NASA Technical Reports Server (NTRS)
Walsh, Joanne L.; Young, Katherine C.; Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.
1994-01-01
This paper describes an integrated aerodynamic, dynamic, and structural (IADS) optimization procedure for helicopter rotor blades. The procedure combines performance, dynamics, and structural analyses with a general purpose optimizer using multilevel decomposition techniques. At the upper level, the structure is defined in terms of local quantities (stiffnesses, mass, and average strains). At the lower level, the structure is defined in terms of local quantities (detailed dimensions of the blade structure and stresses). The IADS procedure provides an optimization technique that is compatible with industrial design practices in which the aerodynamic and dynamic design is performed at a global level and the structural design is carried out at a detailed level with considerable dialogue and compromise among the aerodynamic, dynamic, and structural groups. The IADS procedure is demonstrated for several cases.
NASA Technical Reports Server (NTRS)
Walsh, Joanne L.; Young, Katherine C.; Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.
1995-01-01
This paper describes an integrated aerodynamic/dynamic/structural (IADS) optimization procedure for helicopter rotor blades. The procedure combines performance, dynamics, and structural analyses with a general-purpose optimizer using multilevel decomposition techniques. At the upper level, the structure is defined in terms of global quantities (stiffness, mass, and average strains). At the lower level, the structure is defined in terms of local quantities (detailed dimensions of the blade structure and stresses). The IADS procedure provides an optimization technique that is compatible with industrial design practices in which the aerodynamic and dynamic designs are performed at a global level and the structural design is carried out at a detailed level with considerable dialog and compromise among the aerodynamic, dynamic, and structural groups. The IADS procedure is demonstrated for several examples.
Optimization of rotor blades for combined structural, dynamic, and aerodynamic properties
NASA Technical Reports Server (NTRS)
He, Cheng-Jian; Peters, David A.
1990-01-01
Optimal helicopter blade design with computer-based mathematical programming has received more and more attention in recent years. Most of the research has focused on optimum dynamic characteristics of rotor blades to reduce vehicle vibration. There is also work on optimization of aerodynamic performance and on composite structural design. This research has greatly increased our understanding of helicopter optimum design in each of these aspects. Helicopter design is an inherently multidisciplinary process involving strong interactions among various disciplines which can appropriately include aerodynamics; dynamics, both flight dynamics and structural dynamics; aeroelasticity: vibrations and stability; and even acoustics. Therefore, the helicopter design process must satisfy manifold requirements related to the aforementioned diverse disciplines. In our present work, we attempt to combine several of these important effects in a unified manner. First, we design a blade with optimum aerodynamic performance by proper layout of blade planform and spanwise twist. Second, the blade is designed to have natural frequencies that are placed away from integer multiples of the rotor speed for a good dynamic characteristics. Third, the structure is made as light as possible with sufficient rotational inertia to allow for autorotational landing, with safe stress margins and flight fatigue life at each cross-section, and with aeroelastical stability and low vibrations. Finally, a unified optimization refines the solution.
Integration of dynamic, aerodynamic, and structural optimization of helicopter rotor blades
NASA Technical Reports Server (NTRS)
Peters, David A.
1991-01-01
Summarized here is the first six years of research into the integration of structural, dynamic, and aerodynamic considerations in the design-optimization process for rotor blades. Specifically discussed here is the application of design optimization techniques for helicopter rotor blades. The reduction of vibratory shears and moments at the blade root, aeroelastic stability of the rotor, optimum airframe design, and an efficient procedure for calculating system sensitivities with respect to the design variables used are discussed.
Numerical simulations of interactions among aerodynamics, structural dynamics, and control systems
NASA Astrophysics Data System (ADS)
Preidikman, Sergio
A robust technique for performing numerical simulations of nonlinear unsteady aeroelastic behavior is developed. The technique is applied to long-span bridges and the wing of a modern business jet. The heart of the procedure is combining the aerodynamic and structural models. The aerodynamic model is a general unsteady vortex-lattice method. The structural model for the bridges is a rigid roadbed supported by linear and torsional springs. For the aircraft wing, the structural model is a cantilever beam with rigid masses attached at various positions along the span; it was generated with the NASTRAN program. The structure, flowing air, and control devices are considered to be the elements of a single dynamic system. All the governing equations are integrated simultaneously and interactively in the time domain; a predictor-corrector method was adapted to perform this integration. For long-span bridges, the simulation predicts the onset of flutter accurately, and the numerical results strongly suggest that an actively controlled wing attached below the roadbed can easily suppress the wind-excited oscillations. The governing equations for a proposed passive system were developed. The wing structure is modelled with finite elements. The deflections are expressed as an expansion in terms of the free-vibration modes. The time-dependent coefficients are the generalized coordinates of the entire dynamic system. The concept of virtual work was extended to develop a method to transfer the aerodynamic loads to the structural nodes. Depending on the speed of the aircraft, the numerical results show damped responses to initial disturbances (although there are no viscous terms in either the aerodynamic or structural model), merging of modal frequencies, the development of limit-cycle oscillations, and the occurrence of a supercritical Hopf bifurcation leading to motion on a torus.
NASA Technical Reports Server (NTRS)
Prasanth, Ravi K.; Klein, Vladislav; Murphy, Patrick C.; Mehra, Raman K.
2005-01-01
This paper describes model structures and parameter estimation algorithms suitable for the identification of unsteady aerodynamic models from input-output data. The model structures presented are state space models and include linear time-invariant (LTI) models and linear parameter-varying (LPV) models. They cover a wide range of local and parameter dependent identification problems arising in unsteady aerodynamics and nonlinear flight dynamics. We present a residue algorithm for estimating model parameters from data. The algorithm can incorporate apriori information and is described in detail. The algorithms are evaluated on the F-16XL wind-tunnel test data from NAS Langley Research Center. Results of numerical evaluation are presented. The paper concludes with a discussion major issues and directions for future work.
Effect of Helicopter Blade Dynamics on Blade Aerodynamic and Structural Loads
NASA Technical Reports Server (NTRS)
Heffernan, Ruth M.
1987-01-01
The effect of rotor blade dynamics on aerodynamic and structural loads is examined for a conventional, main- rotor helicopter using both a comprehensive rotorcraft analysis (CAMRAD) and night test data. The impact of blade dynamics on blade section lift-coefficient time histories is studied by comparing predictions from both a rigid blade analysis and an elastic blade analysis with helicopter flight test data. The elastic blade analysis better predicts high-frequency behavior of section lift. In addition, components of the blade angle of attack, such as elastic blade twist, blade nap rate, blade slope velocity, and inflow, are examined as a function of blade mode. Elastic blade motion affects the blade angle of attack by a few tenths of a degree, and up to the sixth rotor harmonic. A similar study of the influence of blade dynamics on bending and torsion moments was also conducted. The modal analysis of the predicted blade structural loads suggested that five elastic bending deg of freedom (four flap and one lag) and three elastic torsion deg of freedom contributed to calculations of the blade structural loads. However, when structural bending load predictions from several elastic blade analyses were compared with flight test data, an elastic blade model consisting of only three elastic bending modes (first and second flap, and first lag), and two elastic torsion modes was found to be sufficient for maximum correlation.
NASA Technical Reports Server (NTRS)
Jones, William H.
1985-01-01
The Combined Aerodynamic and Structural Dynamic Problem Emulating Routines (CASPER) is a collection of data-base modification computer routines that can be used to simulate Navier-Stokes flow through realistic, time-varying internal flow fields. The Navier-Stokes equation used involves calculations in all three dimensions and retains all viscous terms. The only term neglected in the current implementation is gravitation. The solution approach is of an interative, time-marching nature. Calculations are based on Lagrangian aerodynamic elements (aeroelements). It is assumed that the relationships between a particular aeroelement and its five nearest neighbor aeroelements are sufficient to make a valid simulation of Navier-Stokes flow on a small scale and that the collection of all small-scale simulations makes a valid simulation of a large-scale flow. In keeping with these assumptions, it must be noted that CASPER produces an imitation or simulation of Navier-Stokes flow rather than a strict numerical solution of the Navier-Stokes equation. CASPER is written to operate under the Parallel, Asynchronous Executive (PAX), which is described in a separate report.
Effect of helicopter blade dynamics on blade aerodynamic and structural loads
NASA Technical Reports Server (NTRS)
Heffernan, Ruth M.
1987-01-01
The effect of rotor blade dynamics on aerodynamic and structural loads is examined for a conventional, main-rotor helicopter using a comprehensive rotorcraft analysis (CAMRAD) and flight-test data. The impact of blade dynamics on blade section lift-coefficient time histories is studied by comparing predictions from a rigid-blade analysis and an elastic-blade analysis with helicopter flight test data. The elastic blade analysis better predicts high-frequency behavior of section lift. In addition, components of the blade angle of attack such as elastic blade twist, blade flap rate, blade slope velocity, and inflow are examined as a function of blade mode. Elastic blade motion changed blade angle of attack by a few tenths of a degree, and up to the sixth rotor harmonic. A similar study of the influence of blade dynamics on bending and torsion moments was also conducted. A correlation study comparing predictions from several elastic-blade analyses with flight-test data revealed that an elastic-blade model consisting of only three elastic bending modes (first and second flap and first lag), and two elastic torsion modes was sufficient for good correlation.
Shipley, D.E.; Miller, M.S.; Robinson, M.C.; Luttges, M.W.; Simms, D.A.
1994-08-01
Aerodynamic data collected from the National Renewable Energy Laboratory`s Combined Experiment have shown three distinct performance regimes when the turbine is operated under relatively steady flow conditions. Operating at blade angles of attack below static stall, excellent agreement is achieved with two-dimensional wind tunnel data. Around the static stall angle, the cycle average normal force produced is greater than the static test data. Span locations near the hub produce extremely large values of normal force coefficient, well in excess of the two-dimensional data results. These performance regimes have been shown to be a function of the three-dimensional flow structure and cycle averaged dynamic stall effects. Power generation and root bending moments have also been shown to be directly dependent on the inflow wind velocity. Aerodynamic data, including episodes of dynamic stall, have been correlated on a cycle by cycle basis with the structural and power generation characteristics of a horizontal axis wind turbine. Instantaneous unsteady forces and resultant power generation indicate that peak transient levels can significantly exceed cycle averaged values. Strong coupling between transient aerodynamic and resonant response of the turbine was also observed. These results provide some initial insight into the contribution of unsteady aerodynamics on undesirable turbine structural response and fatigue life.
NASA Astrophysics Data System (ADS)
Shipley, D. E.; Miller, M. S.; Robinson, M. C.; Luttges, M. W.; Simms, D. A.
1994-08-01
Aerodynamic data collected from the National Renewable Energy Laboratory's Combined Experiment have shown three distinct performance regimes when the turbine is operated under relatively steady flow conditions. Operating at blade angles of attack below static stall, excellent agreement is achieved with two-dimensional wind tunnel data. Around the static stall angle, the cycle average normal force produced is greater than the static test data. Span locations near the hub produce extremely large values of normal force coefficient, well in excess of the two-dimensional data results. These performance regimes have been shown to be a function of the three-dimensional flow structure and cycle averaged dynamic stall effects. Power generation and root bending moments have also been shown to be directly dependent on the inflow wind velocity. Aerodynamic data, including episodes of dynamic stall, have been correlated on a cycle by cycle basis with the structural and power generation characteristics of a horizontal axis wind turbine. Instantaneous unsteady forces and resultant power generation indicate that peak transient levels can significantly exceed cycle averaged values. Strong coupling between transient aerodynamic and resonant response of the turbine was also observed. These results provide some initial insight into the contribution of unsteady aerodynamics on undesirable turbine structural response and fatigue life.
NASA Technical Reports Server (NTRS)
Thorp, Scott A.
1992-01-01
This presentation will discuss the development of a NASA Geometry Exchange Specification for transferring aerodynamic surface geometry between LeRC systems and grid generation software used for computational fluid dynamics research. The proposed specification is based on a subset of the Initial Graphics Exchange Specification (IGES). The presentation will include discussion of how the NASA-IGES standard will accommodate improved computer aided design inspection methods and reverse engineering techniques currently being developed. The presentation is in viewgraph format.
NASA Astrophysics Data System (ADS)
Cesnik, C. E. S.; Opoku, D. G.; Nitzsche, F.; Cheng, T.
2004-06-01
An active aeroelastic and aeroacoustic analysis of helicopter rotor systems is presented in this paper. It is a tightly coupled computational aeroelastic code that interfaces a particle-wake panel method code with an active nonlinear mixed variational intrinsic beam element code. In addition, a Ffowcs-Williams-Hawkings equation-based acoustic component is incorporated to complete the numerical implementation. The theory behind each component is summarized here as well as the method for coupling the aerodynamic and structural components. Sample acoustic and aeroelastic results are given for different model-scale rotors. Comparisons with available (passive) results show very good agreement. Preliminary study with an active twist rotor is also shown.
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.
Integrated Aerodynamic/Structural/Dynamic Analyses of Aircraft with Large Shape Changes
NASA Technical Reports Server (NTRS)
Samareh, Jamshid A.; Chwalowski, Pawel; Horta, Lucas G.; Piatak, David J.; McGowan, Anna-Maria R.
2007-01-01
The conceptual and preliminary design processes for aircraft with large shape changes are generally difficult and time-consuming, and the processes are often customized for a specific shape change concept to streamline the vehicle design effort. Accordingly, several existing reports show excellent results of assessing a particular shape change concept or perturbations of a concept. The goal of the current effort was to develop a multidisciplinary analysis tool and process that would enable an aircraft designer to assess several very different morphing concepts early in the design phase and yet obtain second-order performance results so that design decisions can be made with better confidence. The approach uses an efficient parametric model formulation that allows automatic model generation for systems undergoing radical shape changes as a function of aerodynamic parameters, geometry parameters, and shape change parameters. In contrast to other more self-contained approaches, the approach utilizes off-the-shelf analysis modules to reduce development time and to make it accessible to many users. Because the analysis is loosely coupled, discipline modules like a multibody code can be easily swapped for other modules with similar capabilities. One of the advantages of this loosely coupled system is the ability to use the medium-to high-fidelity tools early in the design stages when the information can significantly influence and improve overall vehicle design. Data transfer among the analysis modules are based on an accurate and automated general purpose data transfer tool. In general, setup time for the integrated system presented in this paper is 2-4 days for simple shape change concepts and 1-2 weeks for more mechanically complicated concepts. Some of the key elements briefly described in the paper include parametric model development, aerodynamic database generation, multibody analysis, and the required software modules as well as examples for a telescoping wing, a
Dynamic soaring: aerodynamics for albatrosses
NASA Astrophysics Data System (ADS)
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 equations provide an instructive and appealing example of fixed-wing aerodynamics suitable for undergraduate demonstration.
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…
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
Comparisons of several aerodynamic methods for application to dynamic loads analyses
NASA Technical Reports Server (NTRS)
Kroll, R. I.; Miller, R. D.
1976-01-01
The results of a study are presented in which the applicability at subsonic speeds of several aerodynamic methods for predicting dynamic gust loads on aircraft, including active control systems, was examined and compared. These aerodynamic methods varied from steady state to an advanced unsteady aerodynamic formulation. Brief descriptions of the structural and aerodynamic representations and of the motion and load equations are presented. Comparisons of numerical results achieved using the various aerodynamic methods are shown in detail. From these results, aerodynamic representations for dynamic gust analyses are identified. It was concluded that several aerodynamic methods are satisfactory for dynamic gust analyses of configurations having either controls fixed or active control systems that primarily affect the low frequency rigid body aircraft response.
Dynamic Stall in Pitching Airfoils: Aerodynamic Damping and Compressibility Effects
NASA Astrophysics Data System (ADS)
Corke, Thomas C.; Thomas, Flint O.
2015-01-01
Dynamic stall is an incredibly rich fluid dynamics problem that manifests itself on an airfoil during rapid, transient motion in which the angle of incidence surpasses the static stall limit. It is an important element of many manmade and natural flyers, including helicopters and supermaneuverable aircraft, and low-Reynolds number flapping-wing birds and insects. The fluid dynamic attributes that accompany dynamic stall include an eruption of vorticity that organizes into a well-defined dynamic stall vortex and massive excursions in aerodynamic loads that can couple with the airfoil structural dynamics. The dynamic stall process is highly sensitive to surface roughness that can influence turbulent transition and to local compressibility effects that occur at free-stream Mach numbers that are otherwise incompressible. Under some conditions, dynamic stall can result in negative aerodynamic damping that leads to limit-cycle growth of structural vibrations and rapid mechanical failure. The mechanisms leading to negative damping have been a principal interest of recent experiments and analysis. Computational fluid dynamic simulations and low-order models have not been good predictors so far. Large-eddy simulation could be a viable approach although it remains computationally intensive. The topic is technologically important owing to the desire to develop next-generation rotorcraft that employ adaptive rotor dynamic stall control.
Nonlinear problems in flight dynamics involving aerodynamic bifurcations
NASA Technical Reports Server (NTRS)
Tobak, M.; Chapman, G. T.
1985-01-01
Aerodynamic bifurcation is defined as the replacement of an unstable equilibrium flow by a new stable equilibrium flow at a critical value of a parameter. A mathematical model of the aerodynamic contribution to the aircraft's equations of motion is amended to accommodate aerodynamic bifurcations. Important bifurcations such as, the onset of large-scale vortex-shedding are defined. The amended mathematical model is capable of incorporating various forms of aerodynamic responses, including those associated with dynamic stall of airfoils.
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.
Estimation of Unsteady Aerodynamic Models from Dynamic Wind Tunnel Data
NASA Technical Reports Server (NTRS)
Murphy, Patrick; Klein, Vladislav
2011-01-01
Demanding aerodynamic modelling requirements for military and civilian aircraft have motivated researchers to improve computational and experimental techniques and to pursue closer collaboration in these areas. Model identification and validation techniques are key components for this research. This paper presents mathematical model structures and identification techniques that have been used successfully to model more general aerodynamic behaviours in single-degree-of-freedom dynamic testing. Model parameters, characterizing aerodynamic properties, are estimated using linear and nonlinear regression methods in both time and frequency domains. Steps in identification including model structure determination, parameter estimation, and model validation, are addressed in this paper with examples using data from one-degree-of-freedom dynamic wind tunnel and water tunnel experiments. These techniques offer a methodology for expanding the utility of computational methods in application to flight dynamics, stability, and control problems. Since flight test is not always an option for early model validation, time history comparisons are commonly made between computational and experimental results and model adequacy is inferred by corroborating results. An extension is offered to this conventional approach where more general model parameter estimates and their standard errors are compared.
Dynamic control of a bistable wing under aerodynamic loading
NASA Astrophysics Data System (ADS)
Bilgen, Onur; Arrieta, Andres F.; Friswell, Michael I.; Hagedorn, Peter
2013-02-01
The aerodynamic evaluation of a dynamic control technique applied to a bistable unsymmetrical cross-ply composite plate with surface bonded piezoelectric actuators is presented. The plate is clamped on one end to form a low-aspect-ratio wing. A previously proposed dynamic control method, utilizing bending resonance in different stable equilibrium positions, is used to induce snap-through between the two equilibrium states. Compared to quasi-static actuation, driving the bistable plate near resonance using surface bonded piezoelectric materials requires, theoretically, a lower peak excitation voltage to achieve snap-through. First, a set of extensive wind tunnel experiments are conducted on the passive bistable wing to understand the change in the dynamic behavior under various aerodynamic conditions. The passive wing demonstrated sufficient bending stiffness to sustain its shape under aerodynamic loading while preserving the desired bistable behavior. Next, by the use of the resonant control technique, the plate is turned into an effectively monostable structure, or alternatively, both stable equilibrium positions can be reached actively from the other stable equilibrium. Dynamic forward and reverse snap-through is demonstrated in the wind tunnel which shows both the effectiveness of the piezoelectric actuation as well as the load carrying capability of both states of the bistable wing.
Aerodynamics modeling of towed-cable dynamics
Kang, S.W.; Latorre, V.R.
1991-01-17
The dynamics of a cable/drogue system being towed by an orbiting aircraft has been investigated as a part of an LTWA project for the Naval Air Systems Command. We present here a status report on the tasks performed under Phase 1. We have accomplished the following tasks under Phase 1: A literature survey on the towed-cable motion problem has been conducted. While both static (steady-state) and dynamic (transient) analyses exist in the literature, no single, comprehensive analysis exists that directly addresses the present problem. However, the survey also reveals that, when judiciously applied, these past analyses can serve as useful building blocks for approaching the present problem. A numerical model that addresses several aspects of the towed-cable dynamic problem has been adapted from a Canadian underwater code for the present aerodynamic situation. This modified code, called TOWDYN, analyzes the effects of gravity, tension, aerodynamic drag, and wind. Preliminary results from this code demonstrate that the wind effects alone CAN generate the drogue oscillation behavior, i.e., the yo-yo'' phenomenon. This code also will serve as a benchmark code for checking the accuracy of a more general and complete R D'' model code. We have initiated efforts to develop a general R D model supercomputer code that also takes into account other physical factors, such as induced oscillations and bending stiffness. This general code will be able to evaluate the relative impacts of the various physical parameters, which may become important under certain conditions. This R D code will also enable development of a simpler operational code that can be used by the Naval Air personnel in the field.
Dynamic stability of an aerodynamically efficient motorcycle
NASA Astrophysics Data System (ADS)
Sharma, Amrit; Limebeer, David J. N.
2012-08-01
Motorcycles exhibit two potentially dangerous oscillatory modes known as 'wobble' and 'weave'. The former is reminiscent of supermarket castor shimmy, while the latter is a low frequency 'fish-tailing' motion that involves a combination of rolling, yawing, steering and side-slipping motions. These unwanted dynamic features, which can occur when two-wheeled vehicles are operated at speed, have been studied extensively. The aim of this paper is to use mathematical analysis to identify important stability trends in the on-going design of a novel aerodynamically efficient motorcycle known as the ECOSSE Spirit ES1. A mathematical model of the ES1 is developed using a multi-body dynamics software package called VehicleSim [Anon, VehicleSim Lisp Reference Manual Version 1.0, Mechanical Simulation Corporation, 2008. Available at http://www.carsim.com]. This high-fidelity motorcycle model includes realistic tyre-road contact geometry, a comprehensive tyre model, tyre relaxation and a flexible frame. A parameter set representative of a modern high-performance machine and rider is used. Local stability is investigated via the eigenvalues of the linearised models that are associated with equilibrium points of interest. A comprehensive study of the effects of frame flexibilities, acceleration, aerodynamics and tyre variations is presented, and an optimal passive steering compensator is derived. It is shown that the traditional steering damper cannot be used to stabilise the ES1 over its entire operating speed range. A simple passive compensator, involving an inerter is proposed. Flexibility can be introduced deliberately into various chassis components to change the stability characteristics of the vehicle; the implications of this idea are studied.
NASA Astrophysics Data System (ADS)
Strasser, Matthew N.
Structural loading produced by an impacting vortex is a hazardous phenomenon that is encountered in numerous applications ranging from the destruction of residences by tornados to the chopping of tip vortices by rotors. Adequate design of structures to resist vortex-induced structural loading necessitates study of the phenomenon that control the structural loading produced by an impacting vortex. This body of work extends the current knowledge base of vortex-structure interaction by evaluating the influence of the relative vortex-to-structure size on the structural loading that the vortex produces. A computer model is utilized to directly simulate the two-dimensional impact of an impinging vortex with a slender, cylindrical structure. The vortex's tangential velocity profile (TVP) is defined by a normalization of the Vatistas analytical (TVP) which realistically replicates the documented spectrum of measured vortex TVPs. The impinging vortex's maximum tangential velocity is fixed, and the vortex's critical radius is incremented from one to one-hundred times the structure's diameter. When the impinging vortex is small, it interacts with vortices produced on the structure by the free stream, and maximum force coefficient amplitudes vary by more than 400% when the impinging vortex impacts the structure at different times. Maximum drag and lift force coefficient amplitudes reach asymptotic values as the impinging vortex's size increases that are respectively 94.77% and 10.66% less than maximum force coefficients produced by an equivalent maximum velocity free stream. The vortex produces maximum structural loading when its path is shifted above the structure's centerline, and maximum drag and lift force coefficients are respectively up to 4.80% and 34.07% greater than maximum force coefficients produced by an equivalent-velocity free stream. Finally, the dynamic load factor (DLF) concept is used to develop a generalized methodology to assess the dynamic amplification of
Integrated structural-aerodynamic design optimization
NASA Technical Reports Server (NTRS)
Haftka, R. T.; Kao, P. J.; Grossman, B.; Polen, D.; Sobieszczanski-Sobieski, J.
1988-01-01
This paper focuses on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration, with emphasis on the major difficulty associated with multidisciplinary design optimization processes, their enormous computational costs. Methods are presented for reducing this computational burden through the development of efficient methods for cross-sensitivity calculations and the implementation of approximate optimization procedures. Utilizing a modular sensitivity analysis approach, it is shown that the sensitivities can be computed without the expensive calculation of the derivatives of the aerodynamic influence coefficient matrix, and the derivatives of the structural flexibility matrix. The same process is used to efficiently evaluate the sensitivities of the wing divergence constraint, which should be particularly useful, not only in problems of complete integrated aircraft design, but also in aeroelastic tailoring applications.
Integrated aerodynamic-structural-control wing design
NASA Technical Reports Server (NTRS)
Rais-Rohani, M.; Haftka, R. T.; Grossman, B.; Unger, E. R.
1992-01-01
The aerodynamic-structural-control design of a forward-swept composite wing for a high subsonic transport aircraft is considered. The structural analysis is based on a finite-element method. The aerodynamic calculations are based on a vortex-lattice method, and the control calculations are based on an output feedback control. The wing is designed for minimum weight subject to structural, performance/aerodynamic and control constraints. Efficient methods are used to calculate the control-deflection and control-effectiveness sensitivities which appear as second-order derivatives in the control constraint equations. To suppress the aeroelastic divergence of the forward-swept wing, and to reduce the gross weight of the design aircraft, two separate cases are studied: (1) combined application of aeroelastic tailoring and active controls; and (2) aeroelastic tailoring alone. The results of this study indicated that, for this particular example, aeroelastic tailoring is sufficient for suppressing the aeroelastic divergence, and the use of active controls was not necessary.
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.
Integrated aerodynamic/structural design of a sailplane wing
NASA Technical Reports Server (NTRS)
Grossman, B.; Gurdal, Z.; Haftka, R. T.; Strauch, G. J.; Eppard, W. M.
1986-01-01
Using lifting-line theory and beam analysis, the geometry (planiform and twist) and composite material structural sizes (skin thickness, spar cap, and web thickness) were designed for a sailplane wing, subject to both structural and aerodynamic constraints. For all elements, the integrated design (simultaneously designing the aerodynamics and the structure) was superior in terms of performance and weight to the sequential design (where the aerodynamic geometry is designed to maximize the performance, following which a structural/aeroelastic design minimizes the weight). Integrated designs produced less rigid, higher aspect ratio wings with favorable aerodynamic/structural interactions.
Computational fluid dynamics uses in fluid dynamics/aerodynamics education
NASA Technical Reports Server (NTRS)
Holst, Terry L.
1994-01-01
The field of computational fluid dynamics (CFD) has advanced to the point where it can now be used for the purpose of fluid dynamics physics education. Because of the tremendous wealth of information available from numerical simulation, certain fundamental concepts can be efficiently communicated using an interactive graphical interrogation of the appropriate numerical simulation data base. In other situations, a large amount of aerodynamic information can be communicated to the student by interactive use of simple CFD tools on a workstation or even in a personal computer environment. The emphasis in this presentation is to discuss ideas for how this process might be implemented. Specific examples, taken from previous publications, will be used to highlight the presentation.
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.
Influence of unsteady aerodynamics on driving dynamics of passenger cars
NASA Astrophysics Data System (ADS)
Huemer, Jakob; Stickel, Thomas; Sagan, Erich; Schwarz, Martin; Wall, Wolfgang A.
2014-11-01
Recent approaches towards numerical investigations with computational fluid dynamics methods on unsteady aerodynamic loads of passenger cars identified major differences compared with steady-state aerodynamic excitations. Furthermore, innovative vehicle concepts such as electric-vehicles or hybrid drives further challenge the basic layout of passenger cars. Therefore, the relevance of unsteady aerodynamic loads on cross-wind stability of changing basic vehicle architectures should be analysed. In order to assure and improve handling and ride characteristics at high velocity of the actual range of vehicle layouts, the influence of unsteady excitations on the vehicle response was investigated. For this purpose, a simulation of the vehicle dynamics through multi-body simulation was used. The impact of certain unsteady aerodynamic load characteristics on the vehicle response was quantified and key factors were identified. Through a series of driving simulator tests, the identified differences in the vehicle response were evaluated regarding their significance on the subjective driver perception of cross-wind stability. Relevant criteria for the subjective driver assessment of the vehicle response were identified. As a consequence, a design method for the basic layout of passenger cars and chassis towards unsteady aerodynamic excitations was defined.
A comprehensive analytical model of rotorcraft aerodynamics and dynamics. Part 3: Program manual
NASA Technical Reports Server (NTRS)
Johnson, W.
1980-01-01
The computer program for a comprehensive analytical model of rotorcraft aerodynamics and dynamics is described. This analysis is designed to calculate rotor performance, loads, and noise; the helicopter vibration and gust response; the flight dynamics and handling qualities; and the system aeroelastic stability. The analysis is a combination of structural, inertial, and aerodynamic models that is applicable to a wide range of problems and a wide class of vehicles. The analysis is intended for use in the design, testing, and evaluation of rotors and rotorcraft and to be a basis for further development of rotary wing theories.
NASA Technical Reports Server (NTRS)
Johnson, W.
1980-01-01
Structural, inertia, and aerodynamic models were combined to form a comprehensive model of rotor aerodynamics and dynamics that is applicable to a wide range of problems and a wide class of vehicles. A digital computer program is used to calculate rotor performance, loads, and noise; helicopter vibration and gust response; flight dynamics and handling qualities; and system aeroelastic stability. The analysis is intended for use in the design, testing, and evaluation of rotors and rotorcraft, and to be a basis for further development of rotary wing theories.
Ground/Flight Correlation of Aerodynamic Loads with Structural Response
NASA Technical Reports Server (NTRS)
Mangalam, Arun S.; Davis, Mark C.
2009-01-01
United States Air Force Research Laboratory (AFRL) ground tests at the NASA Transonic Dynamics Tunnel (TDT) and NASA flight tests provide a basis and methodology for in-flight characterization of the aeroelastic performance through the monitoring of the fluid-structure interaction using surface flow sensors. NASA NF-15B flight tests provided a unique opportunity to test the correlation of aerodynamic loads with sectional flow attachment/detachment points, also known as flow bifurcation points (FBPs), as observed in previous wind tunnel tests. The NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. These data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in root-bending strains and hot-film sensor signals near the stagnation region that were highly correlated. For the TDT tests, a flexible wing section developed under the AFRL SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at multiple span stations. The TDT tests provided data showing a gradual phase change between the FBP and the structural mode occurred during a resonant condition as the wings structural modes were excited by the tunnel-generated gusts.
Role of computational fluid dynamics in unsteady aerodynamics for aeroelasticity
NASA Technical Reports Server (NTRS)
Guruswamy, Guru P.; Goorjian, Peter M.
1989-01-01
In the last two decades there have been extensive developments in computational unsteady transonic aerodynamics. Such developments are essential since the transonic regime plays an important role in the design of modern aircraft. Therefore, there has been a large effort to develop computational tools with which to accurately perform flutter analysis at transonic speeds. In the area of Computational Fluid Dynamics (CFD), unsteady transonic aerodynamics are characterized by the feature of modeling the motion of shock waves over aerodynamic bodies, such as wings. This modeling requires the solution of nonlinear partial differential equations. Most advanced codes such as XTRAN3S use the transonic small perturbation equation. Currently, XTRAN3S is being used for generic research in unsteady aerodynamics and aeroelasticity of almost full aircraft configurations. Use of Euler/Navier Stokes equations for simple typical sections has just begun. A brief history of the development of CFD for aeroelastic applications is summarized. The development of unsteady transonic aerodynamics and aeroelasticity are also summarized.
Dynamic response of aircraft structure
NASA Technical Reports Server (NTRS)
1975-01-01
The physical and mathematical problems associated with the response of elastic structures to random excitations such as occurs during buffeting and other transonic phenomena were discussed. The following subjects were covered: (1) general dynamic system consisting of the aircraft structure, the aerodynamic driving forces due to separated flow, and the aerodynamic forces due to aircraft structural motion, (2) structural and aerodynamic quantities of the dynamic system with special emphasis given to the description of the aerodynamic forces, and including a treatment of similarity laws, scaling effects, and wind tunnel testing, and (3) methods for data processing of fluctuating pressure recordings and techniques for response analysis for random excitation. A general buffeting flutter model, which takes into account the interactions between the separated and motion induced flows was presented. Relaxations of this model leading to the forced vibration model were explained.
Missile autopilot design considering uncertainties in aerodynamics and actuator dynamics
NASA Astrophysics Data System (ADS)
Song, Yong D.; Hou, J.; Fogson, F.
2000-07-01
This work presents a method for missile autopilot design in the presence of actuator and uncertain dynamics. Nonlinear control algorithms are derived based on both missile aerodynamics and actuator dynamics. To account for system nonlinearities and uncertainties due to varying flight conditions, a memory-based compensation unit is developed and integrated into the strategy. Simulation on EMRAAT missile validates the effectiveness of the proposed control method.
Supersonic Parachute Aerodynamic Testing and Fluid Structure Interaction Simulation
NASA Astrophysics Data System (ADS)
Lingard, J. S.; Underwood, J. C.; Darley, M. G.; Marraffa, L.; Ferracina, L.
2014-06-01
The ESA Supersonic Parachute program expands the knowledge of parachute inflation and flying characteristics in supersonic flows using wind tunnel testing and fluid structure interaction to develop new inflation algorithms and aerodynamic databases.
Coupled flow, thermal and structural analysis of aerodynamically heated panels
NASA Technical Reports Server (NTRS)
Thornton, Earl A.; Dechaumphai, Pramote
1986-01-01
A finite element approach to coupling flow, thermal and structural analyses of aerodynamically heated panels is presented. The Navier-Stokes equations for laminar compressible flow are solved together with the energy equation and quasi-static structural equations of the panel. Interactions between the flow, panel heat transfer and deformations are studied for thin stainless steel panels aerodynamically heated by Mach 6.6 flow.
Structural evaluation of deployable aerodynamic spike booms
NASA Technical Reports Server (NTRS)
Richter, B. J.
1975-01-01
An extendable boom consisting of a series of telescopic cylindrical tube segments and overlapping lock joints developed for use as an aerodynamic spike mounted atop a missile is described. Two candidate design concepts differing mainly in the particular overlapping lock joint designs are undergoing a combined analytical/experimental evaluation. Some of the results of this evaluation are presented.
Improved Aerodynamic Influence Coefficients for Dynamic Aeroelastic Analyses
NASA Astrophysics Data System (ADS)
Gratton, Patrice
2011-12-01
Currently at Bombardier Aerospace, aeroelastic analyses are performed using the Doublet Lattice Method (DLM) incorporated in the NASTRAN solver. This method proves to be very reliable and fast in preliminary design stages where wind tunnel experimental results are often not available. Unfortunately, the geometric simplifications and limitations of the DLM, based on the lifting surfaces theory, reduce the ability of this method to give reliable results for all flow conditions, particularly in transonic flow. Therefore, a new method has been developed involving aerodynamic data from high-fidelity CFD codes which solve the Euler or Navier-Stokes equations. These new aerodynamic loads are transmitted to the NASTRAN aeroelastic module through improved aerodynamic influence coefficients (AIC). A cantilevered wing model is created from the Global Express structural model and a set of natural modes is calculated for a baseline configuration of the structure. The baseline mode shapes are then combined with an interpolation scheme to deform the 3-D CFD mesh necessary for Euler and Navier-Stokes analyses. An uncoupled approach is preferred to allow aerodynamic information from different CFD codes. Following the steady state CFD analyses, pressure differences ( DeltaCp), calculated between the deformed models and the original geometry, lead to aerodynamic loads which are transferred to the DLM model. A modal-based AIC method is applied to the aerodynamic matrices of NASTRAN based on a least-square approximation to evaluate aerodynamic loads of a different wing configuration which displays similar types of mode shapes. The methodology developed in this research creates weighting factors based on steady CFD analyses which have an equivalent reduced frequency of zero. These factors are applied to both the real and imaginary part of the aerodynamic matrices as well as all reduced frequencies used in the PK-Method which solves flutter problems. The modal-based AIC method
Assessment of aerodynamic and dynamic models in a comprehensive analysis
NASA Technical Reports Server (NTRS)
Johnson, W.
1985-01-01
The history, status, and lessons of a comprehensive analysis for rotorcraft are reviewed. The development, features, and capabilities of the analysis are summarized, including the aerodynamic and dynamic models that were used. Examples of correlation of the computational results with experimental data are given, extensions of the analysis for research in several topics of helicopter technology are discussed, and the experiences of outside users are summarized. Finally, the required capabilities and approach for the next comprehensive analysis are described.
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.
Multidisciplinary Aerodynamic-Structural Shape Optimization Using Deformation (MASSOUD)
NASA Technical Reports Server (NTRS)
Samareh, Jamshid A.
2000-01-01
This paper presents a multidisciplinary shape parameterization approach. The approach consists of two basic concepts: (1) parameterizing the shape perturbations rather than the geometry itself and (2) performing the shape deformation by means of the soft object animation algorithms used in computer graphics. Because the formulation presented in this paper is independent of grid topology, we can treat computational fluid dynamics and finite element grids in the same manner. The proposed approach is simple, compact, and efficient. Also, the analytical sensitivity derivatives are easily computed for use in a gradient-based optimization. This algorithm is suitable for low-fidelity (e.g., linear aerodynamics and equivalent laminate plate structures) and high-fidelity (e.g., nonlinear computational fluid dynamics and detailed finite element modeling) analysis tools. This paper contains the implementation details of parameterizing for planform, twist, dihedral, thickness, camber, and free-form surface. Results are presented for a multidisciplinary application consisting of nonlinear computational fluid dynamics, detailed computational structural mechanics, and a simple performance module.
Rotor Airloads Prediction Using Loose Aerodynamic Structural Coupling
NASA Technical Reports Server (NTRS)
Potsdam, Mark; Yeo, Hyeonsoo; Johnson, Wayne
2004-01-01
This work couples a computational fluid dynamics (CFD) code and rotorcraft computational structural dynamics (CSD) code to calculate helicopter rotor airloads across a range of flight conditions. An iterative loose (weak) coupling methodology is used to couple the CFD and CSD codes on a per revolution, periodic basis. The CFD uses a high fidelity, Navier-Stokes, overset grid methodology with first principles-based wake capturing. Modifications are made to the CFD code for aeroelastic analysis. For a UH-60A Blackhawk helicopter, four challenging level flight conditions are computed: 1) low speed (u = 0.15) with blade-vortex interaction, 2) high speed (u = 0.37) with advancing blade negative lift, 3) high thrust with dynamic stall (u = 0.24), and 4) hover. Results are compared with UH-60A Airloads Program fight test data. Most importantly, for all cases the loose coupling methodology is shown to be stable, convergent, and robust with full coupling of normal force, pitching moment, and chord force. In comparison with flight test data, normal force and pitching moment magnitudes are in good agreement. For the high speed and dynamic stall cases a phase lag in comparison with the data is seen, nonetheless, the shapes of the curves are very good. Overall, the results are noteworthy improvement over lifting line aerodynamics used in rotorcraft comprehensive codes.
Fully integrated aerodynamic/dynamic optimization of helicopter rotor blades
NASA Technical Reports Server (NTRS)
Walsh, Joanne L.; Lamarsh, William J., II; Adelman, Howard M.
1992-01-01
A fully integrated aerodynamic/dynamic optimization procedure is described for helicopter rotor blades. The procedure combines performance and dynamic analyses with a general purpose optimizer. The procedure minimizes a linear combination of power required (in hover, forward flight, and maneuver) and vibratory hub shear. The design variables include pretwist, taper initiation, taper ratio, root chord, blade stiffnesses, tuning masses, and tuning mass locations. Aerodynamic constraints consist of limits on power required in hover, forward flight and maneuvers; airfoil section stall; drag divergence Mach number; minimum tip chord; and trim. Dynamic constraints are on frequencies, minimum autorotational inertia, and maximum blade weight. The procedure is demonstrated for two cases. In the first case, the objective function involves power required (in hover, forward flight and maneuver) and dynamics. The second case involves only hover power and dynamics. The designs from the integrated procedure are compared with designs from a sequential optimization approach in which the blade is first optimized for performance and then for dynamics. In both cases, the integrated approach is superior.
Unsteady aerodynamics of reverse flow dynamic stall on an oscillating blade section
NASA Astrophysics Data System (ADS)
Lind, Andrew H.; Jones, Anya R.
2016-07-01
Wind tunnel experiments were performed on a sinusoidally oscillating NACA 0012 blade section in reverse flow. Time-resolved particle image velocimetry and unsteady surface pressure measurements were used to characterize the evolution of reverse flow dynamic stall and its sensitivity to pitch and flow parameters. The effects of a sharp aerodynamic leading edge on the fundamental flow physics of reverse flow dynamic stall are explored in depth. Reynolds number was varied up to Re = 5 × 105, reduced frequency was varied up to k = 0.511, mean pitch angle was varied up to 15∘, and two pitch amplitudes of 5∘ and 10∘ were studied. It was found that reverse flow dynamic stall of the NACA 0012 airfoil is weakly sensitive to the Reynolds numbers tested due to flow separation at the sharp aerodynamic leading edge. Reduced frequency strongly affects the onset and persistence of dynamic stall vortices. The type of dynamic stall observed (i.e., number of vortex structures) increases with a decrease in reduced frequency and increase in maximum pitch angle. The characterization and parameter sensitivity of reverse flow dynamic stall given in the present work will enable the development of a physics-based analytical model of this unsteady aerodynamic phenomenon.
Efficient optimization of integrated aerodynamic-structural design
NASA Technical Reports Server (NTRS)
Haftka, R. T.; Grossman, B.; Eppard, W. M.; Kao, P. J.; Polen, D. M.
1989-01-01
Techniques for reducing the computational complexity of multidisciplinary design optimization (DO) of aerodynamic structures are described and demonstrated. The basic principles of aerodynamic and structural DO are reviewed; the formulation of the combined DO problem is outlined; and particular attention is given to (1) the application of perturbation methods to cross-sensitivity computations and (2) numerical approximation procedures. Trial DOs of a simple sailplane design are presented in tables and graphs and discussed in detail. The IBM 3090 CPU time for the entire integrated DO was reduced from an estimated 10 h to about 6 min.
A dynamic counterpart of Lamb vector in viscous compressible aerodynamics
NASA Astrophysics Data System (ADS)
Liu, L. Q.; Wu, J. Z.; Shi, Y. P.; Zhu, J. Y.
2014-12-01
The Lamb vector is known to play a key role in incompressible fluid dynamics and vortex dynamics. In particular, in low-speed steady aerodynamics it is solely responsible for the total force acting on a moving body, known as the vortex force, with the classic two-dimensional (exact) Kutta-Joukowski theorem and three-dimensional (linearized) lifting-line theory as the most famous special applications. In this paper we identify an innovative dynamic counterpart of the Lamb vector in viscous compressible aerodynamics, which we call the compressible Lamb vector. Mathematically, we present a theorem on the dynamic far-field decay law of the vorticity and dilatation fields, and thereby prove that the generalized Lamb vector enjoys exactly the same integral properties as the Lamb vector does in incompressible flow, and hence the vortex-force theory can be generalized to compressible flow with exactly the same general formulation. Moreover, for steady flow of polytropic gas, we show that physically the force exerted on a moving body by the gas consists of a transverse force produced by the original Lamb vector and a new longitudinal force that reflects the effects of compression and irreversible thermodynamics.
Aerodynamic-structural model of offwind yacht sails
NASA Astrophysics Data System (ADS)
Mairs, Christopher M.
An aerodynamic-structural model of offwind yacht sails was created that is useful in predicting sail forces. Two sails were examined experimentally and computationally at several wind angles to explore a variety of flow regimes. The accuracy of the numerical solutions was measured by comparing to experimental results. The two sails examined were a Code 0 and a reaching asymmetric spinnaker. During experiment, balance, wake, and sail shape data were recorded for both sails in various configurations. Two computational steps were used to evaluate the computational model. First, an aerodynamic flow model that includes viscosity effects was used to examine the experimental flying shapes that were recorded. Second, the aerodynamic model was combined with a nonlinear, structural, finite element analysis (FEA) model. The aerodynamic and structural models were used iteratively to predict final flying shapes of offwind sails, starting with the design shapes. The Code 0 has relatively low camber and is used at small angles of attack. It was examined experimentally and computationally at a single angle of attack in two trim configurations, a baseline and overtrimmed setting. Experimentally, the Code 0 was stable and maintained large flow attachment regions. The digitized flying shapes from experiment were examined in the aerodynamic model. Force area predictions matched experimental results well. When the aerodynamic-structural tool was employed, the predictive capability was slightly worse. The reaching asymmetric spinnaker has higher camber and operates at higher angles of attack than the Code 0. Experimentally and computationally, it was examined at two angles of attack. Like the Code 0, at each wind angle, baseline and overtrimmed settings were examined. Experimentally, sail oscillations and large flow detachment regions were encountered. The computational analysis began by examining the experimental flying shapes in the aerodynamic model. In the baseline setting, the
Subsonic Static and Dynamic Aerodynamics of Blunt Entry Vehicles
NASA Technical Reports Server (NTRS)
Mitcheltree, Robert A.; Fremaux, Charles M.; Yates, Leslie A.
1999-01-01
The incompressible subsonic aerodynamics of four entry-vehicle shapes with variable c.g. locations are examined in the Langley 20-Foot Vertical Spin Tunnel. The shapes examined are spherically-blunted cones with half-cone angles of 30, 45, and 60 deg. The nose bluntness varies between 0.25 and 0.5 times the base diameter. The Reynolds number based on model diameter for these tests is near 500,000. Quantitative data on attitude and location are collected using a video-based data acquisition system and reduced with a six deg-of-freedom inverse method. All of the shapes examined suffered from strong dynamic instabilities which could produced limit cycles with sufficient amplitudes to overcome static stability of the configuration. Increasing cone half-angle or nose bluntness increases drag but decreases static and dynamic stability.
Naziar, J.; Couch, R.; Davis, M.
1996-01-01
Traditionally, aeropropulsion structural performance and aerodynamic performance have been designed separately and later mated together via flight testing. In today`s atmosphere of declining resources, it is imperative that more productive ways of designing and verifying aeropropulsion performance and structural interaction be made available to the aerospace industry. One method of obtaining a more productive design and evaluation capability is through the use of numerical simulations. Currently, Lawrence Livermore National Laboratory has developed a generalized fluid/structural interaction code known as ALE3D. This code is capable of characterizing fluid and structural interaction for components such as the combustor, fan/stators, inlet and/or nozzles. This code solves the 3D Euler equations and has been applied to several aeropropulsion applications such as a supersonic inlet and a combustor rupture simulation. To characterize aerodynamic-structural interaction for rotating components such as the compressor, appropriate turbomachinery simulations would need to be implemented within the ALE3D structure. The Arnold Engineering Development Center is currently developing a three-dimensional compression system code known as TEACC (Turbine Engine Analysis Compressor Code). TEACC also solves the 3D Euler equations and is intended to simulate dynamic behavior such as inlet distortion, surge or rotating stall. The technology being developed within the TEACC effort provides the necessary turbomachinery simulation for implementation into ALE3D. This paper describes a methodology to combine three-dimensional aerodynamic turbomachinery technology into the existing aerodynamic-structural interaction simulation, ALE3D to obtain the desired aerodynamic and structural integrated simulation for an aeropropulsion system.
Fluid-thermal-structural study of aerodynamically heated leading edges
NASA Technical Reports Server (NTRS)
Deuchamphai, Pramote; Thornton, Earl A.; Wieting, Allan R.
1988-01-01
A finite element approach for integrated fluid-thermal-structural analysis of aerodynamically heated leading edges is presented. The Navier-Stokes equations for high speed compressible flow, the energy equation, and the quasi-static equilibrium equations for the leading edge are solved using a single finite element approach in one integrated, vectorized computer program called LIFTS. The fluid-thermal-structural coupling is studied for Mach 6.47 flow over a 3-in diam cylinder for which the flow behavior and the aerothermal loads are calibrated by experimental data. Issues of the thermal-structural response are studied for hydrogen-cooled, super thermal conducting leading edges subjected to intense aerodynamic heating.
Integrated aerodynamic-structural design of a transport wing
NASA Technical Reports Server (NTRS)
Grossman, B.; Haftka, R. T.; Kao, P.-J.; Polen, D. M.; Rais-Rohani, M.; Sobieszczanski-Sobieski, J.
1989-01-01
The integrated aerodynamic-structural design of a subsonic transport wing for minimum weight subject to required range is formulated and solved. The problem requires large computational resources, and two methods are used to alleviate the computational burden. First, a modular sensitivity method that permits the usage of black-box disciplinary software packages, is used to reduce the cost of sensitivity derivatives. In particular, it is shown that derivatives of the aeroelastic response and divergence speed can be calculated without the costly computation of derivatives of aerodynamic influence coefficient and structural stiffness matrices. A sequential approximate optimization is used to further reduce computational cost. The optimization procedure is shown to require a relatively small number of analysis and sensitivity calculations.
Aerodynamic role of dynamic wing morphing in hummingbird maneuvering flight
NASA Astrophysics Data System (ADS)
Ren, Yan; Shallcross, Gregory; Dong, Haibo; Deng, Xinyan; Tobalske, Bret; Flow Simulation Research Group Team; Bio-robotics lab Collaboration; University of Montana Flight Laboratory Collaboration
2014-11-01
The flexibility and deformation of hummingbird wing gives hummingbird a great degree of control over fluid forces in flapping flight. Unlike insect wing's passive deformation, hummingbird wing employs a more complicated wing morphing mechanism through both active muscle control and passive feather-air interaction, which results in highly complex 3D wing topology variations during the unsteady flight. Three camera high speed (1000 fps) high resolution digital video was taken and digitized to measure 3D wing conformation in all its complexity during steady flying and maneuvering. Results have shown that the dynamic wing morphing is more prominent in maneuvering flight. Complicated cambering and twisting patterns are observed along the wing pitching axis. A newly developed immersed boundary method which realistically models wing-joint-body of the hummingbird is then employed to simulate the flow associated with dynamic morphing. The simulations provide a first of its kind glimpse of the fluid and vortex dynamics associated with dynamic wing morphing and aerodynamic force computations allow us to gain a better understanding of force producing mechanisms in hummingbird maneuvering flight. This work is supported by AFOSR FA9550-12-1-007 and NSF CEBT-1313217.
Aero-Structural Assessment of an Inflatable Aerodynamic Decelerator
NASA Technical Reports Server (NTRS)
Sheta, Essam F.; Venugopalan, Vinod; Tan, X. G.; Liever, Peter A.; Habchi, Sami D.
2010-01-01
NASA is conducting an Entry, Descent and Landing Systems Analysis (EDL-SA) Study to determine the key technology development projects that should be undertaken for enabling the landing of large payloads on Mars for both human and robotic missions. Inflatable Aerodynamic Decelerators (IADs) are one of the candidate technologies. A variety of EDL architectures are under consideration. The current effort is conducted for development and simulations of computational framework for inflatable structures.
Structural effects of unsteady aerodynamic forces on horizontal-axis wind turbines
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.
