions from grasping force data. PMID:22134182

  2. Force feedback coupling with dynamics for physical simulation of product assembly and operation performance

    NASA Astrophysics Data System (ADS)

    Liu, Zhenyu; Tan, Jianrong; Duan, Guifang; Fu, Yun

    2015-01-01

    Most existing force feedback methods are still difficult to meet the requirements of real-time force calculation in virtual assembly and operation with complex objects. In addition, there is often an assumption that the controlled objects are completely free and the target object is only completely fixed or free, thus, the dynamics of the kinematic chain where the controlled objects are located are neglected during the physical simulation of the product manipulation with force feedback interaction. This paper proposes a physical simulation method of product assembly and operation manipulation based on statistically learned contact force prediction model and the coupling of force feedback and dynamics. In the proposed method, based on hidden Markov model (HMM) and local weighting learning (LWL), contact force prediction model is constructed, which can estimate the contact force in real time during interaction. Based on computational load balance model, the computing resources are dynamically assigned and the dynamics integral step is optimized. In addition, smoothing process is performed to the force feedback on the synchronization points. Consequently, we can solve the coupling and synchronization problems of high-frequency feedback force servo, low-frequency dynamics solver servo and scene rendering servo, and realize highly stable and accurate force feedback in the physical simulation of product assembly and operation manipulation. This research proposes a physical simulation method of product assembly and operation manipulation.

  3. Aerodynamic characteristics of sixteen electric, hybrid, and subcompact vehicles

    NASA Technical Reports Server (NTRS)

    Kurtz, D. W.

    1979-01-01

    An elementary electric and hybrid vehicle aerodynamic data base was developed using data obtained on sixteen electric, hybrid, and sub-compact production vehicles tested in the Lockheed-Georgia low-speed wind tunnel. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current four-passenger proto-type automobile which was designed with aerodynamics as an integrated parameter. Vehicles were tested at yaw angles up to 40 degrees and a wing weighting analysis is presented which yields a vehicle's effective drag coefficient as a function of wing velocity and driving cycle. Other parameters investigated included the effects of windows open and closed, radiators open and sealed, and pop-up headlights. Complete six-component force and moment data are presented in both tabular and graphical formats. Only limited commentary is offered since, by its very nature, a data base should consist of unrefined reference material. A justification for pursuing efficient aerodynamic design of EHVs is presented.

  4. Wing Flexion and Aerodynamics Performance of Insect Free Flights

    NASA Astrophysics Data System (ADS)

    Dong, Haibo; Liang, Zongxian; Ren, Yan

    2010-11-01

    Wing flexion in flapping flight is a hallmark of insect flight. It is widely thought that wing flexibility and wing deformation would potentially provide new aerodynamic mechanisms of aerodynamic force productions over completely rigid wings. However, there are lack of literatures on studying fluid dynamics of freely flying insects due to the presence of complex shaped moving boundaries in the flow domain. In this work, a computational study of freely flying insects is being conducted. High resolution, high speed videos of freely flying dragonflies and damselflies is obtained and used as a basis for developing high fidelity geometrical models of the dragonfly body and wings. 3D surface reconstruction technologies are used to obtain wing topologies and kinematics. The wing motions are highly complex and a number of different strategies including singular vector decomposition of the wing kinematics are used to examine the various kinematical features and their impact on the wing performance. Simulations are carried out to examine the aerodynamic performance of all four wings and understand the wake structures of such wings.

  5. Size effects on insect hovering aerodynamics: an integrated computational study.

    PubMed

    Liu, H; Aono, H

    2009-03-01

    Hovering is a miracle of insects that is observed for all sizes of flying insects. Sizing effect in insect hovering on flapping-wing aerodynamics is of interest to both the micro-air-vehicle (MAV) community and also of importance to comparative morphologists. In this study, we present an integrated computational study of such size effects on insect hovering aerodynamics, which is performed using a biology-inspired dynamic flight simulator that integrates the modelling of realistic wing-body morphology, the modelling of flapping-wing and body kinematics and an in-house Navier-Stokes solver. Results of four typical insect hovering flights including a hawkmoth, a honeybee, a fruit fly and a thrips, over a wide range of Reynolds numbers from O(10(4)) to O(10(1)) are presented, which demonstrate the feasibility of the present integrated computational methods in quantitatively modelling and evaluating the unsteady aerodynamics in insect flapping flight. Our results based on realistically modelling of insect hovering therefore offer an integrated understanding of the near-field vortex dynamics, the far-field wake and downwash structures, and their correlation with the force production in terms of sizing and Reynolds number as well as wing kinematics. Our results not only give an integrated interpretation on the similarity and discrepancy of the near- and far-field vortex structures in insect hovering but also demonstrate that our methods can be an effective tool in the MAVs design. PMID:19258688

  6. Size effects on insect hovering aerodynamics: an integrated computational study.

    PubMed

    Liu, H; Aono, H

    2009-03-01

    Hovering is a miracle of insects that is observed for all sizes of flying insects. Sizing effect in insect hovering on flapping-wing aerodynamics is of interest to both the micro-air-vehicle (MAV) community and also of importance to comparative morphologists. In this study, we present an integrated computational study of such size effects on insect hovering aerodynamics, which is performed using a biology-inspired dynamic flight simulator that integrates the modelling of realistic wing-body morphology, the modelling of flapping-wing and body kinematics and an in-house Navier-Stokes solver. Results of four typical insect hovering flights including a hawkmoth, a honeybee, a fruit fly and a thrips, over a wide range of Reynolds numbers from O(10(4)) to O(10(1)) are presented, which demonstrate the feasibility of the present integrated computational methods in quantitatively modelling and evaluating the unsteady aerodynamics in insect flapping flight. Our results based on realistically modelling of insect hovering therefore offer an integrated understanding of the near-field vortex dynamics, the far-field wake and downwash structures, and their correlation with the force production in terms of sizing and Reynolds number as well as wing kinematics. Our results not only give an integrated interpretation on the similarity and discrepancy of the near- and far-field vortex structures in insect hovering but also demonstrate that our methods can be an effective tool in the MAVs design.

  7. Unsteady transonic aerodynamics

    SciTech Connect

    Nixon, D.

    1989-01-01

    Various papers on unsteady transonic aerodynamics are presented. The topics addressed include: physical phenomena associated with unsteady transonic flows, basic equations for unsteady transonic flow, practical problems concerning aircraft, basic numerical methods, computational methods for unsteady transonic flows, application of transonic flow analysis to helicopter rotor problems, unsteady aerodynamics for turbomachinery aeroelastic applications, alternative methods for modeling unsteady transonic flows.

  8. Uncertainty in Computational Aerodynamics

    NASA Technical Reports Server (NTRS)

    Luckring, J. M.; Hemsch, M. J.; Morrison, J. H.

    2003-01-01

    An approach is presented to treat computational aerodynamics as a process, subject to the fundamental quality assurance principles of process control and process improvement. We consider several aspects affecting uncertainty for the computational aerodynamic process and present a set of stages to determine the level of management required to meet risk assumptions desired by the customer of the predictions.

  9. The aerodynamics of hovering flight in Drosophila.

    PubMed

    Fry, Steven N; Sayaman, Rosalyn; Dickinson, Michael H

    2005-06-01

    Using 3D infrared high-speed video, we captured the continuous wing and body kinematics of free-flying fruit flies, Drosophila melanogaster, during hovering and slow forward flight. We then 'replayed' the wing kinematics on a dynamically scaled robotic model to measure the aerodynamic forces produced by the wings. Hovering animals generate a U-shaped wing trajectory, in which large drag forces during a downward plunge at the start of each stroke create peak vertical forces. Quasi-steady mechanisms could account for nearly all of the mean measured force required to hover, although temporal discrepancies between instantaneous measured forces and model predictions indicate that unsteady mechanisms also play a significant role. We analyzed the requirements for hovering from an analysis of the time history of forces and moments in all six degrees of freedom. The wing kinematics necessary to generate sufficient lift are highly constrained by the requirement to balance thrust and pitch torque over the stroke cycle. We also compare the wing motion and aerodynamic forces of free and tethered flies. Tethering causes a strong distortion of the stroke pattern that results in a reduction of translational forces and a prominent nose-down pitch moment. The stereotyped distortion under tethered conditions is most likely due to a disruption of sensory feedback. Finally, we calculated flight power based directly on the measurements of wing motion and aerodynamic forces, which yielded a higher estimate of muscle power during free hovering flight than prior estimates based on time-averaged parameters. This discrepancy is mostly due to a two- to threefold underestimate of the mean profile drag coefficient in prior studies. We also compared our values with the predictions of the same time-averaged models using more accurate kinematic and aerodynamic input parameters based on our high-speed videography measurements. In this case, the time-averaged models tended to overestimate flight

  10. Aerodynamics of Laminar Flames

    NASA Astrophysics Data System (ADS)

    Law, Chung K.

    2000-11-01

    The presentation will review recent advances in the understanding of the structure, dynamics, and geometry of stretched, nonequidiffusive, laminar premixed flames, as exemplified by the unsteady propagation of wrinkled flames in nonuniform flow fields. It is first shown that by considering the effects of aerodynamic stretch on the flame structure, and by allowing for mixture nonequidiffusion, the flame responses, especially the flame propagation speed, can be quantitatively as well as qualitatively modified from the idealized planar limit. Subsequently, by treating the flame as a level surface propagating with the stretch-affected flame speed, problems of increasing complexity are presented to illustrate various features of flame propagation. The illustration first treats the flame as a structureless surface propagating into a constant-density combustible with a constant velocity * the laminar flame speed, and demonstrates the phenomena of cusp formation and volumetric burning rate augmentation through flame wrinkling. By using the stretch-affected flame speed, we then describe the phenomena of cusp broadening as well as tip opening of the Bunsen flame. Finally, by allowing for the density jump across the flame surface, a unified dispersion relation is derived for the intrinsic hydrodynamic, body-force, and nonequidiffusive modes of flame

  11. Aerodynamics of tip-reversal upstroke in a revolving pigeon wing.

    PubMed

    Crandell, Kristen E; Tobalske, Bret W

    2011-06-01

    During slow flight, bird species vary in their upstroke kinematics using either a 'flexed wing' or a distally supinated 'tip-reversal' upstroke. Two hypotheses have been presented concerning the function of the tip-reversal upstroke. The first is that this behavior is aerodynamically inactive and serves to minimize drag. The second is that the tip-reversal upstroke is capable of producing significant aerodynamic forces. Here, we explored the aerodynamic capabilities of the tip-reversal upstroke using a well-established propeller method. Rock dove (Columba livia, N=3) wings were spread and dried in postures characteristic of either mid-upstroke or mid-downstroke and spun at in vivo Reynolds numbers to simulate forces experienced during slow flight. We compared 3D wing shape for the propeller and in vivo kinematics, and found reasonable kinematic agreement between methods (mean differences 6.4% of wing length). We found that the wing in the upstroke posture is capable of producing substantial aerodynamic forces. At in vivo angles of attack (66 deg at mid-upstroke, 46 deg at mid-downstroke), the upstroke wings averaged for three birds produced a lift-to-drag ratio of 0.91, and the downstroke wings produced a lift-to-drag ratio of 3.33. Peak lift-to-drag ratio was 2.5 for upstroke and 6.3 for downstroke. Our estimates of total force production during each half-stroke suggest that downstroke produces a force that supports 115% of bodyweight, and during upstroke a forward-directed force (thrust) is produced at 36% of body weight. PMID:21562173

  12. Aerodynamics of tip-reversal upstroke in a revolving pigeon wing.

    PubMed

    Crandell, Kristen E; Tobalske, Bret W

    2011-06-01

    During slow flight, bird species vary in their upstroke kinematics using either a 'flexed wing' or a distally supinated 'tip-reversal' upstroke. Two hypotheses have been presented concerning the function of the tip-reversal upstroke. The first is that this behavior is aerodynamically inactive and serves to minimize drag. The second is that the tip-reversal upstroke is capable of producing significant aerodynamic forces. Here, we explored the aerodynamic capabilities of the tip-reversal upstroke using a well-established propeller method. Rock dove (Columba livia, N=3) wings were spread and dried in postures characteristic of either mid-upstroke or mid-downstroke and spun at in vivo Reynolds numbers to simulate forces experienced during slow flight. We compared 3D wing shape for the propeller and in vivo kinematics, and found reasonable kinematic agreement between methods (mean differences 6.4% of wing length). We found that the wing in the upstroke posture is capable of producing substantial aerodynamic forces. At in vivo angles of attack (66 deg at mid-upstroke, 46 deg at mid-downstroke), the upstroke wings averaged for three birds produced a lift-to-drag ratio of 0.91, and the downstroke wings produced a lift-to-drag ratio of 3.33. Peak lift-to-drag ratio was 2.5 for upstroke and 6.3 for downstroke. Our estimates of total force production during each half-stroke suggest that downstroke produces a force that supports 115% of bodyweight, and during upstroke a forward-directed force (thrust) is produced at 36% of body weight.

  13. Explosive force production during isometric squats correlates with athletic performance in rugby union players.

    PubMed

    Tillin, Neale Anthony; Pain, Matthew Thomas Gerard; Folland, Jonathan

    2013-01-01

    This study investigated the association between explosive force production during isometric squats and athletic performance (sprint time and countermovement jump height). Sprint time (5 and 20 m) and jump height were recorded in 18 male elite-standard varsity rugby union players. Participants also completed a series of maximal- and explosive-isometric squats to measure maximal force and explosive force at 50-ms intervals up to 250 ms from force onset. Sprint performance was related to early phase (≤100 ms) explosive force normalised to maximal force (5 m, r = -0.63, P = 0.005; and 20 m, r = -0.54, P = 0.020), but jump height was related to later phase (>100 ms) absolute explosive force (0.51 < r < 0.61; 0.006 < P < 0.035). When participants were separated for 5-m sprint time (< or ≥ 1s), the faster group had greater normalised explosive force in the first 150 ms of explosive-isometric squats (33-67%; 0.001 < P < 0.017). The results suggest that explosive force production during isometric squats was associated with athletic performance. Specifically, sprint performance was most strongly related to the proportion of maximal force achieved in the initial phase of explosive-isometric squats, whilst jump height was most strongly related to absolute force in the later phase of the explosive-isometric squats.

  14. Force Production and Reactive Strength Capabilities After Anterior Cruciate Ligament Reconstruction

    PubMed Central

    Flanagan, Eamonn P; Galvin, Lorcan; Harrison, Andrew J

    2008-01-01

    Context: Ambiguity exists in the literature regarding whether individuals can restore function to 100% after anterior cruciate ligament (ACL) reconstruction. The response of force production and reactive strength in stretch-shortening cycle activities after surgery has not been established. Objective: To compare reactive strength and force production capabilities between the involved and uninvolved legs of participants who had undergone ACL reconstruction and rehabilitation with the reactive strength and force production capabilities of a control group. Design: Repeated measures, cross-sectional. Setting: Research laboratory. Patients or Other Participants: Ten participants with ACL reconstructions who had returned to their chosen sports and 10 age-matched and activity-matched control subjects. Intervention(s): We screened the ACL group with the International Knee Documentation Committee Subjective Knee Evaluation Form and functional performance tests to measure a basic level of function. We assessed force production capabilities and reactive strength using squat, countermovement, drop, and rebound jump protocols on a force sledge apparatus. Main Outcome Measure(s): The dependent variables were flight time, peak vertical ground reaction force, leg spring stiffness, and reactive strength index. Results: No participant in the ACL group exhibited functional deficits in comparison with normative values or the control group. Using the force sledge apparatus, we found no notable differences in force production capabilities and reactive strength in the ACL group when comparing the involved with uninvolved legs or the degree of difference between legs with the control group. Conclusions: After ACL reconstruction, rehabilitated participants did not exhibit deficits in force production or reactive strength capabilities. Our results suggest that force production and reactive strength capabilities can be restored to levels comparable with the uninjured control limb and may not

  15. Force production and asymmetric deformation of a flexible flapping wing in forward flight

    NASA Astrophysics Data System (ADS)

    Tian, Fang-Bao; Luo, Haoxiang; Song, Jialei; Lu, Xi-Yun

    2013-01-01

    Insect wings usually are flexible and deform significantly under the combined inertial and aerodynamic load. To study the effect of wing flexibility on both lift and thrust production in forward flight, a two-dimensional numerical simulation is employed to compute the fluid-structure interaction of an elastic wing section translating in an inclined stroke plane while pitching around its leading ledge. The effects of the wing stiffness, mass ratio, stroke plane angle, and flight speed are considered. The results show that the passive pitching due to wing deformation can significantly increase thrust while either maintaining lift at the same level or increasing it simultaneously. Another important finding is that even though the wing structure and actuation kinematics are symmetric, chordwise deformation of the wing shows a larger magnitude during upstroke than during downstroke. The asymmetry is more pronounced when the wing has a low mass ratio so that the fluid-induced deformation is significant. Such an aerodynamic cause may serve as an additional mechanism for the asymmetric deformation pattern observed in real insects.

  16. Synoptic events force biological productivity in Patagonian fjord ecosystems

    NASA Astrophysics Data System (ADS)

    Daneri, Giovanni

    2016-04-01

    The annual cycle of primary productivity of the Patagonian fjords has, to date, been described as a two phase system consisting of a short non productive winter phase (during June and July) and a productive phase extending from late winter (August) to autumn (May). Low levels of primary production, phytoplankton biomass and high concentrations of surface nutrients have been described as characterizing winter conditions while pulsed productivity events typifies the productivity pattern during the extended productive season. Pulsed productivity events characterize coastal waters where inorganic nutrients in surface layers are replenished following periods of intensive utilization by autotrophs. Freshwater input in Patagonian fjords in southern Chile (41-55°S) results in one of the largest estuarine regions worldwide. Here strong haline water column stratification prevents nutrient mixing to the surface layers thus potentially shutting off algal production. Our working hypothesis considered that in order to reconcile the observed pulsed productivity pattern, periodic breaking (associated to surface nutrient replenishment) and re-establishment of estuarine conditions (associated to water column stratification) would be required. Up to now however our understanding of the physical processes that control water column conditions in the Patagonian fjord area has been extremely limited. Here we present evidence linking the passage of synoptic low pressure fronts to pulsed productivity events in the Patagonian fjord area. These front controls and influence local processes of interaction between the fjord and the atmosphere generating a rapid water column response. In the specific case of the Puyuhuapi fjord we have been able to show that such synoptic fronts induce surface flow reversal and water column mixing. Phytoplankton blooming occurs after the passage of the synoptic front once calmer conditions prevail and estuarine conditions are re established. The occurrence of

  17. Radial force distribution changes associated with tangential force production in cylindrical grasping, and the importance of anatomical registration.

    PubMed

    Pataky, Todd C; Slota, Gregory P; Latash, Mark L; Zatsiorsky, Vladimir M

    2012-01-10

    Radial force (F(r)) distributions describe grip force coordination about a cylindrical object. Recent studies have employed only explicit F(r) tasks, and have not normalized for anatomical variance when considering F(r) distributions. The goals of the present study were (i) to explore F(r) during tangential force production tasks, and (ii) to examine the extent to which anatomical registration (i.e. spatial normalization of anatomically analogous structures) could improve signal detectability in F(r) data. Twelve subjects grasped a vertically oriented cylindrical handle (diameter=6 cm) and matched target upward tangential forces of 10, 20, and 30 N. F(r) data were measured using a flexible pressure mat with an angular resolution of 4.8°, and were registered using piecewise-linear interpolation between five manually identified points-of-interest. Results indicate that F(r) was primarily limited to three contact regions: the distal thumb, the distal fingers, and the fingers' metatacarpal heads, and that, while increases in tangential force caused significant increases in F(r) for these regions, they did not significantly affect the F(r) distribution across the hand. Registration was found to substantially reduce between-subject variability, as indicated by both accentuated F(r) trends, and amplification of the test statistic. These results imply that, while subjects focus F(r) primarily on three anatomical regions during cylindrical grasp, inter-subject anatomical differences introduce a variability that, if not corrected for via registration, may compromise one's ability to draw anatomically relevant conclusions from grasping force data. PMID:22134182

  18. Incremental Aerodynamic Coefficient Database for the USA2

    NASA Technical Reports Server (NTRS)

    Richardson, Annie Catherine

    2016-01-01

    In March through May of 2016, a wind tunnel test was conducted by the Aerosciences Branch (EV33) to visually study the unsteady aerodynamic behavior over multiple transition geometries for the Universal Stage Adapter 2 (USA2) in the MSFC Aerodynamic Research Facility's Trisonic Wind Tunnel (TWT). The purpose of the test was to make a qualitative comparison of the transonic flow field in order to provide a recommended minimum transition radius for manufacturing. Additionally, 6 Degree of Freedom force and moment data for each configuration tested was acquired in order to determine the geometric effects on the longitudinal aerodynamic coefficients (Normal Force, Axial Force, and Pitching Moment). In order to make a quantitative comparison of the aerodynamic effects of the USA2 transition geometry, the aerodynamic coefficient data collected during the test was parsed and incorporated into a database for each USA2 configuration tested. An incremental aerodynamic coefficient database was then developed using the generated databases for each USA2 geometry as a function of Mach number and angle of attack. The final USA2 coefficient increments will be applied to the aerodynamic coefficients of the baseline geometry to adjust the Space Launch System (SLS) integrated launch vehicle force and moment database based on the transition geometry of the USA2.

  19. Aerodynamics of Shuttle Orbiter at high altitudes

    NASA Technical Reports Server (NTRS)

    Rault, Didier F. G.

    1993-01-01

    The high-altitude/high-Knudsen number aerodynamics of the Shuttle Orbiter are computed from Low-Earth Orbit down to 100 km using three-dimensional direct simulation Monte Carlo and free molecule codes. Results are compared with Blanchard's latest Shuttle aerodynamic model, which is based on in-flight accelerometer measurements, and bridging formula models. Good comparison is observed, except for the normal force and pitching moment coefficients. The present results were obtained for a generic Shuttle geometry configuration corresponding to a zero deflection for all control surfaces.

  20. Responsiveness of muscle tone characteristics to progressive force production.

    PubMed

    Mustalampi, Sirpa; Häkkinen, Arja; Kautiainen, Hannu; Weir, Adam; Ylinen, Jari

    2013-01-01

    It is possible to measure muscle tone reliably, quickly and objectively using tonometers although they are not yet widely used. In clinical practice, it may be helpful if clinicians could assess the degree of contraction in different parts of a muscle without having to perform time-consuming electromyography measurements. The purpose of this study was to evaluate the responsiveness of different muscle tone characteristics to progressively increased contraction force of quadriceps muscle. Twenty healthy subjects (mean age 39.9 years, 50% women) volunteered. Using 2 different tonometers various muscle viscoelastic properties were measured. The frequency (hertz), logarithmic decrement, and stiffness (newtons per meter) of damped mechanical oscillation of the muscle tissue and tissue compliance (millijoules) were registered from rectus femoris muscle at rest and 20, 40, 60, 80% of maximal voluntary contraction determined using dynamometry. All the values changed linearly with increasing force level. Compliance, oscillation stiffness, and frequency parameters showed large effect sizes (ESs ≥ 0.8). The standardized respoknse mean for compliance was 5.3 (4.8-5.7) mJ, for oscillation stiffness 1.8 (1.3-2.2) N·m(-1), frequency 1.1 (0.6-1.5) Hz, and decrement -0.6 (-1.0 to -0.2). The results indicate that the compliance and oscillation stiffness parameters showed the highest responsiveness and can thus best detect changes in muscle contraction state. The additional value of using tonometers to measure these properties in clinical practice should be investigated further.

  1. A drag-based mechanism for vertical force production in the smallest flying insects

    NASA Astrophysics Data System (ADS)

    Jones, Shannon; Laurenza, Ryan; Miller, Laura

    2013-11-01

    Previous work has shown that the flight kinematics and aerodynamics of the smallest flying insects may be significantly different than that of their larger counterparts. These small insects, such as thrips and parasitoid wasps, are on the order of 1 mm in length and operate at a Reynolds number less than 10. Due to their small size and high wing beat frequency, quantitative data on the wing kinematics of the smallest insects is not available. As a result, there has been much debate and speculation about the flight strategies employed by these insects. With the challenges associated with generating lift at low Reynolds numbers, it could be beneficial for the smallest insects to use a drag-based motion to generate some or all of its vertical force, however this has not been rigorously investigated. We used computational fluid dynamics to investigate the feasibility of drag-based propulsion in the tiniest insects. We investigated the vertical force generated by an idealized drag-based vertical stroke over a range of Reynolds numbers from 1 to 150. We also compared this stroke to more conventional hovering stroke kinematics such as that of a fruit fly and dragonfly.

  2. Forced degradation studies of rapamycin: identification of autoxidation products.

    PubMed

    Oyler, Alan R; Segmuller, Brigitte E; Sun, Yanqiu; Polshyna, Ann; Dunphy, Richard; Armstrong, Barbara L; Achord, Patrick; Maryanoff, Cynthia A; Alquier, Lori; Il'ichev, Yuri V

    2012-02-01

    The immunosuppressant drug rapamycin, also known as Sirolimus, underwent autoxidation under mild conditions to give numerous monomeric and oligomeric compounds, which were generally characterized by size-exclusion chromatography and NP-HPLC with UV and MS detection. Some of the more predominant products, epoxides and ketones, were isolated and identified. Two epoxides and 10S-epimer of rapamycin were described for the first time. Observed rapamycin isomers were also addressed. Computational chemistry was used to provide mechanistic insights. Formation of the majority of the rapamycin products could be rationalized with free radical-mediated autoxidation reactions involving alkene and alcohol sites. Methodological aspects of oxidative stress testing are discussed. PMID:22088479

  3. Identification of aerodynamic models for maneuvering aircraft

    NASA Technical Reports Server (NTRS)

    Lan, C. Edward; Hu, C. C.

    1992-01-01

    A Fourier analysis method was developed to analyze harmonic forced-oscillation data at high angles of attack as functions of the angle of attack and its time rate of change. The resulting aerodynamic responses at different frequencies are used to build up the aerodynamic models involving time integrals of the indicial type. An efficient numerical method was also developed to evaluate these time integrals for arbitrary motions based on a concept of equivalent harmonic motion. The method was verified by first using results from two-dimensional and three-dimensional linear theories. The developed models for C sub L, C sub D, and C sub M based on high-alpha data for a 70 deg delta wing in harmonic motions showed accurate results in reproducing hysteresis. The aerodynamic models are further verified by comparing with test data using ramp-type motions.

  4. Aerodynamics of magnetic levitation (MAGLEV) trains

    NASA Technical Reports Server (NTRS)

    Schetz, Joseph A.; Marchman, James F., III

    1996-01-01

    High-speed (500 kph) trains using magnetic forces for levitation, propulsion and control offer many advantages for the nation and a good opportunity for the aerospace community to apply 'high tech' methods to the domestic sector. One area of many that will need advanced research is the aerodynamics of such MAGLEV (Magnetic Levitation) vehicles. There are important issues with regard to wind tunnel testing and the application of CFD to these devices. This talk will deal with the aerodynamic design of MAGLEV vehicles with emphasis on wind tunnel testing. The moving track facility designed and constructed in the 6 ft. Stability Wind Tunnel at Virginia Tech will be described. Test results for a variety of MAGLEV vehicle configurations will be presented. The last topic to be discussed is a Multi-disciplinary Design approach that is being applied to MAGLEV vehicle configuration design including aerodynamics, structures, manufacturability and life-cycle cost.

  5. Nonlinear aerodynamic modeling using multivariate orthogonal functions

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.

    1993-01-01

    A technique was developed for global modeling of nonlinear aerodynamic coefficients using multivariate orthogonal functions based on the data. Each orthogonal function retained in the model was decomposed into an expansion of ordinary polynomials in the independent variables, so that the final model could be interpreted as selectively retained terms from a multivariable power series expansion. A predicted squared-error metric was used to determine the orthogonal functions to be retained in the model; analytical derivatives were easily computed. The approach was demonstrated on the Z-body axis aerodynamic force coefficient (Cz) wind tunnel data for an F-18 research vehicle which came from a tabular wind tunnel and covered the entire subsonic flight envelope. For a realistic case, the analytical model predicted experimental values of Cz very well. The modeling technique is shown to be capable of generating a compact, global analytical representation of nonlinear aerodynamics. The polynomial model has good predictive capability, global validity, and analytical differentiability.

  6. Effects of wing deformation on aerodynamic performance of a revolving insect wing

    NASA Astrophysics Data System (ADS)

    Noda, Ryusuke; Nakata, Toshiyuki; Liu, Hao

    2014-12-01

    Flexible wings of insects and bio-inspired micro air vehicles generally deform remarkably during flapping flight owing to aerodynamic and inertial forces, which is of highly nonlinear fluid-structure interaction (FSI) problems. To elucidate the novel mechanisms associated with flexible wing aerodynamics in the low Reynolds number regime, we have built up a FSI model of a hawkmoth wing undergoing revolving and made an investigation on the effects of flexible wing deformation on aerodynamic performance of the revolving wing model. To take into account the characteristics of flapping wing kinematics we designed a kinematic model for the revolving wing in two-fold: acceleration and steady rotation, which are based on hovering wing kinematics of hawkmoth, Manduca sexta. Our results show that both aerodynamic and inertial forces demonstrate a pronounced increase during acceleration phase, which results in a significant wing deformation. While the aerodynamic force turns to reduce after the wing acceleration terminates due to the burst and detachment of leading-edge vortices (LEVs), the dynamic wing deformation seem to delay the burst of LEVs and hence to augment the aerodynamic force during and even after the acceleration. During the phase of steady rotation, the flexible wing model generates more vertical force at higher angles of attack (40°-60°) but less horizontal force than those of a rigid wing model. This is because the wing twist in spanwise owing to aerodynamic forces results in a reduction in the effective angle of attack at wing tip, which leads to enhancing the aerodynamics performance by increasing the vertical force while reducing the horizontal force. Moreover, our results point out the importance of the fluid-structure interaction in evaluating flexible wing aerodynamics: the wing deformation does play a significant role in enhancing the aerodynamic performances but works differently during acceleration and steady rotation, which is mainly induced by

  7. Stochastic order parameter equation of isometric force production revealed by drift-diffusion estimates

    NASA Astrophysics Data System (ADS)

    Frank, T. D.; Friedrich, R.; Beek, P. J.

    2006-11-01

    We address two questions that are central to understanding human motor control variability: what kind of dynamical components contribute to motor control variability (i.e., deterministic and/or random ones), and how are those components structured? To this end, we derive a stochastic order parameter equation for isometric force production from experimental data using drift-diffusion estimates. We show that the force variability increases with the required force output because of a decrease of deterministic stability and an accompanying increase of noise intensity. A structural analysis reveals that the deterministic component consists of a linear control loop, while the random component involves a noise source that scales with force output. In addition, we present evidence for the existence of a subject-independent overall noise level of human isometric force production.

  8. Advanced turboprop installation aerodynamics

    NASA Technical Reports Server (NTRS)

    Smith, R. C.

    1981-01-01

    The expected aerodynamic effects of a propfan installed on a thick supercritical wing are summarized qualitatively. Nacelle/wing and jet interactions, slipstream incremental velocity, nonuniform inflow, and swirl loss recovery are discussed.

  9. Aerodynamics of Heavy Vehicles

    NASA Astrophysics Data System (ADS)

    Choi, Haecheon; Lee, Jungil; Park, Hyungmin

    2014-01-01

    We present an overview of the aerodynamics of heavy vehicles, such as tractor-trailers, high-speed trains, and buses. We introduce three-dimensional flow structures around simplified model vehicles and heavy vehicles and discuss the flow-control devices used for drag reduction. Finally, we suggest important unsteady flow structures to investigate for the enhancement of aerodynamic performance and future directions for experimental and numerical approaches.

  10. Aerodynamic Shutoff Valve

    NASA Technical Reports Server (NTRS)

    Horstman, Raymond H.

    1992-01-01

    Aerodynamic flow achieved by adding fixed fairings to butterfly valve. When valve fully open, fairings align with butterfly and reduce wake. Butterfly free to turn, so valve can be closed, while fairings remain fixed. Design reduces turbulence in flow of air in internal suction system. Valve aids in development of improved porous-surface boundary-layer control system to reduce aerodynamic drag. Applications primarily aerospace. System adapted to boundary-layer control on high-speed land vehicles.

  11. Unsteady aerodynamics of insect flight.

    PubMed

    Ellington, C P

    1995-01-01

    Over the past decade, the importance of unsteady aerodynamic mechanisms for flapping insect flight has become widely recognised. Even at the fastest flight speeds, the old quasi-steady aerodynamic interpretation seems inadequate to explain the extra lift produced by the wings. Recent experiments on rigid model wings have confirmed the effectiveness of several postulated high-lift mechanisms. Delayed stall can produce extra lift for several chords of travel during the translational phases of the wingbeat. Lift can also be enhanced by circulation created during pronation and supination by rotational mechanisms: the fling/peel, the near fling/peel and isolated rotation. These studies have revealed large leading-edge vortices which contribute to the circulation around the wing, augmenting the lift. The mechanisms show distinctive patterns of vortex shedding from leading and trailing edges. The results of flow visualization experiments on tethered insects are reviewed in an attempt to identify the high-lift mechanisms actually employed. The fling/peel mechanism is clearly used by some insects. The near fling/peel is the wing motion most commonly observed, but evidence for the production of high lift remains indirect. For many insects, lift on the upstroke probably results from delayed stall instead of the flex mechanism of isolated rotation. The large leading-edge vortices from experiments on rigid model wings are greatly reduced or missing around the real insect wings, often making the identification of aerodynamic mechanisms inconclusive. A substantial spanwise flow component has been detected over the aerodynamic upper wing surface, which should transport leading-edge vorticity towards the wingtip before it has much time to roll up. This spanwise transport, arising from centrifugal acceleration, is probably a general phenomenon for flapping insect flight. It should reduce and stabilise any leading-edge vortices that are present, which is essential for preventing

  12. Bat flight: aerodynamics, kinematics and flight morphology.

    PubMed

    Hedenström, Anders; Johansson, L Christoffer

    2015-03-01

    Bats evolved the ability of powered flight more than 50 million years ago. The modern bat is an efficient flyer and recent research on bat flight has revealed many intriguing facts. By using particle image velocimetry to visualize wake vortices, both the magnitude and time-history of aerodynamic forces can be estimated. At most speeds the downstroke generates both lift and thrust, whereas the function of the upstroke changes with forward flight speed. At hovering and slow speed bats use a leading edge vortex to enhance the lift beyond that allowed by steady aerodynamics and an inverted wing during the upstroke to further aid weight support. The bat wing and its skeleton exhibit many features and control mechanisms that are presumed to improve flight performance. Whereas bats appear aerodynamically less efficient than birds when it comes to cruising flight, they have the edge over birds when it comes to manoeuvring. There is a direct relationship between kinematics and the aerodynamic performance, but there is still a lack of knowledge about how (and if) the bat controls the movements and shape (planform and camber) of the wing. Considering the relatively few bat species whose aerodynamic tracks have been characterized, there is scope for new discoveries and a need to study species representing more extreme positions in the bat morphospace. PMID:25740899

  13. Aerodynamics of high-speed railway train

    NASA Astrophysics Data System (ADS)

    Raghunathan, Raghu S.; Kim, H.-D.; Setoguchi, T.

    2002-10-01

    Railway train aerodynamic problems are closely associated with the flows occurring around train. Much effort to speed up the train system has to date been paid on the improvement of electric motor power rather than understanding the flow around the train. This has led to larger energy losses and performance deterioration of the train system, since the flows around train are more disturbed due to turbulence of the increased speed of the train, and consequently the flow energies are converted to aerodynamic drag, noise and vibrations. With the speed-up of train, many engineering problems which have been neglected at low train speeds, are being raised with regard to aerodynamic noise and vibrations, impulse forces occurring as two trains intersect each other, impulse wave at the exit of tunnel, ear discomfort of passengers inside train, etc. These are of major limitation factors to the speed-up of train system. The present review addresses the state of the art on the aerodynamic and aeroacoustic problems of high-speed railway train and highlights proper control strategies to alleviate undesirable aerodynamic problems of high-speed railway train system.

  14. Bat flight: aerodynamics, kinematics and flight morphology.

    PubMed

    Hedenström, Anders; Johansson, L Christoffer

    2015-03-01

    Bats evolved the ability of powered flight more than 50 million years ago. The modern bat is an efficient flyer and recent research on bat flight has revealed many intriguing facts. By using particle image velocimetry to visualize wake vortices, both the magnitude and time-history of aerodynamic forces can be estimated. At most speeds the downstroke generates both lift and thrust, whereas the function of the upstroke changes with forward flight speed. At hovering and slow speed bats use a leading edge vortex to enhance the lift beyond that allowed by steady aerodynamics and an inverted wing during the upstroke to further aid weight support. The bat wing and its skeleton exhibit many features and control mechanisms that are presumed to improve flight performance. Whereas bats appear aerodynamically less efficient than birds when it comes to cruising flight, they have the edge over birds when it comes to manoeuvring. There is a direct relationship between kinematics and the aerodynamic performance, but there is still a lack of knowledge about how (and if) the bat controls the movements and shape (planform and camber) of the wing. Considering the relatively few bat species whose aerodynamic tracks have been characterized, there is scope for new discoveries and a need to study species representing more extreme positions in the bat morphospace.

  15. Aerodynamic Control of a Pitching Airfoil by Distributed Bleed Actuation

    NASA Astrophysics Data System (ADS)

    Kearney, John; Glezer, Ari

    2013-11-01

    The aerodynamic forces and moments on a dynamically pitching 2-D airfoil model are controlled in wind tunnel experiments using distributed active bleed. Bleed flow on the suction surface downstream of the leading edge is driven by pressure differences across the airfoil and is regulated by low-power louver actuators. The bleed interacts with cross flows to effect time-dependent variations of the vorticity flux and thereby alters the local flow attachment, resulting in significant changes in pre- and post-stall lift and pitching moment (over 50% increase in baseline post-stall lift). The flow field over the airfoil is measured using high-speed (2000 fps) PIV, resolving the dynamics and characteristic time-scales of production and advection of vorticity concentrations that are associated with transient variations in the aerodynamic forces and moments. In particular, it is shown that the actuation improves the lift hysteresis and pitch stability during the oscillatory pitching by altering the evolution of the dynamic stall vortex and the ensuing flow attachment during the downstroke. Supported by the Rotorcraft Center (VLRCOE) at Georgia Tech.

  16. Forces Shaping Future U.S. Coal Production and Use

    USGS Publications Warehouse

    Attanasi, E.D.; Pierce, Brenda S.

    2001-01-01

    More than half of the electricity in the United States is generated by coal-fired powerplants. U.S. coal producers sell almost 90 percent of their product for electricity generation, and so, the future of the U.S. coal industry will be determined by the future of coal-fired electricity-generation plants. The U.S. Geological Survey (USGS) is completing a National Coal Resource Assessment (NCRA) of five major coal-producing regions of the United States (fig. 1): (1) the Appalachian Basin, (2) the Illinois Basin, (3) the Gulf Coast, (4) the Colorado Plateau, and (5) the Northern Rocky Mountains and Great Plains. The Powder River and Williston Basins are the principal producing areas of the Northern Rocky Mountains and Great Plains region.

  17. A flight experiment to measure rarefied-flow aerodynamics

    NASA Technical Reports Server (NTRS)

    Blanchard, Robert C.

    1990-01-01

    A flight experiment to measure rarefied-flow aerodynamics of a blunt lifting body is being developed by NASA. This experiment, called the Rarefied-Flow Aerodynamic Measurement Experiment (RAME), is part of the Aeroassist Flight Experiment (AFE) mission, which is a Pathfinder design tool for aeroassisted orbital transfer vehicles. The RAME will use flight measurements from accelerometers, rate gyros, and pressure transducers, combined with knowledge of AFE in-flight mass properties and trajectory, to infer aerodynamic forces and moments in the rarefied-flow environment, including transition into the hypersonic continuum regime. Preflight estimates of the aerodynamic measurements are based upon environment models, existing computer simulations, and ground test results. Planned maneuvers at several altitudes will provide a first-time opportunity to examine gas-surface accommondation effects on aerodynamic coefficients in an environment of changing atmospheric composition. A description is given of the RAME equipment design.

