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Last update: November 12, 2013.
1

Rotary wing aerodynamically generated noise  

Microsoft Academic Search

The history and methodology of aerodynamic noise reduction in rotary wing aircraft are presented. Thickness noise during hover tests and blade vortex interaction noise are determined and predicted through the use of a variety of computer codes. The use of test facilities and scale models for data acquisition are discussed.

F. J. Schmitz; H. A. Morse

1982-01-01

2

Aircraft aerodynamic noise during approach  

NASA Astrophysics Data System (ADS)

The effect of approach velocity, nose and flap inclination, and undercarriage position on aircraft noise was studied. The A 300 B and SN 601 aircraft made two approach passes over a chain of noise recorders. The sound fields and noise spectra show that increasing the speed and flap angle or lowering the undercarriage produces a general increase in noise level such that the directivity of the aerodynamic noise source is hardly changed. All noise spectra increase. Pure frequencies (400 to 500 Hz) accompany flap deployment for the SN 601.

Parant, J. L.

3

Aerodynamic Noise: a Critical Survey  

NASA Astrophysics Data System (ADS)

Annoyance due to railway noise is a particularly sensitive aspect of new high-speed projects. Many studies have shown that aerodynamic noise becomes significant above 300 km/h and can become predominant with the reduction of the contribution of rolling noise. At the moment, no further global reduction of high-speed train noise can be achieved if the aerodynamic noise is not reduced. The objective of this paper is to provide a critical survey of the aeroacoustic noise problem for trains, particularly for high-speed trains. The first step in any acoustic study is to identify the different sources. This paper describes the different aeroacoustic phenomena which are representative of high-speed trains and the technical methodologies used to characterize these phenomena. Specific tools have been developed from on-line tests, wind tunnel experiments, theoretical studies or numerical simulations to characterize the different sources. Using examples, the limitations of the methods and the solutions currently available are reveiwed today. Methods of global modelling of a high-speed train emission are also presented. Finally, future development of new tools based on numerical simulation in aeroacoustics are discussed.

Talotte, C.

2000-03-01

4

Aerodynamic noise prediction using grey model  

Microsoft Academic Search

In this paper, two methods are described to predict the aerodynamic noise induced by flow around a cylinder using the linear model GM (1, 1) and the nonlinear model Verhult based on grey system theory. The grey prediction initial data is from large eddy simulation and acoustic analogy. The prediction results using the model GM(1, 1) are respectively compared to

Long Shuangli; Nie Hong; Li Lei; Xu Xin

2010-01-01

5

On the role of aerodynamically generated sound in determining wayside noise levels from high speed trains  

Microsoft Academic Search

The relative contributions of aerodynamic and wheel\\/rail noise to railway wayside noise levels are not well understood. Methods for predicting these contributions discussed in this paper include (i) an equation for turbulent boundary layer noise (the minimum wayside noise), (ii) an empirical formula for total aerodynamic noise based on airframe noise studies, and (iii) the Peters equation for wheel\\/rail interaction

W. F. King

1977-01-01

6

Aerodynamics and interaction noise of streamlined bodies in nonuniform flows  

NASA Astrophysics Data System (ADS)

The unsteady aerodynamics and interaction noise of streamlined bodies are modeled in terms of the Euler equations linearized about a nonuniform flow. The validity of the inviscid approach is supported by recent LES simulations of an airfoil in a gust indicating that for not-too-small impinging excitations, the interaction process is dominated by inertia forces. Results in the present paper are focused on the aerodynamics and interaction noise of a turbofan modeled as an annular cascade. The model accounts for the inflow-fan-duct coupling and the high frequency of the interaction process. Two high-order numerical algorithms are developed with body-fitted coordinate system. One algorithm uses a primitive variable formulation, the other uses an efficient velocity splitting algorithm and is suitable for broadband computations. Analytical and numerical analysis of disturbances in rotational flows is developed and exact inflow/outflow boundary conditions are derived, yielding directly the radiated acoustics. The upstream disturbances evolve in rotational flows and as a result the aerodynamic-aeroacoustic response of the annular cascade depends on the initial conditions location. Computational results show that the three-dimensional geometry of the annular cascade, the mean flow swirl, and the blade geometry have strong influence on the blade sectional lift and the radiated sound. These results also show the inadequacy of using the popular linear cascade model particularly for realistic fan geometry and inflow conditions.

Atassi, H. M.; Logue, M. M.

2011-08-01

7

An unsteady aerodynamic formulation for efficient rotor tonal noise prediction  

NASA Astrophysics Data System (ADS)

An aerodynamic/aeroacoustic solution methodology for predction of tonal noise emitted by helicopter rotors and propellers is presented. It is particularly suited for configurations dominated by localized, high-frequency inflow velocity fields as those generated by blade-vortex interactions. The unsteady pressure distributions are determined by the sectional, frequency-domain Küssner-Schwarz formulation, with downwash including the wake inflow velocity predicted by a three-dimensional, unsteady, panel-method formulation suited for the analysis of rotors operating in complex aerodynamic environments. The radiated noise is predicted through solution of the Ffowcs Williams-Hawkings equation. The proposed approach yields a computationally efficient solution procedure that may be particularly useful in preliminary design/multidisciplinary optimization applications. It is validated through comparisons with solutions that apply the airloads directly evaluated by the time-marching, panel-method formulation. The results are provided in terms of blade loads, noise signatures and sound pressure level contours. An estimation of the computational efficiency of the proposed solution process is also presented.

Gennaretti, M.; Testa, C.; Bernardini, G.

2013-12-01

8

The prediction of aerodynamic and wheel\\/rail noise generated by high-speed trains  

Microsoft Academic Search

Wheel\\/rail interactions and aerodynamic fluctuations are the important sources of wayside noise produced by high-speed railway trains. The dominance of one or the other of these sources depends entirely on the relative effectivenss of each in generating radiated noise. Equations are given for the calculation of both the wheel\\/rail and aerodynamic noise levels and their predictions are compared to peak

W. F. King III

1977-01-01

9

Numerical simulation for prediction of aerodynamic noise characteristics on a HAWT of NREL phase VI  

Microsoft Academic Search

The purpose of this study is to numerically predict the characteristics of aerodynamic noise generated from rotating wind\\u000a turbine blades according to wind speeds using commercial CFD code, FLUENT. The near-field flow around a HAWT of NREL Phase\\u000a VI is simulated directly by LES, whereas the far-field aerodynamic noise for frequencies below 500 Hz is modeled using FW-H\\u000a analogy. As

Jang-Oh Mo; Young-Ho Lee

2011-01-01

10

Effects of mechanical properties of sealing systems on aerodynamic noise generation inside vehicles  

Microsoft Academic Search

One dominant “wind noise” generating mechanism in road vehicles is the interaction between turbulent flows and flexible structures: specifically door seals and side glass windows. In this study, the effects of seal mechanical properties on interior aerodynamic noise were investigated. ^ The sound transmission characteristics of seals were first investigated. The vibration response together with the radiated sound power was

Junhong Park

2002-01-01

11

Reduction of Aerodynamic Noise Generated by a Bluff-Shaped Pantograph Head Using Synthetic Jet Actuators  

NASA Astrophysics Data System (ADS)

With an increase in the maximum speed of Shinkansen trains, it becomes imperative to resolve aerodynamic and aeroacoustic problems related to pantographs. Hence, some methods based on flow control have been studied to improve the aerodynamic and aeroacoustic characteristics. In this study, the authors attempted to control the flow around a pantograph by using synthetic jets. The results of numerical and experimental tests indicate that the synthetic jets can stabilize the flow around the bluff-shaped pantograph head, thus resulting in a reduction in aerodynamic noise.

Kishige, Hiroaki; Minobe, Takayuki; Ikeda, Mitsuru; Suzuki, Masahiro

12

Aerodynamics.  

National Technical Information Service (NTIS)

A brief review of aerodynamic investigations currently underway at the Institute for Aerospace Studies is provided. An extensive investigation of airship dynamics and turbulence response has resulted in the development of a numerical analysis of airship d...

J. D. Delaurier G. W. Johnston D. W. Zingg W. D. Mckinney C. Hayball

1989-01-01

13

Numerical modeling of wind turbine aerodynamic noise in the time domain.  

PubMed

Aerodynamic noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge noise model is used to determine the unsteady pressure on the blade surface. The far-field noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine noise can be quite different with respect to the distance and direction from the wind turbine. PMID:23363200

Lee, Seunghoon; Lee, Seungmin; Lee, Soogab

2013-02-01

14

Fan Noise Source Diagnostic Test: Rotor Alone Aerodynamic Performance Results.  

National Technical Information Service (NTIS)

The aerodynamic performance of an isolated fan or rotor alone model was measured in the NASA Glenn Research Center 9- by 15- Foot Low Speed Wind Tunnel as part of the Fan Broadband Source Diagnostic Test conducted at NASA Glenn. The Source Diagnostic Test...

C. E. Hughes R. J. Jeracki R. P. Woodward C. J. Miller

2005-01-01

15

Influence of separated vortex on aerodynamic noise of an airfoil blade  

NASA Astrophysics Data System (ADS)

In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade, the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code. In the case of rear surface separation, the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle. The aerodynamic noise level then becomes small according to the vortex scale in the blade chord. When the flow is separated at the leading edge, a separated vortex of low pressure is formed at the vicinity of the trailing edge. The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake. It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.

Sasaki, Soichi; Takamatsu, Hajime; Tsujino, Masao; Tsubota, Haruhiro; Hayashi, Hidechito

2010-02-01

16

An investigation of rotor noise generation by aerodynamic disturbance  

Microsoft Academic Search

An open rotor was considered as a process for converting an unsteady velocity inflow into sound radiation. With the aid of crude assumptions, aero-acoustic transfer functions were defined theoretically for both discrete frequency and broad band noise. A study of the validity of these transfer functions yielded results which show good agreement at discrete frequencies though slightly less good for

C. E. Whitfield

1977-01-01

17

Prediction of aerodynamic noise in a ring fan based on wake characteristics  

NASA Astrophysics Data System (ADS)

A ring fan is a propeller fan that applies an axial-flow impeller with a ring-shaped shroud on the blade tip side. In this study, the entire flow field of the ring fan is simulated using computational fluid dynamics (CFD); the accuracy of the CFD is verified through a comparison with the aerodynamic characteristics of a propeller fan of current model. Moreover, the aerodynamic noise generated by the fan is predicted on the basis of the wake characteristics. The aerodynamic characteristic of the ring fan based on CFD can represent qualitatively the variation in the measured value. The main flow domain of the ring fan is formed at the tip side of the blade because blade tip vortex is not formed at that location. Therefore, the relative velocity of the ring fan is increased by the circumferential velocity. The sound pressure levels of the ring fan within the frequency band of less than 200 Hz are larger than that of the propeller fan. In the analysis of the wake characteristics, it revealed that Karman vortex shedding occurred in the main flow domain in the frequency domain lower than 200 Hz; the aerodynamic noise of the ring fan in the vortex shedding frequency enlarges due to increase in the relative velocity and the velocity fluctuation.

Sasaki, Soichi; Fukuda, Masaharu; Tsujino, Masao; Tsubota, Haruhiro

2011-06-01

18

Analysis of aerodynamic field and noise of a small wind turbine  

NASA Astrophysics Data System (ADS)

The wind energy is deemed as one of the most durable energetic variants of the future because the wind resources are immense. Furthermore, one predicts that the small wind turbine will play a vital role in the urban environment. Unfortunately, nowadays, the noise emissions from wind turbines represent one of the main obstacles to widespread the use in populated zones. Moreover, the energetic efficiency of these wind turbines has to be high even at low and medium wind velocities because, usually the cities are not windy places. The numerical results clearly show that the wakes after the trailing edge are the main noise sources. In order to decrease the power of these noise sources, we should try to decrease the intensity of wakes after the trailing edge, i.e. the aerodynamic fields from pressure and suction sides would have to be almost the same near trailing edge. Furthermore, one observes a strong link between transport (circumferential) velocity and acoustic power level, i.e. if the transport velocity increases, the acoustic power level also augments.

Niculescu, Mihai Leonida; Cojocaru, Marius Gabriel; Pricop, Mihai Victor

2012-11-01

19

Unified aeroacoustics analysis for high speed turboprop aerodynamics and noise. Volume 3: Application of theory for blade loading, wakes, noise, and wing shielding  

Microsoft Academic Search

Results of the program for the generation of a computer prediction code for noise of advanced single rotation, turboprops (prop-fans) such as the SR3 model are presented. The code is based on a linearized theory developed at Hamilton Standard in which aerodynamics and acoustics are treated as a unified process. Both steady and unsteady blade loading are treated. Capabilities include

D. B. Hanson; C. J. McColgan; R. M. Ladden; R. J. Klatte

1991-01-01

20

High speed train noise emission: Latest investigation of the aerodynamic/rolling noise contribution  

NASA Astrophysics Data System (ADS)

The aim of this paper is to discuss the quantification of aeroacoustic and rolling noise sources emitted by high-speed trains externally. This work relies on the comparison of experimental data obtained in the DEUFRAKO Annex K and K2 projects and those produced more recently. These are firstly measurements obtained within the NOEMIE project dedicated to the High Speed Technical Specifications for Interoperability involving the measurement of the acoustic emission of different rolling stock travelling at 250, 300 and 320 km/h (TGV-Duplex, ICE3, Thalys). Additionally, measurements are considered that are obtained in the framework of an SNCF acoustic test campaign performed on a TGV-Duplex at speeds up to 350 km/h. These comprise source localisation using two-dimensional acoustic array measurements and assessment of the wayside noise increase as a function of the speed. The conclusions drawn in the DEUFRAKO K project are compared with the new set of data. A detailed analysis of the results is also provided, supported by complementary measurements (wheel and rail measurements) and simulations (TWINS calculations).

Mellet, C.; Létourneaux, F.; Poisson, F.; Talotte, C.

2006-06-01

21

PREFACE: Aerodynamic sound Aerodynamic sound  

Microsoft Academic Search

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

Sadao Akishita

2010-01-01

22

Unified aeroacoustics analysis for high speed turboprop aerodynamics and noise. Volume 3: Application of theory for blade loading, wakes, noise, and wing shielding  

NASA Astrophysics Data System (ADS)

Results of the program for the generation of a computer prediction code for noise of advanced single rotation, turboprops (prop-fans) such as the SR3 model are presented. The code is based on a linearized theory developed at Hamilton Standard in which aerodynamics and acoustics are treated as a unified process. Both steady and unsteady blade loading are treated. Capabilities include prediction of steady airload distributions and associated aerodynamic performance, unsteady blade pressure response to gust interaction or blade vibration, noise fields associated with thickness and steady and unsteady loading, and wake velocity fields associated with steady loading. The code was developed on the Hamilton Standard IBM computer and has now been installed on the Cray XMP at NASA-Lewis. The work had its genesis in the frequency domain acoustic theory developed at Hamilton Standard in the late 1970s. It was found that the method used for near field noise predictions could be adapted as a lifting surface theory for aerodynamic work via the pressure potential technique that was used for both wings and ducted turbomachinery. In the first realization of the theory for propellers, the blade loading was represented in a quasi-vortex lattice form. This was upgraded to true lifting surface loading. Originally, it was believed that a purely linear approach for both aerodynamics and noise would be adequate. However, two sources of nonlinearity in the steady aerodynamics became apparent and were found to be a significant factor at takeoff conditions. The first is related to the fact that the steady axial induced velocity may be of the same order of magnitude as the flight speed and the second is the formation of leading edge vortices which increases lift and redistribute loading. Discovery and properties of prop-fan leading edge vortices were reported in two papers. The Unified AeroAcoustic Program (UAAP) capabilites are demonstrated and the theory verified by comparison with the predictions with data from tests at NASA-Lewis. Steady aerodyanmic performance, unsteady blade loading, wakes, noise, and wing and boundary layer shielding are examined.

Hanson, D. B.; McColgan, C. J.; Ladden, R. M.; Klatte, R. J.

1991-05-01

23

Aerodynamic Noise Radiated by the Intercoach Spacing and the Bogie of a High-Speed Train  

NASA Astrophysics Data System (ADS)

Full-scale acoustic experiments on a TGV are performed with on-board measurement techniques. Some spectral characteristics of the intercoach spacing and the bogie region are highlighted and interpreted. Two measurement techniques are described; they both extract the acoustical information of a particular aerodynamic source from the signal given by a flow imbedded probe.

Frémion, N.; Vincent, N.; Jacob, M.; Robert, G.; Louisot, A.; Guerrand, S.

2000-03-01

24

Influence of diffuser on aerodynamic noise of a forward curved fan  

NASA Astrophysics Data System (ADS)

In order to clarify the influence of a diffuser on the characteristics of a forward curved fan, the influence of the bare ratio and the outlet angle on the characteristics of the fan were measured through an experiment performed with an actual fan as well as through a numerical simulation, respectively. The mechanism of the discrete frequency noise generated by the separated flow of the diffuser was analyzed. The optimized bare ratio was approximately 17%. The flow separated inside of the diffuser generated discrete frequency noise owing to the interaction between the reversed flow from the diffuser and the impeller rotating at the blade passing frequency. The diffuser outlet angle influenced the pressure ratio more than that by the bare ratio. Furthermore, it was confirmed that restraining the separation in the diffuser effectively decreases the fan noise.

Sasaki, Soichi; Suzuki, Kota; Onomichi, Yuta; Hayashi, Hidechito

2013-10-01

25

PREFACE: Aerodynamic sound Aerodynamic sound  

NASA Astrophysics Data System (ADS)

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 reduction of bluff-body noise. Xiaoyu Wang and Xiaofeng Sun discuss the interaction of fan stator and acoustic treatments using the transfer element method. S Saito and his colleagues in JAXA report the development of active devices for reducing helicopter noise. The paper by A Tamura and M Tsutahara proposes a brand new methodology for aerodynamic sound by applying the lattice Boltzmann finite difference method. As the method solves the fluctuation of air density directly, it has the advantage of not requiring modeling of the sound generation. M A Langthjem and M Nakano solve the hole-tone feedback cycle in jet flow by a numerical method. Y Ogami and S Akishita propose the application of a line-vortex method to the three-dimensional separated flow from a bluff body. I hope that a second issue on aerodynamic sound will be published in FDR in the not too distant future.

Akishita, Sadao

2010-02-01

26

Unified aeroacoustics analysis for high speed turboprop aerodynamics and noise. Volume 5: Propagation of propeller tone noise through a fuselage boundary layer  

NASA Astrophysics Data System (ADS)

An analysis of tone noise propagation through a boundary layer and fuselage scattering effects was derived. This analysis is a three dimensional and the complete wave field is solved by matching analytical expressions for the incident and scattered waves in the outer flow to a numerical solution in the boundary layer flow. The outer wave field is constructed analytically from an incident wave appropriate to the source and a scattered wave in the standard Hankel function form. For the incident wave, an existing function - domain propeller noise radiation theory is used. In the boundary layer region, the wave equation is solved by numerical methods. The theoretical analysis is embodied in a computer program which allows the calculation of correction factors for the fuselage scattering and boundary layer refraction effects. The effects are dependent on boundary layer profile, flight speed, and frequency. Corrections can be derived for any point on the fuselage, including those on the opposite side from the source. The theory was verified using limited cases and by comparing calculations with available measurements from JetStar tests of model prop-fans. For the JetStar model scale, the boundary layer refraction effects produce moderate fuselage pressure reinforcements aft of and near the plane of rotation and significant attenuation forward of the plane of rotation at high flight speeds. At lower flight speeds, the calculated boundary layer effects result in moderate amplification over the fuselage area of interest. Apparent amplification forward of the plane of rotation is a result of effective changes in the source directivity due to boundary layer refraction effects. Full scale effects are calculated to be moderate, providing fuselage pressure amplification of about 5 dB at the peak noise location. Evaluation using available noise measurements was made under high-speed, high-altitude flight conditions. Comparisons of calculations made of free field noise, using a current frequency-domain propeller noise prediction method, and fuselage effects using this new procedure show good agreement with fuselage measurements over a wide range of flight speeds and frequencies. Correction factors for the JetStar measurements made on the fuselage are provided in an Appendix.

Magliozzi, B.; Hanson, D. B.

1991-05-01

27

Hypersonic Aerodynamics.  

National Technical Information Service (NTIS)

The Gas Dynamics Laboratory of the Department of Aerospace and Mechanical Sciences of Princeton University has performed research in experimental and theoretical hypersonic aerodynamics supported by the Air Force Office of Scientific Research. The two are...

S. M. Bogdonoff

1975-01-01

28

Aerodynamic Drag.  

National Technical Information Service (NTIS)

Current research and future prospects in the field of aerodynamic drag were presented and discussed at this Specialists' Meeting. Main emphasis was placed on subjects of practical value to the aerospace industry in relation to its need for accurate predic...

1973-01-01

29

Animation aerodynamics  

Microsoft Academic Search

Methods based on aerodynamics are developed to simulate and control the motion of objects in fluid flows. To simplify the physics for animation, the problem is broken down into two parts: a fluid flow regime and an object boundary regime. With this simplification one can approximate the realistic behaviour of objects moving in liquids or air. It also enables a

Jakub Wejchert; David R. Haumann

1991-01-01

30

Subsonic fan noise  

Microsoft Academic Search

Helicopter rotor noise theories are used to determine the noise of subsonic fans produced solely by the rotor, which results from aerodynamic intake flow distortions. Extensions to the theories allow for both stationary, phase-related distortions and distortions which vary randomly with time and may therefore be considered to rotate with random speeds. It is shown that the aerodynamic interaction of

B. Barry; C. J. Moore

1971-01-01

31

Awesome Aerodynamics!  

NSDL National Science Digital Library

The following resource is from Lessonopoly, which has created student activities and lesson plans to support the video series, Science of the Olympic Winter Games, created by NBC Learn and the National Science Foundation. Featuring exclusive footage from NBC Sports and contributions from Olympic athletes and NSF scientists, the series will help teach your students valuable scientific concepts. In this particular lesson, students will learn about the role of scientific research in the design of competition suits for athletes in the Winter Olympics. Students will also explore and research the concept of aerodynamics, and conduct their own scientific experiment to gain an understanding of this concept.

2010-01-01

32

Missile Aerodynamics: NEAR Conference on Missile Aerodynamics.  

National Technical Information Service (NTIS)

Several aspects of missile aerodynamics were discussed at the conference held in Monterey, California from October 31-November 2, 1988. Missile aerodynamics from an historical perspective, a critical assessment of prediction capabilities, external store s...