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.
CFD based aerodynamic modeling to study flight dynamics of a flapping wing micro air vehicle
NASA Astrophysics Data System (ADS)
Rege, Alok Ashok
The demand for small unmanned air vehicles, commonly termed micro air vehicles or MAV's, is rapidly increasing. Driven by applications ranging from civil search-and-rescue missions to military surveillance missions, there is a rising level of interest and investment in better vehicle designs, and miniaturized components are enabling many rapid advances. The need to better understand fundamental aspects of flight for small vehicles has spawned a surge in high quality research in the area of micro air vehicles. These aircraft have a set of constraints which are, in many ways, considerably different from that of traditional aircraft and are often best addressed by a multidisciplinary approach. Fast-response non-linear controls, nano-structures, integrated propulsion and lift mechanisms, highly flexible structures, and low Reynolds aerodynamics are just a few of the important considerations which may be combined in the execution of MAV research. The main objective of this thesis is to derive a consistent nonlinear dynamic model to study the flight dynamics of micro air vehicles with a reasonably accurate representation of aerodynamic forces and moments. The research is divided into two sections. In the first section, derivation of the nonlinear dynamics of flapping wing micro air vehicles is presented. The flapping wing micro air vehicle (MAV) used in this research is modeled as a system of three rigid bodies: a body and two wings. The design is based on an insect called Drosophila Melanogaster, commonly known as fruit-fly. The mass and inertial effects of the wing on the body are neglected for the present work. The nonlinear dynamics is simulated with the aerodynamic data published in the open literature. The flapping frequency is used as the control input. Simulations are run for different cases of wing positions and the chosen parameters are studied for boundedness. Results show a qualitative inconsistency in boundedness for some cases, and demand a better
Simultaneous Aerodynamic and Structural Design Optimization (SASDO) for a 3-D Wing
NASA Technical Reports Server (NTRS)
Gumbert, Clyde R.; Hou, Gene J.-W.; Newman, Perry A.
2001-01-01
The formulation and implementation of an optimization method called Simultaneous Aerodynamic and Structural Design Optimization (SASDO) is shown as an extension of the Simultaneous Aerodynamic Analysis and Design Optimization (SAADO) method. It is extended by the inclusion of structure element sizing parameters as design variables and Finite Element Method (FEM) analysis responses as constraints. The method aims to reduce the computational expense. incurred in performing shape and sizing optimization using state-of-the-art Computational Fluid Dynamics (CFD) flow analysis, FEM structural analysis and sensitivity analysis tools. SASDO is applied to a simple. isolated, 3-D wing in inviscid flow. Results show that the method finds the saine local optimum as a conventional optimization method with some reduction in the computational cost and without significant modifications; to the analysis tools.
NASA Technical Reports Server (NTRS)
1980-01-01
Advanced rotorcraft technology and tilt rotor aircraft were discussed. Rotorcraft performance, acoustics, and vibrations were discussed, as was the use of composite materials in rotorcraft structures. Rotorcraft aerodynamics, specifically the aerodynamic phenomena of a rotating and the aerodynamics of fuselages, was discussed.
Impact of high-alpha aerodynamics on dynamic stability parameters of aircraft and missiles
NASA Technical Reports Server (NTRS)
Malcolm, G. N.
1981-01-01
The aerodynamic phenomena associated with high angles of attack and their effects on the dynamic stability characteristics of airplane and missile configurations are examined. Information on dynamic effects is limited. Steady flow phenomena and their effects on the forces and moments are reviewed. The effects of asymmetric vortices and of vortex bursting on the dynamic response of flight vehicles are reviewed with respect to their influence on: (1) nonlinearity of aerodynamic coefficients with attitude, rates, and accelerations; (2) cross coupling between longitudinal and lateral directional models of motion; (3) time dependence and hysteresis effects; (4) configuration dependencey; and (5) mathematical modeling of the aerodynamics.
Coupled Aerodynamic and Structural Sensitivity Analysis of a High-Speed Civil Transport
NASA Technical Reports Server (NTRS)
Mason, B. H.; Walsh, J. L.
2001-01-01
An objective of the High Performance Computing and Communication Program at the NASA Langley Research Center is to demonstrate multidisciplinary shape and sizing optimization of a complete aerospace vehicle configuration by using high-fidelity, finite-element structural analysis and computational fluid dynamics aerodynamic analysis. In a previous study, a multi-disciplinary analysis system for a high-speed civil transport was formulated to integrate a set of existing discipline analysis codes, some of them computationally intensive, This paper is an extension of the previous study, in which the sensitivity analysis for the coupled aerodynamic and structural analysis problem is formulated and implemented. Uncoupled stress sensitivities computed with a constant load vector in a commercial finite element analysis code are compared to coupled aeroelastic sensitivities computed by finite differences. The computational expense of these sensitivity calculation methods is discussed.
NASA Astrophysics Data System (ADS)
Liu, Hao; Nakata, Toshiyuki; Gao, Na; Maeda, Masateru; Aono, Hikaru; Shyy, Wei
2010-12-01
Aiming at developing an effective tool to unveil key mechanisms in bio-flight as well as to provide guidelines for bio-inspired micro air vehicles (MAVs) design, we propose a comprehensive computational framework, which integrates aerodynamics, flight dynamics, vehicle stability and maneuverability. This framework consists of (1) a Navier-Stokes unsteady aerodynamic model; (2) a linear finite element model for structural dynamics; (3) a fluid-structure interaction (FSI) model for coupled flexible wing aerodynamics aeroelasticity; (4) a free-flying rigid body dynamic (RBD) model utilizing the Newtonian-Euler equations of 6DoF motion; and (5) flight simulator accounting for realistic wing-body morphology, flapping-wing and body kinematics, and a coupling model accounting for the nonlinear 6DoF flight dynamics and stability of insect flapping flight. Results are presented based on hovering aerodynamics with rigid and flexible wings of hawkmoth and fruitfly. The present approach can support systematic analyses of bio- and bio-inspired flight.
Mathematical modeling of the aerodynamic characteristics in flight dynamics
NASA Technical Reports Server (NTRS)
Tobak, M.; Chapman, G. T.; Schiff, L. B.
1984-01-01
Basic concepts involved in the mathematical modeling of the aerodynamic response of an aircraft to arbitrary maneuvers are reviewed. The original formulation of an aerodynamic response in terms of nonlinear functionals is shown to be compatible with a derivation based on the use of nonlinear functional expansions. Extensions of the analysis through its natural connection with ideas from bifurcation theory are indicated.
Fluid Dynamics Panel Symposium on Aerodynamics of Power Plant Installation
NASA Technical Reports Server (NTRS)
Henderson, W. P.
1982-01-01
Powerplant installations involve complex flows, strongly influenced by viscous effects and often with important aerodynamic interactions between the airframe and propulsion system. The introduction of vehicle propulsion concepts, and points of emphasis in aircraft and missile design requirements, provide an expanding range of aerodynamic problems which cal for both experimental and theoretical study. Aerodynamic problems in powerplant installation are surveyed and work which has improved basic understanding or has enhanced prediction and design methods in this field is reviewed. Powerplant installation effects for both combat and transport aircraft are emphasized.
Single annular combustor: Experimental investigations of aerodynamics, dynamics and emissions
NASA Astrophysics Data System (ADS)
Mohammad, Bassam Sabry
The present work investigates the aerodynamics, dynamics and emissions of a Single Cup Combustor Sector. The Combustor resembles a real Gas Turbine Combustor with primary, secondary and dilution zones (also known as fuel rich dome combustor). The research is initiated by studying the effect of the combustor front end geometry on the flow field. Two different exit configurations (one causes a sudden expansion to the swirling flow while the other causes a gradual expansion), installed in a dump combustor, are tested using LDV. The results reveal that the expanding surface reduces the turbulence activities, eliminates the corner recirculation zone and increases the length of the CRZ appreciably. An asymmetry in the flow field is observed due to the asymmetry of the expanding surface. To study the effect of chamber geometry on the flow field, the dome configuration is tested in the combustor sector with the primary dilution jets blocked. The size of the CRZ is reduced significantly (40% reduction in the height). With active primary jets, the CRZ is reconstructed in 3D by conducting several PIV measurements off-center. The confinement appears to significantly influence the shape of the CRZ such that the area ratio is similar for both the confinement and the CRZ (approximately 85%). The primary jets considerably contribute to the heat release process at high power conditions. Also, the primary jets drastically impact the flow field structure. Therefore, the parameters influencing the primary jets are studied using PIV (pressure drop, jets size, off-centering, interaction with convective cooling air, jet blockage and fuel injection). This study is referred to as a jet sensitivity study. The results indicate that the primary jets can be used effectively in controlling the flow field structure. A pressure drop of 4.3% and 7.6% result in similar flows with no noticeable effect on the size of the CRZ and the four jets wake regions. On the other hand, the results show that the
Integrated aerodynamic and dynamic optimization of tiltrotor wing and rotor systems
NASA Astrophysics Data System (ADS)
Orr, Stanley
Rotorcraft analysis and design must account for interdisciplinary interactions, especially between aerodynamics, structural, and dynamics responses. In this design domain, the work of disciplinary experts is segregated to a large extent. Furthermore, the design of subsystems is also segregated. In this environment it is difficult to account for interdisciplinary interactions and exploit the coupling between sub systems. This work examined the multidisciplinary nature of a tiltrotor aircraft focusing on the aerodynamic design of the rotor, and the structural and dynamic design of the rotor and wing systems. The design was considered to be in the preliminary design phase, after the basic configuration is set and before fine details of the design are defined. Attention was focused on developing an optimization problem formulation that was sufficiently complete so that optimization technologies and heuristic strategies could be developed and evaluated for tiltrotor design. Furthermore the level of detail in the analysis was consistent with the phase of design. Coupling between the aerodynamic, dynamic, and structural design was shown to be significant. Additionally, the coupling between the design of the wing and rotor systems was also significant, so that an integrated design was required. This work developed integrated design strategies for solving this design problem efficiently, while exploiting the couplings. Sum of system weights was the main objective along with vibratory rotor hub loads while hover performance, strength, frequency placement, and stability were constraints. Design variables included blade aerodynamic planform and twist as well as the details of composite D-spar blade sections, and details of composite torque-box wing sections. Cruise mode rotor speed and wing thickness were also included as design variables. A genetic algorithm based collaborative optimization was used as the solution framework for the global optimal search. The problem was
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.
Matha, D.; Schlipf, M.; Cordle, A.; Pereira, R.; Jonkman, J.
2011-10-01
This paper presents the current major modeling challenges for floating offshore wind turbine design tools and describes aerodynamic and hydrodynamic effects due to rotor and platform motions and usage of non-slender support structures.
NASA Technical Reports Server (NTRS)
Van Norman, John W.; Dyakonov, Artem; Schoenenberger, Mark; Davis, Jody; Muppidi, Suman; Tang, Chun; Bose, Deepak; Mobley, Brandon; Clark, Ian
2015-01-01
An overview of pre-flight aerodynamic models for the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) campaign is presented, with comparisons to reconstructed flight data and discussion of model updates. The SFDT campaign objective is to test Supersonic Inflatable Aerodynamic Decelerator (SIAD) and large supersonic parachute technologies at high altitude Earth conditions relevant to entry, descent, and landing (EDL) at Mars. Nominal SIAD test conditions are attained by lifting a test vehicle (TV) to 36 km altitude with a large helium balloon, then accelerating the TV to Mach 4 and and 53 km altitude with a solid rocket motor. The first flight test (SFDT-1) delivered a 6 meter diameter robotic mission class decelerator (SIAD-R) to several seconds of flight on June 28, 2014, and was successful in demonstrating the SFDT flight system concept and SIAD-R. The trajectory was off-nominal, however, lofting to over 8 km higher than predicted in flight simulations. Comparisons between reconstructed flight data and aerodynamic models show that SIAD-R aerodynamic performance was in good agreement with pre-flight predictions. Similar comparisons of powered ascent phase aerodynamics show that the pre-flight model overpredicted TV pitch stability, leading to underprediction of trajectory peak altitude. Comparisons between pre-flight aerodynamic models and reconstructed flight data are shown, and changes to aerodynamic models using improved fidelity and knowledge gained from SFDT-1 are discussed.
Numerical investigation of the aerodynamic and structural characteristics of a corrugated wing
NASA Astrophysics Data System (ADS)
Hord, Kyle
Previous experimental studies on static, bio-inspired corrugated wings have shown that they produce favorable aerodynamic properties such as delayed stall compared to streamlined wings and flat plates at high Reynolds numbers (Re ≥ 4x104). The majority of studies have been carried out with scaled models of dragonfly forewings from the Aeshna Cyanea in either wind tunnels or water channels. In this thesis, the aerodynamics of a corrugated airfoil was studied using computational fluid dynamics methods at a low Reynolds number of 1000. Structural analysis was also performed using the commercial software SolidWorks 2009. The flow field is described by solving the incompressible Navier-Stokes equations on an overlapping grid using the pressure-Poisson method. The equations are discretized in space with second-order accurate central differences. Time integration is achieved through the second-order Crank-Nicolson implicit method. The complex vortex structures that form in the corrugated airfoil valleys and around the corrugated airfoil are studied in detail. Comparisons are made with experimental measurements from corrugated wings and also with simulations of a flat plate. Contrary to the studies at high Reynolds numbers, our study shows that at low Reynolds numbers the wing corrugation does not provide any aerodynamic benefit compared to a smoothed flat plate. Instead, the corrugated profile generates more pressure drag which is only partially offset by the reduction of friction drag, leading to more total drag than the flat plate. Structural analysis shows that the wing corrugation can increase the resistance to bending moments on the wing structure. A smoothed structure has to be three times thicker to provide the same stiffness. It was concluded the corrugated wing has the structural benefit to provide the same resistance to bending moments with a much reduced weight.
Aerodynamic, structural, and trajectory analysis of ASTRID-1 vehicle
Glover, L.S.; Iwaskiw, A.P.; Oursler, M.A.; Perini, L.L.; Schaefer, E.D.
1994-02-10
The Johns Hopkins University/Applied Physics Laboratory, JHU/API, in support of Lawrence Livermore National Laboratory, LLNL, is conducting aerodynamic, trajectory, and structural analysis of the Advanced Single Stage Technology Rapid Insertion Demonstration (ASTRID) vehicle, being launched out of Vandenberg Air Force Base (VAFB) in February 1994. The launch is designated ASTRID-1 and is the first in a series of three that will be launched out of VAFB. Launch dates for the next two flights have not been identified, but they are scheduled for the 1994-1995 time frame. The primary goal of the ASTRID-1 flight is to test the LLNL light weight thrust on demand bi-propellant pumped divert propulsion system. The system is employed as the main thrusters for the ASTRID-1 vehicle and uses hydrazine as the mono-propellant. The major conclusions are: (1) The vehicle is very stable throughout flight (stability margin = 17 to 24 inches); (2) The aerodynamic frequency and the roll rate are such that pitch-roll interactions will be small; (3) The high stability margin combined with the high launcher elevation angle makes the vehicle flight path highly sensitive to perturbations during the initial phase of flight, i.e., during the first second of flight after leaving the rail; (4) The major impact dispersions for the test flight are due to winds. The wind impact dispersions are 90% dictated by the low altitude, 0 to 1000 ft., wind conditions; and (5) In order to minimize wind dispersions, head wind conditions are favored for the launch as November VAFB mean tail winds result in land impacts. The ballistic wind methodology can be employed to assess the impact points of winds at the launch site.
Shock Structure Analysis and Aerodynamics in a Weakly Ionized Gas Flow
NASA Technical Reports Server (NTRS)
Saeks, R.; Popovic, S.; Chow, A. S.
2006-01-01
The structure of a shock wave propagating through a weakly ionized gas is analyzed using an electrofluid dynamics model composed of classical conservation laws and Gauss Law. A viscosity model is included to correctly model the spatial scale of the shock structure, and quasi-neutrality is not assumed. A detailed analysis of the structure of a shock wave propagating in a weakly ionized gas is presented, together with a discussion of the physics underlying the key features of the shock structure. A model for the flow behind a shock wave propagating through a weakly ionized gas is developed and used to analyze the effect of the ionization on the aerodynamics and performance of a two-dimensional hypersonic lifting body.
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.
Modeling, Control, and Estimation of Flexible, Aerodynamic Structures
NASA Astrophysics Data System (ADS)
Ray, Cody W.
Engineers have long been inspired by nature’s flyers. Such animals navigate complex environments gracefully and efficiently by using a variety of evolutionary adaptations for high-performance flight. Biologists have discovered a variety of sensory adaptations that provide flow state feedback and allow flying animals to feel their way through flight. A specialized skeletal wing structure and plethora of robust, adaptable sensory systems together allow nature’s flyers to adapt to myriad flight conditions and regimes. In this work, motivated by biology and the successes of bio-inspired, engineered aerial vehicles, linear quadratic control of a flexible, morphing wing design is investigated, helping to pave the way for truly autonomous, mission-adaptive craft. The proposed control algorithm is demonstrated to morph a wing into desired positions. Furthermore, motivated specifically by the sensory adaptations organisms possess, this work transitions to an investigation of aircraft wing load identification using structural response as measured by distributed sensors. A novel, recursive estimation algorithm is utilized to recursively solve the inverse problem of load identification, providing both wing structural and aerodynamic states for use in a feedback control, mission-adaptive framework. The recursive load identification algorithm is demonstrated to provide accurate load estimate in both simulation and experiment.
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.
Drones for aerodynamic and structural testing /DAST/ - A status report
NASA Technical Reports Server (NTRS)
Murrow, H. N.; Eckstrom, C. V.
1978-01-01
A program for providing research data on aerodynamic loads and active control systems on wings with supercritical airfoils in the transonic speed range is described. Analytical development, wind tunnel tests, and flight tests are included. A Firebee II target drone vehicle has been modified for use as a flight test facility. The program currently includes flight experiments on two aeroelastic research wings. The primary purpose of the first flight experiment is to demonstrate an active control system for flutter suppression on a transport-type wing. Design and fabrication of the wing are complete and after installing research instrumentation and the flutter suppression system, flight testing is expected to begin in early 1979. The experiment on the second research wing - a fuel-conservative transport type - is to demonstrate multiple active control systems including flutter suppression, maneuver load alleviation, gust load alleviation, and reduce static stability. Of special importance for this second experiment is the development and validation of integrated design methods which include the benefits of active controls in the structural design.
Aerodynamic and Nonlinear Dynamic Acoustic Analysis of Tension Asymmetry in Excised Canine Larynges
ERIC Educational Resources Information Center
Devine, Erin E.; Bulleit, Erin E.; Hoffman, Matthew R.; McCulloch, Timothy M.; Jiang, Jack J.
2012-01-01
Purpose: To model tension asymmetry caused by superior laryngeal nerve paralysis (SLNP) in excised larynges and apply perturbation, nonlinear dynamic, and aerodynamic analyses. Method: SLNP was modeled in 8 excised larynges using sutures and weights to mimic cricothyroid (CT) muscle function. Weights were removed from one side to create tension…
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.
Dynamic Control of Aerodynamic Instabilities in Gas Turbine Engines
NASA Technical Reports Server (NTRS)
Greitzer, E. M.; Epstein, A. H.; Guenette, G. R.; Gysling, D. L.; Haynes, J.; Hendricks, G. J.; Paduano, J.; Simon, J. S.; Valavani, L.
1992-01-01
This lecture discusses the use of closed loop control at the component level to enhance the performance of gas turbine engines. The general theme is the suppression of flow instabilities (rotating stall and surge) through use of feedback, either actively or by means of the aeromechanical coupling provided by tailored structures. The basic concepts that underlie active control of turbomachinery instability, and their experimental demonstration, are first described for a centrifugal compressor. It is shown that the mechanism for stabilization is associated with damping of unsteady perturbations in the compression system, and the steady-state performance can thus remain virtually unaltered. Control of instability using a tailored structure is then discussed, along with experimental results illustrating the flow range extension achievable using this technique. A considerably more complex problem is presented by active control or rotating stall where the multi-dimensional features mean that distributed sensing and actuation are required. In addition, there are basic questions concerning unsteady fluid mechanics; these imply the need to resolve issues connected with identification of suitable signals as well as with definition of appropriate wave launchers for implementing the feedback. These issues are discussed and the results of initial successful demonstrations of active control of rotating stall in a single-stage and a three-stage axial compressor are presented. The lecture concludes with suggestions for future research on dynamic control of gas turbine engines.
System Dynamic Analysis of a Wind Tunnel Model with Applications to Improve Aerodynamic Data Quality
NASA Technical Reports Server (NTRS)
Buehrle, Ralph David
1997-01-01
The research investigates the effect of wind tunnel model system dynamics on measured aerodynamic data. During wind tunnel tests designed to obtain lift and drag data, the required aerodynamic measurements are the steady-state balance forces and moments, pressures, and model attitude. However, the wind tunnel model system can be subjected to unsteady aerodynamic and inertial loads which result in oscillatory translations and angular rotations. The steady-state force balance and inertial model attitude measurements are obtained by filtering and averaging data taken during conditions of high model vibrations. The main goals of this research are to characterize the effects of model system dynamics on the measured steady-state aerodynamic data and develop a correction technique to compensate for dynamically induced errors. Equations of motion are formulated for the dynamic response of the model system subjected to arbitrary aerodynamic and inertial inputs. The resulting modal model is examined to study the effects of the model system dynamic response on the aerodynamic data. In particular, the equations of motion are used to describe the effect of dynamics on the inertial model attitude, or angle of attack, measurement system that is used routinely at the NASA Langley Research Center and other wind tunnel facilities throughout the world. This activity was prompted by the inertial model attitude sensor response observed during high levels of model vibration while testing in the National Transonic Facility at the NASA Langley Research Center. The inertial attitude sensor cannot distinguish between the gravitational acceleration and centrifugal accelerations associated with wind tunnel model system vibration, which results in a model attitude measurement bias error. Bias errors over an order of magnitude greater than the required device accuracy were found in the inertial model attitude measurements during dynamic testing of two model systems. Based on a theoretical modal
A comprehensive analytical model of rotorcraft aerodynamics and dynamics. Part 2: User's manual
NASA Technical Reports Server (NTRS)
Johnson, W.
1980-01-01
The use of a computer program for a comprehensive analytical model of rotorcraft aerodynamics and dynamics is described. The program calculates the loads and motion of helicopter rotors and airframe. First the trim solution is obtained, then the flutter, flight dynamics, and/or transient behavior can be calculated. Either a new job can be initiated or further calculations can be performed for an old job.
NASA Astrophysics Data System (ADS)
Wu, Chengjun; Liu, Jiang; Pan, Jie
2014-07-01
DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics(CFD) and computational aerodynamic acoustics(CAA) simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures(i.e. the heat sink, the bell-mouth type shroud and the outlet grille) upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring's size and throat's depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %(i.e. 100 m3·h-1) at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.
Structural/aerodynamic Blade Analyzer (SAB) User's Guide, Version 1.0
NASA Technical Reports Server (NTRS)
Morel, M. R.
1994-01-01
The structural/aerodynamic blade (SAB) analyzer provides an automated tool for the static-deflection analysis of turbomachinery blades with aerodynamic and rotational loads. A structural code calculates a deflected blade shape using aerodynamic loads input. An aerodynamic solver computes aerodynamic loads using deflected blade shape input. The two programs are iterated automatically until deflections converge. Currently, SAB version 1.0 is interfaced with MSC/NASTRAN to perform the structural analysis and PROP3D to perform the aerodynamic analysis. This document serves as a guide for the operation of the SAB system with specific emphasis on its use at NASA Lewis Research Center (LeRC). This guide consists of six chapters: an introduction which gives a summary of SAB; SAB's methodology, component files, links, and interfaces; input/output file structure; setup and execution of the SAB files on the Cray computers; hints and tips to advise the user; and an example problem demonstrating the SAB process. In addition, four appendices are presented to define the different computer programs used within the SAB analyzer and describe the required input decks.
On the generation of flight dynamics aerodynamic tables by computational fluid dynamics
NASA Astrophysics Data System (ADS)
Da Ronch, A.; Ghoreyshi, M.; Badcock, K. J.
2011-11-01
An approach for the generation of aerodynamic tables using computational fluid dynamics is discussed. For aircraft flight dynamics, forces and moments are often tabulated in multi-dimensional look-up tables, requiring a large number of calculations to fill the tables. A method to efficiently reduce the number of high-fidelity analyses is reviewed. The method uses a kriging-based surrogate model. Low-fidelity (computationally cheap) estimates are augmented with higher fidelity data. Data fusion combines the two datasets into one single database. The approach can also handle changes in aircraft geometry. Once constructed, the look-up tables can be used in real-time to fly the aircraft through the database. To demonstrate the capabilities of the framework presented, five test cases are considered. These include a transonic cruiser concept design, an unconventional configuration, two passenger jet aircraft, and a jet trainer aircraft. Investigations into the areas of flight handling qualities, stability and control characteristics and manoeuvring aircraft are made. To assess the accuracy of the simulations, numerical results are also compared with wind tunnel and flight test data.
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.
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.
Structural Verification and Modeling of a Tension Cone Inflatable Aerodynamic Decelerator
NASA Technical Reports Server (NTRS)
Tanner, Christopher L.; Cruz, Juan R.; Braun, Robert D.
2010-01-01
Verification analyses were conducted on membrane structures pertaining to a tension cone inflatable aerodynamic decelerator using the analysis code LS-DYNA. The responses of three structures - a cylinder, torus, and tension shell - were compared against linear theory for various loading cases. Stress distribution, buckling behavior, and wrinkling behavior were investigated. In general, agreement between theory and LS-DYNA was very good for all cases investigated. These verification cases exposed the important effects of using a linear elastic liner in membrane structures under compression. Finally, a tension cone wind tunnel test article is modeled in LS-DYNA for which preliminary results are presented. Unlike data from supersonic wind tunnel testing, the segmented tension shell and torus experienced oscillatory behavior when subjected to a steady aerodynamic pressure distribution. This work is presented as a work in progress towards development of a fluid-structures interaction mechanism to investigate aeroelastic behavior of inflatable aerodynamic decelerators.
NASA Technical Reports Server (NTRS)
Batina, John T.
1990-01-01
Improved algorithms for the solution of the time-dependent Euler equations are presented for unsteady aerodynamic analysis involving unstructured dynamic meshes. The improvements have been developed recently to the spatial and temporal discretizations used by unstructured grid flow solvers. The spatial discretization involves a flux-split approach which is naturally dissipative and captures shock waves sharply with at most one grid point within the shock structure. The temporal discretization involves an implicit time-integration shceme using a Gauss-Seidel relaxation procedure which is computationally efficient for either steady or unsteady flow problems. For example, very large time steps may be used for rapid convergence to steady state, and the step size for unsteady cases may be selected for temporal accuracy rather than for numerical stability. Steady and unsteady flow results are presented for the NACA 0012 airfoil to demonstrate applications of the new Euler solvers. The unsteady results were obtained for the airfoil pitching harmonically about the quarter chord. The resulting instantaneous pressure distributions and lift and moment coefficients during a cycle of motion compare well with experimental data. The paper presents a description of the Euler solvers along with results and comparisons which assess the capability.
NASA Technical Reports Server (NTRS)
Batina, John T.
1990-01-01
Improved algorithm for the solution of the time-dependent Euler equations are presented for unsteady aerodynamic analysis involving unstructured dynamic meshes. The improvements were developed recently to the spatial and temporal discretizations used by unstructured grid flow solvers. The spatial discretization involves a flux-split approach which is naturally dissipative and captures shock waves sharply with at most one grid point within the shock structure. The temporal discretization involves an implicit time-integration scheme using a Gauss-Seidel relaxation procedure which is computationally efficient for either steady or unsteady flow problems. For example, very large time steps may be used for rapid convergence to steady state, and the step size for unsteady cases may be selected for temporal accuracy rather than for numerical stability. Steady and unsteady flow results are presented for the NACA 0012 airfoil to demonstrate applications of the new Euler solvers. The unsteady results were obtained for the airfoil pitching harmonically about the quarter chord. The resulting instantaneous pressure distributions and lift and moment coefficients during a cycle of motion compare well with experimental data. A description of the Euler solvers is presented along with results and comparisons which assess the capability.
Aerodynamic Control of a Dynamically Pitching Airfoil using Transitory Pulsed Actuation
NASA Astrophysics Data System (ADS)
Tan, Yuehan; Crittenden, Thomas; Glezer, Ari
2015-11-01
Transitory control and regulation of trapped vorticity concentrations are exploited for control of the aerodynamic loads on an airfoil that is dynamically pitching beyond the dynamic stall margin in wind tunnel experiments. Actuation is effected using a spanwise array of integrated miniature chemical (combustion based) high impulse actuators that are triggered intermittently relative to the airfoil's motion on characteristic time scales that are an order of magnitude shorter than the airfoil's convective time scale. The effects of the actuation on the aerodynamic characteristics of the airfoil are assessed using time-dependent measurements of the lift force and pitching moment coupled with time-resolved particle image velocimetry that is acquired phased-locked to the motion of the airfoil. The aerodynamic loading can be significantly altered by a number of actuation programs using multiple actuation bursts during the pitch cycle. While actuation during the upstroke primarily affects the formation, evolution, and advection of the dynamic stall vortex, actuation during the downstroke accelerates flow attachment. Superposition of such actuation programs leads to enhancement of cycle lift and pitch stability, and reduced cycle hysteresis.
NASA/Army Rotorcraft Technology. Volume 1: Aerodynamics, and Dynamics and Aeroelasticity
NASA Technical Reports Server (NTRS)
1988-01-01
The Conference Proceedings is a compilation of over 30 technical papers presented at this milestone event which reported on the advances in rotorcraft technical knowledge resulting from NASA, Army, and industry rotorcraft research programs over the last 5 to 10 years. The Conference brought together over 230 government, industry, and allied nation conferees to exchange technical information and hear invited technical papers by prominent NASA, Army, and industry researchers covering technology topics which included: aerodynamics, dynamics and elasticity, propulsion and drive systems, flight dynamics and control, acoustics, systems integration, and research aircraft.
Not Available
1993-01-01
In this article two integral computational fluid dynamics methods for steady-state and transient vehicle aerodynamic simulations are described using a Chevrolet Corvette ZR-1 surface panel model. In the last decade, road-vehicle aerodynamics have become an important design consideration. Originally, the design of low-drag shapes was given high priority due to worldwide fuel shortages that occurred in the mid-seventies. More recently, there has been increased interest in the role aerodynamics play in vehicle stability and passenger safety. Consequently, transient aerodynamics and the aerodynamics of vehicle in yaw have become important issues at the design stage. While there has been tremendous progress in Navier-Stokes methodology in the last few years, the physics of bluff-body aerodynamics are still very difficult to model correctly. Moreover, the computational effort to perform Navier-Stokes simulations from the geometric stage to complete flow solutions requires much computer time and impacts the design cycle time. In the short run, therefore, simpler methods must be used for such complicated problems. Here, two methods are described for the simulation of steady-state and transient vehicle aerodynamics.
Model-based fault detection and identification with online aerodynamic model structure selection
NASA Astrophysics Data System (ADS)
Lombaerts, T.
2013-12-01
This publication describes a recursive algorithm for the approximation of time-varying nonlinear aerodynamic models by means of a joint adaptive selection of the model structure and parameter estimation. This procedure is called adaptive recursive orthogonal least squares (AROLS) and is an extension and modification of the previously developed ROLS procedure. This algorithm is particularly useful for model-based fault detection and identification (FDI) of aerospace systems. After the failure, a completely new aerodynamic model can be elaborated recursively with respect to structure as well as parameter values. The performance of the identification algorithm is demonstrated on a simulation data set.
NASA Astrophysics Data System (ADS)
Sarychev, V. A.; Gutnik, S. A.
2015-11-01
The rotational dynamics of a satellite moving over a circular orbit under an effect of gravitational and aerodynamic torques is investigated. A method is proposed for determining all equilibrium positions (equilibrium orientations) of a satellite in an orbital coordinate system with given values of an aerodynamic torque vector and principal central moments of inertia; the conditions of their existence are obtained, depending on four dimensionless parameters of the problem. Bifurcation values of parameters are found for which the number of equilibrium orientations changes. The numerical analysis of the evolution of regions of existence of various numbers of equilibrium orientations in the space of dimensionless parameters is carried out. The relationship between the obtained regions of existence and the regions of existence of equilibrium orientations of an axisymmetric satellite is considered. It is shown that the number of equilibrium positions of a satellite does not exceed 24 and cannot be less than 8, in the general case.
A study on the dynamic characteristics of rocket structure
NASA Astrophysics Data System (ADS)
Kim, K. O.; Lee, J. M.; Kim, J. H.; Kim, S. J.
The dynamic characteristics of a rocket structure are studied in various aspects. Modeling of the structure used by the finite element method is performed, and analysis of stress under various loading condition is carried out. In particular, stresses and deflections are investigated for the structure subjected to internal pressure, thermal load, and aerodynamic forces during flight. Natural frequencies and mode shapes are also calculated.
Simplified Aerodynamic and Structural Modeling for Oblique All-Wing Aircraft. Phase 2: Structures
NASA Technical Reports Server (NTRS)
Kroo, Ilan (Principal Investigator)
1994-01-01
Any aircraft preliminary design study requires a structural model of the proposed configuration. The model must be capable of estimating the structural weight of a given configuration, and of predicting the deflections which will result from foreseen flight and ground loads. The present work develops such a model for the proposed Oblique All Wing airplane. The model is based on preliminary structural work done by Jack Williams and Peter Rudolph at Mdng, and is encoded in a FORTRAN program. As a stand-alone application, the program can calculate the weight CG location, and several types of structural deflections; used in conjunction with an aerodynamics model, the program can be used for mission analysis or sizing studies.
Dynamic interactions between hypersonic vehicle aerodynamics and propulsion system performance
NASA Technical Reports Server (NTRS)
Flandro, G. A.; Roach, R. L.; Buschek, H.
1992-01-01
Described here is the development of a flexible simulation model for scramjet hypersonic propulsion systems. The primary goal is determination of sensitivity of the thrust vector and other system parameters to angle of attack changes of the vehicle. Such information is crucial in design and analysis of control system performance for hypersonic vehicles. The code is also intended to be a key element in carrying out dynamic interaction studies involving the influence of vehicle vibrations on propulsion system/control system coupling and flight stability. Simple models are employed to represent the various processes comprising the propulsion system. A method of characteristics (MOC) approach is used to solve the forebody and external nozzle flow fields. This results in a very fast computational algorithm capable of carrying out the vast number of simulation computations needed in guidance, stability, and control studies. The three-dimensional fore- and aft body (nozzle) geometry is characterized by the centerline profiles as represented by a series of coordinate points and body cross-section curvature. The engine module geometry is represented by an adjustable vertical grid to accommodate variations of the field parameters throughout the inlet and combustor. The scramjet inlet is modeled as a two-dimensional supersonic flow containing adjustable sidewall wedges and multiple fuel injection struts. The inlet geometry including the sidewall wedge angles, the number of injection struts, their sweepback relative to the vehicle reference line, and strut cross-section are user selectable. Combustion is currently represented by a Rayleigh line calculation including corrections for variable gas properties; improved models are being developed for this important element of the propulsion flow field. The program generates (1) variation of thrust magnitude and direction with angle of attack, (2) pitching moment and line of action of the thrust vector, (3) pressure and temperature
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
NASA Technical Reports Server (NTRS)
Murch, Austin M.; Foster, John V.
2007-01-01
A simulation study was conducted to investigate aerodynamic modeling methods for prediction of post-stall flight dynamics of large transport airplanes. The research approach involved integrating dynamic wind tunnel data from rotary balance and forced oscillation testing with static wind tunnel data to predict aerodynamic forces and moments during highly dynamic departure and spin motions. Several state-of-the-art aerodynamic modeling methods were evaluated and predicted flight dynamics using these various approaches were compared. Results showed the different modeling methods had varying effects on the predicted flight dynamics and the differences were most significant during uncoordinated maneuvers. Preliminary wind tunnel validation data indicated the potential of the various methods for predicting steady spin motions.
NASA Technical Reports Server (NTRS)
Mennell, R. C.
1973-01-01
Experimental aerodynamic investigations were conducted on an 0.0405 scale representation of the Rockwell -89A Light Weight Space Shuttle Orbiter. The test purpose was to obtain pressure loads data in the presence of the ground for orbiter structural strength analysis. Aerodynamic force data was also recorded to allow correlation with all pressure loads information. Angles of attack from minus 3 deg to 18 deg and angles of sideslip of 0 deg, plus or minus 50 deg, and plus or minus 10 deg were tested in the presence of the NAAL ground plane. Static pressure bugs were used to obtain a pressure loads survey of the basic configuration, elevon deflections of 5 deg, 10 deg, 15 deg, and minus 20 deg and a rudder deflection of minus 15 deg, at a tunnel dynamic pressure of 40 psi. The test procedure was to locate a maximum of 30 static pressure bugs on the model surface at various locations calculated to prevent aerodynamic and physical interference. Then by various combinations of location the pressure bugs output was to define a complete pressure survey for the fuselages, wing, vertical tail, and main landing gear door.
Unsteady Aerodynamic and Dynamic Analysis of the Meridian UAS in a Rolling-Yawing Motion
NASA Astrophysics Data System (ADS)
Lykins, Ryan
The nonlinear and unsteady aerodynamic effects of operating the Meridian unmanned aerial system (UAS) in crosswinds and at high angular rates is investigated in this work. The Meridian UAS is a large autonomous aircraft, with a V-tail configuration, operated in Polar Regions for the purpose of remotely measuring ice sheet thickness. The inherent nonlinear coupling produced by the V-tail, along with the strong atmospheric disturbances, has made classical model identification methods inadequate for proper model development. As such, a powerful tool known as Fuzzy Logic Modeling (FLM) was implemented to generate time-dependent, nonlinear, and unsteady aerodynamic models using flight test data collected in Greenland in 2011. Prior to performing FLM, compatibility analysis is performed on the data, for the purpose of systematic bias removal and airflow angle estimation. As one of the advantages of FLM is the ability to model unsteady aerodynamics, the reduced frequency for both longitudinal and lateral-directional motions is determined from the unbiased data, using Theodorsen's theory of unsteadiness, which serves as an input parameter in modeling. These models have been used in this work to identify pilot induced oscillations, unsteady coupling motions, unsteady motion due to the slipstream and cross wind interaction, and destabilizing motions and orientations. This work also assesses the accuracy of preliminary aircraft dynamic models developed using engineering level software, and addresses the autopilot Extended Kalman Filter state estimations.
NASA Technical Reports Server (NTRS)
Hui, W. H.
1985-01-01
Bifurcation theory is used to analyze the nonlinear dynamic stability characteristics of an aircraft subject to single-degree-of-freedom. The requisite moment of the aerodynamic forces in the equations of motion is shown to be representable in a form equivalent to the response to finite amplitude oscillations. It is shown how this information can be deduced from the case of infinitesimal-amplitude oscillations. The bifurcation theory analysis reveals that when the bifurcation parameter is increased beyond a critical value at which the aerodynamic damping vanishes, new solutions representing finite amplitude periodic motions bifurcate from the previously stable steady motion. The sign of a simple criterion, cast in terms of aerodynamic properties, determines whether the bifurcating solutions are stable or unstable. For the pitching motion of flat-plate airfoils flying at supersonic/hypersonic speed and for oscillation of flaps at transonic speed, the bifurcation is subcritical, implying either the exchanges of stability between steady and periodic motion are accompanied by hysteresis phenomena, or that potentially large aperiodic departures from steady motion may develop.
NASA Technical Reports Server (NTRS)
Campbell, John P; Mckinney, Marion O
1952-01-01
A summary of methods for making dynamic lateral stability and response calculations and for estimating the aerodynamic stability derivatives required for use in these calculations is presented. The processes of performing calculations of the time histories of lateral motions, of the period and damping of these motions, and of the lateral stability boundaries are presented as a series of simple straightforward steps. Existing methods for estimating the stability derivatives are summarized and, in some cases, simple new empirical formulas are presented. Detailed estimation methods are presented for low-subsonic-speed conditions but only a brief discussion and a list of references are given for transonic and supersonic speed conditions.
Evaluation of Ares-I Control System Robustness to Uncertain Aerodynamics and Flex Dynamics
NASA Technical Reports Server (NTRS)
Jang, Jiann-Woei; VanTassel, Chris; Bedrossian, Nazareth; Hall, Charles; Spanos, Pol
2008-01-01
This paper discusses the application of robust control theory to evaluate robustness of the Ares-I control systems. Three techniques for estimating upper and lower bounds of uncertain parameters which yield stable closed-loop response are used here: (1) Monte Carlo analysis, (2) mu analysis, and (3) characteristic frequency response analysis. All three methods are used to evaluate stability envelopes of the Ares-I control systems with uncertain aerodynamics and flex dynamics. The results show that characteristic frequency response analysis is the most effective of these methods for assessing robustness.
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.
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.
Wind Turbine Blade Design System - Aerodynamic and Structural Analysis
NASA Astrophysics Data System (ADS)
Dey, Soumitr
2011-12-01
The ever increasing need for energy and the depletion of non-renewable energy resources has led to more advancement in the "Green Energy" field, including wind energy. An improvement in performance of a Wind Turbine will enhance its economic viability, which can be achieved by better aerodynamic designs. In the present study, a design system that has been under development for gas turbine turbomachinery has been modified for designing wind turbine blades. This is a very different approach for wind turbine blade design, but will allow it to benefit from the features inherent in the geometry flexibility and broad design space of the presented system. It starts with key overall design parameters and a low-fidelity model that is used to create the initial geometry parameters. The low-fidelity system includes the axisymmetric solver with loss models, T-Axi (Turbomachinery-AXIsymmetric), MISES blade-to-blade solver and 2D wing analysis code XFLR5. The geometry parameters are used to define sections along the span of the blade and connected to the CAD model of the wind turbine blade through CAPRI (Computational Analysis PRogramming Interface), a CAD neutral API that facilitates the use of parametric geometry definition with CAD. Either the sections or the CAD geometry is then available for CFD and Finite Element Analysis. The GE 1.5sle MW wind turbine and NERL NASA Phase VI wind turbine have been used as test cases. Details of the design system application are described, and the resulting wind turbine geometry and conditions are compared to the published results of the GE and NREL wind turbines. A 2D wing analysis code XFLR5, is used for to compare results from 2D analysis to blade-to-blade analysis and the 3D CFD analysis. This kind of comparison concludes that, from hub to 25% of the span blade to blade effects or the cascade effect has to be considered, from 25% to 75%, the blade acts as a 2d wing and from 75% to the tip 3D and tip effects have to be taken into account
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.
NASA Technical Reports Server (NTRS)
Lyle, Karen H.
2014-01-01
Acceptance of new spacecraft structural architectures and concepts requires validated design methods to minimize the expense involved with technology validation via flighttesting. This paper explores the implementation of probabilistic methods in the sensitivity analysis of the structural response of a Hypersonic Inflatable Aerodynamic Decelerator (HIAD). HIAD architectures are attractive for spacecraft deceleration because they are lightweight, store compactly, and utilize the atmosphere to decelerate a spacecraft during re-entry. However, designers are hesitant to include these inflatable approaches for large payloads or spacecraft because of the lack of flight validation. In the example presented here, the structural parameters of an existing HIAD model have been varied to illustrate the design approach utilizing uncertainty-based methods. Surrogate models have been used to reduce computational expense several orders of magnitude. The suitability of the design is based on assessing variation in the resulting cone angle. The acceptable cone angle variation would rely on the aerodynamic requirements.
Integrated aerodynamic-structural design of a forward-swept transport wing
NASA Technical Reports Server (NTRS)
Haftka, Raphael T.; Grossman, Bernard; Kao, Pi-Jen; Polen, David M.; Sobieszczanski-Sobieski, Jaroslaw
1989-01-01
The introduction of composite materials is having a profound effect on aircraft design. Since these materials permit the designer to tailor material properties to improve structural, aerodynamic and acoustic performance, they require an integrated multidisciplinary design process. Futhermore, because of the complexity of the design process, numerical optimization methods are required. The utilization of integrated multidisciplinary design procedures for improving aircraft design is not currently feasible because of software coordination problems and the enormous computational burden. Even with the expected rapid growth of supercomputers and parallel architectures, these tasks will not be practical without the development of efficient methods for cross-disciplinary sensitivities and efficient optimization procedures. The present research is part of an on-going effort which is focused on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration. A sequence of integrated wing design procedures has been developed in order to investigate various aspects of the design process.
Towards an Experimental Investigation of Wind Turbine Aerodynamics at Full Dynamic Similarity
NASA Astrophysics Data System (ADS)
Miller, Mark A.; Hultmark, Marcus
2014-11-01
As horizontal axis wind turbines continue to increase in size (with the largest approaching 200 meters in diameter) it becomes progressively more difficult to test new designs without high computational power or extensive experimental effort using conventional tools. Therefore, compromises are often made between the important non-dimensional parameters (Reynolds number and Strouhal number, or tip speed ratio) so that reasonable engineering insight can be gained. Using the unique facilities available at Princeton University, we aim to match both non-dimensional parameters and thus achieve full dynamic similarity at realistic conditions. This is accomplished by using the High Reynolds number Test Facility (or HRTF), which is a high pressure (200 atmospheres) wind tunnel. We present the design, manufacture, and testing of an apparatus suited to the unique environment of a high-pressure facility as well as future plans for investigating the underlying aerodynamics of large-scale wind turbines.
Defining Dynamic Route Structure
NASA Technical Reports Server (NTRS)
Zelinski, Shannon; Jastrzebski, Michael
2011-01-01
This poster describes a method for defining route structure from flight tracks. Dynamically generated route structures could be useful in guiding dynamic airspace configuration and helping controllers retain situational awareness under dynamically changing traffic conditions. Individual merge and diverge intersections between pairs of flights are identified, clustered, and grouped into nodes of a route structure network. Links are placed between nodes to represent major traffic flows. A parametric analysis determined the algorithm input parameters producing route structures of current day flight plans that are closest to todays airway structure. These parameters are then used to define and analyze the dynamic route structure over the course of a day for current day flight paths. Route structures are also compared between current day flight paths and more user preferred paths such as great circle and weather avoidance routing.
NASA Technical Reports Server (NTRS)
Callahan, Cynthia B.; Bassett, Duane E.
1988-01-01
A model of the AH-64A helicopter was generated in a Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD) in an effort to validate its analytical capabilities for modeling a current advanced Army helicopter. The initial phase of the effort involved the generation of CAMRAD input files necessary for the complete aerodynamic, structural, and dynamic definition of the production AH-64A helicopter. The input files were checked by making comparisons of CAMRAD full helicopter trim and main rotor blade natural frequency predictions with those of full helicopter trim program, Blade Element Trim (BETRIM), and dynamic analysis code, Dynamic Analysis Research Tool (DART), respectively. The main thrust concerned the application of the AH-64A CAMRAD model thus developed and verified for main rotor blade structural loads predictions and comparison with DART analytical results. The investigation provided insight not only into the usefulness of CAMRAD for the AH-64A performance and dynamics prediction, but also into the limitations of the program for modeling advanced rotor and fuselage systems. The model development effort is discussed, the results of the CAMRAD correlation studies presented, and some general conclusions are offered on the applicability of CAMRAD for rotor aeroelastic loads prediction for current and future rotorcraft configurations.
Effect of Trailing Edge Shape on the Unsteady Aerodynamics of Reverse Flow Dynamic Stall
NASA Astrophysics Data System (ADS)
Lind, Andrew; Jones, Anya
2015-11-01
This work considers dynamic stall in reverse flow, where flow travels over an oscillating airfoil from the geometric trailing edge towards the leading edge. An airfoil with a sharp geometric trailing edge causes early formation of a primary dynamic stall vortex since the sharp edge acts as the aerodynamic leading edge in reverse flow. The present work experimentally examines the potential merits of using an airfoil with a blunt geometric trailing edge to delay flow separation and dynamic stall vortex formation while undergoing oscillations in reverse flow. Time-resolved and phase-averaged flow fields and pressure distributions are compared for airfoils with different trailing edge shapes. Specifically, the evolution of unsteady flow features such as primary, secondary, and trailing edge vortices is examined. The influence of these flow features on the unsteady pressure distributions and integrated unsteady airloads provide insight on the torsional loading of rotor blades as they oscillate in reverse flow. The airfoil with a blunt trailing edge delays reverse flow dynamic stall, but this leads to greater downward-acting lift and pitching moment. These results are fundamental to alleviating vibrations of high-speed helicopters, where much of the rotor operates in reverse flow.
NASA Technical Reports Server (NTRS)
Sim, B. W.; Lim, J. W.
2007-01-01
Predictions of blade-vortex interaction (BVI) noise, using blade airloads obtained from a coupled aerodynamic and structural methodology, are presented. This methodology uses an iterative, loosely-coupled trim strategy to cycle information between the OVERFLOW-2 (CFD) and CAMRAD-II (CSD) codes. Results are compared to the HART-II baseline, minimum noise and minimum vibration conditions. It is shown that this CFD/CSD state-of-the-art approach is able to capture blade airload and noise radiation characteristics associated with BVI. With the exception of the HART-II minimum noise condition, predicted advancing and retreating side BVI for the baseline and minimum vibration conditions agrees favorably with measured data. Although the BVI airloads and noise amplitudes are generally under-predicted, this CFD/CSD methodology provides an overall noteworthy improvement over the lifting line aerodynamics and free-wake models typically used in CSD comprehensive analysis codes.
Impact of Aerodynamics and Structures Technology on Heavy Lift Tiltrotors
NASA Technical Reports Server (NTRS)
Acree, C. W., Jr.
2006-01-01
Rotor performance and aeroelastic stability are presented for a 124,000-lb Large Civil Tilt Rotor (LCTR) design. It was designed to carry 120 passengers for 1200 nm, with performance of 350 knots at 30,000 ft altitude. Design features include a low-mounted wing and hingeless rotors, with a very low cruise tip speed of 350 ft/sec. The rotor and wing design processes are described, including rotor optimization methods and wing/rotor aeroelastic stability analyses. New rotor airfoils were designed specifically for the LCTR; the resulting performance improvements are compared to current technology airfoils. Twist, taper and precone optimization are presented, along with the effects of blade flexibility on performance. A new wing airfoil was designed and a composite structure was developed to meet the wing load requirements for certification. Predictions of aeroelastic stability are presented for the optimized rotor and wing, along with summaries of the effects of rotor design parameters on stability.
NASA Astrophysics Data System (ADS)
Etzel, P. B.; Martin, R.; Romeo, R.; Fesen, R.; Hale, R.; Taghavi, R.; Anthony-Twarog, B. J.; Shawl, S. J.; Twarog, B. A.