  18. Modeling of aircraft unsteady aerodynamic characteristics. Part 1: Postulated models

    NASA Technical Reports Server (NTRS)

    Klein, Vladislav; Noderer, Keith D.

    1994-01-01

    A short theoretical study of aircraft aerodynamic model equations with unsteady effects is presented. The aerodynamic forces and moments are expressed in terms of indicial functions or internal state variables. The first representation leads to aircraft integro-differential equations of motion; the second preserves the state-space form of the model equations. The formulations of unsteady aerodynamics is applied in two examples. The first example deals with a one-degree-of-freedom harmonic motion about one of the aircraft body axes. In the second example, the equations for longitudinal short-period motion are developed. In these examples, only linear aerodynamic terms are considered. The indicial functions are postulated as simple exponentials and the internal state variables are governed by linear, time-invariant, first-order differential equations. It is shown that both approaches to the modeling of unsteady aerodynamics lead to identical models.

  19. Aerodynamics of high frequency flapping wings

    NASA Astrophysics Data System (ADS)

    Hu, Zheng; Roll, Jesse; Cheng, Bo; Deng, Xinyan

    2010-11-01

    We investigated the aerodynamic performance of high frequency flapping wings using a 2.5 gram robotic insect mechanism developed in our lab. The mechanism flaps up to 65Hz with a pair of man-made wing mounted with 10cm wingtip-to-wingtip span. The mean aerodynamic lift force was measured by a lever platform, and the flow velocity and vorticity were measured using a stereo DPIV system in the frontal, parasagittal, and horizontal planes. Both near field (leading edge vortex) and far field flow (induced flow) were measured with instantaneous and phase-averaged results. Systematic experiments were performed on the man-made wings, cicada and hawk moth wings due to their similar size, frequency and Reynolds number. For insect wings, we used both dry and freshly-cut wings. The aerodynamic force increase with flapping frequency and the man-made wing generates more than 4 grams of lift at 35Hz with 3 volt input. Here we present the experimental results and the major differences in their aerodynamic performances.

  20. The influence of the elastic vibration of the carrier to the aerodynamics of the external store in air-launch-to-orbit process

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Ye, Zheng-Yin; Wu, Jie

    2016-11-01

    The separation between the carrier and store is one of the most important and difficult phases in Air-launch-to-orbit technology. Based on the previous researches, the interference aerodynamic forces of the store caused by the carrier are obvious in the earlier time during the separation. And the interference aerodynamics will be more complex when considering the elastic deformation of the carrier. Focusing on the conditions that in the earlier time during the separation, the steady and unsteady interference aerodynamic forces of the store are calculated at different angle of attacks and relative distances between the carrier and store. During the calculation, the elastic vibrations of the carrier are considered. According to the cause of formations of the interference aerodynamics, the interference aerodynamic forces of the store are divided into several components. The relative magnitude, change rule, sphere of influence and mechanism of interference aerodynamic forces components of the store are analyzed quantitatively. When the relative distance between the carrier and store is small, the interference aerodynamic forces caused by the elastic vibration of the carrier is about half of the total aerodynamic forces of the store. And as the relative distance increases, the value of interference aerodynamic forces decrease. When the relative distance is larger than twice the mean aerodynamic chord of the carrier, the values of interference aerodynamic forces of the store can be ignored. Besides, under the influence of the steady interference aerodynamic forces, the lift characteristics of the store are worse and the static stability margin is poorer.

  1. Optimal plane change by low aerodynamic forces

    NASA Technical Reports Server (NTRS)

    Vinh, Nguyen X.; Ma, Der-Ming

    1990-01-01

    This paper presents the exact dimensionless equations of motion and the necessary conditions for the computation of the optimal trajectories of a hypervelocity vehicle flying through a nonrotating spherical planetary atmosphere. It is shown that there are two types of maneuvers with nearly identical plane change. In the hard maneuver, the vehicle is pulled down to low altitude for aerodyamic plane change before exit at the prescribed final speed. In the slow maneuver which is described in detail in this paper, the vehicle remains in orbital flight with a small incremental plane change during each passage through the perigee. This maneuver requires several revolutions, and the technique for computation is similar to that in the problem of contraction of orbit.

  2. Aerodynamics of the hovering hummingbird.

    PubMed

    Warrick, Douglas R; Tobalske, Bret W; Powers, Donald R

    2005-06-23

    Despite profound musculoskeletal differences, hummingbirds (Trochilidae) are widely thought to employ aerodynamic mechanisms similar to those used by insects. The kinematic symmetry of the hummingbird upstroke and downstroke has led to the assumption that these halves of the wingbeat cycle contribute equally to weight support during hovering, as exhibited by insects of similar size. This assumption has been applied, either explicitly or implicitly, in widely used aerodynamic models and in a variety of empirical tests. Here we provide measurements of the wake of hovering rufous hummingbirds (Selasphorus rufus) obtained with digital particle image velocimetry that show force asymmetry: hummingbirds produce 75% of their weight support during the downstroke and only 25% during the upstroke. Some of this asymmetry is probably due to inversion of their cambered wings during upstroke. The wake of hummingbird wings also reveals evidence of leading-edge vortices created during the downstroke, indicating that they may operate at Reynolds numbers sufficiently low to exploit a key mechanism typical of insect hovering. Hummingbird hovering approaches that of insects, yet remains distinct because of effects resulting from an inherently dissimilar-avian-body plan.

  3. An Upscaling Analysis on Aerodynamic Roughness Length in North Tibetan Plateau based on Eddy Covariance, Large Aperture Scitillometer Data and Remote Sensing Product

    NASA Astrophysics Data System (ADS)

    SUN, G.; Hu, Z.; Fanglin, S.

    2015-12-01

    Abstract: Aerodynamic roughness length (z0m) is a crucial parameter in quantifying momentum, sensible heat, and latent heat fluxes between atmosphere and land surface, and depends greatly on spatial scales. This paper presents a tentative study in upscaling of z0m in North Tibetan Plateau, based on ground measurement data of different spatial scales from eddy covariance (EC) and large aperture scintillometer (LAS) and NDVI products from MODIS with 250m and 2km spatial resolutions. The comparison of z0m calculated from EC and LAS data indicates that the z0m values at both scales have apparent seasonal variations, and are in good agreement with that of NDVI. However, z0m_LAS is higher than z0m_EC, which is attributed to the differences of roughness elements in their footprints. An upscaling relationship about z0m was established with z0m observations and NDVI products of MODIS.In addition, an altitude correction factor was introduced into vegetation height estimation with NDVI, because the low temperature environment in North Tibetan Plateau due to its high altitude has strong influence on vegetation heights.The z0m retrievals with NDVI products with 250m spatial resolutions from June to September are validated with ground z0m results of Naqu/Amdo, Naqu/MS3478 and Naqu/NewD66 and the agreement is acceptable. The spatial distribution of z0m at 250m spatial resolutions in North Tibetan Plateau from June to September shows that z0m values are below 0.015m in most area, except the area in the southeast part where z0m values reach 0.025m due to lower altitudes. The z0m retrievals at 2km spatial resolutions of the same period range from 0.015 to 0.065m, and high values appear in the area with lower altitudes.The z0m retrievals at both spatial scales are affected by altitude, indicating the uniqueness of Tibetan Plateau. Frequency statistics on z0m retrievals at both spatial resolutions from June to September, 2012 shows obvious typical monthly changes in monsoon season.

  4. Segregated and overlapping neural circuits exist for the production of static and dynamic precision grip force.

    PubMed

    Neely, Kristina A; Coombes, Stephen A; Planetta, Peggy J; Vaillancourt, David E

    2013-03-01

    A central topic in sensorimotor neuroscience is the static-dynamic dichotomy that exists throughout the nervous system. Previous work examining motor unit synchronization reports that the activation strategy and timing of motor units differ for static and dynamic tasks. However, it remains unclear whether segregated or overlapping blood-oxygen-level-dependent (BOLD) activity exists in the brain for static and dynamic motor control. This study compared the neural circuits associated with the production of static force to those associated with the production of dynamic force pulses. To that end, healthy young adults (n = 17) completed static and dynamic precision grip force tasks during functional magnetic resonance imaging (fMRI). Both tasks activated core regions within the visuomotor network, including primary and sensory motor cortices, premotor cortices, multiple visual areas, putamen, and cerebellum. Static force was associated with unique activity in a right-lateralized cortical network including inferior parietal lobe, ventral premotor cortex, and dorsolateral prefrontal cortex. In contrast, dynamic force was associated with unique activity in left-lateralized and midline cortical regions, including supplementary motor area, superior parietal lobe, fusiform gyrus, and visual area V3. These findings provide the first neuroimaging evidence supporting a lateralized pattern of brain activity for the production of static and dynamic precision grip force.

  5. Aerodynamic database development of the ESA intermediate experimental vehicle

    NASA Astrophysics Data System (ADS)

    Pezzella, Giuseppe; Marino, Giuliano; Rufolo, Giuseppe C.

    2014-01-01

    This work deals with the aerodynamic database development of the Intermediate Experiment Vehicle. The aerodynamic analysis, carried out for the whole flight scenario, relies on computational fluid dynamics, wind tunnel test, and engineering-based design data generated during the project phases, from rarefied flow conditions, to hypersonic continuum flow up to reach subsonic speeds regime. Therefore, the vehicle aerodynamic database covers the range of Mach number, angle of attack, sideslip and control surface deflections foreseen for the vehicle nominal re-entry. In particular, the databasing activities are developed in the light of build-up approach. This means that all aerodynamic force and moment coefficients are provided by means of a linear summation over certain number of incremental contributions such as, for example, effect of sideslip angle, aerodynamic control surface effectiveness, etc. Each force and moment coefficient is treated separately and appropriate equation is provided, in which all the pertinent contributions for obtaining the total coefficient for any selected flight conditions appear. To this aim, all the available numerical and experimental aerodynamic data are gathered in order to explicit the functional dependencies from each aerodynamic model addend through polynomial expressions obtained with the least squares method. These polynomials are function of the primary variable that drives the phenomenon whereas secondary dependencies are introduced directly into its unknown coefficients which are determined by means of best-fitting algorithms.

  6. Aerodynamic preliminary analysis system 2. Part 1: Theory

    NASA Technical Reports Server (NTRS)

    Bonner, E.; Clever, W.; Dunn, K.

    1981-01-01

    A subsonic/supersonic/hypersonic aerodynamic analysis was developed by integrating the Aerodynamic Preliminary Analysis System (APAS), and the inviscid force calculation modules of the Hypersonic Arbitrary Body Program. APAS analysis was extended for nonlinear vortex forces using a generalization of the Polhamus analogy. The interactive system provides appropriate aerodynamic models for a single input geometry data base and has a run/output format similar to a wind tunnel test program. The user's manual was organized to cover the principle system activities of a typical application, geometric input/editing, aerodynamic evaluation, and post analysis review/display. Sample sessions are included to illustrate the specific task involved and are followed by a comprehensive command/subcommand dictionary used to operate the system.

  7. Hypersonic Arbitrary-Body Aerodynamics (HABA) for conceptual design

    SciTech Connect

    Salguero, D.E.

    1990-03-15

    The Hypersonic Arbitrary-Body Aerodynamics (HABA) computer program predicts static and dynamic aerodynamic derivatives at hypersonic speeds for any vehicle geometry. It is intended to be used during conceptual design studies where fast computational speed is required. It uses the same geometry and hypersonic aerodynamic methods as the Mark IV Supersonic/Hypersonic Arbitrary-Body Program (SHABP) developed under sponsorship of the Air Force Flight Dynamics Laboratory; however, the input and output formats have been improved to make it easier to use. This program is available as part of the Department 9140 CAE software.

  8. Powered-Lift Aerodynamics and Acoustics. [conferences

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Powered lift technology is reviewed. Topics covered include: (1) high lift aerodynamics; (2) high speed and cruise aerodynamics; (3) acoustics; (4) propulsion aerodynamics and acoustics; (5) aerodynamic and acoustic loads; and (6) full-scale and flight research.

  9. Applied computational aerodynamics

    SciTech Connect

    Henne, P.A.

    1990-01-01

    The present volume discusses the original development of the panel method, the mapping solutions and singularity distributions of linear potential schemes, the capabilities of full-potential, Euler, and Navier-Stokes schemes, the use of the grid-generation methodology in applied aerodynamics, subsonic airfoil design, inverse airfoil design for transonic applications, the divergent trailing-edge airfoil innovation in CFD, Euler and potential computational results for selected aerodynamic configurations, and the application of CFD to wing high-lift systems. Also discussed are high-lift wing modifications for an advanced-capability EA-6B aircraft, Navier-Stokes methods for internal and integrated propulsion system flow predictions, the use of zonal techniques for analysis of rotor-stator interaction, CFD applications to complex configurations, CFD applications in component aerodynamic design of the V-22, Navier-Stokes computations of a complete F-16, CFD at supersonic/hypersonic speeds, and future CFD developments.

  10. Transonic and supersonic ground effect aerodynamics

    NASA Astrophysics Data System (ADS)

    Doig, G.

    2014-08-01

    A review of recent and historical work in the field of transonic and supersonic ground effect aerodynamics has been conducted, focussing on applied research on wings and aircraft, present and future ground transportation, projectiles, rocket sleds and other related bodies which travel in close ground proximity in the compressible regime. Methods for ground testing are described and evaluated, noting that wind tunnel testing is best performed with a symmetry model in the absence of a moving ground; sled or rail testing is ultimately preferable, though considerably more expensive. Findings are reported on shock-related ground influence on aerodynamic forces and moments in and accelerating through the transonic regime - where force reversals and the early onset of local supersonic flow is prevalent - as well as more predictable behaviours in fully supersonic to hypersonic ground effect flows.

  11. Nonlinear aerodynamic wing design

    NASA Technical Reports Server (NTRS)

    Bonner, Ellwood

    1985-01-01

    The applicability of new nonlinear theoretical techniques is demonstrated for supersonic wing design. The new technology was utilized to define outboard panels for an existing advanced tactical fighter model. Mach 1.6 maneuver point design and multi-operating point compromise surfaces were developed and tested. High aerodynamic efficiency was achieved at the design conditions. A corollary result was that only modest supersonic penalties were incurred to meet multiple aerodynamic requirements. The nonlinear potential analysis of a practical configuration arrangement correlated well with experimental data.

  12. Computational aerodynamics and design

    NASA Technical Reports Server (NTRS)

    Ballhaus, W. F., Jr.

    1982-01-01

    The role of computational aerodynamics in design is reviewed with attention given to the design process; the proper role of computations; the importance of calibration, interpretation, and verification; the usefulness of a given computational capability; and the marketing of new codes. Examples of computational aerodynamics in design are given with particular emphasis on the Highly Maneuverable Aircraft Technology. Finally, future prospects are noted, with consideration given to the role of advanced computers, advances in numerical solution techniques, turbulence models, complex geometries, and computational design procedures. Previously announced in STAR as N82-33348

  13. Rarefaction Effects in Hypersonic Aerodynamics

    NASA Astrophysics Data System (ADS)

    Riabov, Vladimir V.

    2011-05-01

    The Direct Simulation Monte-Carlo (DSMC) technique is used for numerical analysis of rarefied-gas hypersonic flows near a blunt plate, wedge, two side-by-side plates, disk, torus, and rotating cylinder. The role of various similarity parameters (Knudsen and Mach numbers, geometrical and temperature factors, specific heat ratios, and others) in aerodynamics of the probes is studied. Important kinetic effects that are specific for the transition flow regime have been found: non-monotonic lift and drag of plates, strong repulsive force between side-by-side plates and cylinders, dependence of drag on torus radii ratio, and the reverse Magnus effect on the lift of a rotating cylinder. The numerical results are in a good agreement with experimental data, which were obtained in a vacuum chamber at low and moderate Knudsen numbers from 0.01 to 10.

  14. Unsteady Aerodynamics of Insect Flight

    NASA Astrophysics Data System (ADS)

    Wang, Z. Jane

    2000-03-01

    The myth `bumble-bees can not fly according to conventional aerodynamics' simply reflects our poor understanding of unsteady viscous fluid dynamics. In particular, we lack a theory of vorticity shedding due to dynamic boundaries at the intermediate Reynolds numbers relevant to insect flight, typically between 10^2 and 10^4, where both viscous and inertial effects are important. In our study, we compute unsteady viscous flows, governed by the Navier-Stokes equation, about a two dimensional flapping wing which mimics the motion of an insect wing. I will present two main results: the existence of a prefered frequency in forward flight and its physical origin, and 2) the vortex dynamics and forces in hovering dragonfly flight.

  15. Air flow testing on aerodynamic truck

    NASA Technical Reports Server (NTRS)

    1975-01-01

    After leasing a cab-over tractor-trailer from a Southern California firm, Dryden researchers added sheet metal modifications like those shown here. They rounded the front corners and edges, and placed a smooth fairing on the cab's roofs and sides extending back to the trailer. During the investigation of truck aerodynamics, the techniques honed in flight research proved highly applicable. By closing the gap between the cab and the trailer, for example, researchers discovered a significant reduction in aerodynamic drag, one resulting in 20 to 25 percent less fuel consumption than the standard design. Many truck manufacturers subsequently incorporated similar modifications on their products.

  16. Nanotribological effects of hair care products and environment on human hair using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Latorre, Carmen; Bhushan, Bharat

    2005-07-01

    Tribological properties are useful in the study of human hair and other biological materials. Major sources of investigation for conditioner treated hair includes localization of conditioner, mechanisms related to changes in surface roughness, friction, and adhesion on the nanoscale due to conditioner agents, and how the products change the microstructure of the cuticle. The paper presents nanotribological studies investigating surface roughness, friction, and adhesion using atomic force/friction force microscopy (AFM/FFM). Test samples include virgin and chemically damaged hair, both with and without commercial conditioner treatment, as well as chemically damaged hair with experimental conditioner treatments. Friction force mapping provides insight into the localized change in friction caused by the application of hair care materials. Adhesive force maps to study adhesion on the cuticle surface provide information about localization and distribution of conditioner as well. A discussion is presented on these properties of hair as a function of relative humidity, temperature, durability, and conditioning treatments.

  17. Post-Flight Aerodynamic and Aerothermal Model Validation of a Supersonic Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Tang, Chun; Muppidi, Suman; Bose, Deepak; Van Norman, John W.; Tanimoto, Rebekah; Clark, Ian

    2015-01-01

    NASA's Low Density Supersonic Decelerator Program is developing new technologies that will enable the landing of heavier payloads in low density environments, such as Mars. A recent flight experiment conducted high above the Hawaiian Islands has demonstrated the performance of several decelerator technologies. In particular, the deployment of the Robotic class Supersonic Inflatable Aerodynamic Decelerator (SIAD-R) was highly successful, and valuable data were collected during the test flight. This paper outlines the Computational Fluid Dynamics (CFD) analysis used to estimate the aerodynamic and aerothermal characteristics of the SIAD-R. Pre-flight and post-flight predictions are compared with the flight data, and a very good agreement in aerodynamic force and moment coefficients is observed between the CFD solutions and the reconstructed flight data.

  18. Parachute Aerodynamics From Video Data

    NASA Technical Reports Server (NTRS)

    Schoenenberger, Mark; Queen, Eric M.; Cruz, Juan R.

    2005-01-01

    A new data analysis technique for the identification of static and dynamic aerodynamic stability coefficients from wind tunnel test video data is presented. This new technique was applied to video data obtained during a parachute wind tunnel test program conducted in support of the Mars Exploration Rover Mission. Total angle-of-attack data obtained from video images were used to determine the static pitching moment curve of the parachute. During the original wind tunnel test program the static pitching moment curve had been determined by forcing the parachute to a specific total angle-of -attack and measuring the forces generated. It is shown with the new technique that this parachute, when free to rotate, trims at an angle-of-attack two degrees lower than was measured during the forced-angle tests. An attempt was also made to extract pitch damping information from the video data. Results suggest that the parachute is dynamically unstable at the static trim point and tends to become dynamically stable away from the trim point. These trends are in agreement with limit-cycle-like behavior observed in the video. However, the chaotic motion of the parachute produced results with large uncertainty bands.

  19. Aerodynamics of Race Cars

    NASA Astrophysics Data System (ADS)

    Katz, Joseph

    2006-01-01

    Race car performance depends on elements such as the engine, tires, suspension, road, aerodynamics, and of course the driver. In recent years, however, vehicle aerodynamics gained increased attention, mainly due to the utilization of the negative lift (downforce) principle, yielding several important performance improvements. This review briefly explains the significance of the aerodynamic downforce and how it improves race car performance. After this short introduction various methods to generate downforce such as inverted wings, diffusers, and vortex generators are discussed. Due to the complex geometry of these vehicles, the aerodynamic interaction between the various body components is significant, resulting in vortex flows and lifting surface shapes unlike traditional airplane wings. Typical design tools such as wind tunnel testing, computational fluid dynamics, and track testing, and their relevance to race car development, are discussed as well. In spite of the tremendous progress of these design tools (due to better instrumentation, communication, and computational power), the fluid dynamic phenomenon is still highly nonlinear, and predicting the effect of a particular modification is not always trouble free. Several examples covering a wide range of vehicle shapes (e.g., from stock cars to open-wheel race cars) are presented to demonstrate this nonlinear nature of the flow field.

  20. Efficient Global Aerodynamic Modeling from Flight Data

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.

    2012-01-01

    A method for identifying global aerodynamic models from flight data in an efficient manner is explained and demonstrated. A novel experiment design technique was used to obtain dynamic flight data over a range of flight conditions with a single flight maneuver. Multivariate polynomials and polynomial splines were used with orthogonalization techniques and statistical modeling metrics to synthesize global nonlinear aerodynamic models directly and completely from flight data alone. Simulation data and flight data from a subscale twin-engine jet transport aircraft were used to demonstrate the techniques. Results showed that global multivariate nonlinear aerodynamic dependencies could be accurately identified using flight data from a single maneuver. Flight-derived global aerodynamic model structures, model parameter estimates, and associated uncertainties were provided for all six nondimensional force and moment coefficients for the test aircraft. These models were combined with a propulsion model identified from engine ground test data to produce a high-fidelity nonlinear flight simulation very efficiently. Prediction testing using a multi-axis maneuver showed that the identified global model accurately predicted aircraft responses.

  1. Identification of aerodynamic models for maneuvering aircraft

    NASA Technical Reports Server (NTRS)

    Chin, Suei; Lan, C. Edward

    1990-01-01

    Due to the requirement of increased performance and maneuverability, the flight envelope of a modern fighter is frequently extended to the high angle-of-attack regime. Vehicles maneuvering in this regime are subjected to nonlinear aerodynamic loads. The nonlinearities are due mainly to three-dimensional separated flow and concentrated vortex flow that occur at large angles of attack. Accurate prediction of these nonlinear airloads is of great importance in the analysis of a vehicle's flight motion and in the design of its flight control system. A satisfactory evaluation of the performance envelope of the aircraft may require a large number of coupled computations, one for each change in initial conditions. To avoid the disadvantage of solving the coupled flow-field equations and aircraft's motion equations, an alternate approach is to use a mathematical modeling to describe the steady and unsteady aerodynamics for the aircraft equations of motion. Aerodynamic forces and moments acting on a rapidly maneuvering aircraft are, in general, nonlinear functions of motion variables, their time rate of change, and the history of maneuvering. A numerical method was developed to analyze the nonlinear and time-dependent aerodynamic response to establish the generalized indicial function in terms of motion variables and their time rates of change.

  2. Aerodynamic analysis of an isolated vehicle wheel

    NASA Astrophysics Data System (ADS)

    Leśniewicz, P.; Kulak, M.; Karczewski, M.

    2014-08-01

    Increasing fuel prices force the manufacturers to look into all aspects of car aerodynamics including wheels, tyres and rims in order to minimize their drag. By diminishing the aerodynamic drag of vehicle the fuel consumption will decrease, while driving safety and comfort will improve. In order to properly illustrate the impact of a rotating wheel aerodynamics on the car body, precise analysis of an isolated wheel should be performed beforehand. In order to represent wheel rotation in contact with the ground, presented CFD simulations included Moving Wall boundary as well as Multiple Reference Frame should be performed. Sliding mesh approach is favoured but too costly at the moment. Global and local flow quantities obtained during simulations were compared to an experiment in order to assess the validity of the numerical model. Results of investigation illustrates dependency between type of simulation and coefficients (drag and lift). MRF approach proved to be a better solution giving result closer to experiment. Investigation of the model with contact area between the wheel and the ground helps to illustrate the impact of rotating wheel aerodynamics on the car body.

  3. Rarefield-Flow Shuttle Aerodynamics Flight Model

    NASA Technical Reports Server (NTRS)

    Blanchard, Robert C.; Larman, Kevin T.; Moats, Christina D.

    1994-01-01

    A model of the Shuttle Orbiter rarefied-flow aerodynamic force coefficients has been derived from the ratio of flight acceleration measurements. The in-situ, low-frequency (less than 1Hz), low-level (approximately 1 x 10(exp -6) g) acceleration measurements are made during atmospheric re-entry. The experiment equipment designed and used for this task is the High Resolution Accelerometer Package (HiRAP), one of the sensor packages in the Orbiter Experiments Program. To date, 12 HiRAP re-entry mission data sets spanning a period of about 10 years have been processed. The HiRAP-derived aerodynamics model is described in detail. The model includes normal and axial hypersonic continuum coefficient equations as function of angle of attack, body-flap deflection, and elevon deflection. Normal and axial free molecule flow coefficient equations as a function of angle of attack are also presented, along with flight-derived rarefied-flow transition bridging formulae. Comparisons are made between the aerodynamics model, data from the latest Orbiter Operational Aerodynamic Design Data Book, applicable computer simulations, and wind-tunnel data.

  4. Sensitivity of Simulated Global Ocean Carbon Flux Estimates to Forcing by Reanalysis Products

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Casey, Nancy W.; Rousseaux, Cecile S.

    2015-01-01

    Reanalysis products from MERRA, NCEP2, NCEP1, and ECMWF were used to force an established ocean biogeochemical model to estimate air-sea carbon fluxes (FCO2) and partial pressure of carbon dioxide (pCO2) in the global oceans. Global air-sea carbon fluxes and pCO2 were relatively insensitive to the choice of forcing reanalysis. All global FCO2 estimates from the model forced by the four different reanalyses were within 20% of in situ estimates (MERRA and NCEP1 were within 7%), and all models exhibited statistically significant positive correlations with in situ estimates across the 12 major oceanographic basins. Global pCO2 estimates were within 1% of in situ estimates with ECMWF being the outlier at 0.6%. Basin correlations were similar to FCO2. There were, however, substantial departures among basin estimates from the different reanalysis forcings. The high latitudes and tropics had the largest ranges in estimated fluxes among the reanalyses. Regional pCO2 differences among the reanalysis forcings were muted relative to the FCO2 results. No individual reanalysis was uniformly better or worse in the major oceanographic basins. The results provide information on the characterization of uncertainty in ocean carbon models due to choice of reanalysis forcing.

  5. Isometric force production parameters during normal and experimental low back pain conditions

    PubMed Central

    Descarreaux, Martin; Blouin, Jean-Sébastien; Teasdale, Normand

    2005-01-01

    Background The control of force and its between-trial variability are often taken as critical determinants of motor performance. Subjects performed isometric trunk flexion and extension forces without and with experiment pain to examine if pain yields changes in the control of trunk forces. The objective of this study is to determine if experimental low back pain modifies trunk isometric force production. Methods Ten control subjects participated in this study. They were required to exert 50 and 75% of their isometric maximal trunk flexion and extension torque. In a learning phase preceding the non painful and painful trials, visual and verbal feedbacks were provided. Then, subjects were asked to perform 10 trials without any feedback. Time to peak torque, time to peak torque variability, peak torque variability as well as constant and absolute error in peak torque were calculated. Time to peak and peak dF/dt were computed to determine if the first peak of dF/dt could predict the peak torque achieved. Results Absolute and constant errors were higher in the presence of a painful electrical stimulation. Furthermore, peak torque variability for the higher level of force was increased with in the presence of experimental pain. The linear regressions between peak dF/dt, time to peak dF/dt and peak torque were similar for both conditions. Experimental low back pain yielded increased absolute and constant errors as well as a greater peak torque variability for the higher levels of force. The control strategy, however, remained the same between the non painful and painful condition. Cutaneous pain affects some isometric force production parameters but modifications of motor control strategies are not implemented spontaneously. Conclusions It is hypothesized that adaptation of motor strategies to low back pain is implemented gradually over time. This would enable LBP patients to perform their daily tasks with presumably less pain and more accuracy. PMID:15703067

  6. Ares I Aerodynamic Testing at the Boeing Polysonic Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Pinier, Jeremy T.; Niskey, Charles J.; Hanke, Jeremy L.; Tomek, William G.

    2011-01-01

    Throughout three full design analysis cycles, the Ares I project within the Constellation program has consistently relied on the Boeing Polysonic Wind Tunnel (PSWT) for aerodynamic testing of the subsonic, transonic and supersonic portions of the atmospheric flight envelope (Mach=0.5 to 4.5). Each design cycle required the development of aerodynamic databases for the 6 degree-of-freedom (DOF) forces and moments, as well as distributed line-loads databases covering the full range of Mach number, total angle-of-attack, and aerodynamic roll angle. The high fidelity data collected in this facility has been consistent with the data collected in NASA Langley s Unitary Plan Wind Tunnel (UPWT) at the overlapping condition ofMach=1.6. Much insight into the aerodynamic behavior of the launch vehicle during all phases of flight was gained through wind tunnel testing. Important knowledge pertaining to slender launch vehicle aerodynamics in particular was accumulated. In conducting these wind tunnel tests and developing experimental aerodynamic databases, some challenges were encountered and are reported as lessons learned in this paper for the benefit of future crew launch vehicle aerodynamic developments.

  7. Joint computational and experimental aerodynamics research on a hypersonic vehicle

    SciTech Connect

    Oberkampf, W.L.; Aeschliman, D.P.; Walker, M.M.

    1992-01-01

    A closely coupled computational and experimental aerodynamics research program was conducted on a hypersonic vehicle configuration at Mach 8. Aerodynamic force and moment measurements and flow visualization results were obtained in the Sandia National Laboratories hypersonic wind tunnel for laminar boundary layer conditions. Parabolized and iterative Navier-Stokes simulations were used to predict flow fields and forces and moments on the hypersonic configuration. The basic vehicle configuration is a spherically blunted 10{degrees} cone with a slice parallel with the axis of the vehicle. On the slice portion of the vehicle, a flap can be attached so that deflection angles of 10{degrees}, 20{degrees}, and 30{degrees} can be obtained. Comparisons are made between experimental and computational results to evaluate quality of each and to identify areas where improvements are needed. This extensive set of high-quality experimental force and moment measurements is recommended for use in the calibration and validation of computational aerodynamics codes. 22 refs.

  8. Measurements of Aerodynamic Damping in the MIT Transonic Rotor

    NASA Technical Reports Server (NTRS)

    Crawley, E. F.

    1981-01-01

    A method was developed and demonstrated for the direct measurement of aerodynamic forcing and aerodynamic damping of a transonic compressor. The method is based on the inverse solution of the structural dynamic equations of motion of the blade disk system in order to determine the forces acting on the system. The disturbing and damping forces acting on a given blade are determined if the equations of motion are expressed in individual blade coordinates. If the structural dynamic equations are transformed to multiblade coordinates, the damping can be measured for blade disk modes, and related to a reduced frequency and interblade phase angle. In order to measure the aerodynamic damping in this way, the free response to a known excitation is studied.

  9. The Dynamics of Voluntary Force Production in Afferented Muscle Influence Involuntary Tremor

    PubMed Central

    Laine, Christopher M.; Nagamori, Akira; Valero-Cuevas, Francisco J.

    2016-01-01

    Voluntary control of force is always marked by some degree of error and unsteadiness. Both neural and mechanical factors contribute to these fluctuations, but how they interact to produce them is poorly understood. In this study, we identify and characterize a previously undescribed neuromechanical interaction where the dynamics of voluntary force production suffice to generate involuntary tremor. Specifically, participants were asked to produce isometric force with the index finger and use visual feedback to track a sinusoidal target spanning 5–9% of each individual's maximal voluntary force level. Force fluctuations and EMG activity over the flexor digitorum superficialis (FDS) muscle were recorded and their frequency content was analyzed as a function of target phase. Force variability in either the 1–5 or 6–15 Hz frequency ranges tended to be largest at the peaks and valleys of the target sinusoid. In those same periods, FDS EMG activity was synchronized with force fluctuations. We then constructed a physiologically-realistic computer simulation in which a muscle-tendon complex was set inside of a feedback-driven control loop. Surprisingly, the model sufficed to produce phase-dependent modulation of tremor similar to that observed in humans. Further, the gain of afferent feedback from muscle spindles was critical for appropriately amplifying and shaping this tremor. We suggest that the experimentally-induced tremor may represent the response of a viscoelastic muscle-tendon system to dynamic drive, and therefore does not fall into known categories of tremor generation, such as tremorogenic descending drive, stretch-reflex loop oscillations, motor unit behavior, or mechanical resonance. Our findings motivate future efforts to understand tremor from a perspective that considers neuromechanical coupling within the context of closed-loop control. The strategy of combining experimental recordings with physiologically-sound simulations will enable thorough

  10. The Dynamics of Voluntary Force Production in Afferented Muscle Influence Involuntary Tremor.

    PubMed

    Laine, Christopher M; Nagamori, Akira; Valero-Cuevas, Francisco J

    2016-01-01

    Voluntary control of force is always marked by some degree of error and unsteadiness. Both neural and mechanical factors contribute to these fluctuations, but how they interact to produce them is poorly understood. In this study, we identify and characterize a previously undescribed neuromechanical interaction where the dynamics of voluntary force production suffice to generate involuntary tremor. Specifically, participants were asked to produce isometric force with the index finger and use visual feedback to track a sinusoidal target spanning 5-9% of each individual's maximal voluntary force level. Force fluctuations and EMG activity over the flexor digitorum superficialis (FDS) muscle were recorded and their frequency content was analyzed as a function of target phase. Force variability in either the 1-5 or 6-15 Hz frequency ranges tended to be largest at the peaks and valleys of the target sinusoid. In those same periods, FDS EMG activity was synchronized with force fluctuations. We then constructed a physiologically-realistic computer simulation in which a muscle-tendon complex was set inside of a feedback-driven control loop. Surprisingly, the model sufficed to produce phase-dependent modulation of tremor similar to that observed in humans. Further, the gain of afferent feedback from muscle spindles was critical for appropriately amplifying and shaping this tremor. We suggest that the experimentally-induced tremor may represent the response of a viscoelastic muscle-tendon system to dynamic drive, and therefore does not fall into known categories of tremor generation, such as tremorogenic descending drive, stretch-reflex loop oscillations, motor unit behavior, or mechanical resonance. Our findings motivate future efforts to understand tremor from a perspective that considers neuromechanical coupling within the context of closed-loop control. The strategy of combining experimental recordings with physiologically-sound simulations will enable thorough exploration

  11. The Dynamics of Voluntary Force Production in Afferented Muscle Influence Involuntary Tremor

    PubMed Central

    Laine, Christopher M.; Nagamori, Akira; Valero-Cuevas, Francisco J.

    2016-01-01

    Voluntary control of force is always marked by some degree of error and unsteadiness. Both neural and mechanical factors contribute to these fluctuations, but how they interact to produce them is poorly understood. In this study, we identify and characterize a previously undescribed neuromechanical interaction where the dynamics of voluntary force production suffice to generate involuntary tremor. Specifically, participants were asked to produce isometric force with the index finger and use visual feedback to track a sinusoidal target spanning 5–9% of each individual's maximal voluntary force level. Force fluctuations and EMG activity over the flexor digitorum superficialis (FDS) muscle were recorded and their frequency content was analyzed as a function of target phase. Force variability in either the 1–5 or 6–15 Hz frequency ranges tended to be largest at the peaks and valleys of the target sinusoid. In those same periods, FDS EMG activity was synchronized with force fluctuations. We then constructed a physiologically-realistic computer simulation in which a muscle-tendon complex was set inside of a feedback-driven control loop. Surprisingly, the model sufficed to produce phase-dependent modulation of tremor similar to that observed in humans. Further, the gain of afferent feedback from muscle spindles was critical for appropriately amplifying and shaping this tremor. We suggest that the experimentally-induced tremor may represent the response of a viscoelastic muscle-tendon system to dynamic drive, and therefore does not fall into known categories of tremor generation, such as tremorogenic descending drive, stretch-reflex loop oscillations, motor unit behavior, or mechanical resonance. Our findings motivate future efforts to understand tremor from a perspective that considers neuromechanical coupling within the context of closed-loop control. The strategy of combining experimental recordings with physiologically-sound simulations will enable thorough

  12. Freight Wing Trailer Aerodynamics Final Technical Report

    SciTech Connect

    Sean Graham

    2007-10-31

    Freight Wing Incorporated utilized the opportunity presented by a DOE category two Inventions and Innovations grant to commercialize and improve upon aerodynamic technology for semi-tuck trailers, capable of decreasing heavy vehicle fuel consumption, related environmental damage, and U.S. consumption of foreign oil. Major project goals included the demonstration of aerodynamic trailer technology in trucking fleet operations, and the development and testing of second generation products. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck’s fuel consumption. However, significant design challenges have prevented past concepts from meeting industry needs. Freight Wing utilized a 2003 category one Inventions and Innovations grant to develop practical solutions to trailer aerodynamics. Fairings developed for the front, rear, and bottom of standard semi-trailers together demonstrated a 7% improvement to fuel economy in scientific tests conducted by the Transportation Research Center (TRC). Operational tests with major trucking fleets proved the functionality of the products, which were subsequently brought to market. This category two grant enabled Freight Wing to further develop, test and commercialize its products, resulting in greatly increased understanding and acceptance of aerodynamic trailer technology. Commercialization was stimulated by offering trucking fleets 50% cost sharing on trial implementations of Freight Wing products for testing and evaluation purposes. Over 230 fairings were implemented through the program with 35 trucking fleets including industry leaders such as Wal-Mart, Frito Lay and Whole Foods. The feedback from these testing partnerships was quite positive with product performance exceeding fleet expectations in many cases. Fleet feedback also was also valuable from a product development standpoint and assisted the design of several second generation products

  13. A simple method for converting frequency domain aerodynamics to the time domain

    NASA Technical Reports Server (NTRS)

    Dowell, E. H.

    1980-01-01

    A simple, direct procedure was developed for converting frequency domain aerodynamics into indicial aerodynamics. The data required for aerodynamic forces in the frequency domain may be obtained from any available (linear) theory. The method retains flexibility for the analyst and is based upon the particular character of the frequency domain results. An evaluation of the method was made for incompressible, subsonic, and transonic two dimensional flows.

  14. Velopharyngeal orifice area prediction during aerodynamic simulation of fricative consonants.

    PubMed

    Smith, B E; Weinberg, B

    1983-01-01

    The present work examined the predictive nature of modeled velopharyngeal orifice area calculations obtained using the hydrokinetic equation (Warren and DuBois, 1964) during conditions simulating voiceless fricative production. Results indicated that accurate estimates of velopharyngeal orifice area can be obtained during aerodynamic events like those known to exist during fricative production. These findings were interpreted to lend support to the view that aerodynamic assessment incorporating hydrokinetic principles provides a useful, noninvasive method for clinical testing and research investigation of velopharyngeal function.

  15. Wind turbine blade aerodynamics: The analysis of field test data

    SciTech Connect

    Luttges, M.W.; Miller, M.S.; Robinson, M.C.; Shipley, D.E.; Young, T.S.

    1994-08-01

    Data obtained from the National Renewable Energy Laboratory site test of a wind turbine (The Combined Experiment) was analyzed specifically to capture information regarding the aerodynamic loading experienced by the machine rotor blades. The inflow conditions were shown to be extremely variable. These inflows yielded three different operational regimes about the blades. Each regime produced very different aerodynamic loading conditions. Two of these regimes could not have been readily predicted from wind tunnel data. These conditions are being subjected to further analyses to provide new guidelines for both designers and operators. The roles of unsteady aerodynamics effects are highlighted since periods of dynamic stall were shown to be associated with brief episodes of high aerodynamic forces.