M. R. Mendenhall D. Nixon M. F. E. Dillenius

1988-01-01

33

On the prediction of wayside noise levels for high-speed railway vehicles  

Microsoft Academic Search

The relative contributions of aerodynamic and wheel\\/rail noise to railway wayside noise levels are not well understood. Methods for predicting these contributions discussed in this paper include an equation for turbulent boundary layer noise (the minimum wayside noise), an empirical formula for total aerodynamic noise based on airframe noise studies, and the Peters equation for wheel\\/rail interaction noise. Comparisons are

W. F. King III

1976-01-01

34

Noisy Aerodynamic Response And Smooth Approximations In Hsct Design  

Microsoft Academic Search

Convergence difficulties were encountered in our recentefforts toward a combined aerodynamic-structuraloptimization of the High Speed Civil Transport (HSCT). The underlying causes of the convergence problemswere traced to numerical noise in the calculationof aerodynamic drag components for the aircraft. Twotechniques were developed to circumvent the obstaclesto convergence. The first technique employed a sequentialapproximate optimization method which usedlarge initial move limits on...

Anthony A. Giunta; Jane M. Dudley; Robert Narducci; Bernard Grossman; Raphael T. Haftka; William H. Mason; Layne T. Watson

1994-01-01

35

Multicomponent Aerodynamic Magnetoelectric Balance.  

National Technical Information Service (NTIS)

The invention pertains to the field of measurement equipment, in particular, to a multicomponent aerodynamic magnetoelectric balance, which can be used for the measurement of small forces and moments in aerodynamic investigations.

N. P. Levitskii

1973-01-01

36

External aerodynamics of heavy ground vehicles: Computations and wind tunnel testing  

Microsoft Academic Search

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the

Ilhan Bayraktar

2002-01-01

37

Comparison of Measured and Predicted Airfoil Self-Noise with Application to Wind Turbine Noise Reduction.  

National Technical Information Service (NTIS)

In the ongoing JOULE-III project Development of Design Tools for Reduced Aerodynamic Noise Wind Turbines (DRAW), prediction codes for inflowturbulence (IT) noise and turbulent boundary layer trailing-edge (TE) noise, are developed and validated. It is sho...

T. Dassen S. Wagner R. Parchen S. Kang G. Guidati

1997-01-01

38

Aerodynamic noise generated by jet-wing\\/flap interactions of the external USB configuration of STOL aircraft. Part 1: Eight percent scale cold-flow model analysis  

Microsoft Academic Search

The acoustic characteristics of the external upper surface blowing (USB) concept of a powered high lift system (PHLS) were studied experimentally using an 8%-scale static cold flow model. Observations of exhaust jet flow attachment and spreading characteristics on wing\\/flap surface were also carried out using several flow visualization techniques. Noise reduction data were obtained by optimizing basic jet nozzle wing\\/flap

M. Maita; S. Shindo

1981-01-01

39

Noise and noise abatement in fans and blowers: A review  

Microsoft Academic Search

Noise generation and its reduction industrial fans (ventilators) is addressed. A review is given of the fan types commonly in use and their practical applications, the mechanisms of the aerodynamic noise generation in fans, theoretical and empirical prediction methods for fan noise, acoustic similarity laws, and noise reduction methods by means of the fan construction and fan operation. Measurement procedures

W. Neise

1980-01-01

40

Beginner's Guide to Aerodynamics  

NSDL National Science Digital Library

NASA's "Beginner's Guide to Aerodynamics" provides some general information on the basics of aerodynamics. The site allows users to explore at their own pace and level of interest. Some of the topics that are available here are: equations of motion, free falling, air resistance, force, gas properties, and atmosphere. Movies, reading materials, and activities are all available to accommodate a variety of different learning styles. This is an excellent resource, with great reference materials for anyone interested in learning more about aerodynamics.

2007-12-07

41

Assessment and prediction of wind turbine noise.  

National Technical Information Service (NTIS)

The significance of basic aerodynamic noise sources for wind turbine noise are assessed, using information on the aero-acoustic mechanisms of other rotors, which have been studied in depth for many years. From the analysis, areas of potential improvement ...

M. V. Lowson

1993-01-01

42

Airbus Industry and Noise in the Community.  

National Technical Information Service (NTIS)

The contribution to the total perceived noise outside an aircraft during takeoff and landing, attributed to engines and the aerodynamics of the aircraft, is considered. Engine noise reduction by design, location of the engine, and by acoustic analysis of ...

J. Chaussonnet

1982-01-01

43

NASA: Beginner's Guide to Aerodynamics - Aerodynamics Index  

NSDL National Science Digital Library

This web page contains an index of all topics available from NASA's Beginner's Guide to Aerodynamics site. Resources include lesson plans, activities, and interactive simulations for grades 3-12 relating to fundamentals of aerodynamics and the forces acting on airborne objects. The scope of content is extensive and includes specific topics such as thrust, lift, drag, relative velocity, air pressure and density, trajectory, and terminal velocity. Resources are also organized by grade level. These resources, available cost-free, were developed by scientists and teacher workshop participants at NASA's Glenn Learning Research Center.

2008-12-16

44

Directivity of railway noise sources  

NASA Astrophysics Data System (ADS)

In the Harmonoise project the description of vertical and horizontal directivities of railway noise sources has been required. Other features of the source description are sound power level spectra in one-third octave bands as a function of speed and the physical location of the different sound sources. Based on systematic investigations methods to measure and to determine the directivities of railway noise sources are presented in this paper. The determination of the directivity of rolling noise is discussed in detail. For the directivities of traction noise and aerodynamic noise the discussion is more analytical because of limited access to relevant data. For each type of main railway noise source, i.e. rolling noise, traction noise and aerodynamic noise, default directivity functions are proposed for the use in the source description of railway noise. These default directivity functions will be subject to revisions when more accurate data become available.

Zhang, Xuetao; Jonasson, Hans G.

2006-06-01

45

Topic in Depth - Aerodynamics  

NSDL National Science Digital Library

Aerodynamics is the study of what makes things go fast, right? More specifically, itâÂÂs the study of the interaction between bodies and the atmosphere. This topic in depth highlights some fun websites on the science of aerodynamics, for beginners to researchers. If youâÂÂve been watching Wimbeldon lately, you might have been wondering about the aerodynamics of tennis. Or maybe you were riding your bike the other day and wondering how you could pick up a little more speed next time. These sites can help explain.

2010-09-17

46

Aerodynamics of Parachutes.  

National Technical Information Service (NTIS)

This AGARD report discusses the principal aerodynamic characteristics of parachutes and the factors which affect them. It is anticipated that its main readers will be recent engineering graduates entering research establishments, parachute companies or re...

D. J. Cockrell A. D. Young

1987-01-01

47

Aerodynamic Lifting Force.  

ERIC Educational Resources Information Center

|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)|

Weltner, Klaus

1990-01-01

48

Science of Cycling: Aerodynamics  

NSDL National Science Digital Library

This website, from the Exploratorium, reviews the aerodynamics of cycling. Wind resistance is often one of the biggest challenges that professional and amateur cyclists face. This site has a form that lets you "Calculate the Aerodynamic Drag and Propulsive Power of a Bicyclist". Use the form to calculate resistance using different inclines, velocity, weight or wind velocity. At the bottom of the page, you can find useful information and tips on reducing resistance. Check it out before your next bike ride!

2007-12-26

49

Applied computational aerodynamics  

SciTech Connect

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.

Henne, P.A.

1990-01-01

50

Passenger Vehicle Interior Noise Reduction by Laminated Side Glass  

Microsoft Academic Search

The transmission of aerodynamically generated noise, in particularly wind noise, and road noise through vehicle glazing has become of increasing importance and is a major problem in automotive NVH today. Conventional tempered side glass has inherent noise transmission problems and radiates noise more easily at around 1-6 KHz at high vehicle operating speeds for highway driving. Laminated side glass was

Jun Lu

51

Freight Wing Trailer Aerodynamics  

Microsoft Academic Search

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

Sean Graham; Patrick Bigatel

2004-01-01

52

Aerodynamics of stretched flames  

Microsoft Academic Search

This dissertation presents studies of three distinctive problems associated with the aerodynamics of stretched premixed flames. In Part I, the geometry, stability, and stabilization of premixed flames are studied by treating the entire flame as a structure surface, with emphasis on the importance of appropriately accounting for stretch effects on its propagation velocity. The main objective of Part II is

Chung-Jen Sun

1998-01-01

53

Aerodynamics of Race Cars  

NASA Astrophysics Data System (ADS)

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.

Katz, Joseph

2006-01-01

54

Measurements of the Radiated Noise from Sailplanes.  

National Technical Information Service (NTIS)

The noise associated with a flight vehicle is generated by two distinct type sources: (1) the propulsion system and (2) the aerodynamic noise associated with movement of the vehicle through the atmosphere. The minimum noise will be radiated when the propu...

D. L. Smith R. P. Paxson R. D. Talmadge E. R. Hotz

1970-01-01

55

NASA progress in aircraft noise prediction  

Microsoft Academic Search

Langley Research Center efforts to develop a methodology for predicting the effective perceived noise level (EPNL) produced by jet-powered CTOL aircraft to an accuracy of + or - 1.5 dB are summarized with emphasis on the aircraft noise prediction program (ANOPP) which contains a complete set of prediction methods for CTOL aircraft including propulsion system noise sources, aerodynamic or airframe

J. P. Raney; S. L. Padula; W. E. Zorumski

1981-01-01

56

HYSHOT-2 Aerodynamics  

NASA Astrophysics Data System (ADS)

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.

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

2005-02-01

57

Applied computational aerodynamics  

Microsoft Academic Search

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

Henne

1990-01-01

58

Wind turbine noise: Prediction tools and design parameter dependence  

NASA Astrophysics Data System (ADS)

Wind turbine aerodynamic noise sources are described, and noise predictions and measurements are compared. The influence of design parameters and variable running speed on noise emission is discussed. Results show that prediction tools for blade tower passage noise predict noise emission reasonably well. Prediction tools for high frequency noise are not sufficient. Reliable noise measurements for different machines are needed. It is important to take background noise levels into account when noise criteria are decided. Noise emission is highly dependent on rotational speed and running a turbine with variable rpm lowers noise emission for low wind speeds.

Meijer, S.

1984-11-01

59

Comparison of Measured and Predicted Airfoil Self-Noise with Application to Wind Turbine Noise Reduction.  

National Technical Information Service (NTIS)

In the ongoing JOULE-III project Development of Design Tools for Reduced Aerodynamic Noise Wind Turbines (DRAW), prediction codes for inflow-turbulence (IT) noise and turbulent boundary layer trailing-edge (TE) noise, are developed and validated. It is sh...

T. Dassen R. Parchen G. Guidati S. Wagner S. Kang A. E. Khodak

1997-01-01

60

Research at DLR towards airframe noise prediction and reduction  

Microsoft Academic Search

In the final approach phase airframe noise represents the ultimate aircraft noise barrier for future aircraft when equipped with quiet UHBR engines. This paper summarizes the results achieved at DLR in the development of methods and tools for airframe noise prediction and reduction. Numerous DLR internal, national and EC co-financed research projects were conducted to investigate the aerodynamic noise of

Werner Dobrzynski; Roland Ewert; Michael Pott-Pollenske; Michaela Herr; Jan Delfs

2008-01-01

61

Freight Wing Trailer Aerodynamics  

SciTech Connect

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.

Graham, Sean (Primary Investigator); Bigatel, Patrick

2004-10-17

62

Aerodynamics: The Mathematical Implications  

NSDL National Science Digital Library

This unit from the Yale-New Haven Teachers Institute is "an attempt to develop a unit in mathematics that will provide topics for students interested in the aviation trades." The unit can be used to cover all areas of mathematics from areas in geometry sectors to basic addition of fraction and decimal numbers. These general math concepts will be introduced using aerodynamics and aviation language and it is hoped that students will begin "to understand the applicability of some of the mathematics concepts they have learned." This curriculum unit also includes sample lesson plans and references.

Smikle, Hermine E.

2000-03-11

63

Aerodynamic design via control theory  

Microsoft Academic Search

Abstract This paper addresses the question of how to modify in aerodynamic design to improve the performance. Representative examples are given to demonstrate the computational feasibility of using control theory for such a purpose. An introduction and historical survey is included. 1 Introduction and historical survey Computers have had a twofold impact on the science of aerodynamics. On the one

Antony Jameson

1988-01-01

64

Aerodynamics of runback ice accretions  

Microsoft Academic Search

An experimental study of the effects of simulated runback ice accretions has been performed in order to describe their aerodynamic performance penalties and investigate their scaling for use in sub-scale aerodynamic testing. Runback ice accretions corresponding to three flight conditions, warm hold, cold hold and descent, were simulated and tested on the NACA 23012 and NACA 3415. The ice shapes

Edward A. Whalen

2007-01-01

65

On Wings: Aerodynamics of Eagles.  

ERIC Educational Resources Information Center

|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)|

Millson, David

2000-01-01

66

Aerodynamics of a Party Balloon  

ERIC Educational Resources Information Center

|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…

Cross, Rod

2007-01-01

67

Aerodynamics of sports balls  

NASA Astrophysics Data System (ADS)

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.

Mehta, R. D.

68

'Integral Noise': An automatic calculation model for the prediction and control of fixed-wing aircraft noise. I - General considerations, theoretical bases and model analysis  

NASA Astrophysics Data System (ADS)

A description is given of the INTNOI Integral Noise Program for advanced aircraft noise prediction and control. This computer model performs, on a modular basis, the analysis of both boundary layer aerodynamic noise and engine noise for the case of such turbofan-powered commercial aircraft as the 737. It also permits the prediction of noise levels due to engine and aerodynamic sources in the communities affected by approach and landing noise footprints. Attention is given to the effect on engine noise levels of low and high fan bypass ratios, the noise components contributed by nacelles, slats, and flaps at various angles, and the specialized options offered by the modular-structure program.

Bossa, F.; Gualdi, R.

1981-10-01

69

Improvement and verification of low-speed aerodynamic characteristics of a supersonic civil transport aircraft  

Microsoft Academic Search

For supersonic civil transport aircraft, the low-speed aerodynamic characteristics form an important factor in its operational capabilities and in its economic viability. Low drag is a prerequisite to meet the present and future noise and emissions requirements. Innovative concepts for leading-edge devices aiming at the improvement of low-speed aerodynamic efficiency are investigated. From computational analysis of a series of leading-edge

J. van Muijden

2006-01-01

70

Projectiles and aerodynamic forces  

NASA Astrophysics Data System (ADS)

Most elementary works on physics contain something about the motion of projectiles which, it is commonly assumed, are acted on only by gravity. Yet even on balls used in various games the aerodynamic forces are rarely completely negligible (Daish 1972, especially chs 6 and 12). As for bullets and artillery projectiles, the force of air resistance on them is commonly many times that of gravity (Smith 1962). What purpose, then, is supposed to be served by presenting students with such unphysical notions and asking them to spend time working out conundrums about such matters? Warren (1965) has commented on the lack of realism in many parts of school physics, but does not seem to have said much about this example. The author's purpose is to find simple ways of taking into account the air resistance on projectiles, at least approximately.

Armstrong, H. L.

1984-09-01

71

Certain Problems of Experimental Aerodynamics.  

National Technical Information Service (NTIS)

Experimental results of a study of the aerodynamic characteristics at low subsonic velocities of poorly streamlined bodies having different shapes and of the flow past irregularities on the earth's surface are presented. The stress and the forces acting o...

S. M. Gorlin

1975-01-01

72

Differential Evolution in Aerodynamic Optimization  

Microsoft Academic Search

Aerodynamic design algorithms require an optimization strategy to search for the best design. The objectof this paper is to compare the performance of some different strategies when used by an aerodynamicshape optimization routine which designs fan blade shapes. A recently developed genetic algorithm,Differential Evolution [1,2], outperforms more traditional techniques.IntroductionAerodynamic shape optimization involvesdesigning the most efficient shapes of bodies thatmove through...

T. Rogalsky; R. W. Derksen; S. Kocabiyik

1999-01-01

73

Noise and Noise Sickness.  

National Technical Information Service (NTIS)

Basic concepts and questions about noise, which contribute to a proper understanding of the characteristic of industrial noise as well as an experimental acoustical complex for the study of the noise factor, are examined. Special attention has been given ...

Y. T. Andreyevagalanina S. V. Alekeseyev A. V. Kadyskin G. A. Suvopov

1973-01-01

74

Some experimental aircraft engine noise facilities in the United Kingdom  

Microsoft Academic Search

Development of aerodynamic noise theories has demanded greater sophistication of acoustic test facilities and measuring techniques. Experimental work at much reduced scale is usually necessary which entails further complexity. Finally the success of the engine designer must be demonstrated at full scale with accurate flight trials. Problems of acoustic and aerodynamic similarity are encountered at all stages and are discussed.

T. J. Hargest

1972-01-01

75

Aerodynamics of Wiffle Balls  

NASA Astrophysics Data System (ADS)

A team of undergraduate students has performed experiments on Wiffle balls in the Harvey Mudd College wind tunnel facility. Wiffle balls are of particular interest because they can attain a curved trajectory with little or no pitcher-imparted spin. The reasons behind this have not previously been quantified formally. A strain gauge device was designed and constructed to measure the lift and drag forces on the Wiffle ball; a second device to measure lift and drag on a spinning ball was also developed. Experiments were conducted over a range of Reynolds numbers corresponding to speeds of roughly 0-40 mph. Lift forces of up to 0.2 N were measured for a Wiffle ball at 40 mph. This is believed to be due to air flowing into the holes on the Wiffle ball in addition to the effect of the holes on external boundary layer separation. A fog-based flow visualization system was developed in order to provide a deeper qualitative understanding of what occurred in the flowfield surrounding the ball. The data and observations obtained in this study support existing assumptions about Wiffle ball aerodynamics and begin to elucidate the mechanisms involved in Wiffle ball flight.

Utvich, Alexis; Jemmott, Colin; Logan, Sheldon; Rossmann, Jenn

2003-11-01

76

A new approach to complete aircraft landing gear noise prediction  

Microsoft Academic Search

This thesis describes a new landing gear noise prediction system developed at The Pennsylvania State University, called Landing Gear Model and Acoustic Prediction code (LGMAP). LGMAP is used to predict the noise of an isolated or installed landing gear geometry. The predictions include several techniques to approximate the aeroacoustic and aerodynamic interactions of landing gear noise generation. These include (1)

Leonard V. Lopes

2009-01-01

77

Analysis and control of computer cooling fan noise  

Microsoft Academic Search

This thesis is divided into three parts: the study of the source mechanisms and their separation, passive noise control, and active noise control. The mechanisms of noise radiated by a typical computer cooling fan is investigated both theoretically and experimentally focusing on the dominant rotor-stator interaction. The unsteady force generated by the aerodynamic interaction between the rotor blades and struts

Kam Wong

2005-01-01

78

An Approximate Analysis of Wing Unsteady Aerodynamics.  

National Technical Information Service (NTIS)

A brief review of the unsteady aerodynamics in lifting surface theory is reported. For utility in design application, simplified but accurate analytical expressions were developed for generalized unsteady aerodynamics of wings of finite aspect ratio and s...

W. R. Wells

1979-01-01

79

Aerodynamic Simulation of Ice Accretion on Airfoils.  

National Technical Information Service (NTIS)

This report describes recent improvements in aerodynamic scaling and simulation of ice accretion on airfoils. Ice accretions were classified into four types on the basis of aerodynamic effects: roughness, horn, streamwise, and spanwise ridge. The NASA Ici...

A. P. Broeren E. Montreuil G. T. Busch H. E. Addy M. B. Bragg

2011-01-01

80

Unsteady aerodynamics modeling for flight dynamics application  

NASA Astrophysics Data System (ADS)

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.

Wang, Qing; He, Kai-Feng; Qian, Wei-Qi; Zhang, Tian-Jiao; Cheng, Yan-Qing; Wu, Kai-Yuan

2012-02-01

81

Langley Symposium on Aerodynamics, volume 1  

SciTech Connect

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.

Not Available

1986-12-01

82

An investigation of the noise from a scale model of an engine exhaust system  

Microsoft Academic Search

To assist in the identification and understanding of the noise sources that contribute to the exhaust noise of aircraft gas turbine engines, controlled experiments have been carried out to study the noise characteristics of a model turbo-jet exhaust system. The noise data have been related to measurements of the aerodynamic conditions in the model and, with the aid of specific

W. D. Bryce; R. C. K. Stevens

1976-01-01

83

Computational Aerodynamics for Aircraft Design  

Microsoft Academic Search

This article outlines some of the principal issues in the development of numerical methods for the prediction of flows over aircraft and their use in the design process. These include the choice of an appropriate mathematical model, the design of shock-capturing algorithms, the treatment of complex geometric configurations, and shape modifications to optimize the aerodynamic performance.

Antony Jameson

1989-01-01

84

POEMS in Newton's Aerodynamic Frustum  

ERIC Educational Resources Information Center

|The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…

Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita

2010-01-01

85

Rotor/Body Aerodynamic Interactions.  

National Technical Information Service (NTIS)

A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in veloc...

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

1983-01-01

86

Dynamic Soaring: Aerodynamics for Albatrosses  

ERIC Educational Resources Information Center

|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…

Denny, Mark

2009-01-01

87

Aerodynamics of runback ice accretions  

NASA Astrophysics Data System (ADS)

An experimental study of the effects of simulated runback ice accretions has been performed in order to describe their aerodynamic performance penalties and investigate their scaling for use in sub-scale aerodynamic testing. Runback ice accretions corresponding to three flight conditions, warm hold, cold hold and descent, were simulated and tested on the NACA 23012 and NACA 3415. The ice shapes were simulated on two levels of fidelity. Medium-fidelity simulations captured the chordwise location, cross-section, height distribution and chordwise extent of the ice accretion. Low-fidelity simulations captured their height and chordwise location. Two scaling methods were also employed. Each simulation was scaled based upon the ratio of the aerodynamic model chord to the full-scale icing model, called geometric scaling. The warm hold simulations were also scaled based upon the ratio of the local, clean-model boundary-layer thickness on the aerodynamic model to that of the icing model, called boundary-layer scaling. This method was employed because the geometrically-scaled simulations were found to be on the order of the boundary-layer thickness as the model approached stall. Following aerodynamic performance testing, fluorescent-oil flow visualization and hot-wire anemometry were used to investigate the flowfield resulting from the low-fidelity warm hold simulations. Results for this work have shown that runback ice accretions can cause significant aerodynamic performance penalties. In general, the NACA 23012 experienced greater aerodynamic performance penalties due to the runback simulations than did the NACA 3415. Low-fidelity simulations of the cold hold case agreed quite well with their medium fidelity counterparts. In the descent case, the level of variation in ice accretion height was too small for there to be a distinction between the low- and medium-fidelity cases. Low-fidelity simulations of the warm hold accretion did not agree well with the medium-fidelity simulation. In fact, the geometrically-scaled simulation was observed to increase the maximum lift and stalling angle-of-attack of the NACA 3415. Flowfield investigations using fluorescent-oil flow visualization and hot-wire anemometry showed that the simulations that were similar in height to the clean-model local boundary-layer thickness acted to stabilize the recovering boundary layer, delaying stall past the stalling angle-of-attack of the clean case.