2004-12-01
The focus of ULTRA (see poster by Twarog et al.) is a three-year plan to develop and test ultralightweight technology for research applications in astronomy. The goal is to demonstrate that a viable alternative exists to traditional glass-mirror technology by designing, fabricating, and testing a research telescope prototype comprising fiber reinforced plastic (CFRP) materials. To date, several mirror designs have been tested. The main goal in the first year has been to develop a 0.4m diameter mirror and OTA that serve as prototypes for the 1m telescope design. Mirrors of 0.4m diameter have been successfully fabricated which yield diffraction limited images. This poster will include a display of the complete OTA (including optics), optics test results, and astronomical images taken with prototype mirrors. Finite element analysis has been used to evaluate the OTA and mirror designs. Preliminary design details were incorporated in a knowledge-based system. Adaptive Modeling Language (AML), an object oriented programming language developed by Technosoft, Inc., was used to develop a parameterized geometric model of the preliminary design. The system can generate mirrors with radials/circumferentials, tube core substructures, as well as modeling the support structure. Computational fluid dynamics analyses were performed for sweep, inclination and ambient wind speed. Finite element analyses were performed for core density and arrangement, skin thickness, back-surface curvature, spider configuration and arrangement of the OTA, while the loading conditions considered thus far are thermal, inertial, and aerodynamic pressure loads. Experimental tests, including ultrasonic nondestructive evaluations, infrared imaging, modal testing, and wind tunnel tests, have been performed on the first prototype mirror, with the primary goal of validating analytical models and identifying potential manufacturing induced variations to be expected among "like" mirrors. Support of this work by
Aeroelasticity of Axially Loaded Aerodynamic Structures for Truss-Braced Wing Aircraft
NASA Technical Reports Server (NTRS)
Nguyen, Nhan; Ting, Eric; Lebofsky, Sonia
2015-01-01
This paper presents an aeroelastic finite-element formulation for axially loaded aerodynamic structures. The presence of axial loading causes the bending and torsional sitffnesses to change. For aircraft with axially loaded structures such as the truss-braced wing aircraft, the aeroelastic behaviors of such structures are nonlinear and depend on the aerodynamic loading exerted on these structures. Under axial strain, a tensile force is created which can influence the stiffness of the overall aircraft structure. This tension stiffening is a geometric nonlinear effect that needs to be captured in aeroelastic analyses to better understand the behaviors of these types of aircraft structures. A frequency analysis of a rotating blade structure is performed to demonstrate the analytical method. A flutter analysis of a truss-braced wing aircraft is performed to analyze the effect of geometric nonlinear effect of tension stiffening on the flutter speed. The results show that the geometric nonlinear tension stiffening effect can have a significant impact on the flutter speed prediction. In general, increased wing loading results in an increase in the flutter speed. The study illustrates the importance of accounting for the geometric nonlinear tension stiffening effect in analyzing the truss-braced wing aircraft.
Skinner, Lawrie; Benmore, Chris J; Weber, Richard; Santodonato, Louis J; Tumber, Sonia; Neuefeind, Joerg C; Lazareva, Lena; Du, Jincheng; Parise, John B
2012-01-01
We have performed neutron diffraction isotopic substitution experiments on aerodynamically levitated droplets of CaSiO3, to directly extract intermediate and local structural information on the Ca environment. The results show a substantial broadening of the Ca-O peak in the pair distribution function of the melt compared to the glass, which comprises primarily of 6- and 7-fold coordinated Ca-polyhedra. The broadening can be explained by a re-distribution of Ca-O bond lengths, especially towards longer distances in the liquid. The first order neutron difference function provides a rigorous test of recent molecular dynamics simulations and supports the model of the presence of short chains or channels of edge shared Ca-octahedra in the liquid state. It is suggested that the polymerization of Ca-polyhedra is responsible for the fragile viscosity behavior of the melt and the glass forming ability in CaSiO3.
NASA Technical Reports Server (NTRS)
Heffernan, Ruth M.; Gaubert, Michel
1986-01-01
A flight test program was conducted to obtain data from an upgraded Gazelle helicopter with an advanced geometry, three bladed rotor. Data were acquired on upper and lower surface chordwise blade pressure, blade bending and torsion moments, and fuselage structural loads. Results are presented from 16 individual flight conditions, including level flights ranging from 10 to 77 m/sec at 50 to 3000 m altitude, turning flights up to 2.0 g, and autorotation. Rotor aerodynamic data include information from 51 pressure transducers distributed chordwise at 75, 88, and 97% radial stations. Individual tranducer pressure coefficients and airfoil section lift and pitching moment coefficients are presented, as are steady state flight condition parameters and time dependence rotor loads. All dynamic data are presented as harmonic analysis coefficients.
Microemulsions: Structure and dynamics
Friberg, S.E.; Bothorel, P.
1987-01-01
This book covers the state-of-the-art in stability, structure, applications, and dynamics representation of microemulsion systems. An international group of reviewers discuss the introductory investigations into macroemulsions and interfacial free energy, the derivation of the microemulsion systems from micellar solutions, and the correlation between structure and dynamics. Future developments in this area are also considered. The book presents following: contents; phase diagrams and pseudophase assumption; phase diagram and critical behavior of a quaternary microemulsion system; non-aqueous microemulsions; nonionics; molecular diffusion in microemulsions; dynamics of microemulsions; low interfacial tensions in microemulsion systems; oil recovery and microemulsions.
Wind Turbine Structural Dynamics
NASA Technical Reports Server (NTRS)
Miller, D. R. (Editor)
1978-01-01
A workshop on wind turbine structural dynamics was held to review and document current United States work on the dynamic behavior of large wind turbines, primarily of the horizontal-axis type, and to identify and discuss other wind turbine configurations that may have lower cost and weight. Information was exchanged on the following topics: (1) Methods for calculating dynamic loads; (2) Aeroelasticity stability (3) Wind loads, both steady and transient; (4) Critical design conditions; (5) Drive train dynamics; and (6) Behavior of operating wind turbines.
New directions in fluid dynamics: non-equilibrium aerodynamic and microsystem flows.
Reese, Jason M; Gallis, Michael A; Lockerby, Duncan A
2003-12-15
Fluid flows that do not have local equilibrium are characteristic of some of the new frontiers in engineering and technology, for example, high-speed high-altitude aerodynamics and the development of micrometre-sized fluid pumps, turbines and other devices. However, this area of fluid dynamics is poorly understood from both the experimental and simulation perspectives, which hampers the progress of these technologies. This paper reviews some of the recent developments in experimental techniques and modelling methods for non-equilibrium gas flows, examining their advantages and drawbacks. We also present new results from our computational investigations into both hypersonic and microsystem flows using two distinct numerical methodologies: the direct simulation Monte Carlo method and extended hydrodynamics. While the direct simulation approach produces excellent results and is used widely, extended hydrodynamics is not as well developed but is a promising candidate for future more complex simulations. Finally, we discuss some of the other situations where these simulation methods could be usefully applied, and look to the future of numerical tools for non-equilibrium flows. PMID:14667308
Uncertainty-Based Approach for Dynamic Aerodynamic Data Acquisition and Analysis
NASA Technical Reports Server (NTRS)
Heim, Eugene H. D.; Bandon, Jay M.
2004-01-01
Development of improved modeling methods to provide increased fidelity of flight predictions for aircraft motions during flight in flow regimes with large nonlinearities requires improvements in test techniques for measuring and characterizing wind tunnel data. This paper presents a method for providing a measure of data integrity for static and forced oscillation test techniques. Data integrity is particularly important when attempting to accurately model and predict flight of today s high performance aircraft which are operating in expanded flight envelopes, often maneuvering at high angular rates at high angles-of-attack, even above maximum lift. Current aerodynamic models are inadequate in predicting flight characteristics in the expanded envelope, such as rapid aircraft departures and other unusual motions. Present wind tunnel test methods do not factor changes of flow physics into data acquisition schemes, so in many cases data are obtained over more iterations than required, or insufficient data may be obtained to determine a valid estimate with statistical significance. Additionally, forced oscillation test techniques, one of the primary tools used to develop dynamic models, do not currently provide estimates of the uncertainty of the results during an oscillation cycle. A method to optimize the required number of forced oscillation cycles based on decay of uncertainty gradients and balance tolerances is also presented.
NASA Astrophysics Data System (ADS)
Polanský, Jiří; Kalmár, László; Gášpár, Roman
2013-12-01
The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteristics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant contains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length [1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were performed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine characteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also partially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calculation stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition.
In-situ X-ray structure measurements on aerodynamically levitated high temperature liquids
Weber, Richard; Benmore, Christopher; Mei Qiang; Wilding, Martin
2009-01-29
High energy, high flux X-ray sources enable new measurements of liquid and amorphous materials in extreme conditions. Aerodynamic levitation in combination with laser beam heating can be used to access high purity and non-equilibrium liquids at temperatures up to 3000 K. In this work, a small aerodynamic levitator was integrated with high energy beamline 11 ID-C at the Advanced Photon Source. Scattered X-rays were detected with a Mar345 image plate. The experiments investigated a series of binary in the CaO-Al{sub 2}O{sub 3}, MgO-SiO{sub 2}, SiO{sub 2}-Al{sub 2}O{sub 3} metal oxide compositions and pure SiO{sub 2}. The results show that the liquids exhibit large changes in structure when the predominant network former is diluted. Measurements on glasses with the same compositions as the liquids suggest that significant structural rearrangement consistent with a fragile-strong transition occurs in these reluctant glass forming liquids as they vitrify.
NASA Technical Reports Server (NTRS)
Reinmann, J. J.
1991-01-01
The purpose of the meeting on Effects of Adverse Weather on Aerodynamics was to provide an update of the stae-of-the-art with respect to the prediction, simulation, and measurement of the effects of icing, anti-icing fluids, and various precipitation on the aerodynamic characteristics of flight vehicles. Sessions were devoted to introductory and survey papers and icing certification issues, to analytical and experimental simulation of ice frost contamination and its effects of aerodynamics, and to the effects of heavy rain and deicing/anti-icing fluids.
Modeling aerodynamic discontinuities and the onset of chaos in flight dynamical systems
NASA Technical Reports Server (NTRS)
Tobak, M.; Chapman, G. T.; Uenal, A.
1986-01-01
Various representations of the aerodynamic contribution to the aircraft's equation of motion are shown to be compatible within the common assumption of their Frechet differentiability. Three forms of invalidating Frechet differentiality are identified, and the mathematical model is amended to accommodate their occurrence. Some of the ways in which chaotic behavior may emerge are discussed, first at the level of the aerodynamic contribution to the equation of motion, and then at the level of the equations of motion themselves.
Unsteady Aerodynamic Testing Using the Dynamic Plunge Pitch and Roll Model Mount
NASA Technical Reports Server (NTRS)
Lutze, Frederick H.; Fan, Yigang
1999-01-01
A final report on the DyPPiR tests that were run are presented. Essentially it consists of two parts, a description of the data reduction techniques and the results. The data reduction techniques include three methods that were considered: 1) signal processing of wind on - wind off data; 2) using wind on data in conjunction with accelerometer measurements; and 3) using a dynamic model of the sting to predict the sting oscillations and determining the aerodynamic inputs using an optimization process. After trying all three, we ended up using method 1, mainly because of its simplicity and our confidence in its accuracy. The results section consists of time history plots of the input variables (angle of attack, roll angle, and/or plunge position) and the corresponding time histories of the output variables, C(sub L), C(sub D), C(sub m), C(sub l), C(sub m), C(sub n). Also included are some phase plots of one or more of the output variable vs. an input variable. Typically of interest are pitch moment coefficient vs. angle of attack for an oscillatory motion where the hysteresis loops can be observed. These plots are useful to determine the "more interesting" cases. Samples of the data as it appears on the disk are presented at the end of the report. The last maneuver, a rolling pull up, is indicative of the unique capabilities of the DyPPiR, allowing combinations of motions to be exercised at the same time.
Modeling Powered Aerodynamics for the Orion Launch Abort Vehicle Aerodynamic Database
NASA Technical Reports Server (NTRS)
Chan, David T.; Walker, Eric L.; Robinson, Philip E.; Wilson, Thomas M.
2011-01-01
Modeling the aerodynamics of the Orion Launch Abort Vehicle (LAV) has presented many technical challenges to the developers of the Orion aerodynamic database. During a launch abort event, the aerodynamic environment around the LAV is very complex as multiple solid rocket plumes interact with each other and the vehicle. It is further complicated by vehicle separation events such as between the LAV and the launch vehicle stack or between the launch abort tower and the crew module. The aerodynamic database for the LAV was developed mainly from wind tunnel tests involving powered jet simulations of the rocket exhaust plumes, supported by computational fluid dynamic simulations. However, limitations in both methods have made it difficult to properly capture the aerodynamics of the LAV in experimental and numerical simulations. These limitations have also influenced decisions regarding the modeling and structure of the aerodynamic database for the LAV and led to compromises and creative solutions. Two database modeling approaches are presented in this paper (incremental aerodynamics and total aerodynamics), with examples showing strengths and weaknesses of each approach. In addition, the unique problems presented to the database developers by the large data space required for modeling a launch abort event illustrate the complexities of working with multi-dimensional data.
Feedback Linearized Aircraft Control Using Dynamic Cell Structure
NASA Technical Reports Server (NTRS)
Jorgensen, C. C.
1998-01-01
A Dynamic Cell Structure (DCS ) Neural Network was developed which learns a topology representing network (TRN) of F-15 aircraft aerodynamic stability and control derivatives. The network is combined with a feedback linearized tracking controller to produce a robust control architecture capable of handling multiple accident and off-nominal flight scenarios. This paper describes network and its performance for accident scenarios including differential stabilator lock, soft sensor failure, control, stability derivative variation, and turbulence.
NASA Technical Reports Server (NTRS)
Mei, Ren-Wei; Shyy, Wei; Yu, Da-Zhi; Luo, Li-Shi; Rudy, David (Technical Monitor)
2001-01-01
The lattice Boltzmann equation (LBE) is a kinetic formulation which offers an alternative computational method capable of solving fluid dynamics for various systems. Major advantages of the method are owing to the fact that the solution for the particle distribution functions is explicit, easy to implement, and the algorithm is natural to parallelize. In this final report, we summarize the works accomplished in the past three years. Since most works have been published, the technical details can be found in the literature. Brief summary will be provided in this report. In this project, a second-order accurate treatment of boundary condition in the LBE method is developed for a curved boundary and tested successfully in various 2-D and 3-D configurations. To evaluate the aerodynamic force on a body in the context of LBE method, several force evaluation schemes have been investigated. A simple momentum exchange method is shown to give reliable and accurate values for the force on a body in both 2-D and 3-D cases. Various 3-D LBE models have been assessed in terms of efficiency, accuracy, and robustness. In general, accurate 3-D results can be obtained using LBE methods. The 3-D 19-bit model is found to be the best one among the 15-bit, 19-bit, and 27-bit LBE models. To achieve desired grid resolution and to accommodate the far field boundary conditions in aerodynamics computations, a multi-block LBE method is developed by dividing the flow field into various blocks each having constant lattice spacing. Substantial contribution to the LBE method is also made through the development of a new, generalized lattice Boltzmann equation constructed in the moment space in order to improve the computational stability, detailed theoretical analysis on the stability, dispersion, and dissipation characteristics of the LBE method, and computational studies of high Reynolds number flows with singular gradients. Finally, a finite difference-based lattice Boltzmann method is
Dynamics and structure of stretched flames
Law, C.K.
1993-12-01
This program aims to gain fundamental understanding on the structure, geometry, and dynamics of laminar premixed flames, and relate these understanding to the practical issues of flame extinction and stabilization. The underlying fundamental interest here is the recent recognition that the response of premixed flames can be profoundly affected by flame stretch, as manifested by flow nonuniformity, flame curvature, and flame/flow unsteadiness. As such, many of the existing understanding on the behavior of premixed flames need to be qualitatively revised. The research program consists of three major thrusts: (1) detailed experimental and computational mapping of the structure of aerodynamically-strained planar flames, with emphasis on the effects of heat loss, nonequidiffusion, and finite residence time on the flame thickness, extent of incomplete reaction, and the state of extinction. (2) Analytical study of the geometry and dynamics of stretch-affected wrinkled flame sheets in simple configurations, as exemplified by the Bunsen flame and the spatially-periodic flame, with emphasis on the effects of nonlinear stretch, the phenomena of flame cusping, smoothing, and tip opening, and their implications on the structure and burning rate of turbulent flames. (3) Stabilization and blowoff of two-dimensional inverted premixed and stabilization and determining the criteria governing flame blowoff. The research is synergistically conducted through the use of laser-based diagnostics, computational simulation of the flame structure with detailed chemistry and transport, and mathematical analysis of the flame dynamics.
PREFACE: Aerodynamic sound Aerodynamic sound
NASA Astrophysics Data System (ADS)
Akishita, Sadao
2010-02-01
The modern theory of aerodynamic sound originates from Lighthill's two papers in 1952 and 1954, as is well known. I have heard that Lighthill was motivated in writing the papers by the jet-noise emitted by the newly commercialized jet-engined airplanes at that time. The technology of aerodynamic sound is destined for environmental problems. Therefore the theory should always be applied to newly emerged public nuisances. This issue of Fluid Dynamics Research (FDR) reflects problems of environmental sound in present Japanese technology. The Japanese community studying aerodynamic sound has held an annual symposium since 29 years ago when the late Professor S Kotake and Professor S Kaji of Teikyo University organized the symposium. Most of the Japanese authors in this issue are members of the annual symposium. I should note the contribution of the two professors cited above in establishing the Japanese community of aerodynamic sound research. It is my pleasure to present the publication in this issue of ten papers discussed at the annual symposium. I would like to express many thanks to the Editorial Board of FDR for giving us the chance to contribute these papers. We have a review paper by T Suzuki on the study of jet noise, which continues to be important nowadays, and is expected to reform the theoretical model of generating mechanisms. Professor M S Howe and R S McGowan contribute an analytical paper, a valuable study in today's fluid dynamics research. They apply hydrodynamics to solve the compressible flow generated in the vocal cords of the human body. Experimental study continues to be the main methodology in aerodynamic sound, and it is expected to explore new horizons. H Fujita's study on the Aeolian tone provides a new viewpoint on major, longstanding sound problems. The paper by M Nishimura and T Goto on textile fabrics describes new technology for the effective reduction of bluff-body noise. The paper by T Sueki et al also reports new technology for the
Numerical Aerodynamic Simulation
NASA Technical Reports Server (NTRS)
1989-01-01
An overview of historical and current numerical aerodynamic simulation (NAS) is given. The capabilities and goals of the Numerical Aerodynamic Simulation Facility are outlined. Emphasis is given to numerical flow visualization and its applications to structural analysis of aircraft and spacecraft bodies. The uses of NAS in computational chemistry, engine design, and galactic evolution are mentioned.
NASA Technical Reports Server (NTRS)
Woodrow Whitlow, Jr. (Editor); Todd, Emily N. (Editor)
1999-01-01
These proceedings represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft.
Cho, Jaeil; Miyazaki, Shin; Yeh, Pat J-F; Kim, Wonsik; Kanae, Shinjiro; Oki, Taikan
2012-03-01
Surface albedo (α) and aerodynamic roughness length (z(0)), which partition surface net radiation into energy fluxes, are critical land surface properties for biosphere-atmosphere interactions and climate variability. Previous studies suggested that canopy structure parameters influence both α and z(0); however, no field data have been reported to quantify their relationships. Here, we hypothesize that a functional relationship between α and z(0) exists for a vegetated surface, since both land surface parameters can be conceptually related to the characteristics of canopy structure. We test this hypothesis by using the observed data collected from 50 site-years of field measurements from sites worldwide covering various vegetated surfaces. On the basis of these data, a negative linear relationship between α and log(z(0)) was found, which is related to the canopy structural parameter. We believe that our finding is a big step toward the estimation of z(0) with high accuracy. This can be used, for example, in the parameterization of land properties and the observation of z(0) using satellite remote sensing. PMID:21562788
Integrating aerodynamics and structures in the minimum weight design of a supersonic transport wing
NASA Technical Reports Server (NTRS)
Barthelemy, Jean-Francois M.; Wrenn, Gregory A.; Dovi, Augustine R.; Coen, Peter G.; Hall, Laura E.
1992-01-01
An approach is presented for determining the minimum weight design of aircraft wing models which takes into consideration aerodynamics-structure coupling when calculating both zeroth order information needed for analysis and first order information needed for optimization. When performing sensitivity analysis, coupling is accounted for by using a generalized sensitivity formulation. The results presented show that the aeroelastic effects are calculated properly and noticeably reduce constraint approximation errors. However, for the particular example selected, the error introduced by ignoring aeroelastic effects are not sufficient to significantly affect the convergence of the optimization process. Trade studies are reported that consider different structural materials, internal spar layouts, and panel buckling lengths. For the formulation, model and materials used in this study, an advanced aluminum material produced the lightest design while satisfying the problem constraints. Also, shorter panel buckling lengths resulted in lower weights by permitting smaller panel thicknesses and generally, by unloading the wing skins and loading the spar caps. Finally, straight spars required slightly lower wing weights than angled spars.
Structural Testing of a 6m Hypersonic Inflatable Aerodynamic Decelerator System
NASA Technical Reports Server (NTRS)
Swanson, G. T.; Kazemba, C. D.; Johnson, R. K.; Hughes, S. J.; Calomino, A. M.
2015-01-01
NASA is developing low ballistic coefficient technologies to support the Nations long-term goal of landing humans on Mars. Current entry, decent, and landing technologies are not practical for this class of payloads due to geometric constraints dictated by current and future launch vehicle fairing limitations. Hypersonic Inflatable Aerodynamic Decelerators (HIADs) are being developed to circumvent this limitation and are now considered a leading technology to enable landing of heavy payloads on Mars. At the beginning of 2014, a 6m diameter HIAD inflatable structure with an integrated flexible thermal protection system (TPS) was subjected to a static load test series to verify its structural performance under flight-relevant loads. The inflatable structure was constructed into a 60 degree sphere-cone configuration using nine inflatable torus segments composed of fiber-reinforced thin films. The inflatable tori were joined together using adhesives and high-strength textile woven structural straps. These straps help distribute the load throughout the inflatable structure. The 6m flexible TPS was constructed using multiple layers of high performance materials that are designed to protect the inflatable structure from heat loads that would be seen in flight during atmospheric entry. A custom test fixture was constructed to perform the static load test series. The fixture consisted of a round structural tub with enough height and width to allow for displacement of the HIAD test article as loads were applied. The bottom of the tub rim had an airtight seal with the floor. The rigid centerbody of the HIAD was mounted to a pedestal in the center of the structural tub. Using an impermeable membrane draped over the HIAD test article, an airtight seal was created with the top rim of the static load tub. This seal allowed partial vacuum to be pulled beneath the HIAD resulting in a uniform static pressure load applied to the outer surface. Using this technique, the test article
NASA Technical Reports Server (NTRS)
Hanson, P. W.
1980-01-01
The characteristics and capabilities of the two tunnels, that relate to studies in the fields of aeroelasticity and unsteady aerodynamics are discussed. Scaling considerations for aeroelasticity and unsteady aerodynamics testing in the two facilities are reviewed, and some of the special features (or lack thereof) of the Langley Research Center Transonic Dynamics Tunnel (TDT) and the National Transonic Facility (NTF) that will weigh heavily in any decisions conducting a given study in the two tunnels are discussed. For illustrative purposes a fighter and a transport airplane are scaled for tests in the NTF and in the TDT, and the resulting model characteristics are compared. The NTF was designed specifically to meet the need for higher Reynolds number capability for flow simulation in aerodynamic performance testing of aircraft designs. However, the NTF can be a valuable tool for evaluating the severity of Reynolds number effects in the areas of dynamic aeroelasticity and unsteady aerodynamics. On the other hand, the TDT was constructed specifically for studies and tests in the field of aeroelasticity. Except for tests requiring the Reynolds number capability of NTF, the TDT will remain the primary facility for tests of dynamic aeroelasticity and unsteady aerodynamics.
NASA Astrophysics Data System (ADS)
Murray, Gabriel Jon
This dissertation is concerned with an active tab for use on a rotorcraft for noise and vibration reduction. The tab is located at the trailing edge of the airfoil. The tab consists of a shim sandwiched by layers of the piezoelectric actuators, macro fiber composites, of varying length. This configuration is similar to a bimorph. The modus operandi is similar to that of a trailing edge flap. The actuators deform the tab, bending it to achieve a tip displacement. This provides a change in the lift, moment, and drag coefficients of the airfoil. By actuating the system at 3/rev to 5/rev, reductions in noise and vibration can be realized. The system was examined and designed around using the UH-60 Blackhawk as the model rotorcraft. The tab is envisioned to operate between 65% to 85% of the main rotor span. The tab's chordwise dimensions considered were 20% and 15% of the blade chord. In order to assess the potential of the tab to change the lift and moment coefficients of the airfoil-tab system, a steady computational fluid dynamics study was conducted. The results were generated via the University of Maryland's Transonic Unsteady Navier-Stokes code. Various tab deflection angles, Mach numbers, and angle-of-attack values were computed. These results were compared to a trailing edge flap of similar size. The comparison shows that the tab produces lift and moment increments similar to that of the trailing edge flap. The design of the tab---composed of both active piezoelectric actuators and passive materials---was conducted using finite element analysis. The objectives were to maximize the tip deflection due to the actuators, while minimizing the deformation due to inertial and aerodynamic forces and loads. The inertial loads (acceleration terms) come from both blade motion, such as flapping and pitch, as well as the rotation of the rotor (centrifugal force). All of these previously mentioned terms cause the tab to undergo undesirable deflections. The original concept
NASA Technical Reports Server (NTRS)
Cox, T. H.; Gilyard, G. B.
1986-01-01
The drones for aerodynamic and structural testing (DAST) project was designed to control flutter actively at high subsonic speeds. Accurate knowledge of the structural model was critical for the successful design of the control system. A ground vibration test was conducted on the DAST vehicle to determine the structural model characteristics. This report presents and discusses the vibration and test equipment, the test setup and procedures, and the antisymmetric and symmetric mode shape results. The modal characteristics were subsequently used to update the structural model employed in the control law design process.
Prominence Structure and Dynamics
NASA Technical Reports Server (NTRS)
Karpen, Judy T.
2009-01-01
Nonerupting prominences are not dull, static objects. Rather, they are composed of fine-scale blobs and threads that are highly dynamic, often appearing to travel in opposite directions on adjacent tracks (denoted counterstreaming). Because the plasma is largely constrained to travel along the magnetic field, these cool, dense features can serve as tracers of the prominence magnetic structure, a valuable resource in view of the long-standing difficulty of observing the coronal field. Conversely, greater understanding of the fundamental magnetic geometry of filament channels can provide important constraints on the physical processes governing the accumulation, support, motion, and eruption of the cool plasma. Despite over a century of detailed observations, large gaps remain in our knowledge of filament channel/plasma formation and evolution. Resolving these issues will shed light on the physics of coronal heating, helicity transport throughout the solar cycle, and the origins of eruptive activity on the Sun. I will discuss the leading models for the magnetic and plasma structure, and outline how new observations and theory /modeling could solve long-standing uncertainties regarding this majestic solar phenomenon.
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.
Structural dynamics verification facility study
NASA Technical Reports Server (NTRS)
Kiraly, L. J.; Hirchbein, M. S.; Mcaleese, J. M.; Fleming, D. P.
1981-01-01
The need for a structural dynamics verification facility to support structures programs was studied. Most of the industry operated facilities are used for highly focused research, component development, and problem solving, and are not used for the generic understanding of the coupled dynamic response of major engine subsystems. Capabilities for the proposed facility include: the ability to both excite and measure coupled structural dynamic response of elastic blades on elastic shafting, the mechanical simulation of various dynamical loadings representative of those seen in operating engines, and the measurement of engine dynamic deflections and interface forces caused by alternative engine mounting configurations and compliances.
Progressive Aerodynamic Model Identification From Dynamic Water Tunnel Test of the F-16XL Aircraft
NASA Technical Reports Server (NTRS)
Murphy, Patrick C.; Klein, Vladislav; Szyba, Nathan M.
2004-01-01
Development of a general aerodynamic model that is adequate for predicting the forces and moments in the nonlinear and unsteady portions of the flight envelope has not been accomplished to a satisfactory degree. Predicting aerodynamic response during arbitrary motion of an aircraft over the complete flight envelope requires further development of the mathematical model and the associated methods for ground-based testing in order to allow identification of the model. In this study, a general nonlinear unsteady aerodynamic model is presented, followed by a summary of a linear modeling methodology that includes test and identification methods, and then a progressive series of steps suggesting a roadmap to develop a general nonlinear methodology that defines modeling, testing, and identification methods. Initial steps of the general methodology were applied to static and oscillatory test data to identify rolling-moment coefficient. Static measurements uncovered complicated dependencies of the aerodynamic coefficient on angle of attack and sideslip in the stall region making it difficult to find a simple analytical expression for the measurement data. In order to assess the effect of sideslip on the damping and unsteady terms, oscillatory tests in roll were conducted at different values of an initial offset in sideslip. Candidate runs for analyses were selected where higher order harmonics were required for the model and where in-phase and out-of-phase components varied with frequency. From these results it was found that only data in the angle-of-attack range of 35 degrees to 37.5 degrees met these requirements. From the limited results it was observed that the identified models fit the data well and both the damping-in-roll and the unsteady term gain are decreasing with increasing sideslip and motion amplitude. Limited similarity between parameter values in the nonlinear model and the linear model suggest that identifiability of parameters in both terms may be a
NASA Technical Reports Server (NTRS)
Nielsen, Jack N.
1988-01-01
The fundamental aerodynamics of slender bodies is examined in the reprint edition of an introductory textbook originally published in 1960. Chapters are devoted to the formulas commonly used in missile aerodynamics; slender-body theory at supersonic and subsonic speeds; vortices in viscid and inviscid flow; wing-body interference; downwash, sidewash, and the wake; wing-tail interference; aerodynamic controls; pressure foredrag, base drag, and skin friction; and stability derivatives. Diagrams, graphs, tables of terms and formulas are provided.
Stuart, J.G.; Wright, A.D.; Butterfield, C.P.
1996-10-01
Mitigating the effects of damaging wind turbine loads and responses extends the lifetime of the turbine and, consequently, reduces the associated Cost of Energy (COE). Active control of aerodynamic devices is one option for achieving wind turbine load mitigation. Generally speaking, control system design and analysis requires a reasonable dynamic model of {open_quotes}plant,{close_quotes} (i.e., the system being controlled). This paper extends the wind turbine aileron control research, previously conducted at the National Wind Technology Center (NWTC), by presenting a more detailed development of the wind turbine dynamic model. In prior research, active aileron control designs were implemented in an existing wind turbine structural dynamics code, FAST (Fatigue, Aerodynamics, Structures, and Turbulence). In this paper, the FAST code is used, in conjunction with system identification, to generate a wind turbine dynamic model for use in active aileron control system design. The FAST code is described and an overview of the system identification technique is presented. An aileron control case study is used to demonstrate this modeling technique. The results of the case study are then used to propose ideas for generalizing this technique for creating dynamic models for other wind turbine control applications.
NASA Astrophysics Data System (ADS)
Gao, YingYing; He, Feng; Shen, MengYu
2011-04-01
Based on the idea of adjoint method and the dynamic evolution method, a new optimum aerodynamic design technique is presented in this paper. It can be applied to the optimum problems with a large number of design variables and is time saving. The key of the new method lies in that the optimization process is regarded as an unsteady evolution, i.e., the optimization is executed, simultaneously with solving the unsteady flow governing equations and adjoint equations. Numerical examples for both the inverse problem and drag minimization using Euler equations have been presented, and the results show that the method presented in this paper is more efficient than the optimum methods based on the steady flow solution and the steady solution of adjoint equations.
NASA Technical Reports Server (NTRS)
Brandon, Jay M.; Foster, John V.
1998-01-01
As airplane designs have trended toward the expansion of flight envelopes into the high angle of attack and high angular rate regimes, concerns regarding modeling the complex unsteady aerodynamics for simulation have arisen. Most current modeling methods still rely on traditional body axis damping coefficients that are measured using techniques which were intended for relatively benign flight conditions. This paper presents recent wind tunnel results obtained during large-amplitude pitch, roll and yaw testing of several fighter airplane configurations. A review of the similitude requirements for applying sub-scale test results to full-scale conditions is presented. Data is then shown to be a strong function of Strouhal number - both the traditional damping terms, but also the associated static stability terms. Additionally, large effects of sideslip are seen in the damping parameter that should be included in simulation math models. Finally, an example of the inclusion of frequency effects on the data in a simulation is shown.
NASA Technical Reports Server (NTRS)
Dawson, Kenneth S.; Fortin, Paul E.
1987-01-01
The results of an integrated study of structures, aerodynamics, and controls using the STARS program on two advanced airplane configurations are presented. Results for the X-29A include finite element modeling, free vibration analyses, unsteady aerodynamic calculations, flutter/divergence analyses, and an aeroservoelastic controls analysis. Good correlation is shown between STARS results and various other verified results. The tasks performed on the Oblique Wing Research Aircraft include finite element modeling and free vibration analyses.
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.
NASA Technical Reports Server (NTRS)
Peele, E. L.; Adams, W. M., Jr.
1979-01-01
A computer program, ISAC, is described which calculates the stability and response of a flexible airplane equipped with active controls. The equations of motion relative to a fixed inertial coordinate system are formulated in terms of the airplane's rigid body motion and its unrestrained normal vibration modes. Unsteady aerodynamic forces are derived from a doublet lattice lifting surface theory. The theoretical basis for the program is briefly explained together with a description of input data and output results.
Projectiles Impact Assessment of Aircraft Wing Structures with Real Dynamic Load
NASA Astrophysics Data System (ADS)
Han, Lu; Han, Qing; Wang, Changlin
2015-07-01
This paper presents an analysis to achieve the impact damage of the wing structure under real dynamic load. MPCCI tools are utilized to convert wing aerodynamic load into structural Finite Element Method (FEM) node load. The ANSYS/LS-DYNA code is also used to simulate the dynamic loading effects of the wing structure hit by several projectiles, including both active damage mechanism and common damage mechanism. In addition, structural node force on the leading edge and the midline is compared to the aerodynamic load separately. Furthermore, the statistical analysis of the penetrating size and the stress concentration around the damage holes indicates that under the same load situation, the structural damage efficiency of active damage mechanism is significantly higher than the one of common damage mechanism.
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.
Evaluation of Rotor Structural and Aerodynamic Loads using Measured Blade Properties
NASA Technical Reports Server (NTRS)
Jung, Sung N.; You, Young-Hyun; Lau, Benton H.; Johnson, Wayne; Lim, Joon W.
2012-01-01
The structural properties of Higher harmonic Aeroacoustic Rotor Test (HART I) blades have been measured using the original set of blades tested in the wind tunnel in 1994. A comprehensive rotor dynamics analysis is performed to address the effect of the measured blade properties on airloads, blade motions, and structural loads of the rotor. The measurements include bending and torsion stiffness, geometric offsets, and mass and inertia properties of the blade. The measured properties are correlated against the estimated values obtained initially by the manufacturer of the blades. The previously estimated blade properties showed consistently higher stiffnesses, up to 30% for the flap bending in the blade inboard root section. The measured offset between the center of gravity and the elastic axis is larger by about 5% chord length, as compared with the estimated value. The comprehensive rotor dynamics analysis was carried out using the measured blade property set for HART I rotor with and without HHC (Higher Harmonic Control) pitch inputs. A significant improvement on blade motions and structural loads is obtained with the measured blade properties.
Dynamics of cylindrical converging shock waves interacting with aerodynamic obstacle arrays
NASA Astrophysics Data System (ADS)
Vignati, F.; Guardone, A.
2015-06-01
Cylindrical converging shock waves interacting with an array of aerodynamic obstacles are investigated numerically for diverse shock strengths and for different obstacle configurations in air in standard conditions. The considered number of obstacles N is 4, 6, 8, 16, and 24. Obstacles are lenticular airfoils with thickness-to-chord ratios t/c of 0.07, 0.14, and 0.21. The distances of the airfoil leading edge from the shock focus point r LE/rLE ref are 1, 2, and 2.5, where rLE ref = 7 is the dimensionless reference distance from the origin. Considered impinging shock Mach numbers Ms are 2.2, 2.7, and 3.2 at the reference distance from the origin. The reference experimental configuration ( N = 8 , t/c = 0 . 14 , r LE = 7 , M s = 2 . 7 ) was proposed by Kjellander et al. ["Thermal radiation from a converging shock implosion," Phys. Fluids 22, 046102 (2010)]. Numerical results compare fairly well to available one-dimensional models for shock propagation and to available experimental results in the reference configuration. Local reflection types are in good agreement with the classical criteria for planar shock waves. The main shock reshaping patterns are identified and their dependence on the shock strength and obstacle configuration is exposed. In particular, different shock patterns are observed after the leading edge reflection, which results in polygonal shock wave with N, 2N, 3N, and 4N sides. The largest temperature peak at the origin is obtained for the 8- and the 16-obstacle configurations and for the smallest thickness to length ratio, 0.07, located at distance from the origin of 2 rLE ref . In terms of compression efficiency at the origin, the 16-obstacle configuration is found to perform slightly better than the reference 8-obstacle configuration—with an efficiency increase of about 2%-3%, which is well within the model accuracy—thus confirming the goodness of the obstacle arrangement proposed by Kjellander and collaborators.
Dynamics of cylindrical converging shock waves interacting with aerodynamic obstacle arrays
Vignati, F.; Guardone, A.
2015-06-15
Cylindrical converging shock waves interacting with an array of aerodynamic obstacles are investigated numerically for diverse shock strengths and for different obstacle configurations in air in standard conditions. The considered number of obstacles N is 4, 6, 8, 16, and 24. Obstacles are lenticular airfoils with thickness-to-chord ratios t/c of 0.07, 0.14, and 0.21. The distances of the airfoil leading edge from the shock focus point (r{sub LE})/(r{sub LE}{sup ref}) are 1, 2, and 2.5, where r{sub LE}{sup ref}=7 is the dimensionless reference distance from the origin. Considered impinging shock Mach numbers M{sub s} are 2.2, 2.7, and 3.2 at the reference distance from the origin. The reference experimental configuration (N=8,t/c =0.14,r{sub LE}=7,M{sub s}=2.7) was proposed by Kjellander et al. [“Thermal radiation from a converging shock implosion,” Phys. Fluids 22, 046102 (2010)]. Numerical results compare fairly well to available one-dimensional models for shock propagation and to available experimental results in the reference configuration. Local reflection types are in good agreement with the classical criteria for planar shock waves. The main shock reshaping patterns are identified and their dependence on the shock strength and obstacle configuration is exposed. In particular, different shock patterns are observed after the leading edge reflection, which results in polygonal shock wave with N, 2N, 3N, and 4N sides. The largest temperature peak at the origin is obtained for the 8- and the 16-obstacle configurations and for the smallest thickness to length ratio, 0.07, located at distance from the origin of 2r{sub LE}{sup ref}. In terms of compression efficiency at the origin, the 16-obstacle configuration is found to perform slightly better than the reference 8-obstacle configuration—with an efficiency increase of about 2%-3%, which is well within the model accuracy—thus confirming the goodness of the obstacle arrangement proposed by Kjellander and
NASA Technical Reports Server (NTRS)
Selberg, B. P.; Cronin, D. L.
1985-01-01
An analytical aerodynamic-structural airplane configuration study was conducted to assess performance gains achievable through advanced design concepts. The mission specification was for 350 mph, range of 1500 st. mi., at altitudes between 30,000 and 40,000 ft. Two payload classes were studied - 1200 lb (6 passengers) and 2400 lb (12 passengers). The configurations analyzed included canard wings, closely coupled dual wings, swept forward - swept rearward wings, joined wings, and conventional wing tail arrangements. The results illustrate substantial performance gains possible with the dual wing configuration. These gains result from weight savings due to predicted structural efficiencies. The need for further studies of structural efficiencies for the various advanced configurations was highlighted.
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.
Molecular dynamics modelling of mechanical properties of polymers for adaptive aerospace structures
NASA Astrophysics Data System (ADS)
Papanikolaou, Michail; Drikakis, Dimitris; Asproulis, Nikolaos
2015-02-01
The features of adaptive structures depend on the properties of the supporting materials. For example, morphing wing structures require wing skin materials, such as rubbers that can withstand the forces imposed by the internal mechanism while maintaining the required aerodynamic properties of the aircraft. In this study, Molecular Dynamics and Minimization simulations are being used to establish well-equilibrated models of Ethylene-Propylene-Diene Monomer (EPDM) elastomer systems and investigate their mechanical properties.
Structural Mechanics and Dynamics Branch
NASA Technical Reports Server (NTRS)
Stefko, George
2003-01-01
The 2002 annual report of the Structural Mechanics and Dynamics Branch reflects the majority of the work performed by the branch staff during the 2002 calendar year. Its purpose is to give a brief review of the branch s technical accomplishments. The Structural Mechanics and Dynamics Branch develops innovative computational tools, benchmark experimental data, and solutions to long-term barrier problems in the areas of propulsion aeroelasticity, active and passive damping, engine vibration control, rotor dynamics, magnetic suspension, structural mechanics, probabilistics, smart structures, engine system dynamics, and engine containment. Furthermore, the branch is developing a compact, nonpolluting, bearingless electric machine with electric power supplied by fuel cells for future "more electric" aircraft. An ultra-high-power-density machine that can generate projected power densities of 50 hp/lb or more, in comparison to conventional electric machines, which generate usually 0.2 hp/lb, is under development for application to electric drives for propulsive fans or propellers. In the future, propulsion and power systems will need to be lighter, to operate at higher temperatures, and to be more reliable in order to achieve higher performance and economic viability. The Structural Mechanics and Dynamics Branch is working to achieve these complex, challenging goals.
Defraeye, Thijs; Blocken, Bert; Koninckx, Erwin; Hespel, Peter; Carmeliet, Jan
2010-08-26
This study aims at assessing the accuracy of computational fluid dynamics (CFD) for applications in sports aerodynamics, for example for drag predictions of swimmers, cyclists or skiers, by evaluating the applied numerical modelling techniques by means of detailed validation experiments. In this study, a wind-tunnel experiment on a scale model of a cyclist (scale 1:2) is presented. Apart from three-component forces and moments, also high-resolution surface pressure measurements on the scale model's surface, i.e. at 115 locations, are performed to provide detailed information on the flow field. These data are used to compare the performance of different turbulence-modelling techniques, such as steady Reynolds-averaged Navier-Stokes (RANS), with several k-epsilon and k-omega turbulence models, and unsteady large-eddy simulation (LES), and also boundary-layer modelling techniques, namely wall functions and low-Reynolds number modelling (LRNM). The commercial CFD code Fluent 6.3 is used for the simulations. The RANS shear-stress transport (SST) k-omega model shows the best overall performance, followed by the more computationally expensive LES. Furthermore, LRNM is clearly preferred over wall functions to model the boundary layer. This study showed that there are more accurate alternatives for evaluating flow around bluff bodies with CFD than the standard k-epsilon model combined with wall functions, which is often used in CFD studies in sports. PMID:20488446
Pyroclastic current dynamic pressure from aerodynamics of tree or pole blow-down
NASA Astrophysics Data System (ADS)
Clarke, A. B.; Voight, B.
2000-07-01
The common occurrence of tree and pole blow-down from pyroclastic currents provides an opportunity to estimate properties of the currents. Blow-down may occur by uprooting (root zone rupture), or flexure or shear at some point on the object. If trees are delimbed before blow-down, each tree or pole can be simulated by a cylinder perpendicular to the current. The force acting on a cylinder is a function of flow dynamic pressure, cylinder geometry, and drag coefficient. Treated as a cantilever of circular cross-section, the strength for the appropriate failure mode (rupture, uprooting or flexure) can then be used to estimate the minimum necessary current dynamic pressure. In some cases, larger or stronger standing objects can provide upper bounds on the dynamic pressure. This analysis was treated in two ways: (1) assuming that the current properties are vertically constant; and (2) allowing current velocity and density to vary vertically according to established models for turbulent boundary layers and stratified flow. The two methods produced similar results for dynamic pressure. The second, along with a method to approximate average whole-current density, offers a means to estimate average velocity and density over the height of the failed objects. The method is applied to several example cases, including Unzen, Mount St. Helens, Lamington, and Merapi volcanoes. Our results compare reasonably well with independent estimates. For several cases, we found that it is possible to use the dynamic pressure equations developed for vertically uniform flow, along with the average cloud density multiplied by a factor of 2-5, to determine average velocity over the height of the failed object.
NASA/USAF research in structural dynamics
NASA Technical Reports Server (NTRS)
Pinson, L. D.; Amos, A. K.
1983-01-01
Research in the structural dynamics of large space structures is discussed. The problems of structural response are emphasized. Dynamic modeling, structural members, finite element techniques, axial loads, and vibration tests are among the topics discussed.
Dynamical structure in paleoclimate data
Stewart, H.B.
1994-12-01
Deterministic chaos in dynamical systems offers a new paradigm for understanding irregular fluctuations. The theory of chaotic dynamical systems includes methods which can test whether any given set of time series data, such as paleoclimate proxy data, are consistent with a deterministic interpretation. Paleoclimate data with annual resolution and absolute dating provide multiple channels of concurrent time series; these multiple time series can be treated as potential phase space coordinates to test whether interannual climate variability is deterministic. Dynamical structure tests which take advantage of such multichannel data are proposed and illustrated by application to a simple synthetic model of chaos, and to two paleoclimate proxy data series.
Dynamic Modeling of Starting Aerodynamics and Stage Matching in an Axi-Centrifugal Compressor
NASA Technical Reports Server (NTRS)
Wilkes, Kevin; OBrien, Walter F.; Owen, A. Karl
1996-01-01
A DYNamic Turbine Engine Compressor Code (DYNTECC) has been modified to model speed transients from 0-100% of compressor design speed. The impetus for this enhancement was to investigate stage matching and stalling behavior during a start sequence as compared to rotating stall events above ground idle. The model can simulate speed and throttle excursions simultaneously as well as time varying bleed flow schedules. Results of a start simulation are presented and compared to experimental data obtained from an axi-centrifugal turboshaft engine and companion compressor rig. Stage by stage comparisons reveal the front stages to be operating in or near rotating stall through most of the start sequence. The model matches the starting operating line quite well in the forward stages with deviations appearing in the rearward stages near the start bleed. Overall, the performance of the model is very promising and adds significantly to the dynamic simulation capabilities of DYNTECC.
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.
Coherent structures and dynamical systems
NASA Technical Reports Server (NTRS)
Jimenez, Javier
1987-01-01
Any flow of a viscous fluid has a finite number of degrees of freedom, and can therefore be seen as a dynamical system. A coherent structure can be thought of as a lower dimensional manifold in whose neighborhood the dynamical system spends a substantial fraction of its time. If such a manifold exists, and if its dimensionality is substantially lower that that of the full flow, it is conceivable that the flow could be described in terms of the reduced set of degrees of freedom, and that such a description would be simpler than one in which the existence of structure was not recognized. Several examples are briefly summarized.
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.
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.
Improved Aerodynamic Analysis for Hybrid Wing Body Conceptual Design Optimization
NASA Technical Reports Server (NTRS)
Gern, Frank H.
2012-01-01
This paper provides an overview of ongoing efforts to develop, evaluate, and validate different tools for improved aerodynamic modeling and systems analysis of Hybrid Wing Body (HWB) aircraft configurations. Results are being presented for the evaluation of different aerodynamic tools including panel methods, enhanced panel methods with viscous drag prediction, and computational fluid dynamics. Emphasis is placed on proper prediction of aerodynamic loads for structural sizing as well as viscous drag prediction to develop drag polars for HWB conceptual design optimization. Data from transonic wind tunnel tests at the Arnold Engineering Development Center s 16-Foot Transonic Tunnel was used as a reference data set in order to evaluate the accuracy of the aerodynamic tools. Triangularized surface data and Vehicle Sketch Pad (VSP) models of an X-48B 2% scale wind tunnel model were used to generate input and model files for the different analysis tools. In support of ongoing HWB scaling studies within the NASA Environmentally Responsible Aviation (ERA) program, an improved finite element based structural analysis and weight estimation tool for HWB center bodies is currently under development. Aerodynamic results from these analyses are used to provide additional aerodynamic validation data.
NASA Technical Reports Server (NTRS)
Wynne, Eleanor C.
1992-01-01
The work under each technical area is described in terms of highlights of accomplishments during the past year and highlights of plans for the current year as they relate to 5 year plans for each technical area. This information will be useful in program coordination with other government organizations and industry in areas of mutual interest. The structural dynamics division consist of the following branches: configuration aeroelasticity; unsteady aerodynamics; aeroservoelasticity; landing and impact dynamics; and spacecraft dynamics.
A Multi-Phase Based Fluid-Structure-Microfluidic interaction sensor for Aerodynamic Shear Stress
NASA Astrophysics Data System (ADS)
Hughes, Christopher; Dutta, Diganta; Bashirzadeh, Yashar; Ahmed, Kareem; Qian, Shizhi
2014-11-01
A novel innovative microfluidic shear stress sensor is developed for measuring shear stress through multi-phase fluid-structure-microfluidic interaction. The device is composed of a microfluidic cavity filled with an electrolyte liquid. Inside the cavity, two electrodes make electrochemical velocimetry measurements of the induced convection. The cavity is sealed with a flexible superhydrophobic membrane. The membrane will dynamically stretch and flex as a result of direct shear cross-flow interaction with the seal structure, forming instability wave modes and inducing fluid motion within the microfluidic cavity. The shear stress on the membrane is measured by sensing the induced convection generated by membrane deflections. The advantages of the sensor over current MEMS based shear stress sensor technology are: a simplified design with no moving parts, optimum relationship between size and sensitivity, no gaps such as those created by micromachining sensors in MEMS processes. We present the findings of a feasibility study of the proposed sensor including wind-tunnel tests, microPIV measurements, electrochemical velocimetry, and simulation data results. The study investigates the sensor in the supersonic and subsonic flow regimes. Supported by a NASA SBIR phase 1 contract.
Structural system identification: Structural dynamics model validation
Red-Horse, J.R.
1997-04-01
Structural system identification is concerned with the development of systematic procedures and tools for developing predictive analytical models based on a physical structure`s dynamic response characteristics. It is a multidisciplinary process that involves the ability (1) to define high fidelity physics-based analysis models, (2) to acquire accurate test-derived information for physical specimens using diagnostic experiments, (3) to validate the numerical simulation model by reconciling differences that inevitably exist between the analysis model and the experimental data, and (4) to quantify uncertainties in the final system models and subsequent numerical simulations. The goal of this project was to develop structural system identification techniques and software suitable for both research and production applications in code and model validation.
NASA Technical Reports Server (NTRS)
Stone, N. H.
1981-01-01
The objectives are to provide a parametric description of the electrostatic interaction of a mesosonic, collisionless plasma with conducting bodies on the order of 1 to 10 Debye lengths in size, and to extend this description to the satellite-ionospheric interaction, where possible. Experimental findings include: the wake of the geometrically complex body appears to be a linear superposition of the wakes of its simple geometric components; and vector ion flux measurements show converging ion streams at the wake axis and direct evidence of ion streams deflected from the wake axis by the positive space charge potential associated with the axial ion peak. The extension to the satellite-ionospheric interaction utilizes qualitative scaling and indicates that similar, but smaller amplitude, wake structures may be expected for small or highly charged bodies. However, for large bodies at small potentials, the structure may be diffused by the thermal ion motion and the dispersion resulting for space charge potentials.
Visual analysis of fluid dynamics at NASA's numerical aerodynamic simulation facility
NASA Technical Reports Server (NTRS)
Watson, Velvin R.
1991-01-01
A study aimed at describing and illustrating visualization tools used in Computational Fluid Dynamics (CFD) and indicating how these tools are likely to change by showing a projected resolution of the human computer interface is presented. The following are outlined using a graphically based test format: the revolution of human computer environments for CFD research; comparison of current environments; current environments with the ideal; predictions for the future CFD environments; what can be done to accelerate the improvements. The following comments are given: when acquiring visualization tools, potential rapid changes must be considered; environmental changes over the next ten years due to human computer interface cannot be fathomed; data flow packages such as AVS, apE, Explorer and Data Explorer are easy to learn and use for small problems, excellent for prototyping, but not so efficient for large problems; the approximation techniques used in visualization software must be appropriate for the data; it has become more cost effective to move jobs that fit on workstations and run only memory intensive jobs on the supercomputer; use of three dimensional skills will be maximized when the three dimensional environment is built in from the start.