  16. Mechanics and aerodynamics of insect flight control.

    PubMed

    Taylor, G K

    2001-11-01

    Insects have evolved sophisticated fight control mechanisms permitting a remarkable range of manoeuvres. Here, I present a qualitative analysis of insect flight control from the perspective of flight mechanics, drawing upon both the neurophysiology and biomechanics literatures. The current literature does not permit a formal, quantitative analysis of flight control, because the aerodynamic force systems that biologists have measured have rarely been complete and the position of the centre of gravity has only been recorded in a few studies. Treating the two best-known insect orders (Diptera and Orthoptera) separately from other insects, I discuss the control mechanisms of different insects in detail. Recent experimental studies suggest that the helicopter model of flight control proposed for Drosophila spp. may be better thought of as a facultative strategy for flight control, rather than the fixed (albeit selected) constraint that it is usually interpreted to be. On the other hand, the so-called 'constant-lift reaction' of locusts appears not to be a reflex for maintaining constant lift at varying angles of attack, as is usually assumed, but rather a mechanism to restore the insect to pitch equilibrium following a disturbance. Differences in the kinematic control mechanisms used by the various insect orders are related to differences in the arrangement of the wings, the construction of the flight motor and the unsteady mechanisms of lift production that are used. Since the evolution of insect flight control is likely to have paralleled the evolutionary refinement of these unsteady aerodynamic mechanisms, taxonomic differences in the kinematics of control could provide an assay of the relative importance of different unsteady mechanisms. Although the control kinematics vary widely between orders, the number of degrees of freedom that different insects can control will always be limited by the number of independent control inputs that they use. Control of the moments

  17. The aerodynamics of insect flight.

    PubMed

    Sane, Sanjay P

    2003-12-01

    The flight of insects has fascinated physicists and biologists for more than a century. Yet, until recently, researchers were unable to rigorously quantify the complex wing motions of flapping insects or measure the forces and flows around their wings. However, recent developments in high-speed videography and tools for computational and mechanical modeling have allowed researchers to make rapid progress in advancing our understanding of insect flight. These mechanical and computational fluid dynamic models, combined with modern flow visualization techniques, have revealed that the fluid dynamic phenomena underlying flapping flight are different from those of non-flapping, 2-D wings on which most previous models were based. In particular, even at high angles of attack, a prominent leading edge vortex remains stably attached on the insect wing and does not shed into an unsteady wake, as would be expected from non-flapping 2-D wings. Its presence greatly enhances the forces generated by the wing, thus enabling insects to hover or maneuver. In addition, flight forces are further enhanced by other mechanisms acting during changes in angle of attack, especially at stroke reversal, the mutual interaction of the two wings at dorsal stroke reversal or wing-wake interactions following stroke reversal. This progress has enabled the development of simple analytical and empirical models that allow us to calculate the instantaneous forces on flapping insect wings more accurately than was previously possible. It also promises to foster new and exciting multi-disciplinary collaborations between physicists who seek to explain the phenomenology, biologists who seek to understand its relevance to insect physiology and evolution, and engineers who are inspired to build micro-robotic insects using these principles. This review covers the basic physical principles underlying flapping flight in insects, results of recent experiments concerning the aerodynamics of insect flight, as well

  18. HYSHOT-2 Aerodynamics

    NASA Astrophysics Data System (ADS)

    Cain, T.; Owen, R.; Walton, C.

    2005-02-01

    The scramjet flight test Hyshot-2, flew on the 30 July 2002. The programme, led by the University of Queensland, had the primary objective of obtaining supersonic combustion data in flight for comparison with measurements made in shock tunnels. QinetiQ was one of the sponsors, and also provided aerodynamic data and trajectory predictions for the ballistic re-entry of the spinning sounding rocket. The unconventional missile geometry created by the nose-mounted asymmetric-scramjet in conjunction with the high angle of attack during re-entry makes the problem interesting. This paper presents the wind tunnel measurements and aerodynamic calculations used as input for the trajectory prediction. Indirect comparison is made with data obtained in the Hyshot-2 flight using a 6 degree-of-freedom trajectory simulation.

  19. Advanced Aerodynamic Control Effectors

    NASA Technical Reports Server (NTRS)

    Wood, Richard M.; Bauer, Steven X. S.

    1999-01-01

    A 1990 research program that focused on the development of advanced aerodynamic control effectors (AACE) for military aircraft has been reviewed and summarized. Data are presented for advanced planform, flow control, and surface contouring technologies. The data show significant increases in lift, reductions in drag, and increased control power, compared to typical aerodynamic designs. The results presented also highlighted the importance of planform selection in the design of a control effector suite. Planform data showed that dramatic increases in lift (greater than 25%) can be achieved with multiple wings and a sawtooth forebody. Passive porosity and micro drag generator control effector data showed control power levels exceeding that available from typical effectors (moving surfaces). Application of an advanced planform to a tailless concept showed benefits of similar magnitude as those observed in the generic studies.

  20. Control of cytoplasmic dynein force production and processivity by its C-terminal domain

    NASA Astrophysics Data System (ADS)

    Nicholas, Matthew P.; Höök, Peter; Brenner, Sibylle; Wynne, Caitlin L.; Vallee, Richard B.; Gennerich, Arne

    2015-02-01

    Cytoplasmic dynein is a microtubule motor involved in cargo transport, nuclear migration and cell division. Despite structural conservation of the dynein motor domain from yeast to higher eukaryotes, the extensively studied S. cerevisiae dynein behaves distinctly from mammalian dyneins, which produce far less force and travel over shorter distances. However, isolated reports of yeast-like force production by mammalian dynein have called interspecies differences into question. We report that functional differences between yeast and mammalian dynein are real and attributable to a C-terminal motor element absent in yeast, which resembles a ‘cap’ over the central pore of the mammalian dynein motor domain. Removal of this cap increases the force generation of rat dynein from 1 pN to a yeast-like 6 pN and greatly increases its travel distance. Our findings identify the CT-cap as a novel regulator of dynein function.

  1. Control of cytoplasmic dynein force production and processivity by its C-terminal domain.

    PubMed

    Nicholas, Matthew P; Höök, Peter; Brenner, Sibylle; Wynne, Caitlin L; Vallee, Richard B; Gennerich, Arne

    2015-02-11

    Cytoplasmic dynein is a microtubule motor involved in cargo transport, nuclear migration and cell division. Despite structural conservation of the dynein motor domain from yeast to higher eukaryotes, the extensively studied S. cerevisiae dynein behaves distinctly from mammalian dyneins, which produce far less force and travel over shorter distances. However, isolated reports of yeast-like force production by mammalian dynein have called interspecies differences into question. We report that functional differences between yeast and mammalian dynein are real and attributable to a C-terminal motor element absent in yeast, which resembles a 'cap' over the central pore of the mammalian dynein motor domain. Removal of this cap increases the force generation of rat dynein from 1 pN to a yeast-like 6 pN and greatly increases its travel distance. Our findings identify the CT-cap as a novel regulator of dynein function.

  2. Aerodynamic noise sources

    NASA Astrophysics Data System (ADS)

    Munin, A. G.; Kuznetsov, V. M.; Leontev, E. A.

    A general theory is developed for aerodynamic sound generation and its propagation in an inhomogeneous medium. Results of theoretical and experimental studies of the acoustic characteristics of jets are discussed, and a solution is presented to the problem concerning the noise from a section, free rotor, and a rotor located inside a channel. Sound propagation in a channel with flow and selection of soundproofing liners for the channel walls are also discussed.

  3. Aerodynamics of Unsteady Sailing Kinetics

    NASA Astrophysics Data System (ADS)

    Keil, Colin; Schutt, Riley; Borshoff, Jennifer; Alley, Philip; de Zegher, Maximilien; Williamson, Chk

    2015-11-01

    In small sailboats, the bodyweight of the sailor is proportionately large enough to induce significant unsteady motion of the boat and sail. Sailors use a variety of kinetic techniques to create sail dynamics which can provide an increment in thrust, thereby increasing the boatspeed. In this study, we experimentally investigate the unsteady aerodynamics associated with two techniques, ``upwind leech flicking'' and ``downwind S-turns''. We explore the dynamics of an Olympic class Laser sailboat equipped with a GPS, IMU, wind sensor, and camera array, sailed expertly by a member of the US Olympic team. The velocity heading of a sailing boat is oriented at an apparent wind angle to the flow. In contrast to classic flapping propulsion, the heaving of the sail section is not perpendicular to the sail's motion through the air. This leads to heave with components parallel and perpendicular to the incident flow. The characteristic motion is recreated in a towing tank where the vortex structures generated by a representative 2-D sail section are observed using Particle Image Velocimetry and the measurement of thrust and lift forces. Amongst other results, we show that the increase in driving force, generated due to heave, is larger for greater apparent wind angles.

  4. Carry-Over of Force Production Symmetry in Athletes of Differing Strength Levels.

    PubMed

    Bailey, Christopher A; Sato, Kimitake; Burnett, Angus; Stone, Michael H

    2015-11-01

    This study sought to determine the level of association between bilateral force production symmetry assessment methods (standing weight distribution [WtD], unloaded and lightly loaded jumps, and isometric strength) and to determine whether the amount of symmetry carry-over between these tasks differs for strong and weak athletes. Subjects for this study included male (n = 31) and female (n = 32) athletes from National Collegiate Athletic Association Division I sports. Athletes performed WtD, unloaded and lightly loaded (20 kg) static and countermovement jumps, and isometric midthigh pull (IMTP) assessments on 2 adjacent force plates. Ground reaction force data were used to calculate symmetry variables and performance-related variables. Using Pearson zero order correlations, evaluations of the amount of symmetry carry-over were made. Weight distribution correlated strongly with jump peak force (PF) (r = 0.628-0.664). Strong relationships were also observed between loading conditions for jump variables (r = 0.568-0.957) as were the relationships between jump types for PF, peak power, and net impulse (r = 0.506-0.834). Based on the pooled sample, there was a lack of association between IMTP and WtD for jump symmetry variables. However, when examining strong and weak groups, rate of force development showed moderate to strong symmetry carry-over in the strongest athletes (r = 0.416-0.589). Stronger athletes appear to display similar explosive strength symmetry characteristics in dynamic and isometric assessments, unlike weaker athletes. Strength seems to influence the amount of force production symmetry carry-over between bilateral assessments. There may be optimal loads and variables for symmetry assessment, but these may differ based on population characteristics.

  5. Aerodynamic control with passively pitching wings

    NASA Astrophysics Data System (ADS)

    Gravish, Nick; Wood, Robert

    Flapping wings may pitch passively under aerodynamic and inertial loads. Such passive pitching is observed in flapping wing insect and robot flight. The effect of passive wing pitch on the control dynamics of flapping wing flight are unexplored. Here we demonstrate in simulation and experiment the critical role wing pitching plays in yaw control of a flapping wing robot. We study yaw torque generation by a flapping wing allowed to passively rotate in the pitch axis through a rotational spring. Yaw torque is generated through alternating fast and slow upstroke and and downstroke. Yaw torque sensitively depends on both the rotational spring force law and spring stiffness, and at a critical spring stiffness a bifurcation in the yaw torque control relationship occurs. Simulation and experiment reveal the dynamics of this bifurcation and demonstrate that anomalous yaw torque from passively pitching wings is the result of aerodynamic and inertial coupling between the pitching and stroke-plane dynamics.

  6. Ion drag force on an absorbing grain in highly collisional plasma in the presence of plasma production and loss processes

    SciTech Connect

    Chaudhuri, Manis; Khrapak, Sergei A.; Morfill, Gregor E.

    2008-09-07

    The ion drag force acting on a small absorbing spherical grain has been calculated analytically in highly collisional plasma with slowly drifting ions taking into account plasma production and loss mechanisms in the vicinity of the grain. It is shown that both the magnitude and direction of the ion drag force are strongly influenced by the plasma production and loss mechanisms. The parameter regimes for the 'positive' and 'negative' ion drag forces acting on an absorbing grain have been identified.

  7. Application of CAD/CAE class systems to aerodynamic analysis of electric race cars

    NASA Astrophysics Data System (ADS)

    Grabowski, L.; Baier, A.; Buchacz, A.; Majzner, M.; Sobek, M.

    2015-11-01

    Aerodynamics is one of the most important factors which influence on every aspect of a design of a car and car driving parameters. The biggest influence aerodynamics has on design of a shape of a race car body, especially when the main objective of the race is the longest distance driven in period of time, which can not be achieved without low energy consumption and low drag of a car. Designing shape of the vehicle body that must generate the lowest possible drag force, without compromising the other parameters of the drive. In the article entitled „Application of CAD/CAE class systems to aerodynamic analysis of electric race cars” are being presented problems solved by computer analysis of cars aerodynamics and free form modelling. Analysis have been subjected to existing race car of a Silesian Greenpower Race Team. On a basis of results of analysis of existence of Kammback aerodynamic effect innovative car body were modeled. Afterwards aerodynamic analysis were performed to verify existence of aerodynamic effect for innovative shape and to recognize aerodynamics parameters of the shape. Analysis results in the values of coefficients and aerodynamic drag forces. The resulting drag forces Fx, drag coefficients Cx(Cd) and aerodynamic factors Cx*A allowed to compare all of the shapes to each other. Pressure distribution, air velocities and streams courses were useful in determining aerodynamic features of analyzed shape. For aerodynamic tests was used Ansys Fluent CFD software. In a paper the ways of surface modeling with usage of Realize Shape module and classic surface modeling were presented. For shapes modeling Siemens NX 9.0 software was used. Obtained results were used to estimation of existing shapes and to make appropriate conclusions.

  8. Development of Nonlinear Aerodynamic Models for Unsteady Responses

    NASA Astrophysics Data System (ADS)

    Chin, Suei

    In the current study, a method based on Fourier analysis is developed to analyze the force and moment data obtained in large amplitude forced oscillation tests at high angles of attack. The aerodynamic models for normal force, lift, drag and pitching moment coefficients are built up from a set of aerodynamic responses to harmonic motions at different frequencies. Based on the aerodynamic models of harmonic data, the indicial responses are formed. The final expressions for the models involve time integrals of the indicial type advocated by Tobak and Schiff. Results from linear two- and three-dimensional unsteady aerodynamic theories as well as test data for a 70-deg delta wing are used to verify the models. It is shown that the present modeling method is accurate in producing the aerodynamic responses to harmonic motions and the ramp type motions. The model also produces correct trend for a 70-deg delta wing in harmonic motion with different mean angles-of-attack. However, the current model cannot be used to extrapolate data to higher angles-of-attack than that of the harmonic motions which form the aerodynamic model. For linear ramp motions, a special method is used to calculate the corresponding frequency and phase angle at a given time. The calculated results from modeling show higher lift peak for linear ramp motion than for harmonic ramp motion. The current model also shows reasonably good results for the lift responses at different mean angles of attack. To the author's knowledge, the current methodology of aerodynamic modeling is the first to produce the harmonic oscillation responses at high angle-of-attack and the ramp type motions.

  9. Separation and characterization of forced degradation products of abacavir sulphate by LC-MS/MS.

    PubMed

    Rao, R Nageswara; Vali, R Mastan; Ramachandra, Bondigalla; Raju, S Satyanarayana

    2011-01-25

    Abacavir sulphate was subjected to forced degradation under the conditions of hydrolysis (acid, alkali and neutral), oxidation, photolysis and thermal stress as prescribed by ICH. Eight degradation products were formed and their separation was accomplished on Waters XTerra C₁₈ (250 mm x 4.6 mm, 5 μm) column using 20 mM ammonium acetate:acetonitrile as a mobile phase in gradient elution mode by LC. The degradation products were characterized by LC-MS/MS and its fragmentation pathways were proposed. No previous reports were found in the literature regarding the degradation behavior of abacavir sulphate.

  10. Unsteady Aerodynamic Flow Control of a Suspended Axisymmetric Moving Platform

    NASA Astrophysics Data System (ADS)

    Lambert, Thomas; Vukasinovic, Bojan; Glezer, Ari

    2011-11-01

    The aerodynamic forces on an axisymmetric wind tunnel model are altered by fluidic interaction of an azimuthal array of integrated synthetic jet actuators with the cross flow. Four-quadrant actuators are integrated into a Coanda surface on the aft section of the body, and the jets emanate from narrow, azimuthally segmented slots equally distributed around the model's perimeter. The model is suspended in the tunnel using eight wires each comprising miniature in-line force sensors and shape-memory-alloy (SMA) strands that are used to control the instantaneous forces and moments on the model and its orientation. The interaction of the actuation jets with the flow over the moving model is investigated using PIV and time-resolved force measurements to assess the transitory aerodynamic loading effected by coupling between the induced motion of the aerodynamic surface and the fluid dynamics that is driven by the actuation. It is shown that these interactions can lead to effective control of the aerodynamic forces and moments, and thereby of the model's motion. Supported by ARO.

  11. Elastic deformation effects on aerodynamic characteristics for a high-aspect-ratio supercritical-wing model

    NASA Technical Reports Server (NTRS)

    Watson, J. J.

    1982-01-01

    The results of an investigation of the deformations of a high-aspect-ratio, force/pressure, supercritical-wing model during wind tunnel tests and the effects these deformations have on the wing aerodynamics are presented. A finite element model of the wing was developed, and then, for conditions corresponding to wind tunnel test points, experimental aerodynamic loads and theoretical aerodynamic loads were applied to the finite element model. Comparisons were made between the results of these load conditions for changes in structural deflections and for changes in aerodynamic characteristics. The results show that the deformations are quite small and that the pressure data are not significantly affected by model deformation.

  12. The sources of two components of variance: An example of multifinger cyclic force production tasks at different frequencies

    PubMed Central

    Friedman, Jason; Skm, Varadhan; Zatsiorsky, Vladimir M.; Latash, Mark L.

    2009-01-01

    In a multifinger cyclic force production task, the finger force variance measured across trials can be decomposed into two components, one that affects the combined force output (“bad variance”), and one that does not (“good variance”). Previous studies have found similar time patterns of “bad variance” and force rate leading to an approximately linear relationship between them. Based on this finding and a recently developed model of multifinger force production, we expected the “bad variance” during cyclic force production to increase monotonically with the rate of force change, both within-a-cycle, and across trials at different frequencies. Alternatively, “bad variance” could show a dependence on task frequency, not on actual force derivative values. Healthy subjects were required to produce cyclic force patterns to prescribed targets by pressing on unidimensional force sensors, at a frequency set by a metronome. The task was performed with only the index finger, and with all four fingers. In the task with all four fingers, the “good variance” increased approximately linearly with an increase in the force magnitude. The “bad variance” showed within-a-cycle modulation similar to that of the force rate. However, an increase in the frequency did not lead to an increase in the “bad variance” that could be expected based on the natural relationships between action frequency and the rate of force change modulation. The results have been interpreted in the framework of an earlier model of multifinger force production where “bad variance” is a result of variance of the timing parameter. The unexpected lack of modulation of the “bad variance” with frequency suggests a drop in variance of the timing parameter with increased frequency. This mechanism may serve to maintain a constant acceptable level of variance under different conditions. PMID:19468721

  13. Aerodynamic performance of membrane wings with adaptive compliance

    NASA Astrophysics Data System (ADS)

    Curet, Oscar M.; Carrere, Alexander; Pande, Arjun; Breuer, Kenneth S.

    2012-11-01

    Some flying animals use wing membranes with adaptive compliance to control their aerodynamic performance. In this work we characterize the mechanical properties and aerodynamic performance of a low aspect ratio membrane wing composed of a dielectric film supported on a rigid frame. We test the wing model in a wind tunnel. When a fixed voltage is applied across the wing membrane the camber increases, accompanied by a small increase in lift (less than 2%). However, lift is significantly increased when the wing is forced with an oscillating field at specific frequencies that correspond to the characteristic vortex shedding frequency. We present the results concerning the kinematics and aerodynamic performance of the adaptive wing membrane and the coupling between the vortex shedding and the forced modulation of elastic modulus.

  14. Impact of Short-Range Forces on Defect Production from High-Energy Collisions.

    PubMed

    Stoller, R E; Tamm, A; Béland, L K; Samolyuk, G D; Stocks, G M; Caro, A; Slipchenko, L V; Osetsky, Yu N; Aabloo, A; Klintenberg, M; Wang, Y

    2016-06-14

    Primary radiation damage formation in solid materials typically involves collisions between atoms that have up to a few hundred keV of kinetic energy. During these collisions, the distance between two colliding atoms can approach 0.05 nm. At such small atomic separations, force fields fitted to equilibrium properties tend to significantly underestimate the potential energy of the colliding dimer. To enable molecular dynamics simulations of high-energy collisions, it is common practice to use a screened Coulomb force field to describe the interactions and to smoothly join this to the equilibrium force field at a suitable interatomic spacing. However, there is no accepted standard method for choosing the parameters used in the joining process, and our results prove that defect production is sensitive to how the force fields are linked. A new procedure is presented that involves the use of ab initio calculations to determine the magnitude and spatial dependence of the pair interactions at intermediate distances, along with systematic criteria for choosing the joining parameters. Results are presented for the case of nickel, which demonstrate the use and validity of the procedure. PMID:27110927

  15. Impact of Short-Range Forces on Defect Production from High-Energy Collisions

    DOE PAGES

    Stoller, R. E.; Tamm, A.; Béland, L. K.; Samolyuk, G. D.; Stocks, G. M.; Caro, A.; Slipchenko, L. V.; Osetsky, Yu. N.; Aabloo, A.; Klintenberg, M.; et al

    2016-04-25

    Primary radiation damage formation in solid materials typically involves collisions between atoms that have up to a few hundred keV of kinetic energy. The distance between two colliding atoms can approach 0.05 nm during these collisions. At such small atomic separations, force fields fitted to equilibrium properties tend to significantly underestimate the potential energy of the colliding dimer. To enable molecular dynamics simulations of high-energy collisions, it is common practice to use a screened Coulomb force field to describe the interactions and to smoothly join this to the equilibrium force field at a suitable interatomic spacing. But, there is nomore » accepted standard method for choosing the parameters used in the joining process, and our results prove that defect production is sensitive to how the force fields are linked. A new procedure is presented that involves the use of ab initio calculations to determine the magnitude and spatial dependence of the pair interactions at intermediate distances, along with systematic criteria for choosing the joining parameters. Results are presented for the case of nickel, which demonstrate the use and validity of the procedure.« less

  16. TMS reveals a direct influence of spinal projections from human SMAp on precise force production.

    PubMed

    Entakli, Jonathan; Bonnard, Mireille; Chen, Sophie; Berton, Eric; De Graaf, Jozina B

    2014-01-01

    The corticospinal (CS) system plays an important role in fine motor control, especially in precision grip tasks. Although the primary motor cortex (M1) is the main source of the CS projections, other projections have been found, especially from the supplementary motor area proper (SMAp). To study the characteristics of these CS projections from SMAp, we compared muscle responses of an intrinsic hand muscle (FDI) evoked by stimulation of human M1 and SMAp during an isometric static low-force control task. Subjects were instructed to maintain a small cursor on a target force curve by applying a pressure with their right precision grip on a force sensor. Neuronavigated transcranial magnetic stimulation was used to stimulate either left M1 or left SMAp with equal induced electric field values at the defined cortical targets. The results show that the SMAp stimulation evokes reproducible muscle responses with similar latencies and amplitudes as M1 stimulation, and with a clear and significant shorter silent period. These results suggest that (i) CS projections from human SMAp are as rapid and efficient as those from M1, (ii) CS projections from SMAp are directly involved in control of the excitability of spinal motoneurons and (iii) SMAp has a different intracortical inhibitory circuitry. We conclude that human SMAp and M1 both have direct influence on force production during fine manual motor tasks. PMID:24164635

  17. Flow Modulation and Force Control in Insect Fast Maneuver

    NASA Astrophysics Data System (ADS)

    Li, Chengyu; Dong, Haibo; Zhang, Wen; Gai, Kuo

    2012-11-01

    In this work, an integrated study combining high-speed photogrammetry and direct numerical simulation (DNS) is used to study free flying insects in fast maneuver. Quantitative measurement has shown the significant differences between quad-winged flyers such as dragonfly and damselfly and two-winged flyers such as cicada. Comparisons of unsteady 3D vortex formation and associated aerodynamic force production reveal the different mechanisms used by insects in fast turn. This work is supported by NSF CBET-1055949.

  18. Supersonic Aerodynamic Characteristics of Blunt Body Trim Tab Configurations

    NASA Technical Reports Server (NTRS)

    Korzun, Ashley M.; Murphy, Kelly J.; Edquist, Karl T.

    2013-01-01

    Trim tabs are aerodynamic control surfaces that can allow an entry vehicle to meet aerodynamic performance requirements while reducing or eliminating the use of ballast mass and providing a capability to modulate the lift-to-drag ratio during entry. Force and moment data were obtained on 38 unique, blunt body trim tab configurations in the NASA Langley Research Center Unitary Plan Wind Tunnel. The data were used to parametrically assess the supersonic aerodynamic performance of trim tabs and to understand the influence of tab area, cant angle, and aspect ratio. Across the range of conditions tested (Mach numbers of 2.5, 3.5, and 4.5; angles of attack from -4deg to +20deg; angles of sideslip from 0deg to +8deg), the effects of varying tab area and tab cant angle were found to be much more significant than effects from varying tab aspect ratio. Aerodynamic characteristics exhibited variation with Mach number and forebody geometry over the range of conditions tested. Overall, the results demonstrate that trim tabs are a viable approach to satisfy aerodynamic performance requirements of blunt body entry vehicles with minimal ballast mass. For a 70deg sphere-cone, a tab with 3% area of the forebody and canted approximately 35deg with no ballast mass was found to give the same trim aerodynamics as a baseline model with ballast mass that was 5% of the total entry mass.

  19. Supersonic Flight Dynamics Test: Trajectory, Atmosphere, and Aerodynamics Reconstruction

    NASA Technical Reports Server (NTRS)

    Kutty, Prasad; Karlgaard, Christopher D.; Blood, Eric M.; O'Farrell, Clara; Ginn, Jason M.; Shoenenberger, Mark; Dutta, Soumyo

    2015-01-01

    The Supersonic Flight Dynamics Test is a full-scale flight test of a Supersonic Inflatable Aerodynamic Decelerator, which is part of the Low Density Supersonic Decelerator technology development project. The purpose of the project is to develop and mature aerodynamic decelerator technologies for landing large mass payloads on the surface of Mars. The technologies include a Supersonic Inflatable Aerodynamic Decelerator and Supersonic Parachutes. The first Supersonic Flight Dynamics Test occurred on June 28th, 2014 at the Pacific Missile Range Facility. This test was used to validate the test architecture for future missions. The flight was a success and, in addition, was able to acquire data on the aerodynamic performance of the supersonic inflatable decelerator. This paper describes the instrumentation, analysis techniques, and acquired flight test data utilized to reconstruct the vehicle trajectory, atmosphere, and aerodynamics. The results of the reconstruction show significantly higher lofting of the trajectory, which can partially be explained by off-nominal booster motor performance. The reconstructed vehicle force and moment coefficients fall well within pre-flight predictions. A parameter identification analysis indicates that the vehicle displayed greater aerodynamic static stability than seen in pre-flight computational predictions and ballistic range tests.

  20. The Aerodynamics of a Flying Sports Disc

    NASA Astrophysics Data System (ADS)

    Potts, Jonathan R.; Crowther, William J.

    2001-11-01

    The flying sports disc is a spin-stabilised axi-symmetric wing of quite remarkable design. A typical disc has an approximate elliptical cross-section and hollowed out under-side cavity, such as the Frisbee(TM) disc. An experimental study of flying disc aerodynamics, including both spinning and non-spinning tests, has been carried out in the wind tunnel. Load measurements, pressure data and flow visualisation techniques have enabled an explanation of the flow physics and provided data for free-flight simulations. A computer simulation that predicts free-flight trajectories from a given set of initial conditions was used to investigate the dynamics of a flying disc. This includes a six-degree of freedom mathematical model of disc flight mechanics, with aerodynamic coefficients derived from experimental data. A flying sports disc generates lift through forward velocity just like a conventional wing. The lift contributed by spin is insignificant and does not provide nearly enough down force to support hover. Without spin, the disc tumbles ground-ward under the influence of an unstable aerodynamic pitching moment. From a backhand throw however, spin is naturally given to the disc. The unchanged pitching moment now results in roll, due to gyroscopic precession, stabilising the disc in free-flight.

  1. Unconventional entropy production in the presence of momentum-dependent forces

    NASA Astrophysics Data System (ADS)

    Kwon, Chulan; Yeo, Joonhyun; Lee, Hyun Keun; Park, Hyunggyu

    2016-03-01

    We investigate the unconventional nature of entropy production (EP) in nonequilibrium systems with odd-parity variables that change signs under time reversal. We consider the Brownian motion of a particle in contact with a heat reservoir, where the particle's momentum is an odd-parity variable. In the presence of an external momentum-dependent force, the EP transferred to the environment is found to be not equivalent to the usual reservoir entropy change due to heat transfer. An additional unconventional contribution to the EP, which is crucial for maintaining the non-negativity of the (average) total EP enforced by the second law of thermodynamics, appears. A few examples are considered to elucidate the novel nature of the EP. We also discuss detailed balance conditions with a momentum-dependent force.

  2. The interference aerodynamics caused by the wing elasticity during store separation

    NASA Astrophysics Data System (ADS)

    Lei, Yang; Zheng-yin, Ye

    2016-04-01

    Air-launch-to-orbit is the technology that has stores carried aloft and launched the store from the plane to the orbit. The separation between the aircraft and store is one of the most important and difficult phases in air-launch-to-orbit technology. There exists strong aerodynamic interference between the aircraft and the store in store separation. When the aspect ratio of the aircraft is large, the elastic deformations of the wing must be considered. The main purpose of this article is to study the influence of the interference aerodynamics caused by the elastic deformations of the wing to the unsteady aerodynamics of the store. By solving the coupled functions of unsteady Navier-Stokes equations, six degrees of freedom dynamic equations and structural dynamic equations simultaneously, the store separation with the elastic deformation of the aircraft considered is simulated numerically. And the interactive aerodynamic forces are analyzed. The study shows that the interference aerodynamics is obvious at earlier time during the separation, and the dominant frequency of the elastic wing determines the aerodynamic forces frequencies of the store. Because of the effect of the interference aerodynamics, the roll angle response and pitch angle response increase. When the store is mounted under the wingtip, the additional aerodynamics caused by the wingtip vortex is obvious, which accelerate the divergence of the lateral force and the lateral-directional attitude angle of the store. This study supports some beneficial conclusions to the engineering application of the air-launch-to-orbit.

  3. The Aerodynamic Plane Table

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1924-01-01

    This report gives the description and the use of a specially designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory, and for miscellaneous truing operations, there is frequent need for a specially equipped plan table. For example, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets of a strut, airship hull, or other carefully formed figure may require exact calipering. Again, a complete airplane model may have to be adjusted for correct incidence at all parts of its surfaces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on a planing or milling machine; but if frequent, justifies the provision of a special table. For this reason it was found desirable in 1918 to make the table described in this report and to equip it with such gauges and measures as the work should require.

  4. Aerodynamic design using numerical optimization

    NASA Technical Reports Server (NTRS)

    Murman, E. M.; Chapman, G. T.

    1983-01-01

    The procedure of using numerical optimization methods coupled with computational fluid dynamic (CFD) codes for the development of an aerodynamic design is examined. Several approaches that replace wind tunnel tests, develop pressure distributions and derive designs, or fulfill preset design criteria are presented. The method of Aerodynamic Design by Numerical Optimization (ADNO) is described and illustrated with examples.

  5. Aerodynamic coefficients and transformation tables

    NASA Technical Reports Server (NTRS)

    Ames, Joseph S

    1918-01-01

    The problem of the transformation of numerical values expressed in one system of units into another set or system of units frequently arises in connection with aerodynamic problems. Report contains aerodynamic coefficients and conversion tables needed to facilitate such transformation. (author)

  6. Sensor Systems Collect Critical Aerodynamics Data

    NASA Technical Reports Server (NTRS)

    2010-01-01

    With the support of Small Business Innovation Research (SBIR) contracts with Dryden Flight Research Center, Tao of Systems Integration Inc. developed sensors and other components that will ultimately form a first-of-its-kind, closed-loop system for detecting, measuring, and controlling aerodynamic forces and moments in flight. The Hampton, Virginia-based company commercialized three of the four planned components, which provide sensing solutions for customers such as Boeing, General Electric, and BMW and are used for applications such as improving wind turbine operation and optimizing air flow from air conditioning systems. The completed system may one day enable flexible-wing aircraft with flight capabilities like those of birds.

  7. Effects of resistance training on tendon mechanical properties and rapid force production in prepubertal children

    PubMed Central

    Waugh, C. M.; Korff, T.; Fath, F.

    2014-01-01

    Children develop lower levels of muscle force, and at slower rates, than adults. Although strength training in children is expected to reduce this differential, a synchronous adaptation in the tendon must be achieved to ensure forces continue to be transmitted to the skeleton with efficiency while minimizing the risk of strain-related tendon injury. We hypothesized that resistance training (RT) would alter tendon mechanical properties in children concomitantly with changes in force production characteristics. Twenty prepubertal children (age 8.9 ± 0.3 yr) were equally divided into control (nontraining) and experimental (training) groups. The training group completed a 10-wk RT intervention consisting of 2–3 sets of 8–15 plantar flexion contractions performed twice weekly on a recumbent calf-raise machine. Achilles tendon properties (cross-sectional area, elongation, stress, strain, stiffness, and Young's modulus), electromechanical delay (EMD; time between the onset of muscle activity and force), rate of force development (RFD; slope of the force-time curve), and rate of electromyographic (EMG) increase (REI; slope of the EMG time curve) were measured before and after RT. Tendon stiffness and Young's modulus increased significantly after RT in the experimental group only (∼29% and ∼25%, respectively); all other tendon properties were not significantly altered, although there were mean decreases in both peak tendon strain and strain at a given force level (14% and 24%, respectively; not significant) which may have implications for tendon injury risk and muscle fiber mechanics. A decrease of ∼13% in EMD was found after RT for the experimental group, which paralleled the increase in tendon stiffness (r = −0.59); however, RFD and REI were unchanged. The present data show that the Achilles tendon adapts to RT in prepubertal children and is paralleled by a change in EMD, although the magnitude of this change did not appear to be sufficient to influence RFD

  8. 26. VIEW OF EXHAUST AND DEFLECTOR FOR SUBSONIC AERODYNAMICS RESEARCH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    26. VIEW OF EXHAUST AND DEFLECTOR FOR SUBSONIC AERODYNAMICS RESEARCH LABORATORY, BUILDING 25C, WHICH REPLACED THE 10-FOOT WIND TUNNEL (1991). - Wright-Patterson Air Force Base, Area B, Buildings 25 & 24,10-foot & 20-foot Wind Tunnel Complex, Northeast side of block bounded by K, G, Third, & Fifth Streets, Dayton, Montgomery County, OH

  9. 28. VIEW OF EXHAUST AND DEFLECTOR FOR SUBSONIC AERODYNAMICS RESEARCH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. VIEW OF EXHAUST AND DEFLECTOR FOR SUBSONIC AERODYNAMICS RESEARCH LABORATORY, BUILDING 25C, WHICH REPLACED THE 10-FOOT WIND TUNNEL (1991). - Wright-Patterson Air Force Base, Area B, Buildings 25 & 24,10-foot & 20-foot Wind Tunnel Complex, Northeast side of block bounded by K, G, Third, & Fifth Streets, Dayton, Montgomery County, OH

  10. 27. VIEW OF EXHAUST AND DEFLECTOR FOR SUBSONIC AERODYNAMICS RESEARCH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. VIEW OF EXHAUST AND DEFLECTOR FOR SUBSONIC AERODYNAMICS RESEARCH LABORATORY, BUILDING 25C, WHICH REPLACED THE 10-FOOT WIND TUNNEL (1991). - Wright-Patterson Air Force Base, Area B, Buildings 25 & 24,10-foot & 20-foot Wind Tunnel Complex, Northeast side of block bounded by K, G, Third, & Fifth Streets, Dayton, Montgomery County, OH

  11. Unsteady aerodynamics of blade rows

    NASA Technical Reports Server (NTRS)

    Verdon, Joseph M.

    1989-01-01

    The requirements placed on an unsteady aerodynamic theory intended for turbomachinery aeroelastic or aeroacoustic applications are discussed along with a brief description of the various theoretical models that are available to address these requirements. The major emphasis is placed on the description of a linearized inviscid theory which fully accounts for the affects of a nonuniform mean or steady flow on unsteady aerodynamic response. Although this linearization was developed primarily for blade flutter prediction, more general equations are presented which account for unsteady excitations due to incident external aerodynamic disturbances as well as those due to prescribed blade motions. The motivation for this linearized unsteady aerodynamic theory is focused on, its physical and mathematical formulation is outlined and examples are presented to illustrate the status of numerical solution procedures and several effects of mean flow nonuniformity on unsteady aerodynamic response.

  12. 77 FR 70473 - Child Labor, Forced Labor, and Forced or Indentured Child Labor in the Production of Goods in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-26

    ... Child Labor, Forced Labor and Human Trafficking (OCFT) at the email or physical address below by 5 p.m... that ILAB follows in developing the TVPRA List (72 FR 73374). The guidelines set forth the criteria by.... List''), identified by country of origin, that the Department, in consultation and cooperation with...

  13. 75 FR 8402 - Child Labor, Forced Labor, and Forced or Indentured Child Labor in the Production of Goods in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... goods (72 FR 73374). The guidelines set forth the criteria by which information is evaluated... believe might have been mined, produced or manufactured with forced or indentured child labor (66 FR 5353... appropriate, revising the List (66 FR 5351). Based on DOL research and information submitted by the...

  14. Predictions of wing and pylon forces caused by propeller installation

    NASA Technical Reports Server (NTRS)

    Martinez, Rudolph

    1987-01-01

    Replacement of current turbojets by high-efficiency unducted propfans could have the unfortunate side effect of increasing cabin noise, essentially because unsteady-aerodynamic mechanisms are likely to be introduced whereby some of the energy saved may be lost again, to the production of propeller noise and to wing/pylon vibrations coupling to the cabin as a sounding board. The present study estimates theoretically associated harmonic aerodynamic forces for two candidate configurations: a pusher propeller which chops through the mean wake of the pylon supporting it, and in the process generates a blade-rate force driving the structure, and a tractor wing-mounted propeller, whose trailing rotating wake induces an unsteady downwash field generating unsteady wing airloads. Reported predictions of such propfan aerodynamic sources of structure-borne sound, or vibration, could be the basis for devising means for their mechanical isolation, and thus for the effective interruption of the structural noise path into the cabin. Both mechanisms are analyzed taking advantage of the high subsonic Mach number and high reduced frequency of the interaction between the impinging flow and the affected aerodynamic element.

  15. Accomplishments at NASA Langley Research Center in rotorcraft aerodynamics technology

    NASA Technical Reports Server (NTRS)

    Wilson, John C.

    1988-01-01

    In recent years, the development of aerodynamic technology for rotorcraft has continued successfully at NASA LaRC. Though the NASA Langley Research Center is not the lead NASA center in this area, the activity was continued due to facilities and individual capabilities which are recognized as contributing to helicopter research needs of industry and government. Noteworthy accomplishments which contribute to advancing the state of rotorcraft technology in the areas of rotor design, airfoil research, rotor aerodynamics, and rotor/fuselage interaction aerodynamics are described. Rotor designs were defined for current helicopters and evaluated in wind tunnel testing. These designs have incorporated advanced airfoils defined analytically and also proven in wind tunnel tests. A laser velocimetry system has become a productive tool for experimental definition of rotor inflow/wake and is providing data for rotorcraft aerodynamic code validation.

  16. Entropy production for velocity-dependent macroscopic forces: The problem of dissipation without fluctuations

    NASA Astrophysics Data System (ADS)

    Cerino, L.; Puglisi, A.