Whalen, Edward A.

88

Aerodynamic and Performance Measurements on a SWT-2.3-101 Wind Turbine  

SciTech Connect

This paper provides an overview of a detailed wind turbine field experiment being conducted at NREL under U.S. Department of Energy sponsorship. The purpose of the experiment is to obtain knowledge about the aerodynamics, performance, noise emission and structural characteristics of the Siemens SWT-2.3-101 wind turbine.

Medina, P.; Singh, M.; Johansen, J.; Jove, A.R.; Machefaux, E.; Fingersh, L. J.; Schreck, S.

2011-10-01

89

AERODYNAMIC AND AEROACOUSTIC OPTIMIZATION OF AIRFOI LS VIA A PARALLEL GENETIC ALGORITHM  

Microsoft Academic Search

A parallel genetic algorithm (GA) was used to generate, in a single run, a family of aerodynamically efficient, low-noise rotor blade designs representing th e Pareto optimal set. The n-branch tournament, uniform crossover genetic algorithm operates on twenty design variables, which constitute the control points for a spline representing the airfoil surface. The GA takes advantage of available computer resources

Brian R. Jones; William A. Crossley; Anastasios S. Lyrintzis

1998-01-01

90

The eect of blade aerodynamic modelling on the prediction of high-frequency rotor airloads  

Microsoft Academic Search

Interactions between the blades and vortical structures within the wake of a helicopter rotor are a significant source of impulsive loading and noise, particularly in descending flight. Brown's Vorticity Transport Model has been used to investigate the influence of the fidelity of the local blade aerodynamic model on the accuracy with which the high-frequency airloads associated with blade-vortex interactions can

Mary E. Kelly; Richard E. Brown

2009-01-01

91

Analysis of aerodynamic pendulum oscillations  

NASA Astrophysics Data System (ADS)

Oscillations of an aerodynamic pendulum about the ``along the flow'' equilibrium are studied. The attached oscillator model is used in order to simulate the internal dynamics of the airflow. Stability criteria are found and stability domains in plane of are constructed for different values of parameters. Influence of damping is studied. It is shown that damping depending on airspeed allows describing experimentally registered phenomenon of flutter occurrence in a certain range of airspeeds.

Selyutskiy, Yury D.

2012-11-01

92

Global nonlinear aerodynamic model identification based on NARMAX model  

Microsoft Academic Search

A new method for global nonlinear aerodynamic model identification is presented. Aerodynamic model of aircraft is analyzed, and a simple and effective aerodynamic model is presented. The aerodynamic model of aircraft is then depicted in NARMAX (Nonlinear Auto Regressive Moving Average model with eXogenous inputs) form inside a Linear Regression framework. The items and coefficients of the aerodynamic model are

Hui Xia; Xianyu Meng; Qingwei Chen

2010-01-01

93

Solve valve noise and cavitation problems  

Microsoft Academic Search

A clear understanding of aerodynamic noise theory and cavitation will avoid most major valve problems in process plants and allow the valve engineer to design out potential problems. On the other hand, the plant owner has to recognize that such valves may require a cost premium. However, such a premium will be recovered in a small amount of time because

1997-01-01

94

Aerodynamics of Horizontal Axis Wind Turbines  

Microsoft Academic Search

\\u000a This chapter reviews the aerodynamic characteristics of horizontal axis wind turbines (HAWTs). While the aerodynamics of wind\\u000a turbine are relatively complicated in detail, the fundamental operational principle of a HAWT is that the action of the blowing\\u000a wind produces aerodynamic forces on the turbine blades to rotate them, thereby capturing the kinetic energy contained in the\\u000a wind and converting this

J. Gordon Leishman

95

Aerodynamics of a rolling airframe missile  

Microsoft Academic Search

For guidance-related reasons, there is considerable interest in rolling missiles having single-plane steering capability. To aid the aerodynamic design of these airframes, a unique investigation into the aerodynamics of a rolling, steering missile has been carried out. It represents the first known attempt to measure in a wind tunnel the aerodynamic forces and moments that act on a spinning body-canard-tail

L. E. Tisserand

1981-01-01

96

A Hybrid Aerodynamic and Aeroacoustic Modeling for Small Wind Turbines  

NASA Astrophysics Data System (ADS)

Stall control and pitch control are the most commonly used methods of regulating power. However, through the opportunities presented by the flexible (or teetered) hub of a two-bladed teetered rotor one can also utilize yaw control to regulate power. This is achieved by adjusting the capture area of the rotor disk relative to the prevailing wind direction. This paper presents the aerodynamic and aeroacoustic results obtained from theoretical models for such a rotor when is yawed to the undisturbed flow. The non-axial flow operating conditions results in a variation in the power output and noise spectrum. Some comparisons between calculated and measured noise spectra of a yaw controlled wind turbine show good agreement over all angles up to 60 degrees of yaw.

Stoica, C.; Dumitrescu, H.; Dumitrache, Al.

2010-09-01

97

Brief Introduction to the Soviet Central Research Institute of Aerodynamics.  

National Technical Information Service (NTIS)

The Central Research Institute of Aerodynamics is a composite research institute of aerodynamics having major activities on solving various practical problems of aerodynamics in addition to general research activities. Its main objectives are: (1) Promote...

Y. Yongziao Z. Ruqing

1985-01-01

98

Inner workings of aerodynamic sweep  

SciTech Connect

The recent trend in using aerodynamic sweep to improve the performance of transonic blading has been one of the more significant technological evolutions for compression components in turbomachinery. This paper reports on the experimental and analytical assessment of the pay-off derived from both aft and forward sweep technology with respect to aerodynamic performance and stability. The single-stage experimental investigation includes two aft-swept rotors with varying degree and type of aerodynamic sweep and one swept forward rotor. On a back-to-back test basis, the results are compared with an unswept rotor with excellent performance and adequate stall margin. Although designed to satisfy identical design speed requirements as the unswept rotor, the experimental results reveal significant variations in efficiency and stall margin with the swept rotors. At design speed, all the swept rotors demonstrated a peak stage efficiency level that was equal to that of the unswept rotor. However, the forward-swept rotor achieved the highest rotor-alone peak efficiency. At the same time, the forward-swept rotor demonstrated a significant improvement in stall margin relative to the already satisfactory level achieved by the unswept rotor. Increasing the level of aft sweep adversely affected the stall margin. A three-dimensional viscous flow analysis was used to assist in the interpretation of the data. The reduced shock/boundary layer interaction, resulting from reduced axial flow diffusion and less accumulation of centrifuged blade surface boundary layer at the tip, was identified as the prime contributor to the enhanced performance with forward sweep. The impact of tip clearance on the performance and stability for one of the aft-swept rotors was also assessed.

Wadia, A.R.; Szucs, P.N.; Crall, D.W. [GE Aircraft Engines, Cincinnati, OH (United States)

1998-10-01

99

Measurement methods used to determine background noise and wind turbine noise emission at Carmarthen Bay  

NASA Astrophysics Data System (ADS)

A system to measure background noise around a prototype 250 kW wind turbine was developed. Permanent microphones controlled by a microprocessor (PANDORA system) provide automatic data samples to characterize background noise and noise emissions, which exhibit high variability. The system consists of 4 microphones 50 m from the turbine (2 sonic and 2 infrasonic) and a single microphone (sonic) adjacent to residences 600 m from the turbine. Noise data are obtained at intermediate distances using portable equipment. Results establish the relationship between background noise (wind noise floor) versus wind speed. Noise emission characteristics from mechanical and aerodynamic sources are described in dB(A), 1/3 octave band, and discrete frequency terms. The PANDORA system was employed to determine the variation of background noise levels inside residences with wind speed and direction.

Narine, P. J.

100

Feedback Control of a Morphing Chevron for Takeoff and Cruise Noise Reduction  

Microsoft Academic Search

Noise from commercial high-bypass ratio turbofan engines is generated by turbulent mixing of the hot jet exhaust, fan stream, and ambient air. Serrated aerodynamic devices, known as chevrons, along the trailing edges of a jet engine primary and secondary exhaust nozzle have been shown to reduce jet noise at takeoff and shock-cell noise at cruise conditions. Their optimum shape is

R. H. Cabell; N. Schiller; J. H. Mabe; R. T. Ruggeri; G. W. Butler

101

Aerodynamics of a Cryogenic Semi-Tanker  

Microsoft Academic Search

The design of a modern cryogenic semi-tanker is based primarily upon functionality with little consideration given to aerodynamic drag. As a result, these tankers have maintained the appearance of a wheeled cylinder for several decades. To reduce the fuel usage of these vehicles, this study investigates their aerodynamics. A detailed understanding of the flow field about the vehicle and its

Jason Ortega; Kambiz Salari

2009-01-01

102

Freight Wing Trailer Aerodynamics Final Technical Report  

Microsoft Academic Search

Freight Wing Incorporated utilized the opportunity presented by a DOE category two Inventions and Innovations grant to commercialize and improve upon aerodynamic technology for semi-tuck trailers, capable of decreasing heavy vehicle fuel consumption, related environmental damage, and U.S. consumption of foreign oil. Major project goals included the demonstration of aerodynamic trailer technology in trucking fleet operations, and the development and

Sean Graham

2007-01-01

103

Recent progress in aerodynamic design optimization  

Microsoft Academic Search

Recent emphasis on reduction of design cycle time and cost in the design of commercial aircraft (P.E. Rubbert, CFD and the changing world of airplane design, AIAA Wright Brothers Lecture, September, 1994) has sparked a renewed interest in design optimization in aerodynamics, structures and aeroelastics. In this paper, recent developments in the use of design optimization in aerodynamics using the

R. G. Melvin; W. P. Huffman; D. P. Young; F. T. Johnson; C. L. Hilmes; M. B. Bieterman

1999-01-01

104

Membrane wing aerodynamics for micro air vehicles  

Microsoft Academic Search

The aerodynamic performance of a wing deteriorates considerably as the Reynolds number decreases from 106 to 104. In particular, flow separation can result in substantial change in effective airfoil shape and cause reduced aerodynamic performance. Lately, there has been growing interest in developing suitable techniques for sustained and robust flight of micro air vehicles (MAVs) with a wingspan of 15cm

Yongsheng Lian; Wei Shyy; Dragos Viieru; Baoning Zhang

2003-01-01

105

Aerodynamics and performance testing of the VAWT  

NASA Astrophysics Data System (ADS)

The aerodynamics and testing of vertical axis wind turbines are discussed. Experiments designed to both better understand the aerodynamics of a section operating in an unsteady, curvilinear flowfield and achieve some of the desired changes in section properties are discussed. The common goal of all of these experiments is to increase efficiency an system reliability.

Klimas, P. C.

106

Aerodynamic tests of Darrieus wind turbine blades  

Microsoft Academic Search

An indoor facility for the aerodynamic testing of Darrieus turbine blades was developed. Lift, drag, and moment coefficients were measured for two blades whose angle of attack and chord-to-radius ratio were varied. The first blade used an NACA 0015 airfoil section; the second used a 15% elliptical cross section with a modified circular arc trailing edge. Blade aerodynamic coefficients were

P. G. Migliore; R. E. Walters; W. P. Wolfe

1983-01-01

107

Aerodynamic flow visualization in the ONERA facilities  

Microsoft Academic Search

Shadowgraphy, schlieren and interferometry are used in the ONERA facilities for transonic and supersonic aerodynamic flow visualization. Apparatus equipping several wind tunnels are described and results shown. Studies of aerodynamic flows in turbomachinery compressors require special visualization set-ups: an optical system with cylindrical lenses concentric to the hub carrying the blades has been achieved for a supersonic annular blade cascade,

C. Veret; M. Philbert; J. Surget; G. Fertin

1977-01-01

108

Aerodynamics for the Mars Phoenix Entry Capsule.  

National Technical Information Service (NTIS)

Pre-flight aerodynamics data for the Mars Phoenix entry capsule are presented. The aerodynamic coefficients were generated as a function of total angle-of-attack and either Knudsen number, velocity, or Mach number, depending on the flight regime. The data...

K. T. Edquist M. Schoenenberger P. N. Desai

2008-01-01

109

Aerodynamics and performance testing of the VAWT  

Microsoft Academic Search

The aerodynamics and testing of vertical axis wind turbines are discussed. Experiments designed to both better understand the aerodynamics of a section operating in an unsteady, curvilinear flowfield and achieve some of the desired changes in section properties are discussed. The common goal of all of these experiments is to increase efficiency an system reliability.

P. C. Klimas

1981-01-01

110

Summary Analysis of the Gemini Entry Aerodynamics.  

National Technical Information Service (NTIS)

The aerodynamic data that were derived in 1967 from the analysis of flight-generated data for the Gemini entry module are presented. These data represent the aerodynamic characteristics exhibited by the vehicle during the entry portion of Gemini 2, 3, 5, ...

A. M. Whitnah D. B. Howes

1972-01-01

111

Cricket Ball Aerodynamics: Myth Versus Science.  

National Technical Information Service (NTIS)

Aerodynamics plays a prominent role in the flight of a cricket ball released by a bowler. The main interest is in the fact that the ball can follow a curved flight path that is not always under the control of the bowler. ne basic aerodynamic principles re...

R. D. Mehta

2000-01-01

112

Aerodynamic Simulation of Runback Ice Accretion.  

National Technical Information Service (NTIS)

This report presents the results of recent investigations into the aerodynamics of simulated runback ice accretion on airfoils. Aerodynamic tests were performed on a full-scale model using a high-fidelity, ice-casting simulation at near-flight Reynolds (R...

A. P. Broeren E. A. Whalen G. T. Busch M. B. Bragg

2009-01-01

113

Drag and Noise Measurements on Underwater Vehicles with a Riblet Surface Coating.  

National Technical Information Service (NTIS)

The purpose of this study was to investigate both the drag and noise reducing effects of riblet surface coatings on a marine vehicles. The use of microgrooves, or riblets, for skin friction reduction originated at NASA Langley for aerodynamic applications...

L. W. Reidy M. C. Gillcrist

1989-01-01

114

Noise Reduction in Centrifugal Fans by the Use of Lambda/4 Resonators.  

National Technical Information Service (NTIS)

Aerodynamic blade passage noise reduction, using a resonator at the cutoff of a centrifugal fan, is described. While preserving the original cutoff geometry, the perforated mouth of the resonator forms the new cutoff. The resonator can be tuned to various...

W. Neise G. H. Koopmann

1982-01-01

115

Dynamic stall and aerodynamic damping  

SciTech Connect

A dynamic stall model is used to analyze and reproduce open air blade section measurements as well as wind tunnel measurements. The dynamic stall model takes variations in both angle of attack and flow velocity into account. The paper gives a brief description of the dynamic stall model and presents results from analyses of dynamic stall measurements for a variety of experiments with different airfoils in wind tunnel and on operating rotors. The wind tunnel experiments comprises pitching as well as plunging motion of the airfoils. The dynamic stall model is applied for derivation of aerodynamic damping characteristics for cyclic motion of the airfoils in flapwise and edgewise direction combined with pitching. The investigation reveals that the airfoil dynamic stall characteristics depend on the airfoil shape, and the type of motion (pitch, plunge). The aerodynamic damping characteristics, and thus the sensitivity to stall induced vibrations, depend highly on the relative motion of the airfoil in flapwise and edgewise direction, and on a possibly coupled pitch variation, which is determined by the structural characteristics of the blade.

Rasmussen, F.; Petersen, J.T.; Madsen, H.A.

1999-08-01

116

High-speed propeller noise prediction - A multidisciplinary approach  

Microsoft Academic Search

The prediction of noise produced by advanced propellers is a multidisciplinary subject which involves the aeroelasticity, aerodynamics, and aeroacoustics of rotating blades. As part of the PTA (Propfan Test Assess- ment) noise-prediction project of NASA Langley, state-of-the-art computational methods in these disciplines were combined to form a comprehensive propeller noise-prediction package. The primary function of the project was to assess

Mark H. Dunn; F. Farassat

1992-01-01

117

Survey of techniques for reduction of wind turbine blade trailing edge noise.  

SciTech Connect

Aerodynamic noise from wind turbine rotors leads to constraints in both rotor design and turbine siting. The primary source of aerodynamic noise on wind turbine rotors is the interaction of turbulent boundary layers on the blades with the blade trailing edges. This report surveys concepts that have been proposed for trailing edge noise reduction, with emphasis on concepts that have been tested at either sub-scale or full-scale. These concepts include trailing edge serrations, low-noise airfoil designs, trailing edge brushes, and porous trailing edges. The demonstrated noise reductions of these concepts are cited, along with their impacts on aerodynamic performance. An assessment is made of future research opportunities in trailing edge noise reduction for wind turbine rotors.

Barone, Matthew Franklin

2011-08-01

118

Design and testing of swept and leaned outlet guide vanes to reduce stator-strut-splitter aerodynamic flow interactions  

Microsoft Academic Search

Large circumferentially varying pressure levels produced by aerodynamic flow interactions between downstream stators and struts present a potential noise and stability margin liability in a compression component. These interactions are presently controlled by tailoring the camber and\\/or stagger angles of vanes neighboring the fan frame struts. This paper reports on the design and testing of a unique set of swept

A. R. Wadia; P. N. Szucs; K. L. Gundy-Burlet

1999-01-01

119

On cup anemometer rotor aerodynamics.  

PubMed

The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup. PMID:22778638

Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

2012-05-10

120

On Cup Anemometer Rotor Aerodynamics  

PubMed Central

The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

Pindado, Santiago; Perez, Javier; Avila-Sanchez, Sergio

2012-01-01

121

Unsteady Aerodynamics of Insect Flight  

NASA Astrophysics Data System (ADS)

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

Wang, Z. Jane

2000-03-01

122

The directivity of railway noise at different speeds  

NASA Astrophysics Data System (ADS)

For a sound source, directivity is an important parameter to specify. This parameter also reflects the physical feature of the sound generation mechanism. In this article, studies on the directivity of railway noise, by measurement and by theoretical investigation, are discussed extensively and systematically. The two most important noise types, i.e. rolling noise and aerodynamic noise, are focused on. A model of perpendicular dipole pair is proposed to interpret the measurement specified directivity characters of wheel/rail radiation. This model naturally explains why a vibrating railway wheel does not present dipole directivity character and why rail radiation is of different vertical and horizontal directivity characters. Moreover pantograph noise is also found to be of perpendicular dipole components. As for aerodynamic noise around bogies, scattering of the air flow is proposed to be the mechanism of the noise generation; this understanding leads to a different directivity description for the noise component. Directivities of other important noise types are discussed as well; their directivities become understood, although lacking of relevant directivity data. In summary, this study provides applicable directivity functions together with a survey of the directivities of all important railway noise types and components. Hopefully, this work will be useful, for railway noise engineering also contribute to understand better railway noise.

Zhang, Xuetao

2010-12-01

123

Noise prevention  

NASA Astrophysics Data System (ADS)

Methods for noise abatement are discussed. Noise nuisance, types of noise (continuous, fluctuating, intermittent, pulsed), and types of noise abatement (absorption, vibration damping, isolation) are defined. Rockwool panels, industrial ceiling panels, baffles, acoustic foam panels, vibration dampers, acoustic mats, sandwich panels, isolating cabins and walls, ear protectors, and curtains are presented.

124

Aerodynamics of Power Plant Installation, Part I.  

National Technical Information Service (NTIS)

Contents: Engine designer's point of view; A discussion of selected aerodynamic problems on integration of propulsion systems with airframe on transport aircraft; The feasibility of supersonic combustion ramjets for low hypersonic speeds; The blunt traili...

1965-01-01

125

Aerodynamic Interference Effects on Tilting Proprotor Aircraft.  

National Technical Information Service (NTIS)

The Green's function method was used to study tilting proprotor aircraft aerodynamics with particular application to the problem of the mutual interference of the wing-fuselage-tail-rotor wake configuration. While the formulation is valid for fully unstea...

P. Soohoo L. Morino R. B. Noll N. D. Ham

1977-01-01

126

Aerodynamic Validation of Emerging Projectile Configurations.  

National Technical Information Service (NTIS)

Ever-increasing demands for accuracy and range in modern warfare have expedited the optimization of projectile design. The crux of projectile design lies in the understanding of its aerodynamic properties early in the design phase. This research first inv...

S. W. Lun

2011-01-01

127

Aerodynamic and Gasdynamic Effects in Cosmogony.  

National Technical Information Service (NTIS)

Senior Scientist Stuart J. Weidenschilling presents his final administrative report for the research program entitled 'Aerodynamic and Gasdynamic Effects in Cosmogony' on which he was the Principal Investigator. The research program produced the following...

S. J. Weidenschilling

2005-01-01

128

Projectile Aerodynamic Jump Due to Lateral Impulsives.  

National Technical Information Service (NTIS)

The linear theory for spinning projectiles is extended to account for the application of a simple lateral square impulse activated during free flight. Analytical results are shown to produce simple contributions to the familiar aerodynamic jump formulatio...

G. R. Cooper

2003-01-01

129

Experimental Facilities and Modelling for Rarefied Aerodynamics.  

National Technical Information Service (NTIS)

The present lecture is devoted to experimental and theoretical modelling for rarefied aerodynamics. General features of experimental studies in rarefied flows are discussed. Experimental facilities designed in Saint Petersburg State University for rarefie...

A. Krylov E. Kustova M. Mekhonoshina V. Lashkov

2011-01-01

130

Review of Aerodynamics for Wind Turbines  

NASA Astrophysics Data System (ADS)

This article reviews the state of the art of wind turbine rotor aerodynamics. It addresses present uncertainties in rotor design and load calculations, recent modelling efforts to reduce these uncertainties, and validation activities regarding the modelling and results thereof.

Snel, Herman

2003-07-01

131

Aerodynamics and Performance Testing of the VAWT.  