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.
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.
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.
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.
Dynamically variable negative stiffness structures
Churchill, Christopher B.; Shahan, David W.; Smith, Sloan P.; Keefe, Andrew C.; McKnight, Geoffrey P.
2016-01-01
Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness–based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel response from passive structures, is a powerful tool to achieve dynamic stiffness changes when configured with an active component. Using relatively simple hardware and low-power, low-frequency actuation, we show an assembly capable of fast (<10 ms) and useful (>100×) dynamic stiffness control. This approach mitigates limitations of conventional tunable stiffness structures that exhibit either small (<30%) stiffness change, high friction, poor load/torque transmission at low stiffness, or high power active control at the frequencies of interest. We experimentally demonstrate actively tunable vibration isolation and stiffness tuning independent of supported loads, enhancing applications such as humanoid robotic limbs and lightweight adaptive vibration isolators. PMID:26989771
Dynamically variable negative stiffness structures.
Churchill, Christopher B; Shahan, David W; Smith, Sloan P; Keefe, Andrew C; McKnight, Geoffrey P
2016-02-01
Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness-based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel response from passive structures, is a powerful tool to achieve dynamic stiffness changes when configured with an active component. Using relatively simple hardware and low-power, low-frequency actuation, we show an assembly capable of fast (<10 ms) and useful (>100×) dynamic stiffness control. This approach mitigates limitations of conventional tunable stiffness structures that exhibit either small (<30%) stiffness change, high friction, poor load/torque transmission at low stiffness, or high power active control at the frequencies of interest. We experimentally demonstrate actively tunable vibration isolation and stiffness tuning independent of supported loads, enhancing applications such as humanoid robotic limbs and lightweight adaptive vibration isolators. PMID:26989771
NASA Astrophysics Data System (ADS)
Taneja, Jayant Kumar
Electricity is an indispensable commodity to modern society, yet it is delivered via a grid architecture that remains largely unchanged over the past century. A host of factors are conspiring to topple this dated yet venerated design: developments in renewable electricity generation technology, policies to reduce greenhouse gas emissions, and advances in information technology for managing energy systems. Modern electric grids are emerging as complex distributed systems in which a portfolio of power generation resources, often incorporating fluctuating renewable resources such as wind and solar, must be managed dynamically to meet uncontrolled, time-varying demand. Uncertainty in both supply and demand makes control of modern electric grids fundamentally more challenging, and growing portfolios of renewables exacerbate the challenge. We study three electricity grids: the state of California, the province of Ontario, and the country of Germany. To understand the effects of increasing renewables, we develop a methodology to scale renewables penetration. Analyzing these grids yields key insights about rigid limits to renewables penetration and their implications in meeting long-term emissions targets. We argue that to achieve deep penetration of renewables, the operational model of the grid must be inverted, changing the paradigm from load-following supplies to supply-following loads. To alleviate the challenge of supply-demand matching on deeply renewable grids, we first examine well-known techniques, including altering management of existing supply resources, employing utility-scale energy storage, targeting energy efficiency improvements, and exercising basic demand-side management. Then, we create several instantiations of supply-following loads -- including refrigerators, heating and cooling systems, and laptop computers -- by employing a combination of sensor networks, advanced control techniques, and enhanced energy storage. We examine the capacity of each load
Some recent advances in computational aerodynamics for helicopter applications
NASA Technical Reports Server (NTRS)
Mccroskey, W. J.; Baeder, J. D.
1985-01-01
The growing application of computational aerodynamics to nonlinear helicopter problems is outlined, with particular emphasis on several recent quasi-two-dimensional examples that used the thin-layer Navier-Stokes equations and an eddy-viscosity model to approximate turbulence. Rotor blade section characteristics can now be calculated accurately over a wide range of transonic flow conditions. However, a finite-difference simulation of the complete flow field about a helicopter in forward flight is not currently feasible, despite the impressive progress that is being made in both two and three dimensions. The principal limitations are today's computer speeds and memories, algorithm and solution methods, grid generation, vortex modeling, structural and aerodynamic coupling, and a shortage of engineers who are skilled in both computational fluid dynamics and helicopter aerodynamics and dynamics.
The DELTA MONSTER: An RPV designed to investigate the aerodynamics of a delta wing platform
NASA Technical Reports Server (NTRS)
Connolly, Kristen; Flynn, Mike; Gallagher, Randy; Greek, Chris; Kozlowski, Marc; Mcdonald, Brian; Mckenna, Matt; Sellar, Rich; Shearon, Andy
1989-01-01
The mission requirements for the performance of aerodynamic tests on a delta wind planform posed some problems, these include aerodynamic interference; structural support; data acquisition and transmission instrumentation; aircraft stability and control; and propulsion implementation. To eliminate the problems of wall interference, free stream turbulence, and the difficulty of achieving dynamic similarity between the test and actual flight aircraft that are associated with aerodynamic testing in wind tunnels, the concept of the remotely piloted vehicle which can perform a basic aerodynamic study on a delta wing was the main objective for the Green Mission - the Delta Monster. The basic aerodynamic studies were performed on a delta wing with a sweep angle greater than 45 degrees. These tests were performed at various angles of attack and Reynolds numbers. The delta wing was instrumented to determine the primary leading edge vortex formation and location, using pressure measurements and/or flow visualization. A data acquisition system was provided to collect all necessary data.
Structurally Dynamic Spin Market Networks
NASA Astrophysics Data System (ADS)
Horváth, Denis; Kuscsik, Zoltán
The agent-based model of stock price dynamics on a directed evolving complex network is suggested and studied by direct simulation. The stationary regime is maintained as a result of the balance between the extremal dynamics, adaptivity of strategic variables and reconnection rules. The inherent structure of node agent "brain" is modeled by a recursive neural network with local and global inputs and feedback connections. For specific parametric combination the complex network displays small-world phenomenon combined with scale-free behavior. The identification of a local leader (network hub, agent whose strategies are frequently adapted by its neighbors) is carried out by repeated random walk process through network. The simulations show empirically relevant dynamics of price returns and volatility clustering. The additional emerging aspects of stylized market statistics are Zipfian distributions of fitness.
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
Sierra Structural Dynamics User's Notes
Reese, Garth M.
2015-10-19
Sierra/SD provides a massively parallel implementation of structural dynamics finite element analysis, required for high fidelity, validated models used in modal, vibration, static and shock analysis of weapons systems. This document provides a users guide to the input for Sierra/SD. Details of input specifications for the different solution types, output options, element types and parameters are included. The appendices contain detailed examples, and instructions for running the software on parallel platforms.
Thermo-viscoplastic analysis of hypersonic structures subjected to severe aerodynamic heating
NASA Technical Reports Server (NTRS)
Thornton, Earl A.; Oden, J. Tinsley; Tworzydlo, W. Woytek; Youn, Sung-Kie
1989-01-01
A thermoviscoplastic computational method for hypersonic structures is presented. The method employs unified viscoplastic constitutive model implemented in a finite element approach for quasi-static thermal-structural analysis. Applications of the approach to convectively cooled hypersonic structures illustrate the effectiveness of the approach and provide insight into the transient inelastic structural behavior at elevated temperatures.
Evolutionary dynamics in structured populations
Nowak, Martin A.; Tarnita, Corina E.; Antal, Tibor
2010-01-01
Evolutionary dynamics shape the living world around us. At the centre of every evolutionary process is a population of reproducing individuals. The structure of that population affects evolutionary dynamics. The individuals can be molecules, cells, viruses, multicellular organisms or humans. Whenever the fitness of individuals depends on the relative abundance of phenotypes in the population, we are in the realm of evolutionary game theory. Evolutionary game theory is a general approach that can describe the competition of species in an ecosystem, the interaction between hosts and parasites, between viruses and cells, and also the spread of ideas and behaviours in the human population. In this perspective, we review the recent advances in evolutionary game dynamics with a particular emphasis on stochastic approaches in finite sized and structured populations. We give simple, fundamental laws that determine how natural selection chooses between competing strategies. We study the well-mixed population, evolutionary graph theory, games in phenotype space and evolutionary set theory. We apply these results to the evolution of cooperation. The mechanism that leads to the evolution of cooperation in these settings could be called ‘spatial selection’: cooperators prevail against defectors by clustering in physical or other spaces. PMID:20008382
Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks
NASA Technical Reports Server (NTRS)
Jorgensen, Charles C.
1997-01-01
A Dynamic Cell Structure (DCS) Neural Network was developed which learns topology representing networks (TRNS) of F-15 aircraft aerodynamic stability and control derivatives. The network is integrated into a direct adaptive tracking controller. The combination produces a robust adaptive architecture capable of handling multiple accident and off- nominal flight scenarios. This paper describes the DCS network and modifications to the parameter estimation procedure. The work represents one step towards an integrated real-time reconfiguration control architecture for rapid prototyping of new aircraft designs. Performance was evaluated using three off-line benchmarks and on-line nonlinear Virtual Reality simulation. Flight control was evaluated under scenarios including differential stabilator lock, soft sensor failure, control and stability derivative variations, and air turbulence.
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.
Computational Methods for Structural Mechanics and Dynamics
NASA Technical Reports Server (NTRS)
Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)
1989-01-01
Topics addressed include: transient dynamics; transient finite element method; transient analysis in impact and crash dynamic studies; multibody computer codes; dynamic analysis of space structures; multibody mechanics and manipulators; spatial and coplanar linkage systems; flexible body simulation; multibody dynamics; dynamical systems; and nonlinear characteristics of joints.
Aerodynamic Modeling for Aircraft in Unsteady Flight Conditions
NASA Technical Reports Server (NTRS)
Lan, C. Edward
2000-01-01
This report summarizes the activities in unsteady aerodynamic modeling and application of unsteady aerodynamic models to flight dynamics. A public on briefing was presented on July 21, 1999 at Langley Research Center.
NASA Technical Reports Server (NTRS)
Wynne, Eleanor C.
1991-01-01
The research accomplishments of the Structural Dynamics Division for F.Y. 1991 are presented. The work is discussed in terms of highlights of accomplishments during the past year and plans for the current year as they relate to 5-year plans and the objectives of each technical area. Included is research on unsteady aerodynamics, helicopter rotors, computational fluid dynamics, oscillations of leading edge flaps of a delta wing, and aircraft wing loads.
Zelenyuk, Alla; Cai, Yong; Imre, Dan G.
2006-03-01
With the advert of aerosol instrumentation it has become possible to simultaneously measure individual particle mobility and vacuum aerodynamic diameters. For spherical particles these two diameters yield individual particle density. In contrast, assigning a physical meaning to the mobility or aerodynamic diameter of aspherical particles is not straightforward. This paper presents an experimental exploration of the effect of particle shape on the relationship between mobility and vacuum aerodynamic diameters. We make measurements on systems of three types: 1) Agglomerates of spheres, for which the density and the volume are known; 2) Ammonium sulfate, sodium chloride, succinic acid and lauric acid irregularly shaped particles of known density; and 3) Internally mixed particles, containing organics and ammonium sulfate, of unknown density and shape. For agglomerates of spheres we observed alignment effects in the DMA and report the first measurements of the dynamic shape factors (DSFs) in free molecular regime. We present here the first experimental determination of the DSF of ammonium sulfate particles. We find for ammonium sulfate particles a DSF that increases from 1.03 to 1.07 as particle mobility diameter increases from 160 nm to 500 nm. Three types of NaC1 particles were generated and characterized: nearly spherical particles with DSF of ~1.02; cubic with DSF that increases from 1.065 to 1.17 as particle mobility diameter increases from 200 nm to 900 nm; and compact agglomerates with DSF 1.3-1.4. Organic particles were found very nearly spherical. The data suggest that particles composed of binary mixtures of ammonium sulfate and succinic acid have lower dynamic shape factors than pure ammonium sulfate particles. However, for internally mixed ammonium sulfate and lauric acid particles we cannot distinguish between nearly spherical particles with low density and particles with DSF of 1.17.
Chromatin Structure in Telomere Dynamics
Galati, Alessandra; Micheli, Emanuela; Cacchione, Stefano
2013-01-01
The establishment of a specific nucleoprotein structure, the telomere, is required to ensure the protection of chromosome ends from being recognized as DNA damage sites. Telomere shortening below a critical length triggers a DNA damage response that leads to replicative senescence. In normal human somatic cells, characterized by telomere shortening with each cell division, telomere uncapping is a regulated process associated with cell turnover. Nevertheless, telomere dysfunction has also been associated with genomic instability, cell transformation, and cancer. Despite the essential role telomeres play in chromosome protection and in tumorigenesis, our knowledge of the chromatin structure involved in telomere maintenance is still limited. Here we review the recent findings on chromatin modifications associated with the dynamic changes of telomeres from protected to deprotected state and their role in telomere functions. PMID:23471416
Sierra Structural Dynamics Theory Manual
Reese, Garth M.
2015-10-19
Sierra/SD provides a massively parallel implementation of structural dynamics finite element analysis, required for high fidelity, validated models used in modal, vibration, static and shock analysis of structural systems. This manual describes the theory behind many of the constructs in Sierra/SD. For a more detailed description of how to use Sierra/SD , we refer the reader to Sierra/SD, User's Notes . Many of the constructs in Sierra/SD are pulled directly from published material. Where possible, these materials are referenced herein. However, certain functions in Sierra/SD are specific to our implementation. We try to be far more complete in those areas. The theory manual was developed from several sources including general notes, a programmer notes manual, the user's notes and of course the material in the open literature. This page intentionally left blank.
Aeroelastic effects in the structural dynamic analysis of vertical axis wind turbines
Lobitz, D.W.; Ashwill, T.D.
1985-01-01
Aeroelastic effects impact the structural dynamic behavior of vertical axis wind turbines (VAWTs) in two major ways. First the stability phenomena of flutter and divergence are direct results of the aeroelasticity of the structure. Secondly, aerodynamic damping can be important for predicting response levels particularly near resonance but also for off resonance conditions. The inclusion of the aeroelasticity is carried out by modifying the damping and stiffness matrices in the NASTRAN finite element code. Through the use of a specially designed preprocessor which reads the usual NASTRAN input deck and adds appropriate cards to it the incorporation of the aeroelastic effects has been made relatively transparent to the user NASTRAN flutter predictions are validated using field measurements and the effect of aerodynamic damping is demonstrated through an application to the Test Bed VAWT being designed at Sandia.
Aeroelastic effects in the structural dynamic analysis of vertical axis wind turbines
Lobitz, D.W.; Ashwill, T.D.
1986-04-01
Aeroelastic effects impact the structural dynamic behavior of vertical axis wind turbines (VAWRs) in two major ways. First, the stability phenomena of flutter and divergence are direct results of the aeroelasticity of the structure. Secondly, aerodynamic damping can be important for predicting response levels, particularly near resonance, but also for off-resonance conditions. The inclusion of the aeroelasticity is carried out by modifying the damping and stiffness matrices in the NASTRAN finite element code. Through the use of a specially designed preprocessor, which reads the usual NASTRAN input deck and adds appropriate cards to it, the incorporation of the aeroelastic effects has been made relatively transparent to the user. NASTRAN flutter predictions are validated using field measurements and the effect of aerodynamic damping is demonstrated through an application to the Test Bed VAWT being designed at Sandia.
Structural Dynamics of Electronic Systems
NASA Astrophysics Data System (ADS)
Suhir, E.
2013-03-01
The published work on analytical ("mathematical") and computer-aided, primarily finite-element-analysis (FEA) based, predictive modeling of the dynamic response of electronic systems to shocks and vibrations is reviewed. While understanding the physics of and the ability to predict the response of an electronic structure to dynamic loading has been always of significant importance in military, avionic, aeronautic, automotive and maritime electronics, during the last decade this problem has become especially important also in commercial, and, particularly, in portable electronics in connection with accelerated testing of various surface mount technology (SMT) systems on the board level. The emphasis of the review is on the nonlinear shock-excited vibrations of flexible printed circuit boards (PCBs) experiencing shock loading applied to their support contours during drop tests. At the end of the review we provide, as a suitable and useful illustration, the exact solution to a highly nonlinear problem of the dynamic response of a "flexible-and-heavy" PCB to an impact load applied to its support contour during drop testing.
Combustion fume structure and dynamics. Final report
Flagan, R.C.
1995-06-29
An investigation of the fundamental physical processes that govern the structures of fume particles that are produced from the vapor phase in a wide range of high temperature systems has been conducted. The key objective of this study has been to develop models of the evolution of fine particles of refractory materials that are produced from the vapor phase, with particular emphasis on those processes that govern the evolution of ash fumes produced from volatilized mineral matter during coal combustion. To accomplish this goal, the study has included investigations of a number of fundamental aspects of pyrogenous fumes: Structural characterization of agglomerate particles in terms of fractal structure parameters; the relationship between the structures of agglomerate particles and the aerodynamic drag forces they experience; coagulation kinetics of fractal-like particles; sintering of aerosol agglomerates past the early stage of neck formation and incorporating the simultaneous influences of several transport mechanisms.
NASA Astrophysics Data System (ADS)
Rivas McGowan, Anna-Maria; Wilkie, W. K.; Moses, Robert W.; Lake, Renee C.; Pinkerton Florance, Jennifer L.; Weiseman, Carol D.; Reaves, Mercedes C.; Taleghani, Barmac K.; Mirick, Paul H.; Wilbur, Matthew L.
1998-06-01
An overview of smart structures research currently underway a the NASA Langley Research Center in the areas of aeroservoelasticity and structural dynamics is presented. Analytical and experimental results, plans, potential technology pay-offs, and challenges are discussed. The goal of this research is to develop the enabling technologies to actively and passively control aircraft and rotorcraft vibration and loads using smart devices. These enabling technologies and related research efforts include developing experimentally validated finite element and aeroservoelastic modeling techniques; conducting bench experimental test to assess feasibility and understand system trade-offs; and conducting large-scale wind-tunnel of rotor blades using interdigitated electrode piezoelectric composites and active control of flutter, and gust and buffeting responses using discrete piezoelectric patches. In addition, NASA Langley is an active participant in the DARPA/Air Force Research Laboratory/NASA/Northrop Grumman Smart Wing program which is assessing aerodynamic performance benefits using smart materials.
Loads and Structural Dynamics Requirements for Spaceflight Hardware
NASA Technical Reports Server (NTRS)
Schultz, Kenneth P.
2011-01-01
The purpose of this document is to establish requirements relating to the loads and structural dynamics technical discipline for NASA and commercial spaceflight launch vehicle and spacecraft hardware. Requirements are defined for the development of structural design loads and recommendations regarding methodologies and practices for the conduct of load analyses are provided. As such, this document represents an implementation of NASA STD-5002. Requirements are also defined for structural mathematical model development and verification to ensure sufficient accuracy of predicted responses. Finally, requirements for model/data delivery and exchange are specified to facilitate interactions between Launch Vehicle Providers (LVPs), Spacecraft Providers (SCPs), and the NASA Technical Authority (TA) providing insight/oversight and serving in the Independent Verification and Validation role. In addition to the analysis-related requirements described above, a set of requirements are established concerning coupling phenomena or other interaction between structural dynamics and aerodynamic environments or control or propulsion system elements. Such requirements may reasonably be considered structure or control system design criteria, since good engineering practice dictates consideration of and/or elimination of the identified conditions in the development of those subsystems. The requirements are included here, however, to ensure that such considerations are captured in the design space for launch vehicles (LV), spacecraft (SC) and the Launch Abort Vehicle (LAV). The requirements in this document are focused on analyses to be performed to develop data needed to support structural verification. As described in JSC 65828, Structural Design Requirements and Factors of Safety for Spaceflight Hardware, implementation of the structural verification requirements is expected to be described in a Structural Verification Plan (SVP), which should describe the verification of each
NASA Technical Reports Server (NTRS)
Spekreijse, S. P.; Boerstoel, J. W.; Vitagliano, P. L.; Kuyvenhoven, J. L.
1992-01-01
About five years ago, a joint development was started of a flow simulation system for engine-airframe integration studies on propeller as well as jet aircraft. The initial system was based on the Euler equations and made operational for industrial aerodynamic design work. The system consists of three major components: a domain modeller, for the graphical interactive subdivision of flow domains into an unstructured collection of blocks; a grid generator, for the graphical interactive computation of structured grids in blocks; and a flow solver, for the computation of flows on multi-block grids. The industrial partners of the collaboration and NLR have demonstrated that the domain modeller, grid generator and flow solver can be applied to simulate Euler flows around complete aircraft, including propulsion system simulation. Extension to Navier-Stokes flows is in progress. Delft Hydraulics has shown that both the domain modeller and grid generator can also be applied successfully for hydrodynamic configurations. An overview is given about the main aspects of both domain modelling and grid generation.
Weber, J K R; Tamalonis, A; Benmore, C J; Alderman, O L G; Sendelbach, S; Hebden, A; Williamson, M A
2016-07-01
An aerodynamic levitator with carbon dioxide laser beam heating was integrated with a hermetically sealed controlled atmosphere chamber and sample handling mechanism. The system enabled containment of radioactive samples and control of the process atmosphere chemistry. The chamber was typically operated at a pressure of approximately 0.9 bars to ensure containment of the materials being processed. Samples 2.5-3 mm in diameter were levitated in flowing gas to achieve containerless conditions. Levitated samples were heated to temperatures of up to 3500 °C with a partially focused carbon dioxide laser beam. Sample temperature was measured using an optical pyrometer. The sample environment was integrated with a high energy (100 keV) x-ray synchrotron beamline to enable in situ structure measurements to be made on levitated samples as they were heated, melted, and supercooled. The system was controlled from outside the x-ray beamline hutch by using a LabVIEW program. Measurements have been made on hot solid and molten uranium dioxide and binary uranium dioxide-zirconium dioxide compositions. PMID:27475566
NASA Astrophysics Data System (ADS)
Weber, J. K. R.; Tamalonis, A.; Benmore, C. J.; Alderman, O. L. G.; Sendelbach, S.; Hebden, A.; Williamson, M. A.
2016-07-01
An aerodynamic levitator with carbon dioxide laser beam heating was integrated with a hermetically sealed controlled atmosphere chamber and sample handling mechanism. The system enabled containment of radioactive samples and control of the process atmosphere chemistry. The chamber was typically operated at a pressure of approximately 0.9 bars to ensure containment of the materials being processed. Samples 2.5-3 mm in diameter were levitated in flowing gas to achieve containerless conditions. Levitated samples were heated to temperatures of up to 3500 °C with a partially focused carbon dioxide laser beam. Sample temperature was measured using an optical pyrometer. The sample environment was integrated with a high energy (100 keV) x-ray synchrotron beamline to enable in situ structure measurements to be made on levitated samples as they were heated, melted, and supercooled. The system was controlled from outside the x-ray beamline hutch by using a LabVIEW program. Measurements have been made on hot solid and molten uranium dioxide and binary uranium dioxide-zirconium dioxide compositions.
Lewis Structures Technology, 1988. Volume 1: Structural Dynamics
NASA Technical Reports Server (NTRS)
1988-01-01
The specific purpose of the symposium was to familiarize the engineering structures community with the depth and range of research performed by the Structures Division of the Lewis Research Center and its academic and industrial partners. Sessions covered vibration control, fracture mechanics, ceramic component reliability, parallel computing, nondestructive testing, dynamical systems, fatigue and damage, wind turbines, hot section technology, structural mechanics codes, computational methods for dynamics, structural optimization, and applications of structural dynamics.
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
Research in Structures and Dynamics, 1984
NASA Technical Reports Server (NTRS)
Hayduk, R. J. (Compiler); Noor, A. K. (Compiler)
1984-01-01
A symposium on advanced and trends in structures and dynamics was held to communicate new insights into physical behavior and to identify trends in the solution procedures for structures and dynamics problems. Pertinent areas of concern were (1) multiprocessors, parallel computation, and database management systems, (2) advances in finite element technology, (3) interactive computing and optimization, (4) mechanics of materials, (5) structural stability, (6) dynamic response of structures, and (7) advanced computer applications.
Future Computer Requirements for Computational Aerodynamics
NASA Technical Reports Server (NTRS)
1978-01-01
Recent advances in computational aerodynamics are discussed as well as motivations for and potential benefits of a National Aerodynamic Simulation Facility having the capability to solve fluid dynamic equations at speeds two to three orders of magnitude faster than presently possible with general computers. Two contracted efforts to define processor architectures for such a facility are summarized.
Surface structure determines dynamic wetting
Wang, Jiayu; Do-Quang, Minh; Cannon, James J.; Yue, Feng; Suzuki, Yuji; Amberg, Gustav; Shiomi, Junichiro
2015-01-01
Liquid wetting of a surface is omnipresent in nature and the advance of micro-fabrication and assembly techniques in recent years offers increasing ability to control this phenomenon. Here, we identify how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. We reveal that the roughness influence can be quantified in terms of a line friction coefficient for the energy dissipation rate at the contact line, and that this can be described in a simple formula in terms of the geometrical parameters of the roughness and the line-friction coefficient of the planar surface. We further identify a criterion to predict if the spreading will be controlled by this surface roughness or by liquid inertia. Our results point to the possibility of selectively controlling the wetting behavior by engineering the surface structure. PMID:25683872
Combustion fume structure and dynamics
Flagan, R.C.
1992-08-01
The focus of this research program is on elucidating the fundamental processes that determine the particle size distribution, composition, and agglomerate structures of coal ash fumes. The ultimate objective of this work is the development and validation of a model for the dynamics of combustion fumes, describing both the evolution of the particle size distribution and the particle morphology. The study employs model systems to address the fundamental questions and to provide rigorous validation of the models to be developed. This first phase of the project has been devoted to the development of a detailed experimental strategy that will allow agglomerates with a broad range of fractal dimensions to be studied in the laboratory. (VC)
Structural Dynamics and Control Interaction of Flexible Structures
NASA Technical Reports Server (NTRS)
Ryan, Robert S. (Editor); Scofield, Harold N. (Editor)
1987-01-01
A workshop on structural dynamics and control interaction of flexible structures was held to promote technical exchange between the structural dynamics and control disciplines, foster joint technology, and provide a forum for discussing and focusing critical issues in the separate and combined areas. Issues and areas of emphasis were identified in structure-control interaction for the next generation of flexible systems.
Resolution of structural heterogeneity in dynamic crystallography
Ren, Zhong; Chan, Peter W. Y.; Moffat, Keith; Pai, Emil F.; Royer, William E.; Šrajer, Vukica; Yang, Xiaojing
2013-01-01
Dynamic behavior of proteins is critical to their function. X-ray crystallography, a powerful yet mostly static technique, faces inherent challenges in acquiring dynamic information despite decades of effort. Dynamic ‘structural changes’ are often indirectly inferred from ‘structural differences’ by comparing related static structures. In contrast, the direct observation of dynamic structural changes requires the initiation of a biochemical reaction or process in a crystal. Both the direct and the indirect approaches share a common challenge in analysis: how to interpret the structural heterogeneity intrinsic to all dynamic processes. This paper presents a real-space approach to this challenge, in which a suite of analytical methods and tools to identify and refine the mixed structural species present in multiple crystallographic data sets have been developed. These methods have been applied to representative scenarios in dynamic crystallography, and reveal structural information that is otherwise difficult to interpret or inaccessible using conventional methods. PMID:23695239
Unsteady Aerodynamic Model Tuning for Precise Flutter Prediction
NASA Technical Reports Server (NTRS)
Pak, Chan-gi
2011-01-01
A simple method for an unsteady aerodynamic model tuning is proposed in this study. This method is based on the direct modification of the aerodynamic influence coefficient matrices. The aerostructures test wing 2 flight-test data is used to demonstrate the proposed model tuning method. The flutter speed margin computed using only the test validated structural dynamic model can be improved using the additional unsteady aerodynamic model tuning, and then the flutter speed margin requirement of 15 percent in military specifications can apply towards the test validated aeroelastic model. In this study, unsteady aerodynamic model tunings are performed at two time invariant flight conditions, at Mach numbers of 0.390 and 0.456. When the Mach number for the unsteady aerodynamic model tuning approaches to the measured fluttering Mach number, 0.502, at the flight altitude of 9,837 ft, the estimated flutter speed is approached to the measured flutter speed at this altitude. The minimum flutter speed difference between the estimated and measured flutter speed is -0.14 percent.
NASA Astrophysics Data System (ADS)
Nield, Joanna; Bryant, Robert; Wiggs, Giles; King, James; Thomas, David; Eckardt, Frank; Washington, Richard
2015-04-01
Salt pans (or playas) are common in arid environments and can be major sources of windblown mineral dust, but there are uncertainties associated with their dust emission potential. These landforms typically form crusts which modify both their erosivity and erodibility by limiting sediment availability, modifying surface and aerodynamic roughness and limiting evaporation rates and sediment production. Here we show the relationship between seasonal surface moisture change and crust pattern development on part of the Makgadikgadi Pans of Botswana (a Southern Hemisphere playa that emits significant dust), based on both remote-sensing and field surface and atmospheric measurements. We use high resolution (sub-cm) terrestrial laser scanning (TLS) surveys over weekly, monthly and annual timescales to accurately characterise crustal ridge thrusting and collapse. Ridge development can change surface topography as much as 30 mm/week on fresh pan areas that have recently been reset by flooding. The corresponding change aerodynamic roughness can be as much as 3 mm/week. At the same time, crack densities across the surface increase and this raises the availability of erodible fluffy, low density dust source sediment stored below the crust layer. We present a conceptual model accounting for the driving forces (subsurface, surface and atmospheric moisture) and feedbacks between these and surface shape that lead to crust pattern trajectories between highly emissive degraded surfaces and less emissive ridged or continuous crusts. These findings improve our understanding of temporal changes in dust availability and supply from playa source regions.
Pickup, B.A.; Thomson, S.L.
2012-01-01
The influence of asymmetric vocal fold stiffness on voice production was evaluated using life-sized, self-oscillating vocal fold models with an idealized geometry based on the human vocal folds. The models were fabricated using flexible, materially-linear silicone compounds with Young’s modulus values comparable to that of vocal fold tissue. The models included a two-layer design to simulate the vocal fold layered structure. The respective Young’s moduli of elasticity of the “left” and “right” vocal fold models were varied to create asymmetric conditions. High-speed videokymography was used to measure maximum vocal fold excursion, vibration frequency, and left-right phase shift, all of which were significantly influenced by asymmetry. Onset pressure, a measure of vocal effort, increased with asymmetry. Particle image velocimetry (PIV) analysis showed significantly greater skewing of the glottal jet in the direction of the stiffer vocal fold model. Potential applications to various clinical conditions are mentioned, and suggestions for future related studies are presented. PMID:19664777
Structural dynamics analyses testing and correlation
NASA Technical Reports Server (NTRS)
Caughey, T. K.
1982-01-01
Some aspects of the lack of close correlation between the predictions of analytical modeling of dynamic structures and the results of vibration tests on such structures are examined. Ways in which the correlation may be improved are suggested.
Error Location in Structural Dynamic Model of a Rocket Structure
NASA Astrophysics Data System (ADS)
Sundararajan, T.; Sam, C.
2012-06-01
Structural dynamic characteristics of the aerospace structures are essential to obtain the structural responses due to dynamic loads during its mission. The structural dynamic parameters of the aerospace structures are frequencies, associated mode shape and damping. Usually finite element (FE) model of the aerospace structures are generated to estimate the frequencies and the associated mode shape. These FE models are validated by modal survey/ground resonance tests to ensure its completeness and correctness. The modeling deficiencies, if any, in these FE models have to be corrected. This paper describes the method to locate the FE modeling errors using residual force method.
NASA Technical Reports Server (NTRS)
Curlett, Brian P.
1991-01-01
The aerodynamic effects of fillet size in a low speed compressor cascade were experimentally studied. Two blade profiles were used during the experiment, namely a controlled diffusion blade and a double circular arc blade. Cascades were tested with three fillet radii and two boundary layer thicknesses over a large range of incidence angles. The cascade performance was determined by extensive downstream flow measurements using a two head, 5 hole pressure probe. Results differ significantly between the two types of blades tested. As fillet radius increases secondary flows and total pressure losses were found to increase for the controlled diffusion blades; whereas, for the double circular arc blades the losses decrease, particularly at high incidence angles.
Structural dynamics branch research and accomplishments
NASA Technical Reports Server (NTRS)
1990-01-01
Summaries are presented of fiscal year 1989 research highlights from the Structural Dynamics Branch at NASA Lewis Research Center. Highlights from the branch's major work areas include aeroelasticity, vibration control, dynamic systems, and computation structural methods. A listing of the fiscal year 1989 branch publications is given.
NASA Technical Reports Server (NTRS)
Whitlow, Jr., Woodrow (Editor); Todd, Emily N. (Editor)
1999-01-01
The proceedings of a workshop sponsored by the Confederation of European Aerospace Societies (CEAS), the American Institute of Aeronautics and Astronautics (AIAA), the National Aeronautics and Space Administration (NASA), Washington, D.C., and the Institute for Computer Applications in Science and Engineering (ICASE), Hampton, Virginia, and held in Williamsburg, Virginia June 22-25, 1999 represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft.
Aerodynamic Control using Distributed Active Bleed
NASA Astrophysics Data System (ADS)
Kearney, John; Glezer, Ari
2015-11-01
The global aerodynamic loads on a stationary and pitching airfoil at angles of attack beyond the static and dynamic stall margins, respectively are controlled in wind tunnel experiments using regulated distributed bleed driven by surface pressure differences. High-speed PIV and proper orthogonal decomposition of the vorticity flux on the static airfoil show that the bleed engenders trains of discrete vortices that advect along the surface and are associated with a local instability that is manifested by a time-averaged bifurcation of the vorticity layer near the bleed outlets and alters the vorticity flux over the airfoil and thereby the aerodynamic loads. Active bleed is used on a dynamically pitching airfoil (at reduced frequencies up to k = 0.42) to modulate the evolution of vorticity concentrations during dynamic stall. Time-periodic bleed improved the pitch stability by reducing adverse pitching moment (``negative damping'') that can precipitate structural instabilities. At the same time, the maintains the cycle-average loads to within 5% of the base flow levels by segmenting the vorticity layer during upstroke and promoting early flow attachment during downstroke segments of the pitch cycle. Supported by Georgia Tech VLRCOE.
Research in structures, structural dynamics and materials, 1989
NASA Technical Reports Server (NTRS)
Hunter, William F. (Compiler); Noor, Ahmed K. (Compiler)
1989-01-01
Topics addressed include: composite plates; buckling predictions; missile launch tube modeling; structural/control systems design; optimization of nonlinear R/C frames; error analysis for semi-analytic displacement; crack acoustic emission; and structural dynamics.
Structure and dynamics of complex liquid water: Molecular dynamics simulation
NASA Astrophysics Data System (ADS)
S, Indrajith V.; Natesan, Baskaran
2015-06-01
We have carried out detailed structure and dynamical studies of complex liquid water using molecular dynamics simulations. Three different model potentials, namely, TIP3P, TIP4P and SPC-E have been used in the simulations, in order to arrive at the best possible potential function that could reproduce the structure of experimental bulk water. All the simulations were performed in the NVE micro canonical ensemble using LAMMPS. The radial distribution functions, gOO, gOH and gHH and the self diffusion coefficient, Ds, were calculated for all three models. We conclude from our results that the structure and dynamical parameters obtained for SPC-E model matched well with the experimental values, suggesting that among the models studied here, the SPC-E model gives the best structure and dynamics of bulk water.
Structural Biology by NMR: Structure, Dynamics, and Interactions
Markwick, Phineus R. L.; Malliavin, Thérèse; Nilges, Michael
2008-01-01
The function of bio-macromolecules is determined by both their 3D structure and conformational dynamics. These molecules are inherently flexible systems displaying a broad range of dynamics on time-scales from picoseconds to seconds. Nuclear Magnetic Resonance (NMR) spectroscopy has emerged as the method of choice for studying both protein structure and dynamics in solution. Typically, NMR experiments are sensitive both to structural features and to dynamics, and hence the measured data contain information on both. Despite major progress in both experimental approaches and computational methods, obtaining a consistent view of structure and dynamics from experimental NMR data remains a challenge. Molecular dynamics simulations have emerged as an indispensable tool in the analysis of NMR data. PMID:18818721
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.
Dynamical symmetries in nuclear structure
Casten, R.F.
1986-01-01
In recent years the concept of dynamical symmetries in nuclei has witnessed a renaissance of interest and activity. Much of this work has been developed in the context of the Interacting Boson Approximation (or IBA) model. The appearance and properties of dynamical symmetries in nuclei will be reviewed, with emphasis on their characteristic signatures and on the role of the proton-neutron interaction in their formation, systematics and evolution. 36 refs., 20 figs.
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.
Predicting protein dynamics from structural ensembles
NASA Astrophysics Data System (ADS)
Copperman, J.; Guenza, M. G.
2015-12-01
The biological properties of proteins are uniquely determined by their structure and dynamics. A protein in solution populates a structural ensemble of metastable configurations around the global fold. From overall rotation to local fluctuations, the dynamics of proteins can cover several orders of magnitude in time scales. We propose a simulation-free coarse-grained approach which utilizes knowledge of the important metastable folded states of the protein to predict the protein dynamics. This approach is based upon the Langevin Equation for Protein Dynamics (LE4PD), a Langevin formalism in the coordinates of the protein backbone. The linear modes of this Langevin formalism organize the fluctuations of the protein, so that more extended dynamical cooperativity relates to increasing energy barriers to mode diffusion. The accuracy of the LE4PD is verified by analyzing the predicted dynamics across a set of seven different proteins for which both relaxation data and NMR solution structures are available. Using experimental NMR conformers as the input structural ensembles, LE4PD predicts quantitatively accurate results, with correlation coefficient ρ = 0.93 to NMR backbone relaxation measurements for the seven proteins. The NMR solution structure derived ensemble and predicted dynamical relaxation is compared with molecular dynamics simulation-derived structural ensembles and LE4PD predictions and is consistent in the time scale of the simulations. The use of the experimental NMR conformers frees the approach from computationally demanding simulations.
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.
14 CFR 25.445 - Auxiliary aerodynamic surfaces.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Auxiliary aerodynamic surfaces. 25.445... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Control Surface and System Loads § 25.445 Auxiliary aerodynamic surfaces. (a) When significant, the aerodynamic influence...
14 CFR 25.445 - Auxiliary aerodynamic surfaces.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Auxiliary aerodynamic surfaces. 25.445... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Control Surface and System Loads § 25.445 Auxiliary aerodynamic surfaces. (a) When significant, the aerodynamic influence...
NASA Astrophysics Data System (ADS)
Fein, Howard
1999-07-01
Holographic Interferometry has been successfully employed to characterize the materials and behavior of diverse types of structures under stress. Specialized variations of this technology have also been applied to define dynamic and vibration related structural behavior. Such applications of holographic technique offer some of the most effective methods of modal and dynamic analysis available. Real-time dynamic testing of the structural behavior of aerodynamic control and airfoil structures for advanced aircraft and missile systems has traditionally required advanced instrumentation for data collection in either actual flight test or wind-tunnel simulations. Advanced optical holography techniques are alternate methods which result in full-field behavioral data on the ground in a nondestructive hardware- in-the-loop environment. These methods offer significant insight in both the development and subsequent operational test and modeling of advanced control and airfoil structures and their integration with total vehicle system dynamics. Aerodynamic control structures and components can be analyzed in place with very low amplitude excitation and the resultant data can be used to adjust the accuracy of mathematically derived structural and behavioral models as well actual performance.
Aerodynamic design on high-speed trains
NASA Astrophysics Data System (ADS)
Ding, San-San; Li, Qiang; Tian, Ai-Qin; Du, Jian; Liu, Jia-Li
2016-01-01
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.
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.
SSME structural dynamic model development
NASA Technical Reports Server (NTRS)
Foley, M. J.; Tilley, D. M.; Welch, C. T.
1983-01-01
A mathematical model of the Space Shuttle Main Engine (SSME) as a complete assembly, with detailed emphasis on LOX and High Fuel Turbopumps is developed. The advantages of both complete engine dynamics, and high fidelity modeling are incorporated. Development of this model, some results, and projected applications are discussed.
Structural Dynamic Behavior of Wind Turbines
NASA Technical Reports Server (NTRS)
Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III
2009-01-01
The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).
Active Control of Aerodynamic Noise Sources
NASA Technical Reports Server (NTRS)
Reynolds, Gregory A.
2001-01-01
Aerodynamic noise sources become important when propulsion noise is relatively low, as during aircraft landing. Under these conditions, aerodynamic noise from high-lift systems can be significant. The research program and accomplishments described here are directed toward reduction of this aerodynamic noise. Progress toward this objective include correction of flow quality in the Low Turbulence Water Channel flow facility, development of a test model and traversing mechanism, and improvement of the data acquisition and flow visualization capabilities in the Aero. & Fluid Dynamics Laboratory. These developments are described in this report.
Unsteady Aerodynamic Model Tuning for Precise Flutter Prediction
NASA Technical Reports Server (NTRS)
Pak, Chan-Gi
2011-01-01
A simple method for an unsteady aerodynamic model tuning is proposed in this study. This method is based on the direct modification of the aerodynamic influence coefficient matrices. The aerostructures test wing 2 flight-test data is used to demonstrate the proposed model tuning method. The flutter speed margin computed using only the test validated structural dynamic model can be improved using the additional unsteady aerodynamic model tuning, and then the flutter speed margin requirement of 15 % in military specifications can apply towards the test validated aeroelastic model. In this study, unsteady aerodynamic model tunings are performed at two time invariant flight conditions, at Mach numbers of 0.390 and 0.456. When the Mach number for the unsteady model tuning approaches to the measured fluttering Mach number, 0.502, at the flight altitude of 9,837 ft, the estimated flutter speed is approached to the measured flutter speed at this altitude. The minimum flutter speed difference between the estimated and measured flutter speed is -.14 %.
Evolutionary dynamics in set structured populations
Tarnita, Corina E.; Antal, Tibor; Ohtsuki, Hisashi; Nowak, Martin A.
2009-01-01
Evolutionary dynamics are strongly affected by population structure. The outcome of an evolutionary process in a well-mixed population can be very different from that in a structured population. We introduce a powerful method to study dynamical population structure: evolutionary set theory. The individuals of a population are distributed over sets. Individuals interact with others who are in the same set. Any 2 individuals can have several sets in common. Some sets can be empty, whereas others have many members. Interactions occur in terms of an evolutionary game. The payoff of the game is interpreted as fitness. Both the strategy and the set memberships change under evolutionary updating. Therefore, the population structure itself is a consequence of evolutionary dynamics. We construct a general mathematical approach for studying any evolutionary game in set structured populations. As a particular example, we study the evolution of cooperation and derive precise conditions for cooperators to be selected over defectors. PMID:19433793
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.
Aerodynamic effects of flexibility in flapping wings
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
From structure to function, via dynamics
NASA Astrophysics Data System (ADS)
Stetter, O.; Soriano, J.; Geisel, T.; Battaglia, D.
2013-01-01
Neurons in the brain are wired into a synaptic network that spans multiple scales, from local circuits within cortical columns to fiber tracts interconnecting distant areas. However, brain function require the dynamic control of inter-circuit interactions on time-scales faster than synaptic changes. In particular, strength and direction of causal influences between neural populations (described by the so-called directed functional connectivity) must be reconfigurable even when the underlying structural connectivity is fixed. Such directed functional influences can be quantified resorting to causal analysis of time-series based on tools like Granger Causality or Transfer Entropy. The ability to quickly reorganize inter-areal interactions is a chief requirement for performance in a changing natural environment. But how can manifold functional networks stem "on demand" from an essentially fixed structure? We explore the hypothesis that the self-organization of neuronal synchronous activity underlies the control of brain functional connectivity. Based on simulated and real recordings of critical neuronal cultures in vitro, as well as on mean-field and spiking network models of interacting brain areas, we have found that "function follows dynamics", rather than structure. Different dynamic states of a same structural network, characterized by different synchronization properties, are indeed associated to different functional digraphs (functional multiplicity). We also highlight the crucial role of dynamics in establishing a structure-to-function link, by showing that whenever different structural topologies lead to similar dynamical states, than the associated functional connectivities are also very similar (structural degeneracy).
Dynamic Structures through Microdifferential Holography
Sharnoff, Mark; Brehm, Lawrence P.; Henry, Richard W.
1986-01-01
The principles of microdifferential holography are developed primarily from nonmathematical argument, and the method's capabilities are compared with those of x-ray and optical diffraction. Microdifferential holography is very sensitive to small displacements of strongly scattering elements of a specimen whether or not they can be optically resolved. We present and interpret differential images of electrical activity of neurons and of contractile activity of isolated skeletal fibers. The latter confirm the suggestion of earlier work that the dynamic regions of contracting muscle are organized along myofibrillar segments rather than by sarcomeres. ImagesFIGURE 2FIGURE 3FIGURE 4FIGURE 5FIGURE 6FIGURE 7 PMID:19431634
Aerodynamic characteristics of airplanes at high angles of attack
NASA Technical Reports Server (NTRS)
Chambers, J. R.; Grafton, S. B.
1977-01-01
An introduction to, and a broad overiew of, the aerodynamic characteristics of airplanes at high angles of attack are provided. Items include: (1) some important fundamental phenomena which determine the aerodynamic characteristics of airplanes at high angles of attack; (2) static and dynamic aerodynamic characteristics near the stall; (3) aerodynamics of the spin; (4) test techniques used in stall/spin studies; (5) applications of aerodynamic data to problems in flight dynamics in the stall/spin area; and (6) the outlook for future research in the area. Although stalling and spinning are flight dynamic problems of importance to all aircraft, including general aviation aircraft, commercial transports, and military airplanes, emphasis is placed on military configurations and the principle aerodynamic factors which influence the stability and control of such vehicles at high angles of attack.
NASA Technical Reports Server (NTRS)
McGowan, Anna-Maria Rivas; Wilkie, W. Keats; Moses, Robert W.; Lake, Renee C.; Florance, Jennifer Pinkerton; Wieseman, Carol D.; Reaves, Mercedes C.; Taleghani, Barmac K.; Mirick, Paul H.; Wilbur, Matthew L.
1998-01-01
An overview of smart structures research currently underway at the NASA Langley Research Center in the areas of aeroservoelasticity and structural dynamics is presented. Analytical and experimental results, plans, potential technology pay-offs, and challenges are discussed. The goal of this research is to develop the enabling technologies to actively and passively control aircraft and rotorcraft vibration and loads using smart devices. These enabling technologies and related research efforts include developing experimentally-validated finite element and aeroservoelastic modeling techniques; conducting bench experimental tests to assess feasibility and understand system trade-offs; and conducting large-scale wind- tunnel tests to demonstrate system performance. The key aeroservoelastic applications of this research include: active twist control of rotor blades using interdigitated electrode piezoelectric composites and active control of flutter, and gust and buffeting responses using discrete piezoelectric patches. In addition, NASA Langley is an active participant in the DARPA/ Air Force Research Laboratory/ NASA/ Northrop Grumman Smart Wing program which is assessing aerodynamic performance benefits using smart materials. Keywords: aeroelasticity, smart structures, piezoelectric actuators, active fiber composites, rotorcraft, buffet load alleviation, individual blade control, aeroservoelasticity, shape memory alloys, damping augmentation, piezoelectric power consumption
VDAC Structure, Selectivity, and Dynamics
Colombini, Marco
2012-01-01
VDAC channels exist in the mitochondrial outer membrane of all eukaryotic organisms. Of the different isoforms present in one organism, it seems that one of these is the canonical VDAC whose properties and 3D structure is highly conserved. The fundamental role of these channels is to control the flux of metabolites between the cytosol and mitochondrial spaces. Based on many functional studies, the fundamental structure of the pore wall consists of one α helix and 13 β strands tilted at a 46° angle. This results in a pore with an estimated internal diameter of 2.5 nm. This structure has not yet been resolved. The published 3D structure consists of 19 β strands and is different from the functional structure that forms voltage-gated channels. The selectivity of the channel is exquisite, being able to select for ATP over molecules of the same size and charge. Voltage gating involves two separate gating processes. The mechanism involves the translocation of a positively charged portion of the wall of the channel to the membrane surface resulting in a reduction in pore diameter and volume and an inversion in ion selectivity. This mechanism is consistent with experiments probing changes in selectivity, voltage gating, kinetics and energetics. Other published mechanisms are in conflict with experimental results. PMID:22240010
Structure and Dynamics of Polymer nanocomposite hydrogels
NASA Astrophysics Data System (ADS)
Xu, Di; Rafailovich, Miriam; Gersappe, Dilip
2013-03-01
Polymer hydrogels are widely used in fields like food science, tissue engineering and drug delivery. A lot of research has focused on developing hydrogels with novel properties. However, a lack of understanding of the dynamics and structure of the hydrogel has become a big obstacle. We use molecular dynamic simulations, which provide a direct observation of gel formation and gel structures, to study the local structural and dynamic properties of hydrogels. Our work focuses on using coarse-graining molecule dynamic simulations to study physically linked polymer nano-composite hydrogels. Our goal is to study how the aspect ratio and shape of the nanofiller introduced to the hydrogel can lead to different mechanical behavior. Our simulation looks at the effects of polymer species, chain length, and water content and the effect on the mechanical properties of the hydrogel.
Dynamic and Structural Gas Turbine Engine Modeling
NASA Technical Reports Server (NTRS)
Turso, James A.
2003-01-01
Model the interactions between the structural dynamics and the performance dynamics of a gas turbine engine. Generally these two aspects are considered separate, unrelated phenomena and are studied independently. For diagnostic purposes, it is desirable to bring together as much information as possible, and that involves understanding how performance is affected by structural dynamics (if it is) and vice versa. This can involve the relationship between thrust response and the excitation of structural modes, for instance. The job will involve investigating and characterizing these dynamical relationships, generating a model that incorporates them, and suggesting and/or developing diagnostic and prognostic techniques that can be incorporated in a data fusion system. If no coupling is found, at the least a vibration model should be generated that can be used for diagnostics and prognostics related to blade loss, for instance.
Evolutionary dynamics of taxonomic structure
Foote, Michael
2012-01-01
The distribution of species among genera and higher taxa has largely untapped potential to reveal among-clade variation in rates of origination and extinction. The probability distribution of the number of species within a genus is modelled with a stochastic, time-homogeneous birth–death model having two parameters: the rate of species extinction, μ, and the rate of genus origination, γ, each scaled as a multiple of the rate of within-genus speciation, λ. The distribution is more sensitive to γ than to μ, although μ affects the size of the largest genera. The species : genus ratio depends strongly on both γ and μ, and so is not a good diagnostic of evolutionary dynamics. The proportion of monotypic genera, however, depends mainly on γ, and so may provide an index of the genus origination rate. Application to living marine molluscs of New Zealand shows that bivalves have a higher relative rate of genus origination than gastropods. This is supported by the analysis of palaeontological data. This concordance suggests that analysis of living taxonomic distributions may allow inference of macroevolutionary dynamics even without a fossil record. PMID:21865239
Structure/load dependent vectors for linear structural dynamic analysis
NASA Technical Reports Server (NTRS)
Qin, Jiangning; Nguyen, Duc T.
1992-01-01
The dynamic solution vectors yielded by the present structure/load dependent-vectors method for large-scale linear structural dynamic analyses involving complex loadings can be used as starting vectors, so that both structure and load characteristics are encompassed by the basis vectors. The method is shown to entail fewer vectors than current alternatives for a given level of accuracy, especially in the cases of structures that have external concentrated masses. Numerical results are presented which illustrate the advantages of this dependent-vectors method relative to other reduction methods.