    2015-08-01

    In macroscopic systems, velocity-dependent phenomenological forces F(v) are used to model friction, feedback devices or self-propulsion. Such forces usually include a dissipative component which conceals the fast energy exchanges with a thermostat at the environment temperature T, ruled by a microscopic Hamiltonian H. The mapping (H,T) \\to F(v) —even if effective for many purposes— may lead to applications of stochastic thermodynamics where an incomplete fluctuating entropy production (FEP) is derived. An enlighting example is offered by recent macroscopic experiments where dissipation is dominated by solid-on-solid friction, typically modelled through a deterministic Coulomb force F(v). Through an adaptation of the microscopic Prandtl-Tomlinson model for friction, we show how the FEP is dominated by the heat released to the T-thermostat, ignored by the macroscopic Coulomb model. This problem, which haunts several studies in the literature, cannot be cured by weighing the time-reversed trajectories with a different auxiliary dynamics: it is only solved by a more accurate stochastic modelling of the thermostat underlying dissipation.

  17. A theoretical note on aerodynamic lifting in dust devils

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Ting

    2016-02-01

    The stress distribution of a known rotating flow near the ground in fluid mechanics indicates that the horizontal aerodynamic entrainment of particles within dust devils is attributed to friction force rather than pressure force. The expression of dust emission rate on Earth was theoretically discussed based on simulated flow field and our current understanding of the physics of aeolian dust. It seems that transition flow is vital to dust devils on Mars.

  18. An aerodynamic model for a hemispherically-capped biconic reentry vehicle with six drag flaps

    SciTech Connect

    Jordan, T.M.; Buffington, R.J.

    1987-01-01

    The development of an aerodynamic model for a hemispherically-capped biconic reentry vehicle with six drag flaps is presented. The aerodynamic model is primarily based on wind tunnel test results, with the use of computational fluid dynamic codes. For Mach numbers from 4 to 15, the inviscid axial force coefficient was computed for drag flap deflections from 6 to 36. Axial force coefficient was found to vary significantly with ablating flap shape as well as with changing flight conditions. The aerodynamic model can be used for input to vehicle recovery trajectory simulations.

  19. Investigation of the transient aerodynamic phenomena associated with passing manoeuvres

    NASA Astrophysics Data System (ADS)

    Noger, C.; Regardin, C.; Széchényi, E.

    2005-11-01

    Passing manoeuvres and crosswind can have significant effects on the stability of road vehicles. The transient aerodynamics, which interacts with suspension, steering geometry and driver reaction is not well understood. When two vehicles overtake or cross, they mutually influence the flow field around each other, and under certain conditions, can generate severe gust loads that act as additional forces on both vehicles. The transient forces acting on them are a function of the longitudinal and transverse spacings and of the relative velocity between the two vehicles. Wind tunnel experiments have been conducted in one of the automotive wind tunnels of the Institut Aérotechnique of Saint-Cyr l’École to simulate the transient overtaking process between two models of a simple generic automobile shape. The tests were designed to study the effects of various parameters such as the longitudinal and transverse spacing, the relative velocity and the crosswind on the aerodynamic forces and moments generated on the overtaken and overtaking vehicles. Test results characterize the transient aerodynamic side force as well as the yawing moment coefficients in terms of these parameters. Measurements of the drag force coefficient as well as the static pressure distribution around the overtaken vehicle complete the understanding. The main results indicate the aerodynamic coefficients of the overtaken vehicle to be velocity independent within the limit of the test parameters, while unsteady aerodynamic effects appear in the case of an overtaking vehicle. The mutual interference effects between the vehicles vary as a linear function of the transverse spacing and the crosswind does not really generate any new unsteady behaviour.

  20. Application of a one-strip integral method to the unsteady supersonic aerodynamics of an inclined flat surface

    NASA Technical Reports Server (NTRS)

    Bennett, R. M.

    1972-01-01

    The method of integral relations is applied in a one-strip approximation to the perturbation equations governing small motions of an inclined, sharp-edged, flat surface about the mean supersonic steady flow. Algebraic expressions for low reduced-frequency aerodynamics are obtained and a set of ordinary differential equations are obtained for general oscillatory motion. Results are presented for low reduced-frequency aerodynamics and for the variation of the unsteady forces with frequency. The method gives accurate results for the aerodynamic forces at low reduced frequency which are in good agreement with available experimental data. However, for cases in which the aerodynamic forces vary rapidly with frequency, the results are qualitatively correct, but of limited accuracy. Calculations indicate that for a range of inclination angles near shock detachment such that the flow in the shock layer is low supersonic, the aerodynamic forces vary rapidly both with inclination angle and with reduced frequency.

  1. Effects of aerodynamic lift on the stability of tethered subsatellite system

    NASA Astrophysics Data System (ADS)

    Keshmiri, Mehdi; Misra, Arun K.

    Dynamics and stability of a two-body tethered system are investigated considering the aerodynamic lift on the subsatellite in addition to he aerodynamic drag. The Free Molecular Flow Model is used to calculate the aerodynamic forces on the subsatellite. Equilibrium configurations of the system are obtained numerically. Equations of motion are linearized analytically about the equilibrium configuration through a symbolic manipulation language, Maple V., and stability behavior of small oscillations about the equilibrium configuration is analyzed. An extensive parametric study is done to understand the effect of aerodynamic forces (lift and drag) on the stability of the uncontrolled system. It is shown that the stability behavior changes significantly if the subsatellite is changed from a body with no lift to a body with lift. Hence, an unstable system with a spherical subsatellite can be stabilized if aerodynamic surfaces are appropriately added. It is concluded that consideration of the aerodynamic lifting forces in addition to the aerodynamic drag forces on the subsatellite is indispensible for proper design of a tethered subsatellite system deployed in a low-altitude orbit.

  2. High speed civil transport aerodynamic optimization

    NASA Technical Reports Server (NTRS)

    Ryan, James S.

    1994-01-01

    This is a report of work in support of the Computational Aerosciences (CAS) element of the Federal HPCC program. Specifically, CFD and aerodynamic optimization are being performed on parallel computers. The long-range goal of this work is to facilitate teraflops-rate multidisciplinary optimization of aerospace vehicles. This year's work is targeted for application to the High Speed Civil Transport (HSCT), one of four CAS grand challenges identified in the HPCC FY 1995 Blue Book. This vehicle is to be a passenger aircraft, with the promise of cutting overseas flight time by more than half. To meet fuel economy, operational costs, environmental impact, noise production, and range requirements, improved design tools are required, and these tools must eventually integrate optimization, external aerodynamics, propulsion, structures, heat transfer, controls, and perhaps other disciplines. The fundamental goal of this project is to contribute to improved design tools for U.S. industry, and thus to the nation's economic competitiveness.

  3. Muscle force production during bent-knee, bent-hip walking in humans.

    PubMed

    Foster, Adam D; Raichlen, David A; Pontzer, Herman

    2013-09-01

    Researchers have long debated the locomotor posture used by the earliest bipeds. While many agree that by 3-4 Ma (millions of years ago), hominins walked with an extended-limb human style of bipedalism, researchers are still divided over whether the earliest bipeds walked like modern humans, or walked with a more bent-knee, bent-hip (BKBH) ape-like form of locomotion. Since more flexed postures are associated with higher energy costs, reconstructing early bipedal mechanics has implications for the selection pressures that led to upright walking. The purpose of this study is to determine how modern human anatomy functions in BKBH walking to clarify the links between morphology and energy costs in different mechanical regimes. Using inverse dynamics, we calculated muscle force production at the major limb joints in humans walking in two modes, both with extended limbs and BKBH. We found that in BKBH walking, humans must produce large muscle forces at the knee to support body weight, leading to higher estimated energy costs. However, muscle forces at the hip remained similar in BKBH and extended limb walking, suggesting that anatomical adaptations for hip extension in humans do not necessarily diminish the effective mechanical advantage at the hip in more flexed postures. We conclude that the key adaptations for economical walking, regardless of joint posture, seem to center on maintaining low muscle forces at the hip, primarily by keeping low external moments at the hip. We explore the implications of these results for interpreting locomotor energetics in early hominins, including australopithecines and Ardipithecus ramidus. PMID:23928351

  4. Force-production asymmetry in male and female athletes of differing strength levels.

    PubMed

    Bailey, Christopher A; Sato, Kimitake; Burnett, Angus; Stone, Michael H

    2015-05-01

    The purpose of this investigation was to determine the existence of bilateral strength and force-production asymmetry and evaluate possible differences based on sex, as well as strength level. Asymmetry was assessed during weight-distribution (WtD) testing, unloaded and lightly loaded static- (SJ) and countermovement-jump (CMJ) testing, and isometric midthigh-pull (IMTP) strength testing. Subjects included 63 athletes (31 male, 32 female) for WtD, SJ, and CMJ tests, while 129 athletes (64 male, 65 female) participated in IMTP testing. Independent-samples t tests were used to determine possible differences in asymmetry magnitude between males and females, as well as between strong and weak athletes. Cohen d effect-size (ES) estimates were also used to estimate difference magnitudes. Statistically different asymmetry levels with moderate to strong ESs were seen between males and females in WtD, 0-kg SJ (peak force [PF]), 20-kg SJ (peak power [PP]), 0-kg CMJ (PF, PP, net impulse), and 20-kg CMJ (PF), but no statistical differences were observed in IMTP variables. Dividing the sample into strong and weak groups produced statistically significant differences with strong ES estimates in IMTP PF and rate of force development, and many ESs in jump symmetry variables increased. The results of this investigation indicate that females may be more prone to producing forces asymmetrically than males during WtD and jumping tasks. Similarly, weaker athletes displayed more asymmetry than stronger athletes. This may indicate that absolute strength may play a larger role in influencing asymmetry magnitude than sex. PMID:25394294

  5. Muscle force production during bent-knee, bent-hip walking in humans.

    PubMed

    Foster, Adam D; Raichlen, David A; Pontzer, Herman

    2013-09-01

    Researchers have long debated the locomotor posture used by the earliest bipeds. While many agree that by 3-4 Ma (millions of years ago), hominins walked with an extended-limb human style of bipedalism, researchers are still divided over whether the earliest bipeds walked like modern humans, or walked with a more bent-knee, bent-hip (BKBH) ape-like form of locomotion. Since more flexed postures are associated with higher energy costs, reconstructing early bipedal mechanics has implications for the selection pressures that led to upright walking. The purpose of this study is to determine how modern human anatomy functions in BKBH walking to clarify the links between morphology and energy costs in different mechanical regimes. Using inverse dynamics, we calculated muscle force production at the major limb joints in humans walking in two modes, both with extended limbs and BKBH. We found that in BKBH walking, humans must produce large muscle forces at the knee to support body weight, leading to higher estimated energy costs. However, muscle forces at the hip remained similar in BKBH and extended limb walking, suggesting that anatomical adaptations for hip extension in humans do not necessarily diminish the effective mechanical advantage at the hip in more flexed postures. We conclude that the key adaptations for economical walking, regardless of joint posture, seem to center on maintaining low muscle forces at the hip, primarily by keeping low external moments at the hip. We explore the implications of these results for interpreting locomotor energetics in early hominins, including australopithecines and Ardipithecus ramidus.

  6. Aerodynamics of Small Vehicles

    NASA Astrophysics Data System (ADS)

    Mueller, Thomas J.

    In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.

  7. Reciprocity relations in aerodynamics

    NASA Technical Reports Server (NTRS)

    Heaslet, Max A; Spreiter, John R

    1953-01-01

    Reverse flow theorems in aerodynamics are shown to be based on the same general concepts involved in many reciprocity theorems in the physical sciences. Reciprocal theorems for both steady and unsteady motion are found as a logical consequence of this approach. No restrictions on wing plan form or flight Mach number are made beyond those required in linearized compressible-flow analysis. A number of examples are listed, including general integral theorems for lifting, rolling, and pitching wings and for wings in nonuniform downwash fields. Correspondence is also established between the buildup of circulation with time of a wing starting impulsively from rest and the buildup of lift of the same wing moving in the reverse direction into a sharp-edged gust.

  8. Vortex flow aerodynamics

    NASA Technical Reports Server (NTRS)

    Smith, J. H. B.; Campbell, J. F.; Young, A. D. (Editor)

    1992-01-01

    The principal emphasis of the meeting was to be on the understanding and prediction of separation-induced vortex flows and their effects on vehicle performance, stability, control, and structural design loads. This report shows that a substantial amount of the papers covering this area were received from a wide range of countries, together with an attendance that was even more diverse. In itself, this testifies to the current interest in the subject and to the appropriateness of the Panel's choice of topic and approach. An attempt is made to summarize each paper delivered, and to relate the contributions made in the papers and in the discussions to some of the important aspects of vortex flow aerodynamics. This reveals significant progress and important clarifications, but also brings out remaining weaknesses in predictive capability and gaps in understanding. Where possible, conclusions are drawn and areas of continuing concern are identified.

  9. Cruise aerodynamics of USB nacelle/wing geometric variations

    NASA Technical Reports Server (NTRS)

    Braden, J. A.; Hancock, J. P.; Burdges, K. P.

    1976-01-01

    Experimental results are presented on aerodynamic effects of geometric variations in upper surface blown nacelle configurations at high speed cruise conditions. Test data include both force and pressure measurements on two and three dimensional models powered by upper surface blowing nacelles of varying geometries. Experimental results are provided on variations in nozzle aspect ratio, nozzle boattail angle, and multiple nacelle installations. The nacelles are ranked according to aerodynamic drag penalties as well as overall installed drag penalties. Sample effects and correlations are shown for data obtained with the pressure model.

  10. An Improved Theoretical Aerodynamic Derivatives Computer Program for Sounding Rockets

    NASA Technical Reports Server (NTRS)

    Barrowman, J. S.; Fan, D. N.; Obosu, C. B.; Vira, N. R.; Yang, R. J.

    1979-01-01

    The paper outlines a Theoretical Aerodynamic Derivatives (TAD) computer program for computing the aerodynamics of sounding rockets. TAD outputs include normal force, pitching moment and rolling moment coefficient derivatives as well as center-of-pressure locations as a function of the flight Mach number. TAD is applicable to slender finned axisymmetric vehicles at small angles of attack in subsonic and supersonic flows. TAD improvement efforts include extending Mach number regions of applicability, improving accuracy, and replacement of some numerical integration algorithms with closed-form integrations. Key equations used in TAD are summarized and typical TAD outputs are illustrated for a second-stage Tomahawk configuration.

  11. Force-dependent and force-independent heat production in single slow- and fast-twitch muscle fibres from Xenopus laevis.

    PubMed Central

    Buschman, H P; van der Laarse, W J; Stienen, G J; Elzinga, G

    1996-01-01

    1. The origin of labile heat production, i.e. a heat component which rapidly decays after the onset of stimulation, and of stable (maintenance) heat production was investigated in intact single fast-twitch (type 1) and slow-twitch (type 3) iliofibularis muscle fibres from Xenopus laevis, at 20 degrees C, by varying stimulation frequency and by varying sarcomere length and the concentration of 2,3-butanedione 2-monoxime (BDM) added. 2. The labile heat produced consisted of a force-independent and a force-dependent part. The average parvalbumin (PA) content found in type 1 fibre bundles (0.84 +/- 0.08 mM; mean +/- S.E.M.; n = 5) and in type 3 fibre bundles (0.12 +/- 0.02 mM; n = 5) indicates that the force-independent labile heat is explained by Ca(2+)-Mg2+ exchange on PA, and amounts to a molar enthalpy change of -78 kJ (molPA)-1. 3. Force-dependent labile heat during fused contractions was similar to the calculated heat production resulting from the formation of force-generating cross-bridges, assuming an enthalpy change associated with cross-bridge formation of -30 kJ mol-1. 4. Activation heat, i.e. the part of the total stable heat that is not related to the contractile apparatus, and of which the calcium sequestration by the sarcoplasmic reticulum is the most important contributor, determined by varying sarcomere length or BDM concentration, was identical. For fused contractions the fraction activation heat of the stable maintenance rate of heat production was 34 +/- 4% (mean +/- S.E.M.; n = 13) in type 1 fibres, and 52 +/- 4% (n = 15) in type 3 fibres. In unfused contractions this was 48 +/- 5% (n = 13) in type 1 fibres, and 35 +/- 2% (n = 11) in type 3 fibres. 5. From the force-dependent stable rate of heat production the economy of cross-bridge cycling, expressed as the force-time integral for a single myosin head per ATP molecule hydrolysed, was calculated. It followed that cross-bridge interaction in type 3 fibres is more economical than in type 1 fibres

  12. Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production

    PubMed Central

    Morin, Jean-Benoît; Gimenez, Philippe; Edouard, Pascal; Arnal, Pierrick; Jiménez-Reyes, Pedro; Samozino, Pierre; Brughelli, Matt; Mendiguchia, Jurdan

    2015-01-01

    Recent literature supports the importance of horizontal ground reaction force (GRF) production for sprint acceleration performance. Modeling and clinical studies have shown that the hip extensors are very likely contributors to sprint acceleration performance. We experimentally tested the role of the hip extensors in horizontal GRF production during short, maximal, treadmill sprint accelerations. Torque capabilities of the knee and hip extensors and flexors were assessed using an isokinetic dynamometer in 14 males familiar with sprint running. Then, during 6-s sprints on an instrumented motorized treadmill, horizontal and vertical GRF were synchronized with electromyographic (EMG) activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus averaged over the first half of support, entire support, entire swing and end-of-swing phases. No significant correlations were found between isokinetic or EMG variables and horizontal GRF. Multiple linear regression analysis showed a significant relationship (P = 0.024) between horizontal GRF and the combination of biceps femoris EMG activity during the end of the swing and the knee flexors eccentric peak torque. In conclusion, subjects who produced the greatest amount of horizontal force were both able to highly activate their hamstring muscles just before ground contact and present high eccentric hamstring peak torque capability. PMID:26733889

  13. Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production.

    PubMed

    Morin, Jean-Benoît; Gimenez, Philippe; Edouard, Pascal; Arnal, Pierrick; Jiménez-Reyes, Pedro; Samozino, Pierre; Brughelli, Matt; Mendiguchia, Jurdan

    2015-01-01

    Recent literature supports the importance of horizontal ground reaction force (GRF) production for sprint acceleration performance. Modeling and clinical studies have shown that the hip extensors are very likely contributors to sprint acceleration performance. We experimentally tested the role of the hip extensors in horizontal GRF production during short, maximal, treadmill sprint accelerations. Torque capabilities of the knee and hip extensors and flexors were assessed using an isokinetic dynamometer in 14 males familiar with sprint running. Then, during 6-s sprints on an instrumented motorized treadmill, horizontal and vertical GRF were synchronized with electromyographic (EMG) activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus averaged over the first half of support, entire support, entire swing and end-of-swing phases. No significant correlations were found between isokinetic or EMG variables and horizontal GRF. Multiple linear regression analysis showed a significant relationship (P = 0.024) between horizontal GRF and the combination of biceps femoris EMG activity during the end of the swing and the knee flexors eccentric peak torque. In conclusion, subjects who produced the greatest amount of horizontal force were both able to highly activate their hamstring muscles just before ground contact and present high eccentric hamstring peak torque capability.

  14. Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). II. Inertial and aerodynamic reorientation.

    PubMed

    Hedrick, T L; Usherwood, J R; Biewener, A A

    2007-06-01

    The reconfigurable, flapping wings of birds allow for both inertial and aerodynamic modes of reorientation. We found evidence that both these modes play important roles in the low speed turning flight of the rose-breasted cockatoo Eolophus roseicapillus. Using three-dimensional kinematics recorded from six cockatoos making a 90 degrees turn in a flight corridor, we developed predictions of inertial and aerodynamic reorientation from estimates of wing moments of inertia and flapping arcs, and a blade-element aerodynamic model. The blade-element model successfully predicted weight support (predicted was 88+/-17% of observed, N=6) and centripetal force (predicted was 79+/-29% of observed, N=6) for the maneuvering cockatoos and provided a reasonable estimate of mechanical power. The estimated torque from the model was a significant predictor of roll acceleration (r(2)=0.55, P<0.00001), but greatly overestimated roll magnitude when applied with no roll damping. Non-dimensional roll damping coefficients of approximately -1.5, 2-6 times greater than those typical of airplane flight dynamics (approximately -0.45), were required to bring our estimates of reorientation due to aerodynamic torque back into conjunction with the measured changes in orientation. Our estimates of inertial reorientation were statistically significant predictors of the measured reorientation within wingbeats (r(2) from 0.2 to 0.37, P<0.0005). Components of both our inertial reorientation and aerodynamic torque estimates correlated, significantly, with asymmetries in the activation profile of four flight muscles: the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis (r(2) from 0.27 to 0.45, P<0.005). Thus, avian flight maneuvers rely on production of asymmetries throughout the flight apparatus rather than in a specific set of control or turning muscles. PMID:17515417

  15. Description of a Computer Program Written for Approach and Landing Test Post Flight Data Extraction of Proximity Separation Aerodynamic Coefficients and Aerodynamic Data Base Verification

    NASA Technical Reports Server (NTRS)

    Homan, D. J.

    1977-01-01

    A computer program written to calculate the proximity aerodynamic force and moment coefficients of the Orbiter/Shuttle Carrier Aircraft (SCA) vehicles based on flight instrumentation is described. The ground reduced aerodynamic coefficients and instrumentation errors (GRACIE) program was developed as a tool to aid in flight test verification of the Orbiter/SCA separation aerodynamic data base. The program calculates the force and moment coefficients of each vehicle in proximity to the other, using the load measurement system data, flight instrumentation data and the vehicle mass properties. The uncertainty in each coefficient is determined, based on the quoted instrumentation accuracies. A subroutine manipulates the Orbiter/747 Carrier Separation Aerodynamic Data Book to calculate a comparable set of predicted coefficients for comparison to the calculated flight test data.

  16. Influences of aerodynamic loads on hunting stability of high-speed railway vehicles and parameter studies

    NASA Astrophysics Data System (ADS)

    Zeng, Xiao-Hui; Wu, Han; Lai, Jiang; Sheng, Hong-Zhi

    2014-12-01

    The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study. A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads: the aerodynamic loads can change the position of vehicle system (consequently the contact relations), the wheel/rail normal contact forces, the gravitational restoring forces/moments and the creep forces/moments. A mathematical model for hunting stability incorporating such influences was developed. A computer program capable of incorporating the effects of aerodynamic loads based on the model was written, and the critical speeds were calculated using this program. The dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method, the results were also compared with the situations without aerodynamic loads. It is shown that the most dominant factors affecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or not. The damping of yaw damper is the most dominant influencing factor for linear critical speeds, while the damping of lateral damper is most dominant for nonlinear ones. When the influences of aerodynamic loads are considered, the linear critical speeds decrease with the rise of crosswind velocity, whereas it is not the case for the nonlinear critical speeds. The variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic loads. Combined actions of aerodynamic loads and suspension parameters also affect the critical speeds. The effects of such joint action are more obvious for nonlinear critical speeds.

  17. Global Nonlinear Parametric Modeling with Application to F-16 Aerodynamics

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.

    1997-01-01

    A global nonlinear parametric modeling technique is described and demonstrated. The technique uses multivariate orthogonal modeling functions generated from the data to determine nonlinear model structure, then expands each retained modeling function into an ordinary multivariate polynomial. The final model form is a finite multivariate power series expansion for the dependent variable in terms of the independent variables. Partial derivatives of the identified models can be used to assemble globally valid linear parameter varying models. The technique is demonstrated by identifying global nonlinear parametric models for nondimensional aerodynamic force and moment coefficients from a subsonic wind tunnel database for the F-16 fighter aircraft. Results show less than 10% difference between wind tunnel aerodynamic data and the nonlinear parameterized model for a simulated doublet maneuver at moderate angle of attack. Analysis indicated that the global nonlinear parametric models adequately captured the multivariate nonlinear aerodynamic functional dependence.

  18. Global Nonlinear Parametric Modeling with Application to F-16 Aerodynamics

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.

    1998-01-01

    A global nonlinear parametric modeling technique is described and demonstrated. The technique uses multivariate orthogonal modeling functions generated from the data to determine nonlinear model structure, then expands each retained modeling function into an ordinary multivariate polynomial. The final model form is a finite multivariate power series expansion for the dependent variable in terms of the independent variables. Partial derivatives of the identified models can be used to assemble globally valid linear parameter varying models. The technique is demonstrated by identifying global nonlinear parametric models for nondimensional aerodynamic force and moment coefficients from a subsonic wind tunnel database for the F-16 fighter aircraft. Results show less than 10% difference between wind tunnel aerodynamic data and the nonlinear parameterized model for a simulated doublet maneuver at moderate angle of attack. Analysis indicated that the global nonlinear parametric models adequately captured the multivariate nonlinear aerodynamic functional dependence.

  19. An experimental study of an aerodynamically optimum windmill

    NASA Astrophysics Data System (ADS)

    Ishida, Y.; Toda, N.; Hoshino, H.; Noguchi, M.

    1982-08-01

    Aerodynamic characteristics of an optimum horizontal axis windmill are described. The windmill, rated at 20 KW at 8 m/s with a two bladed rotor of 14m diameter, is designed so as to vary the geometry of the blade in such a way that the aerodynamic efficiency becomes maximum. The combined blade element momentum theory is used as an analytical tool. To check the design method and get some useful aerodynamic data, a wind tunnel test of a 1/7th scale model (2m diameter) is performed in a low speed tunnel, whose test section is 35.75 sq m. Two models, whose blades have the same optimum chord distribution but have different planforms, are tested. Measurements are made of the efficiency, torque, axial drag force and initial torque for various combinations of the pitch angle and the tip speed ratio. The yaw characteristics of the windmill are also measured.

  20. Exploring the aerodynamic drag of a moving cyclist

    NASA Astrophysics Data System (ADS)

    Theilmann, Florian; Reinhard, Christopher

    2016-01-01

    Although the physics of cycling itself is a complex mixture of aerodynamics, physiology, mechanics, and heuristics, using cycling as a context for teaching physics has a tradition of certainly more than 30 years. Here, a possible feature is the discussion of the noticeable resistant forces such as aerodynamic drag and the associated power consumption of cycling. We use an energy-based approach to model the power input for driving a bike at a constant speed. This approach uses a numerical simulation of the slowing down of a bike moving without pedaling which is implementable with standard spreadsheet software. The simulation can be compared directly to simple measurements with real bikes as well as to an analytic solution of the underlying differential equation. It is possible to derive realistic values for the aerodynamic drag coefficient {{c}\\text{D}} and the total power consumption within a secondary physics course. We also report experiences from teaching such a course to class 8 students.

  1. Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications

    SciTech Connect

    Popovic, S.; Vuskovic, L.

    2006-12-01

    Aerodynamic effects in ionized gases, often neglected phenomena, have been subject of a renewed interest in recent years. After a brief historical account, we discuss a selected number of effects and unresolved problems that appear to be relevant in both aeronautic and propulsion applications in subsonic, supersonic, and hypersonic flow. Interaction between acoustic shock waves and weakly ionized gas is manifested either as plasma-induced shock wave dispersion and acceleration or as shock-wave induced double electric layer in the plasma, followed by the localized increase of the average electron energy and density, as well as enhancement of optical emission. We describe the phenomenology of these effects and discuss several experiments that still do not have an adequate interpretation. Critical for application of aerodynamic effects is the energy deposition into the flow. We classify and discuss some proposed wall-free generation schemes with respect to the efficiency of energy deposition and overall generation of the aerodynamic body force.

  2. Wing-alone aerodynamic characteristics at high angles of attack

    NASA Technical Reports Server (NTRS)

    Stallings, R. L., Jr.; Lamb, M.

    1981-01-01

    An experimental investigation has been conducted to determine wing-alone supersonic aerodynamic characteristics at high angles of attack. The family of wings tested varied in aspect ratio from 0.5 to 4.0 and taper ratio from 0.0 to 1.0. The wings were tested at angles of attack ranging from 0 to 60 deg and Mach numbers from 1.6 to 4.6. The aerodynamic characteristics were obtained by integrating local pressures measured over the wing surface. Comparison of these data with the limited available data from the literature indicate the present data are free of sting interference effects through the test range of angle of attack. Presented and discussed are results showing the effects of model geometry, Mach number and angle of attack on aerodynamic characteristics consisting of normal force, pitching moment, bending moment, longitudinal center-of-pressure locations, and lateral center-of-pressure locations.

  3. Computational aerodynamics and artificial intelligence

    NASA Technical Reports Server (NTRS)

    Kutler, P.; Mehta, U. B.

    1984-01-01

    Some aspects of artificial intelligence are considered and questions are speculated on, including how knowledge-based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use 'expert' systems and how expert systems may speed the design and development process. The anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements are examined for using artificial intelligence in computational fluid dynamics and aerodynamics. Considering two of the essentials of computational aerodynamics - reasoniing and calculating - it is believed that a substantial part of the reasoning can be achieved with artificial intelligence, with computers being used as reasoning machines to set the stage for calculating. Expert systems will probably be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.

  4. Computational aerodynamics and artificial intelligence

    NASA Technical Reports Server (NTRS)

    Mehta, U. B.; Kutler, P.

    1984-01-01

    The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.

  5. Turbine Aerodynamics Design Tool Development

    NASA Technical Reports Server (NTRS)

    Huber, Frank W.; Turner, James E. (Technical Monitor)

    2001-01-01

    This paper presents the Marshal Space Flight Center Fluids Workshop on Turbine Aerodynamic design tool development. The topics include: (1) Meanline Design/Off-design Analysis; and (2) Airfoil Contour Generation and Analysis. This paper is in viewgraph form.

  6. Measurement of Unsteady Aerodynamics Load on the Blade of Field Horizontal Axis Wind Turbine

    NASA Astrophysics Data System (ADS)

    Kamada, Yasunari; Maeda, Takao; Naito, Keita; Ouchi, Yuu; Kozawa, Masayoshi

    This paper describes an experimental field study of the rotor aerodynamics of wind turbines. The test wind turbine is a horizontal axis wind turbine, or: HAWT with a diameter of 10m. The pressure distributions on the rotating blade are measured with multi point pressure transducers. Sectional aerodynamic forces are analyzed from pressure distribution. Blade root moments are measured simultaneously by a pair of strain gauges. The inflow wind is measured by a three component sonic anemometer, the local inflow of the blade section are measured by a pair of 7 hole Pitot tubes. The relation between the aerodynamic moments on the blade root from pressure distribution and the mechanical moment from strain gauges is discussed. The aerodynamic moments are estimated from the sectional aerodynamic forces and show oscillation caused by local wind speed and direction change. The mechanical moment shows similar oscillation to the aerodynamic excepting the short period oscillation of the blade first mode frequency. The fluctuation of the sectional aerodynamic force triggers resonant blade oscillations. Where stall is present along the blade section, the blade's first mode frequency is dominant. Without stall, the rotating frequency is dominant in the blade root moment.

  7. Intermediate Experimental Vehicle, ESA Programme Supersonic Transonic Aerodynamics

    NASA Astrophysics Data System (ADS)

    Sjors, Karin; Olsson, Jorgen; Maseland, Hans; de Cock, Koen; Dutheil, Sylvain; Bouleuc, Laurent; Cantinaud, Olivier; Tribot, Jean-Pierre; Mareschi, Vincenzo; Ferrarella, Daniella, Rufolo, Giuseppe

    2011-05-01

    The IXV project objectives are the design, development, manufacture and on ground and in flight verification of an autonomous European lifting and aerodynamically controlled re-entry system, which is highly flexible and manoeuvrable. The IXV vehicle is planned to be recovered in supersonic regime by means of a Descent and Recovery System (DRS). In that context, a specific aerodynamic identification was carried in order to provide data to be used for consolidating the AEDB (AErodynamic Data Base) and as inputs for the DRS sub-system activities. During the phase C2, a wind tunnel campaign was carried out at for the Mach number range M=1.7 to M=0.3 together with computational fluid dynamics simulation. The main objectives were to assess the aerodynamic forces and moments assuming high aileron setting in supersonic regime and to get preliminary aerodynamic data in subsonic regime to be used as input by the DRS team. The logic and the main results of these activities are presented and discussed in this paper.

  8. Aerodynamic analysis of natural flapping flight using a lift model based on spanwise flow

    NASA Astrophysics Data System (ADS)

    Alford, Lionel D., Jr.

    This study successfully described the mechanics of flapping hovering flight within the framework of conventional aerodynamics. Additionally, the theory proposed and supported by this research provides an entirely new way of looking at animal flapping flight. The mechanisms of biological flight are not well understood, and researchers have not been able to describe them using conventional aerodynamic forces. This study proposed that natural flapping flight can be broken down into a simplest model, that this model can then be used to develop a mathematical representation of flapping hovering flight, and finally, that the model can be successfully refined and compared to biological flapping data. This paper proposed a unique theory that the lift of a flapping animal is primarily the result of velocity across the cambered span of the wing. A force analysis was developed using centripetal acceleration to define an acceleration profile that would lead to a spanwise velocity profile. The force produced by the spanwise velocity profile was determined using a computational fluid dynamics analysis of flow on the simplified wing model. The overall forces on the model were found to produce more than twice the lift required for hovering flight. In addition, spanwise lift was shown to generate induced drag on the wing. Induced drag increased both the model wing's lift and drag. The model allowed the development of a mathematical representation that could be refined to account for insect hovering characteristics and that could predict expected physical attributes of the fluid flow. This computational representation resulted in a profile of lift and drag production that corresponds to known force profiles for insect flight. The model of flapping flight was shown to produce results similar to biological observation and experiment, and these results can potentially be applied to the study of other flapping animals. This work provides a foundation on which to base further exploration

  9. Measurement technology for micro-scale aerodynamics

    NASA Astrophysics Data System (ADS)

    Martin, Michael James

    As micro-technology improves, it may become possible to build flying vehicles at length scales of millimeters, or even microns. Successful design of vehicles at such sizes requires understanding of the fluid mechanics of flight at the micron scale. While biological flight has been studied at these scales, many questions remain to be answered for flight at these scales. Previous work has not determined the limiting scales of continuum aerodynamics for low-speed flight. This study begins with the development of a new scaling law based on boundary layer theory. The laminar boundary layer equations were solved non-dimensionally for slip flow conditions. These results show that a measurable decrease in skin friction, as well as changes in heat transfer, and flow stability, may occur as the boundary layer Knudsen number approaches 0.01. These flow conditions correspond to airfoil chords of up to 100 microns, pressures of 0.1 to 1.0 atmospheres, and velocities from 30 to 100 m/s. Based on this scaling law, specialized wind-tunnel test facilities were designed to operate at scales not previously studied. The novel wind-tunnel allows for independent control of Reynolds and Knudsen numbers on static airfoils. A draw-through, low turbulence, low-pressure wind tunnel with a 1 cm cross section was built and tested. The flow through these facilities is characterized, and recommendations are made for future wind-tunnel development. To allow testing at these scales, micro-scale airfoils, with chords of 100 microns, thicknesses of 5 microns, and a span of 1 cm were fabricated using MEMS fabrication technology. Fabrication of free-standing micro-structures with meso-scale spans and micro-scale cross sections required the development of specialized fabrication processes. These airfoils were integrated with piezoresistive force sensors, allowing measurement of aerodynamic forces. The airfoil structures were successfully released within the tunnel. The actual aerodynamic load on the

  10. Ergonomics strategies and actions for achieving productive use of an ageing work-force.

    PubMed

    Kumashiro, M

    2000-07-01

    In this report, a basic ERGOMA (Ergonomics in Industrial Management) strategy is proposed as a policy for corporate production and employment in countries where ageing populations and reduced birth rates are imminent, and a strategy related to this is proposed. Specifically, as a strategy at the company level, the results of survey studies aimed at the development of methods for determining job capacity, to enable effective use of the labour of ageing workers, were summarized. A number of the insights gained here are steps in the development of a foundational methodology for practical use, and in actual practice a number of these insights must be subjected to measurements. However, the theory and newly developed methodology described here are thought to represent significant changes from the approaches to job capacity diagnosis and assessment published in the past and from the stance towards utilization of an ageing work-force. The author is confident that this represents new progress in one of the ergonomics approach to dealing with the working environment of ageing workers and an ageing work-force in general. PMID:10929834

  11. Muscle-tendon unit stiffness does not independently affect voluntary explosive force production or muscle intrinsic contractile properties.

    PubMed

    Hannah, Ricci; Folland, Jonathan P

    2015-01-01

    This study examined the relationship of muscle-tendon unit (MTU) stiffness and explosive force production during voluntary and evoked contractions of the knee extensors. Thirty-four untrained participants performed a series of explosive voluntary and electrically evoked (octets (8 pulses, 300 Hz) via femoral nerve stimulation) isometric contractions. Maximum voluntary force (MVF) was assessed during maximum voluntary contractions. Explosive force production was assessed as the time taken, from force onset (0 N), to achieve specific levels of absolute (25-300 N) and relative force (5%-75% MVF) during the explosive contractions. Ultrasonic images of the vastus lateralis were recorded during 10-s ramp contractions to assess MTU stiffness, which was expressed in absolute (N · mm(-1)) and relative (to MVF and resting tendon-aponeurosis length) terms. Bivariate correlations suggested that absolute MTU stiffness was associated with voluntary explosive force (time to achieve 150-300 N: r = -0.35 to -0.54, P < 0.05). However, no relationships between stiffness and voluntary explosive force were observed when the influence of MVF was removed, either via partial correlations of absolute values (P ≥ 0.49) or considering relative values (P ≥ 0.14). Similarly, absolute MTU stiffness was related to explosive force during evoked octet contractions (r = -0.41 to -0.64, P < 0.05), but these correlations were no longer present when accounting for the influence of MVF (P ≥ 0.15). Therefore, once maximum strength was considered, MTU stiffness had no independent relationship with voluntary explosive force production or the evoked capacity for explosive force.

  12. A leader-follower relationship in joint action on a discrete force production task.

    PubMed

    Masumoto, Junya; Inui, Nobuyuki

    2014-11-01

    The present study examined the development of a leader-follower relationship in joint action performed by participants with different skill levels. Two participants were instructed to produce discrete isometric forces such that the sum of the forces was the target force. The task did not prescribe the onset time or share of force each participant contributed to the target force. Although novices with low force variability did not produce an earlier force than those with high force variability in the novice-novice group, experienced participants produced an earlier force than novices in the novice-experienced group. While participants with low force variability always produced a stronger force than those with high force variability in both the groups, there was no significant difference in force distributions between participants with low and high force variabilities. Although a novice-experienced pair produced force more complementarily than a novice-novice pair in the first practice block, the difference between pairs vanished after the first practice block, suggesting that leader-follower relations were not always beneficial to task performance. In addition, practice of the joint action did not transfer to individual action.

  13. Dynamical degrees of freedom and correlations in isometric finger force production.

    PubMed

    James, Eric G

    2012-12-01

    Prior research has concluded that the correlations of isometric finger forces represent the extent to which the fingers are controlled as a single unit. If this is the case, finger force correlations should be consistent with estimates of the controlled (dynamical) degrees of freedom in finger forces. The present study examined the finger force correlations and the dynamical degrees of freedom in four isometric force tasks. The tasks were to produce a preferred level of force with the (a) Index, (b) Ring, (c) Both fingers and also to (d) Rest the fingers on the load cells. Dynamical degrees of freedom in finger forces were lowest in the Both finger force task and progressively higher in the Ring, Index and Resting finger force tasks. The finger force correlations were highest in the Resting and lowest in the Index and Ring finger tasks. The results for the dynamical degrees of freedom in finger forces were consistent with a reduction in degrees of freedom in response to the degrees of freedom problem and the task constraints. The results for the finger force correlations were inconsistent with a reduction in the dynamical degrees of freedom. These findings indicate that finger force correlations do not necessarily reflect the coupling of finger forces. The findings also highlight the value of time-domain analyses to reveal the organization of control in isometric finger forces.

  14. Exercise-Induced Oxidative Stress: Cellular Mechanisms and Impact on Muscle Force Production

    PubMed Central

    POWERS, SCOTT K.; JACKSON, MALCOLM J.