National Technical Information Service (NTIS)

Early investigations suggest that reductions in cost of energy (COE) and increases in reliability for VAWT systems may be brought about through relatively inexpensive changes to the current aerodynamic design. This design uses blades of symmetrical cross-...

P. C. Klimas

1981-01-01

132

Aerodynamics and performance testing of the VAWT  

NASA Astrophysics Data System (ADS)

Relatively inexpensive changes to the current aerodynamic design which may bring about reductions in cost of energy (COE) and increases in reliability for VAWT systems are discussed. This design uses blades of symmetrical cross section mounted such that the radius from the rotating tower centerline is normal to the blade chord at roughly the 40% chord point. The envisioned changes to this existing design are intended to: (1) lower cut in windspeed; (2) increase maximum efficiency; (3) limit maximum aerodynamic power; and (4) limit peak aerodynamic torques. Experiments to better understand the aerodynamics of a section operating in an unsteady, curvilinear flowfield and achieve some of the desired changes in section properties are described.

Klimas, P. C.

133

Steady Incompressible Variable Thickness Shear Layer Aerodynamics.  

National Technical Information Service (NTIS)

A shear flow aerodynamic theory for steady incompressible flows is presented for both the lifting and non lifting problems. The slow variation of the boundary layer thickness is considered. The slowly varying behavior is treated by using multitime scales....

M. R. Chi

1976-01-01

134

Aerodynamics and performance testing of the VAWT  

SciTech Connect

Early investigations suggest that reductions in cost of energy (COE) and increases in reliability for VAWT systems may be brought about through relatively inexpensive changes to the current aerodynamic design. This design uses blades of symmetrical cross-section mounted such that the radius from the rotating tower centerline is normal to the blade chord at roughly the 40% chord point. The envisioned changes to this existing design are intended to: (1) lower cut-in windspeed; (2) increase maximum efficiency; (3) limit maximum aerodynamic power; and (4) limit peak aerodynamic torques. This paper describes certain experiments designed to both better understand the aerodynamics of a section operating in an unsteady, curvilinear flowfield and achieve some of the desired changes in section properties. The common goal of all of these experiments is to lower VAWT COE and increase system reliability.

Klimas, P.C.

1981-01-01

135

Conformable M3 Microsystems for Aerodynamic Control.  

National Technical Information Service (NTIS)

The recently emerging microelectromechanical technology has created a new frontier for the control of aerodynamic, structural and propulsion systems. The micromachining process provides two unique features for transducer technology: large in quantity and ...

H. Chih-Ming T. Yu-Chong

1998-01-01

136

Unstructured Mesh Algorithms for Aerodynamic Calculations.  

National Technical Information Service (NTIS)

The use of unstructured mesh techniques for solving complex aerodynamic flows is discussed. The principle advantages of unstructured mesh strategies, as they relate to complex geometries, adaptive meshing capabilities, and parallel processing are emphasiz...

D. J. Mavriplis

1992-01-01

137

Aerodynamics of Seeing on Large Transport Aircraft.  

National Technical Information Service (NTIS)

Data were obtained in the full scale flight environment of the Kuiper Airborne Observatory (KAO) on the nature of turbulent shear layer over the open cavity. These data were used to verify proposed aerodynamic scaling relationships to describe the behavio...

W. C. Rose

1986-01-01

138

Torso Experienced Aerodynamic Forces Experienced during Ejection.  

National Technical Information Service (NTIS)

The aerodynamic forces which are experienced by an ejecting aircrewmember are momentarily unique in direction and can be of severe magnitude. One difficulty of analyzing extremity injury during emergency escape is the diversity and intensity of the aerody...

A. J. Nestle

1981-01-01

139

Coupled Aerodynamic-Thermal-Structural (CATS) Analysis.  

National Technical Information Service (NTIS)

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...

1995-01-01

140

Airport noise  

NASA Astrophysics Data System (ADS)

The problem of airport noise at several airports and air bases is detailed. Community reactions to the noise, steps taken to reduce jet engine noise, and the effect of airport use restrictions and curfews on air transportation are discussed. The adverse effect of changes in allowable operational noise on airport safety and altenative means for reducing noise pollution are considered. Community-airport relations and public relations are discussed.

Pendley, R. E.

141

Numerical simulations for transonic aerodynamic flows  

Microsoft Academic Search

Transonic flow is an important aerodynamic phenomenon that occurs in the high subsonic Mach number flight regime. This paper presents the development of a numerical simulation for three-dimensional transonic aerodynamic flows around an isolated wing. The mathematical formulation is based on a transonic small-disturbance equation, which is a nonlinear and mixed elliptic-hyperbolic partial-differential equation. A Newton-like iterative scheme is developed

Yau Shu Wong; Hong Jiang

1991-01-01

142

Recent progress in aerodynamic design optimization  

NASA Astrophysics Data System (ADS)

Recent emphasis on reduction of design cycle time and cost in the design of commercial aircraft (P.E. Rubbert, CFD and the changing world of airplane design, AIAA Wright Brothers Lecture, September, 1994) has sparked a renewed interest in design optimization in aerodynamics, structures and aeroelastics. In this paper, recent developments in the use of design optimization in aerodynamics using the TRANAIR code are considered. Globalization techniques and the extension of the methodology to multipoint design will be discussed. Copyright

Melvin, R. G.; Huffman, W. P.; Young, D. P.; Johnson, F. T.; Hilmes, C. L.; Bieterman, M. B.

1999-05-01

143

Aerodynamics of missiles with slotted fin configurations  

Microsoft Academic Search

Subsonic and transonic aerodynamic data for missiles with solid and slotted wrap around fin configurations are presented. Free-flight aeroballistic tests to obtain this data were conducted at atmospheric pressure over a Mach number range of 0.8 to 1.6. The aerodynamic coefficients and derivatives presented were extracted from the position-attitude-time histories of the experimentally measured trajectories using non-linear numerical integration data

G. L. Abate; G. L. Winchenbach

1991-01-01

144

Darrieus rotor aerodynamics in turbulent wind  

SciTech Connect

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.

Brahimi, M.T.; Paraschivoiu, I. [Ecole Polytechnique de Montreal, Quebec (Canada). Dept. of Mechanical Engineering

1995-05-01

145

Noise modeling, noise experiment, and noise inversion  

NASA Astrophysics Data System (ADS)

Recent developments in inverting ambient noise to obtain bottom reflection properties originated from an understanding of noise behavior and from noise modeling. Sea-surface noise can be modeled equivalently as a ray, wave, or mode phenomenon, but often the ray or flux approach provides the most insight (explaining, e.g., the noise-notch or low-frequency noise enhancement). Theoretically, noise vertical directionality is surprisingly sensitive to the effective depth of the sheet of sound sources, and this is borne out in the spread of behaviors found experimentally. A number of noise inversion approaches have been proposed based on coherence or directionality of sea-surface noise, individual ships or shipping, and airplane doppler. Using a drifting vertical array as a means to measure directionality, one can infer reflection coefficient versus angle and frequency. One can then use this directly for propagation calculation, or alternatively invert to geoacoustic parameters with the help of a fast noise model. A further development is to recover the reflection phase using spectral factorization, then Fourier transform to get the impulse response, which becomes a sub-bottom profile for a drifting array. At 4-kHz design frequency, the layer structure thus determined compares well with a boomer down to 15 m.

Harrison, Chris H.

2005-09-01

146

Helicopter main rotor\\/tail rotor noise radiation characteristics from scaled model rotor experiments in the DNW  

Microsoft Academic Search

A wind tunnel study was performed to investigate the noise characteristics and directivity pattern of a 40 percent scaled helicopter rotor system (BO 105 main\\/tail rotor model). The major objectives of the study were to establish the importance of the tail rotor with respect to the overall noise radiation and to determine the noise reduction potential of aerodynamically improved blade

K.-J. Schultz; W. R. Splettstoesser

1992-01-01

147

Adaptive noise  

PubMed Central

In biology, noise implies error and disorder and is therefore something which organisms may seek to minimize and mitigate against. We argue that such noise can be adaptive. Recent studies have shown that gene expression can be noisy, noise can be genetically controlled, genes and gene networks vary in how noisy they are and noise generates phenotypic differences among genetically identical cells. Such phenotypic differences can have fitness benefits, suggesting that evolution can shape noise and that noise may be adaptive. For example, gene networks can generate bistable states resulting in phenotypic diversity and switching among individual cells of a genotype, which may be a bet hedging strategy. Here, we review the sources of noise in gene expression, the extent to which noise in biological systems may be adaptive and suggest that applying evolutionary rigour to the study of noise is necessary to fully understand organismal phenotypes.

Viney, Mark; Reece, Sarah E.

2013-01-01

148

Aeroacoustic characteristics and noise reduction of a centrifugal fan for a vacuum cleaner  

Microsoft Academic Search

The aeroacoustic characteristics of a centrifugal fan for a vacuum cleaner and its noise reduction method are studied in this\\u000a paper. The major noise source of a vacuum cleaner is the centrifugal fan. The impeller of the fan rotates at over 3000 rpm,\\u000a and generates very high-level noise. It was revealed that the dominant noise source is the aerodynamic interaction

Wan-Ho Jeon; Ho Seon Rew; Chang-Joon Kim

2004-01-01

149

Flow Noise  

NASA Astrophysics Data System (ADS)

In this chapter, sound sources are discussed where sound is generated by aerodynamic or hydrodynamic flow or where flow is at least an essential influencing quantity. To start with, sound generation originating from flow should be explained considering some typical examples.

Fritz, K. R.; Hantschk, C.-C.; Heim, S.; Nürnberger, H.; Schorer, E.; Stüber, B.; Vortmeyer, D.

150

The Aerodynamics of Bird Flight  

NASA Astrophysics Data System (ADS)

The manifest success of birds in flight over small and large distances, in confined quarters and also in gusty conditions has inspired admiration, investigation and sometimes imitation from the earthbound human. Birds occupy a range of scales (2 g - 12 kg in mass, and 0.05 - 3 m in wingspan) that overlaps certain micro air vehicle (MAV) designs and there is interest in whether some bird-like properties (flapping wings, deformable feathers, movable tails) might be useful or even necessary for successful MAVs. A bird with 5 cm mean chord flying at 8 m/s has a nominal Reynolds number of 2 - 3 x 10^4. This is an extremely inconvenient range for design, operation and analysis of lifting surfaces, even in steady motion, because their properties are very sensitive to boundary layer separation. The moderate- to high-amplitude flapping motions, together with the complex surface geometry and mechanical properties of the wings themselves lead to yet further challenges. This talk will review some of the theoretical and practical approaches towards understanding and analyzing the aerodynamics of various types of bird flight, including some recent research results that suggest that this effort is far from complete.

Spedding, Geoffrey

2002-11-01

151

Advanced theoretical treatment of propeller noise  

NASA Astrophysics Data System (ADS)

Current formulations used for the prediction of the noise of propellers are derived by a unified approach. The approach is based on various forms of the solution of Ffowcs Williams-Hawkings equation. The Ffowcs Williams-Hawkings equation is derived and the method of solving the equation in various forms using the Green's function approach is discussed. To understand the procedure in deriving these results, relevant facts of the generalized function theory are discussed. The power of this theory is demonstrated by several examples. The theoretical formulas by various researchers for propeller noise prediction and a new result by the author are derived and discussed. The emphasis is on time domain methods. The relation of the acoustic theory to linear aerodynamic lifting surface theories is discussed. It is shown that treating linear aerodynamic theory from the point of view of acoustics can lead to new and useful results.

Farassat, F.

152

External aerodynamics of heavy ground vehicles: Computations and wind tunnel testing  

NASA Astrophysics Data System (ADS)

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. This can be achieved by optimization of external body geometry and flow modification devices. Considering the latter, a thorough understanding of the airflow is a prerequisite. The present study aims to simulate the external flow field around a ground vehicle using a computational method. The model and the method are selected to be three dimensional and time-dependent. The Reynolds-averaged Navier Stokes equations are solved using a finite volume method. The Renormalization Group (RNG) k-epsilon model was elected for closure of the turbulent quantities. Initially, the aerodynamics of a generic bluff body is studied computationally and experimentally to demonstrate a number of relevant issues including the validation of the computational method. Experimental study was conducted at the Langley Full Scale Wind Tunnel using pressure probes and force measurement equipment. Experiments and computations are conducted on several geometric configurations. Results are compared in an attempt to validate the computational model for ground vehicle aerodynamics. Then, the external aerodynamics of a heavy truck is simulated using the validated computational fluid dynamics method, and the external flow is presented using computer visualization. Finally, to help the estimation of the error due to two commonly practiced engineering simplifications, a parametric study on the tires and the moving ground effect are conducted on full-scale tractor-trailer configuration. Force and pressure coefficients and velocity distribution around tractor-trailer assembly are computed for each case and the results compared with each other. Finally, this study demonstrates that it is possible to apply computational fluid dynamics for ground vehicle aerodynamics with substantial detail and fidelity. With the latest developments on computing power, computational fluid dynamics can be applied on real-life transportation problems with reasonable turn-around times, reliability, ease of accessibility and affordability. The next step is deemed to be considering such a computational methodology for analysis within an automated optimization process in improving aerodynamic designs of heavy ground vehicles.

Bayraktar, Ilhan

153

Community noise  

NASA Astrophysics Data System (ADS)

Airport and community land use planning as they relate to airport noise reduction are discussed. Legislation, community relations, and the physiological effect of airport noise are considered. Noise at the Logan, Los Angeles, and Minneapolis/St. Paul airports is discussed.

Bragdon, C. R.

154

Identification, modelling and reduction potential of railway noise sources: a critical survey  

NASA Astrophysics Data System (ADS)

Environmental requirements for railway operations will become tighter in the future. In particular, annoyance due to railway noise has to be taken carefully into account in the expansion of freight traffic as well as in new high speed line projects. Reduction of noise at source can be more attractive than the use of noise barriers but this requires a thorough understanding of the source mechanisms. This paper presents a critical survey of the identification and modelling of railway noise sources and summarizes the current knowledge of the physical source phenomena (mainly rolling and aerodynamic sources) as well as the potential for noise reduction. Future research perspectives are also given. These concern, in particular, improvements to source modelling, especially for aerodynamic noise, investigation of other sources and development of more advanced models for predicting railway noise in the environment. These should include a better description of the sources, obtained from modelling.

Talotte, C.; Gautier, P.-E.; Thompson, D. J.; Hanson, C.

2003-10-01

155

Blade-vortex interaction noise reduction with active twist smart rotor technology  

Microsoft Academic Search

The results of this analytical feasibility study suggest that active blade twist technology is a viable means to reduce blade-vortex interaction (BVI) noise in rotorcraft systems. A linearized unsteady aerodynamics analysis was formulated and successfully validated with computation fluid dynamics (CFD) analysis. A simple control scheme with three control points was found to be effective for active BVI noise reduction.

Peter C. Chen; James D. Baeder; Robert A. D. Evans; John Niemczuk

2001-01-01

156

Noise of the 10-bladed 60 deg swept SR5 propeller in a wind tunnel  

Microsoft Academic Search

Noise generated by supersonic helical tip speed propellers is a possible cabin environment problem for future airplanes powered by these propellers. Noise characteristics of one of these propellers, designated SR-5, are presented. A matrix of tests was conducted to provide as much acoustic information as possible. During aerodynamic testing it was discovered that the propeller had an aeroelastic instability which

J. H. Dittmar; G. L. Stefko; R. J. Jeracki

1983-01-01

157

Noise Characteristics of Jet Flap Type Exhaust Flows.  

National Technical Information Service (NTIS)

An experimental investigation of the aerodynamic noise and flow field characteristics of internal-flow jet-augmented flap configurations (abbreviated by the term jet flap throughout the study) is presented. The first part is a parametric study of the infl...

G. O. Schrecker J. R. Maus

1974-01-01

158

Noise Reduction in Centrifugal Fans by Use of Resonators.  

National Technical Information Service (NTIS)

The significant reduction of aerodynamically generated blade passage noise at the source by mounting a lambda/4 resonator at the cut-off lip on centrifugal fans is considered. While preserving the original cut-off lip geometry, the perforated mouth of the...

W. Neise G. H. Koopmann

1981-01-01

159

Noise emission of propfans due to the inflow distortions  

Microsoft Academic Search

The noise emission of counter rotating propellers (CRP) was investigated theoretically and by experiments giving special emphasis to the influence of CRP inflow distortions and to the aerodynamics interaction between the rotors. Experiments were conducted using a 0.6 m scale model CRP with 5 blades on the front rotor and 6 blades on the rear rotor in an open-jet wind

Th. Loelgen; G. Neuwerth

1992-01-01

160

Application of high resolution airload calculations to helicopter noise prediction  

Microsoft Academic Search

Recent studies of blade\\/vortex interactions have resulted in the development of aerodynamic models with which the very detailed loading data necessary for noise predictions can be calculated. The methods employed not only obviate the need for some of the simplifying assumptions that have previously reduced the precision and sensitivity of acoustic calculations but also achieve this improvement at little cost

A. C. Pike

1987-01-01

161

Turbine disk cavity aerodynamics and heat transfer  

NASA Astrophysics Data System (ADS)

Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.

Johnson, B. V.; Daniels, W. A.

1992-07-01

162

Aerodynamic Flow Control using Distributed Active Bleed  

NASA Astrophysics Data System (ADS)

The aerodynamic effects of large-area air bleed that is driven through surface openings by pressure differences across a lifting airfoil and regulated by addressable, arrays of integrated louvers have been investigated in wind tunnel experiments. Time-dependent interactions between the bleed and cross flows alter the apparent aerodynamic shape of the lifting surface and consequently the distributions of aerodynamic forces and moments. The lift and pitching moment can be significantly altered over a wide range of angles of attack from pre- to post-stall by independently-controlled bleed near the leading (LE) and trailing (TE) edges. While TE bleed effects nearly-linear variation of the pitching moment with minimal changes in lift, LE bleed leads to large variations in lift and pitching moment with minimal drag penalty. Phase-locked PIV shows the effects of the bleed on the flow on the suction surface and in the near wake. Supported by AFOSR

Kearney, John M.; Glezer, Ari

2010-11-01

163

Wind turbine aerodynamics research needs assessment  

NASA Astrophysics Data System (ADS)

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.

Stoddard, F. S.; Porter, B. K.

1986-01-01

164

Aerodynamic tests of Darrieus wind turbine blades  

SciTech Connect

An indoor facility for the aerodynamic testing of Darrieus turbine blades was developed. Lift, drag, and moment coefficients were measured for two blades whose angle of attack and chord-to-radius ratio were varied. The first blade used an NACA 0015 airfoil section; the second used a 15% elliptical cross section with a modified circular arc trailing edge. Blade aerodynamic coefficients were corrected to section coefficients for comparison to published rectilinear flow data. Although the airfoil sections were symmetrical, moment coefficients were not zero and the lift and drag curves were asymmetrical about zero lift coefficient and angle of attack. These features verified the predicted virtual camber and incidence phenomena. Boundary-layer centrifugal effects were manifested by discontinuous lift curves and large differences in the angle of zero lift between th NACA 0015 and elliptical airfoils. It was concluded that rectilinear flow aerodynamic data are not applicable to Darrieus turbine blades, even for small chord-to-radius ratios.

Migliore, P.G.; Walters, R.E.; Wolfe, W.P.

1983-03-01

165

Aerodynamic collection efficiency of fog water collectors  

NASA Astrophysics Data System (ADS)

Fog water collectors (FWC) can provide water to arid zones with persistent advection and orographic fog. A key feature of any FWC is the mesh used to capture fog droplets. Two relevant mesh characteristics are its shade coefficient and the characteristics of the fibers used to weave or knit the mesh. This paper develops a simple superposition model to analyze the effect of these factors on the Aerodynamic Collection Efficiency (ACE) of FWCs. Due to the simplicity of the model it cannot be directly applied to actual FWC meshes, and serve only for guidance on the order of magnitude of the optimum shade coefficient and the corresponding ACE. The model shows that there is a maximum ACE of the order of 20-24.5% for shade coefficients between 0.5 and 0.6, for the particular mesh simulated. Aerodynamic collection efficiency can be increased by making the FWC concave and improving the aerodynamics of the mesh fibers.

Rivera, Juan De Dios

2011-11-01

166

14 CFR 23.371 - Gyroscopic and aerodynamic loads.  

Code of Federal Regulations, 2013 CFR

...Gyroscopic and aerodynamic loads. (a) Each engine mount and its supporting structure must be designed for the gyroscopic, inertial, and aerodynamic loads that result, with the engine(s) and propeller(s), if applicable, at maximum continuous...

2013-01-01

167

Analysis of Prop-Fan/Airframe Aerodynamic Integration.  

National Technical Information Service (NTIS)

An approach to aerodynamic integration of turboprops and airframes, with emphasis placed upon wing mounted installations is addressed. Potential flow analytical techniques were employed to study aerodynamic integration of the prop fan propulsion concept w...

M. L. Boctor C. W. Clay C. F. Watson

1978-01-01

168

Mathematical Modeling of the Aerodynamic Characteristics in Flight Dynamics.  

National Technical Information Service (NTIS)

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 der...

G. T. Chapman L. B. Schiff M. Tobak

1984-01-01

169

Static Aerodynamics of the Mars Exploration Rover Entry Capsule.  

National Technical Information Service (NTIS)

The static aerodynamics for the Mars Exploration Rover (MER) aeroshell are presented. This aerodynamic database was an integral part of the end-to-end simulation used in preentry analysis for determining the MER entry design requirements for development o...

M. Schoeneberger F. McNEil Cheatwood P. N. Desai

2005-01-01

170

Unsteady Low Reynolds Number Aerodynamics for Micro Air Vehicles (MAVs).  

National Technical Information Service (NTIS)

This work introduces the Micro Air Vehicle (MAV) problem from the viewpoint of aerodynamics. Water tunnels are assessed as tools for MAV aerodynamics. The design, construction and instrumentation of RB's 'Horizontal Free-surface Water Tunnel' is documente...

M. V. Ol

2010-01-01

171

Control of maglev vehicles with aerodynamic and guideway disturbances  

NASA Astrophysics Data System (ADS)

A modeling, analysis, and control design methodology is presented for maglev vehicle ride quality performance improvement as measured by the Pepler Index. Ride quality enhancement is considered through active control of secondary suspension elements and active aerodynamic surfaces mounted on the train. To analyze and quantify the benefits of active control, the authors have developed a five degree-of-freedom lumped parameter model suitable for describing a large class of maglev vehicles, including both channel and box-beam guideway configurations. Elements of this modeling capability have been recently employed in studies sponsored by the U.S. Department of Transportation (DOT). A perturbation analysis about an operating point, defined by vehicle and average crosswind velocities, yields a suitable linearized state space model for multivariable control system analysis and synthesis. Neglecting passenger compartment noise, the ride quality as quantified by the Pepler Index is readily computed from the system states. A statistical analysis is performed by modeling the crosswind disturbances and guideway variations as filtered white noise, whereby the Pepler Index is established in closed form through the solution to a matrix Lyapunov equation. Data is presented which indicates the anticipated ride quality achieved through various closed-loop control arrangements.