Dynamic Structure of Plasma Fibronectin
Maurer, Lisa M.; Ma, Wenjiang; Mosher, Deane F.
2016-01-01
Fibronectin is a large vertebrate glycoprotein that is found in soluble and insoluble forms and involved in diverse processes. Protomeric fibronectin is a dimer of subunits, each of which comprises 29 to 31 modules—12 type I, two type II, and 15-17 type III. Plasma fibronectin is secreted by hepatocytes and circulates in a compact conformation before it binds to cell surfaces, converts to an extended conformation, and is assembled into fibronectin fibrils. Here we review biophysical and structural studies that have shed light on how plasma fibronectin transitions from the compact to the extended conformation. The three types of modules each have a well-organized secondary and tertiary structure as defined by NMR and crystallography and have been likened to “beads on a string”. There are flexible sequences in the N-terminal tail, between the fifth and sixth type I modules, between the first two and last two of the type III modules, and at the C-terminus. Several specific module-module interactions have been identified that likely maintain the compact quaternary structure of circulating fibronectin. The quaternary structure is perturbed in response to binding events, including binding of fibronectin to the surface of vertebrate cells for fibril assembly and to bacterial adhesins. PMID:27185500
On Dynamics of Spinning Structures
NASA Technical Reports Server (NTRS)
Gupta, K. K.; Ibrahim, A.
2012-01-01
This paper provides details of developments pertaining to vibration analysis of gyroscopic systems, that involves a finite element structural discretization followed by the solution of the resulting matrix eigenvalue problem by a progressive, accelerated simultaneous iteration technique. Thus Coriolis, centrifugal and geometrical stiffness matrices are derived for shell and line elements, followed by the eigensolution details as well as solution of representative problems that demonstrates the efficacy of the currently developed numerical procedures and tools.
Structural dynamics payload loads estimates
NASA Technical Reports Server (NTRS)
Engels, R. C.
1982-01-01
Methods for the prediction of loads on large space structures are discussed. Existing approaches to the problem of loads calculation are surveyed. A full scale version of an alternate numerical integration technique to solve the response part of a load cycle is presented, and a set of short cut versions of the algorithm developed. The implementation of these techniques using the software package developed is discussed.
Dynamic adaptivity of "smart" piezoelectric structures
NASA Astrophysics Data System (ADS)
Tzou, Horn-Sen; Zhong, Jianping P.
1990-10-01
Active smart" space and machine structures with adaptive dynamic characteristics have long been interested in a variety of high-performance systems, e.g., flexible robots, flexible space structures, "smart" machines, etc. In this paper, an active adaptive structure made of piezoelectric materials is proposed and evaluated. The structural adaptivity is achieved by a voltage feedback (open or closed loops) utilizing the converse piezoelectric effect. A mathematical model is proposed and the electrodynamic equations of motion and the generalized boundary conditions of a generic piezoelectric shell subjected to mechanical and electrical excitations are derived using Hamilton's principle and the linear piezoelectric theory. The dynamic adaptivity of the structure is introduced using a feedback control system. The theory is demonstrated in a case study in which the structural adaptivity (natural frequency) is investigated.
Dynamic Structural Health Monitoring of Slender Structures Using Optical Sensors
Antunes, Paulo; Travanca, Rui; Rodrigues, Hugo; Melo, José; Jara, José; Varum, Humberto; André, Paulo
2012-01-01
In this paper we summarize the research activities at the Instituto de Telecomunicações—Pólo de Aveiro and University of Aveiro, in the field of fiber Bragg grating based sensors and their applications in dynamic measurements for Structural Health Monitoring of slender structures such as towers. In this work we describe the implementation of an optical biaxial accelerometer based on fiber Bragg gratings inscribed on optical fibers. The proof-of-concept was done with the dynamic monitoring of a reinforced concrete structure and a slender metallic telecommunication tower. Those structures were found to be suitable to demonstrate the feasibility of FBG accelerometers to obtain the structures' natural frequencies, which are the key parameters in Structural Health Monitoring and in the calibration of numerical models used to simulate the structure behavior. PMID:22778661
NASA Astrophysics Data System (ADS)
Noor, Ahmed K.; Venneri, Samuel L.
Various papers on flight vehicle materials, structures, and dynamics are presented. Individual topics addressed include: general modeling methods, component modeling techniques, time-domain computational techniques, dynamics of articulated structures, structural dynamics in rotating systems, structural dynamics in rotorcraft, damping in structures, structural acoustics, structural design for control, structural modeling for control, control strategies for structures, system identification, overall assessment of needs and benefits in structural dynamics and controlled structures. Also discussed are: experimental aeroelasticity in wind tunnels, aeroservoelasticity, nonlinear aeroelasticity, aeroelasticity problems in turbomachines, rotary-wing aeroelasticity with application to VTOL vehicles, computational aeroelasticity, structural dynamic testing and instrumentation.
NASA Technical Reports Server (NTRS)
Hahne, David E. (Editor)
1999-01-01
NASA's High-Speed Research Program sponsored the 1999 Aerodynamic Performance Technical Review on February 8-12, 1999 in Anaheim, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in the areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High Lift, and Flight Controls. The review objectives were to: (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working on HSCT aerodynamics. In particular, single and midpoint optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented, along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program. This Volume 1/Part 1 publication covers configuration aerodynamics.
Program of Research in Structures and Dynamics
NASA Technical Reports Server (NTRS)
1988-01-01
The Structures and Dynamics Program was first initiated in 1972 with the following two major objectives: to provide a basic understanding and working knowledge of some key areas pertinent to structures, solid mechanics, and dynamics technology including computer aided design; and to provide a comprehensive educational and research program at the NASA Langley Research Center leading to advanced degrees in the structures and dynamics areas. During the operation of the program the research work was done in support of the activities of both the Structures and Dynamics Division and the Loads and Aeroelasticity Division. During the period of 1972 to 1986 the Program provided support for two full-time faculty members, one part-time faculty member, three postdoctoral fellows, one research engineer, eight programmers, and 28 graduate research assistants. The faculty and staff of the program have published 144 papers and reports, and made 70 presentations at national and international meetings, describing their research findings. In addition, they organized and helped in the organization of 10 workshops and national symposia in the structures and dynamics areas. The graduate research assistants and the students enrolled in the program have written 20 masters theses and 2 doctoral dissertations. The overall progress is summarized.
Rocket/launcher structural dynamics
NASA Technical Reports Server (NTRS)
Ferragut, N. J.
1976-01-01
The equations of motion describing the interactions between a rocket and a launcher were derived using Lagrange's Equation. A rocket launching was simulated. The motions of both the rocket and the launcher can be considered in detail. The model contains flexible elements and rigid elements. The rigid elements (masses) were judiciously utilized to simplify the derivation of the equations. The advantages of simultaneous shoe release were illustrated. Also, the loading history of the interstage structure of a boosted configuration was determined. The equations shown in this analysis could be used as a design tool during the modification of old launchers and the design of new launchers.
NASA Technical Reports Server (NTRS)
Nissim, E.
1989-01-01
The aerodynamic energy method is used in this paper to synthesize control laws for NASA's Drone for Aerodynamic and Structural Testing-Aerodynamic Research Wing 1 (DAST-ARW1) mathematical model. The performance of these control laws in terms of closed-loop flutter dynamic pressure, control surface activity, and robustness is compared against other control laws that appear in the literature and relate to the same model. A control law synthesis technique that makes use of the return difference singular values is developed in this paper. it is based on the aerodynamic energy approach and is shown to yield results superior to those given in the literature and based on optimal control theory. Nyquist plots are presented together with a short discussion regarding the relative merits of the minimum singular value as a measure of robustness, compared with the more traditional measure of robustness involving phase and gain margins.
NASA Technical Reports Server (NTRS)
Nissim, Eli
1990-01-01
The aerodynamic energy method is used to synthesize control laws for NASA's drone for aerodynamic and structural testing-aerodynamic research wing 1 (DAST-ARW1) mathematical model. The performance of these control laws in terms of closed-loop flutter dynamic pressure, control surface activity, and robustness is compared with other control laws that relate to the same model. A control law synthesis technique that makes use of the return difference singular values is developed. It is based on the aerodynamic energy approach and is shown to yield results that are superior to those results given in the literature and are based on optimal control theory. Nyquist plots are presented, together with a short discussion regarding the relative merits of the minimum singular value as a measure of robustness as compared with the more traditional measure involving phase and gain margins.
Dynamics of adaptive structures: Design through simulations
NASA Technical Reports Server (NTRS)
Park, K. C.; Alexander, S.
1993-01-01
The use of a helical bi-morph actuator/sensor concept by mimicking the change of helical waveform in bacterial flagella is perhaps the first application of bacterial motions (living species) to longitudinal deployment of space structures. However, no dynamical considerations were analyzed to explain the waveform change mechanisms. The objective is to review various deployment concepts from the dynamics point of view and introduce the dynamical considerations from the outset as part of design considerations. Specifically, the impact of the incorporation of the combined static mechanisms and dynamic design considerations on the deployment performance during the reconfiguration stage is studied in terms of improved controllability, maneuvering duration, and joint singularity index. It is shown that intermediate configurations during articulations play an important role for improved joint mechanisms design and overall structural deployability.
Submesoscale dynamics and planktonic community structure
NASA Astrophysics Data System (ADS)
Franks, P. J.; Taniguchi, D. A.
2012-12-01
The vertical velocities associated with submesoscale dynamics occur on time scales that are resonant with planktonic growth and grazing rates. This resonance may cause submesoscale dynamics to be disproportionately important to planktonic productivity and carbon sequestration. To investigate the role of submesoscale motions on planktonic community structure, we used a continuum size-structured planktonic ecosystem model. The model is based on a traditional NPZ framework, but allows for size dependence of all biological processes. The model was carefully parameterized with data from the literature, and reproduces realistic planktonic size spectra. Perturbing the model with a nutrient pulse similar to that driven by submesoscale upwelling leads to significant perturbations to the ecosystem. Pulses of enhanced biomass propagate from small to large organisms over time scales of days to weeks. We explore the model stability and dynamics, and their dependence on the parameter values, to gain understanding of the potential for submesoscale physical motions to influence planktonic ecosystem dynamics.
Structural dynamics of liganded myoglobin
Frauenfelder, H.; Petsko, G.A.
1980-10-01
X-ray crystallography can reveal the magnitudes and principal directions of the mean-square displacements of every atom in a protein. This structural information is complementary to the temporal information obtainable by spectroscopic techniques such as nuclear magnetic resonance. Determination of the temperature dependence of the mean-square displacements makes it possible to separate large conformational motions from simple thermal vibrations. The contribution of crystal lattice disorder to the overall apparent displacement can be estimated by Moessbauer spectroscopy. This technique has been applied to high resolution x-ray diffraction data from sperm whale myoglobin in its Met iron and oxy cobalt forms. Both crystal structures display regions of large conformational motions, particularly at the chain termini and in the region of the proximal histidine. Overall, the mean-square displacement increases with increasing distance from the center of gravity of the molecule. Some regions of the heme pocket in oxy cobalt myoglobin are more rigid than the corresponding regions in Met myoglobin.
NASA Technical Reports Server (NTRS)
Heeg, Jennifer; Dowell, Earl H.
2001-01-01
Discrete time aeroelastic models with explicitly retained aerodynamic modes have been generated employing a time marching vortex lattice aerodynamic model. This paper presents analytical results from eigenanalysis of these models. The potential of these models to calculate the behavior of modes that represent damped system motion (noncritical modes) in addition to the simple harmonic modes is explored. A typical section with only structural freedom in pitch is examined. The eigenvalues are examined and compared to experimental data. Issues regarding the convergence of the solution with regard to refining the aerodynamic discretization are investigated. Eigenvector behavior is examined; the eigenvector associated with a particular eigenvalue can be viewed as the set of modal participation factors for that particular mode. For the present formulation of the equations of motion, the vorticity for each aerodynamic element appears explicitly as an element of each eigenvector in addition to the structural dynamic generalized coordinates. Thus, modal participation of the aerodynamic degrees of freedom can be assessed in M addition to participation of structural degrees of freedom.
NASA Technical Reports Server (NTRS)
McGowan, Anna-Maria Rivas; Wilkie, W. Keats; Moses, Robert W.; Lake, Renee C.; Florance, Jennifer Pinkerton; Wieseman, Carol D.; Reaves, Mercedes C.; Taleghani, Barmac K.; Mirick, Paul H.; Wilbur, Mathew L.
1997-01-01
An overview of smart structures research currently underway at the NASA Langley Research Center in the areas of aeroservoelasticity and structural dynamics is presented. Analytical and experimental results, plans, potential technology pay-offs, and challenges are discussed. The goal of this research is to develop the enabling technologies to actively and passively control aircraft and rotorcraft vibration and loads using smart devices. These enabling technologies and related research efforts include developing experimentally-validated finite element and aeroservoelastic modeling techniques; conducting bench experimental tests to assess feasibility and understand system trade-offs; and conducting large-scale wind tunnel tests to demonstrate system performance. The key aeroservoelastic applications of this research include: active twist control of rotor blades using interdigitated electrode piezoelectric composites and active control of flutter, and gust and buffeting responses using discrete piezoelectric patches. In addition, NASA Langley is an active participant in the DARPA/Air Force Research Laboratory/NASA/Northrop Grumman Smart Wing program which is assessing aerodynamic performance benefits using smart materials.
Structure and dynamics of biphasic colloidal mixtures.
Mohraz, Ali; Weeks, Eric R; Lewis, Jennifer A
2008-06-01
We investigate the structure and dynamics of biphasic colloidal mixtures composed of coexisting attractive and repulsive microspheres by confocal microscopy. Attractive gels formed in the presence of repulsive microspheres are more spatially homogeneous and, on average, are both more locally tenuous and have fewer large voids than their unary counterparts. The repulsive microspheres within these mixtures display heterogeneous dynamics, with some species exhibiting freely diffusive Brownian motion while others are trapped within the gel network during aggregation. PMID:18643205
Development of Unsteady Aerodynamic and Aeroelastic Reduced-Order Models Using the FUN3D Code
NASA Technical Reports Server (NTRS)
Silva, Walter A.; Vatsa, Veer N.; Biedron, Robert T.
2009-01-01
Recent significant improvements to the development of CFD-based unsteady aerodynamic reduced-order models (ROMs) are implemented into the FUN3D unstructured flow solver. These improvements include the simultaneous excitation of the structural modes of the CFD-based unsteady aerodynamic system via a single CFD solution, minimization of the error between the full CFD and the ROM unsteady aero- dynamic solution, and computation of a root locus plot of the aeroelastic ROM. Results are presented for a viscous version of the two-dimensional Benchmark Active Controls Technology (BACT) model and an inviscid version of the AGARD 445.6 aeroelastic wing using the FUN3D code.
Origin and Structure of Dynamic Cooperative Networks
Wardil, Lucas; Hauert, Christoph
2014-01-01
Societies are built on social interactions among individuals. Cooperation represents the simplest form of a social interaction: one individual provides a benefit to another one at a cost to itself. Social networks represent a dynamical abstraction of social interactions in a society. The behaviour of an individual towards others and of others towards the individual shape the individual's neighbourhood and hence the local structure of the social network. Here we propose a simple theoretical framework to model dynamic social networks by focussing on each individual's actions instead of interactions between individuals. This eliminates the traditional dichotomy between the strategy of individuals and the structure of the population and easily complements empirical studies. As a consequence, altruists, egoists and fair types are naturally determined by the local social structures, while globally egalitarian networks or stratified structures arise. Cooperative interactions drive the emergence and shape the structure of social networks. PMID:25030202
Origin and Structure of Dynamic Cooperative Networks
NASA Astrophysics Data System (ADS)
Wardil, Lucas; Hauert, Christoph
2014-07-01
Societies are built on social interactions among individuals. Cooperation represents the simplest form of a social interaction: one individual provides a benefit to another one at a cost to itself. Social networks represent a dynamical abstraction of social interactions in a society. The behaviour of an individual towards others and of others towards the individual shape the individual's neighbourhood and hence the local structure of the social network. Here we propose a simple theoretical framework to model dynamic social networks by focussing on each individual's actions instead of interactions between individuals. This eliminates the traditional dichotomy between the strategy of individuals and the structure of the population and easily complements empirical studies. As a consequence, altruists, egoists and fair types are naturally determined by the local social structures, while globally egalitarian networks or stratified structures arise. Cooperative interactions drive the emergence and shape the structure of social networks.
Strength of concrete structures under dynamic loading
NASA Astrophysics Data System (ADS)
Kumpyak, O. G.; Galyautdinov, Z. R.; Kokorin, D. N.
2016-01-01
The use of elastic supports is one the efficient methods of decreasing the dynamic loading. The paper describes the influence of elastic supports on the stress-strain state of steel concrete structures exposed to one-time dynamic loading resulting in failure. Oblique bending beams on elastic supports and their elastic, elastoplastic, and elastoplastic consolidation behavior are considered in this paper. For numerical calculations the developed computer program is used based on the finite element method. Research findings prove high efficiency of elastic supports under dynamic loading conditions. The most effective behavior of elastic supports is demonstrated at the elastoplastic stage. A good agreement is observed between the theoretical and experimental results.
Dynamics and structure of energetic displacement cascades
Averback, R.S.; Diaz de la Rubia, T.; Benedek, R.
1987-12-01
This paper summarizes recent progress in the understanding of energetic displacement cascades and the primary state of damage in metals. On the theoretical side, the availability of supercomputers has greatly enhanced our ability to simulate cascades by molecular dynamics. Recent application of this simulation technique to Cu and Ni provides new insight into the dynamics of cascade processes. On the experimental side, new data on ion beam mixing and in situ electron microscopy studies of ion damage at low temperatures reveal the role of the thermodynamic properties of the material on cascade dynamics and structure. 38 refs., 9 figs.
Space station structures and dynamics test program
NASA Technical Reports Server (NTRS)
Bugg, Frank M.; Ivey, E. W.; Moore, C. J.; Townsend, John S.
1987-01-01
The design, construction, and operation of a low-Earth orbit space station poses challenges for development and implementation of technology. One specific challenge is the development of a dynamics test program for defining the space station design requirements, and identifying and characterizing phenomena affecting the space station's design and development. The test proposal, as outlined, is a comprehensive structural dynamics program to be launched in support of the space station (SS). Development of a parametric data base and verification of the mathematical models and analytical analysis tools necessary for engineering support of the station's design, construction, and operation provide the impetus for the dynamics test program. The four test phases planned are discussed: testing of SS applicable structural concepts; testing of SS prototypes; testing of actual SS structural hardware; and on-orbit testing of SS construction.
Aerodynamic Database Development for Mars Smart Lander Vehicle Configurations
NASA Technical Reports Server (NTRS)
Bobskill, Glenn J.; Parikh, Paresh C.; Prabhu, Ramadas K.; Tyler, Erik D.
2002-01-01
An aerodynamic database has been generated for the Mars Smart Lander Shelf-All configuration using computational fluid dynamics (CFD) simulations. Three different CFD codes, USM3D and FELISA, based on unstructured grid technology and LAURA, an established and validated structured CFD code, were used. As part of this database development, the results for the Mars continuum were validated with experimental data and comparisons made where applicable. The validation of USM3D and LAURA with the Unitary experimental data, the use of intermediate LAURA check analyses, as well as the validation of FELISA with the Mach 6 CF(sub 4) experimental data provided a higher confidence in the ability for CFD to provide aerodynamic data in order to determine the static trim characteristics for longitudinal stability. The analyses of the noncontinuum regime showed the existence of multiple trim angles of attack that can be unstable or stable trim points. This information is needed to design guidance controller throughout the trajectory.
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.
Aerodynamic Shape Optimization Based on Free-form Deformation
NASA Technical Reports Server (NTRS)
Samareh, Jamshid A.
2004-01-01
This paper presents a free-form deformation technique suitable for aerodynamic shape optimization. Because the proposed technique is independent of grid topology, we can treat structured and unstructured computational fluid dynamics grids in the same manner. The proposed technique is an alternative shape parameterization technique to a trivariate volume technique. It retains the flexibility and freedom of trivariate volumes for CFD shape optimization, but it uses a bivariate surface representation. This reduces the number of design variables by an order of magnitude, and it provides much better control for surface shape changes. The proposed technique is simple, compact, and efficient. The analytical sensitivity derivatives are independent of the design variables and are easily computed for use in a gradient-based optimization. The paper includes the complete formulation and aerodynamics shape optimization results.
Protein crowding affects hydration structure and dynamics
Harada, Ryuhei; Sugita, Yuji; Feig, Michael
2012-01-01
The effect of protein crowding on the structure and dynamics of water was examined from explicit solvent molecular dynamics simulations of a series of protein G and protein G/villin systems at different protein concentrations. Hydration structure was analyzed in terms of radial distribution functions, three-dimensional hydration sites, and preservation of tetrahedral coordination. Analysis of hydration dynamics focused on self-diffusion rates and dielectric constants as a function of crowding. The results show significant changes in both structure and dynamics of water under highly crowded conditions. The structure of water is altered mostly beyond the first solvation shell. Diffusion rates and dielectric constants are significantly reduced following linear trends as a function of crowding reflecting highly constrained water in crowded environments. The reduced dynamics of diffusion is expected to be strongly related to hydrodynamic properties of crowded cellular environments while the reduced dielectric constant under crowded conditions has implications for the stability of biomolecules in crowded environments. The results from this study suggest a prescription for modeling solvation in simulations of cellular environments. PMID:22352398
Aerodynamic analysis of Pegasus - Computations vs reality
NASA Technical Reports Server (NTRS)
Mendenhall, Michael R.; Lesieutre, Daniel J.; Whittaker, C. H.; Curry, Robert E.; Moulton, Bryan
1993-01-01
Pegasus, a three-stage, air-launched, winged space booster was developed to provide fast and efficient commercial launch services for small satellites. The aerodynamic design and analysis of Pegasus was conducted without benefit of wind tunnel tests using only computational aerodynamic and fluid dynamic methods. Flight test data from the first two operational flights of Pegasus are now available, and they provide an opportunity to validate the accuracy of the predicted pre-flight aerodynamic characteristics. Comparisons of measured and predicted flight characteristics are presented and discussed. Results show that the computational methods provide reasonable aerodynamic design information with acceptable margins. Post-flight analyses illustrate certain areas in which improvements are desired.
NASA Astrophysics Data System (ADS)
Terekhov, V. I.; Bogatko, T. V.
2016-06-01
The results of a numerical study of the influence of the thicknesses of dynamic and thermal boundary layers on turbulent separation and heat transfer in a tube with sudden expansion are presented. The first part of this work studies the influence of the thickness of the dynamic boundary layer, which was varied by changing the length of the stabilization area within the maximal extent possible: from zero to half of the tube diameter. In the second part of the study, the flow before separation was hydrodynamically stabilized and the thermal layer before the expansion could simultaneously change its thickness from 0 to D1/2. The Reynolds number was varied in the range of {Re}_{{{{D}}1 }} = 6.7 \\cdot 103 {{to}} 1.33 \\cdot 105 , and the degree of tube expansion remained constant at ER = (D 2/D 1)2 = 1.78. A significant effect of the thickness of the separated boundary layer on both dynamic and thermal characteristics of the flow is shown. In particular, it was found out that with an increase in the thickness of the boundary layer the recirculation zone increases and the maximal Nusselt number decreases. It was determined that the growth of the heat layer thickness does not affect the hydrodynamic characteristics of the flow after separation but does lead to a reduction of heat transfer intensity in the separation area and removal of the coordinates of maximal heat transfer from the point of tube expansion. The generalizing dependence for the maximal Nusselt number at various thermal layer thicknesses is given. Comparison with experimental data confirmed the main trends in the behavior of heat and mass transfer processes in separated flows behind a step with different thermal prehistories.
Chemical structure and dynamics: Annual report 1993
Colson, S.D.
1994-07-01
The Chemical Structure and Dynamics program responds to the need for a fundamental, molecular-level understanding of chemistry at the wide variety of environmentally-important interfaces. The research program is built around the established relationship between structure, thermodynamics, and kinetics. This research effort continues to evolve into a program of rigorous studies of fundamental molecular processes in model systems (e.g., well-characterized surfaces, single-component solutions, clusters, and biological molecules), and studies of complex systems found in the environment. Experimental studies of molecular and supramolecular structures and thermodynamics are key to understanding the nature of matter, and lead to direct comparison with computational results. Kinetic and mechanistic measurements, combined with real-time dynamics measurements of atomic and molecular motions during chemical reactions, provide for a molecular-level description of chemical reactions. The anticipated results of this work are the achievement of a quantitative understanding of chemical processes at complex interfaces, the development of new techniques for the detection and measurement of species at such interfaces, and the interpretation and extrapolation of the observations in terms of models of interfacial chemistry. The Chemical Structure and Dynamics research program includes five areas described in detail in this report: Reaction mechanisms at solid interfaces; Solution and solution interfaces; Structure and dynamics of biological systems; Analytical methods development; and atmospheric chemistry. Extended abstracts are presented for 23 studies.
Multiscale structure in eco-evolutionary dynamics
NASA Astrophysics Data System (ADS)
Stacey, Blake C.
In a complex system, the individual components are neither so tightly coupled or correlated that they can all be treated as a single unit, nor so uncorrelated that they can be approximated as independent entities. Instead, patterns of interdependency lead to structure at multiple scales of organization. Evolution excels at producing such complex structures. In turn, the existence of these complex interrelationships within a biological system affects the evolutionary dynamics of that system. I present a mathematical formalism for multiscale structure, grounded in information theory, which makes these intuitions quantitative, and I show how dynamics defined in terms of population genetics or evolutionary game theory can lead to multiscale organization. For complex systems, "more is different," and I address this from several perspectives. Spatial host--consumer models demonstrate the importance of the structures which can arise due to dynamical pattern formation. Evolutionary game theory reveals the novel effects which can result from multiplayer games, nonlinear payoffs and ecological stochasticity. Replicator dynamics in an environment with mesoscale structure relates to generalized conditionalization rules in probability theory. The idea of natural selection "acting at multiple levels" has been mathematized in a variety of ways, not all of which are equivalent. We will face down the confusion, using the experience developed over the course of this thesis to clarify the situation.
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.
Switchable and Tunable Aerodynamic Drag on Cylinders
NASA Astrophysics Data System (ADS)
Guttag, Mark; Lopez Jimenez, Francisco; Reis, Pedro
2015-11-01
We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, which are thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.
Switchable and Tunable Aerodynamic Drag on Cylinders
NASA Astrophysics Data System (ADS)
Guttag, Mark; Lopéz Jiménez, Francisco; Upadhyaya, Priyank; Kumar, Shanmugam; Reis, Pedro
We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.
Recent advances in structural dynamics of large space structures
NASA Technical Reports Server (NTRS)
Pinson, Larry D.
1987-01-01
Recent progress in the area of structural dynamics of large space structures is reviewed. Topics include system identification, large angle slewing of flexible structures, definition of scaling limitations in structural models, and recent results on a tension-stabilized antenna concept known as the hoop-column. Increasingly complex laboratory experiments guide most of the activities leading to realistic technological developments. Theoretical progress in system identification based on system realization theory resulting in unification of several methods is reviewed. Experimental results from implementation of a theoretical large-angle slewing control approach are shown. Status and results of the development of a research computer program for analysis of the transient dynamics of large angle motion of flexible structures are presented. Correlation of results from analysis and vibration tests of the hoop-column antenna concepts are summarized.
Recent advances in structural dynamics of large space structures
NASA Technical Reports Server (NTRS)
Pinson, Larry D.
1987-01-01
Recent progress in the area of structural dynamics of large space structures is reviewed. Topics include system identification, large angle slewing of flexible structures, definition of scaling limitations in structural models, and recent results on a tension-stabilized antenna concept known as the hoop-column. Increasingly complex laboratory experiments guide most of the activities leading to realistic technological developments. Theoretical progress in system identification based on system realization theory resulting in unification of several methods is reviewed. Experimental results from implementation of a theoretical large-angle slewing control approach are shown. Status and results of the development of a research computer program for analysis of the transient dynamics of large angle motion of flexible structures are presented. Correlation of results from analysis and vibration tests of the hoop-column antenna concept are summarized.
Space station structures and dynamics test program
NASA Technical Reports Server (NTRS)
Moore, Carleton J.; Townsend, John S.; Ivey, Edward W.
1987-01-01
The design, construction, and operation of a low-Earth orbit space station poses unique challenges for development and implementation of new technology. The technology arises from the special requirement that the station be built and constructed to function in a weightless environment, where static loads are minimal and secondary to system dynamics and control problems. One specific challenge confronting NASA is the development of a dynamics test program for: (1) defining space station design requirements, and (2) identifying the characterizing phenomena affecting the station's design and development. A general definition of the space station dynamic test program, as proposed by MSFC, forms the subject of this report. The test proposal is a comprehensive structural dynamics program to be launched in support of the space station. The test program will help to define the key issues and/or problems inherent to large space structure analysis, design, and testing. Development of a parametric data base and verification of the math models and analytical analysis tools necessary for engineering support of the station's design, construction, and operation provide the impetus for the dynamics test program. The philosophy is to integrate dynamics into the design phase through extensive ground testing and analytical ground simulations of generic systems, prototype elements, and subassemblies. On-orbit testing of the station will also be used to define its capability.
Dynamic based damage detection in composite structures
NASA Astrophysics Data System (ADS)
Banerjee, Sauvik; Ricci, Fabrizio; Baid, Harsh; Mal, Ajit K.
2009-03-01
Advanced composites are being used increasingly in state-of-the-art aircraft and aerospace structures. In spite of their many advantages, composite materials are highly susceptible to hidden flaws that may occur at any time during the life cycle of a structure, and if undetected, may cause sudden and catastrophic failure of the entire structure. This paper is concerned with the detection and characterization of hidden defects in composite structures before they grow to a critical size. A methodology for automatic damage identification and localization is developed using a combination of vibration and wave propagation data. The structure is assumed to be instrumented with an array of actuators and sensors to excite and record its dynamic response, including vibration and wave propagation effects. A damage index, calculated from the measured dynamical response of the structure in a previous (reference) state and the current state, is introduced as a determinant of structural damage. The indices are used to identify low velocity impact damages in increasingly complex composite structural components. The potential application of the approach in developing health monitoring systems in defects-critical structures is indicated.
Aerodynamic Noise Generated by Shinkansen Cars
NASA Astrophysics Data System (ADS)
KITAGAWA, T.; NAGAKURA, K.
2000-03-01
The noise value (A -weighted sound pressure level, SLOW) generated by Shinkansen trains, now running at 220-300 km/h, should be less than 75 dB(A) at the trackside. Shinkansen noise, such as rolling noise, concrete support structure noise, and aerodynamic noise are generated by various parts of Shinkansen trains. Among these aerodynamic noise is important because it is the major contribution to the noise generated by the coaches running at high speed. In order to reduce the aerodynamic noise, a number of improvements to coaches have been made. As a result, the aerodynamic noise has been reduced, but it still remains significant. In addition, some aerodynamic noise generated from the lower parts of cars remains. In order to investigate the contributions of these noises, a method of analyzing Shinkansen noise has been developed and applied to the measured data of Shinkansen noise at speeds between 120 and 315 km/h. As a result, the following conclusions have been drawn: (1) Aerodynamic noise generated from the upper parts of cars was reduced considerably by smoothing car surfaces. (2) Aerodynamic noise generated from the lower parts of cars has a major influence upon the wayside noise.
Algorithms and software for nonlinear structural dynamics
NASA Technical Reports Server (NTRS)
Belytschko, Ted; Gilbertsen, Noreen D.; Neal, Mark O.
1989-01-01
The objective of this research is to develop efficient methods for explicit time integration in nonlinear structural dynamics for computers which utilize both concurrency and vectorization. As a framework for these studies, the program WHAMS, which is described in Explicit Algorithms for the Nonlinear Dynamics of Shells (T. Belytschko, J. I. Lin, and C.-S. Tsay, Computer Methods in Applied Mechanics and Engineering, Vol. 42, 1984, pp 225 to 251), is used. There are two factors which make the development of efficient concurrent explicit time integration programs a challenge in a structural dynamics program: (1) the need for a variety of element types, which complicates the scheduling-allocation problem; and (2) the need for different time steps in different parts of the mesh, which is here called mixed delta t integration, so that a few stiff elements do not reduce the time steps throughout the mesh.
Experimental research on structural dynamics and control
NASA Technical Reports Server (NTRS)
Montgomery, R. C.; Horner, G. C.; Cole, S. R.
1981-01-01
This report describes an apparatus at the NASA Langley Research Center for conducting research on dynamics and control of structural dynamics systems. The apparatus consists of a 3.66 m (12 ft.) long flexible beam to which are attached four electromagnetic actuators, nine noncontacting sensors to measure deflection of beam at various locations, and four strain gage type load cells one at each actuator attachment point. The important feature of the apparatus is that the actuators can be controlled and deflection and load sensor data can be processed in real time using the research centers CDC Cyber 175 computer system - thereby allowing research to be conducted on structural dynamics systems using advanced control laws. The facility is described in the report along with a detailed discussion of the actuators used.
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.
Computation of dragonfly aerodynamics
NASA Astrophysics Data System (ADS)
Gustafson, Karl; Leben, Robert
1991-04-01
Dragonflies are seen to hover and dart, seemingly at will and in remarkably nimble fashion, with great bursts of speed and effectively discontinuous changes of direction. In their short lives, their gossamer flight provides us with glimpses of an aerodynamics of almost extraterrestrial quality. Here we present the first computer simulations of such aerodynamics.
Proteins with Novel Structure, Function and Dynamics
NASA Technical Reports Server (NTRS)
Pohorille, Andrew
2014-01-01
Recently, a small enzyme that ligates two RNA fragments with the rate of 10(exp 6) above background was evolved in vitro (Seelig and Szostak, Nature 448:828-831, 2007). This enzyme does not resemble any contemporary protein (Chao et al., Nature Chem. Biol. 9:81-83, 2013). It consists of a dynamic, catalytic loop, a small, rigid core containing two zinc ions coordinated by neighboring amino acids, and two highly flexible tails that might be unimportant for protein function. In contrast to other proteins, this enzyme does not contain ordered secondary structure elements, such as alpha-helix or beta-sheet. The loop is kept together by just two interactions of a charged residue and a histidine with a zinc ion, which they coordinate on the opposite side of the loop. Such structure appears to be very fragile. Surprisingly, computer simulations indicate otherwise. As the coordinating, charged residue is mutated to alanine, another, nearby charged residue takes its place, thus keeping the structure nearly intact. If this residue is also substituted by alanine a salt bridge involving two other, charged residues on the opposite sides of the loop keeps the loop in place. These adjustments are facilitated by high flexibility of the protein. Computational predictions have been confirmed experimentally, as both mutants retain full activity and overall structure. These results challenge our notions about what is required for protein activity and about the relationship between protein dynamics, stability and robustness. We hypothesize that small, highly dynamic proteins could be both active and fault tolerant in ways that many other proteins are not, i.e. they can adjust to retain their structure and activity even if subjected to mutations in structurally critical regions. This opens the doors for designing proteins with novel functions, structures and dynamics that have not been yet considered.
DISCOS- DYNAMIC INTERACTION SIMULATION OF CONTROLS AND STRUCTURES (IBM VERSION)
NASA Technical Reports Server (NTRS)
Frisch, H. P.
1994-01-01
deployment, analysis of multispin satellites, and analysis of large, highly flexible satellites, including the design of attitude-control systems. The overall approach of DISCOS is unique in that any member body of the system may be flexible, and the system is not restricted to a topological tree configuration. The equations of motion are developed using the most general form of Lagrange's equations, including auxiliary nonholonomic rehenomic conditions of constraint. Lagrange multipliers are used as interaction forces/ torques to maintain prescribed constraints. Nonlinear flexible/rigid dynamic coupling effects are accounted for in unabridged fashion for individual bodies and for the total system. Elastic deformation can be represented by normal vibration modes or by any adequate series of Rayleigh functions, including 'quasi-static' displacement functions. To 'solve' Lagrange's equations of motion, the explicit form of the kinetic and potential energy functions, the dissipation function, and the form of the transformation relating ordinary Cartesian position coordinates to the generalized coordinates must be defined. The potential energy and dissipation functions for a structure are determined with standard finite-element techniques by the NASTRAN program. In order to use the computed functions, the Lagrange's equations and the system kinematic constraint equations are expressed in matrix format. These differential matrix equations are solved numerically by the DISCOS program. Provisions are included for environmental loading of the structure (spacecraft), including solar pressure, gravity gradient, and aerodynamic drag. Input to DISCOS includes topological and geometrical descriptions of the structure under analysis, initial conditions, control system descriptions, and NASTRAN-derived structural matrices. Specialized routines are supplied that read the input data and redimension the DISCOS programs to minimize core requirements. Output includes an extensive list of
Dynamic object management for distributed data structures
NASA Technical Reports Server (NTRS)
Totty, Brian K.; Reed, Daniel A.
1992-01-01
In distributed-memory multiprocessors, remote memory accesses incur larger delays than local accesses. Hence, insightful allocation and access of distributed data can yield substantial performance gains. The authors argue for the use of dynamic data management policies encapsulated within individual distributed data structures. Distributed data structures offer performance, flexibility, abstraction, and system independence. This approach is supported by data from a trace-driven simulation study of parallel scientific benchmarks. Experimental data on memory locality, message count, message volume, and communication delay suggest that data-structure-specific data management is superior to a single, system-imposed policy.
Nonlinear problems in flight dynamics
NASA Technical Reports Server (NTRS)
Chapman, G. T.; Tobak, M.
1984-01-01
A comprehensive framework is proposed for the description and analysis of nonlinear problems in flight dynamics. Emphasis is placed on the aerodynamic component as the major source of nonlinearities in the flight dynamic system. Four aerodynamic flows are examined to illustrate the richness and regularity of the flow structures and the nature of the flow structures and the nature of the resulting nonlinear aerodynamic forces and moments. A framework to facilitate the study of the aerodynamic system is proposed having parallel observational and mathematical components. The observational component, structure is described in the language of topology. Changes in flow structure are described via bifurcation theory. Chaos or turbulence is related to the analogous chaotic behavior of nonlinear dynamical systems characterized by the existence of strange attractors having fractal dimensionality. Scales of the flow are considered in the light of ideas from group theory. Several one and two degree of freedom dynamical systems with various mathematical models of the nonlinear aerodynamic forces and moments are examined to illustrate the resulting types of dynamical behavior. The mathematical ideas that proved useful in the description of fluid flows are shown to be similarly useful in the description of flight dynamic behavior.
NASA Technical Reports Server (NTRS)
McMillin, S. Naomi (Editor)
1999-01-01
NASA's High-Speed Research Program sponsored the 1998 Aerodynamic Performance Technical Review on February 9-13, in Los Angeles, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High-Lift, and Flight Controls. The review objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working HSCT aerodynamics. In particular, single and multi-point optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program.
NASA Technical Reports Server (NTRS)
Hahne, David E. (Editor)
1999-01-01
NASA's High-Speed Research Program sponsored the 1999 Aerodynamic Performance Technical Review on February 8-12, 1999 in Anaheim, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in the areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High Lift, and Flight Controls. The review objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working on HSCT aerodynamics. In particular, single and midpoint optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented, along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program. This Volume 1/Part 2 publication covers the design optimization and testing sessions.
NASA Technical Reports Server (NTRS)
McMillin, S. Naomi (Editor)
1999-01-01
NASA's High-Speed Research Program sponsored the 1998 Aerodynamic Performance Technical Review on February 9-13, in Los Angeles, California. The review was designed to bring together NASA and industry HighSpeed Civil Transport (HSCT) Aerodynamic Performance technology development participants in areas of. Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High-Lift, and Flight Controls. The review objectives were to: (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working HSCT aerodynamics. In particular, single and multi-point optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program.
Creating a Test Validated Structural Dynamic Finite Element Model of the X-56A Aircraft
NASA Technical Reports Server (NTRS)
Pak, Chan-Gi; Truong, Samson
2014-01-01
Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the Multi Utility Technology Test-bed, X-56A aircraft, is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground vibration test-validated structural dynamic finite element model of the X-56A aircraft is created in this study. The structural dynamic finite element model of the X-56A aircraft is improved using a model tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, while other properties such as center of gravity location, total weight, and offdiagonal terms of the mass orthogonality matrix were used as constraints. The end result was a more improved and desirable structural dynamic finite element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.
Dynamic structural disorder in supported nanoscale catalysts
Rehr, J. J.; Vila, F. D.
2014-04-07
We investigate the origin and physical effects of “dynamic structural disorder” (DSD) in supported nano-scale catalysts. DSD refers to the intrinsic fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to bulk materials, nano-scale systems exhibit substantial fluctuations in structure, charge, temperature, and other quantities, as well as large surface effects. The DSD is driven largely by the stochastic librational motion of the center of mass and fluxional bonding at the nanoparticle surface due to thermal coupling with the substrate. Our approach for calculating and understanding DSD is based on a combination of real-time density functional theory/molecular dynamics simulations, transient coupled-oscillator models, and statistical mechanics. This approach treats thermal and dynamic effects over multiple time-scales, and includes bond-stretching and -bending vibrations, and transient tethering to the substrate at longer ps time-scales. Potential effects on the catalytic properties of these clusters are briefly explored. Model calculations of molecule-cluster interactions and molecular dissociation reaction paths are presented in which the reactant molecules are adsorbed on the surface of dynamically sampled clusters. This model suggests that DSD can affect both the prefactors and distribution of energy barriers in reaction rates, and thus can significantly affect catalytic activity at the nano-scale.
Dynamic structural disorder in supported nanoscale catalysts.
Rehr, J J; Vila, F D
2014-04-01
We investigate the origin and physical effects of "dynamic structural disorder" (DSD) in supported nano-scale catalysts. DSD refers to the intrinsic fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to bulk materials, nano-scale systems exhibit substantial fluctuations in structure, charge, temperature, and other quantities, as well as large surface effects. The DSD is driven largely by the stochastic librational motion of the center of mass and fluxional bonding at the nanoparticle surface due to thermal coupling with the substrate. Our approach for calculating and understanding DSD is based on a combination of real-time density functional theory/molecular dynamics simulations, transient coupled-oscillator models, and statistical mechanics. This approach treats thermal and dynamic effects over multiple time-scales, and includes bond-stretching and -bending vibrations, and transient tethering to the substrate at longer ps time-scales. Potential effects on the catalytic properties of these clusters are briefly explored. Model calculations of molecule-cluster interactions and molecular dissociation reaction paths are presented in which the reactant molecules are adsorbed on the surface of dynamically sampled clusters. This model suggests that DSD can affect both the prefactors and distribution of energy barriers in reaction rates, and thus can significantly affect catalytic activity at the nano-scale. PMID:24712802
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
Research in Structures, Structural Dynamics and Materials, 1990
NASA Technical Reports Server (NTRS)
Barthelemy, Jean-Francois M. (Compiler); Noor, Ahmed K. (Compiler)
1990-01-01
The Structural Dynamics and Materials (SDM) Conference was held on April 2 to 4, 1990 in Long Beach, California. This publication is a compilation of presentations of the work-in-progress sessions and does not contain papers from the regular sessions since those papers are published by AIAA in the conference proceedings.
Structural Dynamics and Control Interaction of Flexible Structures
NASA Technical Reports Server (NTRS)
Ryan, Robert S. (Editor); Scofield, Harold N. (Editor)
1987-01-01
A Workshop was held to promote technical exchange between the structural dynamic and control disciplines, foster joint technology, and provide a forum for discussing and focusing critical issues in the separate and combined areas. The workshop was closed by a panel meeting. Panel members' viewpoints and their responses to questions are included.
Aerodynamic Performance Enhancement of a Finite Span Wind Turbine Blade using Synthetic Jets
NASA Astrophysics Data System (ADS)
Taylor, Keith; Leong, Chia Min; Amitay, Michael
2011-11-01
Modern wind turbines undergo significant changes in pitch angle and structural loading through a revolution. Recent developments in flow control techniques, coupled with increased interest in green energy technologies, have led to interest in applying these techniques to wind turbines, in an effort to increase power output and reduce structural stress associated with widely varying loading. This reduction in structural stress could lead to reduced operational costs associated with the maintenance cycle. The effect of active flow control on the aerodynamic and structural aspects of finite span blade was investigated experimentally. When synthetic jets were employed the effect on aerodynamic performance and structural vibrations, during static and dynamic pitch conditions, was significant. In order to investigate if the jets can be actuated for less time (reduce their power consumption), they were actuated during only a portion of the pitch cycle or using pulse modulation. The results showed that these techniques result in significant reduction in the hysteresis loop and the structural vibrations.
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.
NASA Technical Reports Server (NTRS)
Pak, Chan-Gi; Truong, Samson S.
2014-01-01
Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of Multi Utility Technology Test Bed, X-56A, aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of X-56A. The ground vibration test validated structural dynamic finite element model of the X-56A is created in this study. The structural dynamic finite element model of the X-56A is improved using a model tuning tool. In this study, two different weight configurations of the X-56A have been improved in a single optimization run.
The aerodynamics of propellers
NASA Astrophysics Data System (ADS)
Wald, Quentin R.
2006-02-01
The theory and the design of propellers of minimum induced loss is treated. The pioneer analysis of this problem was presented more than half a century ago by Theodorsen, but obscurities in his treatment and inaccuracies and limited coverage in his tables of the Goldstein circulation function for helicoidal vortex sheets have not been remedied until the present work which clarifies and extends his work. The inverse problem, the prediction of the performance of a given propeller of arbitrary form, is also treated. The theory of propellers of minimum energy loss is dependent on considerations of a regular helicoidal trailing vortex sheet; consequently, a more detailed discussion of the dynamics of vortex sheets and the consequences of their instability and roll up is presented than is usually found in treatments of propeller aerodynamics. Complete and accurate tables of the circulation function are presented. Interference effects between a fuselage or a nacelle and the propeller are considered. The regimes of propeller, vortex ring, and windmill operation are characterized.
The structure and dynamics of multilayer networks
NASA Astrophysics Data System (ADS)
Boccaletti, S.; Bianconi, G.; Criado, R.; del Genio, C. I.; Gómez-Gardeñes, J.; Romance, M.; Sendiña-Nadal, I.; Wang, Z.; Zanin, M.
2014-11-01
In the past years, network theory has successfully characterized the interaction among the constituents of a variety of complex systems, ranging from biological to technological, and social systems. However, up until recently, attention was almost exclusively given to networks in which all components were treated on equivalent footing, while neglecting all the extra information about the temporal- or context-related properties of the interactions under study. Only in the last years, taking advantage of the enhanced resolution in real data sets, network scientists have directed their interest to the multiplex character of real-world systems, and explicitly considered the time-varying and multilayer nature of networks. We offer here a comprehensive review on both structural and dynamical organization of graphs made of diverse relationships (layers) between its constituents, and cover several relevant issues, from a full redefinition of the basic structural measures, to understanding how the multilayer nature of the network affects processes and dynamics.
Annual Report 2000. Chemical Structure and Dynamics
Colson, Steven D.; McDowell, Robin S.
2001-04-15
This annual report describes the research and accomplishments of the Chemical Structure and Dynamics Program in the year 2000, one of six research programs at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) - a multidisciplinary, national scientific user facility and research organization. The Chemical Structure and Dynamics (CS&D) program is meeting the need for a fundamental, molecular-level understanding by 1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; 2) developing a multidisciplinary capability for describing interfacial chemical processes relevant to environmental chemistry; and 3) developing state-of-the-art research and analytical methods for characterizing complex materials of the types found in natural and contaminated systems.
Chemical structure and dynamics. Annual report 1995
Colson, S.D.; McDowell, R.S.
1996-05-01
The Chemical Structure and Dynamics program is a major component of Pacific Northwest National Laboratory`s Environmental Molecular Sciences Laboratory (EMSL), providing a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for the characterization of waste tanks and pollutant distributions, and for detection and monitoring of trace atmospheric species.
Annual Report 2000. Chemical Structure and Dynamics
Colson, Steve D; McDowell, Rod S
2001-04-15
This annual report describes the research and accomplishments of the Chemical Structure and Dynamics Program in the year 2000, one of six research programs at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) - a multidisciplinary, national scientific user facility and research organization. The Chemical Structure and Dynamics (CS and D) program is meeting the need for a fundamental, molecular-level understanding by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes relevant to environmental chemistry; and (3) developing state-of-the-art research and analytical methods for characterizing complex materials of the types found in natural and contaminated systems.
Chemical structure and dynamics: Annual report 1996
Colson, S.D.; McDowell, R.S.
1997-03-01
The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing waste tanks and pollutant distributions, and for detecting and monitoring trace atmospheric species.
Nonlinear Response of Composite Panels Under Combined Acoustic Excitation and Aerodynamic Pressure
NASA Technical Reports Server (NTRS)
Abdel-Motagaly, K.; Duan, B.; Mei, C.
1999-01-01
A finite element formulation is presented for the analysis of large deflection response of composite panels subjected to aerodynamic pressure- at supersonic flow and high acoustic excitation. The first-order shear deformation theory is considered for laminated composite plates, and the von Karman nonlinear strain-displacement relations are employed for the analysis of large deflection panel response. The first-order piston theory aerodynamics and the simulated Gaussian white noise are employed for the aerodynamic and acoustic loads, respectively. The nonlinear equations of motion for an arbitrarily laminated composite panel subjected to a combined aerodynamic and acoustic pressures are formulated first in structure node degrees-of-freedom. The system equations are then transformed and reduced to a set of coupled nonlinear equations in modal coordinates. Modal participation is defined and the in-vacuo modes to be retained in the analysis are based on the modal participation values. Numerical results include root mean square values of maximum deflections, deflection and strain response time histories, probability distributions, and power spectrum densities. Results showed that combined acoustic and aerodynamic loads have to be considered for panel analysis and design at high dynamic pressure values.
Space structure (dynamics and control) theme development
NASA Technical Reports Server (NTRS)
Russell, Richard A.; Gates, Richard M.
1988-01-01
A study was made to define the long-range technical objectives and goals for the Space Structure (Dynamics and Control) theme area. The approach was to evaluate ongoing and proposed technology activities such that the technology gaps and voids could be identified. After the technology needs were identified, a set of recommended experimental activities was defined including the technical objectives of each and their relationship.
Structure And Dynamics Of Finite Dust Clouds
Block, D.; Kroll, M.; Arp, O.; Piel, A.; Kaeding, S.; Ivanov, Y.; Melzer, A.; Henning, C.; Baumgartner, H.; Bonitz, M.
2008-09-07
Two novel three-dimensional (3D) diagnostics, stereoscopic imaging and digital holography, enable us to provide a critical comparison of experimental results with simulations and theory and thus to gain a detailed insight into the structural and dynamical properties of strongly coupled dust clouds. Special attention is paid to the influence of screening and the role of metastable states in dust clouds containing just a very few particles.
Impact dynamics research on composite transport structures
NASA Technical Reports Server (NTRS)
Carden, H. D.
1984-01-01
The experimental and analytical efforts being undertaken to investigate the response of composite and aluminum structures under crash loading conditions were reviewed. A Boeing 720 airplane was used in the controlled-impact demonstration test. Energy absorption of composite materials, the tearing of fuselage skin panels, the friction and abrasion behavior of composite skins, and the crushing behavior and dynamic response of composite beams were among the topics addressed.
Impact dynamics research on composite transport structures
NASA Technical Reports Server (NTRS)
Carden, H. D.