    2010-01-01

    The first suggestion that physical exercise results in free radical-mediated damage to tissues appeared in 1978, and the past three decades have resulted in a large growth of knowledge regarding exercise and oxidative stress. Although the sources of oxidant production during exercise continue to be debated, it is now well established that both resting and contracting skeletal muscles produce reactive oxygen species and reactive nitrogen species. Importantly, intense and prolonged exercise can result in oxidative damage to both proteins and lipids in the contracting myocytes. Furthermore, oxidants can modulate a number of cell signaling pathways and regulate the expression of multiple genes in eukaryotic cells. This oxidant-mediated change in gene expression involves changes at transcriptional, mRNA stability, and signal transduction levels. Furthermore, numerous products associated with oxidant-modulated genes have been identified and include antioxidant enzymes, stress proteins, DNA repair proteins, and mitochondrial electron transport proteins. Interestingly, low and physiological levels of reactive oxygen species are required for normal force production in skeletal muscle, but high levels of reactive oxygen species promote contractile dysfunction resulting in muscle weakness and fatigue. Ongoing research continues to probe the mechanisms by which oxidants influence skeletal muscle contractile properties and to explore interventions capable of protecting muscle from oxidant-mediated dysfunction. PMID:18923182

  15. Forcings of nutrient, oxygen, and primary production interannual variability in the southeast Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Bachèlery, M.-L.; Illig, S.; Dadou, I.

    2016-08-01

    The recurrent occurrences of interannual warm and cold events along the coast of Africa have been intensively studied because of their striking effects on climate and fisheries. Using sensitivity experimentation based on a coupled physical/biogeochemical model, we show that the oceanic remote equatorial forcing explains more than 85% of coastal interannual nitrate and oxygen fluctuations along the Angolan and Namibian coasts up to the Benguela Upwelling System (BUS). These events, associated with poleward propagations of upwelling and downwelling Coastal Trapped Waves (CTW), are maximum in subsurface and controlled by physical advection processes. Surprisingly, an abrupt change in the CTW biogeochemical signature is observed in the BUS, associated with mixed vertical gradients due to the strong local upwelling dynamics. Coastal modifications of biogeochemical features result in significant primary production variations that may affect fisheries habitats and coastal biodiversity along the southwestern African coasts and in the BUS.

  16. Aerodynamics of badminton shuttlecocks

    NASA Astrophysics Data System (ADS)

    Verma, Aekaansh; Desai, Ajinkya; Mittal, Sanjay

    2013-08-01

    A computational study is carried out to understand the aerodynamics of shuttlecocks used in the sport of badminton. The speed of the shuttlecock considered is in the range of 25-50 m/s. The relative contribution of various parts of the shuttlecock to the overall drag is studied. It is found that the feathers, and the net in the case of a synthetic shuttlecock, contribute the maximum. The gaps, in the lower section of the skirt, play a major role in entraining the surrounding fluid and causing a difference between the pressure inside and outside the skirt. This pressure difference leads to drag. This is confirmed via computations for a shuttlecock with no gaps. The synthetic shuttle experiences more drag than the feather model. Unlike the synthetic model, the feather shuttlecock is associated with a swirling flow towards the end of the skirt. The effect of the twist angle of the feathers on the drag as well as the flow has also been studied.

  17. Aerodynamics of bird flight

    NASA Astrophysics Data System (ADS)

    Dvořák, Rudolf

    2016-03-01

    Unlike airplanes birds must have either flapping or oscillating wings (the hummingbird). Only such wings can produce both lift and thrust - two sine qua non attributes of flying.The bird wings have several possibilities how to obtain the same functions as airplane wings. All are realized by the system of flight feathers. Birds have also the capabilities of adjusting the shape of the wing according to what the immediate flight situation demands, as well as of responding almost immediately to conditions the flow environment dictates, such as wind gusts, object avoidance, target tracking, etc. In bird aerodynamics also the tail plays an important role. To fly, wings impart downward momentum to the surrounding air and obtain lift by reaction. How this is achieved under various flight situations (cruise flight, hovering, landing, etc.), and what the role is of the wing-generated vortices in producing lift and thrust is discussed.The issue of studying bird flight experimentally from in vivo or in vitro experiments is also briefly discussed.

  18. Introduction. Computational aerodynamics.

    PubMed

    Tucker, Paul G

    2007-10-15

    The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier-Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used.

  19. 76 FR 22921 - Child Labor, Forced Labor, and Forced or Indentured Child Labor in the Production of Goods in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-25

    ... Labor and Human Trafficking (OCFT) at the e-mail or physical address below by 5 p.m., May 20, 2011. To... goods (72 FR 73374). The guidelines set forth the criteria by which information is evaluated... of products (the ``List''), identified by country of origin, that the Department, in consultation...

  20. Aerodynamic and Aeroelastic Characteristics of a Tension Cone Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Clark, Ian G.; Cruz, Juan R.; Hughes, Monica F.; Ware, Joanne S.; Madlangbayan, Albert; Braun, Robert D.

    2009-01-01

    The supersonic aerodynamic and aeroelastic characteristics of a tension cone inflatable aerodynamic decelerator were investigated by wind tunnel testing. Two sets of tests were conducted: one using rigid models and another using textile models. Tests using rigid models were conducted over a Mach number range from 1.65 to 4.5 at angles of attack from -12 to 20 degrees. The axial, normal, and pitching moment coefficients were found to be insensitive to Mach number over the tested range. The axial force coefficient was nearly constant (C(sub A) = 1.45 +/- 0.05) with respect to angle of attack. Both the normal and pitching moment coefficients were nearly linear with respect to angle of attack. The pitching moment coefficient showed the model to be statically stable about the reference point. Schlieren images and video showed a detached bow shock with no evidence of large regions of separated flow and/or embedded shocks at all Mach numbers investigated. Qualitatively similar static aerodynamic coefficient and flow visualization results were obtained using textile models at a Mach number of 2.5. Using inflatable textile models the torus pressure required to maintain the model in the fully-inflated configuration was determined. This pressure was found to be sensitive to details in the structural configuration of the inflatable models. Additional tests included surface pressure measurements on rigid models and deployment and inflation tests with inflatable models.

  1. Modeling the Launch Abort Vehicle's Subsonic Aerodynamics from Free Flight Testing

    NASA Technical Reports Server (NTRS)

    Hartman, Christopher L.

    2010-01-01

    An investigation into the aerodynamics of the Launch Abort Vehicle for NASA's Constellation Crew Launch Vehicle in the subsonic, incompressible flow regime was conducted in the NASA Langley 20-ft Vertical Spin Tunnel. Time histories of center of mass position and Euler Angles are captured using photogrammetry. Time histories of the wind tunnel's airspeed and dynamic pressure are recorded as well. The primary objective of the investigation is to determine models for the aerodynamic yaw and pitch moments that provide insight into the static and dynamic stability of the vehicle. System IDentification Programs for AirCraft (SIDPAC) is used to determine the aerodynamic model structure and estimate model parameters. Aerodynamic models for the aerodynamic body Y and Z force coefficients, and the pitching and yawing moment coefficients were identified.

  2. Velopharyngeal orifice area prediction during aerodynamic simulation of fricative consonants.

    PubMed

    Smith, B E; Weinberg, B

    1983-01-01

    The present work examined the predictive nature of modeled velopharyngeal orifice area calculations obtained using the hydrokinetic equation (Warren and DuBois, 1964) during conditions simulating voiceless fricative production. Results indicated that accurate estimates of velopharyngeal orifice area can be obtained during aerodynamic events like those known to exist during fricative production. These findings were interpreted to lend support to the view that aerodynamic assessment incorporating hydrokinetic principles provides a useful, noninvasive method for clinical testing and research investigation of velopharyngeal function. PMID:6572571

  3. Climatic and oceanic forcing of new, net, and diatom production in the North Water

    NASA Astrophysics Data System (ADS)

    Tremblay, Jean-Eric; Gratton, Yves; Fauchot, Juliette; Price, Neil M.

    New, net, and diatom production in the North Water were estimated during May to July 1998 from in vitro measurements of nitrate uptake and mesoscale temporal changes in the inventories of nitrate, silicate, oxygen, and inorganic carbon (DIC). Sampling stations were divided into two domains according to the position of the dominant water types: the silicate-rich Arctic water (SRAW) and Baffin Bay Water (BBW). BBW dominated in the southeast and was associated with relatively shallow upper mixed layers (UMLs) and weak horizontal advection. A phytoplankton bloom started in late April in BBW and grew slowly over 7 weeks, during which time the build-up of particulate organic nitrogen and carbon accounted for ca. 80% of the nitrate and DIC deficit, respectively. Over half of the new production (1.37 g C m -2 d -1) during this period was attributed to wind-driven replenishment of nitrate in the euphotic zone. The bloom culminated when seasonally declining winds and rising temperatures severed the UML from the deep nutrient reservoir. The same change in weather induced ice melt, stratification, and bloom development in northern SRAW, which had previously been characterized by deep UMLs. Collectively, the results imply that the timing and magnitude of blooms in the North Water are controlled by a succession of oceanic and climatic forcings. New C production in the North Water during April to July (1.11 g C m -2 d -1) was an order of magnitude higher than in adjacent waters and up to 8 times higher than in the Northeast Water polynya. As much as 80% of this production was mediated by diatoms >5 μm, suggesting potentially high and efficient C transfer to the herbivorous food web and deep waters.

  4. Quasi-steady state aerodynamics of the cheetah tail.

    PubMed

    Patel, Amir; Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-01-01

    During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities. PMID:27412267

  5. Quasi-steady state aerodynamics of the cheetah tail

    PubMed Central

    Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-01-01

    ABSTRACT During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities. PMID:27412267

  6. Quasi-steady state aerodynamics of the cheetah tail.

    PubMed

    Patel, Amir; Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-08-15

    During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities.

  7. Aerodynamics and vortical structures in hovering fruitflies

    NASA Astrophysics Data System (ADS)

    Meng, Xue Guang; Sun, Mao

    2015-03-01

    We measure the wing kinematics and morphological parameters of seven freely hovering fruitflies and numerically compute the flows of the flapping wings. The computed mean lift approximately equals to the measured weight and the mean horizontal force is approximately zero, validating the computational model. Because of the very small relative velocity of the wing, the mean lift coefficient required to support the weight is rather large, around 1.8, and the Reynolds number of the wing is low, around 100. How such a large lift is produced at such a low Reynolds number is explained by combining the wing motion data, the computed vortical structures, and the theory of vorticity dynamics. It has been shown that two unsteady mechanisms are responsible for the high lift. One is referred as to "fast pitching-up rotation": at the start of an up- or downstroke when the wing has very small speed, it fast pitches down to a small angle of attack, and then, when its speed is higher, it fast pitches up to the angle it normally uses. When the wing pitches up while moving forward, large vorticity is produced and sheds at the trailing edge, and vorticity of opposite sign is produced near the leading edge and on the upper surface, resulting in a large time rate of change of the first moment of vorticity (or fluid impulse), hence a large aerodynamic force. The other is the well known "delayed stall" mechanism: in the mid-portion of the up- or downstroke the wing moves at large angle of attack (about 45 deg) and the leading-edge-vortex (LEV) moves with the wing; thus, the vortex ring, formed by the LEV, the tip vortices, and the starting vortex, expands in size continuously, producing a large time rate of change of fluid impulse or a large aerodynamic force.

  8. Aerodynamics of two-dimensional slotted bluff bodies

    SciTech Connect

    Takahashi, F.; Higuchi, H.

    1988-04-30

    Aerodynamic characteristics of two-dimensional, slotted bluff bodies were experimentally investigated. Flow visualizations, base pressure measurements, mean velocity vector measurements, and drag force measurements were conducted to analyze effects of spacing ratio (i.e., porosity), curvature, and vent. Low porosity model configurations produced stable near-wake patterns with enhanced vortex sheddings of overall wake formations. Model curvature reduced drag forces and weakened the vortex sheddings. Stabilizing effect of curvature on the near-wake patterns was also found. A vent combined with large model curvature was found to control drag force effectively, as well as suppressing vortex sheddings. 10 refs., 52 figs., 1 tab.

  9. Effect of forced aeration on citric acid production by Aspergillus sp. mutants in SSF.

    PubMed

    Rodrigues, Cristine; Vandenberghe, Luciana P S; Sturm, Wilerson; Dergint, Dario E A; Spier, Michele Rigon; de Carvalho, Júlio Cesar; Soccol, Carlos R

    2013-12-01

    Citric acid (CA) is one of the most important products of fermentation in the world. A great variety of agro-industrial residues can be used in solid state fermentation. Aspergillus niger parental strain (CCT 7716) and two strains obtained by mutagenesis (CCT 7717 and CCT 7718) were evaluated in Erlenmeyer flasks and glass columns using citric pulp (CP) as substrate/support, sugarcane molasses and methanol. Best results using glass columns (forced aeration) were found in the fourth day of fermentation: 278.4, 294.9 and 261.1 g CA/kg of dry CP with CCT 7716, CCT 7718 and CCT 7717, respectively. In Erlenmeyer flasks (aeration by diffusion) CA reached 410.7, 446.8 and 492.7 g CA/kg of dry CP with CCT 7716, CCT 7718 and CCT 7717, respectively. The aeration by diffusion improved CA production by the three strains. A data acquisition system specially developed for biotechnological processes analysis was used to perform the respirometric parameters measurement.

  10. Application Program Interface for the Orion Aerodynamics Database

    NASA Technical Reports Server (NTRS)

    Robinson, Philip E.; Thompson, James

    2013-01-01

    The Application Programming Interface (API) for the Crew Exploration Vehicle (CEV) Aerodynamic Database has been developed to provide the developers of software an easily implemented, fully self-contained method of accessing the CEV Aerodynamic Database for use in their analysis and simulation tools. The API is programmed in C and provides a series of functions to interact with the database, such as initialization, selecting various options, and calculating the aerodynamic data. No special functions (file read/write, table lookup) are required on the host system other than those included with a standard ANSI C installation. It reads one or more files of aero data tables. Previous releases of aerodynamic databases for space vehicles have only included data tables and a document of the algorithm and equations to combine them for the total aerodynamic forces and moments. This process required each software tool to have a unique implementation of the database code. Errors or omissions in the documentation, or errors in the implementation, led to a lengthy and burdensome process of having to debug each instance of the code. Additionally, input file formats differ for each space vehicle simulation tool, requiring the aero database tables to be reformatted to meet the tool s input file structure requirements. Finally, the capabilities for built-in table lookup routines vary for each simulation tool. Implementation of a new database may require an update to and verification of the table lookup routines. This may be required if the number of dimensions of a data table exceeds the capability of the simulation tools built-in lookup routines. A single software solution was created to provide an aerodynamics software model that could be integrated into other simulation and analysis tools. The highly complex Orion aerodynamics model can then be quickly included in a wide variety of tools. The API code is written in ANSI C for ease of portability to a wide variety of systems. The

  11. Attenuated rapid onset vasodilation with greater force production in skeletal muscle of caveolin-2-/- mice.

    PubMed

    Fernando, Charmain A; Liu, Yajun; Sowa, Grzegorz; Segal, Steven S

    2016-08-01

    Caveolin-2 (Cav2) is a major protein component of caveolae in membranes of vascular smooth muscle and endothelium, yet its absence alters the ultrastructure of skeletal muscle fibers. To gain insight into Cav2 function in skeletal muscle, we tested the hypothesis that genetic deletion of Cav2 would alter microvascular reactivity and depress contractile function of skeletal muscle in vivo. In the left gluteus maximus muscle (GM) of anesthetized Cav2(-/-) and wild-type (WT) male mice (age, 6 mo), microvascular responses to physiological agonists and to GM contractions were studied at 34°C. For feed arteries (FA), first- (1A), second- (2A) and third-order (3A) arterioles, respective mean diameters at rest (45, 35, 25, 12 μm) and during maximal dilation (65, 55, 45, 30 μm) were similar between groups. Cumulative dilations to ACh (10(-9) to 10(-5) M) and constrictions to norepinephrine (10(-9) to 10(-5) M) were also similar between groups, as were steady-state dilations during rhythmic twitch contractions (2 and 4 Hz; 30 s). For single tetanic contractions (100 Hz; 100, 250, and 500 ms), rapid onset vasodilation (ROV) increased with contraction duration throughout networks in GM of both groups but was reduced by nearly half in Cav2(-/-) mice compared with WT mice (P < 0.05). Nevertheless, maximal force during tetanic contraction was ∼40% greater in GM of Cav2(-/-) vs. WT mice (152 ± 14 vs. 110 ± 3 mN per square millimeter, respectively; P < 0.05). Thus, while structural and functional properties of resistance networks are well maintained in the GM of Cav2(-/-) mice, diminished ROV with greater force production reveals novel physiological roles for Cav2 in skeletal muscle. PMID:27317631

  12. Aerodynamic Analysis of Simulated Heat Shield Recession for the Orion Command Module

    NASA Technical Reports Server (NTRS)

    Bibb, Karen L.; Alter, Stephen J.; Mcdaniel, Ryan D.

    2008-01-01

    The aerodynamic effects of the recession of the ablative thermal protection system for the Orion Command Module of the Crew Exploration Vehicle are important for the vehicle guidance. At the present time, the aerodynamic effects of recession being handled within the Orion aerodynamic database indirectly with an additional safety factor placed on the uncertainty bounds. This study is an initial attempt to quantify the effects for a particular set of recessed geometry shapes, in order to provide more rigorous analysis for managing recession effects within the aerodynamic database. The aerodynamic forces and moments for the baseline and recessed geometries were computed at several trajectory points using multiple CFD codes, both viscous and inviscid. The resulting aerodynamics for the baseline and recessed geometries were compared. The forces (lift, drag) show negligible differences between baseline and recessed geometries. Generally, the moments show a difference between baseline and recessed geometries that correlates with the maximum amount of recession of the geometry. The difference between the pitching moments for the baseline and recessed geometries increases as Mach number decreases (and the recession is greater), and reach a value of -0.0026 for the lowest Mach number. The change in trim angle of attack increases from approx. 0.5deg at M = 28.7 to approx. 1.3deg at M = 6, and is consistent with a previous analysis with a lower fidelity engineering tool. This correlation of the present results with the engineering tool results supports the continued use of the engineering tool for future work. The present analysis suggests there does not need to be an uncertainty due to recession in the Orion aerodynamic database for the force quantities. The magnitude of the change in pitching moment due to recession is large enough to warrant inclusion in the aerodynamic database. An increment in the uncertainty for pitching moment could be calculated from these results and

  13. Interaction of finger enslaving and error compensation in multiple finger force production

    PubMed Central

    Martin, Joel R.; Latash, Mark L.; Zatsiorsky, Vladimir M.

    2009-01-01

    Previous studies have documented two patterns of finger interaction during multi-finger pressing tasks, enslaving and error compensation, which do not agree with each other. Enslaving is characterized by positive correlation between instructed (master) and non-instructed (slave) finger(s) while error compensation can be described as a pattern of negative correlation between master and slave fingers. We hypothesize that pattern of finger interaction, enslaving or compensation, depends on the initial force level and the magnitude of the targeted force change. Subjects were instructed to press with four fingers (I - index, M - middle, R - ring, and L - little) from a specified initial force to a target forces following a ramp target line. Force-force relations between master and each of three slave fingers were analyzed during the ramp phase of trials by calculating correlation coefficients within each master-slave pair and then 2-factor ANOVA was performed to determine effect of initial force and force increase on the correlation coefficients. It was found that, as initial force increased, the value of the correlation coefficient decreased and in some cases became negative, i.e. the enslaving transformed into error compensation. Force increase magnitude had a smaller effect on the correlation coefficients. The observations support the hypothesis that the pattern of inter-finger interaction—enslaving or compensation—depends on the initial force level and, to a smaller degree, on the targeted magnitude of the force increase. They suggest that the controller views tasks with higher steady-state forces and smaller force changes as implying a requirement to avoid large changes in the total force. PMID:18985331

  14. A computational model of cerebrospinal fluid production and reabsorption driven by Starling forces.

    PubMed

    Buishas, Joel; Gould, Ian G; Linninger, Andreas A

    2014-10-01

    Experimental evidence has cast doubt on the classical model of river-like cerebrospinal fluid (CSF) flow from the choroid plexus to the arachnoid granulations. We propose a novel model of water transport through the parenchyma from the microcirculation as driven by Starling forces. This model investigates the effect of osmotic pressure on water transport between the cerebral vasculature, the extracellular space (ECS), the perivascular space (PVS), and the CSF. A rigorous literature search was conducted focusing on experiments which alter the osmolarity of blood or ventricles and measure the rate of CSF production. Investigations into the effect of osmotic pressure on the volume of ventricles and the flux of ions in the blood, choroid plexus epithelium, and CSF are reviewed. Increasing the osmolarity of the serum via a bolus injection completely inhibits nascent fluid flow production in the ventricles. A continuous injection of a hyperosmolar solution into the ventricles can increase the volume of the ventricle by up to 125%. CSF production is altered by 0.231 μL per mOsm in the ventricle and by 0.835 μL per mOsm in the serum. Water flux from the ECS to the CSF is identified as a key feature of intracranial dynamics. A complete mathematical model with all equations and scenarios is fully described, as well as a guide to constructing a computational model of intracranial water balance dynamics. The model proposed in this article predicts the effects the osmolarity of ECS, blood, and CSF on water flux in the brain, establishing a link between osmotic imbalances and pathological conditions such as hydrocephalus and edema. PMID:25358881

  15. Aerosol Radiative Forcing Estimates from South Asian Clay Brick Production Based on Direct Emission Measurements

    NASA Astrophysics Data System (ADS)

    Weyant, C.; Athalye, V.; Ragavan, S.; Rajarathnam, U.; Kr, B.; Lalchandani, D.; Maithel, S.; Malhotra, G.; Bhanware, P.; Thoa, V.; Phuong, N.; Baum, E.; Bond, T. C.

    2012-12-01

    About 150-200 billion clay bricks are produced in India every year. Most of these bricks are fired in small-scale traditional kilns that burn coal or biomass without pollution controls. Reddy and Venkataraman (2001) estimated that 8% of fossil fuel related PM2.5 emissions and 23% of black carbon emissions in India are released from brick production. Few direct emissions measurements have been done in this industry and black carbon emissions, in particular, have not been previously measured. In this study, 9 kilns representing five common brick kiln technologies were tested for aerosol properties and gaseous pollutant emissions, including optical scattering and absorption and thermal-optical OC/EC. Simple relationships are then used to estimate the radiative-forcing impact. Kiln design and fuel quality greatly affect the overall emission profiles and relative climate warming. Batch production kilns, such as the Downdraft kiln, produce the most PM2.5 (0.97 gPM2.5/fired brick) with an OC/EC fraction of 0.3. Vertical Shaft Brick kilns using internally mixed fuels produce the least PM (0.09 gPM2.5/kg fired brick) with the least EC (OC/EC = 16.5), but these kilns are expensive to implement and their use throughout Southern Asia is minimal. The most popular kiln in India, the Bull's Trench kiln, had fewer emissions per brick than the Downdraft kiln, but an even higher EC fraction (OC/EC = 0.05). The Zig-zag kiln is similar in structure to the Bull's Trench kiln, but the emission factors are significantly lower: 50% reduction for CO, 17% for PM2.5 and 60% for black carbon. This difference in emissions suggests that converting traditional Bull's Trench kilns into less polluting Zig-zag kilns would result in reduced atmospheric warming from brick production.

  16. Configuration Aerodynamics: Past - Present - Future

    NASA Technical Reports Server (NTRS)

    Wood, Richard M.; Agrawal, Shreekant; Bencze, Daniel P.; Kulfan, Robert M.; Wilson, Douglas L.

    1999-01-01

    The Configuration Aerodynamics (CA) element of the High Speed Research (HSR) program is managed by a joint NASA and Industry team, referred to as the Technology Integration Development (ITD) team. This team is responsible for the development of a broad range of technologies for improved aerodynamic performance and stability and control characteristics at subsonic to supersonic flight conditions. These objectives are pursued through the aggressive use of advanced experimental test techniques and state of the art computational methods. As the HSR program matures and transitions into the next phase the objectives of the Configuration Aerodynamics ITD are being refined to address the drag reduction needs and stability and control requirements of High Speed Civil Transport (HSCT) aircraft. In addition, the experimental and computational tools are being refined and improved to meet these challenges. The presentation will review the work performed within the Configuration Aerodynamics element in 1994 and 1995 and then discuss the plans for the 1996-1998 time period. The final portion of the presentation will review several observations of the HSR program and the design activity within Configuration Aerodynamics.

  17. Aerodynamic drag on intermodal railcars

    NASA Astrophysics Data System (ADS)

    Kinghorn, Philip; Maynes, Daniel

    2014-11-01

    The aerodynamic drag associated with transport of commodities by rail is becoming increasingly important as the cost of diesel fuel increases. This study aims to increase the efficiency of intermodal cargo trains by reducing the aerodynamic drag on the load carrying cars. For intermodal railcars a significant amount of aerodynamic drag is a result of the large distance between loads that often occurs and the resulting pressure drag resulting from the separated flow. In the present study aerodynamic drag data have been obtained through wind tunnel testing on 1/29 scale models to understand the savings that may be realized by judicious modification to the size of the intermodal containers. The experiments were performed in the BYU low speed wind tunnel and the test track utilizes two leading locomotives followed by a set of five articulated well cars with double stacked containers. The drag on a representative mid-train car is measured using an isolated load cell balance and the wind tunnel speed is varied from 20 to 100 mph. We characterize the effect that the gap distance between the containers and the container size has on the aerodynamic drag of this representative rail car and investigate methods to reduce the gap distance.

  18. Validation of Methodology for Estimating Aircraft Unsteady Aerodynamic Parameters from Dynamic Wind Tunnel Tests

    NASA Technical Reports Server (NTRS)

    Murphy, Patrick C.; Klein, Vladislav

    2003-01-01

    A basic problem in flight dynamics is the mathematical formulation of the aerodynamic model for aircraft. This study is part of an ongoing effort at NASA Langley to develop a more general formulation of the aerodynamic model for aircraft that includes nonlinear unsteady aerodynamics and to develop appropriate test techniques that facilitate identification of these models. A methodology for modeling and testing using wide-band inputs to estimate the unsteady form of the aircraft aerodynamic model was developed previously but advanced test facilities were not available at that time to allow complete validation of the methodology. The new model formulation retained the conventional static and rotary dynamic terms but replaced conventional acceleration terms with more general indicial functions. In this study advanced testing techniques were utilized to validate the new methodology for modeling. Results of static, conventional forced oscillation, wide-band forced oscillation, oscillatory coning, and ramp tests are presented.

  19. Fast-Running Aeroelastic Code Based on Unsteady Linearized Aerodynamic Solver Developed

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.; Bakhle, Milind A.; Keith, T., Jr.

    2003-01-01

    The NASA Glenn Research Center has been developing aeroelastic analyses for turbomachines for use by NASA and industry. An aeroelastic analysis consists of a structural dynamic model, an unsteady aerodynamic model, and a procedure to couple the two models. The structural models are well developed. Hence, most of the development for the aeroelastic analysis of turbomachines has involved adapting and using unsteady aerodynamic models. Two methods are used in developing unsteady aerodynamic analysis procedures for the flutter and forced response of turbomachines: (1) the time domain method and (2) the frequency domain method. Codes based on time domain methods require considerable computational time and, hence, cannot be used during the design process. Frequency domain methods eliminate the time dependence by assuming harmonic motion and, hence, require less computational time. Early frequency domain analyses methods neglected the important physics of steady loading on the analyses for simplicity. A fast-running unsteady aerodynamic code, LINFLUX, which includes steady loading and is based on the frequency domain method, has been modified for flutter and response calculations. LINFLUX, solves unsteady linearized Euler equations for calculating the unsteady aerodynamic forces on the blades, starting from a steady nonlinear aerodynamic solution. First, we obtained a steady aerodynamic solution for a given flow condition using the nonlinear unsteady aerodynamic code TURBO. A blade vibration analysis was done to determine the frequencies and mode shapes of the vibrating blades, and an interface code was used to convert the steady aerodynamic solution to a form required by LINFLUX. A preprocessor was used to interpolate the mode shapes from the structural dynamic mesh onto the computational dynamics mesh. Then, we used LINFLUX to calculate the unsteady aerodynamic forces for a given mode, frequency, and phase angle. A postprocessor read these unsteady pressures and

  20. New technology in turbine aerodynamics.

    NASA Technical Reports Server (NTRS)

    Glassman, A. J.; Moffitt, T. P.

    1972-01-01

    Cursory review of some recent work that has been done in turbine aerodynamic research. Topics discussed include the aerodynamic effect of turbine coolant, high work-factor (ratio of stage work to square of blade speed) turbines, and computer methods for turbine design and performance prediction. Experimental cooled-turbine aerodynamics programs using two-dimensional cascades, full annular cascades, and cold rotating turbine stage tests are discussed with some typical results presented. Analytically predicted results for cooled blade performance are compared to experimental results. The problems and some of the current programs associated with the use of very high work factors for fan-drive turbines of high-bypass-ratio engines are discussed. Computer programs have been developed for turbine design-point performance, off-design performance, supersonic blade profile design, and the calculation of channel velocities for subsonic and transonic flowfields. The use of these programs for the design and analysis of axial and radial turbines is discussed.

  1. General Theory of Aerodynamic Instability and the Mechanism of Flutter

    NASA Technical Reports Server (NTRS)

    Theodorsen, Theodore

    1949-01-01

    The aerodynamic forces on an oscillating airfoil or airfoil-aileron combination of three independent degrees of freedom have been determined. The problem resolves itself into the solution of certain definite integrals, which have been identified as Bessel functions of the first and second kind and of zero and first order. The theory, being based on potential flow and the Kutta condition, is fundamentally equivalent to the conventional wing-section theory relating to the steady case. The air forces being known, the mechanism of aerodynamic instability has been analyzed in detail. An exact solution, involving potential flow and the adoption of the Kutta condition, has been analyzed in detail. An exact solution, involving potential flow and the adoption of the Kutta condition, has been arrived at. The solution is of a simple form and is expressed by means of an auxiliary parameter K.

  2. Aerodynamic Characteristics of High Speed Trains under Cross Wind Conditions

    NASA Astrophysics Data System (ADS)

    Chen, W.; Wu, S. P.; Zhang, Y.

    2011-09-01

    Numerical simulation for the two models in cross-wind was carried out in this paper. The three-dimensional compressible Reynolds-averaged Navier-Stokes equations(RANS), combined with the standard k-ɛ turbulence model, were solved on multi-block hybrid grids by second order upwind finite volume technique. The impact of fairing on aerodynamic characteristics of the train models was analyzed. It is shown that, the flow separates on the fairing and a strong vortex is generated, the pressure on the upper middle car decreases dramatically, which leads to a large lift force. The fairing changes the basic patterns around the trains. In addition, formulas of the coefficient of aerodynamic force at small yaw angles up to 24° were expressed.

  3. Does lowering evening rectal temperature to morning levels offset the diurnal variation in muscle force production?

    PubMed

    Robinson, William R; Pullinger, Samuel A; Kerry, Jonathan W; Giacomoni, Magali; Robertson, Colin M; Burniston, Jatin G; Waterhouse, James M; Edwards, Ben J

    2013-10-01

    Muscle force production and power output in active males, regardless of the site of measurement (hand, leg, or back), are higher in the evening than the morning. This diurnal variation is attributed to motivational, peripheral, and central factors and higher core and, possibly, muscle temperatures in the evening. This study investigated whether decreasing evening resting rectal temperatures to morning values, by immersion in a water tank, leads to muscle force production and power output becoming equal to morning values in motivated subjects. Ten healthy active males (mean ± SD: age, 22.5 ± 1.3 yrs; body mass, 80.1 ± 7.8 kg; height, 1.72 ± 0.05 m) completed the study, which was approved by the local ethics committee of the university. The subjects were familiarized with the techniques and protocol and then completed three sessions (separated by at least 48 h): control morning (07:30 h) and evening (17:30 h) sessions (with an active 5-min warm-up on a cycle ergometer at 150 W) and then a further session at 17:30 h but preceded by an immersion in cold water (~16.5 °C) to lower rectal temperature (Trec) to morning values. During each trial, three measures of grip strength, isokinetic leg strength measurements (of knee flexion and extension at 1.05 and 4.19 rad s(-1) through a 90° range of motion), and three measures of maximal voluntary contraction (MVC) on an isometric dynamometer (utilizing the twitch-interpolation technique) were performed. Trec, rating of perceived exertion (RPE), and thermal comfort (TC) were also measured after the subjects had reclined for 30 min at the start of the protocol and prior to the measures for grip, isokinetic, and isometric dynamometry. Muscle temperature was taken after the warm-up or water immersion and immediately before the isokinetic and MVC measurements. Data were analyzed using general linear models with repeated measures. Trec values were higher at rest in the evening (by 0.37 °C; p < 0.05) than the morning, but

  4. Results of an aerodynamic force and moment investigation of an 0.015-scale configuration 3 space shuttle orbiter in the NASA/ARC 3.5-foot hypersonic wind tunnel (OA58)

    NASA Technical Reports Server (NTRS)

    Dziubala, T. J.; Cleary, J. W.

    1974-01-01

    The primary objective of the test was to obtain stability and control data for the basic configuration and an alternate configuration for the Space Shuttle Orbiter. Pitch runs were made with 0 deg of sideslip at Mach numbers of 5.3, 7.3 and 10.3. Six-component force data and fuselage base pressures were recorded for each run. Shadowgraph pictures were taken at selected points. Model 420 was used for the tests.

  5. Aerodynamics Research Revolutionizes Truck Design

    NASA Technical Reports Server (NTRS)

    2008-01-01

    During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.

  6. Importance of anisotropy in detachment rates for force production and cargo transport by a team of motor proteins.

    PubMed

    Takshak, Anjneya; Kunwar, Ambarish

    2016-05-01

    Many cellular processes are driven by collective forces generated by a team consisting of multiple molecular motor proteins. One aspect that has received less attention is the detachment rate of molecular motors under mechanical force/load. While detachment rate of kinesin motors measured under backward force increases rapidly for forces beyond stall-force; this scenario is just reversed for non-yeast dynein motors where detachment rate from microtubule decreases, exhibiting a catch-bond type behavior. It has been shown recently that yeast dynein responds anisotropically to applied load, i.e. detachment rates are different under forward and backward pulling. Here, we use computational modeling to show that these anisotropic detachment rates might help yeast dynein motors to improve their collective force generation in the absence of catch-bond behavior. We further show that the travel distance of cargos would be longer if detachment rates are anisotropic. Our results suggest that anisotropic detachment rates could be an alternative strategy for motors to improve the transport properties and force production by the team. PMID:26890030

  7. Production and destruction of eddy kinetic energy in forced submesoscale eddy-resolving simulations

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sonaljit; Ramachandran, Sanjiv; Tandon, Amit; Mahadevan, Amala

    2016-09-01

    We study the production and dissipation of the eddy kinetic energy (EKE) in a submesoscale eddy field forced with downfront winds using the Process Study Ocean Model (PSOM) with a horizontal grid resolution of 0.5 km. We simulate an idealized 100 m deep mixed-layer front initially in geostrophic balance with a jet in a domain that permits eddies within a range of O(1 km-100 km). The vertical eddy viscosities and the dissipation are parameterized using four different subgrid vertical mixing parameterizations: the k - ɛ , the KPP, and two different constant eddy viscosity and diffusivity profiles with a magnitude of O(10-2m2s-1) in the mixed layer. Our study shows that strong vertical eddy viscosities near the surface reduce the parameterized dissipation, whereas strong vertical eddy diffusivities reduce the lateral buoyancy gradients and consequently the rate of restratification by mixed-layer instabilities (MLI). Our simulations show that near the surface, the spatial variability of the dissipation along the periphery of the eddies depends on the relative alignment of the ageostrophic and geostrophic shear. Analysis of the resolved EKE budgets in the frontal region from the simulations show important similarities between the vertical structure of the EKE budget produced by the k - ɛ and KPP parameterizations, and earlier LES studies. Such an agreement is absent in the simulations using constant eddy-viscosity parameterizations.

  8. Force production during squats performed with a rotational resistance device under stable versus unstable conditions

    PubMed Central

    Moras, Gerard; Vázquez-Guerrero, Jairo

    2015-01-01

    [Purpose] Force production during a squat action on a rotational resistance device (RRD) under stable and unstable conditions. [Subjects and Methods] Twenty-one healthy males were asked to perform six sets of six repetitions of squats on an RRD on either stable or unstable surfaces. The stable and unstable sets were performed on different days. Muscular outputs were obtained from a linear encoder and a strain gauge fixed to a vest. [Results] Overall, the results showed no significant differences for any of the dependent variables across exercise modes. Forcemean outputs were higher in the concentric phase than in the eccentric phase for each condition, but there were no differences in velocity, time or displacement. The forcepeak was similar in the eccentric and concentric phases of movement under both stable and unstable conditions. There were no significant differences in forcemean between sets per condition or between conditions. [Conclusion] These results suggest that performing squats with a RRD achieves similar forcemean and forcepeak under stable and unstable conditions. The forcepeak produced is also similar in concentric and eccentric phases. PMID:26696707

  9. Effects of vibration training on force production in female basketball players.

    PubMed

    Fernandez-Rio, Javier; Terrados, Nicolas; Fernandez-Garcia, Benjamin; Suman, Oscar E

    2010-05-01

    The goal of this research project was to investigate the long-term effects of whole-body vibration (WBV) training on force production. Thirty-one female basketball players were randomly distributed in an experimental group: VG (vibration) and a control group: CG (no vibration). Both groups participated in the same training program; however, the experimental group (VG) performed a set of exercises on a vibration platform (Power Plate) at 30- to 35-Hz frequency and 4 mm amplitude, whereas the CG performed the same exercises at 0 Hz. Muscle performance of the legs was tested on a contact-time platform (Ergojump, Finland) through several tests: squat jump (SJ), countermovement jump (CMJ), and 15-second maximal performance jump; squat leg power (knee extension) was also evaluated using an Ergopower machine (Bosco, Italy). After 14 weeks, there was a significant increase (p < 0.001) from initial to final tests in both groups (CG and VG) in SJ, CMJ, 15 seconds, and squat leg power. However, there were no significant differences between the VG and the CG for any of the parameters evaluated. The findings of this study indicate that WBV training has no additive or discernible effect on the strength development of female basketball players after several weeks of use, suggesting that the application of this technology has no advantages over traditional strength training methods.

  10. Equifinality and its violations in a redundant system: multifinger accurate force production

    PubMed Central

    Wilhelm, Luke; Zatsiorsky, Vladimir M.