Flueckiger, Karl; Mark, Steve; Caswell, Ruth; McCallum, Duncan

1994-05-01

172

Numerical simulations for transonic aerodynamic flows  

NASA Astrophysics Data System (ADS)

Transonic flow is an important aerodynamic phenomenon that occurs in the high subsonic Mach number flight regime. This paper presents the development of a numerical simulation for three-dimensional transonic aerodynamic flows around an isolated wing. The mathematical formulation is based on a transonic small-disturbance equation, which is a nonlinear and mixed elliptic-hyperbolic partial-differential equation. A Newton-like iterative scheme is developed for solving the transonic equation, and it is used in conjunction with a preconditioned minimal-residual algorithm. The numerical technique is proven to be efficient and reliable. Computational results for transonic flows around the ONERA M6 wing are presented.

Wong, Yau Shu; Jiang, Hong

1991-04-01

173

Identification of Aerodynamic Coefficients of Ground Vehicles Using Neural Network  

Microsoft Academic Search

The purpose of this paper is to demonstrate the application of a combination of neural network and an oscillating model facility as an approach in identification of aerodynamic coefficients of ground vehicle. In literature study, a method for estimating transient aerodynamic data has been introduced and the aerodynamic coefficients are extracted from the measured time response by means of conventional

Nabilah Ramli; Shuhaimi Mansor; Hishamuddin Jamaluddin; Waleed Fekry Faris

2007-01-01

174

Aerodynamics of flapping wings with fluttering trailing edges  

Microsoft Academic Search

Our previous work on the aerodynamics of passive flexible flapping wings showed that there is a strong relationship between the dynamics of trailing edge and the size of the leading edge vortex, therefore aerodynamic forces. Here we investigated the aerodynamic effects of active trailing edges. The experiments were conducted on a model flapping wing in an oil tank. During static

Liang Zhao; Zheng Hu; Jesse Roll; Xinyan Deng

2010-01-01

175

A Study of Aerodynamics of Low Reynolds Number Flexible Airfoils  

Microsoft Academic Search

The interaction between aerodynamics and structural flexibility in a low Reynolds number environment is of considerable interest to biological and micro air vehicles. In this study, coupled fluid-structure computations of the Navier-Stokes fluid flow and a flexible airfoil in low Reynolds number environments are conducted to probe the aerodynamic implications. While a flexible airfoil deforms in response to the aerodynamic

Jian Tang; Dragos Viieru; Wei Shyy

176

Pressure-sensitive paint in aerodynamic testing  

Microsoft Academic Search

Pressure-sensitive paint (PSP) is a relatively new aerodynamic measurement tool with the unique capability of providing a field measurement of pressure over a test surface. An introductory review of this technology is presented, which is confined to the application of the PSP method to aircraft development wind tunnel testing. This is at present the primary application area and thus the

B. G. McLachlan; J. H. Bell

1995-01-01

177

The bulk aerodynamic formulation over heterogeneous surfaces  

Microsoft Academic Search

This interpretative literature survey examines problems with application of the bulk aerodynamic method to spatially averaged fluxes over heterogeneous surfaces. This task is approached by tying together concepts from a diverse range of recent studies on subgrid parameterization, the roughness sublayer, the roll of large “inactive” boundary-layer eddies, internal boundary-layer growth, the equilibrium sublayer, footprint theory and the blending height.

L. Mahrt

1996-01-01

178

Aerodynamics of high-speed railway train  

Microsoft Academic Search

Railway train aerodynamic problems are closely associated with the flows occurring around train. Much effort to speed up the train system has to date been paid on the improvement of electric motor power rather than understanding the flow around the train. This has led to larger energy losses and performance deterioration of the train system, since the flows around train

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

2002-01-01

179

Aerodynamic drag in cycling: methods of assessment.  

PubMed

When cycling on level ground at a speed greater than 14 m/s, aerodynamic drag is the most important resistive force. About 90% of the total mechanical power output is necessary to overcome it. Aerodynamic drag is mainly affected by the effective frontal area which is the product of the projected frontal area and the coefficient of drag. The effective frontal area represents the position of the cyclist on the bicycle and the aerodynamics of the cyclist-bicycle system in this position. In order to optimise performance, estimation of these parameters is necessary. The aim of this study is to describe and comment on the methods used during the last 30 years for the evaluation of the effective frontal area and the projected frontal area in cycling, in both laboratory and actual conditions. Most of the field methods are not expensive and can be realised with few materials, providing valid results in comparison with the reference method in aerodynamics, the wind tunnel. Finally, knowledge of these parameters can be useful in practice or to create theoretical models of cycling performance. PMID:21936289

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

2011-09-01

180

Macro aerodynamic devices controlled by micro systems  

Microsoft Academic Search

Micro-ElectroMechanical-Systems (MEMS) have emerged as a major enabling technology across the engineering disciplines. In this study, the possibility of applying MEMS to the aerodynamic field was explored. We have demonstrated that microtransducers can be used to control the motion of a delta wing in a wind tunnel and can even maneuver a scaled aircraft in flight tests. The main advantage

Gwo-Bin Lee; F. K. Jiang; T. Tsao; Y. C. Tai; C. M. Ho

1997-01-01

181

COMPUTER ANALYSIS OF INDUSTRIAL BATCH DRYER AERODYNAMICS  

Microsoft Academic Search

One of the fundamental problems encountered in the batch dryer design field is the determination of appropriate equipment configuration that would ensure uniform distribution of air over the dryer trays. Such industrial batch dryer aerodynamics problems can be successfully investigated using computational fluid dynamics techniques. A mathematical model for predicting the two-dimensional air flow inside a typical industrial batch dryer

C. T. Kiranoudis; N. C. Markatos

1998-01-01

182

Hybrid methods for inverse aerodynamic design  

Microsoft Academic Search

This thesis describes a novel hybrid approach for the multipoint inverse design of airfoils for complex aerodynamic systems. In this approach, an inverse design method for single-element airfoils is coupled with an analysis module for the complex system. The airfoils that comprise the complex system are generated in isolation using the single-element airfoil inverse design method. The analysis module is

Ashok Gopalarathnam

1999-01-01

183

Minimum Energy Guidance for Aerodynamically Controlled Missiles  

Microsoft Academic Search

This paper examines the problem of guiding a missile to a target using minimal energy. First, an optimal controller is de- velopedforamissilethathasarbitrarycontrol overits acceleration vector. Next, an optimal controller is sought for a missile that has a directional control constraint, which is intended to model the ac- tual constraint present in aerodynamically controlled missiles. The optimal guidance law is shown

Robert Wes Morgan; Hal Tharp; Thomas L. Vincent

2011-01-01

184

Aerodynamics of Transport Aircraft Spoiler Solutions  

Microsoft Academic Search

based on wing mean aerodynamic chord. Spoiler or air brake, respectively, deflection angles are varied. Most relevant parameters, regarding steep approach performance, are minimum approach velocity, descent velocity and approach velocity. The corresponding values are theoretically derived. Therewith, the relative performance of the different spoilers is shown. Regarding effectiveness per deflection angle, a vertically deployed air brake with no breather

U. JUNG; C. BREITSAMTER

185

Containerless processing of ceramics by aerodynamic levitation  

Microsoft Academic Search

An inexpensive containerless processing technique based on aerodynamic levitation has been developed for high temperature studies on ceramics. A spherical sample of about 0.5 cm diameter levitates in an upward stream of inert gas in a flared graphite nozzle which also acts as a susceptor and heats the sample by radiation to a maximum temperature of 2200°C. The highest heating

A. S. Gandhi; A. Saravanan; V. Jayaram

1996-01-01

186

Noise Protection  

NASA Astrophysics Data System (ADS)

Environmental Health Systems puts forth an increasing effort in the U.S. to develop ways of controlling noise, particularly in industrial environments due to Federal and State laws, labor union insistence and new findings relative to noise pollution impact on human health. NASA's Apollo guidance control system aided in the development of a noise protection product, SMART. The basis of all SMART products is SMART compound a liquid plastic mixture with exceptional energy/sound absorbing qualities. The basic compound was later refined for noise protection use.

1980-01-01

187

Acoustic and Aerodynamic Performance of a 1.83-Meter (6-Ft) Diameter 1.25-Pressure-Ratio Fan (Qf-8).  

National Technical Information Service (NTIS)

A 1.25-pressure-ratio 1.83-meter (6-ft) tip diameter experimental fan stage with characteristics suitable for engine application on STOL aircraft was tested for acoustic and aerodynamic performance. The design incorporated proven features for low noise, i...

R. P. Woodward J. G. Lucas

1976-01-01

188

Aircraft Noise  

NASA Astrophysics Data System (ADS)

Aircraft industry is exposed to increasing public pressure aiming at a continuing reduction of aircraft noise levels. This is necessary to both compensate for the detrimental effect on noise of the expected increase in air traffic and improve the quality of living in residential areas around airports.

Michel, Ulf; Dobrzynski, Werner; Splettstoesser, Wolf; Delfs, Jan; Isermann, Ullrich; Obermeier, Frank

189

Noise jammer discrimination by noise modulation bandwidth  

NASA Astrophysics Data System (ADS)

A method is described for distinguishing between multiple noise jammer sources having different noise modulation bandwidths. Noise signals are detected by a receiver having a bandwidth substantially the same as the bandwidth of the jammer noise source. The dwell time of the noise pulses formed by the receiver provides a means for determining the noise modulation bandwidth of a noise jammer source.

Wise, C. D.

1984-06-01

190

Aeroacoustics of modern transonic fans — Fan noise reduction from its sources  

Microsoft Academic Search

The noise of aerodynamics nature from modern transonic fan is examined from its sources with the perspective of noise reduction\\u000a through aero-acoustics design using advanced Computational Fluid Dynamics (CFD) tools. In particular the problems associated\\u000a with the forward propagating noise in the front is addressed. It is identified that the shock wave spillage from the leading\\u000a edge near the fan

L. Xu; J. D. Denton

2003-01-01

191

Freight Wing Trailer Aerodynamics Final Technical Report  

SciTech Connect

Freight Wing Incorporated utilized the opportunity presented by a DOE category two Inventions and Innovations grant to commercialize and improve upon aerodynamic technology for semi-tuck trailers, capable of decreasing heavy vehicle fuel consumption, related environmental damage, and U.S. consumption of foreign oil. Major project goals included the demonstration of aerodynamic trailer technology in trucking fleet operations, and the development and testing of second generation products. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck’s fuel consumption. However, significant design challenges have prevented past concepts from meeting industry needs. Freight Wing utilized a 2003 category one Inventions and Innovations grant to develop practical solutions to trailer aerodynamics. Fairings developed for the front, rear, and bottom of standard semi-trailers together demonstrated a 7% improvement to fuel economy in scientific tests conducted by the Transportation Research Center (TRC). Operational tests with major trucking fleets proved the functionality of the products, which were subsequently brought to market. This category two grant enabled Freight Wing to further develop, test and commercialize its products, resulting in greatly increased understanding and acceptance of aerodynamic trailer technology. Commercialization was stimulated by offering trucking fleets 50% cost sharing on trial implementations of Freight Wing products for testing and evaluation purposes. Over 230 fairings were implemented through the program with 35 trucking fleets including industry leaders such as Wal-Mart, Frito Lay and Whole Foods. The feedback from these testing partnerships was quite positive with product performance exceeding fleet expectations in many cases. Fleet feedback also was also valuable from a product development standpoint and assisted the design of several second generation products intended to further improve efficiency, lower costs, and enhance durability. Resulting products demonstrated a 30% efficiency improvement in full scale wind tunnel tests. The fuel savings of our most promising product, the “Belly Fairing” increased from 4% to 6% in scientific track and operational tests. The project successfully demonstrated the economic feasibility of trailer aerodynamics and positioned the technology to realize significant public benefits. Scientific testing conducted with partners such as the EPA Smartway program and Transport Canada clearly validated the fuel and emission saving potential of the technology. The Smartway program now recommends trailer aerodynamics as a certified fuel saving technology and is offering incentives such as low interest loans. Trailer aerodynamics can save average trucks over 1,100 gallons of fuel an 13 tons of emissions every 100,000 miles, a distance many trucks travel annually. These fuel savings produce a product return on investment period of one to two years in average fleet operations. The economic feasibility of the products was validated by participating fleets, several of which have since completed large implementations or demonstrated an interest in volume orders. The commercialization potential of the technology was also demonstrated, resulting in a national distribution and manufacturing partnership with a major industry supplier, Carrier Transicold. Consequently, Freight Wing is well positioned to continue marketing trailer aerodynamics to the trucking industry. The participation of leading fleets in this project served to break down the market skepticism that represents a primary barrier to widespread industry utilization. The benefits of widespread utilization of the technology could be quite significant for both the transportation industry and the public. Trailer aerodynamics could potentially save the U.S. trucking fleet over a billion gallons of fuel and 20 million tons of emissions annually.

Sean Graham

2007-10-31

192

Numerical and experimental investigation on aerodynamic performance of small axial flow fan with hollow blade root  

NASA Astrophysics Data System (ADS)

To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blade root is manufactured near the hub. The numerical and experimental results show that hollow blade root has some effect on the static performance. Static pressure of the modified fan is generally the same with that of the datum fan, while, the efficiency curve of the modified fan has a different trend with that of the datum fan. The highest efficiency of the modified fan is 10% greater than that of the datum fan. The orthogonal experimental results of fan noise show that hollow blade root is a feasible method of reducing fan noise, and the maximum value of noise reduction is about 2 dB. The factors affecting the noise reduction of hollow blade root are in the order of importance as follows: hollow blade margin, hollow blade height and hollow blade width. The much smoother pressure distribution of the modified fan than that of the datum fan is the main mechanism of noise reduction of hollow blade root. The research results will provide the proof of the parameter optimization and the structure design for high performance and low noise small axial fans.

Li, Zhang; Jin, Yingzi; Huashu, Dou; Yuzhen, Jin

2013-10-01

193

Performance of an aerodynamic particle separator  

SciTech Connect

This compact, high-flow device aerodynamically separates small particles from a gas stream by a series of annular truncated airfoils. The operating concept, design and performance of this novel particle separator are described. Tests results using corn starch and post-cyclone coal fly ash are presented. Particle collection efficiencies of 90% for corn starch and 70% for coal fly ash were measured at inlet velocities of 80 ft s{sup {minus}1} (2,700 cfm) and (6 inches) water pressure drop with particle loading up to 4 gr ft{sup {minus}3} in air at standard conditions. Results from computer modeling using FLUENT are presented and compared to the tests. The aerodynamic particle separator is an attractive alternative to a cyclone collector.

Ragland, K.; Han, J.; Aerts, D. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Mechanical Engineering

1996-12-31

194

Aerodynamics of missiles with slotted fin configurations  

SciTech Connect

Subsonic and transonic aerodynamic data for missiles with solid and slotted wrap around fin configurations are presented. Free-flight aeroballistic tests to obtain this data were conducted at atmospheric pressure over a Mach number range of 0.8 to 1.6. The aerodynamic coefficients and derivatives presented were extracted from the position-attitude-time histories of the experimentally measured trajectories using non-linear numerical integration data reduction routines. Results of this testing and analysis show the static and dynamic stability variations for solid and slotted wrap around fin configurations. The presence of a side moment dependent on pitch angle, inherent to wrap around fin configurations, is measured for both configurations. Results indicate a reduction in the magnitude of this side-moment for missiles with slotted fins. Also, roll dependence with Mach number effects are not present with the slotted fin configurations. Designers should consider these factors whenever wrap around fins are utilized. 14 refs.

Abate, G.L.; Winchenbach, G.L. (USAF, Armament Laboratory, Eglin AFB, FL (USA))

1991-01-01

195

Aerodynamic interference between two Darrieus wind turbines  

SciTech Connect

The effect of aerodynamic interference on the performance of two curved bladed Darrieus-type vertical axis wind turbines has been calculated using a vortex/lifting line aerodynamic model. The turbines have a tower-to-tower separation distance of 1.5 turbine diameters, with the line of turbine centers varying with respect to the ambient wind direction. The effects of freestream turbulence were neglected. For the cases examined, the calculations showed that the downwind turbine power decrement (1) was significant only when the line of turbine centers was coincident with the ambient wind direction, (2) increased with increasing tipspeed ratio, and (3) is due more to induced flow angularities downstream than to speed deficits near the downstream turbine.

Schatzle, P.R.; Klimas, P.C.; Spahr, H.R.

1981-04-01

196

Aerodynamic design of winged space vehicle  

Microsoft Academic Search

The aerodynamic and flight dynamic characteristics of a winged space vehicle, the Highly Maneuverable Experimental Space vehicle, have been evaluated by numerical calculations and wind tunnel tests. Special attention is given to the high angle-of-attack flight capability in high-speed flight conditions, along with the capability to achieve a safe horizontal landing on a conventional runway. The longitudinal and lateral\\/directional trim

Yoshifumi Inatani; Koichi Yonemoto

1988-01-01

197

Variable-Fidelity Aerodynamic Shape Optimization  

Microsoft Academic Search

\\u000a Aerodynamic shape optimization (ASO) plays an important role in the design of aircraft, turbomachinery and other fluid machinery.\\u000a Simulation-driven ASO involves the coupling of computational fluid dynamics (CFD) solvers with numerical optimization methods.\\u000a Although being relatively mature and widely used, ASO is still being improved and numerous challenges remain. This chapter\\u000a provides an overview of simulation-driven ASO methods, with an

Leifur Leifsson; Slawomir Koziel

198

Unsteady aerodynamics of fluttering and tumbling plates  

Microsoft Academic Search

We investigate the aerodynamics of freely falling plates in a quasi-two-dimensional flow at Reynolds number of 103, which is typical for a leaf or business card falling in air. We quantify the trajectories experimentally using high-speed digital video at sufficient resolution to determine the instantaneous plate accelerations and thus to deduce the instantaneous fluid forces. We compare the measurements with

U. P ESAVENTO; Z. J ANE W ANG

2005-01-01

199

Aerodynamic characteristics of flapping motion in hover  

Microsoft Academic Search

The aim of the present work is to understand the aerodynamic phenomena and the vortex topology of an unsteady flapping motion\\u000a by means of numerical and experimental methods. Instead of the use of real insect\\/bird wing geometries and kinematics which\\u000a are highly complex and difficult to imitate by an exact modeling, a simplified model is used in order to understand

D. Funda Kurtulus; Laurent David; Alain Farcy; Nafiz Alemdaroglu

2008-01-01

200

Hybrid methods for inverse aerodynamic design  

NASA Astrophysics Data System (ADS)

This thesis describes a novel hybrid approach for the multipoint inverse design of airfoils for complex aerodynamic systems. In this approach, an inverse design method for single-element airfoils is coupled with an analysis module for the complex system. The airfoils that comprise the complex system are generated in isolation using the single-element airfoil inverse design method. The analysis module is then used to obtain the aerodynamic characteristics of the resulting complex system. Using a multidimensional Newton iteration, the design variables associated with the generation of the airfoils in isolation are adjusted to achieve desired aerodynamic characteristics on the complex system. As the thesis demonstrates, changes in velocity distributions for an airfoil in isolation are very similar to the changes for the same airfoil as a part of a more complex system. This similarity enables (1) the use of the isolated airfoil velocity distributions as design variables to achieve the desired aerodynamics on the complex system and (2) the computation of sensitivities for the Newton iteration during the design of the airfoils in isolation rather than through repeated function evaluations of the analysis module. These features result in a unified hybrid approach that not only is rapid and interactive, but also enables easy integration of different analysis modules in the design method. In this thesis, the hybrid approach has been applied to the development of inverse methods for the design of (1) multi-element airfoils for multipoint velocity and boundary-layer prescriptions and (2) airfoils to obtain desired multipoint velocity distributions on three-dimensional wings and complex juncture regions. These methods are discussed in detail. Several examples are presented to demonstrate the methods. Finally, the potential of the hybrid design approach for application to the design of other systems such as airfoils with plain flaps and airfoils for wing-fuselage junctures is presented.

Gopalarathnam, Ashok

201

CFD calculations of S809 aerodynamic characteristics  

Microsoft Academic Search

Steady-state, two-dimensional CFD calculations were made for the S809 laminar-flow, wind-turbine airfoil using the commercial code CFD-ACE. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data from the Delft University 1.8 m x 1.25 m low-turbulence wind tunnel. This work highlights two areas in CFD that require further investigation and development in order to enable

Walter P. Wolfe; Stuart S. Ochs

1997-01-01

202

DOE Project on Heavy Vehicle Aerodynamic Drag  

Microsoft Academic Search

Class 8 tractor-trailers consume 11-12% of the total US petroleum use. At highway speeds, 65% of the energy expenditure for a Class 8 truck is in overcoming aerodynamic drag. The project objective is to improve fuel economy of Class 8 tractor-trailers by providing guidance on methods of reducing drag by at least 25%. A 25% reduction in drag would present

R McCallen; K Salari; J Ortega; P Castellucci; D Pointer; F Browand; J Ross; B Storms

2007-01-01

203

Noise Jammer Discrimination by Noise Spectral Bandwidth.  

National Technical Information Service (NTIS)

A method for distinguishing between multiple noise jammer sources having different noise spectral bandwidths. Noise signals are detected over a relatively narrow detection bandwidth. The percent of time that the jammer spectral noise is within the fixed d...

C. D. Wise

1984-01-01

204

The Aerodynamics of a Flying Sports Disc  

NASA Astrophysics Data System (ADS)

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

Potts, Jonathan R.; Crowther, William J.

2001-11-01

205

Computational Aerodynamics of Insects' Flapping Flight  

NASA Astrophysics Data System (ADS)

The kinematics of the Insects' flapping flight is modeled through mathematical and computational observations with commercial software. Recently, study on the insects' flapping flight became one of the challenging research subjects in the field of aeronautics because of its potential applicability to intelligent micro-robots capable of autonomous flight and the next generation aerial-vehicles. In order to uncover its curious unsteady characteristics, many researchers have conducted experimental and computational studies on the unsteady aerodynamics of insects' flapping flight. In the present paper, the unsteady flow physics around insect wings is carried out by utilizing computer software e-AIRS. The e-AIRS (e-Science Aerospace Integrated Research System) analyzes and models the results of computational and experimental aerodynamics, along with integrated research process of these two research activities. Stroke angles and phase angles, the important two factors in producing lift of the airfoils are set as main parameters to determine aerodynamic characteristics of the insects' flapping flight. As a result, the optimal phase angle to minimize the drag and to maximize the lift are found. Various simulations indicate that using proper value of variables produce greater thrust due to an optimal angle of attack at the initial position during down stroke motion.