1985-01-01
The experimental and analytical efforts being undertaken to investigate the response of composite and aluminum structures under crash loading conditions were reviewed. A Boeing 720 airplane was used in the controlled-impact demonstration test. Energy absorption of composite materials, the tearing of fuselage skin panels, the friction and abrasion behavior of composite skins, and the crushing behavior and dynamic response of composite beams were among the topics addressed.
Patterns and localized structures in population dynamics
NASA Astrophysics Data System (ADS)
Clerc, M. G.; Escaff, D.; Kenkre, V. M.
2005-11-01
Patterns, fronts, and localized structures of a prototypical model for population dynamics interaction are studied. The physical content of the model is the coexistence of a simple random walk for the motion of the individuals with a nonlinearity in the competitive struggle for resources which simultaneously stresses the Allee effect and interaction at a distance. Mathematically, the model is variational and exhibits coexistence between different stable extended states. Solutions are obtained, the phase diagram is constructed, and the emergence of localized structures is investigated.
8B structure in Fermionic Molecular Dynamics
NASA Astrophysics Data System (ADS)
Henninger, K. R.; Neff, T.; Feldmeier, H.
2015-04-01
The structure of the light exotic nucleus 8B is investigated in the Fermionic Molecular Dynamics (FMD) model. The decay of 8B is responsible for almost the entire high- energy solar-neutrino flux, making structure calculations of 8B important for determining the solar core temperature. 8B is a proton halo candidate thought to exhibit clustering. FMD uses a wave-packet basis and is well-suited for modelling clustering and halos. For a multiconfiguration treatment we construct the many-body Hilbert space from antisymmetrised angular-momentum projected 8-particle states. First results show formation of a proton halo.
Dynamic Deployment Simulations of Inflatable Space Structures
NASA Technical Reports Server (NTRS)
Wang, John T.
2005-01-01
The feasibility of using Control Volume (CV) method and the Arbitrary Lagrangian Eulerian (ALE) method in LSDYNA to simulate the dynamic deployment of inflatable space structures is investigated. The CV and ALE methods were used to predict the inflation deployments of three folded tube configurations. The CV method was found to be a simple and computationally efficient method that may be adequate for modeling slow inflation deployment sine the inertia of the inflation gas can be neglected. The ALE method was found to be very computationally intensive since it involves the solving of three conservative equations of fluid as well as dealing with complex fluid structure interactions.
Dynamics of overlapping structures in modular networks.
Almendral, J A; Leyva, I; Li, D; Sendiña-Nadal, I; Havlin, S; Boccaletti, S
2010-07-01
Modularity is a fundamental feature of real networks, being intimately bounded to their functionality, i.e., to their capability of performing parallel tasks in a coordinated way. Although the modular structure of real graphs has been intensively studied, very little is known on the interactions between functional modules of a graph. Here, we present a general method based on synchronization of networking oscillators, that is able to detect overlapping structures in multimodular environments. We furthermore report the full analytical and theoretical description on the relationship between the overlapping dynamics and the underlying network topology. The method is illustrated by means of a series of applications. PMID:20866697
NASA Handbook for Spacecraft Structural Dynamics Testing
NASA Technical Reports Server (NTRS)
Kern, Dennis L.; Scharton, Terry D.
2005-01-01
Recent advances in the area of structural dynamics and vibrations, in both methodology and capability, have the potential to make spacecraft system testing more effective from technical, cost, schedule, and hardware safety points of view. However, application of these advanced test methods varies widely among the NASA Centers and their contractors. Identification and refinement of the best of these test methodologies and implementation approaches has been an objective of efforts by the Jet Propulsion Laboratory on behalf of the NASA Office of the Chief Engineer. But to develop the most appropriate overall test program for a flight project from the selection of advanced methodologies, as well as conventional test methods, spacecraft project managers and their technical staffs will need overall guidance and technical rationale. Thus, the Chief Engineer's Office has recently tasked JPL to prepare a NASA Handbook for Spacecraft Structural Dynamics Testing. An outline of the proposed handbook, with a synopsis of each section, has been developed and is presented herein. Comments on the proposed handbook are solicited from the spacecraft structural dynamics testing community.
Handbook on dynamics of jointed structures.
Ames, Nicoli M.; Lauffer, James P.; Jew, Michael D.; Segalman, Daniel Joseph; Gregory, Danny Lynn; Starr, Michael James; Resor, Brian Ray
2009-07-01
The problem of understanding and modeling the complicated physics underlying the action and response of the interfaces in typical structures under dynamic loading conditions has occupied researchers for many decades. This handbook presents an integrated approach to the goal of dynamic modeling of typical jointed structures, beginning with a mathematical assessment of experimental or simulation data, development of constitutive models to account for load histories to deformation, establishment of kinematic models coupling to the continuum models, and application of finite element analysis leading to dynamic structural simulation. In addition, formulations are discussed to mitigate the very short simulation time steps that appear to be required in numerical simulation for problems such as this. This handbook satisfies the commitment to DOE that Sandia will develop the technical content and write a Joints Handbook. The content will include: (1) Methods for characterizing the nonlinear stiffness and energy dissipation for typical joints used in mechanical systems and components. (2) The methodology will include practical guidance on experiments, and reduced order models that can be used to characterize joint behavior. (3) Examples for typical bolted and screw joints will be provided.
Feature extraction for structural dynamics model validation
Hemez, Francois; Farrar, Charles; Park, Gyuhae; Nishio, Mayuko; Worden, Keith; Takeda, Nobuo
2010-11-08
This study focuses on defining and comparing response features that can be used for structural dynamics model validation studies. Features extracted from dynamic responses obtained analytically or experimentally, such as basic signal statistics, frequency spectra, and estimated time-series models, can be used to compare characteristics of structural system dynamics. By comparing those response features extracted from experimental data and numerical outputs, validation and uncertainty quantification of numerical model containing uncertain parameters can be realized. In this study, the applicability of some response features to model validation is first discussed using measured data from a simple test-bed structure and the associated numerical simulations of these experiments. issues that must be considered were sensitivity, dimensionality, type of response, and presence or absence of measurement noise in the response. Furthermore, we illustrate a comparison method of multivariate feature vectors for statistical model validation. Results show that the outlier detection technique using the Mahalanobis distance metric can be used as an effective and quantifiable technique for selecting appropriate model parameters. However, in this process, one must not only consider the sensitivity of the features being used, but also correlation of the parameters being compared.
NASA Handbook for Spacecraft Structural Dynamics Testing
NASA Technical Reports Server (NTRS)
Kern, Dennis L.; Scharton, Terry D.
2004-01-01
Recent advances in the area of structural dynamics and vibrations, in both methodology and capability, have the potential to make spacecraft system testing more effective from technical, cost, schedule, and hardware safety points of view. However, application of these advanced test methods varies widely among the NASA Centers and their contractors. Identification and refinement of the best of these test methodologies and implementation approaches has been an objective of efforts by the Jet Propulsion Laboratory on behalf of the NASA Office of the Chief Engineer. But to develop the most appropriate overall test program for a flight project from the selection of advanced methodologies, as well as conventional test methods, spacecraft project managers and their technical staffs will need overall guidance and technical rationale. Thus, the Chief Engineer's Office has recently tasked JPL to prepare a NASA Handbook for Spacecraft Structural Dynamics Testing. An outline of the proposed handbook, with a synopsis of each section, has been developed and is presented herein. Comments on the proposed handbook is solicited from the spacecraft structural dynamics testing community.
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.
Aerodynamic applications of infrared thermography
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Alderfer, David W.
1989-01-01
A series of wind tunnel experiments were conducted as part of a systematic study for evaluation of infrared thermography as a viable non-intrusive thermal measurement technique for aerodynamic applications. The experiments consisted of obtaining steady-state surface temperature and convective heat transfer rates for a uniformly heated cylinder in transverse flow with a Reynolds number range of 46,000 to 250,000. The calculated convective heat transfer rates were in general agreement with classical data. Furthermore, IR thermography provided valuable real-time fluid dynamic information such as visualization of flow separation, transition and vortices.
Uncertain structural dynamics of aircraft panels and fuzzy structures analysis
NASA Astrophysics Data System (ADS)
Sparrow, Victor W.; Buehrle, Ralph D.
2002-11-01
Aircraft fuselage panels, seemingly simple structures, are actually complex because of the uncertainty of the attachments of the frame stiffeners and longitudinal stringers. It is clearly important to understand the dynamics of these panels because of the subsequent radiation into the passenger cabin, even when complete information is not available for all portions of the finite-element model. Over the last few years a fuzzy structures analysis (FSA) approach has been undertaken at Penn State and NASA Langley to quantify the uncertainty in modeling aircraft panels. A new MSC.Nastran [MSC.Software Corp. (Santa Ana, CA)] Direct Matrix Abstraction Program (DMAP) code was written and tested [AIAA paper 2001-1320, 42nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conf., Seattle, WA, 16 April 2001] and was applied to simple fuselage panel models [J. Acoust. Soc. Am. 109, 2410(A) (2001)]. Recently the work has focused on understanding the dynamics of a realistic aluminum fuselage panel, typical of today's aircraft construction. This presentation will provide an overview of the research and recent results will be given for the fuselage panel. Comparison between experiments and the FSA results will be shown for different fuzzy input parameters. [Work supported by NASA Research Cooperative Agreement NCC-1-382.
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)
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.
Sensitivity Analysis and Optimization of Aerodynamic Configurations with Blend Surfaces
NASA Technical Reports Server (NTRS)
Thomas, A. M.; Tiwari, S. N.
1997-01-01
A novel (geometrical) parametrization procedure using solutions to a suitably chosen fourth order partial differential equation is used to define a class of airplane configurations. Inclusive in this definition are surface grids, volume grids, and grid sensitivity. The general airplane configuration has wing, fuselage, vertical tail and horizontal tail. The design variables are incorporated into the boundary conditions, and the solution is expressed as a Fourier series. The fuselage has circular cross section, and the radius is an algebraic function of four design parameters and an independent computational variable. Volume grids are obtained through an application of the Control Point Form method. A graphic interface software is developed which dynamically changes the surface of the airplane configuration with the change in input design variable. The software is made user friendly and is targeted towards the initial conceptual development of any aerodynamic configurations. Grid sensitivity with respect to surface design parameters and aerodynamic sensitivity coefficients based on potential flow is obtained using an Automatic Differentiation precompiler software tool ADIFOR. Aerodynamic shape optimization of the complete aircraft with twenty four design variables is performed. Unstructured and structured volume grids and Euler solutions are obtained with standard software to demonstrate the feasibility of the new surface definition.
Aerodynamic Limitations of the UH-60A Rotor
NASA Technical Reports Server (NTRS)
Coleman, Colin P.; Bousman, William G.
1996-01-01
High quality airloads data have been obtained on an instrumented UH-60A in flight and these data provide insight into the aerodynamic limiting behavior of the rotor. At moderate weight coefficients and high advance ratio limiting performance is largely caused by high drag near the blade tip on the advancing side of the rotor as supercritical flow develops on the rotor with moderate to strong, shocks on both surfaces of the blade. Drag divergence data from two-dimensional airfoil tests show good agreement with the development of the supercritical flow regions. Large aerodynamic pitching moments are observed at high advance ratio, as well, and these pitching moments are the source of high torsional moments on the blade and control system loads. These loads occur on the advancing side of the disk and are not related to blade stall which does not occur for these weight coefficients. At high weight coefficients aerodynamic and structural limits are related to dynamic stall cycles that begin on the retreating side of the blade and, for the most severe conditions, carry around to the advancing side of the blade at the presumed first frequency of the blade/control system.
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.
Darrieus rotor aerodynamics in turbulent wind
Brahimi, M.T.; Paraschivoiu, I.
1995-05-01
The earlier aerodynamic models for studying vertical axis wind turbines (VAWT`s) are based on constant incident wind conditions and are thus capable of predicting only periodic variations in the loads. The purpose of the present study is to develop a model capable of predicting the aerodynamic loads on the Darrieus rotor in a turbulent wind. This model is based on the double-multiple streamtube method (DMS) and incorporates a stochastic wind model. The method used to simulate turbulent velocity fluctuations is based on the power spectral density. The problem consists in generating a region of turbulent flow with a relevant spectrum and spatial correlation. The first aerodynamic code developed is based on a one-dimensional turbulent wind model. However, since this model ignores the structure of the turbulence in the crossflow plane, an extension to three dimensions has been made. The computer code developed, CARDAAS, has been used to predict aerodynamic loads for the Sandia-17m rotor and compared to CARDAAV results and experimental data. Results have shown that the computed aerodynamic loads have been improved by including stochastic wind into the aerodynamic model.
Condensed Antenna Structural Models for Dynamics Analysis
NASA Technical Reports Server (NTRS)
Levy, R.
1985-01-01
Condensed degree-of-freedom models are compared with large degree-of-freedom finite-element models of a representative antenna-tipping and alidade structure, for both locked and free-rotor configurations. It is shown that: (1) the effective-mass models accurately reproduce the lower-mode natural frequencies of the finite element model; (2) frequency responses for the two types of models are in agreement up to at least 16 rad/s for specific points; and (3) transient responses computed for the same points are in good agreement. It is concluded that the effective-mass model, which best represents the five lower modes of the finite-element model, is a sufficient representation of the structure for future incorporation with a total servo control structure dynamic simulation.
Community structure and dynamics in social systems
NASA Astrophysics Data System (ADS)
Wilkinson, Dennis M.
This thesis presents applications of statistical physics to the study of the structure and dynamics of social systems, that is, systems whose interactions are based on information exchange. Social systems typically possess a community structure arising from the self organization of groups of interacting components into tightly-knit clusters. An automated method of identifying communities within a network of interactions is first presented. The method includes a statistical component crucial to obtaining accurate results in large, complex systems. It is applied to two real-world social networks, a network of email interactions and a network of related articles in the biomedical literature. The clusters it identifies within these networks are shown to correspond to communities of interrelated components. Next, the dynamics of cooperative problem solving processes on social systems are studied. A simple stochastic model is proposed which captures key aspects of the dynamics which have been empirically observed. Most important among these are the increase in average time to solution and in likelihood of long delays as the system size increases, as well as the log-normal distribution of times to solution. It is shown that a community structure both reduces the average time to solution and decreases the probability of delay. In cases where a system of cooperative efforts does not possess an inherent community structure, the effect of imposing communities is examined. The factor which most affects the dynamics when communities are imposed is shown to be the degree to which individuals neglect information from outside their own communities. The theory of stochastic vector processes is central to the dynamics of social systems and a mathematical study of this subject is presented. Expressions describing the evolution of the moments in the neighborhood of fixed points are obtained for arbitrary systems. Approximation techniques are applied in the small and large noise limits
Dynamic Probabilistic Instability of Composite Structures
NASA Technical Reports Server (NTRS)
Chamis, Christos C.
2009-01-01
A computationally effective method is described to evaluate the non-deterministic dynamic instability (probabilistic dynamic buckling) of thin composite shells. The method is a judicious combination of available computer codes for finite element, composite mechanics and probabilistic structural analysis. The solution method is incrementally updated Lagrangian. It is illustrated by applying it to thin composite cylindrical shell subjected to dynamic loads. Both deterministic and probabilistic buckling loads are evaluated to demonstrate the effectiveness of the method. A universal plot is obtained for the specific shell that can be used to approximate buckling loads for different load rates and different probability levels. Results from this plot show that the faster the rate, the higher the buckling load and the shorter the time. The lower the probability, the lower is the buckling load for a specific time. Probabilistic sensitivity results show that the ply thickness, the fiber volume ratio and the fiber longitudinal modulus, dynamic load and loading rate are the dominant uncertainties in that order.
Aerodynamic derivatives of a cone with a semi-apex angle 20° at supersonic velocities
NASA Astrophysics Data System (ADS)
Adamov, N. P.; Kharitonov, A. M.; Chasovnikov, E. A.
2014-12-01
The paper deals with an experimental study of stationary and nonstationary aerodynamic characteristics of a circular cone in the range of Mach numbers 1.75-7. The experimental equipment and the method of determining the aerodynamic characteristics are briefly described. The integral aerodynamic characteristics of the model in tests with force measurements and the aerodynamic derivatives of the pitching moment in dynamic tests on a setup with free oscillations are obtained. The experimental data are compared with numerical predictions.
Impact of Cross-Axis Structural Dynamics on Validation of Linear Models for Space Launch System
NASA Technical Reports Server (NTRS)
Pei, Jing; Derry, Stephen D.; Zhou Zhiqiang; Newsom, Jerry R.
2014-01-01
A feasibility study was performed to examine the advisability of incorporating a set of Programmed Test Inputs (PTIs) during the Space Launch System (SLS) vehicle flight. The intent of these inputs is to provide validation to the preflight models for control system stability margins, aerodynamics, and structural dynamics. During October 2009, Ares I-X program was successful in carrying out a series of PTI maneuvers which provided a significant amount of valuable data for post-flight analysis. The resulting data comparisons showed excellent agreement with the preflight linear models across the frequency spectrum of interest. However unlike Ares I-X, the structural dynamics associated with the SLS boost phase configuration are far more complex and highly coupled in all three axes. This presents a challenge when implementing this similar system identification technique to SLS. Preliminary simulation results show noticeable mismatches between PTI validation and analytical linear models in the frequency range of the structural dynamics. An alternate approach was examined which demonstrates the potential for better overall characterization of the system frequency response as well as robustness of the control design.
Structure and Dynamics with Ultrafast Electron Microscopes
NASA Astrophysics Data System (ADS)
Siwick, Bradley
In this talk I will describe how combining ultrafast lasers and electron microscopes in novel ways makes it possible to directly `watch' the time-evolving structure of condensed matter, both at the level of atomic-scale structural rearrangements in the unit cell and at the level of a material's nano- microstructure. First, I will briefly describe my group's efforts to develop ultrafast electron diffraction using radio- frequency compressed electron pulses in the 100keV range, a system that rivals the capabilities of xray free electron lasers for diffraction experiments. I will give several examples of the new kinds of information that can be gleaned from such experiments. In vanadium dioxide we have mapped the detailed reorganization of the unit cell during the much debated insulator-metal transition. In particular, we have been able to identify and separate lattice structural changes from valence charge density redistribution in the material on the ultrafast timescale. In doing so we uncovered a previously unreported optically accessible phase/state of vanadium dioxide that has monoclinic crystallography like the insulator, but electronic structure and properties that are more like the rutile metal. We have also combined these dynamic structural measurements with broadband ultrafast spectroscopy to make detailed connections between structure and properties for the photoinduced insulator to metal transition. Second, I will show how dynamic transmission electron microscopy (DTEM) can be used to make direct, real space images of nano-microstructural evolution during laser-induced crystallization of amorphous semiconductors at unprecedented spatio-temporal resolution. This is a remarkably complex process that involves several distinct modes of crystal growth and the development of intricate microstructural patterns on the nanosecond to ten microsecond timescales all of which can be imaged directly with DTEM.
Relevance of aerodynamic modelling for load reduction control strategies of two-bladed wind turbines
NASA Astrophysics Data System (ADS)
Luhmann, B.; Cheng, P. W.
2014-06-01
A new load reduction concept is being developed for the two-bladed prototype of the Skywind 3.5MW wind turbine. Due to transport and installation advantages both offshore and in complex terrain two-bladed turbine designs are potentially more cost-effective than comparable three-bladed configurations. A disadvantage of two-bladed wind turbines is the increased fatigue loading, which is a result of asymmetrically distributed rotor forces. The innovative load reduction concept of the Skywind prototype consists of a combination of cyclic pitch control and tumbling rotor kinematics to mitigate periodic structural loading. Aerodynamic design tools must be able to model correctly the advanced dynamics of the rotor. In this paper the impact of the aerodynamic modelling approach is investigated for critical operational modes of a two-bladed wind turbine. Using a lifting line free wake vortex code (FVM) the physical limitations of the classical blade element momentum theory (BEM) can be evaluated. During regular operation vertical shear and yawed inflow are the main contributors to periodic blade load asymmetry. It is shown that the near wake interaction of the blades under such conditions is not fully captured by the correction models of BEM approach. The differing prediction of local induction causes a high fatigue load uncertainty especially for two-bladed turbines. The implementation of both cyclic pitch control and a tumbling rotor can mitigate the fatigue loading by increasing the aerodynamic and structural damping. The influence of the time and space variant vorticity distribution in the near wake is evaluated in detail for different cyclic pitch control functions and tumble dynamics respectively. It is demonstrated that dynamic inflow as well as wake blade interaction have a significant impact on the calculated blade forces and need to be accounted for by the aerodynamic modelling approach. Aeroelastic simulations are carried out using the high fidelity multi body
Solar Prominence Fine Structure and Dynamics
NASA Astrophysics Data System (ADS)
Berger, Thomas
2014-01-01
We review recent observational and theoretical results on the fine structure and dynamics of solar prominences, beginning with an overview of prominence classifications, the proposal of possible new ``funnel prominence'' classification, and a discussion of the recent ``solar tornado'' findings. We then focus on quiescent prominences to review formation, down-flow dynamics, and the ``prominence bubble'' phenomena. We show new observations of the prominence bubble Rayleigh-Taylor instability triggered by a Kelvin-Helmholtz shear flow instability occurring along the bubble boundary. Finally we review recent studies on plasma composition of bubbles, emphasizing that differential emission measure (DEM) analysis offers a more quantitative analysis than photometric comparisons. In conclusion, we discuss the relation of prominences to coronal magnetic flux ropes, proposing that prominences can be understood as partially ionized condensations of plasma forming the return flow of a general magneto-thermal convection in the corona.
Aerodynamic Decelerators for Planetary Exploration: Past, Present, and Future
NASA Technical Reports Server (NTRS)
Cruz, Juna R.; Lingard, J. Stephen
2006-01-01
In this paper, aerodynamic decelerators are defined as textile devices intended to be deployed at Mach numbers below five. Such aerodynamic decelerators include parachutes and inflatable aerodynamic decelerators (often known as ballutes). Aerodynamic decelerators play a key role in the Entry, Descent, and Landing (EDL) of planetary exploration vehicles. Among the functions performed by aerodynamic decelerators for such vehicles are deceleration (often from supersonic to subsonic speeds), minimization of descent rate, providing specific descent rates (so that scientific measurements can be obtained), providing stability (drogue function - either to prevent aeroshell tumbling or to meet instrumentation requirements), effecting further aerodynamic decelerator system deployment (pilot function), providing differences in ballistic coefficients of components to enable separation events, and providing height and timeline to allow for completion of the EDL sequence. Challenging aspects in the development of aerodynamic decelerators for planetary exploration missions include: deployment in the unusual combination of high Mach numbers and low dynamic pressures, deployment in the wake behind a blunt-body entry vehicle, stringent mass and volume constraints, and the requirement for high drag and stability. Furthermore, these aerodynamic decelerators must be qualified for flight without access to the exotic operating environment where they are expected to operate. This paper is an introduction to the development and application of aerodynamic decelerators for robotic planetary exploration missions (including Earth sample return missions) from the earliest work in the 1960s to new ideas and technologies with possible application to future missions. An extensive list of references is provided for additional study.
Fundamental structures of dynamic social networks.
Sekara, Vedran; Stopczynski, Arkadiusz; Lehmann, Sune
2016-09-01
Social systems are in a constant state of flux, with dynamics spanning from minute-by-minute changes to patterns present on the timescale of years. Accurate models of social dynamics are important for understanding the spreading of influence or diseases, formation of friendships, and the productivity of teams. Although there has been much progress on understanding complex networks over the past decade, little is known about the regularities governing the microdynamics of social networks. Here, we explore the dynamic social network of a densely-connected population of ∼1,000 individuals and their interactions in the network of real-world person-to-person proximity measured via Bluetooth, as well as their telecommunication networks, online social media contacts, geolocation, and demographic data. These high-resolution data allow us to observe social groups directly, rendering community detection unnecessary. Starting from 5-min time slices, we uncover dynamic social structures expressed on multiple timescales. On the hourly timescale, we find that gatherings are fluid, with members coming and going, but organized via a stable core of individuals. Each core represents a social context. Cores exhibit a pattern of recurring meetings across weeks and months, each with varying degrees of regularity. Taken together, these findings provide a powerful simplification of the social network, where cores represent fundamental structures expressed with strong temporal and spatial regularity. Using this framework, we explore the complex interplay between social and geospatial behavior, documenting how the formation of cores is preceded by coordination behavior in the communication networks and demonstrating that social behavior can be predicted with high precision. PMID:27555584
Structure and Dynamics of Colliding Plasma Jets
Li, C.; Ryutov, D.; Hu, S.; Rosenberg, M.; Zylstra, A.; Seguin, F.; Frenje, J.; Casey, D.; Gatu Johnson, M.; Manuel, M.; et al
2013-12-01
Monoenergetic-proton radiographs of laser-generated, high-Mach-number plasma jets colliding at various angles shed light on the structures and dynamics of these collisions. The observations compare favorably with results from 2D hydrodynamic simulations of multistream plasma jets, and also with results from an analytic treatment of electron flow and magnetic field advection. In collisions of two noncollinear jets, the observed flow structure is similar to the analytic model’s prediction of a characteristic feature with a narrow structure pointing in one direction and a much thicker one pointing in the opposite direction. Spontaneous magnetic fields, largely azimuthal around the colliding jets and generatedmore » by the well-known ∇Te ×∇ne Biermann battery effect near the periphery of the laser spots, are demonstrated to be “frozen in” the plasma (due to high magnetic Reynolds number RM ~5×10⁴) and advected along the jet streamlines of the electron flow. These studies provide novel insight into the interactions and dynamics of colliding plasma jets.« less
Structure and Dynamics of Colliding Plasma Jets
Li, C.; Ryutov, D.; Hu, S.; Rosenberg, M.; Zylstra, A.; Seguin, F.; Frenje, J.; Casey, D.; Gatu Johnson, M.; Manuel, M.; Rinderknecht, H.; Petrasso, R.; Amendt, P.; Park, H.; Remington, B.; Wilks, S.; Betti, R.; Froula, D.; Knauer, J.; Meyerhofer, D.; Drake, R.; Kuranz, C.; Young, R.; Koenig, M.
2013-12-01
Monoenergetic-proton radiographs of laser-generated, high-Mach-number plasma jets colliding at various angles shed light on the structures and dynamics of these collisions. The observations compare favorably with results from 2D hydrodynamic simulations of multistream plasma jets, and also with results from an analytic treatment of electron flow and magnetic field advection. In collisions of two noncollinear jets, the observed flow structure is similar to the analytic model’s prediction of a characteristic feature with a narrow structure pointing in one direction and a much thicker one pointing in the opposite direction. Spontaneous magnetic fields, largely azimuthal around the colliding jets and generated by the well-known ∇T_{e} ×∇n_{e} Biermann battery effect near the periphery of the laser spots, are demonstrated to be “frozen in” the plasma (due to high magnetic Reynolds number R_{M} ~5×10⁴) and advected along the jet streamlines of the electron flow. These studies provide novel insight into the interactions and dynamics of colliding plasma jets.
Structural Dynamics of Tropical Moist Forest Gaps.
Hunter, Maria O; Keller, Michael; Morton, Douglas; Cook, Bruce; Lefsky, Michael; Ducey, Mark; Saleska, Scott; de Oliveira, Raimundo Cosme; Schietti, Juliana
2015-01-01
Gap phase dynamics are the dominant mode of forest turnover in tropical forests. However, gap processes are infrequently studied at the landscape scale. Airborne lidar data offer detailed information on three-dimensional forest structure, providing a means to characterize fine-scale (1 m) processes in tropical forests over large areas. Lidar-based estimates of forest structure (top down) differ from traditional field measurements (bottom up), and necessitate clear-cut definitions unencumbered by the wisdom of a field observer. We offer a new definition of a forest gap that is driven by forest dynamics and consistent with precise ranging measurements from airborne lidar data and tall, multi-layered tropical forest structure. We used 1000 ha of multi-temporal lidar data (2008, 2012) at two sites, the Tapajos National Forest and Ducke Reserve, to study gap dynamics in the Brazilian Amazon. Here, we identified dynamic gaps as contiguous areas of significant growth, that correspond to areas > 10 m2, with height <10 m. Applying the dynamic definition at both sites, we found over twice as much area in gap at Tapajos National Forest (4.8%) as compared to Ducke Reserve (2.0%). On average, gaps were smaller at Ducke Reserve and closed slightly more rapidly, with estimated height gains of 1.2 m y-1 versus 1.1 m y-1 at Tapajos. At the Tapajos site, height growth in gap centers was greater than the average height gain in gaps (1.3 m y-1 versus 1.1 m y-1). Rates of height growth between lidar acquisitions reflect the interplay between gap edge mortality, horizontal ingrowth and gap size at the two sites. We estimated that approximately 10% of gap area closed via horizontal ingrowth at Ducke Reserve as opposed to 6% at Tapajos National Forest. Height loss (interpreted as repeat damage and/or mortality) and horizontal ingrowth accounted for similar proportions of gap area at Ducke Reserve (13% and 10%, respectively). At Tapajos, height loss had a much stronger signal (23% versus 6
Structural Dynamics of Tropical Moist Forest Gaps
Hunter, Maria O.; Keller, Michael; Morton, Douglas; Cook, Bruce; Lefsky, Michael; Ducey, Mark; Saleska, Scott; de Oliveira, Raimundo Cosme; Schietti, Juliana
2015-01-01
Gap phase dynamics are the dominant mode of forest turnover in tropical forests. However, gap processes are infrequently studied at the landscape scale. Airborne lidar data offer detailed information on three-dimensional forest structure, providing a means to characterize fine-scale (1 m) processes in tropical forests over large areas. Lidar-based estimates of forest structure (top down) differ from traditional field measurements (bottom up), and necessitate clear-cut definitions unencumbered by the wisdom of a field observer. We offer a new definition of a forest gap that is driven by forest dynamics and consistent with precise ranging measurements from airborne lidar data and tall, multi-layered tropical forest structure. We used 1000 ha of multi-temporal lidar data (2008, 2012) at two sites, the Tapajos National Forest and Ducke Reserve, to study gap dynamics in the Brazilian Amazon. Here, we identified dynamic gaps as contiguous areas of significant growth, that correspond to areas > 10 m2, with height <10 m. Applying the dynamic definition at both sites, we found over twice as much area in gap at Tapajos National Forest (4.8 %) as compared to Ducke Reserve (2.0 %). On average, gaps were smaller at Ducke Reserve and closed slightly more rapidly, with estimated height gains of 1.2 m y-1 versus 1.1 m y-1 at Tapajos. At the Tapajos site, height growth in gap centers was greater than the average height gain in gaps (1.3 m y-1 versus 1.1 m y-1). Rates of height growth between lidar acquisitions reflect the interplay between gap edge mortality, horizontal ingrowth and gap size at the two sites. We estimated that approximately 10 % of gap area closed via horizontal ingrowth at Ducke Reserve as opposed to 6 % at Tapajos National Forest. Height loss (interpreted as repeat damage and/or mortality) and horizontal ingrowth accounted for similar proportions of gap area at Ducke Reserve (13 % and 10 %, respectively). At Tapajos, height loss had a much stronger signal (23
Adaptive dynamics for physiologically structured population models.
Durinx, Michel; Metz, J A J Hans; Meszéna, Géza
2008-05-01
We develop a systematic toolbox for analyzing the adaptive dynamics of multidimensional traits in physiologically structured population models with point equilibria (sensu Dieckmann et al. in Theor. Popul. Biol. 63:309-338, 2003). Firstly, we show how the canonical equation of adaptive dynamics (Dieckmann and Law in J. Math. Biol. 34:579-612, 1996), an approximation for the rate of evolutionary change in characters under directional selection, can be extended so as to apply to general physiologically structured population models with multiple birth states. Secondly, we show that the invasion fitness function (up to and including second order terms, in the distances of the trait vectors to the singularity) for a community of N coexisting types near an evolutionarily singular point has a rational form, which is model-independent in the following sense: the form depends on the strategies of the residents and the invader, and on the second order partial derivatives of the one-resident fitness function at the singular point. This normal form holds for Lotka-Volterra models as well as for physiologically structured population models with multiple birth states, in discrete as well as continuous time and can thus be considered universal for the evolutionary dynamics in the neighbourhood of singular points. Only in the case of one-dimensional trait spaces or when N = 1 can the normal form be reduced to a Taylor polynomial. Lastly we show, in the form of a stylized recipe, how these results can be combined into a systematic approach for the analysis of the (large) class of evolutionary models that satisfy the above restrictions. PMID:17943289
Algebraic Dynamic Programming over general data structures
2015-01-01
Background Dynamic programming algorithms provide exact solutions to many problems in computational biology, such as sequence alignment, RNA folding, hidden Markov models (HMMs), and scoring of phylogenetic trees. Structurally analogous algorithms compute optimal solutions, evaluate score distributions, and perform stochastic sampling. This is explained in the theory of Algebraic Dynamic Programming (ADP) by a strict separation of state space traversal (usually represented by a context free grammar), scoring (encoded as an algebra), and choice rule. A key ingredient in this theory is the use of yield parsers that operate on the ordered input data structure, usually strings or ordered trees. The computation of ensemble properties, such as a posteriori probabilities of HMMs or partition functions in RNA folding, requires the combination of two distinct, but intimately related algorithms, known as the inside and the outside recursion. Only the inside recursions are covered by the classical ADP theory. Results The ideas of ADP are generalized to a much wider scope of data structures by relaxing the concept of parsing. This allows us to formalize the conceptual complementarity of inside and outside variables in a natural way. We demonstrate that outside recursions are generically derivable from inside decomposition schemes. In addition to rephrasing the well-known algorithms for HMMs, pairwise sequence alignment, and RNA folding we show how the TSP and the shortest Hamiltonian path problem can be implemented efficiently in the extended ADP framework. As a showcase application we investigate the ancient evolution of HOX gene clusters in terms of shortest Hamiltonian paths. Conclusions The generalized ADP framework presented here greatly facilitates the development and implementation of dynamic programming algorithms for a wide spectrum of applications. PMID:26695390
Dynamic Structure in Artificial Protein Hydrogels
NASA Astrophysics Data System (ADS)
Kennedy, Scott B.; Hong, Mei; de Azevedo, Eduardo; Tirrell, David A.; Russell, Thomas P.
2000-03-01
Artificial proteins that form reversible hydrogels have been designed and synthesized using recombinant DNA methodologies. Proteins are designed such that two helical, leucine zipper domains flank a central, water soluble domain. Under proper conditions of concentration, pH, and temperature the helical domains aggregate as coiled coils and act as physical crosslinks. Small angle x-ray and neutron scattering have been used to elucidate the gel structure, and NMR and fluorescence exchange experiments have been used to probe the dynamics of the gel system.
Static and dynamic analyses of tensegrity structures
NASA Astrophysics Data System (ADS)
Nishimura, Yoshitaka
Tensegrity structures are a class of truss structures consisting of a continuous set of tension members (cables) and a discrete set of compression members (bars). Since tensegrity structures are light weight and can be compactly stowed and deployed, cylindrical tensegrity modules have been proposed for space structures. From a view point of structural dynamics, tensegrity structures pose a new set of problems, i.e., initial shape finding. Initial configurations of tensegrity structures must be computed by imposing a pre-stressability condition to initial equilibrium equations. There are ample qualitative statements regarding the initial geometry of cylindrical and spherical tensegrity modules. Quantitative initial shape anlyses have only been performed on one-stage and two-stage cylindrical modules. However, analytical expressions for important geometrical parameters such as twist angles and overlap ratios lack the definition of the initial shape of both cylindrical and spherical tensegrity modules. In response to the above needs, a set of static and dynamic characterization procedures for tensegrity modules was first developed. The procedures were subsequently applied to Buckminster Fuller's spherical tensegrity modules. Both the initial shape and the corresponding pre-stress mode were analytically obtained by using the graphs of the tetrahedral, octahedral (cubic), and icosahedral (dodecahedral) groups. For pre-stressed configurations, modal analyses were conducted to classify a large number of infinitesimal mechanism modes. The procedures also applied tocyclic cylindrical tensegrity modules with an arbitrary number of stages. It was found that both the Maxwell number and the number of infinitesimal mechanism modes are independent of the number of stages in the axial direction. A reduced set of equilibrium equations was derived by incorporating cyclic symmetry and the flip, or quasi-flip, symmetry of the cylindrical modules. For multi-stage modules with more than
Physics of badminton shuttlecocks. Part 1 : aerodynamics
NASA Astrophysics Data System (ADS)
Cohen, Caroline; Darbois Texier, Baptiste; Quéré, David; Clanet, Christophe
2011-11-01
We study experimentally shuttlecocks dynamics. In this part we show that shuttlecock trajectory is highly different from classical parabola. When one takes into account the aerodynamic drag, the flight of the shuttlecock quickly curves downwards and almost reaches a vertical asymptote. We solve the equation of motion with gravity and drag at high Reynolds number and find an analytical expression of the reach. At high velocity, this reach does not depend on velocity anymore. Even if you develop your muscles you will not manage to launch the shuttlecock very far because of the ``aerodynamic wall.'' As a consequence you can predict the length of the field. We then discuss the extend of the aerodynamic wall to other projectiles like sports balls and its importance.
Wind turbine aerodynamics research needs assessment
NASA Astrophysics Data System (ADS)
Stoddard, F. S.; Porter, B. K.
1986-01-01
A prioritized list is developed for wind turbine aerodynamic research needs and opportunities which could be used by the Department of Energy program management team in detailing the DOE Five-Year Wind Turbine Research Plan. The focus of the Assessment was the basic science of aerodynamics as applied to wind turbines, including all relevant phenomena, such as turbulence, dynamic stall, three-dimensional effects, viscosity, wake geometry, and others which influence aerodynamic understanding and design. The study was restricted to wind turbines that provide electrical energy compatible with the utility grid, and included both horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT). Also, no economic constraints were imposed on the design concepts or recommendations since the focus of the investigation was purely scientific.
Hypersonic Arbitrary-Body Aerodynamics (HABA) for conceptual design
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.
Numerical study on air-structure coupling dynamic characteristics of the axial fan blade
NASA Astrophysics Data System (ADS)
Chen, Q. G.; Xie, B.; Li, F.; Gu, W. G.
2013-12-01
In order to understand the dynamic characteristics of the axial-flow fan blade due to the effect of rotating stress and the action of unsteady aerodynamic forces caused by the airflow, a numerical simulation method for air-structure coupling in an axial-flow fan with fixed rear guide blades was performed. The dynamic characteristics of an axial-flow fan rotating blade were studied by using the two-way air-structure coupling method. Based on the standard k-ε turbulence model, and using weak coupling method, the preceding six orders modal parameters of the rotating blade were obtained, and the distributions of stress and strain on the rotating blade were presented. The results show that the modal frequency from the first to the sixth order is 3Hz higher than the modal frequency without considering air-structure coupling interaction; the maximum stress and the maximum strain are all occurred in the vicinity of root area of the blade no matter the air-structure coupling is considered or not, thus, the blade root is the dangerous location subjected to fatigue break; the position of maximum deformation is at the blade tip, so the vibration of the blade tip is significant. This study can provide theoretical references for the further study on the strength analysis and mechanical optimal design.
Molten uranium dioxide structure and dynamics
Skinner, L. B.; Parise, J. B.; Benmore, C. J.; Weber, J. K.R.; Williamson, M. A.; Tamalonis, A.; Hebden, A.; Wiencek, T.; Alderman, O. L.G.; Guthrie, M.; Leibowitz, L.
2014-11-21
Uranium dioxide (UO_{2}) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO_{2} as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO_{2} have prevented structural studies. In this work, we combine laser heating, sample levitation, and synchrotron x-rays to obtain pair distribution function measurements of hot solid and molten UO_{2}. The hot solid shows a substantial increase in oxygen disorder around the lambda transition (2670 K) but negligible U-O coordination change. On melting, the average U-O coordination drops from 8 to 6.7 ± 0.5. Molecular dynamics models refined to this structure predict higher U-U mobility than 8-coordinated melts.
Molten uranium dioxide structure and dynamics
Skinner, L. B.; Parise, J. B.; Benmore, C. J.; Weber, J. K.R.; Williamson, M. A.; Tamalonis, A.; Hebden, A.; Wiencek, T.; Alderman, O. L.G.; Guthrie, M.; et al
2014-11-21
Uranium dioxide (UO2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO2 have prevented structural studies. In this work, we combine laser heating, sample levitation, and synchrotron x-rays to obtain pair distribution function measurements of hot solid and molten UO2. The hot solid shows a substantial increase in oxygen disorder around the lambda transition (2670 K) but negligible U-O coordination change. Onmore » melting, the average U-O coordination drops from 8 to 6.7 ± 0.5. Molecular dynamics models refined to this structure predict higher U-U mobility than 8-coordinated melts.« less
Nucleon Structure from Dynamical Lattice QCD
Huey-Wen Lin
2007-06-01
We present lattice QCD numerical calculations of hadronic structure functions and form factors from full-QCD lattices, with a chirally symmetric fermion action, domain-wall fermions, for the sea and valence quarks. The lattice spacing is about 0.12 fm with physical volume approximately (2 fm)3 for RBC 2-flavor ensembles and (3 fm)3 for RBC/UKQCD 2+1-flavor dynamical ones. The lightest sea quark mass is about 1/2 the strange quark mass for the former ensembles and 1/4 for the latter ones. Our calculations include: isovector vector- and axial-charge form factors and the first few moments of the polarized and unpolarized structure functions of the nucleon. Nonperturbative renormalization in RI/MOM scheme is applied.
Nucleon Structure from Dynamical Lattice QCD
Lin, H.-W.
2007-06-13
We present lattice QCD numerical calculations of hadronic structure functions and form factors from full-QCD lattices, with a chirally symmetric fermion action, domain-wall fermions, for the sea and valence quarks. The lattice spacing is about 0.12 fm with physical volume approximately (2 fm)3 for RBC 2-flavor ensembles and (3 fm)3 for RBC/UKQCD 2+1-flavor dynamical ones. The lightest sea quark mass is about 1/2 the strange quark mass for the former ensembles and 1/4 for the latter ones. Our calculations include: isovector vector- and axial-charge form factors and the first few moments of the polarized and unpolarized structure functions of the nucleon. Nonperturbative renormalization in RI/MOM scheme is applied.
Molten uranium dioxide structure and dynamics.
Skinner, L B; Benmore, C J; Weber, J K R; Williamson, M A; Tamalonis, A; Hebden, A; Wiencek, T; Alderman, O L G; Guthrie, M; Leibowitz, L; Parise, J B
2014-11-21
Uranium dioxide (UO2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO2 have prevented structural studies. In this work, we combine laser heating, sample levitation, and synchrotron x-rays to obtain pair distribution function measurements of hot solid and molten UO2. The hot solid shows a substantial increase in oxygen disorder around the lambda transition (2670 K) but negligible U-O coordination change. On melting, the average U-O coordination drops from 8 to 6.7 ± 0.5. Molecular dynamics models refined to this structure predict higher U-U mobility than 8-coordinated melts. PMID:25414311
Structural Dynamics, Stability, and Control of Helicopters
NASA Technical Reports Server (NTRS)
Meirovitch, L.; Hale, A. L.
1978-01-01
The dynamic synthesis of gyroscopic structures consisting of point-connected substructures is investigated. The objective is to develop a mathematical model capable of an adequate simulation of the modal characteristics of a helicopter using a minimum number of degrees of freedom. The basic approach is to regard the helicopter structure as an assemblage of flexible substructures. The variational equations for the perturbed motion about certain equilibrium solutions are derived. The discretized variational equations can be conveniently exhibited in matrix form, and a great deal of information about the system modal characteristics can be extracted from the coefficient matrices. The derivation of the variational equations requires a monumental amount of algebraic operations. To automate this task a symbolic manipulation program on a digital computer is developed.
Dynamics and Emergent Structures in Active Fluids
NASA Astrophysics Data System (ADS)
Baskaran, Aparna
2014-03-01
In this talk, we consider an active fluid of colloidal sized particles, with the primary manifestation of activity being a self-replenishing velocity along one body axis of the particle. This is a minimal model for varied systems such as bacterial colonies, cytoskeletal filament motility assays vibrated granular particles and self propelled diffusophoretic colloids, depending on the nature of interaction among the particles. Using microscopic Brownian dynamics simulations, coarse-graining using the tools of non-equilibrium statistical mechanics and analysis of macroscopic hydrodynamic theories, we characterize emergent structures seen in these systems, which are determined by the symmetry of the interactions among the active units, such as propagating density waves, dense stationary bands, asters and phase separated isotropic clusters. We identify a universal mechanism, termed ``self-regulation,'' as the underlying physics that leads to these structures in diverse systems. Support from NSF through DMR-1149266 and DMR-0820492.
Structural dynamics and ecology of flatfish populations
NASA Astrophysics Data System (ADS)
Bailey, Kevin M.
1997-11-01
The concept of structure in populations of marine fishes is fundamental to how we manage and conduct research on these resources. The degree of population structure ranges widely among flatfishes. Although we know that large populations tend to be subdivided into local populations, based on morphological, meristic and reproductive characteristics, these data often conflict with evidence on genetic stock structure, due to the scale and organization of movement within the metapopulation. Movement of individuals between local subpopulations and colonization events on a macroecological scale are probably important to some flatfish populations. Dispersal of larvae is known to be a major factor affecting population mixing. Some flatfishes have planktonic stages of long duration and for these species there is often, but not always, little population structure; gene flow sometimes may be limited by oceanographic features, such as eddies and fronts. At the juvenile stage dispersal can result in colonization of under-utilized habitats; however, for flatfishes with strong habitat requirements, this type of event may be less likely when suitable habitats are fragmented. Complex population structure has major implications for management, e.g. lumping harvested populations with little gene flow can have detrimental local effects. Moreover, the issue of population structure and movement influences the interpretation of research data, where populations are generally treated as closed systems. There is currently a strong need for a multidisciplinary approach to study fish population dynamics and the structure of their populations. This research should involve molecular geneticists, population geneticists, animal behaviourists and ecologists. Migration mechanisms, colonization and extinction events, gene flow and density-dependent movements are subject areas of great importance to managing large harvested populations, but our understanding of them at ecological scales, at least for
NASA Technical Reports Server (NTRS)
Hemsch, Michael J. (Editor); Nielsen, Jack N. (Editor)
1986-01-01
The present conference on tactical missile aerodynamics discusses autopilot-related aerodynamic design considerations, flow visualization methods' role in the study of high angle-of-attack aerodynamics, low aspect ratio wing behavior at high angle-of-attack, supersonic airbreathing propulsion system inlet design, missile bodies with noncircular cross section and bank-to-turn maneuvering capabilities, 'waverider' supersonic cruise missile concepts and design methods, asymmetric vortex sheding phenomena from bodies-of-revolution, and swept shock wave/boundary layer interaction phenomena. Also discussed are the assessment of aerodynamic drag in tactical missiles, the analysis of supersonic missile aerodynamic heating, the 'equivalent angle-of-attack' concept for engineering analysis, the vortex cloud model for body vortex shedding and tracking, paneling methods with vorticity effects and corrections for nonlinear compressibility, the application of supersonic full potential method to missile bodies, Euler space marching methods for missiles, three-dimensional missile boundary layers, and an analysis of exhaust plumes and their interaction with missile airframes.
Solution Structure and Backbone Dynamics of Streptopain
Wang, Chih-Chieh; Houng, Hsiang-Chee; Chen, Chun-Liang; Wang, Pei-Ju; Kuo, Chih-Feng; Lin, Yee-Shin; Wu, Jiunn-Jong; Lin, Ming T.; Liu, Ching-Chuan; Huang, Wenya; Chuang, Woei-Jer
2009-01-01
Streptococcal pyrogenic exotoxin B (SPE B) is a cysteine protease expressed by Streptococcus pyogenes. The D9N, G163S, G163S/A172S, and G239D mutant proteins were expressed to study the effect of the allelic variants on their protease activity. In contrast to other mutants, the G239D mutant was ∼12-fold less active. The Gly-239 residue is located within the C-terminal S230-G239 region, which cannot be observed in the x-ray structure. The three-dimensional structure and backbone dynamics of the 28-kDa mature SPE B (mSPE B) were determined. Unlike the x-ray structure of the 40-kDa zymogen SPE B (proSPE B), we observed the interactions between the C-terminal loop and the active site residues in mSPE B. The structural differences between mSPE B and proSPE B were the conformation of the C-terminal loop and the orientation of the catalytic His-195 residue, suggesting that activation and inactivation of SPE B is involved in the His-195 side-chain rotation. Dynamics analysis of mSPE B and the mSPE B/inhibitor complexes showed that the catalytic and C-terminal loops were the most flexible regions with low order parameter values of 0.5 to 0.8 and exhibited the motion on the ps/ns timescale. These findings suggest that the flexible C-terminal loop of SPE B may play an important role in controlling the substrate binding, resulting in its broad substrate specificity. PMID:19237546
Aerodynamic properties of turbulent combustion fields
NASA Technical Reports Server (NTRS)
Hsiao, C. C.; Oppenheim, A. K.
1985-01-01
Flow fields involving turbulent flames in premixed gases under a variety of conditions are modeled by the use of a numerical technique based on the random vortex method to solve the Navier-Stokes equations and a flame propagation algorithm to trace the motion of the front and implement the Huygens principle, both due to Chorin. A successive over-relaxation hybrid method is applied to solve the Euler equation for flows in an arbitrarily shaped domain. The method of images, conformal transformation, and the integral-equation technique are also used to treat flows in special cases, according to their particular requirements. Salient features of turbulent flame propagation in premixed gases are interpreted by relating them to the aerodynamic properties of the flow field. Included among them is the well-known cellular structure of flames stabilized by bluff bodies, as well as the formation of the characteristic tulip shape of flames propagating in ducts. In its rudimentary form, the mechanism of propagation of a turbulent flame is shown to consist of: (1) rotary motion of eddies at the flame front, (2) self-advancement of the front at an appropriate normal burning speed, and (3) dynamic effects of expansion due to exothermicity of the combustion reaction. An idealized model is used to illustrate these fundamental mechanisms and to investigate basic aerodynamic features of flames in premixed gases. The case of a confined flame stabilized behind a rearward-facing step is given particular care and attention. Solutions are shown to be in satisfactory agreement with experimental results, especially with respect to global properties such as the average velocity profiles and reattachment length.
Fine Structure and Dynamics of Sunspot Penumbra
NASA Astrophysics Data System (ADS)
Ryutova, M.; Berger, T.; Title, A.
2007-08-01
A mature sunspot is usually surrounded by a penumbra: strong vertical magnetic field in the umbra, the dark central region of sunspot, becomes more and more horizontal toward the periphery forming an ensemble of a thin magnetic filaments of varying inclinations. Recent high resolution observations with the 1-meter Swedish Solar Telescope (SST) on La Palma revealed a fine substructure of penumbral filaments and new regularities in their dynamics.1 These findings provide both the basis and constraints for an adequate model of the penumbra whose origin still remains enigmatic. We present results of recent observations obtained with the SST. Our data, taken simultaneously in 4305 Å G-band and 4396 Å continuum bandpasses and compiled in high cadence movies, confirm previous results and reveal new features of the penumbra. We find e.g. that individual filaments are cylindrical helices with a pitch/radius ratio providing their dynamic stability. We propose a mechanism that may explain the fine structure of penumbral filaments, the observed regularities, and their togetherness with sunspot formation. The mechanism is based on the anatomy of sunspots in which not only penumbra has a filamentary structure but umbra itself is a dense conglomerate of twisted interlaced flux tubes.