    2013-01-01

    We explored a hypothesis that transient perturbations applied to a redundant system result in equifinality in the space of task-related performance variables but not in the space of elemental variables. The subjects pressed with four fingers and produced an accurate constant total force level. The “inverse piano” device was used to lift and lower one of the fingers smoothly. The subjects were instructed “not to intervene voluntarily” with possible force changes. Analysis was performed in spaces of finger forces and finger modes (hypothetical neural commands to fingers) as elemental variables. Lifting a finger led to an increase in its force and a decrease in the forces of the other three fingers; the total force increased. Lowering the finger back led to a drop in the force of the perturbed finger. At the final state, the sum of the variances of finger forces/modes computed across repetitive trials was significantly higher than the variance of the total force/mode. Most variance of the individual finger force/mode changes between the preperturbation and postperturbation states was compatible with constant total force. We conclude that a transient perturbation applied to a redundant system leads to relatively small variance in the task-related performance variable (equifinality), whereas in the space of elemental variables much more variance occurs that does not lead to total force changes. We interpret the results within a general theoretical scheme that incorporates the ideas of hierarchically organized control, control with referent configurations, synergic control, and the uncontrolled manifold hypothesis. PMID:23904497

  11. Equifinality and its violations in a redundant system: multifinger accurate force production.

    PubMed

    Wilhelm, Luke; Zatsiorsky, Vladimir M; Latash, Mark L

    2013-10-01

    We explored a hypothesis that transient perturbations applied to a redundant system result in equifinality in the space of task-related performance variables but not in the space of elemental variables. The subjects pressed with four fingers and produced an accurate constant total force level. The "inverse piano" device was used to lift and lower one of the fingers smoothly. The subjects were instructed "not to intervene voluntarily" with possible force changes. Analysis was performed in spaces of finger forces and finger modes (hypothetical neural commands to fingers) as elemental variables. Lifting a finger led to an increase in its force and a decrease in the forces of the other three fingers; the total force increased. Lowering the finger back led to a drop in the force of the perturbed finger. At the final state, the sum of the variances of finger forces/modes computed across repetitive trials was significantly higher than the variance of the total force/mode. Most variance of the individual finger force/mode changes between the preperturbation and postperturbation states was compatible with constant total force. We conclude that a transient perturbation applied to a redundant system leads to relatively small variance in the task-related performance variable (equifinality), whereas in the space of elemental variables much more variance occurs that does not lead to total force changes. We interpret the results within a general theoretical scheme that incorporates the ideas of hierarchically organized control, control with referent configurations, synergic control, and the uncontrolled manifold hypothesis. PMID:23904497

  12. Elytra boost lift, but reduce aerodynamic efficiency in flying beetles.

    PubMed

    Johansson, L Christoffer; Engel, Sophia; Baird, Emily; Dacke, Marie; Muijres, Florian T; Hedenström, Anders

    2012-10-01

    Flying insects typically possess two pairs of wings. In beetles, the front pair has evolved into short, hardened structures, the elytra, which protect the second pair of wings and the abdomen. This allows beetles to exploit habitats that would otherwise cause damage to the wings and body. Many beetles fly with the elytra extended, suggesting that they influence aerodynamic performance, but little is known about their role in flight. Using quantitative measurements of the beetle's wake, we show that the presence of the elytra increases vertical force production by approximately 40 per cent, indicating that they contribute to weight support. The wing-elytra combination creates a complex wake compared with previously studied animal wakes. At mid-downstroke, multiple vortices are visible behind each wing. These include a wingtip and an elytron vortex with the same sense of rotation, a body vortex and an additional vortex of the opposite sense of rotation. This latter vortex reflects a negative interaction between the wing and the elytron, resulting in a single wing span efficiency of approximately 0.77 at mid downstroke. This is lower than that found in birds and bats, suggesting that the extra weight support of the elytra comes at the price of reduced efficiency. PMID:22593097

  13. Elytra boost lift, but reduce aerodynamic efficiency in flying beetles

    PubMed Central

    Johansson, L. Christoffer; Engel, Sophia; Baird, Emily; Dacke, Marie; Muijres, Florian T.; Hedenström, Anders

    2012-01-01

    Flying insects typically possess two pairs of wings. In beetles, the front pair has evolved into short, hardened structures, the elytra, which protect the second pair of wings and the abdomen. This allows beetles to exploit habitats that would otherwise cause damage to the wings and body. Many beetles fly with the elytra extended, suggesting that they influence aerodynamic performance, but little is known about their role in flight. Using quantitative measurements of the beetle's wake, we show that the presence of the elytra increases vertical force production by approximately 40 per cent, indicating that they contribute to weight support. The wing-elytra combination creates a complex wake compared with previously studied animal wakes. At mid-downstroke, multiple vortices are visible behind each wing. These include a wingtip and an elytron vortex with the same sense of rotation, a body vortex and an additional vortex of the opposite sense of rotation. This latter vortex reflects a negative interaction between the wing and the elytron, resulting in a single wing span efficiency of approximately 0.77 at mid downstroke. This is lower than that found in birds and bats, suggesting that the extra weight support of the elytra comes at the price of reduced efficiency. PMID:22593097

  14. Computations of Aerodynamic Performance Databases Using Output-Based Refinement

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis, Michael J.

    2009-01-01

    Objectives: Handle complex geometry problems; Control discretization errors via solution-adaptive mesh refinement; Focus on aerodynamic databases of parametric and optimization studies: 1. Accuracy: satisfy prescribed error bounds 2. Robustness and speed: may require over 105 mesh generations 3. Automation: avoid user supervision Obtain "expert meshes" independent of user skill; and Run every case adaptively in production settings.

  15. Coupled Aerodynamic-Thermal-Structural (CATS) Analysis

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Coupled Aerodynamic-Thermal-Structural (CATS) Analysis is a focused effort within the Numerical Propulsion System Simulation (NPSS) program to streamline multidisciplinary analysis of aeropropulsion components and assemblies. Multidisciplinary analysis of axial-flow compressor performance has been selected for the initial focus of this project. CATS will permit more accurate compressor system analysis by enabling users to include thermal and mechanical effects as an integral part of the aerodynamic analysis of the compressor primary flowpath. Thus, critical details, such as the variation of blade tip clearances and the deformation of the flowpath geometry, can be more accurately modeled and included in the aerodynamic analyses. The benefits of this coupled analysis capability are (1) performance and stall line predictions are improved by the inclusion of tip clearances and hot geometries, (2) design alternatives can be readily analyzed, and (3) higher fidelity analysis by researchers in various disciplines is possible. The goals for this project are a 10-percent improvement in stall margin predictions and a 2:1 speed-up in multidisciplinary analysis times. Working cooperatively with Pratt & Whitney, the Lewis CATS team defined the engineering processes and identified the software products necessary for streamlining these processes. The basic approach is to integrate the aerodynamic, thermal, and structural computational analyses by using data management and Non-Uniform Rational B-Splines (NURBS) based data mapping. Five software products have been defined for this task: (1) a primary flowpath data mapper, (2) a two-dimensional data mapper, (3) a database interface, (4) a blade structural pre- and post-processor, and (5) a computational fluid dynamics code for aerothermal analysis of the drum rotor. Thus far (1) a cooperative agreement has been established with Pratt & Whitney, (2) a Primary Flowpath Data Mapper has been prototyped and delivered to General Electric

  16. Langley Symposium on Aerodynamics, volume 1

    NASA Technical Reports Server (NTRS)

    Stack, Sharon H. (Compiler)

    1986-01-01

    The purpose of this work was to present current work and results of the Langley Aeronautics Directorate covering the areas of computational fluid dynamics, viscous flows, airfoil aerodynamics, propulsion integration, test techniques, and low-speed, high-speed, and transonic aerodynamics. The following sessions are included in this volume: theoretical aerodynamics, test techniques, fluid physics, and viscous drag reduction.

  17. Unsteady aerodynamics modeling for flight dynamics application

    NASA Astrophysics Data System (ADS)

    Wang, Qing; He, Kai-Feng; Qian, Wei-Qi; Zhang, Tian-Jiao; Cheng, Yan-Qing; Wu, Kai-Yuan

    2012-02-01

    In view of engineering application, it is practicable to decompose the aerodynamics into three components: the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration, the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch, yaw, roll, and coupled yawroll large-amplitude oscillations. The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics, respectively. The results show that: (1) unsteady aerodynamics has no effect upon the existence of trim points, but affects their stability; (2) unsteady aerodynamics has great effects upon the existence, stability, and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously. Furthermore, the dynamic responses of the aircraft to elevator deflections are inspected. It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft. Finally, the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.

  18. Numerical and experimental investigations on unsteady aerodynamics of flapping wings

    NASA Astrophysics Data System (ADS)

    Yu, Meilin

    the flow fields around a series of plunging NACA symmetric airfoils with thickness ratio ranging from 4.0% to 20.0% of the airfoil chord length. The contribution of viscous force to flapping propulsion is accessed and it is found that viscous force becomes thrust producing, instead of drag producing, and plays a non-negligible role in thrust generation for thin airfoils. This is closely related to the variations of the dynamics of the unsteady vortex structures around the plunging airfoils. As nature flyers use complex wing kinematics in flapping flight, kinematics effects on the aerodynamic performance with different airfoil thicknesses are numerically studied by using a series of NACA symmetric airfoils. It is found that the combined plunging and pitching motion can outperform the pure plunging or pitching motion by sophisticatedly adjusting the airfoil gestures during the oscillation stroke. The thin airfoil better manipulates leading edge vortices (LEVs) than the thick airfoil (NACA0030) does in studied cases, and there exists an optimal thickness for large thrust generation with reasonable propulsive efficiency. With the present kinematics and dynamic parameters, relatively low reduced frequency is conducive for thrust production and propulsive efficiency for all tested airfoil thicknesses. In order to obtain the optimal kinematics parameters of flapping flight, a kinematics optimization is then performed. A gradient-based optimization algorithm is coupled with a second-order SD Navier-Stokes solver to search for the optimal kinematics of a certain airfoil undergoing a combined plunging and pitching motion. Then a high-order SD scheme is used to verify the optimization results and reveal the detailed vortex structures associated with the optimal kinematics of the flapping flight. It is found that for the case with maximum propulsive efficiency, there exists no leading edge separation during most of the oscillation cycle. In order to provide constructive

  19. Aerodynamic performance and particle image velocimetery of piezo actuated biomimetic manduca sexta engineered wings towards the design and application of a flapping wing flight vehicle

    NASA Astrophysics Data System (ADS)

    DeLuca, Anthony M.

    Considerable research and investigation has been conducted on the aerodynamic performance, and the predominate flow physics of the Manduca Sexta size of biomimetically designed and fabricated wings as part of the AFIT FWMAV design project. Despite a burgeoning interest and research into the diverse field of flapping wing flight and biomimicry, the aerodynamics of flapping wing flight remains a nebulous field of science with considerable variance into the theoretical abstractions surrounding aerodynamic mechanisms responsible for aerial performance. Traditional FWMAV flight models assume a form of a quasi-steady approximation of wing aerodynamics based on an infinite wing blade element model (BEM). An accurate estimation of the lift, drag, and side force coefficients is a critical component of autonomous stability and control models. This research focused on two separate experimental avenues into the aerodynamics of AFIT's engineered hawkmoth wings|forces and flow visualization. 1. Six degree of freedom force balance testing, and high speed video analysis was conducted on 30°, 45°, and 60° angle stop wings. A novel, non-intrusive optical tracking algorithm was developed utilizing a combination of a Gaussian Mixture Model (GMM) and ComputerVision (OpenCV) tools to track the wing in motion from multiple cameras. A complete mapping of the wing's kinematic angles as a function of driving amplitude was performed. The stroke angle, elevation angle, and angle of attack were tabulated for all three wings at driving amplitudes ranging from A=0.3 to A=0.6. The wing kinematics together with the force balance data was used to develop several aerodynamic force coefficient models. A combined translational and rotational aerodynamic model predicted lift forces within 10%, and vertical forces within 6%. The total power consumption was calculated for each of the three wings, and a Figure of Merit was calculated for each wing as a general expression of the overall efficiency of

  20. Aerodynamic effects of corrugation and deformation in flapping wings of hovering hoverflies.

    PubMed

    Du, Gang; Sun, Mao

    2012-05-01

    We investigated the aerodynamic effects of wing deformation and corrugation of a three-dimensional model hoverfly wing at a hovering condition by solving the Navier-Stokes equations on a dynamically deforming grid. Various corrugated wing models were tested. Insight into whether or not there existed significant aerodynamic coupling between wing deformation (camber and twist) and wing corrugation was obtained by comparing aerodynamic forces of four cases: a smooth-plate wing in flapping motion without deformation (i.e. a rigid flat-plate wing in flapping motion); a smooth-plate wing in flapping motion with deformation; a corrugated wing in flapping motion without deformation (i.e. a rigid corrugated wing in flapping motion); a corrugated wing in flapping motion with deformation. There was little aerodynamic coupling between wing deformation and corrugation: the aerodynamic effect of wing deformation and corrugation acting together was approximately a superposition of those of deformation and corrugation acting separately. When acting alone, the effect of wing deformation was to increase the lift by 9.7% and decrease the torque (or aerodynamic power) by 5.2%, and that of wing corrugation was to decrease the lift by 6.5% and increase the torque by 2.2%. But when acting together, the wing deformation and corrugation only increased the lift by ~3% and decreased the torque by ~3%. That is, the combined aerodynamic effect of deformation and corrugation is rather small. Thus, wing corrugation is mainly for structural, not aerodynamic, purpose, and in computing or measuring the aerodynamic forces, using a rigid flat-plate wing to model the corrugated deforming wing at hovering condition can be a good approximation. PMID:22266123

  1. Aerodynamic effects of corrugation and deformation in flapping wings of hovering hoverflies.

    PubMed

    Du, Gang; Sun, Mao

    2012-05-01

    We investigated the aerodynamic effects of wing deformation and corrugation of a three-dimensional model hoverfly wing at a hovering condition by solving the Navier-Stokes equations on a dynamically deforming grid. Various corrugated wing models were tested. Insight into whether or not there existed significant aerodynamic coupling between wing deformation (camber and twist) and wing corrugation was obtained by comparing aerodynamic forces of four cases: a smooth-plate wing in flapping motion without deformation (i.e. a rigid flat-plate wing in flapping motion); a smooth-plate wing in flapping motion with deformation; a corrugated wing in flapping motion without deformation (i.e. a rigid corrugated wing in flapping motion); a corrugated wing in flapping motion with deformation. There was little aerodynamic coupling between wing deformation and corrugation: the aerodynamic effect of wing deformation and corrugation acting together was approximately a superposition of those of deformation and corrugation acting separately. When acting alone, the effect of wing deformation was to increase the lift by 9.7% and decrease the torque (or aerodynamic power) by 5.2%, and that of wing corrugation was to decrease the lift by 6.5% and increase the torque by 2.2%. But when acting together, the wing deformation and corrugation only increased the lift by ~3% and decreased the torque by ~3%. That is, the combined aerodynamic effect of deformation and corrugation is rather small. Thus, wing corrugation is mainly for structural, not aerodynamic, purpose, and in computing or measuring the aerodynamic forces, using a rigid flat-plate wing to model the corrugated deforming wing at hovering condition can be a good approximation.

  2. New technology in turbine aerodynamics

    NASA Technical Reports Server (NTRS)

    Glassman, A. J.; Moffitt, T. P.

    1972-01-01

    A cursory review is presented of some of the recent work that has been done in turbine aerodynamic research at NASA-Lewis Research Center. Topics discussed include the aerodynamic effect of turbine coolant, high work-factor (ratio of stage work to square of blade speed) turbines, and computer methods for turbine design and performance prediction. An extensive bibliography is included. Experimental cooled-turbine aerodynamics programs using two-dimensional cascades, full annular cascades, and cold rotating turbine stage tests are discussed with some typical results presented. Analytically predicted results for cooled blade performance are compared to experimental results. The problems and some of the current programs associated with the use of very high work factors for fan-drive turbines of high-bypass-ratio engines are discussed. Turbines currently being investigated make use of advanced blading concepts designed to maintain high efficiency under conditions of high aerodynamic loading. Computer programs have been developed for turbine design-point performance, off-design performance, supersonic blade profile design, and the calculation of channel velocities for subsonic and transonic flow fields. The use of these programs for the design and analysis of axial and radial turbines is discussed.

  3. Sensitivity analysis in computational aerodynamics

    NASA Technical Reports Server (NTRS)

    Bristow, D. R.

    1984-01-01

    Information on sensitivity analysis in computational aerodynamics is given in outline, graphical, and chart form. The prediction accuracy if the MCAERO program, a perturbation analysis method, is discussed. A procedure for calculating perturbation matrix, baseline wing paneling for perturbation analysis test cases and applications of an inviscid sensitivity matrix are among the topics covered.

  4. Aerodynamic laboratory at Cuatro Vientos

    NASA Technical Reports Server (NTRS)

    JUBERA

    1922-01-01

    This report presents a listing of the many experiments in aerodynamics taking place at Cuatro Vientos. Some of the studies include: testing spheres, in order to determine coefficients; mechanical and chemical tests of materials; and various tests of propeller strength and flexibility.

  5. Shuttle reentry aerodynamic heating test

    NASA Technical Reports Server (NTRS)

    Pond, J. E.; Mccormick, P. O.; Smith, S. D.

    1971-01-01

    The research for determining the space shuttle aerothermal environment is reported. Brief summaries of the low Reynolds number windward side heating test, and the base and leeward heating and high Reynolds number heating test are included. Also discussed are streamline divergence and the resulting effect on aerodynamic heating, and a thermal analyzer program that is used in the Thermal Environment Optimization Program.

  6. Dynamic Soaring: Aerodynamics for Albatrosses

    ERIC Educational Resources Information Center

    Denny, Mark

    2009-01-01

    Albatrosses have evolved to soar and glide efficiently. By maximizing their lift-to-drag ratio "L/D", albatrosses can gain energy from the wind and can travel long distances with little effort. We simplify the difficult aerodynamic equations of motion by assuming that albatrosses maintain a constant "L/D". Analytic solutions to the simplified…

  7. POEMS in Newton's Aerodynamic Frustum

    ERIC Educational Resources Information Center

    Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita

    2010-01-01

    The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…

  8. Rotary wing aerodynamically generated noise

    NASA Technical Reports Server (NTRS)

    Schmitz, F. J.; Morse, H. A.

    1982-01-01

    The history and methodology of aerodynamic noise reduction in rotary wing aircraft are presented. Thickness noise during hover tests and blade vortex interaction noise are determined and predicted through the use of a variety of computer codes. The use of test facilities and scale models for data acquisition are discussed.

  9. Aerodynamic design via control theory

    NASA Technical Reports Server (NTRS)

    Jameson, Antony

    1988-01-01

    The question of how to modify aerodynamic design in order to improve performance is addressed. Representative examples are given to demonstrate the computational feasibility of using control theory for such a purpose. An introduction and historical survey of the subject is included.

  10. Orion Aerodynamics for Hypersonic Free Molecular to Continuum Conditions

    NASA Technical Reports Server (NTRS)

    Moss, James N.; Greene, Francis A.; Boyles, Katie A.

    2006-01-01

    Numerical simulations are performed for the Orion Crew Module, previously known as the Crew Exploration Vehicle (CEV) Command Module, to characterize its aerodynamics during the high altitude portion of its reentry into the Earth's atmosphere, that is, from free molecular to continuum hypersonic conditions. The focus is on flow conditions similar to those that the Orion Crew Module would experience during a return from the International Space Station. The bulk of the calculations are performed with two direct simulation Monte Carlo (DSMC) codes, and these data are anchored with results from both free molecular and Navier-Stokes calculations. Results for aerodynamic forces and moments are presented that demonstrate their sensitivity to rarefaction, that is, for free molecular to continuum conditions (Knudsen numbers of 111 to 0.0003). Also included are aerodynamic data as a function of angle of attack for different levels of rarefaction and results that demonstrate the aerodynamic sensitivity of the Orion CM to a range of reentry velocities (7.6 to 15 km/s).

  11. Passive flow control by membrane wings for aerodynamic benefit

    NASA Astrophysics Data System (ADS)

    Timpe, Amory; Zhang, Zheng; Hubner, James; Ukeiley, Lawrence

    2013-03-01

    The coupling of passive structural response of flexible membranes with the flow over them can significantly alter the aerodynamic characteristic of simple flat-plate wings. The use of flexible wings is common throughout biological flying systems inspiring many engineers to incorporate them into small engineering flying systems. In many of these systems, the motion of the membrane serves to passively alter the flow over the wing potentially resulting in an aerodynamic benefit. In this study, the aerodynamic loads and the flow field for a rigid flat-plate wing are compared to free trailing-edge membrane wings with two different pre-tensions at a chord-based Reynolds number of approximately 50,000. The membrane was silicon rubber with a scalloped free trailing edge. The analysis presented includes load measurements from a sting balance along with velocity fields and membrane deflections from synchronized, time-resolved particle image velocimetry and digital image correlation. The load measurements demonstrate increased aerodynamic efficiency and lift, while the synchronized flow and membrane measurements show how the membrane motion serves to force the flow. This passive flow control introduced by the membranes motion alters the flows development over the wing and into the wake region demonstrating how, at least for lower angles of attack, the membranes motion drives the flow as opposed to the flow driving the membrane motion.

  12. Comparison of TOPEX/Poseidon Sea Level and Linear Model Results forced by Various Wind Products for the Tropical Pacific

    NASA Technical Reports Server (NTRS)

    Hackert, Eric C.; Busalacchi, Antonio J.

    1997-01-01

    The goal of this paper is to compare TOPEX/Posaidon (T/P) sea level with sea level results from linear ocean model experiments forced by several different wind products for the tropical Pacific. During the period of this study (October 1992 - October 1995), available wind products include satellite winds from the ERS-1 scatterometer product of [HALP 97] and the passive microwave analysis of SSMI winds produced using the variational analysis method (VAM) of [ATLA 91]. In addition, atmospheric GCM winds from the NCEP reanalysis [KALN 96], ECMWF analysis [ECMW94], and the Goddard EOS-1 (GEOS-1) reanalysis experiment [SCHU 93] are available for comparison. The observed ship wind analysis of FSU [STRI 92] is also included in this study. The linear model of [CANE 84] is used as a transfer function to test the quality of each of these wind products for the tropical Pacific. The various wind products are judged by comparing the wind-forced model sea level results against the T/P sea level anomalies. Correlation and RMS difference maps show how well each wind product does in reproducing the T/P sea level signal. These results are summarized in a table showing area average correlations and RMS differences. The large-scale low-frequency temporal signal is reproduced by all of the wind products, However, significant differences exist in both amplitude and phase on regional scales. In general, the model results forced by satellite winds do a better job reproducing the T/P signal (i.e. have a higher average correlation and lower RMS difference) than the results forced by atmospheric model winds.

  13. Does raising morning rectal temperature to evening levels offset the diurnal variation in muscle force production?

    PubMed

    Edwards, Ben J; Pullinger, Samuel A; Kerry, Jonathan W; Robinson, William R; Reilly, Tom P; Robertson, Colin M; Waterhouse, James M

    2013-05-01

    Muscle force production and power output in active males, regardless of the site of measurement (hand, leg, or back), are higher in the evening than in the morning. This diurnal variation is attributed to motivational, peripheral and central factors, and higher core and, possibly, muscle temperatures in the evening. This study investigated whether increasing morning rectal temperatures to evening resting values, by active or passive warm-ups, leads to muscle force production and power output becoming equal to evening values in motivated subjects. Ten healthy active males (mean ± SD: age, 21.2 ± 1.9 yrs; body mass, 75.4 ± 8 kg; height, 1.76 ± .06 m) completed the study, which was approved by the University Ethics Committee. The subjects were familiarized with the techniques and protocol and then completed four sessions (separated by at least 48 h): control morning (07:30 h) and evening (17:30 h) sessions (with an active 5-min warm-up) and then two further sessions at 07:30 h but proceeded by an extended active or passive warm-up to raise rectal temperature to evening values. These last two sessions were counterbalanced in order of administration. During each trial, three measures of handgrip strength, isokinetic leg strength measurements (of knee flexion and extension at 1.05 and 4.19 rad.s(-1) through a 90° range of motion), and four measures of maximal voluntary contraction (MVC) on an isometric ergometer (utilizing the twitch-interpolation technique) were performed. Rectal and intra-aural temperatures, ratings of perceived exertion (RPE) and thermal comfort (TC) were measured. Measurements were made after the subjects had reclined for 30 min and after the warm-ups and prior to the measurement of handgrip and isokinetic and isometric ergometry. Muscle temperature was taken after the warm-up and immediately before the isokinetic and MVC measurements. Warm-ups were either active (cycle ergometer at 150 W) or passive (resting in a room at 35 °C, relative

  14. Structural forces and the production of TB-related stigma among Haitians in two contexts.

    PubMed

    Coreil, Jeannine; Mayard, Gladys; Simpson, Kelly M; Lauzardo, Michael; Zhu, Yiliang; Weiss, Mitchell

    2010-10-01

    In recent years renewed interest in health-related stigma has underscored the importance of better understanding the structural underpinnings of stigma processes. This study investigated the influence of sociocultural context on perceived components of tuberculosis-related stigma in non-affected persons by comparing Haitians living in South Florida, USA, with Haitians residing in Léogane Commune, Haiti. Using the methods of cultural epidemiology, a two-phase study based on fieldwork between 2004 and 2007 collected ethnographic data on the cultural context and components of tuberculosis (TB) stigma, and administered a stigma scale developed specifically for these populations. Thematic analysis of stigma components expressed in interviews, focus groups and observation revealed commonalities as well as distinctive emphases of TB stigma in the two comparison groups. Factor analyses of stigma scale scores confirmed the thematic differences revealed in ethnographic findings and highlight the influence of political and economic factors in shaping the meaning and experience of illness. Perceived components of TB stigma among Haitians in South Florida incorporated aspects of Haitian identity as a negatively stereotyped minority community within the larger society, while in Haiti, stigma was associated primarily with poverty, malnutrition, and HIV co-infection. Discussion of findings focuses on the social production of perceived and anticipated stigma as it is influenced by structural forces including the influences of politics, economics, institutional policies, and health service delivery structures. The findings also demonstrate the value of a transnational framework encompassing both sending and receiving countries for understanding TB-related stigma in immigrant communities.

  15. What Geological, Economic, or Policy Forces Might Limit Fossil Fuel Production?

    NASA Astrophysics Data System (ADS)

    Heinberg, R.

    2015-12-01

    In order to ensure a 50% chance of keeping global temperatures from exceeding 2°C above pre-industrial levels, it has been estimated that total carbon dioxide emissions between 2011-2050 must be capped at roughly 1,100 gigatons.[1] However, some estimates calculate that global fossil fuel reserves—including unconventional oil and gas—hold at least three times this amount of potential greenhouse gas emissions.[2]What socio-political, technological, or economic forces are most likely to keep these energy resources from being burned? While it is difficult to predict with specificity what combination of technological, geological, or human factors will significantly minimize global fossil fuel production, there are at least four key potential drivers: 1. Under-investment and the economics of unconventional oil and natural gas; 2. International policy, driven by citizen demand and leadership from key nations; 3. Massive deployment of renewable energy sources and other technological solutions; and 4. Large-scale energy curtailment resulting from global economic contraction. We will explore the implications, viability, and consequences of each of these potential factors. [1] [1]United Nations Framework Convention on Climate Change (UNFCC) Report of the Conference of the Parties on its Fifteenth Session, held in Copenhagen from 7 to 19 December 2009. Part Two: Action taken by the Conference of the Parties at its Fifteenth Session. United Nations Climate Change Conf. Report 43 http://unfccc.int/resource/docs/2009/cop15/eng/11a01.pdf (UNFCC, 2009) [2] Raupach, M. R. et al. Sharing a quota on cumulative carbon emissions. Nature Clim. Chang. 4, 873-879 (2014)

  16. Structural Forces and the Production of TB-related Stigma among Haitians in Two Contexts

    PubMed Central

    Coreil, Jeannine; Mayard, Gladys; Simpson, Kelly M; Lauzardo, Michael; Zhu, Yiliang; Weiss, Mitchell

    2012-01-01

    In recent years renewed interest in health-related stigma has underscored the importance of better understanding the structural underpinnings of stigma processes. This study investigated the influence of sociocultural context on perceived components of tuberculosis-related stigma in non-affected persons by comparing Haitians living in South Florida, USA, with Haitians residing in Léogane Commune, Haiti. Using the methods of cultural epidemiology, a two-phase study based on fieldwork between 2004–07 collected ethnographic data on the cultural context and components of tuberculosis (TB) stigma, and administered a stigma scale developed specifically for these populations. Thematic analysis of stigma components expressed in interviews, focus groups and observation revealed commonalities as well as distinctive emphases of TB stigma in the two comparison groups. Factor analyses of stigma scale scores confirmed the thematic differences revealed in ethnographic findings and highlight the influence of political and economic factors in shaping the meaning and experience of illness. Perceived components of TB stigma among Haitians in South Florida incorporated aspects of Haitian identity as a negatively stereotyped minority community within the larger society, while in Haiti, stigma was associated primarily with poverty, malnutrition, and HIV co-infection. Discussion of findings focuses on the social production of perceived and anticipated stigma as it is influenced by structural forces including the influences of politics, economics, institutional policies, and health service delivery structures. The findings also demonstrate the value of a transnational framework encompassing both sending and receiving countries for understanding TB related stigma in immigrant communities. PMID:20724052

  17. Force production characteristics of leg extensor, trunk flexor and extensor muscles in male and female basketball players.

    PubMed

    Häkkinen, K

    1991-09-01

    Eleven male and nine female basketball players from two teams at the same relative competitive level were studied for the force production characteristics of their leg extensor, trunk flexor and extensor muscles. As expected, the male players demonstrated greater (p less than 0.001) absolute maximal strength in the three muscle groups than the females. When the force values were related to body weight, the differences became smaller but the male group could still produce higher values especially for the trunk flexor (p less than 0.01) and extensor muscles (p less than 0.05). The males demonstrated higher (p less than 0.001) values than the females for maximal vertical jumping height both in the squat jump (41.5 +/- 3.0 and 21.5 +/- 2.4 cm) and in the counter movement jump (43.9 +/- 4.0 and 24.8 +/- 2.5 cm). As expected, the times required to produce the same absolute force levels in the isometric force-time curves were significantly (p less than 0.001) shorter in the male team than in the female. However, the times needed to produce the same relative force levels were also shorter (p less than 0.05) in the male group. In the whole subject sample the individual values in maximal leg extension force correlated significantly (p less than 0.001) with the vertical jumping height. The present results suggest that the differences observed in force production characteristics between the male and female groups may not be explained only by the sexual difference but also by the differences in the overall volume and/or the type of strength and power training during the preparatory training season(s).(ABSTRACT TRUNCATED AT 250 WORDS)

  18. The influence of the breathing action on net drag force production in front crawl swimming.

    PubMed

    Formosa, D; Sayers, M G L; Burkett, B

    2014-12-01

    20 elite swimmers completed a total of 6 randomized net drag force trials in 2 conditions (i) 3 breathing and (ii) 3 non-breathing. Net drag force was measured using an assisted motorized dynamometer device mounted upon a Kistler force-platform. The male participants demonstrated no statistical differences in stroke rates between breathing and non-breathing trials. Female participants, however, demonstrated a statistical difference stroke rate. The male participants demonstrated that the breathing action caused a greater (26%) net drag force compared to the females (16%). To further understand the influence of breathing on swimming technique, each stroke was analyzed and comparisons were made between the breathing and non-breathing conditions. The male participants demonstrated a similar minimum net drag force when comparing the breathing and non-breathing conditions. Analysis showed that minimum net drag force and maximum net drag force for the males changed when integrating the breathing action, while female participants demonstrated similar swimming technique, regardless of condition or stroke.

  19. Pressures, forces, moments and shock shapes for a geometrically matched sphere-cone and hyperboloid at Mach 20.3 in helium. [22-inch aerodynamics leg of the Langley hypersonic helium tunnel facility

    NASA Technical Reports Server (NTRS)

    Calloway, R. L.

    1983-01-01

    An investigation was conducted to compare measured and predicted pressure distributions, forces and moments, and shock shapes on a geometrically matched sphere-cone and hyperboloid. A hyperboloid with a nose radius of 0.5276 in. and an asymptotic angle of 39.9871 deg was matched to a sphere-cone with a nose radius of 0.750 in. and a cone half-angle of 45 deg. Experimental results in helium at a free-stream Mach number of 20.3 and a free-stream unit Reynolds number of 6.83 x 10 to the 6th power per foot were combined with predicted results from a theoretical method to compare the two shapes. Comparisons of experimental results showed small differences in the two shapes, but the prediction method provided better results for the hyperboloid than for the sphere-cone.

  20. Aerodynamic Force Characteristics of a Series of Lifting Cone and Cone-Cylinder Configurations at a Mach Number of 6.83 and Angles of Attack up to 130 Deg

    NASA Technical Reports Server (NTRS)

    Penland, Jim A.

    1961-01-01

    Force tests of a series of right circular cones having semivertex angles ranging from 5 deg to 45 deg and a series of right circular cone-cylinder configurations having semivertex angles ranging from 5 deg to 20 deg and an afterbody fineness ratio of 6 have been made in the Langley 11-inch hypersonic tunnel at a Mach number of 6.83, a Reynolds number of 0.24 x 10.6 per inch, and angles of attack up to 130 deg. An analysis of the results made use of the Newtonian and modified Newtonian theories and the exact theory. A comparison of the experimental data of both cone and cone-cylinder configurations with theoretical calculations shows that the Newtonian concept gives excellent predictions of trends of the force characteristics and the locations with respect to angle of attack of the points of maximum lift, maximum drag, and maximum lift-drag ratio. Both the Newtonian a.nd exact theories give excellent predictions of the sign and value of the initial lift-curve slope. The maximum lift coefficient for conical bodies is nearly constant at a value of 0.5 based on planform area for semivertex angles up to 30 deg. The maximum lift-drag ratio for conical bodies can be expected to be not greater than about 3.5, and this value might be expected only for slender cones having semivertex angles of less than 5 deg. The increments of angle of attack and lift coefficient between the maximum lift-drag ratio and the maximum lift coefficient for conical bodies decrease rapidly with increasing semivertex angles as predicted by the modified Newtonian theory.

  1. Aerodynamics of a linear oscillating cascade

    NASA Technical Reports Server (NTRS)

    Buffum, Daniel H.; Fleeter, Sanford

    1990-01-01

    The steady and unsteady aerodynamics of a linear oscillating cascade are investigated using experimental and computational methods. Experiments are performed to quantify the torsion mode oscillating cascade aerodynamics of the NASA Lewis Transonic Oscillating Cascade for subsonic inlet flowfields using two methods: simultaneous oscillation of all the cascaded airfoils at various values of interblade phase angle, and the unsteady aerodynamic influence coefficient technique. Analysis of these data and correlation with classical linearized unsteady aerodynamic analysis predictions indicate that the wind tunnel walls enclosing the cascade have, in some cases, a detrimental effect on the cascade unsteady aerodynamics. An Euler code for oscillating cascade aerodynamics is modified to incorporate improved upstream and downstream boundary conditions and also the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic predictions of the code, and the computational unsteady aerodynamic influence coefficient technique is shown to be a viable alternative for calculation of oscillating cascade aerodynamics.

  2. Flutter and Forced Response Analyses of Cascades using a Two-Dimensional Linearized Euler Solver

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.; Srivastava, R.; Mehmed, O.

    1999-01-01

    Flutter and forced response analyses for a cascade of blades in subsonic and transonic flow is presented. The structural model for each blade is a typical section with bending and torsion degrees of freedom. The unsteady aerodynamic forces due to bending and torsion motions. and due to a vortical gust disturbance are obtained by solving unsteady linearized Euler equations. The unsteady linearized equations are obtained by linearizing the unsteady nonlinear equations about the steady flow. The predicted unsteady aerodynamic forces include the effect of steady aerodynamic loading due to airfoil shape, thickness and angle of attack. The aeroelastic equations are solved in the frequency domain by coupling the un- steady aerodynamic forces to the aeroelastic solver MISER. The present unsteady aerodynamic solver showed good correlation with published results for both flutter and forced response predictions. Further improvements are required to use the unsteady aerodynamic solver in a design cycle.

  3. JT9D performance deterioration results from a simulated aerodynamic load test

    NASA Technical Reports Server (NTRS)

    Stakolich, E. G.; Stromberg, W. J.

    1981-01-01

    The results of testing to identify the effects of simulated aerodynamic flight loads on JT9D engine performance are presented. The test results were also used to refine previous analytical studies on the impact of aerodynamic flight loads on performance losses. To accomplish these objectives, a JT9D-7AH engine was assembled with average production clearances and new seals as well as extensive instrumentation to monitor engine performance, case temperatures, and blade tip clearance changes. A special loading device was designed and constructed to permit application of known moments and shear forces to the engine by the use of cables placed around the flight inlet. The test was conducted in the Pratt & Whitney Aircraft X-Ray Test Facility to permit the use of X-ray techniques in conjunction with laser blade tip proximity probes to monitor important engine clearance changes. Upon completion of the test program, the test engine was disassembled, and the condition of gas path parts and final clearances were documented. The test results indicate that the engine lost 1.1 percent in thrust specific fuel consumption (TSFC), as measured under sea level static conditions, due to increased operating clearances caused by simulated flight loads. This compares with 0.9 percent predicted by the analytical model and previous study efforts.

  4. Control of Pitching Airfoil Aerodynamics by Vorticity Flux Modification using Active Bleed

    NASA Astrophysics Data System (ADS)

    Kearney, John; Glezer, Ari

    2014-11-01

    Distributed active bleed driven by pressure differences across a pitching airfoil is used to regulate the vorticity flux over the airfoil's surface and thereby to control aerodynamic loads in wind tunnel experiments. The range of pitch angles is varied beyond the static stall margin of the 2-D VR-7 airfoil at reduced pitching rates up to k = 0.42. Bleed is regulated dynamically using piezoelectric louvers between the model's pressure side near the trailing edge and the suction surface near the leading edge. The time-dependent evolution of vorticity concentrations over the airfoil and in the wake during the pitch cycle is investigated using high-speed PIV and the aerodynamic forces and moments are measured using integrated load cells. The timing of the dynamic stall vorticity flux into the near wake and its effect on the flow field are analyzed in the presence and absence of bleed using proper orthogonal decomposition (POD). It is shown that bleed actuation alters the production, accumulation, and advection of vorticity concentrations near the surface with significant effects on the evolution, and, in particular, the timing of dynamic stall vortices. These changes are manifested by alteration of the lift hysteresis and improvement of pitch stability during the cycle, while maintaining cycle-averaged lift to within 5% of the base flow level with significant implications for improvement of the stability of flexible wings and rotor blades. This work is supported by the Rotorcraft Center (VLRCOE) at Georgia Tech.

  5. The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces

    PubMed Central

    Dimitriadis, Grigorios; Nudds, Robert L.

    2016-01-01

    The diversity of wing morphologies in birds reflects their variety of flight styles and the associated aerodynamic and inertial requirements. Although the aerodynamics underlying wing morphology can be informed by aeronautical research, important differences exist between planes and birds. In particular, birds operate at lower, transitional Reynolds numbers than do most aircraft. To date, few quantitative studies have investigated the aerodynamic performance of avian wings as fixed lifting surfaces and none have focused upon the differences between wings from different flight style groups. Dried wings from 10 bird species representing three distinct flight style groups were mounted on a force/torque sensor within a wind tunnel in order to test the hypothesis that wing morphologies associated with different flight styles exhibit different aerodynamic properties. Morphological differences manifested primarily as differences in drag rather than lift. Maximum lift coefficients did not differ between groups, whereas minimum drag coefficients were lowest in undulating flyers (Corvids). The lift to drag ratios were lower than in conventional aerofoils and data from free-flying soaring species; particularly in high frequency, flapping flyers (Anseriformes), which do not rely heavily on glide performance. The results illustrate important aerodynamic differences between the wings of different flight style groups that cannot be explained solely by simple wing-shape measures. Taken at face value, the results also suggest that wing-shape is linked principally to changes in aerodynamic drag, but, of course, it is aerodynamics during flapping and not gliding that is likely to be the primary driver. PMID:27781155

  6. Investigation of aerodynamic braking devices for wind turbine applications

    SciTech Connect

    Griffin, D.A.

    1997-04-01

    This report documents the selection and preliminary design of a new aerodynamic braking system for use on the stall-regulated AWT-26/27 wind turbines. The goal was to identify and design a configuration that offered improvements over the existing tip brake used by Advanced Wind Turbines, Inc. (AWT). Although the design objectives and approach of this report are specific to aerodynamic braking of AWT-26/27 turbines, many of the issues addressed in this work are applicable to a wider class of turbines. The performance trends and design choices presented in this report should be of general use to wind turbine designers who are considering alternative aerodynamic braking methods. A literature search was combined with preliminary work on device sizing, loads and mechanical design. Candidate configurations were assessed on their potential for benefits in the areas of cost, weight, aerodynamic noise, reliability and performance under icing conditions. As a result, two configurations were identified for further study: the {open_quotes}spoiler-flap{close_quotes} and the {open_quotes}flip-tip.{close_quotes} Wind tunnel experiments were conducted at Wichita State University to evaluate the performance of the candidate aerodynamic brakes on an airfoil section representative of the AWT-26/27 blades. The wind tunnel data were used to predict the braking effectiveness and deployment characteristics of the candidate devices for a wide range of design parameters. The evaluation was iterative, with mechanical design and structural analysis being conducted in parallel with the braking performance studies. The preliminary estimate of the spoiler-flap system cost was $150 less than the production AWT-26/27 tip vanes. This represents a reduction of approximately 5 % in the cost of the aerodynamic braking system. In view of the preliminary nature of the design, it would be prudent to plan for contingencies in both cost and weight.

  7. Concurrent endurance and explosive type strength training increases activation and fast force production of leg extensor muscles in endurance athletes.