Yang, Kyung Dong; Kyung, Richard

2011-11-01

206

A Preliminary Axial Fan Design Method with the Considerat ion of Performance and Noise Characteristics  

NASA Astrophysics Data System (ADS)

Presented in this paper are a fan's aero-acoustic performance method and its computation procedure which combines aerodynamic flow field data, performances and noise levels of fan. The internal flow field and the performance of fan are analyzed by the through-flow modeling, inviscid pitch-averaged quasi-3D flow analysis combined with flow deviation and pressure loss distribution models. Based on the predicted internal flow field dada by the trough-flow modeling, fan noise is predicted by two models for the discrete frequency noise due to rotating steady aerodynamic thrust and blade interaction and for the broadband noise due to turbulent boundary layer and wake vortex shedding. The present predictions of the flow distribution, the performance and the noise level of fan are well agreed with actual test results.

Lee, Chan; Kil, Hyun Gwon

2010-06-01

207

Study of aerodynamic methods for improving truck fuel economy  

Microsoft Academic Search

Results are reported of a 3-year program to investigate aerodynamic means to reduce fuel consumption of tractor-trailer trucks. The study considered the benefit of aerodynamic add-on devices to reduce the aerodynamic drag on existing vehicles, and the influence of design alternatives in reducing the drag of future vehicles. Results are obtained for scaled-models in water table and wind-tunnel experiments, and

F. T. Jr. Buckley; C. H. Marks; W. H. Jr. Walston

1978-01-01

208

A study of aerodynamic methods for improving truck fuel economy  

Microsoft Academic Search

Results of a 3-year program to investigate aerodynamic means to reduce fuel consumption of tractor-trailer trucks are reported. The study considers the benefit of aerodynamic add-on devices to reduce the aerodynamic drag on existing vehicles, and the influence of design alternatives in reducing the drag of future vehicles. Results are obtained for scaled-models in water table and wind-tunnel experiments, and

F. T. Jr. Buckley; C. H. Marks; W. H. Walston Jr

1978-01-01

209

Inverse aerodynamic design applications using the MGM hybrid formulation  

Microsoft Academic Search

The well-known modified Garabedian–Mcfadden (MGM) method is an attractive alternative for aerodynamic inverse design, for its simplicity and effectiveness (P. Garabedian and G. Mcfadden, Design of supercritical swept wings, AIAA J. 20(3) (1982), 289–291; J.B. Malone, J. Vadyak, and L.N. Sankar, Inverse aerodynamic design method for aircraft components, J. Aircraft 24(2) (1987), 8–9; Santos, A hybrid optimization method for aerodynamic

Ernani V. Volpe; Guilherme L. Oliveira; Luis C. C. Santos; Marcelo T. Hayashi; Marco A. B. Ceze

2009-01-01

210

State of the art in wind turbine aerodynamics and aeroelasticity  

NASA Astrophysics Data System (ADS)

A comprehensive review of wind turbine aeroelasticity is given. The aerodynamic part starts with the simple aerodynamic Blade Element Momentum Method and ends with giving a review of the work done applying CFD on wind turbine rotors. In between is explained some methods of intermediate complexity such as vortex and panel methods. Also the different approaches to structural modelling of wind turbines are addressed. Finally, the coupling between the aerodynamic and structural modelling is shown in terms of possible instabilities and some examples.

Hansen, M. O. L.; Sørensen, J. N.; Voutsinas, S.; Sørensen, N.; Madsen, H. Aa.

2006-06-01

211

Airframe Noise Prediction Method.  

National Technical Information Service (NTIS)

A noise component method is presented for calculating airframe noise. Noise from clean wing and tail surface is represented as trailing edge noise caused by the turbulent boundary layer. Landing gear noise is given by an empirical representation of model ...

M. R. Fink

1977-01-01

212

Acoustic and aerodynamic study of a pusher-propeller aircraft model  

NASA Astrophysics Data System (ADS)

An aerodynamic and acoustic study was made of a pusher-propeller aircraft model in the NASA-Ames 7 x 10 ft Wind Tunnel. The test section was changed to operate as an open jet. The 591 mm diameter unswept propeller was operated alone and in the wake of three empennages: an I tail, Y tail, and a V tail. The radiated noise and detailed wake properties were measured. Results indicate that the unsteady blade loading caused by the blade interactions with the wake mean velocity distribution had a strong effect on the harmonics of blade passage noise. The blade passage harmonics above the first were substantially increased in all horizontal directions by the empennage/propeller interaction. Directivity in the plane of the propeller was maximum perpendicular to the blade surface. Increasing the tail loading caused the propeller harmonics to increase 3 to 5 dB for an empennage/propeller spacing of 0.38 mean empennage chords. The interaction noise became weak as empennage propeller spacing was increased beyond 1.0 mean empennage chord lengths. Unlike the mean wake deficit, the wake turbulence had only a small effect on the propeller noise, that effect being a small increase in the broadband noise.

Soderman, Paul T.; Horne, W. Clifton

1990-09-01

213

Reference values and improvement of aerodynamic drag in professional cyclists.  

PubMed

The aims of this study were to measure the aerodynamic drag in professional cyclists, to obtain aerodynamic drag reference values in static and effort positions, to improve the cyclists' aerodynamic drag by modifying their position and cycle equipment, and to evaluate the advantages and disadvantages of these modifications. The study was performed in a wind tunnel with five professional cyclists. Four positions were assessed with a time-trial bike and one position with a standard racing bike. In all positions, aerodynamic drag and kinematic variables were recorded. The drag area for the time-trial bike was 31% higher in the effort than static position, and lower than for the standard racing bike. Changes in the cyclists' position decreased the aerodynamic drag by 14%. The aero-helmet was not favourable for all cyclists. The reliability of aerodynamic drag measures in the wind tunnel was high (r > 0.96, coefficient of variation < 2%). In conclusion, we measured and improved the aerodynamic drag in professional cyclists. Our results were better than those of other researchers who did not assess aerodynamic drag during effort at race pace and who employed different wheels. The efficiency of the aero-helmet, and the validity, reliability, and sensitivity of the wind tunnel and aerodynamic field testing were addressed. PMID:17943597

García-López, Juan; Rodríguez-Marroyo, José Antonio; Juneau, Carl-Etienne; Peleteiro, José; Martínez, Alfredo Córdova; Villa, José Gerardo

2008-02-01

214

A climatology of formation conditions for aerodynamic contrails  

NASA Astrophysics Data System (ADS)

Aerodynamic contrails are defined in this paper as line shaped ice clouds caused by aerodynamically triggered cooling over the wings of an aircraft in cruise which become visible immediately at the trailing edge of the wing or close to it. Effects at low altitudes like condensation to liquid droplets and their potential heterogeneous freezing are excluded from our definition. We study atmospheric conditions that allow formation of aerodynamic contrails. These conditions are stated and then applied to atmospheric data, first to a special case where an aerodynamic contrail was actually observed and then to a full year of global reanalysis data. We show where, when (seasonal variation), and how frequently (probability) aerodynamic contrails can form, and how this relates to actual patterns of air traffic. We study the formation of persistent aerodynamic contrails as well. Finally we check whether aerodynamic and exhaust contrails can coexist in the atmosphere. We show that visible aerodynamic contrails are possible only in an altitude range between roughly 540 and 250 hPa, and that the ambient temperature is the most important parameter, not the relative humidity. Finally we give an argument for our believe that currently aerodynamic contrails have a much smaller climate effect than exhaust contrails, which may however change in future with more air traffic in the tropics.

Gierens, K.; Dilger, F.

2013-06-01

215

Aerodynamic, aeroacoustic, and aeroelastic investigations of airfoil-vortex interaction using large-eddy simulation  

NASA Astrophysics Data System (ADS)

In helicopters, vortices (generated at the tip of the rotor blades) interact with the next advancing blades during certain flight and manoeuvring conditions, generating undesirable levels of acoustic noise and vibration. These Blade-Vortex Interactions (BVIs), which may cause the most disturbing acoustic noise, normally occur in descent or high-speed forward flight. Acoustic noise characterization (and potential reduction) is one the areas generating intensive research interest to the rotorcraft industry. Since experimental investigations of BVI are extremely costly, some insights into the BVI or AVI (2-D Airfoil-Vortex Interaction) can be gained using Computational Fluid Dynamics (CFD) numerical simulations. Numerical simulation of BVI or AVI has been of interest to CFD for many years. There are still difficulties concerning an accurate numerical prediction of BVI. One of the main issues is the inherent dissipation of CFD turbulence models, which severely affects the preservation of the vortex characteristics. Moreover this is not an issue only for aerodynamic and aeroacoustic analysis but also for aeroelastic investigations as well, especially when the strong (two-way) aeroelastic coupling is of interest. The present investigation concentrates mainly on AVI simulations. The simulations are performed for Mach number, Ma = 0.3, resulting in a Reynolds number, Re = 1.3 x 106, which is based on the chord, c, of the airfoil (NACA0012). Extensive literature search has indicated that the present work represents the first comprehensive investigation of AVI using the LES numerical approach, in the rotorcraft research community. The major factor affecting the aerodynamic coefficients and aeroacoustic field as a result of airfoil-vortex interaction is observed to be the unsteady pressure generated at the location of the interaction. The present numerical results show that the aerodynamic coefficients (lift, moment, and drag) and aeroacoustic field are strongly dependent on the airfoil-vortex vertical miss-distance, airfoil angle of attack, vortex characteristics, and aeroelastic response of airfoil to airfoil-vortex interaction. A decay of airfoil-vortex interactions with the increase of vertical miss-distance and angle of attack was observed. Also, a decay of airfoil-vortex interactions is observed for the case of a flexible structure when compared with the case of a rigid structure. The decay of vortex core size produces a decrease in the aerodynamic coefficients.

Ilie, Marcel

216

Environmental Noise  

Microsoft Academic Search

\\u000a Environmental noise may be defined as unwanted sound that is caused by emissions from traffic (roads, air traffic corridors,\\u000a and railways), industrial sites and recreational infrastructures, which may cause both annoyance and damage to health. Noise\\u000a in the environment or community seriously affects people, interfering with daily activities at school, work and home and during\\u000a leisure time.\\u000a \\u000a \\u000a As an introduction

Martin Rumberg

2009-01-01

217

Predicting tonal noise from a high rotational speed centrifugal fan  

NASA Astrophysics Data System (ADS)

Prediction of noise generated by centrifugal fans is much more complex than prediction noise generated by axial fans. A complete, aerodynamic and aeroacoustic, investigation of the tonal noise of a high rotational speed centrifugal fan is proposed in this paper. The studied fan is made up of an impeller, a diffuser and a return channel. The purpose of this work is to understand the nature of noise generated within this type of machine. An aeroacoustic model based on the Ffowcs Williams and Hawkings equation is used to predict dipole and monopole tonal noises in the frequency domain. Showing the importance of the monopole source in this kind of fans constitutes the main contribution in these research tasks. A numerical simulation of the fluid flow validated by experiments, enables to obtain the fluctuating forces and normal velocity on the impeller and diffuser blades needed for the aeroacoustic computation.

Khelladi, S.; Kouidri, S.; Bakir, F.; Rey, R.

2008-06-01

218

Aerodynamic yawing moment characteristics of bird wings.  

PubMed

The aerodynamic yawing moments due to sideslip are considered for wings of birds. Reference is made to the experience with aircraft wings in order to identify features which are significant for the yawing moment characteristics. Thus, it can be shown that wing sweep, aspect ratio and lift coefficient have a great impact. Focus of the paper is on wing sweep which can considerably increase the yawing moment due to sideslip when compared with unswept wings. There are many birds the wings of which employ sweep. To show the effect of sweep for birds, the aerodynamic characteristics of a gull wing which is considered as a representative example are treated in detail. For this purpose, a sophisticated aerodynamic method is used to compute results of high precision. The yawing moments of the gull wing with respect to the sideslip angle and the lift coefficient are determined. They show a significant level of yaw stability which strongly increases with the lift coefficient. It is particularly high in the lift coefficient region of best gliding flight conditions. In order to make the effect of sweep more perspicuous, a modification of the gull wing employing no sweep is considered for comparison. It turns out that the unswept wing yields yawing moments which are substantially smaller than those of the original gull wing with sweep. Another feature significant for the yawing moment characteristics concerns the fact that sweep is at the outer part of bird wings. By considering the underlying physical mechanism, it is shown that this feature is most important for the efficiency of wing sweep. To sum up, wing sweep provides a primary contribution to the yawing moments. It may be concluded that this is an essential reason why there is sweep in bird wings. PMID:15808868

Sachs, Gottfried

2005-06-21

219

Aerodynamic and functional consequences of wing compliance  

NASA Astrophysics Data System (ADS)

A growing body of evidence indicates that a majority of insects experience some degree of wing deformation during flight. With no musculature distal to the wing base, the instantaneous shape of an insect wing is dictated by the interaction of aerodynamic forces with the inertial and elastic forces that arise from periodic accelerations of the wing. Passive wing deformation is an unavoidable feature of flapping flight for many insects due to the inertial loads that accompany rapid stroke reversals—loads that well exceed the mean aerodynamic force. Although wing compliance has been implicated in a few lift-enhancing mechanisms (e.g., favorable camber), the direct aerodynamic consequences of wing deformation remain generally unresolved. In this paper, we present new experimental data on how wing compliance may affect the overall induced flow in the hawkmoth, Manduca sexta. Real moth wings were subjected to robotic actuation in their dominant plane of rotation at a natural wing beat frequency of 25 Hz. We used digital particle image velocimetry at exceptionally high temporal resolution (2,100 fps) to assess the influence of wing compliance on the mean advective flows, relying on a natural variation in wing stiffness to alter the amount of emergent deformation (freshly extracted wings are flexible and exhibit greater compliance than those that are desiccated). We find that flexible wings yield mean advective flows with substantially greater magnitudes and orientations more beneficial to lift than those of stiff wings. Our results confirm that wing compliance plays a critical role in the production of flight forces.

Mountcastle, Andrew M.; Daniel, Thomas L.

2009-05-01

220

Aerodynamic and functional consequences of wing compliance  

NASA Astrophysics Data System (ADS)

A growing body of evidence indicates that a majority of insects experience some degree of wing deformation during flight. With no musculature distal to the wing base, the instantaneous shape of an insect wing is dictated by the interaction of aerodynamic forces with the inertial and elastic forces that arise from periodic accelerations of the wing. Passive wing deformation is an unavoidable feature of flapping flight for many insects due to the inertial loads that accompany rapid stroke reversals—loads that well exceed the mean aerodynamic force. Although wing compliance has been implicated in a few lift-enhancing mechanisms (e.g., favorable camber), the direct aerodynamic consequences of wing deformation remain generally unresolved. In this paper, we present new experimental data on how wing compliance may affect the overall induced flow in the hawkmoth, Manduca sexta. Real moth wings were subjected to robotic actuation in their dominant plane of rotation at a natural wing beat frequency of 25 Hz. We used digital particle image velocimetry at exceptionally high temporal resolution (2,100 fps) to assess the influence of wing compliance on the mean advective flows, relying on a natural variation in wing stiffness to alter the amount of emergent deformation (freshly extracted wings are flexible and exhibit greater compliance than those that are desiccated). We find that flexible wings yield mean advective flows with substantially greater magnitudes and orientations more beneficial to lift than those of stiff wings. Our results confirm that wing compliance plays a critical role in the production of flight forces.

Mountcastle, Andrew M.; Daniel, Thomas L.

221

Fluidization technologies: Aerodynamic principles and process engineering.  

PubMed

The concept of fluidization has been adapted to different unit processes of pharmaceutical product development. Till date a lot of improvements have been made in the engineering design to achieve superior process performance. This review is focused on the fundamental principles of aerodynamics and hydrodynamics associated with the fluidization technologies. Fluid-bed coating, fluidized bed granulation, rotor processing, hot melt granulation, electrostatic coating, supercritical fluid based fluidized bed technology are highlighted. Developments in the design of processing equipments have been explicitly elucidated. This article also discusses processing problems from the operator's perspective along with latest developments in the application of these principles. PMID:19340888

Dixit, Rahul; Puthli, Shivanand

2009-11-01

222

Measurement technology for micro-scale aerodynamics  

NASA Astrophysics Data System (ADS)

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

Martin, Michael James

223

Aerodynamics of High-Speed Trains  

NASA Astrophysics Data System (ADS)

This review highlights the differences between the aerodynamics of high-speed trains and other types of transportation vehicles. The emphasis is on modern, high-speed trains, including magnetic levitation (Maglev) trains. Some of the key differences are derived from the fact that trains operate near the ground or a track, have much greater length-to-diameter ratios than other vehicles, pass close to each other and to trackside structures, are more subject to crosswinds, and operate in tunnels with entry and exit events. The coverage includes experimental techniques and results and analytical and numerical methods, concentrating on the most recent information available.

Schetz, Joseph A.

224

Noise thermometer.  

National Technical Information Service (NTIS)

The noise thermometry (NT) is a temperature measuring method by which the absolute temperature measurement can be performed with a very high accuracy and without any influence of ambient environments and of the thermal history of its NT sensor (electric r...

H. Von Brixy T. Kakuta

1996-01-01

225

Quantum Noise  

Microsoft Academic Search

Quantum Noise is advertised as a handbook, and this is indeed how it functions for me these days: it is a book that I keep within hand's reach, ready to be consulted on the proper use of quantum stochastic methods in the course of my research on quantum dots. I should point out that quantum optics, the target field for

C W J Beenakker

2005-01-01

226

Direct identification offlutter derivatives and aerodynamic admittances ofbridge decks  

Microsoft Academic Search

Flutter derivatives and aerodynamic admittances provide basis ofpredicting the critical wind speed in flutter and buffeting analysis oflong-span cable-supported bridges. In this paper, one popular stochastic system identification technique, covariance- driven stochastic subspace identification (SSI in short), is first presented for estimation of the flutter derivatives and aerodynamic admittances ofbridge decks f rom their random responses in turbulent flow. Numerical

Ming Gu; Xian-Rong Qin

2004-01-01

227

Constrained optimization of aerodynamic shapes via minimization of total drag  

Microsoft Academic Search

In this study, a robust and efficient approach to the multipoint constrained design is developed and applied to the optimization of aerodynamic wings. The objective is to minimize the total drag at fixed lift subject to various geometrical and aerodynamical constraints. The approach employs Genetic Algorithms (GAs) as an optimization tool in combination with a Reduced Order Models (ROM) method

S. Peigin; B. Epstein

2005-01-01

228

Chemical Fractionation in Chondrites by Aerodynamic Sorting of Chondritic Materials  

Microsoft Academic Search

Aerodynamic sorting in the nebula has been invoked directly or indirectly to account for the size variations of chondrules in different groups [1], associated size variations of chondrules and metal spherules in a CR chondrite [2], and variations in the oxygen isotopic compositions of H-L-LL chondrules and whole rocks [3]. We suggest that aerodynamic sorting processes affected the relative abundances

E. R. D. Scott; H. Haack

1993-01-01

229

FLPP IXV Re-Entry Vehicle, Aerodynamic Characterisation  

NASA Astrophysics Data System (ADS)

The European Space Agency ESA, has engaged in 2004, the IXV project (Intermediate eXperimental Vehicle) which is part of the FLPP (Future Launcher Preparatory Programme) aiming at answering to critical technological issues, while supporting the future generation launchers and improving in general European capabilities in the strategic field of atmospheric re-entry for space transportation, exploration, and scientific applications. The IXV key mission and system objectives are the design, development, manufacturing, assembling and on- ground to in-flight verification of an autonomous European lifting and aerodynamically controlled re- entry system, integrating the critical re-entry technologies at the system level. The current IXV vehicle is a slender body type exhibiting rounded shape and thick body. Since the beginning of the IXV project, an aerodynamic data base (AEDB) has been built up and continuously updated integrating the additional information mainly provided by means of CFD. The AEDB includes nominal aerodynamic data, a new set of free molecular aerodynamic coefficients as well as aerodynamic uncertainties. Through the phase B2/C1, complementary computations were performed (CFSE, EPFL, ASTRIUM, TAS, DAA) as well as wind tunnel tests such as ONERA S4ma, DLR H2K, DNW/NLR SST, FOI T1500. All data were analyzed and compared enabling the consolidation of the nominal aerodynamic and aerodynamic uncertainties as well. The paper presents the logic of work based on the system engineering plan with emphasis on the different prediction tools used aiming the final aerodynamic characterization of the IXV configuration.

Belmont, J.-P.; Cantinaud, O.; Tribot, J.-P.; Walloschek, T.