Modeling Insurgent Network Structure and Dynamics
NASA Astrophysics Data System (ADS)
Gabbay, Michael; Thirkill-Mackelprang, Ashley
2010-03-01
We present a methodology for mapping insurgent network structure based on their public rhetoric. Indicators of cooperative links between insurgent groups at both the leadership and rank-and-file levels are used, such as joint policy statements or joint operations claims. In addition, a targeting policy measure is constructed on the basis of insurgent targeting claims. Network diagrams which integrate these measures of insurgent cooperation and ideology are generated for different periods of the Iraqi and Afghan insurgencies. The network diagrams exhibit meaningful changes which track the evolution of the strategic environment faced by insurgent groups. Correlations between targeting policy and network structure indicate that insurgent targeting claims are aimed at establishing a group identity among the spectrum of rank-and-file insurgency supporters. A dynamical systems model of insurgent alliance formation and factionalism is presented which evolves the relationship between insurgent group dyads as a function of their ideological differences and their current relationships. The ability of the model to qualitatively and quantitatively capture insurgent network dynamics observed in the data is discussed.
Chemical Structure and Dynamics annual report 1997
Colson, S.D.; McDowell, R.S.
1998-03-01
The Chemical Structure and Dynamics (CS and D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. The authors respond to the need for a fundamental, molecular level understanding of chemistry at a wide variety of environmentally important interfaces by: (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing complex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. The focus of the research is defined primarily by DOE`s environmental problems: fate and transport of contaminants in the subsurface environment, processing and storage of waste materials, cellular effects of chemical and radiological insult, and atmospheric chemistry as it relates to air quality and global change. Twenty-seven projects are described under the following topical sections: Reaction mechanisms at interfaces; High-energy processes at environmental interfaces; Cluster models of the condensed phase; and Miscellaneous.
Advanced aerodynamics and active controls. Selected NASA research
NASA Technical Reports Server (NTRS)
1981-01-01
Aerodynamic and active control concepts for application to commercial transport aircraft are discussed. Selected topics include in flight direct strike lightning research, triply redundant digital fly by wire control systems, tail configurations, winglets, and the drones for aerodynamic and structural testing (DAST) program.
Structure and Dynamics of the Solar Chromosphere
NASA Technical Reports Server (NTRS)
Kalkofen, Wolfgang
1998-01-01
The problem of chromospheric dynamics and heating consists of two problems: one, concerning the magnetic network on the boundary of supergranulation cells (CB), where the oscillation period is seven minutes, and the other, concerning the cell interior (CI), where the oscillation period is three minutes. The observational data on the oscillations and the emission of radiation can be used to determine the structure and dynamics of the atmosphere provided answers are known to three critical questions, concerning: the nature of the waves powering the bright points, the origin of the observed oscillation periods and the mechanism of chromospheric heating. The recent modeling of the dynamics of the CI, which combines a sophisticated treatment of gas dynamics and radiative transfer in a one-dimensional model with empirical velocity input from the observations, answered the first of these questions: the waves powering K(sub 2upsilon), bright points are propagating acoustic waves. This firm conclusion declares invalid the model of Leibacher & Stein, which explains the observed period with standing acoustic waves in a chromospheric cavity. On the third question, the heating of the chromosphere in the CI, their model predicts that the temperature in the chromosphere is declining in the outward direction up to a height of at least I Mm most of the time, so even the time-average temperature is dropping monotonically in the outward direction, implying that lines formed in the chromosphere up to a height of at least 1 Mm appear in absorption most of the time and everywhere in the CI. The problem of the CI can be resolved with a two-component model, which combines a model for K(sub 2upsilon), bright points with a model for the background. The bright point model has the same aims as the CS94 model, except that the empirical driving from the LRK93 observations is replaced by impulsive excitation, as suggested by the properties of the Klein-Gordon equation.
Structural Dynamics of the Vault Ribonucleoprotein Particle
NASA Astrophysics Data System (ADS)
Casañas, Arnau; Querol, Jordi; Fita, Ignasi; Verdaguer, Núria
Vaults are ubiquitous, highly conserved, 13 MDa ribonucleoprotein particles, involved in a diversity of cellular processes, including multidrug resistance, transport mechanisms and signal transmission. There are between 104 and 106 vault particles per mammalian cell and they do not trigger autoimmunity. The vault particle shows a hollow barrel-shaped structure organized in two identical moieties, each consisting of 39 copies of the major vault protein (MVP). Other data indicated that vault halves can dissociate at acidic pH. The high resolution, crystal structure of the of the seven N-terminal domains (R1-R7) of MVP, forming the central vault barrel, together with that of the native vault particle (solved at 8 Å resolution), revealed the interactions governing vault association and suggested a pH-dependent mechanism for a reversible dissociation induced by low pH. Vault particles posses many features making them very promising vehicles for the delivery of therapeutic agents including self-assembly, 100 nm size range, emerging atomic-level structural information, natural presence in humans ensuring biocompability, recombinant production system, existing features for targeting species to the large lumen and a dynamic structure that may be controlled for manipulation of drug release kinetics. All these attributes provide vaults with enormous potential as a drug/gene delivery platform.
Structural and dynamical properties of complex networks
NASA Astrophysics Data System (ADS)
Ghoshal, Gourab
Recent years have witnessed a substantial amount of interest within the physics community in the properties of networks. Techniques from statistical physics coupled with the widespread availability of computing resources have facilitated studies ranging from large scale empirical analysis of the worldwide web, social networks, biological systems, to the development of theoretical models and tools to explore the various properties of these systems. Following these developments, in this dissertation, we present and solve for a diverse set of new problems, investigating the structural and dynamical properties of both model and real world networks. We start by defining a new metric to measure the stability of network structure to disruptions, and then using a combination of theory and simulation study its properties in detail on artificially generated networks; we then compare our results to a selection of networks from the real world and find good agreement in most cases. In the following chapter, we propose a mathematical model that mimics the structure of popular file-sharing websites such as Flickr and CiteULike and demonstrate that many of its properties can solved exactly in the limit of large network size. The remaining part of the dissertation primarily focuses on the dynamical properties of networks. We first formulate a model of a network that evolves under the addition and deletion of vertices and edges, and solve for the equilibrium degree distribution for a variety of cases of interest. We then consider networks whose structure can be manipulated by adjusting the rules by which vertices enter and leave the network. We focus in particular on degree distributions and show that, with some mild constraints, it is possible by a suitable choice of rules to arrange for the network to have any degree distribution we desire. In addition we define a simple local algorithm by which appropriate rules can be implemented in practice. Finally, we conclude our
Structure and dynamics in Photosystem I
NASA Astrophysics Data System (ADS)
Jolley, Craig Charles
Photosystem I (PSI) is a transmembrane protein complex that uses incident light energy to drive an energetically unfavorable electron transfer reaction across a membrane in the early steps of oxygenic photosynthesis. This electron transfer reaction provides energy for the fixing of carbon dioxide and for the subsequent synthesis of nearly all biological material on Earth. Despite the morphological variety of oxygenic photosynthetic organisms---ranging from single-celled aquatic cyanobacteria to large, complex terrestrial plants---the structure and function of PSI are remarkably well-conserved across phyla. PSI has been the subject of extensive interdisciplinary research involving fields ranging from molecular genetics to condensed matter physics, and many aspects of its function still remain unclear. This study presents a variety of theoretical and experimental approaches to aspects of PSI structure and dynamics. An atomic-level structural model of higher plant PSI has been constructed based on recent protein crystal structures, and provides insight into the evolution of eukaryotic PSI. Time-resolved optical spectroscopic studies of PSI supercomplexes from the green freshwater alga Chlamydomonas reinhardtii illustrate how this organism adapts its photosynthetic apparatus to deal with changing environmental conditions and highlight the importance of structure-function relationships in light-harvesting systems. A novel computational approach using constrained geometric simulations has been used to model a portion of the PSI assembly process, shedding some light on how the heterodimeric PSI reaction center evolved from the more ancient homodimeric photosynthetic reaction centers found in green sulfur bacteria and heliobacteria. A new method is also demonstrated in which constrained geometric simulations are used to flexibly fit a high-resolution protein structure to a low-resolution density map obtained with cryo-electron microscopy (cryo-EM) or low-resolution x
Applied computational aerodynamics
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.
NASA Technical Reports Server (NTRS)
Tezduyar, Tayfun E.
1998-01-01
This is a final report as far as our work at University of Minnesota is concerned. The report describes our research progress and accomplishments in development of high performance computing methods and tools for 3D finite element computation of aerodynamic characteristics and fluid-structure interactions (FSI) arising in airdrop systems, namely ram-air parachutes and round parachutes. This class of simulations involves complex geometries, flexible structural components, deforming fluid domains, and unsteady flow patterns. The key components of our simulation toolkit are a stabilized finite element flow solver, a nonlinear structural dynamics solver, an automatic mesh moving scheme, and an interface between the fluid and structural solvers; all of these have been developed within a parallel message-passing paradigm.
Structural dynamic health monitoring of adaptive CFRP structures
NASA Astrophysics Data System (ADS)
Kaiser, Stephan; Melcher, Joerg; Breitbach, Elmar J.; Sachau, Delf
1999-07-01
The DLR Institute of Structural Mechanics is engaged in the construction and optimization of adaptive structures for aerospace and terrestrial applications. Due to the FFS- Project, one of the recent works of the Institute is the reduction of buffet induced vibration loads at a fin. The construction of modern aircrafts is influenced b the increasing use of fiber composites. They have more specific stiffness and strength properties than metals. On the other hand the layered structure leads to new kinds of damages like delaminations. In the fin interface there are actuators and sensors integrated. Therefore the fin is connected with a controller. For the extension of this adaptive system towards an on-line tool for health monitoring this controller can be used as an identifier of the structure's modal parameters. The most promising procedure is based on MX filters. These filters constitute the filter coefficients from which a fast transformation procedure extracts the modal parameters. The changes of these parameters are related to the location and extent of the damage. So when using the already integrate controller for system identification, one can have a low-cost on-line damage detection for dynamic adaptive structures. First off-line test at CFRP plates have shown the ability to detect delaminations.
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.
Chromospheric Structure and Dynamics--Observations
NASA Technical Reports Server (NTRS)
Ayres, Thomas R.
1997-01-01
The chromosphere is a highly structured dynamic 'layer' of the solar outer atmosphere. Here, not only are the effects of mechanical heating first evident (moving upward in altitude from the deep photosphere), but also the amount of nonradiative energy deposited is far greater than in the albeit much hotter overlying transition region and corona. Further, the chromosphere is by far the thickest zone of the solar atmosphere with respect to the pressure scale height. A major goal of stellar astrophysics is to understand how the chromosphere is heated and why it adopts its peculiar structure. A cursory examination of solar filtergrams and high-resolution movies demonstrates that much of the chromospheric "action" must be occurring on fine spatial scales and short times; particularly in the cell interior transient brightenings, but also in the longer-lived network fragments. That regime of investigation is far removed from what one usually associates with "synoptic" measurements. Nevertheless, synoptic observations of chromospheric indices, filtergrams, and globally-averaged profile parameters (e.g., for Ca II) not only can provide important insight concerning the crucial role of the cycle-variable part of the solar magnetic field; but they also can forge a key link with analogous measurements of the stars, where often the phenomena can be significantly exaggerated from the solar case, but high spatial resolution reconnaissance is not even a remote possibility. In addition to discussing the synoptic aspects of chromospheric structure and dynamics, I will summarize new insights into the general problem of the solar chromosphere that have been obtained recently with the SUMER far-ultraviolet spectrometer on SOHO.
NASA Technical Reports Server (NTRS)
Mankbadi, R.; Liu, J. T. C.
1984-01-01
The theoretical capability of identifying the source of turbulent jet noise is assessed in comparison with experimental data. Account is taken of axisymmetric and spiral turbulence modes in Lighthill's (1952) formulation of turbulent noise. Coherent structures interacting with the mean flow and the fine-grained turbulence are the primary noise sources, modeled as an oscillating streamwise distribution. Low-frequencies arise farther downstream while high-frequencies congregate close to the nozzle lip. Previous measurements at various exit velocities, angles with respect to the nozzle axis, the Strouhal number and downstream distance are discussed. The model successfully predicted the angular distribution of noise frequency due to coherent structures. Further work is indicated on compressibility effects.
Effects of kinematics on aerodynamic periodicity for a periodically plunging airfoil
NASA Astrophysics Data System (ADS)
Wu, Jianghao; Wang, Dou; Zhang, Yanlai
2015-12-01
In conventional Micro-Air-Vehicle design inspired by insects, the periodical motion of flapping airfoil usually leads to generation of a periodical aerodynamic force. However, recent studies indicate that time courses of aerodynamic force and flow structure of a flapping airfoil may be non-periodical even though the airfoil undergoes a periodical motion. In this paper, a computational fluid dynamics analysis is employed to investigate the effects of some dimensionless variables, such as Reynolds number, plunging amplitude, advance ratio, and angle of attack, on the periodicity of the flow around a flapping airfoil. The governing equations in an inertial frame of reference are solved to obtain unsteady flow structure and aerodynamic behaviors of the airfoil. It is found in the results that the periodicity of the flow and aerodynamics is greatly dependent on Reynolds number and plunging amplitude. Under given conditions, the product of these two variables may be utilized as a criterion parameter to judge whether the time course of the flow is periodical or not. In addition, a new mechanism that accounts for the non-periodical flow is revealed to explain the flow of airfoil with pre-stall angle of attack.
Aerodynamics of thrust vectoring
NASA Technical Reports Server (NTRS)
Tseng, J. B.; Lan, C. Edward
1989-01-01
Thrust vectoring as a means to enhance maneuverability and aerodynamic performane of a tactical aircraft is discussed. This concept usually involves the installation of a multifunction nozzle. With the nozzle, the engine thrust can be changed in direction without changing the attitude of the aircraft. Change in the direction of thrust induces a significant change in the aerodynamic forces on the aircraft. Therefore, this device can be used for lift-augmenting as well as stability and control purposes. When the thrust is deflected in the longitudinal direction, the lift force and the pitching stability can be manipulated, while the yawing stability can be controlled by directing the thrust in the lateral direction.
Unsteady Nonlinear Aerodynamic Response Modeling: A Data-Priven Perspective
NASA Astrophysics Data System (ADS)
Hemati, Maziar; Dawson, Scott; Rowley, Clarence
2014-11-01
Current real-time-capable aerodynamic modeling strategies are greatly challenged in the face of aggressive flight maneuvers, such as rapid pitching motions that lead to pronounced leading-edge vortex shedding and aerodynamic stall. The inability to accurately and robustly predict, in a low-dimensional manner, the nonlinear aerodynamic force/moment response of an aircraft to sharp maneuvers puts practical approaches for aerodynamic optimization and control out of reach. Here, we propose a parameter-varying model to approximate the response of an airfoil to arbitrarily prescribed rapid pitching kinematics. An output-minimization procedure is invoked to identify the nonlinear model from input-output data gathered from direct numerical fluid dynamics simulations. The resulting nonlinear models have noteworthy predictive capabilities for arbitrary pitching maneuvers that span a broad range of operating regimes, thus making the models especially useful for aerodynamic optimization and real-time control and simulation.
Evaluation of aerodynamic derivatives from a magnetic balance system
NASA Technical Reports Server (NTRS)
Raghunath, B. S.; Parker, H. M.
1972-01-01
The dynamic testing of a model in the University of Virginia cold magnetic balance wind-tunnel facility is expected to consist of measurements of the balance forces and moments, and the observation of the essentially six degree of freedom motion of the model. The aerodynamic derivatives of the model are to be evaluated from these observations. The basic feasibility of extracting aerodynamic information from the observation of a model which is executing transient, complex, multi-degree of freedom motion is demonstrated. It is considered significant that, though the problem treated here involves only linear aerodynamics, the methods used are capable of handling a very large class of aerodynamic nonlinearities. The basic considerations include the effect of noise in the data on the accuracy of the extracted information. Relationships between noise level and the accuracy of the evaluated aerodynamic derivatives are presented.
Nonparametric inference of network structure and dynamics
NASA Astrophysics Data System (ADS)
Peixoto, Tiago P.
The network structure of complex systems determine their function and serve as evidence for the evolutionary mechanisms that lie behind them. Despite considerable effort in recent years, it remains an open challenge to formulate general descriptions of the large-scale structure of network systems, and how to reliably extract such information from data. Although many approaches have been proposed, few methods attempt to gauge the statistical significance of the uncovered structures, and hence the majority cannot reliably separate actual structure from stochastic fluctuations. Due to the sheer size and high-dimensionality of many networks, this represents a major limitation that prevents meaningful interpretations of the results obtained with such nonstatistical methods. In this talk, I will show how these issues can be tackled in a principled and efficient fashion by formulating appropriate generative models of network structure that can have their parameters inferred from data. By employing a Bayesian description of such models, the inference can be performed in a nonparametric fashion, that does not require any a priori knowledge or ad hoc assumptions about the data. I will show how this approach can be used to perform model comparison, and how hierarchical models yield the most appropriate trade-off between model complexity and quality of fit based on the statistical evidence present in the data. I will also show how this general approach can be elegantly extended to networks with edge attributes, that are embedded in latent spaces, and that change in time. The latter is obtained via a fully dynamic generative network model, based on arbitrary-order Markov chains, that can also be inferred in a nonparametric fashion. Throughout the talk I will illustrate the application of the methods with many empirical networks such as the internet at the autonomous systems level, the global airport network, the network of actors and films, social networks, citations among
Structure, dynamics, and function of biomolecules
Frauenfelder, H.; Berendzen, J.R.; Garcia, A.; Gupta, G.; Olah, G.A.; Terwilliger, T.C.; Trewhella, J.; Wood, C.C.; Woodruff, W.H.
1998-11-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors enhanced Los Alamos' core competency in Bioscience and Biotechnology by building on present strengths in experimental techniques, theory, high-performance computing, modeling, and simulation applied to biomolecular structure, dynamics, and function. Specifically, the authors strengthened their capabilities in neutron/x-ray scattering, x-ray crystallography, NMR, laser, and optical spectroscopies. Initially they focused on supporting the Los alamos Neutron Science Center (LANSCE) in the design and implementation of new neutron scattering instrumentation, they developed new methods for analysis of scattering data, and they developed new projects to study the structures of biomolecular complexes. The authors have also worked to strengthen interactions between theory and experiment, and between the biological and physical sciences. They sponsored regular meetings of members from all interested LANL technical divisions, and supported two lecture series: ''Biology for Physicists'' and ''Issues in Modern Biology''. They also supported the formation of interdisciplinary/inter-divisional teams to develop projects in science-based bioremediation and an integrated structural biology resource. Finally, they successfully worked with a multidisciplinary team to put forward the Laboratory's Genome and Beyond tactical goal.
Structure and dynamics of glasses and glass formers
Angell, C.A.; Ngai, K.L.; Kieffer, J.; Egami, T.; Nienhaus, G.U.
1997-12-31
This book was divided into the following parts: (1) short-time dynamics; (2) relaxation dynamics of glasses and glass formers; (3) glasslike systems, simulations, and models; (4) contrasting metallic, ionic, bio, and polymer systems; (5) structure, energetics, and polyamorphism; and (6) structure and dynamics of glasses and glass formers. Separate abstracts were prepared for most papers in this volume.
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.
Structure and dynamics of amorphous water ice
NASA Technical Reports Server (NTRS)
Laufer, D.; Kochavi, E.; Bar-Nun, A.; Owen, T. (Principal Investigator)
1987-01-01
Further insight into the structure and dynamics of amorphous water ice, at low temperatures, was obtained by trapping in it Ar, Ne, H2, and D2. Ballistic water-vapor deposition results in the growth of smooth, approximately 1 x 0.2 micrometer2, ice needles. The amorphous ice seems to exist in at least two separate forms, at T < 85 K and at 85 < T < 136.8 K, and transform irreversibly from one form to the other through a series of temperature-dependent metastable states. The channels formed by the water hexagons in the ice are wide enough to allow the free penetration of H2 and D2 into the ice matrix even in the relatively compact cubic ice, resulting in H2-(D2-) to-ice ratios (by number) as high as 0.63. The larger Ar atoms can penetrate only into the wider channels of amorphous ice, and Ne is an intermediate case. Dynamic percolation behavior explains the emergence of Ar and Ne (but not H2 and D2) for the ice, upon warming, in small and big gas jets. The big jets, each containing approximately 5 x 10(10) atoms, break and propel the ice needles. Dynamic percolation also explains the collapse of the ice matrix under bombardment by Ar , at a pressure exceeding 2.6 dyn cm-2, and the burial of huge amounts of gas inside the collapsed matrix, up to an Ar-to-ice of 3.3 (by number). The experimental results could be relevant to comets, icy satellites, and icy grain mantles in dense interstellar clouds.
Computer graphics in aerodynamic analysis
NASA Technical Reports Server (NTRS)
Cozzolongo, J. V.
1984-01-01
The use of computer graphics and its application to aerodynamic analyses on a routine basis is outlined. The mathematical modelling of the aircraft geometries and the shading technique implemented are discussed. Examples of computer graphics used to display aerodynamic flow field data and aircraft geometries are shown. A future need in computer graphics for aerodynamic analyses is addressed.
Low Speed Aerodynamics of the X-38 CRV
NASA Technical Reports Server (NTRS)
Komerath, N. M.; Funk, R.; Ames, R. G.; Mahalingam, R.; Matos, C.
1998-01-01
This project was performed in support of the engineering development of the NASA X-38 Crew Return Vehicle (CRV)system. Wind tunnel experiments were used to visualize various aerodynamic phenomena encountered by the CRV during the final stages of descent and landing. Scale models of the CRV were used to visualize vortex structures above and below the vehicle, and in its wake, and to quantify their trajectories. The effect of flaperon deflection on these structures was studied. The structure and dynamics of the CRV's wake during the drag parachute deployment stage were measured. Regions of high vorticity were identified using surveys conducted in several planes using a vortex meter. Periodic shedding of the vortex sheets from the sides of the CRV was observed using laser sheet videography as the CRV reached high angles of attack during the quasi-steady pitch-up prior to parafoil deployment. Using spectral analysis of hot-film anemometer data, the Strouhal number of these wake fluctuations was found to be 0.14 based on the model span. Phenomena encountered in flight test during parafoil operation were captured in scale-model tests, and a video photogrammetry technique was implemented to obtain parafoil surface shapes during flight in the tunnel. Forces on the parafoil were resolved using tension gages on individual lines. The temporal evolution of the phenomenon of leading edge collapse was captured. Laser velocimetry was used to demonstrate measurement of the porosity of the parafoil surface. From these measurements, several physical explanations have been developed for phenomena observed at various stages of the X-38 development program. Quantitative measurement capabilities have also been demonstrated for continued refinement of the aerodynamic technologies employed in the X-38 project. Detailed results from these studies are given in an AIAA Paper, two slide presentations, and other material which are given on a Web-based archival resource. This is the Digital
Dynamics of influence on hierarchical structures
NASA Astrophysics Data System (ADS)
Fotouhi, Babak; Rabbat, Michael G.
2013-08-01
Dichotomous spin dynamics on a pyramidal hierarchical structure (the Bethe lattice) are studied. The system embodies a number of classes, where a class comprises nodes that are equidistant from the root (head node). Weighted links exist between nodes from the same and different classes. The spin (hereafter state) of the head node is fixed. We solve for the dynamics of the system for different boundary conditions. We find necessary conditions so that the classes eventually repudiate or acquiesce in the state imposed by the head node. The results indicate that to reach unanimity across the hierarchy, it suffices that the bottommost class adopts the same state as the head node. Then the rest of the hierarchy will inevitably comply. This also sheds light on the importance of mass media as a means of synchronization between the topmost and bottommost classes. Surprisingly, in the case of discord between the head node and the bottommost classes, the average state over all nodes inclines towards that of the bottommost class regardless of the link weights and intraclass configurations. Hence the role of the bottommost class is signified.
Structure and Dynamics of Cellulose Molecular Solutions
NASA Astrophysics Data System (ADS)
Wang, Howard; Zhang, Xin; Tyagi, Madhusudan; Mao, Yimin; Briber, Robert
Molecular dissolution of microcrystalline cellulose has been achieved through mixing with ionic liquid 1-Ethyl-3-methylimidazolium acetate (EMIMAc), and organic solvent dimethylformamide (DMF). The mechanism of cellulose dissolution in tertiary mixtures has been investigated by combining quasielastic and small angle neutron scattering (QENS and SANS). As SANS data show that cellulose chains take Gaussian-like conformations in homogenous solutions, which exhibit characteristics of having an upper critical solution temperature, the dynamic signals predominantly from EMIMAc molecules indicate strong association with cellulose in the dissolution state. The mean square displacement quantities support the observation of the stoichiometric 3:1 EMIMAc to cellulose unit molar ratio, which is a necessary criterion for the molecular dissolution of cellulose. Analyses of dynamics structure factors reveal the temperature dependence of a slow and a fast process for EMIMAc's bound to cellulose and in DMF, respectively, as well as a very fast process due possibly to the rotational motion of methyl groups, which persisted to near the absolute zero.
The dynamical structure of intense Mediterranean cyclones
NASA Astrophysics Data System (ADS)
Flaounas, Emmanouil; Raveh-Rubin, Shira; Wernli, Heini; Drobinski, Philippe; Bastin, Sophie
2015-05-01
This paper presents and analyzes the three-dimensional dynamical structure of intense Mediterranean cyclones. The analysis is based on a composite approach of the 200 most intense cyclones during the period 1989-2008 that have been identified and tracked using the output of a coupled ocean-atmosphere regional simulation with 20 km horizontal grid spacing and 3-hourly output. It is shown that the most intense Mediterranean cyclones have a common baroclinic life cycle with a potential vorticity (PV) streamer associated with an upper-level cyclonic Rossby wave breaking, which precedes cyclogenesis in the region and triggers baroclinic instability. It is argued that this common baroclinic life cycle is due to the strongly horizontally sheared environment in the Mediterranean basin, on the poleward flank of the quasi-persistent subtropical jet. The composite life cycle of the cyclones is further analyzed considering the evolution of key atmospheric elements as potential temperature and PV, as well as the cyclones' thermodynamic profiles and rainfall. It is shown that most intense Mediterranean cyclones are associated with warm conveyor belts and dry air intrusions, similar to those of other strong extratropical cyclones, but of rather small scale. Before cyclones reach their mature stage, the streamer's role is crucial to advect moist and warm air towards the cyclones center. These dynamical characteristics, typical for very intense extratropical cyclones in the main storm track regions, are also valid for these Mediterranean cases that have features that are visually similar to tropical cyclones.
The dynamical structure of intense Mediterranean cyclones
NASA Astrophysics Data System (ADS)
Flaounas, Emmanouil; Raveh-Rubin, Shira; Wernli, Heini; Drobinski, Philippe; Bastin, Sophie
2014-09-01
This paper presents and analyzes the three-dimensional dynamical structure of intense Mediterranean cyclones. The analysis is based on a composite approach of the 200 most intense cyclones during the period 1989-2008 that have been identified and tracked using the output of a coupled ocean-atmosphere regional simulation with 20 km horizontal grid spacing and 3-hourly output. It is shown that the most intense Mediterranean cyclones have a common baroclinic life cycle with a potential vorticity (PV) streamer associated with an upper-level cyclonic Rossby wave breaking, which precedes cyclogenesis in the region and triggers baroclinic instability. It is argued that this common baroclinic life cycle is due to the strongly horizontally sheared environment in the Mediterranean basin, on the poleward flank of the quasi-persistent subtropical jet. The composite life cycle of the cyclones is further analyzed considering the evolution of key atmospheric elements as potential temperature and PV, as well as the cyclones' thermodynamic profiles and rainfall. It is shown that most intense Mediterranean cyclones are associated with warm conveyor belts and dry air intrusions, similar to those of other strong extratropical cyclones, but of rather small scale. Before cyclones reach their mature stage, the streamer's role is crucial to advect moist and warm air towards the cyclones center. These dynamical characteristics, typical for very intense extratropical cyclones in the main storm track regions, are also valid for these Mediterranean cases that have features that are visually similar to tropical cyclones.
Dynamics and structure of planetary rings
NASA Technical Reports Server (NTRS)
French, R. G.
1991-01-01
Recent research efforts were directed towards sharpening the understanding of kinematical and dynamical properties of the Uranian rings, with the combination of Earth-based and Voyager observations, and in obtaining and interpreting new observations of the Saturn system from the remarkable stellar occultation of 3 Jul. 1989. Some of the highlights studied include: (1) a detailed comparison of structure and dynamics of the Uranus rings from joint analysis of high quality Earth-based data and the complete set of Voyager occultation measurements; (2) a comprehensive search for weak normal modes excited in the Uranian rings, analogous to the m = 2 and m = 0 normal modes previously identified for the delta and gamma rings; (3) an ongoing search for faint rings and ring arcs of Uranus, using both Voyager images of the rings and Earth-based and spacecraft stellar occultation data; (4) a comparison of upper stratospheric temperatures of Uranus inferred from Voyager ultraviolet occultations with results of ground-based occultation observations; and (5) observations of the 3 Jul. 1989 Saturn occultation of 28 Sgr.
Lagrangian coherent structures and inertial particle dynamics
NASA Astrophysics Data System (ADS)
Sudharsan, M.; Brunton, Steven L.; Riley, James J.
2016-03-01
In this work we investigate the dynamics of inertial particles using finite-time Lyapunov exponents (FTLE). In particular, we characterize the attractor and repeller structures underlying preferential concentration of inertial particles in terms of FTLE fields of the underlying carrier fluid. Inertial particles that are heavier than the ambient fluid (aerosols) attract onto ridges of the negative-time fluid FTLE. This negative-time FTLE ridge becomes a repeller for particles that are lighter than the carrier fluid (bubbles). We also examine the inertial FTLE (iFTLE) determined by the trajectories of inertial particles evolved using the Maxey-Riley equations with nonzero Stokes number and density ratio. Finally, we explore the low-pass filtering effect of Stokes number. These ideas are demonstrated on two-dimensional numerical simulations of the unsteady double-gyre flow.
Structure and Dynamic Regulation of Abl Kinases*
Panjarian, Shoghag; Iacob, Roxana E.; Chen, Shugui; Engen, John R.; Smithgall, Thomas E.
2013-01-01
The c-abl proto-oncogene encodes a unique protein-tyrosine kinase (Abl) distinct from c-Src, c-Fes, and other cytoplasmic tyrosine kinases. In normal cells, Abl plays prominent roles in cellular responses to genotoxic stress as well as in the regulation of the actin cytoskeleton. Abl is also well known in the context of Bcr-Abl, the oncogenic fusion protein characteristic of chronic myelogenous leukemia. Selective inhibitors of Bcr-Abl, of which imatinib is the prototype, have had a tremendous impact on clinical outcomes in chronic myelogenous leukemia and revolutionized the field of targeted cancer therapy. In this minireview, we focus on the structural organization and dynamics of Abl kinases and how these features influence inhibitor sensitivity. PMID:23316053
Segmenting dynamic human action via statistical structure.
Baldwin, Dare; Andersson, Annika; Saffran, Jenny; Meyer, Meredith
2008-03-01
Human social, cognitive, and linguistic functioning depends on skills for rapidly processing action. Identifying distinct acts within the dynamic motion flow is one basic component of action processing; for example, skill at segmenting action is foundational to action categorization, verb learning, and comprehension of novel action sequences. Yet little is currently known about mechanisms that may subserve action segmentation. The present research documents that adults can register statistical regularities providing clues to action segmentation. This finding provides new evidence that structural knowledge gained by mechanisms such as statistical learning can play a role in action segmentation, and highlights a striking parallel between processing of action and processing in other domains, such as language. PMID:18035346
Chromatin Higher-order Structure and Dynamics
Woodcock, Christopher L.; Ghosh, Rajarshi P.
2010-01-01
The primary role of the nucleus as an information storage, retrieval, and replication site requires the physical organization and compaction of meters of DNA. Although it has been clear for many years that nucleosomes constitute the first level of chromatin compaction, this contributes a relatively small fraction of the condensation needed to fit the typical genome into an interphase nucleus or set of metaphase chromosomes, indicating that there are additional “higher order” levels of chromatin condensation. Identifying these levels, their interrelationships, and the principles that govern their occurrence has been a challenging and much discussed problem. In this article, we focus on recent experimental advances and the emerging evidence indicating that structural plasticity and chromatin dynamics play dominant roles in genome organization. We also discuss novel approaches likely to yield important insights in the near future, and suggest research areas that merit further study. PMID:20452954
NASA Technical Reports Server (NTRS)
Massman, William
1987-01-01
A semianalytical method for describing the mean wind profile and shear stress within plant canopies and for estimating the roughness length and the displacement height is presented. This method incorporates density and vertical structure of the canopy and includes simple parameterizations of the roughness sublayer and shelter factor. Some of the wind profiles examined are consistent with first-order closure techniques while others are consistent with second-order closure techniques. Some profiles show a shearless region near the base of the canopy; however, none displays a secondary maximum there. Comparing several different analytical expressions for the canopy wind profile against observations suggests that one particular type of profile (an Airy function which is associated with the triangular foliage surface area density distribution) is superior to the others. Because of the numerical simplicity of the methods outlined, it is suggested that they may be profitably used in large-scale models of plant-atmosphere exchanges.
Multiscale Dynamics of Solar Magnetic Structures
NASA Technical Reports Server (NTRS)
Uritsky, Vadim M.; Davila, Joseph M.
2012-01-01
Multiscale topological complexity of the solar magnetic field is among the primary factors controlling energy release in the corona, including associated processes in the photospheric and chromospheric boundaries.We present a new approach for analyzing multiscale behavior of the photospheric magnetic flux underlying these dynamics as depicted by a sequence of high-resolution solar magnetograms. The approach involves two basic processing steps: (1) identification of timing and location of magnetic flux origin and demise events (as defined by DeForest et al.) by tracking spatiotemporal evolution of unipolar and bipolar photospheric regions, and (2) analysis of collective behavior of the detected magnetic events using a generalized version of the Grassberger-Procaccia correlation integral algorithm. The scale-free nature of the developed algorithms makes it possible to characterize the dynamics of the photospheric network across a wide range of distances and relaxation times. Three types of photospheric conditions are considered to test the method: a quiet photosphere, a solar active region (NOAA 10365) in a quiescent non-flaring state, and the same active region during a period of M-class flares. The results obtained show (1) the presence of a topologically complex asymmetrically fragmented magnetic network in the quiet photosphere driven by meso- and supergranulation, (2) the formation of non-potential magnetic structures with complex polarity separation lines inside the active region, and (3) statistical signatures of canceling bipolar magnetic structures coinciding with flaring activity in the active region. Each of these effects can represent an unstable magnetic configuration acting as an energy source for coronal dissipation and heating.
MULTISCALE DYNAMICS OF SOLAR MAGNETIC STRUCTURES
Uritsky, Vadim M.; Davila, Joseph M.
2012-03-20
Multiscale topological complexity of the solar magnetic field is among the primary factors controlling energy release in the corona, including associated processes in the photospheric and chromospheric boundaries. We present a new approach for analyzing multiscale behavior of the photospheric magnetic flux underlying these dynamics as depicted by a sequence of high-resolution solar magnetograms. The approach involves two basic processing steps: (1) identification of timing and location of magnetic flux origin and demise events (as defined by DeForest et al.) by tracking spatiotemporal evolution of unipolar and bipolar photospheric regions, and (2) analysis of collective behavior of the detected magnetic events using a generalized version of the Grassberger-Procaccia correlation integral algorithm. The scale-free nature of the developed algorithms makes it possible to characterize the dynamics of the photospheric network across a wide range of distances and relaxation times. Three types of photospheric conditions are considered to test the method: a quiet photosphere, a solar active region (NOAA 10365) in a quiescent non-flaring state, and the same active region during a period of M-class flares. The results obtained show (1) the presence of a topologically complex asymmetrically fragmented magnetic network in the quiet photosphere driven by meso- and supergranulation, (2) the formation of non-potential magnetic structures with complex polarity separation lines inside the active region, and (3) statistical signatures of canceling bipolar magnetic structures coinciding with flaring activity in the active region. Each of these effects can represent an unstable magnetic configuration acting as an energy source for coronal dissipation and heating.
Chemical structure and dynamics. Annual report 1994
Colson, S.D.
1995-07-01
The Chemical Structure and Dynamics program was organized as a major component of Pacific Northwest Laboratory`s Environmental and Molecular Sciences Laboratory (EMSL), a state-of-the-art collaborative facility for studies of chemical structure and dynamics. Our program responds to the need for a fundamental, molecular-level understanding of chemistry at the wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces, and (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage. This research effort was initiated in 1989 and will continue to evolve over the next few years into a program of rigorous studies of fundamental molecular processes in model systems, such as well-characterized surfaces, single-component solutions, clusters, and biological molecules; and studies of complex systems found in the environment (multispecies, multiphase solutions; solid/liquid, liquid/liquid, and gas/surface interfaces; colloidal dispersions; ultrafine aerosols; and functioning biological systems). The success of this program will result in the achievement of a quantitative understanding of chemical reactions at interfaces, and more generally in condensed media, that is comparable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for predictions of macroscopic chemical behavior in condensed and heterogeneous media, adding significantly to the value of field-scale environmental models, the prediction of short- and long-term nuclear waste storage stabilities, and other problems related to the primary missions of the DOE.
Annual Report 1998: Chemical Structure and Dynamics
RS McDowell.
1999-05-10
The Chemical Structure and Dynamics (CS D) program is a major component of the William R. Wiley Environmental Molecular Sciences Labo- ratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of- the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interracial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in envi- ronmental chemistry and in nuclear waste proc- essing and storage; and (3) developing state-of- the-art analytical methods for characterizing com- plex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. Our program aims at achieving a quantitative understanding of chemical reactions at interfaces and, more generally, in condensed media, compa- rable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for pre- dicting macroscopic chemical behavior in con- densed and heterogeneous media, which will add significantly to the value of field-scale envi- ronmental models, predictions of short- and long- term nuclear waste storage stabilities, and other areas related to the primary missions of the U.S. Department of Energy (DOE).
Annual Report 1998: Chemical Structure and Dynamics
SD Colson; RS McDowell
1999-05-10
The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Labo- ratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of- the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interracial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in envi- ronmental chemistry and in nuclear waste proc- essing and storage; and (3) developing state-of- the-art analytical methods for characterizing com- plex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. Our program aims at achieving a quantitative understanding of chemical reactions at interfaces and, more generally, in condensed media, compa- rable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for pre- dicting macroscopic chemical behavior in con- densed and heterogeneous media, which will add significantly to the value of field-scale envi- ronmental models, predictions of short- and long- term nuclear waste storage stabilities, and other areas related to the primary missions of the U.S. Department of Energy (DOE).
Aerodynamics Improve Wind Wheel
NASA Technical Reports Server (NTRS)
Ramsey, V. W.
1982-01-01
Modifications based on aerodynamic concepts would raise efficiency of wind-wheel electric-power generator. Changes smooth airflow, to increase power output, without increasing size of wheel. Significant improvements in efficiency anticipated without any increase in size or number of moving parts and without departing from simplicity of original design.
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.
Photogrammetry of a Hypersonic Inflatable Aerodynamic Decelerator
NASA Technical Reports Server (NTRS)
Kushner, Laura Kathryn; Littell, Justin D.; Cassell, Alan M.
2013-01-01
In 2012, two large-scale models of a Hypersonic Inflatable Aerodynamic decelerator were tested in the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. One of the objectives of this test was to measure model deflections under aerodynamic loading that approximated expected flight conditions. The measurements were acquired using stereo photogrammetry. Four pairs of stereo cameras were mounted inside the NFAC test section, each imaging a particular section of the HIAD. The views were then stitched together post-test to create a surface deformation profile. The data from the photogram- metry system will largely be used for comparisons to and refinement of Fluid Structure Interaction models. This paper describes how a commercial photogrammetry system was adapted to make the measurements and presents some preliminary results.
DISCOS- DYNAMIC INTERACTION SIMULATION OF CONTROLS AND STRUCTURES (IBM VERSION)
NASA Technical Reports Server (NTRS)
Frisch, H. P.
1994-01-01
deployment, analysis of multispin satellites, and analysis of large, highly flexible satellites, including the design of attitude-control systems. The overall approach of DISCOS is unique in that any member body of the system may be flexible, and the system is not restricted to a topological tree configuration. The equations of motion are developed using the most general form of Lagrange's equations, including auxiliary nonholonomic rehenomic conditions of constraint. Lagrange multipliers are used as interaction forces/ torques to maintain prescribed constraints. Nonlinear flexible/rigid dynamic coupling effects are accounted for in unabridged fashion for individual bodies and for the total system. Elastic deformation can be represented by normal vibration modes or by any adequate series of Rayleigh functions, including 'quasi-static' displacement functions. To 'solve' Lagrange's equations of motion, the explicit form of the kinetic and potential energy functions, the dissipation function, and the form of the transformation relating ordinary Cartesian position coordinates to the generalized coordinates must be defined. The potential energy and dissipation functions for a structure are determined with standard finite-element techniques by the NASTRAN program. In order to use the computed functions, the Lagrange's equations and the system kinematic constraint equations are expressed in matrix format. These differential matrix equations are solved numerically by the DISCOS program. Provisions are included for environmental loading of the structure (spacecraft), including solar pressure, gravity gradient, and aerodynamic drag. Input to DISCOS includes topological and geometrical descriptions of the structure under analysis, initial conditions, control system descriptions, and NASTRAN-derived structural matrices. Specialized routines are supplied that read the input data and redimension the DISCOS programs to minimize core requirements. Output includes an extensive list of
An aerodynamic load criterion for airships
NASA Technical Reports Server (NTRS)
Woodward, D. E.
1975-01-01
A simple aerodynamic bending moment envelope is derived for conventionally shaped airships. This criterion is intended to be used, much like the Naval Architect's standard wave, for preliminary estimates of longitudinal strength requirements. It should be useful in tradeoff studies between speed, fineness ratio, block coefficient, structure weight, and other such general parameters of airship design.
Space Station Freedom solar dynamic modules structural modelling and analysis
Lawrence, C.; Morris, R.
1991-12-01
In support of the Space Station Freedom (SSF) Solar Dynamic Power Module effort, structural design studies were performed to investigate issues related to the design of the power module, its pointing capabilities, and the integration of the module into the SSF infrastructure. Of particular concern from a structural viewpoint are the dynamics of the power module, the impact of the power module on the Space Station dynamics and controls, and the required control effort for obtaining the specified Solar Dynamic Power Module pointing accuracy. Structural analyses were performed to determine the structural dynamics attributes of both the existing and the proposed structural dynamics module designs. The objectives of these analyses were to generate validated Solar Dynamic Power Module NASTRAN finite element models, combine Space Station and power module models into integrated system models, perform finite element modal analyses to assess the effect of the relocations of the power module center of mass, and provide modal data to controls designers for control systems design.
Dynamics of wake structure in clapping propulsion
NASA Astrophysics Data System (ADS)
Kim, Daegyoum; Gharib, Morteza
2009-11-01
Some animals such as insects and frogs use a pair of symmetric flaps for locomotion. In some cases, these flappers operate in close proximity or even touch each other. In order to understand the underlying physics of these kinds of motion, we have studied the wake structures induced by clapping and their associated thrust performance. A simple mechanical model with two acrylic plates was used to simulate the power stroke of the clapping motion and three-dimensional flow fields were obtained using defocusing digital particle image velocimetry. Our studies show that the process of vortex connection plays a critical role in forming a downstream closed vortex loop. Under some kinematic conditions, this vortex loop changes its shape dynamically, which is analogous to the process of an elliptical vortex ring switching its minor and major axis. As the length of the plate along the rotating shaft decreases to change an aspect ratio, the downstream motion of the vortex is retarded due to the outward motion of side edge vortices and less propulsive force is generated per the surface area of the plate. The impact of compliance and stroke angle of the plate on wake structures and thrust magnitudes are also presented.
Dynamics of Subauroral Polarization Stream (SAPS) Structures
NASA Astrophysics Data System (ADS)
Sazykin, S. Y.; Coster, A. J.; Huba, J.; Ridley, A. J.; Erickson, P. J.; Foster, J. C.; Baker, J. B. H.; Wolf, R.
2015-12-01
The Subauroral Polarization Stream (SAPS) flow structures are narrow ionospheric channels of fast (in excess of 100 m/s) westward drift just outside the equatorward edge of the diffuse aurora in the dusk-to-midnight local time sector. Other terms for this phenomenon include subauroral Ion Drift (SAID) events and Polarization Jets. SAPS structures represent a striking departure from the commonly-used two-cell convection pattern. They are thought to arise from the displacement of the downward region-2 Birkeland currents on the dusk side equatorward of the low-latitude boundary of the auroral oval during times of changing high-latitude convection. In this paper, we will use several event simulations with the SAMI3-RCM numerical model (a self-consistent ionosphere-inner magnetosphere model) and RCM-GITM (a self-consistent model of the ionosphere-thermosphere-inner magnetosphere) to analyze the relative roles of changes in the IMF Bz component, ionospheric electron density depletions, and thermospheric modifications in controlling the dynamics of SAPS. Simulation results will be compared to multi-instrument ionospheric observations.
Digital system for structural dynamics simulation
NASA Technical Reports Server (NTRS)
Krauter, A. I.; Lagace, L. J.; Wojnar, M. K.; Glor, C.
1982-01-01
State-of-the-art digital hardware and software for the simulation of complex structural dynamic interactions, such as those which occur in rotating structures (engine systems). System were incorporated in a designed to use an array of processors in which the computation for each physical subelement or functional subsystem would be assigned to a single specific processor in the simulator. These node processors are microprogrammed bit-slice microcomputers which function autonomously and can communicate with each other and a central control minicomputer over parallel digital lines. Inter-processor nearest neighbor communications busses pass the constants which represent physical constraints and boundary conditions. The node processors are connected to the six nearest neighbor node processors to simulate the actual physical interface of real substructures. Computer generated finite element mesh and force models can be developed with the aid of the central control minicomputer. The control computer also oversees the animation of a graphics display system, disk-based mass storage along with the individual processing elements.
Aerodynamic heated steam generating apparatus
Kim, K.
1986-08-12
An aerodynamic heated steam generating apparatus is described which consists of: an aerodynamic heat immersion coil steam generator adapted to be located on the leading edge of an airframe of a hypersonic aircraft and being responsive to aerodynamic heating of water by a compression shock airstream to produce steam pressure; an expansion shock air-cooled condensor adapted to be located in the airframe rearward of and operatively coupled to the aerodynamic heat immersion coil steam generator to receive and condense the steam pressure; and an aerodynamic heated steam injector manifold adapted to distribute heated steam into the airstream flowing through an exterior generating channel of an air-breathing, ducted power plant.
Sea anemones possess dynamic mitogenome structures.
Emblem, Åse; Okkenhaug, Siri; Weiss, Emily S; Denver, Dee R; Karlsen, Bård Ove; Moum, Truls; Johansen, Steinar D
2014-06-01
A notable feature of hexacoral mitogenomes is the presence of complex self-catalytic group I introns. We investigated mitogenome structural variations and evolutionary mechanisms in actiniarian sea anemones based on the complete mitogenome sequence of the cold-water sea anemone species Urticina eques, Bolocera tuediae, Hormathia digitata and Metridium senile, and two isolates of the sub-tropical Aiptasia pulchella. Whole genome sequencing at 50 times coverage of B. tuediae and H. digitata indicated low mtDNA copy number of per haploid nuclear genome and presence of rare haplotypes. A group I intron inserted in ND5 was found to host essential mitochondrial protein genes in all species, and an additional truncated copy of ND5 in B. tuediae. A second group I intron (inserted in COI) that contained a homing endonuclease gene (HEG) was present in all mtDNA examined. Different variants of HEGs were observed, and included expressed elements fused in-frame with upstream exons and free-standing HEGs embedded within the intron. A notable hallmark of HEGs was a high extent of overlap with ribozyme structural elements; the U. eques HEG overlapped with the entire intron. We reconstructed the evolutionary history of the COI intron from insertion at unoccupied cognate sites, through HEG degradation, to intron loss. We also identified a novel insertion element in U. eques that contained two expressed protein-coding genes. An evolutionary analysis of the sea anemone mtDNA genes revealed higher substitution rates in the HEG and the insertion sequence as compared to the other loci, indicating relaxed selective pressures in these elements. We conclude that sea anemone mitogenomes are surprisingly dynamic in structure despite the economical organization and low sequence mutation rate. PMID:24613805
Dynamic Wind Loads and Vortex Structures in the Wake of a Wind Turbine
NASA Astrophysics Data System (ADS)
Hu, Hui; Yang, Zifeng; Sarkar, Partha
2010-11-01
We report an experimental study to characterize the dynamic wind loads and evolution of wake vortex flow structures downstream of a horizontal axis wind turbine (HAWT). The experiments were conducted in a wind tunnel with a wind turbine model placed in a boundary layer flow developed over rough and smooth surfaces in order to study the effects of roughness and the resulting velocity and turbulence fields on the wake characteristics and fatigue loads acting on the wind turbine. In addition to measuring dynamic wind loads (both aerodynamic forces and moments) acting on the wind turbine model using a six-component load cell, a high-resolution Particle Image Velocimetry (PIV) system was used to make phase-locked flow field measurements to quantify the time-evolution of the wake vortex and turbulence flow structures shedding from wind turbine blades. The detailed flow field measurements were correlated with the wind load measurements to elucidate the underlying physics associated with turbine power generation and fatigue loads acting on wind turbines.
Simultaneous Aerodynamic Analysis and Design Optimization (SAADO) for a 3-D Flexible Wing
NASA Technical Reports Server (NTRS)
Gumbert, Clyde R.; Hou, Gene J.-W.
2001-01-01
The formulation and implementation of an optimization method called Simultaneous Aerodynamic Analysis and Design Optimization (SAADO) are extended from single discipline analysis (aerodynamics only) to multidisciplinary analysis - in this case, static aero-structural analysis - and applied to a simple 3-D wing problem. The method aims to reduce the computational expense incurred in performing shape optimization using state-of-the-art Computational Fluid Dynamics (CFD) flow analysis, Finite Element Method (FEM) structural analysis and sensitivity analysis tools. Results for this small problem show that the method reaches the same local optimum as conventional optimization. However, unlike its application to the win,, (single discipline analysis), the method. as I implemented here, may not show significant reduction in the computational cost. Similar reductions were seen in the two-design-variable (DV) problem results but not in the 8-DV results given here.
Prediction of Hyper-X Stage Separation Aerodynamics Using CFD
NASA Technical Reports Server (NTRS)
Buning, Pieter G.; Wong, Tin-Chee; Dilley, Arthur D.; Pao, Jenn L.
2000-01-01
The NASA X-43 "Hyper-X" hypersonic research vehicle will be boosted to a Mach 7 flight test condition mounted on the nose of an Orbital Sciences Pegasus launch vehicle. The separation of the research vehicle from the Pegasus presents some unique aerodynamic problems, for which computational fluid dynamics has played a role in the analysis. This paper describes the use of several CFD methods for investigating the aerodynamics of the research and launch vehicles in close proximity. Specifically addressed are unsteady effects, aerodynamic database extrapolation, and differences between wind tunnel and flight environments.
Bioinspired, dynamic, structured surfaces for biofilm prevention
NASA Astrophysics Data System (ADS)
Epstein, Alexander K.
Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of biocidal treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters, frequently impossible. Adding to the challenge, we have discovered that biofilm can be both impenetrable to vapors and extremely nonwetting, repelling even low surface tension commercial antimicrobials. Our study shows multiple contributing factors, including biochemical components and multiscale reentrant topography. Reliant on surface chemistry, conventional strategies for preventing biofilm only transiently affect attachment and/or are environmentally toxic. In this work, we look to Nature's antifouling solutions, such as the dynamic spiny skin of the echinoderm, and we develop a versatile surface nanofabrication platform. Our benchtop approach unites soft lithography, electrodeposition, mold deformation, and material selection to enable many degrees of freedom—material, geometric, mechanical, dynamic—that can be programmed starting from a single master structure. The mechanical properties of the bio-inspired nanostructures, verified by AFM, are precisely and rationally tunable. We examine how synthetic dynamic nanostructured surfaces control the attachment of pathogenic biofilms. The parameters governing long-range patterning of bacteria on high-aspect-ratio (HAR) nanoarrays are combinatorially elucidated, and we discover that sufficiently low effective stiffness of these HAR arrays mechanoselectively inhibits ˜40% of Pseudomonas aeruginosa biofilm attachment. Inspired by the active echinoderm skin, we design and fabricate externally actuated dynamic elastomer surfaces with active surface microtopography. We extract from a large parameter space the critical topographic length scales and actuation time scales for achieving
Structural dynamics technology research in NASA: Perspective on future needs
NASA Technical Reports Server (NTRS)
1979-01-01
The perspective of a NASA ad hoc study group on future research needs in structural dynamics within the aerospace industry is presented. The common aspects of the design process across the industry are identified and the role of structural dynamics is established through a discussion of various design considerations having their basis in structural dynamics. The specific structural dynamics issues involved are identified and assessed as to their current technological status and trends. Projections of future requirements based on this assessment are made and areas of research to meet them are identified.
Launch vehicle aerodynamic data base development comparison with flight data
NASA Technical Reports Server (NTRS)
Hamilton, J. T.; Wallace, R. O.; Dill, C. C.
1983-01-01
The aerodynamic development plan for the Space Shuttle integrated vehicle had three major objectives. The first objective was to support the evolution of the basic configuration by establishing aerodynamic impacts to various candidate configurations. The second objective was to provide continuing evaluation of the basic aerodynamic characteristics in order to bring about a mature data base. The third task was development of the element and component aerodynamic characteristics and distributed air loads data to support structural loads analyses. The complexity of the configurations rendered conventional analytic methods of little use and therefore required extensive wind tunnel testing of detailed complex models. However, the ground testing and analyses did not predict the aerodynamic characteristics that were extracted from the Space Shuttle flight test program. Future programs that involve the use of vehicles similar to the Space Shuttle should be concerned with the complex flow fields characteristics of these types of complex configurations.
Structural dynamics and vibrations of damped, aircraft-type structures
NASA Technical Reports Server (NTRS)
Young, Maurice I.
1992-01-01
Engineering preliminary design methods for approximating and predicting the effects of viscous or equivalent viscous-type damping treatments on the free and forced vibration of lightly damped aircraft-type structures are developed. Similar developments are presented for dynamic hysteresis viscoelastic-type damping treatments. It is shown by both engineering analysis and numerical illustrations that the intermodal coupling of the undamped modes arising from the introduction of damping may be neglected in applying these preliminary design methods, except when dissimilar modes of these lightly damped, complex aircraft-type structures have identical or nearly identical natural frequencies. In such cases, it is shown that a relatively simple, additional interaction calculation between pairs of modes exhibiting this 'modal response' phenomenon suffices in the prediction of interacting modal damping fractions. The accuracy of the methods is shown to be very good to excellent, depending on the normal natural frequency separation of the system modes, thereby permitting a relatively simple preliminary design approach. This approach is shown to be a natural precursor to elaborate finite element, digital computer design computations in evaluating the type, quantity, and location of damping treatment.
New aircraft configurations handling qualities studies based on the aerodynamic invariant concept
NASA Astrophysics Data System (ADS)
Bazile, J.
2013-12-01
This paper proposes an innovative approach to go deeper in the Handling Qualities knowledge for New Aircraft Configurations based on the Aerodynamic Invariant Concept. By manipulating the Doublet Lattice Method for aerodynamic derivatives computation, an Aerodynamic Invariant can be highlighted. It contributes to many aircraft dynamics parameters and can be considered as "key driver" of the longitudinal aircraft dynamics. The aim of this new approach is to study the impact of this aerodynamic invariant on aircraft Handling Qualities and to ask the question: "Could this aerodynamic invariant be used in parallel with Performance in the conceptual design phase to "seek" New Aircraft configurations capable of achieving further Handling Qualities improvement with Performance benefits?" The enclosed results highlight that the aerodynamic invariant could allow to improve and to optimize the aircraft Handling Qualities by relaxing the aircraft dynamics stability.
Not Available
1992-01-01
The present conference on structural dynamics encompasses finite-element analyses of rotorcraft vibration, spacecraft dynamics, dynamic analyses, rotor aeroelasticity, rotorcraft dynamics, damping, control analysis and experiments, and experimental dynamics and testing. Specific issues addressed include NASA/industry design-analysis methods for vibrations, controlling a large flexible structure to mimic a rigid one, the dynamic response of rapidly heated space structures, interval prediction in structural dynamic analysis, mode localization in computer disk drives, and a discrete transfer-matrix method for rotating beams. Also addressed are the dynamics of axially moving continua on an elastic foundation, stiffness and stress in a fluid-filled circular diaphragm, linear structure control by the modal force technique, directional filters for sensing 1D structural dynamics, and an adaptive multilevel substructuring method for efficient modeling of complex structures.
Aerodynamic Reconstruction Applied to Parachute Test Vehicle Flight Data Analysis
NASA Technical Reports Server (NTRS)
Cassady, Leonard D.; Ray, Eric S.; Truong, Tuan H.
2013-01-01
The aerodynamics, both static and dynamic, of a test vehicle are critical to determining the performance of the parachute cluster in a drop test and for conducting a successful test. The Capsule Parachute Assembly System (CPAS) project is conducting tests of NASA's Orion Multi-Purpose Crew Vehicle (MPCV) parachutes at the Army Yuma Proving Ground utilizing the Parachute Test Vehicle (PTV). The PTV shape is based on the MPCV, but the height has been reduced in order to fit within the C-17 aircraft for extraction. Therefore, the aerodynamics of the PTV are similar, but not the same as, the MPCV. A small series of wind tunnel tests and computational fluid dynamics cases were run to modify the MPCV aerodynamic database for the PTV, but aerodynamic reconstruction of the flights has proven an effective source for further improvements to the database. The acceleration and rotational rates measured during free flight, before parachute inflation but during deployment, were used to con rm vehicle static aerodynamics. A multibody simulation is utilized to reconstruct the parachute portions of the flight. Aerodynamic or parachute parameters are adjusted in the simulation until the prediction reasonably matches the flight trajectory. Knowledge of the static aerodynamics is critical in the CPAS project because the parachute riser load measurements are scaled based on forebody drag. PTV dynamic damping is critical because the vehicle has no reaction control system to maintain attitude - the vehicle dynamics must be understood and modeled correctly before flight. It will be shown here that aerodynamic reconstruction has successfully contributed to the CPAS project.
A Generic Nonlinear Aerodynamic Model for Aircraft
NASA Technical Reports Server (NTRS)
Grauer, Jared A.; Morelli, Eugene A.
2014-01-01
A generic model of the aerodynamic coefficients was developed using wind tunnel databases for eight different aircraft and multivariate orthogonal functions. For each database and each coefficient, models were determined using polynomials expanded about the state and control variables, and an othgonalization procedure. A predicted squared-error criterion was used to automatically select the model terms. Modeling terms picked in at least half of the analyses, which totalled 45 terms, were retained to form the generic nonlinear aerodynamic (GNA) model. Least squares was then used to estimate the model parameters and associated uncertainty that best fit the GNA model to each database. Nonlinear flight simulations were used to demonstrate that the GNA model produces accurate trim solutions, local behavior (modal frequencies and damping ratios), and global dynamic behavior (91% accurate state histories and 80% accurate aerodynamic coefficient histories) under large-amplitude excitation. This compact aerodynamics model can be used to decrease on-board memory storage requirements, quickly change conceptual aircraft models, provide smooth analytical functions for control and optimization applications, and facilitate real-time parametric system identification.
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.
NASA Astrophysics Data System (ADS)
Mantha, Sriteja; Yethiraj, Arun
2016-02-01
The properties of water under confinement are of practical and fundamental interest. In this work, we study the properties of water in the self-assembled lyotropic phases of Gemini surfactants with a focus on testing the standard analysis of quasi-elastic neutron scattering (QENS) experiments. In QENS experiments, the dynamic structure factor is measured and fit to models to extract the translational diffusion constant, DT, and rotational relaxation time, τR. We test this procedure by using simulation results for the dynamic structure factor, extracting the dynamic parameters from the fit as is typically done in experiments, and comparing the values to those directly measured in the simulations. We find that the de-coupling approximation, where the intermediate scattering function is assumed to be a product of translational and rotational contributions, is quite accurate. The jump-diffusion and isotropic rotation models, however, are not accurate when the degree of confinement is high. In particular, the exponential approximations for the intermediate scattering function fail for highly confined water and the values of DT and τR can differ from the measured value by as much as a factor of two. Other models have more fit parameters, however, and with the range of energies and wave-vectors accessible to QENS, the typical analysis appears to be the best choice. In the most confined lamellar phase, the dynamics are sufficiently slow that QENS does not access a large enough time scale.
Structure and dynamics of ultrathin organic films
NASA Astrophysics Data System (ADS)
Kiktyeva, Tatyana A.
Existing and newly developed nonlinear optical methods have been used to characterize molecular structure, orientation and dynamics at interfaces. Optical second harmonic generation (SHG) studies have been conducted on molecular films of the organic dyes, rhodamine 6G and malachite green, adsorbed at the fused silica/air interface. The second harmonic response from the organic dye films was found to be a non-monotonic function of the surface concentration with discontinuities corresponding to completion of successive monolayers. This behavior reflects ordering of molecular adlayers, which extends for several layers. Polarized SHG studies in conjunction with optical absorbance and fluorescence measurements were used to determine the type of interactions responsible for the adsorption in the ordered layers. The results indicate that the well-defined order within the first layer is due to the specific adsorbate-substrate interactions. Orientation in subsequent layers is teed by adsorbate-adsorbate interactions, dependent on the nature of the adsorbate and consequently on its orientation within the first layer. These results provide a direct measure of the extent of the interfacial ordering and molecular interactions at the solid/air interface and can be used to determine an adsorbate's filling factor. Time and frequency resolved vibrational spectra of a monolayer of amphiphilic molecules at the CaF2/air interface were investigated using infrared-visible sum frequency generation. Vibrational wave packet dynamics following coherent excitation of CH3 vibrational modes with broad bandwidth infrared pulses is reported. The induced macroscopic polarization displays quantum interference effects (quantum beats) and decays on a time scale dependent on the nature of the interfacial environment. These observations provide a link between the degree of structural order of the monolayer and the vibrational coherence lifetime. Monitoring interfacial wave packet dynamics represents a
Optimizing Dynamical Network Structure for Pinning Control
Orouskhani, Yasin; Jalili, Mahdi; Yu, Xinghuo
2016-01-01
Controlling dynamics of a network from any initial state to a final desired state has many applications in different disciplines from engineering to biology and social sciences. In this work, we optimize the network structure for pinning control. The problem is formulated as four optimization tasks: i) optimizing the locations of driver nodes, ii) optimizing the feedback gains, iii) optimizing simultaneously the locations of driver nodes and feedback gains, and iv) optimizing the connection weights. A newly developed population-based optimization technique (cat swarm optimization) is used as the optimization method. In order to verify the methods, we use both real-world networks, and model scale-free and small-world networks. Extensive simulation results show that the optimal placement of driver nodes significantly outperforms heuristic methods including placing drivers based on various centrality measures (degree, betweenness, closeness and clustering coefficient). The pinning controllability is further improved by optimizing the feedback gains. We also show that one can significantly improve the controllability by optimizing the connection weights. PMID:27067020
Optimizing Dynamical Network Structure for Pinning Control.
Orouskhani, Yasin; Jalili, Mahdi; Yu, Xinghuo
2016-01-01
Controlling dynamics of a network from any initial state to a final desired state has many applications in different disciplines from engineering to biology and social sciences. In this work, we optimize the network structure for pinning control. The problem is formulated as four optimization tasks: i) optimizing the locations of driver nodes, ii) optimizing the feedback gains, iii) optimizing simultaneously the locations of driver nodes and feedback gains, and iv) optimizing the connection weights. A newly developed population-based optimization technique (cat swarm optimization) is used as the optimization method. In order to verify the methods, we use both real-world networks, and model scale-free and small-world networks. Extensive simulation results show that the optimal placement of driver nodes significantly outperforms heuristic methods including placing drivers based on various centrality measures (degree, betweenness, closeness and clustering coefficient). The pinning controllability is further improved by optimizing the feedback gains. We also show that one can significantly improve the controllability by optimizing the connection weights. PMID:27067020
Optimizing Dynamical Network Structure for Pinning Control
NASA Astrophysics Data System (ADS)
Orouskhani, Yasin; Jalili, Mahdi; Yu, Xinghuo
2016-04-01
Controlling dynamics of a network from any initial state to a final desired state has many applications in different disciplines from engineering to biology and social sciences. In this work, we optimize the network structure for pinning control. The problem is formulated as four optimization tasks: i) optimizing the locations of driver nodes, ii) optimizing the feedback gains, iii) optimizing simultaneously the locations of driver nodes and feedback gains, and iv) optimizing the connection weights. A newly developed population-based optimization technique (cat swarm optimization) is used as the optimization method. In order to verify the methods, we use both real-world networks, and model scale-free and small-world networks. Extensive simulation results show that the optimal placement of driver nodes significantly outperforms heuristic methods including placing drivers based on various centrality measures (degree, betweenness, closeness and clustering coefficient). The pinning controllability is further improved by optimizing the feedback gains. We also show that one can significantly improve the controllability by optimizing the connection weights.
Dynamics of a complex streamer structure
NASA Astrophysics Data System (ADS)
Lehtinen, N. G.; Ostgaard, N.; Inan, U.
2014-12-01
Streamer corona formation and propagation is an important process in the development of lightning. In order to understand its dynamics, the streamer front velocity is calculated in a 1D model with curvature. We show that streamers may only propagate only the presence of mechanisms such as electron drift, electron diffusion and photoionization. The results indicate, in particular, that: (1) the effect of photoionization on the streamer velocity for both positive and negative streamers is mostly determined by the photoionization length, with a weaker dependence on the amount of photoionization; (2) the electron drift may increase the velocity of the negative streamers but has an opposite effect on the positive streamers; (3) the contributions of photoionization and electron diffusion to the velocity are decreased for positive curvature, i.e., convex fronts, while the contribution of electron drift is independent of curvature. These results are used in a fractal model in which the front propagation velocity is simulated as the cluster growth probability [Niemeyer et al, 1984, doi:10.1103/PhysRevLett.52.1033]. In the case when the photoionization is the main mechanism which determines the streamer propagation, the emerging transverse size of the streamers is of the order of the photoionization length, and at the larger scale the streamer structure is a fractal similar to the one obtained in a diffusion-limited aggregation system.
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.
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.
NASA Technical Reports Server (NTRS)
Cole, Jennifer Hansen
2010-01-01
This slide presentation reviews some of the basic principles of aerodynamics. Included in the presentation are: a few demonstrations of the principles, an explanation of the concepts of lift, drag, thrust and weight, a description of Bernoulli's principle, the concept of the airfoil (i.e., the shape of the wing) and how that effects lift, and the method of controlling an aircraft by manipulating the four forces using control surfaces.
A NASTRAN-based computer program for structural dynamic analysis of Horizontal Axis Wind Turbines
NASA Technical Reports Server (NTRS)
Lobitz, Don W.
1995-01-01
This paper describes a computer program developed for structural dynamic analysis of horizontal axis wind turbines (HAWT's). It is based on the finite element method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of the tower end rotor, which are treated in NASTRAN as separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a constant angular velocity. The two structures are subsequently joined together (external to NASTRAN) using a time-dependent transformation consistent with the hub configuration. Aerodynamic loads are computed with an established flow model based on strip theory. Aeroelastic effects are included by incorporating the local velocity and twisting deformation of the blade in the load computation. The turbulent nature of the wind, both in space and time, is modeled by adding in stochastic wind increments. The resulting equations of motion are solved in the time domain using the implicit Newmark-Beta integrator. Preliminary comparisons with data from the Boeing/NASA MOD2 HAWT indicate that the code is capable of accurately and efficiently predicting the response of HAWT's driven by turbulent winds.
A NASTRAN-based computer program for structural dynamic analysis of Horizontal Axis Wind Turbines
NASA Astrophysics Data System (ADS)
Lobitz, Don W.
1995-05-01
This paper describes a computer program developed for structural dynamic analysis of horizontal axis wind turbines (HAWT's). It is based on the finite element method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of the tower end rotor, which are treated in NASTRAN as separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a constant angular velocity. The two structures are subsequently joined together (external to NASTRAN) using a time-dependent transformation consistent with the hub configuration. Aerodynamic loads are computed with an established flow model based on strip theory. Aeroelastic effects are included by incorporating the local velocity and twisting deformation of the blade in the load computation. The turbulent nature of the wind, both in space and time, is modeled by adding in stochastic wind increments. The resulting equations of motion are solved in the time domain using the implicit Newmark-Beta integrator. Preliminary comparisons with data from the Boeing/NASA MOD2 HAWT indicate that the code is capable of accurately and efficiently predicting the response of HAWT's driven by turbulent winds.
Comparison of piezoelectric systems and aerodynamic systems for aircraft vibration alleviation
NASA Astrophysics Data System (ADS)
Becker, Juergen; Luber, Wolfgang G.
1998-06-01
A comparison of active smart structure - piezoelectric control system and aerodynamic active systems for vibration alleviation and elastic mode damping of a military aircraft structure is presented. The vibration alleviation systems which are operative at flight in turbulence or during maneuvers at high incidence corresponding to severe buffeting conditions are under investigation by DASA as a part of research study on advanced aircraft structures. The active systems for elastic mode damping are designed as digital systems to provide vibration alleviation and have an interface to the flight control system (FCS) or are directly part of the FCS. The sensor concept of all different systems is the same as the sensor concept used for the FCS with the corresponding benefits of redundancy and safety. The design of systems and the comparisons of system properties are based on open and closed loop response calculations, performed with the dynamic model of the total aircraft including coupling of flight mechanics, structural dynamics, FCS dynamics and hydraulic actuator or piezo-actuator dynamics. Aerodynamic systems, like active foreplane and flap concepts, rudder and auxiliary rudder concepts, and piezoelectric systems, like piezo interface at the interconnection fin to rear fuselage and integrated piezo concepts are compared. Besides the essential effects on flexible aircraft mode stability and vibration alleviation factors system complexity and safety aspects are described.
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.
Dynamics and structure of turbulent premixed flames
NASA Technical Reports Server (NTRS)
Bilger, R. W.; Swaminathan, N.; Ruetsch, G. R.; Smith, N. S. A.
1995-01-01
In earlier work (Mantel & Bilger, 1994) the structure of the turbulent premixed flame was investigated using statistics based on conditional averaging with the reaction progress variable as the conditioning variable. The DNS data base of Trouve and Poinsot (1994) was used in this investigation. Attention was focused on the conditional dissipation and conditional axial velocity in the flame with a view to modeling these quantities for use in the conditional moment closure (CMC) approach to analysis of kinetics in premixed flames (Bilger, 1993). Two remarkable findings were made: there was almost no acceleration of the axial velocity in the flame front itself; and the conditional scalar dissipation remained as high, or higher, than that found in laminar premixed flames. The first finding was surprising since in laminar flames all the fluid acceleration occurs through the flame front, and this could be expected also for turbulent premixed flames at the flamelet limit. The finding gave hope of inventing a new approach to the dynamics of turbulent premixed flames through use of rapid distortion theory or an unsteady Bernoulli equation. This could lead to a new second order closure for turbulent premixed flames. The second finding was contrary to our measurements with laser diagnostics in lean hydrocarbon flames where it is found that conditional scalar dissipation drops dramatically below that for laminar flamelets when the turbulence intensity becomes high. Such behavior was not explainable with a one-step kinetic model, even at non-unity Lewis number. It could be due to depletion of H2 from the reaction zone by preferential diffusion. The capacity of the flame to generate radicals is critically dependent on the levels of H2 present (Bilger, et al., 1991). It seemed that a DNS computation with a multistep reduced mechanism would be worthwhile if a way could be found to make this feasible. Truly innovative approaches to complex problems often come only when there is the
Structural Dynamics Branch research and accomplishments for FY 1990
NASA Technical Reports Server (NTRS)
1991-01-01
Presented here is a collection of FY 1990 research highlights from the Structural Dynamics Branch at the NASA Lewis Research Center. Highlights are from the branch's major work areas: aeroelasticity, vibration control, dynamic systems, and computational structural methods. A listing is given of FY 1990 branch publications.
Structural dynamics branch research and accomplishments for FY 1988
NASA Technical Reports Server (NTRS)
1989-01-01
Fiscal year 1988 research highlights from the Structural Dynamics Branch at NASA Lewis Research Center are described. Highlights from the branch's major work areas -- aeroelasticity, vibration control, dynamic systems, and computational structural methods -- are included as well as a complete listing of the FY 88 branch publications.
Structural dynamics branch research and accomplishments to FY 1992
NASA Technical Reports Server (NTRS)
Lawrence, Charles
1992-01-01
This publication contains a collection of fiscal year 1992 research highlights from the Structural Dynamics Branch at NASA LeRC. Highlights from the branch's major work areas--Aeroelasticity, Vibration Control, Dynamic Systems, and Computational Structural Methods are included in the report as well as a listing of the fiscal year 1992 branch publications.
Structural dynamics branch research and accomplishments for fiscal year 1987
NASA Technical Reports Server (NTRS)
1988-01-01
This publication contains a collection of fiscal year 1987 research highlights from the Structural Dynamics Branch at NASA Lewis Research Center. Highlights from the branch's four major work areas, Aeroelasticity, Vibration Control, Dynamic Systems, and Computational Structural Methods, are included in the report as well as a complete listing of the FY87 branch publications.
Structure of the Benzene - by Dynamics
NASA Astrophysics Data System (ADS)
Schnell, Melanie; Erlekam, Undine; Von Helden, Gert; Meijer, Gerard; Bunker, Philip R.; Grabow, Jens-Uwe; Van Der Avoird, Ad
2013-06-01
The benzene dimer is the prototype system for Van der Waals interactions between aromatic molecules. Here, we report a joint experimental and theoretical study regarding normal (C_6H_6)_2 and the partially deuterated (C_6D_6)(C_6H_6) isotopologue. Interestingly, although its tilted T-shaped equilibrium structure corresponds to an asymmetric rotor, both isotopologues exhibit the rotational spectrum of a symmetric rotor, with a characteristic quartet splitting pattern due to internal tunneling motions: each transition exhibits a -2 : -1 : +1 : +2 splitting ratio with respect to its center. We unravel these splittings with the aid of the unrivalled resolution of the supersonic-jet FT-microwave experiment which provides accurate split-patterns, by means of a reduced-dimensionality model for the internal dynamics of the (rotating) dimer that reproduces them. They turn out to originate from a concerted tunneling mechanism involving both the hindered rotation of the stem in the T-shaped dimer around its sixfold axis and tilt tunneling. We also show that the observed intensities of the tunneling components are not solely determined by nuclear spin statistical weights. Rather, taking small differences in the dissociation energies of different dimer nuclear spin species into account, the kinetics of the dimer formation and equilibration can bias the populations of the tunneling symmetry species. Using Stark shift measurements, we determine the dipole moment of (C_6H_6)_2 to be μ = 0.580(51) D, in agreement with the value of 0.63 D calculated with the assumption that the dipole moment is mainly determined by the dipoles induced in both monomers by the electric field of the quadrupole of the other monomer. M. Schnell, U. Erlekam, P. R. Bunker, G. v. Helden, J.-U. Grabow, G. Meijer, A. van der Avoird, Angew. Chem. Int. Ed., DOI: 10.1002/anie.201300653 and 10.1002/ange.201300653
AIAA Dynamics Specialists Conference, Dallas, TX, Apr. 16, 17, 1992, Technical Papers
Not Available
1992-01-01
This conference presents papers in the fields of spacecraft dynamics, the control of structures, the active flexible wing, flutter characteristics, and rotary-wing aeroelasticity. Also considered are control-structure interaction, unsteady aerodynamics, fixed-wing aeroelasticity, structural dynamics systems, and CSI-sensors and actuators.
Aerodynamic shape optimization using control theory
NASA Technical Reports Server (NTRS)
Reuther, James
1996-01-01
Aerodynamic shape design has long persisted as a difficult scientific challenge due its highly nonlinear flow physics and daunting geometric complexity. However, with the emergence of Computational Fluid Dynamics (CFD) it has become possible to make accurate predictions of flows which are not dominated by viscous effects. It is thus worthwhile to explore the extension of CFD methods for flow analysis to the treatment of aerodynamic shape design. Two new aerodynamic shape design methods are developed which combine existing CFD technology, optimal control theory, and numerical optimization techniques. Flow analysis methods for the potential flow equation and the Euler equations form the basis of the two respective design methods. In each case, optimal control theory is used to derive the adjoint differential equations, the solution of which provides the necessary gradient information to a numerical optimization method much more efficiently then by conventional finite differencing. Each technique uses a quasi-Newton numerical optimization algorithm to drive an aerodynamic objective function toward a minimum. An analytic grid perturbation method is developed to modify body fitted meshes to accommodate shape changes during the design process. Both Hicks-Henne perturbation functions and B-spline control points are explored as suitable design variables. The new methods prove to be computationally efficient and robust, and can be used for practical airfoil design including geometric and aerodynamic constraints. Objective functions are chosen to allow both inverse design to a target pressure distribution and wave drag minimization. Several design cases are presented for each method illustrating its practicality and efficiency. These include non-lifting and lifting airfoils operating at both subsonic and transonic conditions.
Spectral response of multilayer optical structures to dynamic mechanical loading
NASA Astrophysics Data System (ADS)
Scripka, David; LeCroy, Garrett; Summers, Christopher J.; Thadhani, Naresh N.
2015-05-01
A computational study of Distributed Bragg Reflectors (DBR) and Optical Microcavities (OMC) was conducted to ascertain their potential as time-resolved mesoscale sensors due to their unique structure-driven spectral characteristics. Shock wave propagation simulations of polymer-based DBRs and glass/ceramic-based OMCs were coupled with spectral response calculations to demonstrate the combined dynamic mechanical and spectral response of the structures. Clear spectral shifts in both structures are predicted as a function of dynamic loading magnitude. Potential applications of the structures include high spatial and temporal resolution surface maps of material states, and in-situ probing of material interfaces during dynamic loading.
NASA Astrophysics Data System (ADS)
Shortis, Mark R.; Robson, Stuart; Jones, Thomas W.; Goad, William K.; Lunsford, Charles B.
2016-06-01
Aerospace engineers require measurements of the shape of aerodynamic surfaces and the six degree of freedom (6DoF) position and orientation of aerospace models to analyse structural dynamics and aerodynamic forces. The measurement technique must be non-contact, accurate, reliable, have a high sample rate and preferably be non-intrusive. Close range photogrammetry based on multiple, synchronised, commercial-off-the-shelf digital cameras can supply surface shape and 6DoF data at 5-15Hz with customisable accuracies. This paper describes data acquisition systems designed and implemented at NASA Langley Research Center to capture surface shapes and 6DoF data. System calibration and data processing techniques are discussed. Examples of experiments and data outputs are described.
Details of insect wing design and deformation enhance aerodynamic function and flight efficiency.
Young, John; Walker, Simon M; Bomphrey, Richard J; Taylor, Graham K; Thomas, Adrian L R
2009-09-18
Insect wings are complex structures that deform dramatically in flight. We analyzed the aerodynamic consequences of wing deformation in locusts using a three-dimensional computational fluid dynamics simulation based on detailed wing kinematics. We validated the simulation against smoke visualizations and digital particle image velocimetry on real locusts. We then used the validated model to explore the effects of wing topography and deformation, first by removing camber while keeping the same time-varying twist distribution, and second by removing camber and spanwise twist. The full-fidelity model achieved greater power economy than the uncambered model, which performed better than the untwisted model, showing that the details of insect wing topography and deformation are important aerodynamically. Such details are likely to be important in engineering applications of flapping flight. PMID:19762645
(Inter-),Network Structure and DynamicS
NASA Astrophysics Data System (ADS)
Rutten, R. J.
1999-09-01
The dynamical nature of the low solar atmosphere outside active regions is emphasized by recent observations and simulations alike. La Palma images, MDI maps, SUMER spectra, TRACE movies, hydrodynamic shock simulations and magnetohydrodynamic sheet simulations all impart non-quiet behavior to the "quiet Sun". This review begins with a brief summary of current insights and then focuses on various quiet-Sun questions that seem pertinent and solvable.
An Aerodynamic Analysis of a Spinning Missile with Dithering Canards
NASA Technical Reports Server (NTRS)
Meakin, Robert L.; Nygaard, Tor A.
2003-01-01
A generic spinning missile with dithering canards is used to demonstrate the utility of an overset structured grid approach for simulating the aerodynamics of rolling airframe missile systems. The approach is used to generate a modest aerodynamic database for the generic missile. The database is populated with solutions to the Euler and Navier-Stokes equations. It is used to evaluate grid resolution requirements for accurate prediction of instantaneous missile loads and the relative aerodynamic significance of angle-of-attack, canard pitching sequence, viscous effects, and roll-rate effects. A novel analytical method for inter- and extrapolation of database results is also given.
The effects of bolted joints on dynamic response of structures
NASA Astrophysics Data System (ADS)
Zaman, I.; Khalid, A.; Manshoor, B.; Araby, S.; Ghazali, M. I.
2013-12-01
Joint is an universal fastening technology for structural members; in particular bolted joints are extensively used in mechanical structures due to their simple maintenance and low cost. However, the components of bolted joints are imperative because failure could be catastrophic and endanger lives. Hence, in this study, the effects of bolted joints on vibrating structures are investigated by determining the structural dynamic properties, such as mode shapes, damping ratios and natural frequencies, and these are compared with the monolithic structures (welding). Two approaches of experimental rigs are developed: a beam and a frame where both are subjected to dynamic loading. The analysis reveals the importance of bolted joints in increasing the damping properties and minimizing the vibration magnitude of structures, this indicates the significant influence of bolted joints on the dynamic behaviour of assembled structures. The outcome of this study provides a good model for predicting the experimental variable response in different types of structural joints.
Aerodynamic Design of Wing based on Humpback Whale Flipper
NASA Astrophysics Data System (ADS)
Akram, Saif; Baig, Faisal
2013-11-01
The tubercles provide a bio-inspired design that has commercial viability for wing-like structures. Wind tunnel tests at low speeds of model humpback flippers with leading-edge tubercles have demonstrated improvements tubercles make, such as a staggering 32% reduction in drag, 8% improvement in lift, and a 40% increase in angle of attack over smooth flippers before stalling. The tubercles on the leading edge act as a passive-flow control device that improves the performance and maneuverability of the flipper. Possible fluid-dynamic mechanisms for improved performance include delay of stall through generation of a vortex and modification of the boundary layer, and increase in effective span by reduction of both spanwise flow and strength of the tip vortex. In the present work, numerical investigation of a 3D wing with scalloped leading edge inspired by the humpback whale flipper is carried out at high subsonic speeds with variation in angle of attack from 0 to 25 degrees. The effect of using different turbulence models is also investigated in order to attain a better understanding of mechanism(s) responsible for improved aerodynamic performance. This new understanding of humpback whale flipper aerodynamics has strong implications for wing design.
Reconstruction of dynamic structural inputs in the presence of noise
Bateman, V.I.; Solomon, O.M. Jr.
1986-08-01
This report describes a technique to reconstruct dynamic structural inputs by deconvolution of measured data. The structure to which this technique has been applied is a mild steel bar (3 in diameter and 60 in. long) with a conical nose which provides some geometric simulation of penetrating structures which are used in field test. The deconvolution technique successfully reconstructs dynamic inputs to the bar with and without additive white noise present in the measured response.
METAPOPULATION STRUCTURE AND DYNAMICS OF POND BREEDING
Our review indicates that pond breeding amphibians exhibit highly variable spatial and temporal population dynamics, such that no single generalized model can realistically describe these animals. We propose that consideration of breeding pond permanence, and adaptations to pond ...
Influence of hinge point on flexible flap aerodynamic performance
NASA Astrophysics Data System (ADS)
Y Zhao, H.; Ye, Z.; Wu, P.; Li, C.
2013-12-01
Large scale wind turbines lead to increasing blade lengths and weights, which presents new challenges for blade design. This paper selects NREL S809 airfoil, uses the parameterized technology to realize the flexible trailing edge deformation, researches the static aerodynamic characteristics of wind turbine blade airfoil with flexible deformation, and the dynamic aerodynamic characteristics in the process of continuous deformation, analyses the influence of hinge point position on flexible flap aerodynamic performance, in order to further realize the flexible wind turbine blade design and provides some references for the active control scheme. The results show that compared with the original airfoil, proper trailing edge deformation can improve the lift coefficient, reduce the drag coefficient, and thereby more efficiently realize flow field active control. With hinge point moving forward, total aerodynamic performance of flexible flap improves. Positive swing angle can push the transition point backward, thus postpones the occurrence of the transition phenomenon.
Computational Aerodynamic Analysis of Offshore Upwind and Downwind Turbines
Zhao, Qiuying; Sheng, Chunhua; Afjeh, Abdollah
2014-01-01
Aerodynamic interactions of the model NREL 5 MW offshore horizontal axis wind turbines (HAWT) are investigated using a high-fidelity computational fluid dynamics (CFD) analysis. Four wind turbine configurations are considered; three-bladed upwind and downwind and two-bladed upwind and downwind configurations, which operate at two different rotor speeds of 12.1 and 16 RPM. In the present study, both steady and unsteady aerodynamic loads, such as the rotor torque, blade hub bending moment, and base the tower bending moment of the tower, are evaluated in detail to provide overall assessment of different wind turbine configurations. Aerodynamic interactions between the rotor and tower are analyzed,more » including the rotor wake development downstream. The computational analysis provides insight into aerodynamic performance of the upwind and downwind, two- and three-bladed horizontal axis wind turbines.« less
Freight Wing Trailer Aerodynamics
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.
Numerical Aerodynamic Simulation (NAS)
NASA Technical Reports Server (NTRS)
Peterson, V. L.; Ballhaus, W. F., Jr.; Bailey, F. R.
1983-01-01
The history of the Numerical Aerodynamic Simulation Program, which is designed to provide a leading-edge capability to computational aerodynamicists, is traced back to its origin in 1975. Factors motivating its development and examples of solutions to successively refined forms of the governing equations are presented. The NAS Processing System Network and each of its eight subsystems are described in terms of function and initial performance goals. A proposed usage allocation policy is discussed and some initial problems being readied for solution on the NAS system are identified.
Flight Test Maneuvers for Efficient Aerodynamic Modeling
NASA Technical Reports Server (NTRS)
Morelli, Eugene A.
2011-01-01
Novel flight test maneuvers for efficient aerodynamic modeling were developed and demonstrated in flight. Orthogonal optimized multi-sine inputs were applied to aircraft control surfaces to excite aircraft dynamic response in all six degrees of freedom simultaneously while keeping the aircraft close to chosen reference flight conditions. Each maneuver was designed for a specific modeling task that cannot be adequately or efficiently accomplished using conventional flight test maneuvers. All of the new maneuvers were first described and explained, then demonstrated on a subscale jet transport aircraft in flight. Real-time and post-flight modeling results obtained using equation-error parameter estimation in the frequency domain were used to show the effectiveness and efficiency of the new maneuvers, as well as the quality of the aerodynamic models that can be identified from the resultant flight data.
Mimicking the humpback whale: An aerodynamic perspective
NASA Astrophysics Data System (ADS)
Aftab, S. M. A.; Razak, N. A.; Mohd Rafie, A. S.; Ahmad, K. A.
2016-07-01
This comprehensive review aims to provide a critical overview of the work on tubercles in the past decade. The humpback whale is of interest to aerodynamic/hydrodynamic researchers, as it performs manoeuvres that baffle the imagination. Researchers have attributed these capabilities to the presence of lumps, known as tubercles, on the leading edge of the flipper. Tubercles generate a unique flow control mechanism, offering the humpback exceptional manoeuverability. Experimental and numerical studies have shown that the flow pattern over the tubercle wing is quite different from conventional wings. Research on the Tubercle Leading Edge (TLE) concept has helped to clarify aerodynamic issues such as flow separation, tonal noise and dynamic stall. TLE shows increased lift by delaying and restricting spanwise separation. A summary of studies on different airfoils and reported improvement in performance is outlined. The major contributions and limitations of previous work are also reported.
Aerodynamics of the Mars Microprobe Entry Vehicles
NASA Technical Reports Server (NTRS)
Mitcheltree, R. A.; Moss, J. N.; Cheatwood, F. M.; Greene, F. A.; Braun, R. D.
1997-01-01
The selection of the unique aeroshell shape for the Mars Microprobes is discussed. A description of its aerodynamics in hypersonic rarefied, hypersonic continuum, supersonic and transonic flow regimes is then presented. This description is based on Direct Simulation Monte Carlo analyses in the rarefied-flow regime, thermochemical nonequilibrium Computational Fluid Dynamics in the hypersonic regime, existing wind tunnel data in the supersonic and transonic regime, additional computational work in the transonic regime, and finally, ballistic range data. The aeroshell is shown to possess the correct combination of aerodynamic stability and drag to convert the probe's initial tumbling attitude and high velocity at atmospheric-interface into the desired surface-impact orientation and velocity.
Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Technology Development Overview
NASA Technical Reports Server (NTRS)
Hughes, Stephen J.; Cheatwood, F. McNeil; Calomino, Anthony M.; Wright, Henry S.
2013-01-01
The successful flight of the Inflatable Reentry Vehicle Experiment (IRVE)-3 has further demonstrated the potential value of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology. This technology development effort is funded by NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). This paper provides an overview of a multi-year HIAD technology development effort, detailing the projects completed to date and the additional testing planned for the future. The effort was divided into three areas: Flexible Systems Development (FSD), Mission Advanced Entry Concepts (AEC), and Flight Validation. FSD consists of a Flexible Thermal Protection Systems (FTPS) element, which is investigating high temperature materials, coatings, and additives for use in the bladder, insulator, and heat shield layers; and an Inflatable Structures (IS) element which includes manufacture and testing (laboratory and wind tunnel) of inflatable structures and their associated structural elements. AEC consists of the Mission Applications element developing concepts (including payload interfaces) for missions at multiple destinations for the purpose of demonstrating the benefits and need for the HIAD technology as well as the Next Generation Subsystems element. Ground test development has been pursued in parallel with the Flight Validation IRVE-3 flight test. A larger scale (6m diameter) HIAD inflatable structure was constructed and aerodynamically tested in the National Full-scale Aerodynamics Complex (NFAC) 40ft by 80ft test section along with a duplicate of the IRVE-3 3m article. Both the 6m and 3m articles were tested with instrumented aerodynamic covers which incorporated an array of pressure taps to capture surface pressure distribution to validate Computational Fluid Dynamics (CFD) model predictions of surface pressure distribution. The 3m article also had a duplicate IRVE-3 Thermal Protection System (TPS) to test in addition to testing with the
Relations between structural and dynamic thermal characteristics of building walls
Kossecka, E.; Kosny, J.
1996-10-01
The effect of internal thermal structure on dynamic characteristics of walls is analyzed. The concept of structure factors is introduced and the conditions they impose on response factors are given. Simple examples of multilayer walls, representing different types of thermal resistance and capacity distribution, are analyzed to illustrate general relations between structure factors and response factors. The idea of the ``thermally equivalent wall``, a plane multilayer structure, with dynamic characteristics similar to those of a complex structure, in which three-dimensional heat flow occurs, is presented.
Recent Progress in Heliogyro Solar Sail Structural Dynamics
NASA Technical Reports Server (NTRS)
Wilkie, William K.; Warren, Jerry E.; Horta, Lucas G.; Juang, Jer-Nan; Gibbs, Samuel C.; Dowell, E.; Guerrant, Daniel; Lawrence Dale
2014-01-01
Results from recent National Aeronautics and Space Administration (NASA) research on the structural dynamics and control characteristics of heliogyro solar sails are summarized. Specific areas under investigation include coupled nonlinear finite element analysis of heliogyro membrane blade with solar radiation pressure effects, system identification of spinning membrane structures, solarelastic stability analysis of heliogyro solar sails, including stability during blade deployment, and results from small-scale in vacuo dynamics experiments with spinning high-aspect ratio membranes. A low-cost, rideshare payload heliogyro technology demonstration mission concept, used as a mission context for these heliogyro structural dynamics and solarelasticity investigations, is also described.
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.
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.
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)
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…
NASA Technical Reports Server (NTRS)
Egolfopoulos, Fokion N.
1995-01-01
The first objective of the program is to introduce the meritorious counterflow methodology in microgravity in order to quantify the steady and unsteady characteristics of weakly-burning premixed and diffusion flames for a wide variety of conditions including elevated pressures. Subsequently, through detailed modeling and comparisons with the experimental data, to provide physical insight into the elementary mechanisms controlling the flame response. The configuration offers good control over the parameters of interest and can be modelled closely. The knowledge which will be gained from the counterflow flames will be subsequently used to analyze near-limit phenomena related to other configurations by conducting detailed numerical simulations including multidimensional ones. Among the problems to be analyzed are the downward and upward propagation of near-limit flames in tubes and phenomena observed in spherical and cylindrical geometries.
Ion-ion dynamic structure factor of warm dense mixtures.
Gill, N M; Heinonen, R A; Starrett, C E; Saumon, D
2015-06-01
The ion-ion dynamic structure factor of warm dense matter is determined using the recently developed pseudoatom molecular dynamics method [Starrett et al., Phys. Rev. E 91, 013104 (2015)]. The method uses density functional theory to determine ion-ion pair interaction potentials that have no free parameters. These potentials are used in classical molecular dynamics simulations. This constitutes a computationally efficient and realistic model of dense plasmas. Comparison with recently published simulations of the ion-ion dynamic structure factor and sound speed of warm dense aluminum finds good to reasonable agreement. Using this method, we make predictions of the ion-ion dynamical structure factor and sound speed of a warm dense mixture-equimolar carbon-hydrogen. This material is commonly used as an ablator in inertial confinement fusion capsules, and our results are amenable to direct experimental measurement. PMID:26172810
Ion-ion dynamic structure factor of warm dense mixtures
Gill, N. M.; Heinonen, R. A.; Starrett, C. E.; Saumon, D.
2015-06-25
In this study, the ion-ion dynamic structure factor of warm dense matter is determined using the recently developed pseudoatom molecular dynamics method [Starrett et al., Phys. Rev. E 91, 013104 (2015)]. The method uses density functional theory to determine ion-ion pair interaction potentials that have no free parameters. These potentials are used in classical molecular dynamics simulations. This constitutes a computationally efficient and realistic model of dense plasmas. Comparison with recently published simulations of the ion-ion dynamic structure factor and sound speed of warm dense aluminum finds good to reasonable agreement. Using this method, we make predictions of the ion-ion dynamical structure factor and sound speed of a warm dense mixture—equimolar carbon-hydrogen. This material is commonly used as an ablator in inertial confinement fusion capsules, and our results are amenable to direct experimental measurement.
Ion-ion dynamic structure factor of warm dense mixtures
Gill, N. M.; Heinonen, R. A.; Starrett, C. E.; Saumon, D.
2015-06-25
In this study, the ion-ion dynamic structure factor of warm dense matter is determined using the recently developed pseudoatom molecular dynamics method [Starrett et al., Phys. Rev. E 91, 013104 (2015)]. The method uses density functional theory to determine ion-ion pair interaction potentials that have no free parameters. These potentials are used in classical molecular dynamics simulations. This constitutes a computationally efficient and realistic model of dense plasmas. Comparison with recently published simulations of the ion-ion dynamic structure factor and sound speed of warm dense aluminum finds good to reasonable agreement. Using this method, we make predictions of the ion-ionmore » dynamical structure factor and sound speed of a warm dense mixture—equimolar carbon-hydrogen. This material is commonly used as an ablator in inertial confinement fusion capsules, and our results are amenable to direct experimental measurement.« less
Riboswitch Structure and Dynamics by smFRET Microscopy
Suddala, Krishna C.; Walter, Nils G.
2016-01-01
Riboswitches are structured non-coding RNA elements that control the expression of their embedding messenger RNAs by sensing the intracellular concentration of diverse metabolites. As the name suggests, riboswitches are dynamic in nature so that studying their inherent conformational dynamics and ligand-mediated folding is important for understanding their mechanism of action. Single molecule fluorescence energy transfer (smFRET) microscopy is a powerful and versatile technique for studying the folding pathways and intra- and intermolecular dynamics of biological macromolecules, especially RNA. The ability of smFRET to monitor intramolecular distances and their temporal evolution make it a particularly insightful tool for probing the structure and dynamics of riboswitches. Here, we detail the general steps for using prism-based total internal reflection fluorescence (TIRF) microscopy for smFRET studies of the structure, dynamics and ligand binding mechanisms of riboswitches. PMID:25432756
NASA Technical Reports Server (NTRS)
Bales, K. S.
1983-01-01
The objectives, expected results, approach, and milestones for research projects of the IPAD Project Office and the impact dynamics, structural mechanics, and structural dynamics branches of the Structures and Dynamics Division are presented. Research facilities are described. Topics covered include computer aided design; general aviation/transport crash dynamics; aircraft ground performance; composite structures; failure analysis, space vehicle dynamics; and large space structures.
Segmenting Dynamic Human Action via Statistical Structure
ERIC Educational Resources Information Center
Baldwin, Dare; Andersson, Annika; Saffran, Jenny; Meyer, Meredith
2008-01-01
Human social, cognitive, and linguistic functioning depends on skills for rapidly processing action. Identifying distinct acts within the dynamic motion flow is one basic component of action processing; for example, skill at segmenting action is foundational to action categorization, verb learning, and comprehension of novel action sequences. Yet…
Controlled multibody dynamics simulation for large space structures
NASA Technical Reports Server (NTRS)
Housner, J. M.; Wu, S. C.; Chang, C. W.
1989-01-01
Multibody dynamics discipline, and dynamic simulation in control structure interaction (CSI) design are discussed. The use, capabilities, and architecture of the Large Angle Transient Dynamics (LATDYN) code as a simulation tool are explained. A generic joint body with various types of hinge connections; finite element and element coordinate systems; results of a flexible beam spin-up on a plane; mini-mast deployment; space crane and robotic slewing manipulations; a potential CSI test article; and multibody benchmark experiments are also described.
Membrane Protein Structure and Dynamics from NMR Spectroscopy
NASA Astrophysics Data System (ADS)
Hong, Mei; Zhang, Yuan; Hu, Fanghao
2012-05-01
We review the current state of membrane protein structure determination using solid-state nuclear magnetic resonance (NMR) spectroscopy. Multidimensional magic-angle-spinning correlation NMR combined with oriented-sample experiments has made it possible to measure a full panel of structural constraints of membrane proteins directly in lipid bilayers. These constraints include torsion angles, interatomic distances, oligomeric structure, protein dynamics, ligand structure and dynamics, and protein orientation and depth of insertion in the lipid bilayer. Using solid-state NMR, researchers have studied potassium channels, proton channels, Ca2+ pumps, G protein-coupled receptors, bacterial outer membrane proteins, and viral fusion proteins to elucidate their mechanisms of action. Many of these membrane proteins have also been investigated in detergent micelles using solution NMR. Comparison of the solid-state and solution NMR structures provides important insights into the effects of the solubilizing environment on membrane protein structure and dynamics.
Computing Nonequilibrium Conformational Dynamics of Structured Nucleic Acid Assemblies.
Sedeh, Reza Sharifi; Pan, Keyao; Adendorff, Matthew Ralph; Hallatschek, Oskar; Bathe, Klaus-Jürgen; Bathe, Mark
2016-01-12
Synthetic nucleic acids can be programmed to form precise three-dimensional structures on the nanometer-scale. These thermodynamically stable complexes can serve as structural scaffolds to spatially organize functional molecules including multiple enzymes, chromophores, and force-sensing elements with internal dynamics that include substrate reaction-diffusion, excitonic energy transfer, and force-displacement response that often depend critically on both the local and global conformational dynamics of the nucleic acid assembly. However, high molecular weight assemblies exhibit long time-scale and large length-scale motions that cannot easily be sampled using all-atom computational procedures such as molecular dynamics. As an alternative, here we present a computational framework to compute the overdamped conformational dynamics of structured nucleic acid assemblies and apply it to a DNA-based tweezer, a nine-layer DNA origami ring, and a pointer-shaped DNA origami object, which consist of 204, 3,600, and over 7,000 basepairs, respectively. The framework employs a mechanical finite element model for the DNA nanostructure combined with an implicit solvent model to either simulate the Brownian dynamics of the assembly or alternatively compute its Brownian modes. Computational results are compared with an all-atom molecular dynamics simulation of the DNA-based tweezer. Several hundred microseconds of Brownian dynamics are simulated for the nine-layer ring origami object to reveal its long time-scale conformational dynamics, and the first ten Brownian modes of the pointer-shaped structure are predicted. PMID:26636351
Nonlinear dynamics and collective excitations in layered superconducting structures
NASA Astrophysics Data System (ADS)
Zel'Tser, A. S.; Kivshar', Iu. S.; Soboleva, T. K.
1991-06-01
Nonlinear excitations in layered superconducting structures representing a system of interacting extended Josephson junctions are investigated theoretically. The possibility of the propagation of dynamic supersolitons, localized vortex lattice density excitations, in such a system is demonstrated. Particular attention is given to soliton excitations of two types: kinks and envelope solitons. The relaxation of dynamic kinks is investigated numerically.
Dynamic Structure of Emotions Among Individuals with Parkinson's Disease
ERIC Educational Resources Information Center
Chow, Sy-Miin; Nesselroade, John R.; Shifren, Kim; McArdle, John J.
2004-01-01
With few exceptions, the dynamics underlying the mood structures of individuals with Parkinson's Disease have consistently been overlooked. Based on 12 participants' daily self-reports over 72 days, we identified 10 participants whose covariance matrices for positive and negative affect were similar enough to warrant pooling. Dynamic factor models…
Not Available
1991-01-01
The present conference on aplied aerodynamics encompasses computational fluid dynamics, drag prediction/analysis, experimental aerodynamics, high angles of attack, rotor/propeller aerodynamics, super/hypersonic aerodynamics, unsteady aerodynamics, vortex physics, high-speed civil-transport aeroacoustics, and airfoil/wing aerodynamics. Specific issues addressed include high-speed civil-transport air-breathing propulsion, generic hypersonic inlet-module analysis, an investigation on spoiler effects, high-alpha vehicle dynamics, space-station resource node flow-field analysis, a numerical simulation of sabot discard aerodynamics, and vortex control using pneumatic blowing. Also addressed are Navier-Stokes solutions for the F/A-18 Wing-LEX fuselage, tail venting for enhanced yaw damping at spinning conditions, an investigation of rotor wake interactions with a body in low-speed forward flight, and multigrid calculations of 3D viscous cascade flows.
Quantifying and modeling soil structure dynamics
Technology Transfer Automated Retrieval System (TEKTRAN)
Characterization of soil structure has been a topic of scientific discussions ever since soil structure has been recognized as an important factor affecting soil physical, mechanical, chemical, and biological processes. Beyond semi-quantitative soil morphology classes, it is a challenge to describe ...