    PubMed

    Mikkola, Jussi S; Rusko, Heikki K; Nummela, Ari T; Paavolainen, Leena M; Häkkinen, Keijo

    2007-05-01

    The purpose of this experiment was to examine the effects of concurrent endurance and explosive strength training on electromyography (EMG) and force production of leg extensors, sport-specific rapid force production, aerobic capacity, and work economy in cross-country skiers. Nineteen male cross-country skiers were assigned to an experimental group (E, n = 8) or a control group (C, n = 11). The E group trained for 8 weeks with the same total training volume as C, but 27% of endurance training in E was replaced by explosive strength training. The skiers were measured at pre- and post training for concentric and isometric force-time parameters of leg extensors and EMG activity from the vastus lateralis (VL) and medialis (VM) muscles. Sport-specific rapid force production was measured by performing a 30-m double poling test with the maximal velocity (V(30DP)) and sport-specific endurance economy by constant velocity 2-km double poling test (CVDP) and performance (V(2K)) by 2-km maximal double poling test with roller skis on an indoor track. Maximal oxygen uptake (Vo(2)max) was determined during the maximal treadmill walking test with the poles. The early absolute forces (0-100 ms) in the force-time curve in isometric action increased in E by 18 +/- 22% (p < 0.05), with concomitant increases in the average integrated EMG (IEMG) (0-100 ms) of VL by 21 +/- 21% (p < 0.05). These individual changes in the average IEMG of VL correlated with the changes in early force (r = 0.86, p < 0.01) in E. V(30DP) increased in E (1.4 +/- 1.6%) (p < 0.05) but not in C. The V(2K) increased in C by 2.9 +/- 2.8% (p < 0.01) but not significantly in E (5.5 +/- 5.8%, p < 0.1). However, the steady-state oxygen consumption in CVDP decreased in E by 7 +/- 6% (p < 0.05). No significant changes occurred in Vo(2)max either in E or in C. The present concurrent explosive strength and endurance training in endurance athletes produced improvements in explosive force associated with increased rapid

  8. The Contribution of the C-Terminal Tails of Microtubules in Altering the Force Production Specifications of Multiple Kinesin-1.

    PubMed

    Feizabadi, Mitra Shojania

    2016-09-01

    The extent to which beta tubulin isotypes contribute to the function of microtubules and the microtubule-driven transport of molecular motors is poorly understood. The major differences in these isotypes are associated with the structure of their C-terminal tails. Recent studies have revealed a few aspects of the C-terminal tails' regulatory role on the activities of some of the motor proteins on a single-molecule level. However, little attention is given to the degree to which the function of a team of motor proteins can be altered by the microtubule's tail. In a set of parallel experiments, we investigated this open question by studying the force production of several kinesin-1 (kinesin) molecular motors along two groups of microtubules: regular ones and those microtubules whose C-terminals are cleaved by subtilisin digestion. The results indicate that the difference between the average of the force production of motors along two types of microtubules is statistically significant. The underlying mechanism of such production is substantially different as well. As compared to untreated microtubules, the magnitude of the binding time of several kinesin-1 is almost three times greater along subtilisin-treated microtubules. Also, the velocity of the group of kinesin molecules shows a higher sensitivity to external loads and reduces significantly under higher loads along subtilisin-treated microtubules. Together, this work shows the capacity of the tails in fine-tuning the force production characteristics of several kinesin molecules.

  9. The Contribution of the C-Terminal Tails of Microtubules in Altering the Force Production Specifications of Multiple Kinesin-1.

    PubMed

    Feizabadi, Mitra Shojania

    2016-09-01

    The extent to which beta tubulin isotypes contribute to the function of microtubules and the microtubule-driven transport of molecular motors is poorly understood. The major differences in these isotypes are associated with the structure of their C-terminal tails. Recent studies have revealed a few aspects of the C-terminal tails' regulatory role on the activities of some of the motor proteins on a single-molecule level. However, little attention is given to the degree to which the function of a team of motor proteins can be altered by the microtubule's tail. In a set of parallel experiments, we investigated this open question by studying the force production of several kinesin-1 (kinesin) molecular motors along two groups of microtubules: regular ones and those microtubules whose C-terminals are cleaved by subtilisin digestion. The results indicate that the difference between the average of the force production of motors along two types of microtubules is statistically significant. The underlying mechanism of such production is substantially different as well. As compared to untreated microtubules, the magnitude of the binding time of several kinesin-1 is almost three times greater along subtilisin-treated microtubules. Also, the velocity of the group of kinesin molecules shows a higher sensitivity to external loads and reduces significantly under higher loads along subtilisin-treated microtubules. Together, this work shows the capacity of the tails in fine-tuning the force production characteristics of several kinesin molecules. PMID:27503105

  10. Population studies should reflect the criterion of productive forces and the viewpoint of a market-oriented economy.

    PubMed

    Peng, X

    1989-01-01

    This commentary is on the role of population studies in a market oriented economy which reflects Marxist theories on productive forces. Population development must not be viewed unidimensionally. Prior thinking focused on the mode of social production determining population development and vice versa. The assumption prevalent prior to 1978 was that there was no common pattern among different societies. This view was openly challenged in the 2nd national population science symposium in Chengdu, Sichuan Province. It was stated that population development is affected by production techniques in either capitalist or socialist countries. Further understanding of this relationship based on quantitative and qualitative research was required. Public ownership is the basis of a socialist economy. Marxist views were that populations in market or nonmarket economies are different, and population scholars need to study these relationships. There was a mistaken belief that a socialist economy was nonmarket oriented. Correcting the mistake meant taking into consideration migration, urbanization, employment, expenditure, and the relationship to reproduction, as well as rethinking the development patterns. When the price of the labor force differs from its value, the investment in population and population quality will be affected. This has led to rampant commercialization and higher school dropout rates. Short term interests predominate. The trend does not benefit the quality of the population or the promotion of social productive forces. Further examination is needed of the effects of urbanization on a planned market oriented economy with socialist public ownership. PMID:12316994

  11. LTSTAR- SUPERSONIC WING NON-LINEAR AERODYNAMICS PROGRAM

    NASA Technical Reports Server (NTRS)

    Carlson, H. W.

    1994-01-01

    The Supersonic Wing Nonlinear Aerodynamics computer program, LTSTAR, was developed to provide for the estimation of the nonlinear aerodynamic characteristics of a wing at supersonic speeds. This corrected linearized-theory method accounts for nonlinearities in the variation of basic pressure loadings with local surface slopes, predicts the degree of attainment of theoretical leading-edge thrust forces, and provides an estimate of detached leading-edge vortex loadings that result when the theoretical thrust forces are not fully realized. Comparisons of LTSTAR computations with experimental results show significant improvements in detailed wing pressure distributions, particularly for large angles of attack and for regions of the wing where the flow is highly three-dimensional. The program provides generally improved predictions of the wing overall force and moment coefficients. LTSTAR could be useful in design studies aimed at aerodynamic performance optimization and for providing more realistic trade-off information for selection of wing planform geometry and airfoil section parameters. Input to the LTSTAR program includes wing planform data, freestream conditions, wing camber, wing thickness, scaling options, and output options. Output includes pressure coefficients along each chord, section normal and axial force coefficients, and the spanwise distribution of section force coefficients. With the chordwise distributions and section coefficients at each angle of attack, three sets of polars are output. The first set is for linearized theory with and without full leading-edge thrust, the second set includes nonlinear corrections, and the third includes estimates of attainable leading-edge thrust and vortex increments along with the nonlinear corrections. The LTSTAR program is written in FORTRAN IV for batch execution and has been implemented on a CDC 6000 series computer with a central memory requirement of approximately 150K (octal) of 60 bit words. The LTSTAR

  12. Transient platoon aerodynamics and bluff body flows

    NASA Astrophysics Data System (ADS)

    Tsuei, Lun

    There are two components of this experimental work: transient vehicle platoon aerodynamics and bluff-body flows. The transient aerodynamic effects in a four-vehicle platoon during passing maneuvers and in-line oscillations are investigated. A vehicle model is moved longitudinally parallel to a four-car platoon to simulate passing maneuvers. The drag and side forces experienced by each platoon member are measured using strain gauge balances. The resulting data are presented as dimensionless coefficients. It is shown that each car in the platoon experiences a repulsive side force when the passing vehicle is in the neighborhood of its rear half. The side force reverses its direction and becomes an attractive force when the passing vehicle moves to the neighborhood of its front half. The drag force experienced by each platoon member is increased when the passing vehicle is in its proximity. The effects of the lateral spacing and relative velocity between the platoon and the passing vehicle, as well as the shape of the passing vehicle, are also investigated. Similar trends are observed in simulations of both a vehicle passing a platoon and a platoon overtaking a vehicle. During the in-line oscillation experiments, one of the four platoon members is forced to undergo longitudinal periodic motions. The drag force experienced by each platoon member is determined simultaneously during the oscillations. The effects of the location of the oscillating vehicle, the shape of the vehicles and the displacement and velocity amplitudes of the oscillation are examined. The results from the transient conditions are compared to those from the steady tests in the same setup. In the case of a four-car platoon, the drag variations experienced by the vehicles adjacent to the oscillating vehicle are discussed using a cavity model. It is found that when the oscillating car moves forward and approaches its upstream neighbor, itself and its downstream neighbor experiences an increased drag

  13. Recent progress in flapping wing aerodynamics and aeroelasticity

    NASA Astrophysics Data System (ADS)

    Shyy, W.; Aono, H.; Chimakurthi, S. K.; Trizila, P.; Kang, C.-K.; Cesnik, C. E. S.; Liu, H.

    2010-10-01

    Micro air vehicles (MAVs) have the potential to revolutionize our sensing and information gathering capabilities in areas such as environmental monitoring and homeland security. Flapping wings with suitable wing kinematics, wing shapes, and flexible structures can enhance lift as well as thrust by exploiting large-scale vortical flow structures under various conditions. However, the scaling invariance of both fluid dynamics and structural dynamics as the size changes is fundamentally difficult. The focus of this review is to assess the recent progress in flapping wing aerodynamics and aeroelasticity. It is realized that a variation of the Reynolds number (wing sizing, flapping frequency, etc.) leads to a change in the leading edge vortex (LEV) and spanwise flow structures, which impacts the aerodynamic force generation. While in classical stationary wing theory, the tip vortices (TiVs) are seen as wasted energy, in flapping flight, they can interact with the LEV to enhance lift without increasing the power requirements. Surrogate modeling techniques can assess the aerodynamic outcomes between two- and three-dimensional wing. The combined effect of the TiVs, the LEV, and jet can improve the aerodynamics of a flapping wing. Regarding aeroelasticity, chordwise flexibility in the forward flight can substantially adjust the projected area normal to the flight trajectory via shape deformation, hence redistributing thrust and lift. Spanwise flexibility in the forward flight creates shape deformation from the wing root to the wing tip resulting in varied phase shift and effective angle of attack distribution along the wing span. Numerous open issues in flapping wing aerodynamics are highlighted.

  14. β-Alanine supplementation enhances human skeletal muscle relaxation speed but not force production capacity.

    PubMed

    Hannah, Ricci; Stannard, Rebecca Louise; Minshull, Claire; Artioli, Guilherme Giannini; Harris, Roger Charles; Sale, Craig

    2015-03-01

    β-Alanine (BA) supplementation improves human exercise performance. One possible explanation for this is an enhancement of muscle contractile properties, occurring via elevated intramuscular carnosine resulting in improved calcium sensitivity and handling. This study investigated the effect of BA supplementation on in vivo contractile properties and voluntary neuromuscular performance. Twenty-three men completed two experimental sessions, pre- and post-28 days supplementation with 6.4 g/day of BA (n = 12) or placebo (PLA; n = 11). During each session, force was recorded during a series of knee extensor contractions: resting and potentiated twitches and octet (8 pulses, 300 Hz) contractions elicited via femoral nerve stimulation; tetanic contractions (1 s, 1-100 Hz) via superficial muscle stimulation; and maximum and explosive voluntary contractions. BA supplementation had no effect on the force-frequency relationship, or the force responses (force at 25 and 50 ms from onset, peak force) of resting or potentiated twitches, and octet contractions (P > 0.05). Resting and potentiated twitch electromechanical delay and time-to-peak tension were unaffected by BA supplementation (P > 0.05), although half-relaxation time declined by 7-12% (P < 0.05). Maximum and explosive voluntary forces were unchanged after BA supplementation. BA supplementation had no effect on evoked force responses, implying that altered calcium sensitivity and/or release are not the mechanisms by which BA supplementation influences exercise performance. The reduced half-relaxation time with BA supplementation might, however, be explained by enhanced reuptake of calcium, which has implications for the efficiency of muscle contraction following BA supplementation.

  15. Computational fluid dynamics framework for aerodynamic model assessment

    NASA Astrophysics Data System (ADS)

    Vallespin, D.; Badcock, K. J.; Da Ronch, A.; White, M. D.; Perfect, P.; Ghoreyshi, M.

    2012-07-01

    This paper reviews the work carried out at the University of Liverpool to assess the use of CFD methods for aircraft flight dynamics applications. Three test cases are discussed in the paper, namely, the Standard Dynamic Model, the Ranger 2000 jet trainer and the Stability and Control Unmanned Combat Air Vehicle. For each of these, a tabular aerodynamic model based on CFD predictions is generated along with validation against wind tunnel experiments and flight test measurements. The main purpose of the paper is to assess the validity of the tables of aerodynamic data for the force and moment prediction of realistic aircraft manoeuvres. This is done by generating a manoeuvre based on the tables of aerodynamic data, and then replaying the motion through a time-accurate computational fluid dynamics calculation. The resulting forces and moments from these simulations were compared with predictions from the tables. As the latter are based on a set of steady-state predictions, the comparisons showed perfect agreement for slow manoeuvres. As manoeuvres became more aggressive some disagreement was seen, particularly during periods of large rates of change in attitudes. Finally, the Ranger 2000 model was used on a flight simulator.

  16. Wind Tunnel Tests on Aerodynamic Characteristics of Advanced Solid Rocket

    NASA Astrophysics Data System (ADS)

    Kitamura, Keiichi; Fujimoto, Keiichiro; Nonaka, Satoshi; Irikado, Tomoko; Fukuzoe, Moriyasu; Shima, Eiji

    The Advanced Solid Rocket is being developed by JAXA (Japan Aerospace Exploration Agency). Since its configuration has been changed very recently, its aerodynamic characteristics are of great interest of the JAXA Advanced Solid Rocket Team. In this study, we carried out wind tunnel tests on the aerodynamic characteristics of the present configuration for Mach 1.5. Six test cases were conducted with different body configurations, attack angles, and roll angles. A six component balance, oilflow visualization, Schlieren images were used throughout the experiments. It was found that, at zero angle-of-attack, the flow around the body were perturbed and its drag (axial force) characteristics were significantly influenced by protruding body components such as flanges, cable ducts, and attitude control units of SMSJ (Solid Motor Side Jet), while the nozzle had a minor role. With angle-of-attack of five degree, normal force of CNα = 3.50±0.03 was measured along with complex flow features observed in the full-component model; whereas no crossflow separations were induced around the no-protuberance model with CNα = 2.58±0.10. These values were almost constant with respect to the angle-of-attack in both of the cases. Furthermore, presence of roll angle made the flow more complicated, involving interactions of separation vortices. These data provide us with fundamental and important aerodynamic insights of the Advanced Solid Rocket, and they will be utilized as reference data for the corresponding numerical analysis.

  17. On-orbit free molecular flow aerodynamic characteristics of a proposal space operations center configuration

    NASA Technical Reports Server (NTRS)

    Romere, P. O.

    1982-01-01

    A proposed configuration for a Space Operations Center is presented in its eight stages of buildup. The on orbit aerodynamic force and moment characteristics were calculated for each stage based upon free molecular flow theory. Calculation of the aerodynamic characteristics was accomplished through the use of an orbital aerodynamic computer program, and the computation method is described with respect to the free molecular theory used. The aerodynamic characteristics are presented in tabulated form for each buildup stage at angles of attack from 0 to 360 degrees and roll angles from -60 to +60 degrees. The reference altitude is 490 kilometers, however, the data should be applicable for altitudes below 490 kilometers down to approximately 185 kilometers.

  18. Bilateral deficit in explosive force production is not caused by changes in agonist neural drive.

    PubMed

    Buckthorpe, Matthew W; Pain, Matthew T G; Folland, Jonathan P

    2013-01-01

    Bilateral deficit (BLD) describes the phenomenon of a reduction in performance during synchronous bilateral (BL) movements when compared to the sum of identical unilateral (UL) movements. Despite a large body of research investigating BLD of maximal voluntary force (MVF) there exist a paucity of research examining the BLD for explosive strength. Therefore, this study investigated the BLD in voluntary and electrically-evoked explosive isometric contractions of the knee extensors and assessed agonist and antagonist neuromuscular activation and measurement artefacts as potential mechanisms. Thirteen healthy untrained males performed a series of maximum and explosive voluntary contractions bilaterally (BL) and unilaterally (UL). UL and BL evoked twitch and octet contractions were also elicited. Two separate load cells were used to measure MVF and explosive force at 50, 100 and 150 ms after force onset. Surface EMG amplitude was measured from three superficial agonists and an antagonist. Rate of force development (RFD) and EMG were reported over consecutive 50 ms periods (0-50, 50-100 and 100-150 ms). Performance during UL contractions was compared to combined BL performance to measure BLD. Single limb performance during the BL contractions was assessed and potential measurement artefacts, including synchronisation of force onset from the two limbs, controlled for. MVF showed no BLD (P = 0.551), but there was a BLD for explosive force at 100 ms (11.2%, P = 0.007). There was a BLD in RFD 50-100 ms (14.9%, P = 0.004), but not for the other periods. Interestingly, there was a BLD in evoked force measures (6.3-9.0%, P<0.001). There was no difference in agonist or antagonist EMG for any condition (P≥0.233). Measurement artefacts contributed minimally to the observed BLD. The BLD in volitional explosive force found here could not be explained by measurement issues, or agonist and antagonist neuromuscular activation. The BLD in voluntary and evoked explosive force might

  19. Techniques for estimating Space Station aerodynamic characteristics

    NASA Technical Reports Server (NTRS)

    Thomas, Richard E.

    1993-01-01

    A method was devised and calculations were performed to determine the effects of reflected molecules on the aerodynamic force and moment coefficients for a body in free molecule flow. A procedure was developed for determining the velocity and temperature distributions of molecules reflected from a surface of arbitrary momentum and energy accommodation. A system of equations, based on momentum and energy balances for the surface, incident, and reflected molecules, was solved by a numerical optimization technique. The minimization of a 'cost' function, developed from the set of equations, resulted in the determination of the defining properties of the flow reflected from the arbitrary surface. The properties used to define both the incident and reflected flows were: average temperature of the molecules in the flow, angle of the flow with respect to a vector normal to the surface, and the molecular speed ratio. The properties of the reflected flow were used to calculate the contribution of multiply reflected molecules to the force and moments on a test body in the flow. The test configuration consisted of two flat plates joined along one edge at a right angle to each other. When force and moment coefficients of this 90 deg concave wedge were compared to results that did not include multiple reflections, it was found that multiple reflections could nearly double lift and drag coefficients, with nearly a 50 percent increase in pitching moment for cases with specular or nearly specular accommodation. The cases of diffuse or nearly diffuse accommodation often had minor reductions in axial and normal forces when multiple reflections were included. There were several cases of intermediate accommodation where the addition of multiple reflection effects more than tripled the lift coefficient over the convex technique.

  20. Computer Simulation of Aircraft Aerodynamics

    NASA Technical Reports Server (NTRS)

    Inouye, Mamoru

    1989-01-01

    The role of Ames Research Center in conducting basic aerodynamics research through computer simulations is described. The computer facilities, including supercomputers and peripheral equipment that represent the state of the art, are described. The methodology of computational fluid dynamics is explained briefly. Fundamental studies of turbulence and transition are being pursued to understand these phenomena and to develop models that can be used in the solution of the Reynolds-averaged Navier-Stokes equations. Four applications of computer simulations for aerodynamics problems are described: subsonic flow around a fuselage at high angle of attack, subsonic flow through a turbine stator-rotor stage, transonic flow around a flexible swept wing, and transonic flow around a wing-body configuration that includes an inlet and a tail.

  1. Viking entry aerodynamics and heating

    NASA Technical Reports Server (NTRS)

    Polutchko, R. J.

    1974-01-01

    The characteristics of the Mars entry including the mission sequence of events and associated spacecraft weights are described along with the Viking spacecraft. Test data are presented for the aerodynamic characteristics of the entry vehicle showing trimmed alpha, drag coefficient, and trimmed lift to drag ratio versus Mach number; the damping characteristics of the entry configuration; the angle of attack time history of Viking entries; stagnation heating and pressure time histories; and the aeroshell heating distribution as obtained in tests run in a shock tunnel for various gases. Flight tests which demonstrate the aerodynamic separation of the full-scale aeroshell and the flying qualities of the entry configuration in an uncontrolled mode are documented. Design values selected for the heat protection system based on the test data and analysis performed are presented.

  2. Aerodynamic investigation by infrared imaging

    NASA Technical Reports Server (NTRS)

    Roberts, A. Sidney, Jr.; Mcree, Griffith J.; Gartenberg, Ehud

    1988-01-01

    Infrared imaging systems can be used to measure temperatures of actively heated bodies immersed in an airstream. This monitoring of the convective heat transfer process, provides also information about the interaction between the body and the flow. The concept appeals to Nusselt/Reynolds numbers relations in order to produce data of interest from surface temperatures. Two test cases are presented and reference is made to analytical results: the mapping of a laminar jet and the temperature distribution along a constant power heated flat plate in laminar boundary layer regime. Although this research is currently focused on low speed aerodynamics, the extension to high speed aerodynamics, where the body undergoes frictional heating is of interest in this context, too.

  3. Aerodynamic instability: A case history

    NASA Technical Reports Server (NTRS)

    Eisenmann, R. C.

    1985-01-01

    The identification, diagnosis, and final correction of complex machinery malfunctions typically require the correlation of many parameters such as mechanical construction, process influence, maintenance history, and vibration response characteristics. The progression is reviewed of field testing, diagnosis, and final correction of a specific machinery instability problem. The case history presented addresses a unique low frequency instability problem on a high pressure barrel compressor. The malfunction was eventually diagnosed as a fluidic mechanism that manifested as an aerodynamic disturbance to the rotor assembly.

  4. Aerodynamic Design Using Neural Networks

    NASA Technical Reports Server (NTRS)

    Rai, Man Mohan; Madavan, Nateri K.

    2003-01-01

    The design of aerodynamic components of aircraft, such as wings or engines, involves a process of obtaining the most optimal component shape that can deliver the desired level of component performance, subject to various constraints, e.g., total weight or cost, that the component must satisfy. Aerodynamic design can thus be formulated as an optimization problem that involves the minimization of an objective function subject to constraints. A new aerodynamic design optimization procedure based on neural networks and response surface methodology (RSM) incorporates the advantages of both traditional RSM and neural networks. The procedure uses a strategy, denoted parameter-based partitioning of the design space, to construct a sequence of response surfaces based on both neural networks and polynomial fits to traverse the design space in search of the optimal solution. Some desirable characteristics of the new design optimization procedure include the ability to handle a variety of design objectives, easily impose constraints, and incorporate design guidelines and rules of thumb. It provides an infrastructure for variable fidelity analysis and reduces the cost of computation by using less-expensive, lower fidelity simulations in the early stages of the design evolution. The initial or starting design can be far from optimal. The procedure is easy and economical to use in large-dimensional design space and can be used to perform design tradeoff studies rapidly. Designs involving multiple disciplines can also be optimized. Some practical applications of the design procedure that have demonstrated some of its capabilities include the inverse design of an optimal turbine airfoil starting from a generic shape and the redesign of transonic turbines to improve their unsteady aerodynamic characteristics.

  5. Rudolf Hermann, wind tunnels and aerodynamics

    NASA Astrophysics Data System (ADS)

    Lundquist, Charles A.; Coleman, Anne M.

    2008-04-01

    Rudolf Hermann was born on December 15, 1904 in Leipzig, Germany. He studied at the University of Leipzig and at the Aachen Institute of Technology. His involvement with wind tunnels began in 1934 when Professor Carl Wieselsberger engaged him to work at Aachen on the development of a supersonic wind tunnel. On January 6, 1936, Dr. Wernher von Braun visited Dr. Hermann to arrange for use of the Aachen supersonic wind tunnel for Army problems. On April 1, 1937, Dr. Hermann became Director of the Supersonic Wind Tunnel at the Army installation at Peenemunde. Results from the Aachen and Peenemunde wind tunnels were crucial in achieving aerodynamic stability for the A-4 rocket, later designated as the V-2. Plans to build a Mach 10 'hypersonic' wind tunnel facility at Kochel were accelerated after the Allied air raid on Peenemunde on August 17, 1943. Dr. Hermann was director of the new facility. Ignoring destruction orders from Hitler as WWII approached an end in Europe, Dr. Hermann and his associates hid documents and preserved wind tunnel components that were acquired by the advancing American forces. Dr. Hermann became a consultant to the Air Force at its Wright Field in November 1945. In 1951, he was named professor of Aeronautical Engineering at the University of Minnesota. In 1962, Dr. Hermann became the first Director of the Research Institute at the University of Alabama in Huntsville (UAH), a position he held until he retired in 1970.

  6. Aerodynamic Flow Control of a Maneuvering Airfoil

    NASA Astrophysics Data System (ADS)

    Brzozowski, Daniel P.; Culp, John; Glezer, Ari

    2010-11-01

    The unsteady aerodynamic forces and moments on a maneuvering, free-moving airfoil are varied in wind tunnel experiments by controlling vorticity generation/accumulation near the surface using hybrid synthetic jet actuators. The dynamic characteristics of the airfoil that is mounted on a 2-DOF traverse are controlled using position and attitude feedback loops that are actuated by servo motors. Bi-directional changes in the pitching moment are induced using controllable trapped vorticity concentrations on the suction and pressure surfaces near the trailing edge. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and velocity measurements that are taken phase-locked to the commanded actuation waveform. The time scales associated with the actuation process is determined from PIV measurements of vorticity flux downstream of the trailing edge. Circulation time history shows that the entire flow over the airfoil readjusts within about 1.5 TCONV, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales commensurate with the flow's convective time scale, and that the maneuver response is only limited by the inertia of the platform. Supported by AFSOR.

  7. Baseball Aerodynamics: What do we know and how do we know it?

    NASA Astrophysics Data System (ADS)

    Nathan, Alan

    2009-11-01

    Baseball aerodynamics is governed by three phenomenological quantities: the coefficients of drag, lift, and moment, the latter determining the spin decay time constant. In past years, these quantities were studied mainly in wind tunnel experiments, whereby the forces on the baseball are measured directly. More recently, new tools are being used that focus on measuring accurate baseball trajectories, from which the forces can be inferred. These tools include high-speed motion analysis, video tracking of pitched baseballs (the PITCHf/x system), and Doppler radar tracking. In this contribution, I will discuss what these new tools are teaching us about baseball aerodynamics.

  8. Applied aerodynamics: Challenges and expectations

    NASA Technical Reports Server (NTRS)

    Peterson, Victor L.; Smith, Charles A.

    1993-01-01

    Aerospace is the leading positive contributor to this country's balance of trade, derived largely from the sale of U.S. commercial aircraft around the world. This powerfully favorable economic situation is being threatened in two ways: (1) the U.S. portion of the commercial transport market is decreasing, even though the worldwide market is projected to increase substantially; and (2) expenditures are decreasing for military aircraft, which often serve as proving grounds for advanced aircraft technology. To retain a major share of the world market for commercial aircraft and continue to provide military aircraft with unsurpassed performance, the U.S. aerospace industry faces many technological challenges. The field of applied aerodynamics is necessarily a major contributor to efforts aimed at meeting these technological challenges. A number of emerging research results that will provide new opportunities for applied aerodynamicists are discussed. Some of these have great potential for maintaining the high value of contributions from applied aerodynamics in the relatively near future. Over time, however, the value of these contributions will diminish greatly unless substantial investments continue to be made in basic and applied research efforts. The focus: to increase understanding of fluid dynamic phenomena, identify new aerodynamic concepts, and provide validated advanced technology for future aircraft.

  9. X-34 Vehicle Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Brauckmann, Gregory J.

    1998-01-01

    The X-34, being designed and built by the Orbital Sciences Corporation, is an unmanned sub-orbital vehicle designed to be used as a flying test bed to demonstrate key vehicle and operational technologies applicable to future reusable launch vehicles. The X-34 will be air-launched from an L-1011 carrier aircraft at approximately Mach 0.7 and 38,000 feet altitude, where an onboard engine will accelerate the vehicle to speeds above Mach 7 and altitudes to 250,000 feet. An unpowered entry will follow, including an autonomous landing. The X-34 will demonstrate the ability to fly through inclement weather, land horizontally at a designated site, and have a rapid turn-around capability. A series of wind tunnel tests on scaled models was conducted in four facilities at the NASA Langley Research Center to determine the aerodynamic characteristics of the X-34. Analysis of these test results revealed that longitudinal trim could be achieved throughout the design trajectory. The maximum elevon deflection required to trim was only half of that available, leaving a margin for gust alleviation and aerodynamic coefficient uncertainty. Directional control can be achieved aerodynamically except at combined high Mach numbers and high angles of attack, where reaction control jets must be used. The X-34 landing speed, between 184 and 206 knots, is within the capabilities of the gear and tires, and the vehicle has sufficient rudder authority to control the required 30-knot crosswind.

  10. Maximum likelihood identification of aircraft parameters with unsteady aerodynamic modelling

    NASA Technical Reports Server (NTRS)

    Keskar, D. A.; Wells, W. R.

    1979-01-01

    A simplified aerodynamic force model based on the physical principle of Prandtl's lifting line theory and trailing vortex concept has been developed to account for unsteady aerodynamic effects in aircraft dynamics. Longitudinal equations of motion have been modified to include these effects. The presence of convolution integrals in the modified equations of motion led to a frequency domain analysis utilizing Fourier transforms. This reduces the integro-differential equations to relatively simple algebraic equations, thereby reducing computation time significantly. A parameter extraction program based on the maximum likelihood estimation technique is developed in the frequency domain. The extraction algorithm contains a new scheme for obtaining sensitivity functions by using numerical differentiation. The paper concludes with examples using computer generated and real flight data

  11. DSMC Simulations of Apollo Capsule Aerodynamics for Hypersonic Rarefied Conditions

    NASA Technical Reports Server (NTRS)

    Moss, James N.; Glass, Christopher E.; Greene, Francis A.

    2006-01-01

    Direct simulation Monte Carlo DSMC simulations are performed for the Apollo capsule in the hypersonic low density transitional flow regime. The focus is on ow conditions similar to that experienced by the Apollo Command Module during the high altitude portion of its reentry Results for aerodynamic forces and moments are presented that demonstrate their sensitivity to rarefaction that is for free molecular to continuum conditions. Also aerodynamic data are presented that shows their sensitivity to a range of reentry velocity encompasing conditions that include reentry from low Earth orbit lunar return and Mars return velocities to km/s. The rarefied results are anchored in the continuum regime with data from Navier Stokes simulations

  12. Aerodynamics of slender finned bodies at large angles of attack

    NASA Technical Reports Server (NTRS)

    Agnone, A. M.; Zakkay, V.; Tory, E.; Stallings, R.

    1977-01-01

    In certain missions finned missiles perform slewing maneuvers. Here, large angles of attack are attained. Experimental data needed to understand the aerodynamics of such vehicles are presented. The purpose of this investigation was to study the interaction of the body flow field with that produced by the fins and the resulting effects on the aerodynamic forces and moments. The experiments were conducted at a nominal Mach number of 2.7 and angles of attack from 0 to 50 deg, with two different models. The tests were performed in a range of Reynolds number from 1.5 x 10 to the 6th to 4 x 10 to the 7th per foot (to cover both the laminar and fully turbulent regimes.) Several fin roll angles were investigated. Static pressures on both body and fin surfaces are reported.

  13. Unsteady aerodynamics of vortical flows: Early and recent developments

    NASA Technical Reports Server (NTRS)

    Atassi, H. M.

    1994-01-01

    The development of aerodynamic theories of streaming motions around bodies with unsteady vortical and entropic disturbances is reviewed. The basic concepts associated with such motions, their interaction with solid boundaries and their noise generating mechanisms are described. The theory was first developed in the approximation wherein the unsteady flow is linearized about a uniform mean lfow. This approach has been extensively developed and used in aeroelastic and aeroacoustic calculations. The theory was recently extended to account for the effect of distortion of the incident disturbances by the nonuniform mean flow around the body. This effect is found to have a significant influence on the unsteady aerodynamic force along the body surface and the sound radiated in the far field. Finally, the nonlinear characteristics of unsteady transonic flows are reviewed and recent results of linear and nonlinear computations are presented.

  14. The effects of height and distance on the force production and acceleration in martial arts strikes.

    PubMed

    Bolander, Richard P; Neto, Osmar Pinto; Bir, Cynthia A

    2009-11-01

    Almost all cultures have roots in some sort of self defence system and yet there is relatively little research in this area, outside of a sports related environment. This project investigated different applications of strikes from Kung Fu practitioners that have not been addressed before in the literature. Punch and palm strikes were directly compared from different heights and distances, with the use of a load cell, accelerometers, and high speed video. The data indicated that the arm accelerations of both strikes were similar, although the force and resulting acceleration of the target were significantly greater for the palm strikes. Additionally, the relative height at which the strike was delivered was also investigated. The overall conclusion is that the palm strike is a more effective strike for transferring force to an object. It can also be concluded that an attack to the chest would be ideal for maximizing impact force and moving an opponent off balance. Key PointsIt has been determined that the palm strike is more effective than the punch for developing force and for transferring momentum, most likely the result of a reduced number of rigid links and joints.A strike at head level is less effective than a strike at chest level for developing force and transferring momentum.Distance plays an effect on the overall force and momentum changes, and most likely is dependent on the velocity of the limb and alignment of the bones prior to impact.The teaching of self defence for novices and law enforcement would benefit from including the palm strike as a high priority technique.

  15. The Effects of Height and Distance on the Force Production and Acceleration in Martial Arts Strikes

    PubMed Central

    Bolander, Richard P.; Neto, Osmar Pinto; Bir, Cynthia A.

    2009-01-01

    Almost all cultures have roots in some sort of self defence system and yet there is relatively little research in this area, outside of a sports related environment. This project investigated different applications of strikes from Kung Fu practitioners that have not been addressed before in the literature. Punch and palm strikes were directly compared from different heights and distances, with the use of a load cell, accelerometers, and high speed video. The data indicated that the arm accelerations of both strikes were similar, although the force and resulting acceleration of the target were significantly greater for the palm strikes. Additionally, the relative height at which the strike was delivered was also investigated. The overall conclusion is that the palm strike is a more effective strike for transferring force to an object. It can also be concluded that an attack to the chest would be ideal for maximizing impact force and moving an opponent off balance. Key Points It has been determined that the palm strike is more effective than the punch for developing force and for transferring momentum, most likely the result of a reduced number of rigid links and joints. A strike at head level is less effective than a strike at chest level for developing force and transferring momentum. Distance plays an effect on the overall force and momentum changes, and most likely is dependent on the velocity of the limb and alignment of the bones prior to impact. The teaching of self defence for novices and law enforcement would benefit from including the palm strike as a high priority technique. PMID:24474886

  16. The effects of height and distance on the force production and acceleration in martial arts strikes.

    PubMed

    Bolander, Richard P; Neto, Osmar Pinto; Bir, Cynthia A

    2009-11-01

    Almost all cultures have roots in some sort of self defence system and yet there is relatively little research in this area, outside of a sports related environment. This project investigated different applications of strikes from Kung Fu practitioners that have not been addressed before in the literature. Punch and palm strikes were directly compared from different heights and distances, with the use of a load cell, accelerometers, and high speed video. The data indicated that the arm accelerations of both strikes were similar, although the force and resulting acceleration of the target were significantly greater for the palm strikes. Additionally, the relative height at which the strike was delivered was also investigated. The overall conclusion is that the palm strike is a more effective strike for transferring force to an object. It can also be concluded that an attack to the chest would be ideal for maximizing impact force and moving an opponent off balance. Key PointsIt has been determined that the palm strike is more effective than the punch for developing force and for transferring momentum, most likely the result of a reduced number of rigid links and joints.A strike at head level is less effective than a strike at chest level for developing force and transferring momentum.Distance plays an effect on the overall force and momentum changes, and most likely is dependent on the velocity of the limb and alignment of the bones prior to impact.The teaching of self defence for novices and law enforcement would benefit from including the palm strike as a high priority technique. PMID:24474886

  17. Ground/Flight Correlation of Aerodynamic Loads with Structural Response

    NASA Technical Reports Server (NTRS)

    Mangalam, Arun S.; Davis, Mark C.

    2009-01-01

    Ground and flight tests provide a basis and methodology for in-flight characterization of the aerodynamic and structural performance through the monitoring of the fluid-structure interaction. The NF-15B flight tests of the Intelligent Flight Control System program provided a unique opportunity to test the correlation of aerodynamic loads with points of flow attaching and detaching from the surface, which are also known as flow bifurcation points, as observed in a previous wind tunnel test performed at the U.S. Air Force Academy (Colorado Springs, Colorado). Moreover, flight tests, along with the subsequent unsteady aerodynamic tests in the NASA Transonic Dynamics Tunnel (TDT), provide a basis using surface flow sensors as means of assessing the aeroelastic performance of flight vehicles. For the flight tests, the NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. This data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in a structural response, which were then compared with the hot-film sensor signals. The hot-film sensor signals near the stagnation region were found to be highly correlated with the root-bending strains. For the TDT tests, a flexible wing section developed under the U.S. Air Force Research Lab SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at two span stations. The TDT tests confirmed the correlation between flow bifurcation points and the wing structural response to tunnel-generated gusts. Furthermore, as the wings structural modes were excited by the gusts, a gradual phase change between the flow bifurcation point and the structural mode occurred during a resonant condition.

  18. Validity of the Myotest® in measuring force and power production in the squat and bench press.

    PubMed

    Comstock, Brett A; Solomon-Hill, Glenn; Flanagan, Shawn D; Earp, Jacob E; Luk, Hui-Ying; Dobbins, Kathryn A; Dunn-Lewis, Courtenay; Fragala, Maren S; Ho, Jen-Yu; Hatfield, Disa L; Vingren, Jakob L; Denegar, Craig R; Volek, Jeff S; Kupchak, Brian R; Maresh, Carl M; Kraemer, William J

    2011-08-01

    The purpose of this study was to verify the concurrent validity of a bar-mounted Myotest® instrument in measuring the force and power production in the squat and bench press exercises when compared to the gold standard of a computerized linear transducer and force platform system. Fifty-four men (bench press: 39-171 kg; squat: 75-221 kg) and 43 women (bench press: 18-80 kg; squat: 30-115 kg) (age range 18-30 years) performed a 1 repetition maximum (1RM) strength test in bench press and squat exercises. Power testing consisted of the jump squat and the bench throw at 30% of each subject's 1RM. During each measurement, both the Myotest® instrument and the Celesco linear transducer of the directly interfaced BMS system (Ballistic Measurement System [BMS] Innervations Inc, Fitness Technology force plate, Skye, South Australia, Australia) were mounted to the weight bar. A strong, positive correlation (r) between the Myotest and BMS systems and a high correlation of determination (R2) was demonstrated for bench throw force (r = 0.95, p < 0.05) (R2 = 0.92); bench throw power (r = 0.96, p < 0.05) (R2 = 0.93); squat jump force (r = 0.98, p < 0.05) (R2 = 0.97); and squat jump power (r = 0.91, p < 0.05) (R2 = 0.82). In conclusion, when fixed on the bar in the vertical axis, the Myotest is a valid field instrument for measuring force and power in commonly used exercise movements.