2009-01-01

230

State of the art in wind turbine aerodynamics and aeroelasticity  

Microsoft Academic Search

A comprehensive review of wind turbine aeroelasticity is given. The aerodynamic part starts with the simple aerodynamic Blade Element Momentum Method and ends with giving a review of the work done applying CFD on wind turbine rotors. In between is explained some methods of intermediate complexity such as vortex and panel methods. Also the different approaches to structural modelling of

M. O. L. Hansen; J. N. Sørensen; S. Voutsinas; N. Sørensen; H. Aa. Madsen

2006-01-01

231

The Influence of Windshield on Aerodynamic Performance of VAWT  

Microsoft Academic Search

In this paper, the reason is analyzed that the vertical axis wind turbine (VAWT) is always with low efficiency, on the basis that a new type of VAWT with windshield is proposed. Geometry of windshield has great influence on aerodynamic performance. The computational fluid dynamics (CFD) technique is introduced to investigate its aerodynamic performance. The results indicate that the new

Hu Yonghai; Tong Zhengming

2009-01-01

232

Experimental Investigation on Aerodynamic Characteristics of a Paraglider Wing  

Microsoft Academic Search

The fundamental aerodynamic characteristics of a paraglider's canopy are investigated in wind tunnel experiments using an inflatable cell model designed to represent the dynamic behaviors of each cell comprising the canopy. At attack angles greater than a few degrees, the cell model inflates fully. To characterize its aerodynamic characteristics, we focus our attention on the flow around the inflated cell

Mohammad Mashud; Akira Umemura

2006-01-01

233

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD  

Microsoft Academic Search

An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to enable accurate

W. P. Wolfe; S. S. Ochs

1997-01-01

234

Predicting Aerodynamic Characteristics of Typical Wind Turbine Airfoils Using CFD  

Microsoft Academic Search

An investigation was conducted into the capabilities and accuracy of a representa- tive computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pres- sure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to

Walter P. Wolfe

1997-01-01

235

Flat-plate aerodynamics at very low Reynolds number  

Microsoft Academic Search

Gas flow over a flat-plate airfoil at very-low Reynolds number is investigated in order to understand the aerodynamic issues related to micro air vehicle design and performance. Studies have shown that such low Reynolds number flow exhibits rarefied phenomena and a flat plate having a thickness ratio of 5% has better aerodynamic performance than conventional streamlined airfoils. This paper simulates

Quanhua Sun; Iain D. Boyd

2004-01-01

236

How Autopilot Requirements Constrain the Aerodynamic Design of Homing Missiles  

Microsoft Academic Search

When an aerodynamically controlled missile is used in a homing application, the transfer function of the vehicle becomes part of an overall homing and attitude control feedback loop. Therefore, the missile must be designed so that its aerodynamics meet the constraints required to accomplish homing successfully. For radar homing, these constraints are stringent enough to require an autopilot that controls

F. William Nesline; Mark L. Nesline

1984-01-01

237

Reliability and Applicability of Aerodynamic Measures in Dysphonia Assessment  

ERIC Educational Resources Information Center

|Aerodynamic measures are frequently used to analyse and document pathological voices. Some normative data are available for speakers from the English-speaking population. However, no data are available yet for Chinese speakers despite the fact that they are one of the largest populations in the world. The high variability of aerodynamic measures…

Yiu, Edwin M.-L.; Yuen, Yuet-Ming; Whitehill, Tara; Winkworth, Alison

2004-01-01

238

Aerodynamics inside a rapid compression machine  

SciTech Connect

The aerodynamics inside a rapid compression machine after the end of compression is investigated using planar laser-induced fluorescence (PLIF) of acetone. To study the effect of reaction chamber configuration on the resulting aerodynamics and temperature field, experiments are conducted and compared using a creviced piston and a flat piston under varying conditions. Results show that the flat piston design leads to significant mixing of the cold vortex with the hot core region, which causes alternate hot and cold regions inside the combustion chamber. At higher pressures, the effect of the vortex is reduced. The creviced piston head configuration is demonstrated to result in drastic reduction of the effect of the vortex. Experimental conditions are also simulated using the Star-CD computational fluid dynamics package. Computed results closely match with experimental observation. Numerical results indicate that with a flat piston design, gas velocity after compression is very high and the core region shrinks quickly due to rapid entrainment of cold gases. Whereas, for a creviced piston head design, gas velocity after compression is significantly lower and the core region remains unaffected for a long duration. As a consequence, for the flat piston, adiabatic core assumption can significantly overpredict the maximum temperature after the end of compression. For the creviced piston, the adiabatic core assumption is found to be valid even up to 100 ms after compression. This work therefore experimentally and numerically substantiates the importance of piston head design for achieving a homogeneous core region inside a rapid compression machine. (author)

Mittal, Gaurav; Sung, Chih-Jen [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States)

2006-04-15

239

Aerodynamic characteristics of popcorn ash particles  

SciTech Connect

Popcorn ash particles are fragments of sintered coal fly ash masses that resemble popcorn in low apparent density. They can travel with the flow in the furnace and settle on key places such as catalyst surfaces. Computational fluid dynamics (CFD) models are often used in the design process to prevent the carryover and settling of these particles on catalysts. Particle size, density, and drag coefficient are the most important aerodynamic parameters needed in CFD modeling of particle flow. The objective of this study was to experimentally determine particle size, shape, apparent density, and drag characteristics for popcorn ash particles from a coal-fired power plant. Particle size and shape were characterized by digital photography in three orthogonal directions and by computer image analysis. Particle apparent density was determined by volume and mass measurements. Particle terminal velocities in three directions were measured in water and each particle was also weighed in air and in water. The experimental data were analyzed and models were developed for equivalent sphere and equivalent ellipsoid with apparent density and drag coefficient distributions. The method developed in this study can be used to characterize the aerodynamic properties of popcorn-like particles.

Cherkaduvasala, V.; Murphy, D.W.; Ban, H.; Harrison, K.E.; Monroe, L.S. [University of Alabama, Birmingham, AL (United States). Dept. of Mechanical Engineering

2007-07-01

240

Computational Analysis of Noise Sources inside The High Speed Flow over a Generalized Bump  

Microsoft Academic Search

The aerodynamic noise sources around a three dimensional bump are studied. Firstly in this paper, validation of the numerical method with ILES using symmetric bump is discussed. Cp distribution on the bump is discussed and ILES simulation result shows good agreement with Visbal's numerical result 1 . The gradient of spanwise velocity fluctuation spectrum of present result agrees with gradient

Kentaro Okamoto; Taku Nonomura; Kozo Fujii

241

Drag and noise measurements on underwater vehicles with a riblet surface coating  

Microsoft Academic Search

The purpose of this study was to investigate both the drag and noise reducing effects of riblet surface coatings on marine vehicles. The use of microgrooves, or riblets, for skin friction reduction originated at NASA Langley for aerodynamic applications. Water tunnel tests at the Naval Ocean Systems Center (NOSC), San Diego, have shown that reductions in skin friction of up

Marc C. Gillcrist; Laurel W. Reidy

1989-01-01

242

Analysis of Fan Noise Spectrum Based onWake Characteristics of an Arc Blade  

Microsoft Academic Search

In this study, the wake characteristics of an arc blade were measured by means of a wind tunnel experiment; the characteristics were defined as the width of the wake, diameter of the vortex, ratio of the vortex structure, and local lift. The influence of the angle of attack on the aerodynamic noise of the blade was quantitatively predicted by using

Souichi SASAKI; Hidechito HAYASHI; Daisuke SATOH; Shutaro NASU

243

Application of Wake Characteristics to Prediction of Broadband Noise of a Multiblade Fan  

Microsoft Academic Search

In this study, the wake characteristics of an arc blade were measured by the wind tunnel experiment; the characteristics were defined as the width of the wake, diameter of the vortex, ratio of the vortex scale, and the local lift. The influence of the angle of attack on the aerodynamic noise of the blade was quantitatively predicted by using these

Soichi Sasaki; Hidechito Hayashi

2008-01-01

244

Characterizing computer cooling fan noise.  

PubMed

Computer cooling fan noise is studied theoretically, focusing on the radiation from the interaction between rotor blades and motor struts. The source is decomposed into axial thrust, circumferential drag, and radial force. There is no sound-power coupling among the three components. The index of spatial spinning pressure mode plays the key role in noise radiation. The leading modes are the zeroth, or coincident, mode for thrust and the first mode for the drag and radial force. The effect of source noncompactness is quantified and found to be substantial only for higher-order radiation modes. The sound powers of the leading modes follow a sixth-power law, while the next high-order modes follow an eighth-power law. Quantitative analysis shows that the drag force can be equally noisy as the coincident thrust force. Based on an empirical aerodynamic model of rotor-strut interaction, it is found that the total sound power is more sensitive to the number of struts than rotor blades. Numerical examples are given to demonstrate how the struts can be optimized for typical cooling fan conditions. PMID:14714801

Huang, Lixi

2003-12-01

245

Aerodynamic stability technology for maneuverable missiles. Volume 1: Configuration aerodynamic characteristics  

Microsoft Academic Search

This study developed empirical methods to predict aerodynamic characteristics of body-tail, body-wing-tail and body-strake-tail missile configurations. Methods cover the Mach number range from 0.6 to 3.0. Methods cover the individual body and tail characteristics at angles of attack from 0 to 180 degrees. For winged bodies the methods encompass angles of attack up to about 30 degrees. All mutual interference

G. F. Aiello; M. C. Bateman

1979-01-01

246

CFD calculations of S809 aerodynamic characteristics  

SciTech Connect

Steady-state, two-dimensional CFD calculations were made for the S809 laminar-flow, wind-turbine airfoil using the commercial code CFD-ACE. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data from the Delft University 1.8 m x 1.25 m low-turbulence wind tunnel. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to-turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-{epsilon} model, is not appropriate at angles of attack with flow separation.

Wolfe, W.P. [Sandia National Labs., Albuquerque, NM (United States); Ochs, S.S. [Iowa State Univ., Ames, IA (United States)

1997-01-01

247

Improving the efficiency of aerodynamic shape optimization  

NASA Astrophysics Data System (ADS)

The computational efficiency of an aerodynamic shape optimization procedure that is based on discrete sensitivity analysis is increased through the implementation of two improvements. The first improvement involves replacing a grid-point-based approach for surface representation with a Bezier-Bernstein polynomial parameterization of the surface. Explicit analytical expressions for the grid sensitivity terms are developed for both approaches. The second improvement proposes the use of Newton's method in lieu of an alternating direction implicit methodology to calculate the highly converged flow solutions that are required to compute the sensitivity coefficients. The modified design procedure is demonstrated by optimizing the shape of an internal-external nozzle configuration. Practically identical optimization results are obtained that are independent of the method used to represent the surface. A substantial factor of 8 decrease in computational time for the optimization process is achieved by implementing both of the design procedure improvements.

Burgreen, Greg W.; Baysal, Oktay; Eleshaky, Mohamed E.

1994-01-01

248

Experimental Aerodynamics of Mesoscale Trailing Edge Actuators  

NASA Astrophysics Data System (ADS)

Experiments were performed on a wing with segmented Gurney flaps. Each of the sixteen active flaps is approximately 1.5can be actuated in only two positions: 90 degrees up or 90 degrees down. Wind tunnel experiments were conducted at chord Reynolds numbers up to 800,000. Measurements include the determination of aerodynamic forces and moments using a 6 DOF balance, surface pressure profiles, and wake surveys. Actuation of the full span of the airfoil from the up position to the down position increases the lift coefficient by approximately 0.6 for low to moderate angles of attack. The flaps have a reduced but still significant effect past stall. The overall changes in wing loads are linear with the number of flaps actuated, suggesting that simple control laws may be used. However, surface pressure measurements indicate that each flap affects the section lift over a substantial span. A study of the transient performance of the flaps is underway.

Solovitz, Stephen; Eaton, John

2001-11-01

249

Multiprocessing on supercomputers for computational aerodynamics  

SciTech Connect

Little use is made of multiple processors available on current supercomputers (computers with a theoretical peak performance capability equal to 100 MFLOPS or more) to improve turnaround time in computational aerodynamics. The productivity of a computer user is directly related to this turnaround time. In a time-sharing environment, such improvement is this speed achieved when multiple processors are used efficiently to execute an algorithm. The authors of this paper apply the concept of multiple instructions and multiple data (MIMD) through multitasking via a strategy that requires relatively minor modifications to an existing code for a single processor. This approach maps the available memory to multiple processors, exploiting the C-Fortran-Unix interface. The existing code is mapped without the need for developing a new algorithm. The procedure for building a code utilizing this approach is automated with the Unix stream editor.

Mehta, V.B.; Yarrow, M. (NASA Ames Research Center, Moffett Field, CA (US))

1991-01-01

250

Aerodynamic levitation : an approach to microgravity.  

SciTech Connect

Measurements of the thermophysical and structural properties of liquid materials at high temperature have undergone considerable development in the past few years. Following improvements in electromagnetic levitation, aerodynamic levitation associated with laser heating has shown promise for assessing properties of different molten materials (metals, oxides, and semiconductors), preserving sample purity over a wide range of temperatures and under different gas environments. The density, surface tension and viscosity are measured with a high-speed video camera and an image analysis system. Results on nickel and alumina show that small droplets can be considered in the first approximation to be under microgravity conditions. Using a non-invasive contactless technique recently developed to measure electrical conductivity, results have been extended to variety of materials ranging from liquid metals and liquid semiconductors to ionically conducting materials. The advantage of this technique is the feasibility of monitoring changes in transport occurring during phase transitions and in deeply undercooled states.

Glorieux, B.; Saboungi, M.-L.; Millot, F.; Enderby, J.; Rifflet, J.-C.

2000-12-05

251

Beyond robins: aerodynamic analyses of animal flight  

PubMed Central

Recent progress in studies of animal flight mechanics is reviewed. A range of birds, and now bats, has been studied in wind tunnel facilities, revealing an array of wake patterns caused by the beating wings and also by the drag on the body. Nevertheless, the quantitative analysis of these complex wake structures shows a degree of similarity among all the different wake patterns and a close agreement with standard quasi-steady aerodynamic models and predictions. At the same time, new data on the flow over a bat wing in mid-downstroke show that, at least in this case, such simplifications cannot be useful in describing in detail either the wing properties or control prospects. The reasons for these apparently divergent results are discussed and prospects for future advances are considered.

Hedenstrom, Anders; Spedding, Geoffrey

2008-01-01

252

Methods of reducing vehicle aerodynamic drag  

SciTech Connect

A small scale model (length 1710 mm) of General Motor SUV was built and tested in the wind tunnel for expected wind conditions and road clearance. Two passive devices, rear screen which is plate behind the car and rear fairing where the end of the car is aerodynamically extended, were incorporated in the model and tested in the wind tunnel for different wind conditions. The conclusion is that rear screen could reduce drag up to 6.5% and rear fairing can reduce the drag by 26%. There were additional tests for front edging and rear vortex generators. The results for drag reduction were mixed. It should be noted that there are aesthetic and practical considerations that may allow only partial implementation of these or any drag reduction options.

Sirenko V.; Rohatgi U.

2012-07-08

253

A new idea based on the field test data for guided aircraft aerodynamic model parameters modification  

Microsoft Academic Search

The aerodynamic parameters model is one of important models of guided aircraft simulation system, the modification of the aerodynamic parameters model is an important aspect that the simulation test should analyze. Based on the analysis of the existing aerodynamic parameters modification methods, this paper proposes a new aerodynamic parameters modification method, which build on the field test data, and its

Li Xing-Wei; Pan Xiao

2008-01-01

254

Fourier analysis of the aerodynamic behavior of cup anemometers  

NASA Astrophysics Data System (ADS)

The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the ratio between the first two coefficients in the Fourier series decomposition of the normal-to-the-cup aerodynamic force.

Pindado, Santiago; Pérez, Imanol; Aguado, Maite

2013-06-01

255

Helicopter main rotor/tail rotor noise radiation characteristics from scaled model rotor experiments in the DNW  

NASA Astrophysics Data System (ADS)

A wind tunnel study was performed to investigate the noise characteristics and directivity pattern of a 40 percent scaled helicopter rotor system (BO 105 main/tail rotor model). The major objectives of the study were to establish the importance of the tail rotor with respect to the overall noise radiation and to determine the noise reduction potential of aerodynamically improved blade design. The results show that under descent flight condition, where strong main rotor blade-vortex interaction occurs, the tail rotor contribution is of secondary order, while at climb condition the tail rotor dominates the noise radiation over a significant range of noise emission angles. Main-/tail-rotor aerodynamic interference noise does not appear to be a prime contributor to the total noise emission. The acoustic benefit from fully utilizing the potential of aerodynamically improved blade design was determined: maintaining rotor thrust while reducing the tip speed of such blades by 10 percent yielded noise reductions on the order of 3 to 4 dB and in certain directions in excess of 7 to 8 dB.

Schultz, K.-J.; Splettstoesser, W. R.

256

Cosmic Noise  

NASA Astrophysics Data System (ADS)

1. Prologue; 2. Searching for solar hertzian waves; 3. Jansky and his star static; 4. Grote Reber: science in your backyard; 5. Wartime discovery of the radio sun; 6. Hey's army group after the war; 7.Radiophysics laboratory, Sydney; 8. Ryle's group at the Cavendish; 9. Lovell at Jodrell Bank; 10. Other radio astronomy groups before 1952; 11. Meteor radar; 12. Reaching for the moon; 13. The radio sun; 14. Radio stars; 15. Theories of galactic noise; 16. The 21-cm hydrogen line; 17. New astronomers; 18. A new astronomy; Appendixes; References; Index.

Sullivan, Woodruff T., III

2009-11-01

257

A method of infrared imaging missile's aerodynamic heating modeling and simulations  

NASA Astrophysics Data System (ADS)

The infrared (IR) imaging missile's dome will be heated when fly at high speed in the atmosphere because of the friction of the air flow blocking. The detector's performance will be decline if the dome surface is heated to a certain temperature. In this paper, we find a right way to evaluate the aerothermal effects in the imaging and information processing algorithm. Which have three steps including the aerothermal radiation calculation, quantization and image reconstruction. Firstly, the aerothermal radiation is calculated by using a combination of both methods of theoretical analysis and experiment data. Secondly, the relationship between aerothermal radiation and IR images background mean gray and noise can be calculated through the analysis of the experiment data. At last, we can rebuild an aerodynamic heating effect of infrared images fusion with target and decoy, which can be used for virtual prototyping platform missile trajectory simulation. It can be found that the above constructed images have good agreements with the actual image according to comparison between the simulation data and experiment data. It is an economic method that can solve the lab aerodynamic heating simulation and modeling problems.

Cao, Chunqin; Xiang, Jingbo; Zhang, Xiaoyang; Wang, Weiqiang

2013-09-01

258

Investigating Complex Aerodynamic Flows with a Laser Velocimeter.  

National Technical Information Service (NTIS)

The application of the laser velocimeter in the study of two highly complex aerodynamic flows is discussed. In the first experiment, the laser velocimeter was used with frequency tracking electronics to survey the multiple vortex wake structure behind a m...

J. C. Biggers K. L. Orloff T. W. Ekstedt V. R. Corsiglia

1976-01-01

259

Aerodynamic Characteristics of Passenger Vehicle/Trailer Combinations.  

National Technical Information Service (NTIS)

An experimental investigation of combination vehicle aerodynamics, pertinent to crosswind and truck-induced disturbances, was performed. This was accomplished via 1/10 scale model wind tunnel measurements performed on 6 trailers and 4 tow vehicles, and va...

J. W. Zellner

1982-01-01

260

Aerodynamics of flapping wings with fluttering trailing edges  

NASA Astrophysics Data System (ADS)

Our previous work on the aerodynamics of passive flexible flapping wings showed that there is a strong relationship between the dynamics of trailing edge and the size of the leading edge vortex, therefore aerodynamic forces. Here we investigated the aerodynamic effects of active trailing edges. The experiments were conducted on a model flapping wing in an oil tank. During static tests, the trailing edge bending angle was held constant from the angle of attack of the upper portion of the rigid wing. For dynamic cases, the trailing edge was controlled to flutter with a prescribed frequency and amplitude. Force measurements and PIV results show that trailing edge flexion/camber strongly correlates with the leading edge vortex and the aerodynamic forces. In addition, large instantaneous force variations are observed in the dynamic fluttering cases, suggesting that trailing edge can be used for force modulation in MAVs.

Zhao, Liang; Hu, Zheng; Roll, Jesse; Deng, Xinyan

2010-11-01

261

Aerodynamic and Related Hydrodynamic Studies Using Water Facilities.  

National Technical Information Service (NTIS)

This report consists of 32 papers which review related problems, experiences and advancements in aeronautical and maritime fluid dynamics through the use of water facilities. There has been an increasing use of water facilities for aerodynamic investigati...

1987-01-01

262

Study of the Aerodynamic Interference Effects during Aerial Refueling.  

National Technical Information Service (NTIS)

This report investigated the feasibility of using an analytical approach and the vortex lattice method (VLM) to evaluate aerodynamic interference effects present during aerial refueling. While KC-10 tanker and a B-52 receiver were studied, the method appl...

E. H. Hoganson

1983-01-01

263

Aerodynamic, structural, and trajectory analysis of ASTRID-1 vehicle.  

National Technical Information Service (NTIS)

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 Demonstrat...

L. S. Glover A. P. Iwaskiw M. A. Oursler L. L. Perini E. D. Schaefer

1994-01-01

264

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD.  

National Technical Information Service (NTIS)

An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and ae...

W. P. Wolfe S. S. Ochs

1997-01-01

265

Computerized Data Catalog and Retrieval System for Deployable Aerodynamic Decelerators.  

National Technical Information Service (NTIS)

In the development of a computerized data catalog and data retrieval system for deployable aerodynamic decelerators, the results were twofold: (1) a list of parameters which completely define the information pertinent to these decelerators; and (2) a data...

T. J. Hogan J. J. Schauer

1967-01-01

266

Aerodynamic Methodology (Bodies with and without Tails in Transonic Flow).  

National Technical Information Service (NTIS)

This report presents empirical methods for predicting the aerodynamic characteristics of slender missile bodies with and without deflected horizontal tails in the following ranges of angle of attack and Mach number: (1) Bodies: Angles to 90 degrees, Mach ...

J. E. Fidler M. C. Bateman

1974-01-01

267

Aerodynamics problems of space probes in comet atmosphere  

Microsoft Academic Search

The paper deals with aerodynamic problems connected with a space probe moving in a rarefied gas-dust Halley's comet atmosphere on exposure to electromagnetic solar radiation. Their relative approach velocity will be 78 km\\/s.

Iu. A. Ryzhov; V. P. Bass; V. P. Kariagin; V. M. Kovtunenko; K. N. Kuzovkin

1985-01-01

268

Learning Activities: Students and Recycling. [and] Automobile Aerodynamics.  

ERIC Educational Resources Information Center

|The first learning activity is intended to heighten students' awareness of the need for recycling, reuse, and reduction of materials; the second explores the aerodynamics of automobiles. Both include context, concept, objectives, procedure, and materials needed. (SK)|

McLaughlin, Charles H., Jr.; Schieber, Rich

1994-01-01

269

Low-Density Aerodynamics of the Stardust Sample Return Capsule.  

National Technical Information Service (NTIS)

The aerodynamics of the Stardust Sample Return Capsule are analyzed in the low-density, transitional flow regime using free-molecular, Direct Simulation Monte Carlo, Navier-Stokes, and Newtonian methods to provide inputs for constructing a transitional fl...

R. G. Wilmoth R. A. Micheltree J. N. Moss

2004-01-01

270

Computational Investigation of the Aerodynamic Effects on Fluidic Thrust Vectoring.  

National Technical Information Service (NTIS)

A computational investigation of the aerodynamic effects on fluidic thrust vectoring has been conducted. Three-dimensional simulations of a two-dimensional, convergent-divergent (2DCD) nozzle with fluidic injection for pitch vector control were run with t...