  19. Aerodynamics, kinematics, and energetics of horizontal flapping flight in the long-eared bat Plecotus auritus.

    PubMed

    Norberg, U M

    1976-08-01

    The kinematics, aerodynamics, and energetics of Plecotus auritus in slow horizontal flight, 2-35 m s-1, are analysed. At this speed the inclination of the stroke path is ca. 58 degrees to the horizontal, the stroke angle ca. 91 degrees, and the stroke frequency ca. 11-9 Hz. A method, based on steady-state aerodynamic and momenthum theories, is derived to calculate the lift and drag coefficients as averaged over the whole wing the whole wing-stroke for horizontal flapping flight. This is a further development of Pennycuick's (1968) and Weis-Fogh's (1972) expressions for calculating the lift coefficient. The lift coefficient obtained varies between 1-4 and 1-6, the drag coefficient between 0-4 and 1-2, and the lift:drag ratio between 1-2 and 4-0. The corresponding, calculated, total specific mechanical power output of the wing muscles varies between 27-0 and 40-4 W kg-1 body mass. A maximum estimate of mechanical efficiency is 0-26. The aerodynamic efficiency varies between 0-07 and 0-10. The force coefficient, total mechanical power output, and mechanical and aerodynamic efficiencies are all plausible, demonstrating that the slow flapping flight of Plecotus is thus explicable by steady-state aerodynamics. The downstroke is the power stroke for the vertical upward forces and the upstroke for the horizontal forward forces.

  20. Flight Dynamics of an Aeroshell Using an Attached Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.; Schoenenberger, Mark; Axdahl, Erik; Wilhite, Alan

    2009-01-01

    An aeroelastic analysis of the behavior of an entry vehicle utilizing an attached inflatable aerodynamic decelerator during supersonic flight is presented. The analysis consists of a planar, four degree of freedom simulation. The aeroshell and the IAD are assumed to be separate, rigid bodies connected with a spring-damper at an interface point constraining the relative motion of the two bodies. Aerodynamic forces and moments are modeled using modified Newtonian aerodynamics. The analysis includes the contribution of static aerodynamic forces and moments as well as pitch damping. Two cases are considered in the analysis: constant velocity flight and planar free flight. For the constant velocity and free flight cases with neutral pitch damping, configurations with highly-stiff interfaces exhibit statically stable but dynamically unstable aeroshell angle of attack. Moderately stiff interfaces exhibit static and dynamic stability of aeroshell angle of attack due to damping induced by the pitch angle rate lag between the aeroshell and IAD. For the free-flight case, low values of both the interface stiffness and damping cause divergence of the aeroshell angle of attack due to the offset of the IAD drag force with respect to the aeroshell center of mass. The presence of dynamic aerodynamic moments was found to influence the stability characteristics of the vehicle. The effect of gravity on the aeroshell angle of attack stability characteristics was determined to be negligible for the cases investigated.

  1. Multiprocessing on supercomputers for computational aerodynamics

    NASA Technical Reports Server (NTRS)

    Yarrow, Maurice; Mehta, Unmeel B.

    1991-01-01

    Little use is made of multiple processors available on current supercomputers (computers with a theoretical peak performance capability equal to 100 MFLOPS or more) to improve turnaround time in computational aerodynamics. The productivity of a computer user is directly related to this turnaround time. In a time-sharing environment, such improvement in this speed is achieved when multiple processors are used efficiently to execute an algorithm. The concept of multiple instructions and multiple data (MIMD) is applied through multitasking via a strategy that requires relatively minor modifications to an existing code for a single processor. This approach maps the available memory to multiple processors, exploiting the C-Fortran-Unix interface. The existing code is mapped without the need for developing a new algorithm. The procedure for building a code utilizing this approach is automated with the Unix stream editor.

  2. Multiprocessing on supercomputers for computational aerodynamics

    SciTech Connect

    Mehta, V.B.; Yarrow, M. )

    1991-01-01

    Little use is made of multiple processors available on current supercomputers (computers with a theoretical peak performance capability equal to 100 MFLOPS or more) to improve turnaround time in computational aerodynamics. The productivity of a computer user is directly related to this turnaround time. In a time-sharing environment, such improvement is this speed achieved when multiple processors are used efficiently to execute an algorithm. The authors of this paper apply the concept of multiple instructions and multiple data (MIMD) through multitasking via a strategy that requires relatively minor modifications to an existing code for a single processor. This approach maps the available memory to multiple processors, exploiting the C-Fortran-Unix interface. The existing code is mapped without the need for developing a new algorithm. The procedure for building a code utilizing this approach is automated with the Unix stream editor.

  3. Aerodynamic characteristics of the Fiat UNO car

    SciTech Connect

    Costelli, A.F.

    1984-01-01

    The purpose of this article is to describe the work conducted in the aerodynamic field throughout the 4-year development and engineering time span required by the project of the UNO car. A description is given of all the parametric studies carried out. Through these studies two types of cars at present in production were defined and the characteristics of a possible future sports version laid down. A movable device, to be fitted in the back window, was also set up and patented. When actuated it reduces soiling of back window. A description is also provided of the measurements made in the car flow field and some considerations are outlined about the method applied. This method is still in development phase but it already permits some considerations and in-depth investigations to be made on the vehicle wake.

  4. Micro air vehicle motion tracking and aerodynamic modeling

    NASA Astrophysics Data System (ADS)

    Uhlig, Daniel V.

    Aerodynamic performance of small-scale fixed-wing flight is not well understood, and flight data are needed to gain a better understanding of the aerodynamics of micro air vehicles (MAVs) flying at Reynolds numbers between 10,000 and 30,000. Experimental studies have shown the aerodynamic effects of low Reynolds number flow on wings and airfoils, but the amount of work that has been conducted is not extensive and mostly limited to tests in wind and water tunnels. In addition to wind and water tunnel testing, flight characteristics of aircraft can be gathered through flight testing. The small size and low weight of MAVs prevent the use of conventional on-board instrumentation systems, but motion tracking systems that use off-board triangulation can capture flight trajectories (position and attitude) of MAVs with minimal onboard instrumentation. Because captured motion trajectories include minute noise that depends on the aircraft size, the trajectory results were verified in this work using repeatability tests. From the captured glide trajectories, the aerodynamic characteristics of five unpowered aircraft were determined. Test results for the five MAVs showed the forces and moments acting on the aircraft throughout the test flights. In addition, the airspeed, angle of attack, and sideslip angle were also determined from the trajectories. Results for low angles of attack (less than approximately 20 deg) showed the lift, drag, and moment coefficients during nominal gliding flight. For the lift curve, the results showed a linear curve until stall that was generally less than finite wing predictions. The drag curve was well described by a polar. The moment coefficients during the gliding flights were used to determine longitudinal and lateral stability derivatives. The neutral point, weather-vane stability and the dihedral effect showed some variation with different trim speeds (different angles of attack). In the gliding flights, the aerodynamic characteristics

  5. A comparison of baseline aerodynamic performance of optimally-twisted versus non-twisted HAWT blades

    SciTech Connect

    Simms, D A; Robinson, M C; Hand, M M; Fingersh, L J

    1995-01-01

    NREL has completed the initial twisted blade field tests of the ``Unsteady Aerodynamics Experiment.`` This test series continues systematic measurements of unsteady aerodynamic phenomena prevalent in stall-controlled horizontal axis wind turbines (HAWTs). The blade twist distribution optimizes power production at a single angle of attack along the span. Abrupt transitions into and out of stall are created due to rapid changes in inflow. Data from earlier experiments have been analyzed extensively to characterize the steady and unsteady response of untwisted blades. In this report, a characterization and comparison of the baseline aerodynamic performance of the twisted versus non-twisted blade sets will be presented for steady flow conditions.

  6. Computational Aerodynamic Simulations of a Spacecraft Cabin Ventilation Fan Design

    NASA Technical Reports Server (NTRS)

    Tweedt, Daniel L.

    2010-01-01

    Quieter working environments for astronauts are needed if future long-duration space exploration missions are to be safe and productive. Ventilation and payload cooling fans are known to be dominant sources of noise, with the International Space Station being a good case in point. To address this issue cost effectively, early attention to fan design, selection, and installation has been recommended, leading to an effort by NASA to examine the potential for small-fan noise reduction by improving fan aerodynamic design. As a preliminary part of that effort, the aerodynamics of a cabin ventilation fan designed by Hamilton Sundstrand has been simulated using computational fluid dynamics codes, and the computed solutions analyzed to quantify various aspects of the fan aerodynamics and performance. Four simulations were performed at the design rotational speed: two at the design flow rate and two at off-design flow rates. Following a brief discussion of the computational codes, various aerodynamic- and performance-related quantities derived from the computed flow fields are presented along with relevant flow field details. The results show that the computed fan performance is in generally good agreement with stated design goals.

  7. A New Aerodynamic Data Dispersion Method for Launch Vehicle Design

    NASA Technical Reports Server (NTRS)

    Pinier, Jeremy T.

    2011-01-01

    A novel method for implementing aerodynamic data dispersion analysis is herein introduced. A general mathematical approach combined with physical modeling tailored to the aerodynamic quantity of interest enables the generation of more realistically relevant dispersed data and, in turn, more reasonable flight simulation results. The method simultaneously allows for the aerodynamic quantities and their derivatives to be dispersed given a set of non-arbitrary constraints, which stresses the controls model in more ways than with the traditional bias up or down of the nominal data within the uncertainty bounds. The adoption and implementation of this new method within the NASA Ares I Crew Launch Vehicle Project has resulted in significant increases in predicted roll control authority, and lowered the induced risks for flight test operations. One direct impact on launch vehicles is a reduced size for auxiliary control systems, and the possibility of an increased payload. This technique has the potential of being applied to problems in multiple areas where nominal data together with uncertainties are used to produce simulations using Monte Carlo type random sampling methods. It is recommended that a tailored physics-based dispersion model be delivered with any aerodynamic product that includes nominal data and uncertainties, in order to make flight simulations more realistic and allow for leaner spacecraft designs.

  8. HIAD-2 (Hypersonic Inflatable Aerodynamic Decelerator)

    NASA Video Gallery

    The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project is a disruptive technology that will accommodate the atmospheric entry of heavy payloads to planetary bodies such as Mars. HIAD over...

  9. Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

    PubMed Central

    Py, G; Ramonatxo, C; Sirvent, P; Sanchez, A M J; Philippe, A G; Douillard, A; Galbès, O; Lionne, C; Bonnieu, A; Chopard, A; Cazorla, O; Lacampagne, A; Candau, R B

    2015-01-01

    Clenbuterol is a β2-adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a slow-to-fast phenotypic shift. The aim of the present study was to test the effects of chronic clenbuterol treatment on contractile efficiency and explore the underlying mechanisms, i.e. the muscle contractile machinery and calcium-handling ability. Forty-three 6-week-old male Wistar rats were randomly allocated to one of six groups that were treated with either subcutaneous equimolar doses of clenbuterol (4 mg kg−1 day−1) or saline solution for 9, 14 or 21 days. In addition to the muscle hypertrophy, although an 89% increase in absolute maximal tetanic force (Po) was noted, specific maximal tetanic force (sPo) was unchanged or even depressed in the slow twitch muscle of the clenbuterol-treated rats (P < 0.05). The fit of muscle contraction and relaxation force kinetics indicated that clenbuterol treatment significantly reduced the rate constant of force development and the slow and fast rate constants of relaxation in extensor digitorum longus muscle (P < 0.05), and only the fast rate constant of relaxation in soleus muscle (P < 0.05). Myofibrillar ATPase activity increased in both relaxed and activated conditions in soleus (P < 0.001), suggesting that the depressed specific tension was not due to the myosin head alteration itself. Moreover, action potential-elicited Ca2+ transients in flexor digitorum brevis fibres (fast twitch fibres) from clenbuterol-treated animals demonstrated decreased amplitude after 14 days (−19%, P < 0.01) and 21 days (−25%, P < 0.01). In conclusion, we showed that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca2+ release during contraction could partially explain these deleterious effects. PMID:25656230

  10. Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery.

    PubMed

    Py, G; Ramonatxo, C; Sirvent, P; Sanchez, A M J; Philippe, A G; Douillard, A; Galbès, O; Lionne, C; Bonnieu, A; Chopard, A; Cazorla, O; Lacampagne, A; Candau, R B

    2015-04-15

    Clenbuterol is a β2 -adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a slow-to-fast phenotypic shift. The aim of the present study was to test the effects of chronic clenbuterol treatment on contractile efficiency and explore the underlying mechanisms, i.e. the muscle contractile machinery and calcium-handling ability. Forty-three 6-week-old male Wistar rats were randomly allocated to one of six groups that were treated with either subcutaneous equimolar doses of clenbuterol (4 mg kg(-1) day(-1) ) or saline solution for 9, 14 or 21 days. In addition to the muscle hypertrophy, although an 89% increase in absolute maximal tetanic force (Po ) was noted, specific maximal tetanic force (sPo) was unchanged or even depressed in the slow twitch muscle of the clenbuterol-treated rats (P < 0.05). The fit of muscle contraction and relaxation force kinetics indicated that clenbuterol treatment significantly reduced the rate constant of force development and the slow and fast rate constants of relaxation in extensor digitorum longus muscle (P < 0.05), and only the fast rate constant of relaxation in soleus muscle (P < 0.05). Myofibrillar ATPase activity increased in both relaxed and activated conditions in soleus (P < 0.001), suggesting that the depressed specific tension was not due to the myosin head alteration itself. Moreover, action potential-elicited Ca(2+) transients in flexor digitorum brevis fibres (fast twitch fibres) from clenbuterol-treated animals demonstrated decreased amplitude after 14 days (-19%, P < 0.01) and 21 days (-25%, P < 0.01). In conclusion, we showed that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca(2+) release during contraction could partially explain these deleterious effects. PMID:25656230

  11. Lift vs. drag based mechanisms for vertical force production in the smallest flying insects.

    PubMed

    Jones, S K; Laurenza, R; Hedrick, T L; Griffith, B E; Miller, L A

    2015-11-01

    We used computational fluid dynamics to determine whether lift- or drag-based mechanisms generate the most vertical force in the flight of the smallest insects. These insects fly at Re on the order of 4-60 where viscous effects are significant. Detailed quantitative data on the wing kinematics of the smallest insects is not available, and as a result both drag- and lift-based strategies have been suggested as the mechanisms by which these insects stay aloft. We used the immersed boundary method to solve the fully-coupled fluid-structure interaction problem of a flexible wing immersed in a two-dimensional viscous fluid to compare three idealized hovering kinematics: a drag-based stroke in the vertical plane, a lift-based stroke in the horizontal plane, and a hybrid stroke on a tilted plane. Our results suggest that at higher Re, a lift-based strategy produces more vertical force than a drag-based strategy. At the Re pertinent to small insect hovering, however, there is little difference in performance between the two strategies. A drag-based mechanism of flight could produce more vertical force than a lift-based mechanism for insects at Re<5; however, we are unaware of active fliers at this scale.

  12. Load-induced enhancement of Dynein force production by LIS1-NudE in vivo and in vitro.

    PubMed

    Reddy, Babu J N; Mattson, Michelle; Wynne, Caitlin L; Vadpey, Omid; Durra, Abdo; Chapman, Dail; Vallee, Richard B; Gross, Steven P

    2016-01-01

    Most sub-cellular cargos are transported along microtubules by kinesin and dynein molecular motors, but how transport is regulated is not well understood. It is unknown whether local control is possible, for example, by changes in specific cargo-associated motor behaviour to react to impediments. Here we discover that microtubule-associated lipid droplets (LDs) in COS1 cells respond to an optical trap with a remarkable enhancement in sustained force production. This effect is observed only for microtubule minus-end-moving LDs. It is specifically blocked by RNAi for the cytoplasmic dynein regulators LIS1 and NudE/L (Nde1/Ndel1), but not for the dynactin p150(Glued) subunit. It can be completely replicated using cell-free preparations of purified LDs, where duration of LD force production is more than doubled. These results identify a novel, intrinsic, cargo-associated mechanism for dynein-mediated force adaptation, which should markedly improve the ability of motor-driven cargoes to overcome subcellular obstacles. PMID:27489054

  13. Load-induced enhancement of Dynein force production by LIS1–NudE in vivo and in vitro

    PubMed Central

    Reddy, Babu J. N.; Mattson, Michelle; Wynne, Caitlin L.; Vadpey, Omid; Durra, Abdo; Chapman, Dail; Vallee, Richard B.; Gross, Steven P.

    2016-01-01

    Most sub-cellular cargos are transported along microtubules by kinesin and dynein molecular motors, but how transport is regulated is not well understood. It is unknown whether local control is possible, for example, by changes in specific cargo-associated motor behaviour to react to impediments. Here we discover that microtubule-associated lipid droplets (LDs) in COS1 cells respond to an optical trap with a remarkable enhancement in sustained force production. This effect is observed only for microtubule minus-end-moving LDs. It is specifically blocked by RNAi for the cytoplasmic dynein regulators LIS1 and NudE/L (Nde1/Ndel1), but not for the dynactin p150Glued subunit. It can be completely replicated using cell-free preparations of purified LDs, where duration of LD force production is more than doubled. These results identify a novel, intrinsic, cargo-associated mechanism for dynein-mediated force adaptation, which should markedly improve the ability of motor-driven cargoes to overcome subcellular obstacles. PMID:27489054

  14. Recovery patterns in electroencephalographic global field power during maximal isometric force production.

    PubMed

    Dunn-Lewis, Courtenay; Flanagan, Shawn D; Comstock, Brett A; Maresh, Carl M; Volek, Jeff S; Denegar, Craig R; Kupchak, Brian R; Kraemer, William J

    2011-10-01

    In previous work, cortical activity decreased with fatigue following novel movements or small muscle group actions. These muscle actions, however, do not appear related to the cortical activity seen with biologically relevant and highly trained movement patterns (i.e., ingrained patterns). The cortical recovery response to ingrained patterns-and how it differs with altered load, speed, or volume - is unknown. The purpose of this balanced, within-group study was to investigate differences in cortical activity 24 hours after physically distinct variations of a highly trained squat exercise (n = 7, minimum 4 years resistance training experience). Four resistance protocols were chosen: rate of force development (PWR, 6 × 3 squat jumps at 30% of 1 repetition maximum [1RM]); magnitude of force development (FOR, 6 × 3 squat at 95% of 1RM); volume of force development (VOL, 6 × 10 squat at 80% of their 1RM); and control (CTRL, 6 sets unracking an empty bar). Twenty-four hours later, subjects performed a peak isometric squat while electroencephalographic and biochemical markers of exertion and fatigue were obtained. Global field power detected the quantity of activity superficial to motor regions. Waveforms of activity throughout the isometric squats were obtained and grand averages calculated to produce quantitative depictions of cortical activity. Significance was P ≤ 0.05. Peak isometric squat force was not statistically different 24 hours postexercise (Force [N]: PWR: 2828.79 ± 461.17; FOR: 2887.64 ± 453.09; VOL: 2910.17 ± 625.81; CTRL 2768.53 ± 374.85). Subjects produced similar and characteristic cortical activity patterns during isometric squats despite varying indices of fatigue. Differences were observed based upon the use or nonuse of aerobic endurance exercise in their training program. Patterns of activity in data seem to have emerged based on differences in training preference. Global Field Power (uV) during the isometric squat for PWR was 26.98 ± 14

  15. Space Shuttle flutter as affected by wing-body aerodynamic interaction

    NASA Technical Reports Server (NTRS)

    Chipman, R. R.; Rauch, F. J.; Shyprykevich, P.; Hess, R. W.

    1974-01-01

    In the NASA Langley Research Center 26-inch transonic blowdown wind-tunnel, flutter speeds were measured on 1/80-th scale semispan models of the orbiter wing, the complete Space Shuttle, and intermediate component combinations. Using the doublet lattice method combined with slender body theory to calculate unsteady aerodynamic forces, subsonic flutter speeds were computed for comparison. Aerodynamic interaction was found by test and analysis to raise the flutter speed in some configurations while lowering it in others. Although at Mach number less than 0.7, predicted speeds correlated to within 6% of those measured, rapid deterioration of the agreement occurred at higher subsonic Mach numbers, especially on the more complicated configurations. Additional analysis showed that aerodynamic forces arising from body flexibility potentially can have a large effect on flutter speed, but that the current shuttle design is not so affected.

  16. First-order aerodynamic and aeroelastic behavior of a single-blade installation setup

    NASA Astrophysics Data System (ADS)

    Gaunaa, M.; Bergami, L.; Guntur, S.; Zahle, F.

    2014-06-01

    Limitations on the wind speed at which blade installation can be performed bears important financial consequences. The installation cost of a wind farm could be significantly reduced by increasing the wind speed at which blade mounting operations can be carried out. This work characterizes the first-order aerodynamic and aeroelastic behavior of a single blade installation system, where the blade is grabbed by a yoke, which is lifted by the crane and stabilized by two taglines. A simple engineering model is formulated to describe the aerodynamic forcing on the blade subject to turbulent wind of arbitrary direction. The model is coupled with a schematic aeroelastic representation of the taglines system, which returns the minimum line tension required to compensate for the aerodynamic forcing. The simplified models are in excellent agreement with the aeroelastic code HAWC2, and provide a solid basis for future design of an upgraded single blade installation system able to operate at higher wind speeds.

  17. Effects of contraction path and velocity on the coordination of hand muscles during a three-digit force production task.

    PubMed

    Jiayuan He; Xinjun Sheng; Dingguo Zhang; Xiangyang Zhu

    2014-01-01

    Though many studies indicated that the behavior of single muscle was different between contraction and relaxation, the effect of contraction history profile on multiple muscles has not been investigated. In this study, we analyzed the influence of contraction history on the coordination patterns of hand muscles during a three-digit force production task. The effects of the contraction and relaxation paths with two contraction velocities (5% and 10% maximum voluntary contraction per second) were investigated. The results showed that the force-independent characteristic of muscle coordination patterns still held regardless of the contraction history profiles. In addition, the effect of contraction path was more significant than that of velocity. The study provides a potential way to overcome the impact of contraction disturbance for improving the robustness of the human-machine interface (HMI) based on electromyographic (EMG) pattern recognition.

  18. Study of Falling Roof Vibrations in a Production Face at Roof Support Resistance in the Form of Concentrated Force

    NASA Astrophysics Data System (ADS)

    Buyalich, G. D.; Buyalich, K. G.; Umrikhina, V. Yu

    2016-08-01

    One of the main reasons of roof support failures in production faces is mismatch of their parameters and parameters of dynamic impact on the metal structure from the falling roof during its secondary convergences. To assess the parameters of vibrational interaction of roof support with the roof, it was suggested to use computational models of forces application and a partial differential equation of fourth order describing this process, its numerical solution allowed to assess frequency, amplitude and speed of roof strata movement depending on physical and mechanical properties of the roof strata as well as on load bearing and geometry parameters of the roof support. To simplify solving of the differential equation, roof support response was taken as the concentrated force.

  19. Progress in computational unsteady aerodynamics

    NASA Technical Reports Server (NTRS)

    Obayashi, Shigeru

    1993-01-01

    After vigorous development for over twenty years, Computational Fluid Dynamics (CFD) in the field of aerospace engineering has arrived at a turning point toward maturity. This paper discusses issues related to algorithm development for the Euler/Navier Stokes equations, code validation and recent applications of CFD for unsteady aerodynamics. Algorithm development is a fundamental element for a good CFD program. Code validation tries to bridge the reliability gap between CFD and experiment. Many of the recent applications also take a multidisciplinary approach, which is a future trend for CFD applications. As computers become more affordable, CFD is expected to be a better scientific and engineering tool.

  20. The basic aerodynamics of floatation

    SciTech Connect

    Davies, M.J.; Wood, D.H.

    1983-09-01

    The original derivation of the basic theory governing the aerodynamics of both hovercraft and modern floatation ovens, requires the validity of some extremely crude assumptions. However, the basic theory is surprisingly accurate. It is shown that this accuracy occurs because the final expression of the basic theory can be derived by approximating the full Navier-Stokes equations in a manner that clearly shows the limitations of the theory. These limitations are used in discussing the relatively small discrepancies between the theory and experiment, which may not be significant for practical purposes.

  1. Aerodynamics. [numerical simulation using supercomputers

    NASA Technical Reports Server (NTRS)

    Graves, Randolph A., Jr.

    1988-01-01

    A projection is made of likely improvements in the economics of commercial aircraft operation due to developments in aerodynamics in the next half-century. Notable among these improvements are active laminar flow control techniques' application to third-generation SSTs, in order to achieve an L/D value of about 20; this is comparable to current subsonic transports, and has the further consequence of reducing cabin noise. Wave-cancellation systems may also be used to eliminate sonic boom overpressures, and rapid-combustion systems may be able to eliminate all pollutants from jet exhausts other than CO2.

  2. Aerodynamics. [Numerical simulation using supercomputers

    SciTech Connect

    Graves, R.A. Jr.

    1988-01-01

    A projection is made of likely improvements in the economics of commercial aircraft operation due to developments in aerodynamics in the next half-century. Notable among these improvements are active laminar flow control techniques' application to third-generation SSTs, in order to achieve an L/D value of about 20; this is comparable to current subsonic transports, and has the further consequence of reducing cabin noise. Wave-cancellation systems may also be used to eliminate sonic boom overpressures, and rapid-combustion systems may be able to eliminate all pollutants from jet exhausts other than CO/sub 2/.

  3. Phosphorylation of a twitchin-related protein controls catch and calcium sensitivity of force production in invertebrate smooth muscle

    PubMed Central

    Siegman, Marion J.; Funabara, Daisuke; Kinoshita, Shigeharu; Watabe, Shugo; Hartshorne, David J.; Butler, Thomas M.

    1998-01-01

    “Catch” is a condition of prolonged, high-force maintenance at resting intracellular Ca2+ concentration ([Ca2+]) and very low energy usage, occurring in invertebrate smooth muscles, including the anterior byssus retractor muscle (ABRM) of Mytilus edulis. Relaxation from catch is rapid on serotonergic nerve stimulation in intact muscles and application of cAMP in permeabilized muscles. This release of catch occurs by protein kinase A-mediated phosphorylation of a high (≈600 kDa) molecular mass protein, the regulator of catch. Here, we identify the catch-regulating protein as a homologue of the mini-titin, twitchin, based on (i) a partial cDNA of the purified isolated protein showing 77% amino acid sequence identity to the kinase domain of Aplysia californica twitchin; (ii) a polyclonal antibody to a synthetic peptide in this sequence reacting with the phosphorylated catch-regulating protein band from permeabilized ABRM; and (iii) the similarity of the amino acid composition and molecular weight of the protein to twitchin. In permeabilized ABRM, at all but maximum [Ca2+], phosphorylation of twitchin results in a decreased calcium sensitivity of force production (half-maximum at 2.5 vs. 1.3 μM calcium). At a given submaximal force, with equal numbers of force generators, twitchin phosphorylation increased unloaded shortening velocity ≈2-fold. These data suggest that aspects of the catch state exist not only at resting [Ca2+], but also at higher submaximal [Ca2+]. The mechanism that gives rise to force maintenance in catch probably operates together, to some extent, with that of cycling myosin crossbridges. PMID:9560285

  4. Estimation of Aircraft Unsteady Aerodynamic Parameters from Dynamic Wind Tunnel Testing

    NASA Technical Reports Server (NTRS)

    Murphy, Patrick C.; Klein, Vladislav

    2001-01-01

    Improved aerodynamic mathematical models, for use in aircraft simulation or flight control design, are required when representing nonlinear unsteady aerodynamics. A key limitation of conventional aerodynamic models is the inability to map frequency and amplitude dependent data into the equations of motion directly. In an effort to obtain a more general formulation of the aerodynamic model, researchers have been led to a parallel requirement for more general testing methods. Testing for a more comprehensive model can lead to a very time consuming number of tests especially if traditional single frequency harmonic testing is attempted. This paper presents an alternative to traditional single frequency forced-oscillation testing by utilizing Schroeder sweeps to efficiently obtain the frequency response of the unsteady aerodynamic model. Schroeder inputs provide signals with a flat power spectrum over a specified frequency band. For comparison, experimental results using the traditional single-frequency inputs are also considered. A method for data analysis to determine an adequate unsteady aerodynamic model is presented. Discussion of associated issues that arise during this type of analysis and comparison of results using traditional single frequency analysis are provided.

  5. STEP and STEPSPL: Computer programs for aerodynamic model structure determination and parameter estimation

    NASA Technical Reports Server (NTRS)

    Batterson, J. G.

    1986-01-01

    The successful parametric modeling of the aerodynamics for an airplane operating at high angles of attack or sideslip is performed in two phases. First the aerodynamic model structure must be determined and second the associated aerodynamic parameters (stability and control derivatives) must be estimated for that model. The purpose of this paper is to document two versions of a stepwise regression computer program which were developed for the determination of airplane aerodynamic model structure and to provide two examples of their use on computer generated data. References are provided for the application of the programs to real flight data. The two computer programs that are the subject of this report, STEP and STEPSPL, are written in FORTRAN IV (ANSI l966) compatible with a CDC FTN4 compiler. Both programs are adaptations of a standard forward stepwise regression algorithm. The purpose of the adaptation is to facilitate the selection of a adequate mathematical model of the aerodynamic force and moment coefficients of an airplane from flight test data. The major difference between STEP and STEPSPL is in the basis for the model. The basis for the model in STEP is the standard polynomial Taylor's series expansion of the aerodynamic function about some steady-state trim condition. Program STEPSPL utilizes a set of spline basis functions.

  6. Unsteady aerodynamics and flow control for flapping wing flyers

    NASA Astrophysics Data System (ADS)

    Ho, Steven; Nassef, Hany; Pornsinsirirak, Nick; Tai, Yu-Chong; Ho, Chih-Ming

    2003-11-01

    The creation of micro air vehicles (MAVs) of the same general sizes and weight as natural fliers has spawned renewed interest in flapping wing flight. With a wingspan of approximately 15 cm and a flight speed of a few meters per second, MAVs experience the same low Reynolds number (10 4-10 5) flight conditions as their biological counterparts. In this flow regime, rigid fixed wings drop dramatically in aerodynamic performance while flexible flapping wings gain efficacy and are the preferred propulsion method for small natural fliers. Researchers have long realized that steady-state aerodynamics does not properly capture the physical phenomena or forces present in flapping flight at this scale. Hence, unsteady flow mechanisms must dominate this regime. Furthermore, due to the low flight speeds, any disturbance such as gusts or wind will dramatically change the aerodynamic conditions around the MAV. In response, a suitable feedback control system and actuation technology must be developed so that the wing can maintain its aerodynamic efficiency in this extremely dynamic situation; one where the unsteady separated flow field and wing structure are tightly coupled and interact nonlinearly. For instance, birds and bats control their flexible wings with muscle tissue to successfully deal with rapid changes in the flow environment. Drawing from their example, perhaps MAVs can use lightweight actuators in conjunction with adaptive feedback control to shape the wing and achieve active flow control. This article first reviews the scaling laws and unsteady flow regime constraining both biological and man-made fliers. Then a summary of vortex dominated unsteady aerodynamics follows. Next, aeroelastic coupling and its effect on lift and thrust are discussed. Afterwards, flow control strategies found in nature and devised by man to deal with separated flows are examined. Recent work is also presented in using microelectromechanical systems (MEMS) actuators and angular speed

  7. Blunt Body Aerodynamics for Hypersonic Low Density Flows

    NASA Technical Reports Server (NTRS)

    Moss, James N.; Glass, Christopher E.; Greene, Francis A.

    2006-01-01

    Numerical simulations are performed for the Apollo capsule from the hypersonic rarefied to the continuum regimes. The focus is on flow conditions similar to those experienced by the Apollo 6 Command Module during the high altitude portion of its reentry. The present focus is to highlight some of the current activities that serve as a precursor for computational tool assessments that will be used to support the development of aerodynamic data bases for future capsule flight environments, particularly those for the Crew Exploration Vehicle (CEV). Results for aerodynamic forces and moments are presented that demonstrate their sensitivity to rarefaction; that is, free molecular to continuum conditions. Also, aerodynamic data are presented that shows their sensitivity to a range of reentry velocities, encompassing conditions that include reentry from low Earth orbit, lunar return, and Mars return velocities (7.7 to 15 km/s). The rarefied results obtained with direct simulation Monte Carlo (DSMC) codes are anchored in the continuum regime with data from Navier-Stokes simulations.

  8. The NASA Ames Hypervelocity Free Flight Aerodynamic Facility: Experimental Simulation of the Atmospheric Break-Up of Meteors

    NASA Technical Reports Server (NTRS)

    Wilder, M. C.; Bogdanoff, D. W.

    2015-01-01

    The Hypervelocity Free Flight Aerodynamic Facility at NASA Ames Research Center provides a potential platform for the experimental simulation of meteor breakup at conditions that closely match full-scale entry condition for select parameters. The poster describes the entry environment simulation capabilities of the Hypervelocity Free Flight Aerodynamic Facility (HFFAF) at NASA Ames Research Center and provides example images of the fragmentation of a hypersonic projectile for which break-up was initiated by mechanical forces (impact with a thin polymer diaphragm).

  9. The Characteristics of Force Production of Kinesin-5 on MCF7 Microtubules

    NASA Astrophysics Data System (ADS)

    Shojania Feizabadi, Mitra

    Unlike neural mammalian microtubules with class II of beta tubulin as the major beta tubulin in their compositions, MCF7 microtubules composed of 0% class II beta tubulin isotype, 39.1% class I beta tubulin isotype, 2.5% class III beta tubulin isotype and 58.4% class IV beta tubulin isotype. Recent studies have revealed that function of some of motor proteins can be affected by the structural composition of microtubules. In this work, we will show how the function of mitotic kinesin (Kin-5) under external load changed when moving along bovine versus MCF7 microtubules. Along MCF7 microtubules, the detachment force was reduced and the force-velocity curve was different as compared to those related to bovine brain. We will also show that the elimination of the C-terminal tails made the transport almost similar to the two sets of microtubules. This suggests that the C-terminal tails of tubulin plays a regulatory role in Kinesin-5's function.

  10. Closed-Loop Aerodynamic Flow Control of a Maneuvering Airfoil

    NASA Astrophysics Data System (ADS)

    Brzozowski, Daniel P.; Culp, John R.; Glezer, Ari

    2011-11-01

    The unsteady interaction between trailing edge aerodynamic flow control and airfoil motion in pitch and plunge is investigated in wind tunnel experiments using a 2-DOF traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the surface using hybrid synthetic jet actuators. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and velocity measurements that are taken phase-locked to the commanded actuation waveform. The effect of the unsteady motion on the model-embedded flow control is assessed in unsteady several maneuvers. Circulation time history that is estimated from a PIV wake survey shows that the entire flow over the airfoil readjusts within about 1.5 TCONV, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.

  11. Dynamic stall and aerodynamic damping

    SciTech Connect

    Rasmussen, F.; Petersen, J.T.; Madsen, H.A.

    1999-08-01

    A dynamic stall model is used to analyze and reproduce open air blade section measurements as well as wind tunnel measurements. The dynamic stall model takes variations in both angle of attack and flow velocity into account. The paper gives a brief description of the dynamic stall model and presents results from analyses of dynamic stall measurements for a variety of experiments with different airfoils in wind tunnel and on operating rotors. The wind tunnel experiments comprises pitching as well as plunging motion of the airfoils. The dynamic stall model is applied for derivation of aerodynamic damping characteristics for cyclic motion of the airfoils in flapwise and edgewise direction combined with pitching. The investigation reveals that the airfoil dynamic stall characteristics depend on the airfoil shape, and the type of motion (pitch, plunge). The aerodynamic damping characteristics, and thus the sensitivity to stall induced vibrations, depend highly on the relative motion of the airfoil in flapwise and edgewise direction, and on a possibly coupled pitch variation, which is determined by the structural characteristics of the blade.

  12. Orion Crew Module Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Bibb, Karen L.; Brauckmann, Gregory J.; Rhode, Matthew N.; Owens, Bruce; Chan, David T.; Walker, Eric L.; Bell, James H.; Wilson, Thomas M.

    2011-01-01

    The Apollo-derived Orion Crew Exploration Vehicle (CEV), part of NASA s now-cancelled Constellation Program, has become the reference design for the new Multi-Purpose Crew Vehicle (MPCV). The MPCV will serve as the exploration vehicle for all near-term human space missions. A strategic wind-tunnel test program has been executed at numerous facilities throughout the country to support several phases of aerodynamic database development for the Orion spacecraft. This paper presents a summary of the experimental static aerodynamic data collected to-date for the Orion Crew Module (CM) capsule. The test program described herein involved personnel and resources from NASA Langley Research Center, NASA Ames Research Center, NASA Johnson Space Flight Center, Arnold Engineering and Development Center, Lockheed Martin Space Sciences, and Orbital Sciences. Data has been compiled from eight different wind tunnel tests in the CEV Aerosciences Program. Comparisons are made as appropriate to highlight effects of angle of attack, Mach number, Reynolds number, and model support system effects.

  13. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will design, build, and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604BOO02G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate the aerodynamic flight database for the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. Al these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  14. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database in the hypersonic regime, The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  15. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database i n the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  16. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database in the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  17. Treatment with a corticotrophin releasing factor 2 receptor agonist modulates skeletal muscle mass and force production in aged and chronically ill animals

    PubMed Central

    2011-01-01

    Background Muscle weakness is associated with a variety of chronic disorders such as emphysema (EMP) and congestive heart failure (CHF) as well as aging. Therapies to treat muscle weakness associated with chronic disease or aging are lacking. Corticotrophin releasing factor 2 receptor (CRF2R) agonists have been shown to maintain skeletal muscle mass and force production in a variety of acute conditions that lead to skeletal muscle wasting. Hypothesis We hypothesize that treating animals with a CRF2R agonist will maintain skeletal muscle mass and force production in animals with chronic disease and in aged animals. Methods We utilized animal models of aging, CHF and EMP to evaluate the potential of CRF2R agonist treatment to maintain skeletal muscle mass and force production in aged animals and animals with CHF and EMP. Results In aged rats, we demonstrate that treatment with a CRF2R agonist for up to 3 months results in greater extensor digitorum longus (EDL) force production, EDL mass, soleus mass and soleus force production compared to age matched untreated animals. In the hamster EMP model, we demonstrate that treatment with a CRF2R agonist for up to 5 months results in greater EDL force production in EMP hamsters when compared to vehicle treated EMP hamsters and greater EDL mass and force in normal hamsters when compared to vehicle treated normal hamsters. In the rat CHF model, we demonstrate that treatment with a CRF2R agonist for up to 3 months results in greater EDL and soleus muscle mass and force production in CHF rats and normal rats when compared to the corresponding vehicle treated animals. Conclusions These data demonstrate that the underlying physiological conditions associated with chronic diseases such as CHF and emphysema in addition to aging do not reduce the potential of CRF2R agonists to maintain skeletal muscle mass and force production. PMID:21235761

  18. Aerodynamic design on high-speed trains

    NASA Astrophysics Data System (ADS)

    Ding, San-San; Li, Qiang; Tian, Ai-Qin; Du, Jian; Liu, Jia-Li

    2016-04-01

    Compared with the traditional train, the operational speed of the high-speed train has largely improved, and the dynamic environment of the train has changed from one of mechanical domination to one of aerodynamic domination. The aerodynamic problem has become the key technological challenge of high-speed trains and significantly affects the economy, environment, safety, and comfort. In this paper, the relationships among the aerodynamic design principle, aerodynamic performance indexes, and design variables are first studied, and the research methods of train aerodynamics are proposed, including numerical simulation, a reduced-scale test, and a full-scale test. Technological schemes of train aerodynamics involve the optimization design of the streamlined head and the smooth design of the body surface. Optimization design of the streamlined head includes conception design, project design, numerical simulation, and a reduced-scale test. Smooth design of the body surface is mainly used for the key parts, such as electric-current collecting system, wheel truck compartment, and windshield. The aerodynamic design method established in this paper has been successfully applied to various high-speed trains (CRH380A, CRH380AM, CRH6, CRH2G, and the Standard electric multiple unit (EMU)) that have met expected design objectives. The research results can provide an effective guideline for the aerodynamic design of high-speed trains.

  19. A new technique for aerodynamic noise calculation

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.; Pope, D. S.

    1992-01-01

    A novel method for the numerical analysis of aerodynamic noise generation is presented. The method involves first solving for the time-dependent incompressible flow for the given geometry. This fully nonlinear method that is tailored to extract the relevant acoustic fluctuations seems to be an efficient approach to the numerical analysis of aerodynamic noise generation.

  20. Aerodynamic seal assemblies for turbo-machinery

    SciTech Connect

    Bidkar, Rahul Anil; Wolfe, Christopher; Fang, Biao

    2015-09-29

    The present application provides an aerodynamic seal assembly for use with a turbo-machine. The aerodynamic seal assembly may include a number of springs, a shoe connected to the springs, and a secondary seal positioned about the springs and the shoe.