K. A. Deere

2000-01-01

271

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

National Technical Information Service (NTIS)

A computer program written to calculate the proximity aerodynamic force and moment coefficients of the Orbiter/Shuttle Carrier Aircraft (SCA) vehicles based on flight instrumentation is described. The ground reduced aerodynamic coefficients and instrument...

D. J. Homan

1977-01-01

272

Aerodynamic size association of 7Be in ambient aerosols  

Microsoft Academic Search

The aerodynamic size distribution of 7Be in ambient aerosol particles was determined by using 1-ACFM cascade impactors. The activity distribution of 7Be measured by ?-spectrometry (E? = 447keV), was largely associated with submicron aerosols in the accumulation mode (0.4–2.0 ?m). The activity median aerodynamic diameter, AM AD ranged from 0.76 to 1.18?m (average 0.90?m), indicating post-condensation growth either in the

C. Papastefanou; A. Ioannidou

1995-01-01

273

ROBUST STRUCTURAL DESIGN FOR ACTIVE AEROELASTIC WING WITH AERODYNAMIC UNCERTAINTIES  

Microsoft Academic Search

A multidisciplinary design study for Active Aeroelastic Wing technology considering the uncertainty in maneuver loads estimated by linear aerodynamic theory is presented. The study makes use of a design of experiments\\/response surface methodology and modal-based structural optimization to construct deterministic relationships between wing structural weight and control laws design, based on linear aerodynamics. CFD Navier-Stokes analysis is then used to

P. Scott Zink; Daniella E. Raveh; Dimitri N. Mavris

2000-01-01

274

Aerodynamics and design for ultra-low Reynolds number flight  

Microsoft Academic Search

Growing interest in micro-air-vehicles has created the need for improved understanding of the relevant aerodynamics. A reasonable starting point is the study of airfoil aerodynamics at Reynolds numbers below 10,000, here termed ultra-low Reynolds numbers. The effects of airfoil geometry on performance are explored using an incompressible Navier-Stokes solver. Variations in thickness, camber, and the shape of leading and trailing

Peter Josef Kunz

2003-01-01

275

Numerical investigation of unsteady aerodynamic characteristics of a pitching missile  

Microsoft Academic Search

Three-dimensional Reynolds averaged Navier–Stokes numerical simulations were carried out to predict the aerodynamic loads of a pitching winged missile based on the finite volume method. The Baldwin–Lomax eddy viscosity model with the modifications suggested by Degani and Schiff was used here. The computational results of the aerodynamic loads of a slender revolution body are also given, and agreed well with

Lizhi Yang; Minghai Wang; Zhenghong Gao

2011-01-01

276

Advanced Aerodynamic Design of Passive Porosity Control Effectors  

Microsoft Academic Search

Abstract This paper describes aerodynamic,design work aimed at developing,a passive ,porosity control effector system for a generic ,tailless fighter aircraft. As part of this work, a computational design tool was developed and used to layout ,passive porosity effector systems ,for longitudinal and lateral-directional control at a lowspeed, high angle of attack condition. Aerodynamic analysis was ,conducted ,using the NASA Langley

C. A. Hunter; S. A. Viken; R. M. Wood; S. X. S. Bauer

2001-01-01

277

On the aerodynamic and aeroelastic response of a bridge tower  

Microsoft Academic Search

This work is concerned with the aerodynamic characterization of a cable-stayed bridge tower in free-standing configuration; experimental tests were performed at Politecnico di Milano Wind Tunnel under smooth and turbulent flow conditions. The aerodynamic behavior of the tower was investigated through static and dynamic tests on a 1:30 scale sectional model; the whole structure response has been studied using a

Marco Belloli; Fabio Fossati; Stefano Giappino; Sara Muggiasca; Marco Villani

2011-01-01

278

REVIEW OF X-33 HYPERSONIC AERODYNAMIC AND AEROTHERMODYNAMIC DEVELOPMENT  

Microsoft Academic Search

A review of the experimental and computational studies performed at NASA Langley Research Center (LaRC) to support the optimization and benchmarking of the hypersonic aerodynamic and aerothermodynamic databases for the X-33 vehicle is presented. A synoptic of the testing, computational, and analysis capabilities at LaRC applied to these studies is given. Analy- ses of the hypersonic aerodynamic characteris- tics, control

Richard A. Thompson

2000-01-01

279

Aerodynamics of an Australian Rules Foot Ball and Rugby Ball  

Microsoft Academic Search

The aerodynamic behavior of a Rugby ball and an Australian Rules foot ball is complex and significantly differs from spherical\\u000a sports balls due to their complex ellipsoidal shapes. Although prior aerodynamic studies have been conducted on soccer, tennis,\\u000a cricket and golf balls, scant information about the Australian Rules and Rugby balls is available in the public domain. In\\u000a order to

Firoz Alam; Aleksandar Subic; Simon Watkins; Alexander John Smits

280

Aerodynamic Performances of Corrugated Dragonfly Wings at Low Reynolds Numbers  

NASA Astrophysics Data System (ADS)

The cross-sections of dragonfly wings have well-defined corrugated configurations, which seem to be not very suitable for flight according to traditional airfoil design principles. However, previous studies have led to surprising conclusions of that corrugated dragonfly wings would have better aerodynamic performances compared with traditional technical airfoils in the low Reynolds number regime where dragonflies usually fly. Unlike most of the previous studies of either measuring total aerodynamics forces (lift and drag) or conducting qualitative flow visualization, a series of wind tunnel experiments will be conducted in the present study to investigate the aerodynamic performances of corrugated dragonfly wings at low Reynolds numbers quantitatively. In addition to aerodynamics force measurements, detailed Particle Image Velocimetry (PIV) measurements will be conducted to quantify of the flow field around a two-dimensional corrugated dragonfly wing model to elucidate the fundamental physics associated with the flight features and aerodynamic performances of corrugated dragonfly wings. The aerodynamic performances of the dragonfly wing model will be compared with those of a simple flat plate and a NASA low-speed airfoil at low Reynolds numbers.

Tamai, Masatoshi; He, Guowei; Hu, Hui

2006-11-01

281

Aerodynamic Flow Control of a Maneuvering Airfoil  

NASA Astrophysics Data System (ADS)

The unsteady aerodynamic forces and moments on a maneuvering, free-moving airfoil are varied in wind tunnel experiments by controlling vorticity generation/accumulation near the surface using hybrid synthetic jet actuators. The dynamic characteristics of the airfoil that is mounted on a 2-DOF traverse are controlled using position and attitude feedback loops that are actuated by servo motors. Bi-directional changes in the pitching moment are induced using controllable trapped vorticity concentrations on the suction and pressure surfaces near the trailing edge. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and velocity measurements that are taken phase-locked to the commanded actuation waveform. The time scales associated with the actuation process is determined from PIV measurements of vorticity flux downstream of the trailing edge. Circulation time history shows that the entire flow over the airfoil readjusts within about 1.5 TCONV, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales commensurate with the flow's convective time scale, and that the maneuver response is only limited by the inertia of the platform. Supported by AFSOR.

Brzozowski, Daniel P.; Culp, John; Glezer, Ari

2010-11-01

282

Aerodynamic characteristics of an oscillating airfoil  

NASA Astrophysics Data System (ADS)

Results are reported from wind tunnel tests to study the effects of dynamic aerodynamics on the efficiency of a NACA 0018 airfoil used on a Darreius vertical axis wind turbine (VAWT). The topic is of interest because of uncontrolled pitching which occurs during operation and which produces stall, turbulence and separation effects that reduce efficiency. Present stream-tube theory and axial momentum models are not applicable in the unstable regimes. The wind tunnel tests were conducted with a 45 m/sec flow with an Re of 1.5 million. The situation mimicked typical wind turbine operational conditions. The airfoil was mounted on a hydraulic actuator to allow it to rotate about its quarter-chord location and to control the extent and frequency of oscillations. Data were also gathered on the performance in a steady flow for comparative purposes. Summary data are provided on the static and total pressures over a complete cycle of oscillation, and related to the angles of attack, time of onset of stall, and the lift and drag coefficients. The limitations of the study with regard to the absence of consideration of the flow acceleration experienced by an advancing blade are noted.

Wickens, R. H.

1986-03-01

283

Aerodynamics of high aspect-ratio sails  

NASA Astrophysics Data System (ADS)

Experiments studying the aerodynamics of a 25circular-arc sail section (representative of an AC gennaker cross-section) have been undertaken in the 7x10 ft tunnels at NASA-Ames and Georgia Tech. The aims of the study are to gain a deeper physical understanding of the flow past downwind sails at various angles of incidence and Reynolds numbers, and to create a comprehensive database for validation of numerical models and turbulence models used by the yacht research community and competitive sailing industry. The reason for testing a rectangular planform sail with no spanwise variation in twist or cross-section is to first provide a detailed understanding of the flow topology around generic sail sections. Currently, data of sufficient accuracy to be used for CFD validation are not available. 3D experiments with realistic sail planforms and twisted onset flow are planned for the future. Two models have been tested, one with an AR of 15 and constructed from steel and the other with an AR of 10 and constructed from carbon-fiber and foam. The latter model has pressure tappings, whilst the former was coated with PSP. Pressure distributions, surface flow visualization and PIV reveal the details of the changing flow patterns and separation types with varying angle of incidence.

Crook, Andrew; Gerritsen, Margot

2003-11-01

284

Recent advances in transonic axial compressor aerodynamics  

NASA Astrophysics Data System (ADS)

Transonic axial flow compressors are fundamental components in aircraft engines as they make it possible to maximize pressure ratios per stage unit. This is achieved through a careful combination of both tangential flow deflections and, above all, by taking advantage of shock wave formation around the rotor blades. The resulting flow field is really complex as it features highly three-dimensional inviscid/viscous structures, strong shock-boundary layer interaction and intense tip clearance effects which negatively influence compressor efficiency. Complications are augmented at part load operation, where stall—related phenomena occur. Therefore, considerable research efforts are being spent, both numerically and experimentally, to improve efficiency and stall margin at peak efficiency and near stall operation. The present work aims at giving a complete review of the most recent advances in the field of aerodynamic design and operation of such machines. A great emphasis has been given to highlight the most relevant contribution in this field and to suggest the prospects for future developments.

Biollo, Roberto; Benini, Ernesto

2013-01-01

285

Oscillating cascade aerodynamics at large mean incidence  

SciTech Connect

The aerodynamics of a cascade of airfoils oscillating in torsion about the midchord is investigated experimentally at a large mean incidence angle and, for reference, at a low mean incidence angle. The airfoil section is representative of a modern, low-aspect-ratio, fan blade tip section. Time-dependent airfoil surface pressure measurements were made for reduced frequencies of up to 1.2 for out-of-phase oscillations at a Mach number of 0.5 and chordal incidence angles of 0 and 10 deg; the Reynolds number was 0.9 {times} 10{sup 6}. For the 10 deg chordal incidence angle, a separation bubble formed at the leading edge of the suction surface. The separated flow field was found to have a dramatic effect on the chordwise distribution of the unsteady pressure. In this region, substantial deviations from the attached flow data were found, with the deviations becoming less apparent in the aft region of the airfoil for all reduced frequencies. In particular, near the leading edge the separated flow had a strong destabilizing influence while the attached flow had a strong stabilizing influence.

Buffum, D.H. [NASA Lewis Research Center, Cleveland, OH (United States); Capece, V.R.; King, A.J. [Univ. of California, Davis, CA (United States). Dept. of Mechanical and Aeronautical Engineering; El-Aini, Y.M. [Pratt and Whitney, West Palm Beach, FL (United States)

1998-01-01

286

Rudolf Hermann, wind tunnels and aerodynamics  

NASA Astrophysics Data System (ADS)

Rudolf Hermann was born on December 15, 1904 in Leipzig, Germany. He studied at the University of Leipzig and at the Aachen Institute of Technology. His involvement with wind tunnels began in 1934 when Professor Carl Wieselsberger engaged him to work at Aachen on the development of a supersonic wind tunnel. On January 6, 1936, Dr. Wernher von Braun visited Dr. Hermann to arrange for use of the Aachen supersonic wind tunnel for Army problems. On April 1, 1937, Dr. Hermann became Director of the Supersonic Wind Tunnel at the Army installation at Peenemunde. Results from the Aachen and Peenemunde wind tunnels were crucial in achieving aerodynamic stability for the A-4 rocket, later designated as the V-2. Plans to build a Mach 10 'hypersonic' wind tunnel facility at Kochel were accelerated after the Allied air raid on Peenemunde on August 17, 1943. Dr. Hermann was director of the new facility. Ignoring destruction orders from Hitler as WWII approached an end in Europe, Dr. Hermann and his associates hid documents and preserved wind tunnel components that were acquired by the advancing American forces. Dr. Hermann became a consultant to the Air Force at its Wright Field in November 1945. In 1951, he was named professor of Aeronautical Engineering at the University of Minnesota. In 1962, Dr. Hermann became the first Director of the Research Institute at the University of Alabama in Huntsville (UAH), a position he held until he retired in 1970.

Lundquist, Charles A.; Coleman, Anne M.

2008-04-01

287

Sweeping Noise Blanker.  

National Technical Information Service (NTIS)

A noise rejection circuit is described for a communications receiver in which the input to the receiver is continually sampled by a sweeping heterodyne oscillator to develop a difference frequency noise signal which represents the input noise over a wide ...

D. M. Dilley

1978-01-01

288

Portable Air Compressor Noise.  

National Technical Information Service (NTIS)

The character and magnitude of compressor noise, the technology and cost of quieting compressors, the validity of manufacturers' data, and propagation of compressor noise in the community are examined in this report. It is found that the noise radiated by...

W. N. Patterson R. A. Ely G. G. Huggins

1974-01-01

289

Turbomachinery noise  

NASA Astrophysics Data System (ADS)

Summarized here are key advances in experimental techniques and theoretical applications which point the way to a broad understanding and control of turbomachinery noise. On the experimental side, the development of effective inflow control techniques makes it possible to conduct, in ground based facilities, definitive experiments in internally controlled blade row interactions. Results can now be valid indicators of flight behavior and can provide a firm base for comparison with analytical results. Inflow control coupled with detailed diagnostic tools such as blade pressure measurements can be used to uncover the more subtle mechanisms such as rotor strut interaction, which can set tone levels for some engine configurations. Initial mappings of rotor wake-vortex flow fields have provided a data base for a first generation semiempirical flow disturbance model. Laser velocimetry offers a nonintrusive method for validating and improving the model. Digital data systems and signal processing algorithms are bringing mode measurement closer to a working tool that can be frequently applied to a real machine such as a turbofan engine. On the analytical side, models of most of the links in the chain from turbomachine blade source to far field observation point have been formulated. Three dimensional lifting surface theory for blade rows, including source noncompactness and cascade effects, blade row transmission models incorporating mode and frequency scattering, and modal radiation calculations, including hybrid numerical-analytical approaches, are tools which await further application.

Groeneweg, John F.; Sofrin, Thomas G.; Rice, Edward J.; Gliebe, Phillip R.

1991-08-01

290

Numerical Prediction of Laminar Instability Noise for NACA 0012 Aerofoil  

NASA Astrophysics Data System (ADS)

Aerofoil self-generated noise is recognized to be of fundamental importance in the frame of applied aeroacoustics and the use of computational methods to assess the acoustic behaviour of airframe components challenges an even larger community of engineers and scientists. Several noise generation mechanisms can be found which are mainly related to the physical development of turbulence over the boundary layer. They can be classified in 3 main categories: the Turbulent Boundary Layer--Trailing Edge noise (TBL-TE), the Laminar Boundary Layer--Vortex Shedding (LBL-VS) noise and the Separation Stall (S-S) noise. The TBL-TE is mainly related to the noise generated by turbulent eddies which develop into the boundary layer and usually exhibits a broadband spectrum. The LBL-VS is related to laminar instabilities that can occur within the boundary layer which are responsible for a very late transition and generate a typical peaked tonal noise, while the S-S noise mainly results from the development of large vortices after the separation point. In this paper we propose a numerical analysis targeted to the simulation the LBL-VS noise mechanisms on a NACA 0012 aerofoil, tested at a Reynolds number of 1.1 M and Mach number of 0.2. The aerodynamic simulation is performed with a 2D transient RANS approach using the k-? transitional turbulence model, while the acoustic computations are performed with the FfowcsWilliams-Hawkings (FW-H) acoustic analogy and with a Finite Element (FE) approach solving Lighthill's wave equation. Computed noise spectra are compared with experimental data published by NASA showing a good agreement both for peak location as well as for the predicted noise level.

de Gennaro, Michele; Hueppe, Andreas; Kuehnelt, Helmut; Kaltenbacher, Manfred

2011-09-01

291

Aerodynamics support of research instrument development  

NASA Astrophysics Data System (ADS)

A new velocimetry system is currently being developed at NASA LaRC. The device, known as a Doppler global velocimeter (DGV), can record three velocity components within a plane simultaneously and in near real time. To make measurements the DGV, like many other velocimetry systems, relies on the scattering of light from numerous small particles in a flow field. The particles or seeds are illuminated by a sheet of laser light and viewed by two CCD cameras. The scattered light from the particles will have a frequency which is a function of the source laser light frequency, the viewing angle, and most importantly the seed velocities. By determining the scattered light intensity the velocity can be measured at all points within the light sheet simultaneously. Upon completion of DGV component construction and initial check out a series of tests in the Basic Aerodynamic Research (wind) Tunnel (BART) are scheduled to verify instrument operation and accuracy. If the results are satisfactory, application of the DGV to flight measurements on the F-18 High Alpha Research Vehicle (HARV) are planned. The DGV verification test in the BART facility will utilize a 75 degree swept delta wing model. A major task undertaken this summer included evaluation of previous results for this model. A specific series of tests matching exactly the previous tests and exploring new DGV capabilities were developed and suggested. Another task undertaken was to study DGV system installation possibilities in the F-18 HARV aircraft. In addition, a simple seeding system modification was developed and utilized to make Particle Imaging Velocimetry (PIV) measurements in the BART facility.

Miller, L. Scott

1990-09-01

292

A NUMERICAL STUDY OF FLUID FLOW PAST A CIRCULAR CYLINDER AT RE=3900 AND A PRACTICAL APPROACH TO NOISE PREDICTION  

Microsoft Academic Search

The aim of this study is the prediction of the aerodynamic noise generated by the fluid flow past a circular cylinder at Re=3900, combining numerical simulation of the fluid flow with an analytical noise evaluation. This case has been extended to the flow around a cylinder with Re=140000. The Large Eddy Simulation (LES) turbulence model of FLUENT v6.3 is used

A. Pradera; G. Keith; F. Jacobsen; N. Gil-Negrete; A. Rivas

293

Programme of Research into the Aerodynamics, Stability and Control Characteristics of a Combat Aircraft Having a Forward Swept Wing.  

National Technical Information Service (NTIS)

The aerodynamic stability and control characteristics of the forward swept wing aircraft, and likely stability augmentation requirements were studied. It is found that: (1) the theoretical aerodynamic models match the observed aerodynamic performance; (2)...

M. V. Cook F. Heydari

1985-01-01

294

Low Dimensional Modeling And Computational Analysis of Dragonfly Wing Aerodynamics  

NASA Astrophysics Data System (ADS)

High-fidelity numerical simulations are being used to examine the key aerodynamic features and lift production of insect wings. However, the kinematics of the insect's wing and the resulting aerodynamics is highly complex, and does not lend itself easily to analysis based on simple notions of pitching/heaving kinematics or lift/drag based propulsive mechanisms. A more inventive approach is therefore needed to dissect the wing gait and gain insight into the remarkable aerodynamic performance of the insect's wing. The focus of the current investigation is on the aerodynamics of the wing of a dragonfly (Erythemis Simplicicollis) in hovering motion. The three-dimensional, time-dependent wing kinematics is obtained via a high-speed photogrammetry system. Singular Value Decomposition (SVD) is then applied to extract the essential features of the wing gait. The SVD spectrum shows that the first four modes capture more than 80% of the motion. Aerodynamics of wings flapping with kinematics synthesized from SVD modes will be discussed in detail.

Ren, Yan; Wan, Hui; Dong, Haibo

2011-11-01

295

A velocity parameter for the correlation of axial fan noise  

NASA Astrophysics Data System (ADS)

An aerodynamic parameter that relates subsonic axial fan noise to the fundamental flow behavior in the blade row of a fan is proposed. The parameter is the peak or maximum blade surface velocity in the rotating reference frame and includes, either explicitly or implicitly, the influence of tip speed, volume flow rate, pressure rise, shaft horsepower and efficiency. Correlation of the noise associated with a very broad range of axial fans yields good agreement and collapse of data when compared to currently used correlation methods. Use of this parameter, rather than those based on overall performance, allows trade-off studies to be made within a given performance requirement so that a minimum noise configuration may be designed or selected.

Wright, T.

1982-08-01

296

Clean wing airframe noise modeling for multidisciplinary design and optimization  

NASA Astrophysics Data System (ADS)

A new noise metric has been developed that may be used for optimization problems involving aerodynamic noise from a clean wing. The modeling approach uses a classical trailing edge noise theory as the starting point. The final form of the noise metric includes characteristic velocity and length scales that are obtained from three-dimensional, steady, RANS simulations with a two equation k-o turbulence model. The noise metric is not the absolute value of the noise intensity, but an accurate relative noise measure as shown in the validation studies. One of the unique features of the new noise metric is the modeling of the length scale, which is directly related to the turbulent structure of the flow at the trailing edge. The proposed noise metric model has been formulated so that it can capture the effect of different design variables on the clean wing airframe noise such as the aircraft speed, lift coefficient, and wing geometry. It can also capture three dimensional effects which become important at high lift coefficients, since the characteristic velocity and the length scales are allowed to vary along the span of the wing. Noise metric validation was performed with seven test cases that were selected from a two-dimensional NACA 0012 experimental database. The agreement between the experiment and the predictions obtained with the new noise metric was very good at various speeds, angles of attack, and Reynolds Number, which showed that the noise metric is capable of capturing the variations in the trailing edge noise as a relative noise measure when different flow conditions and parameters are changed. Parametric studies were performed to investigate the effect of different design variables on the noise metric. Two-dimensional parametric studies were done using two symmetric NACA four-digit airfoils (NACA 0012 and NACA 0009) and two supercritical (SC(2)-0710 and SC(2)-0714) airfoils. The three-dimensional studies were performed with two versions of a conventional transport wing at realistic approach conditions. The twist distribution of the baseline wing was changed to obtain a modified wing which was used to investigate the effect of the twist on the trailing edge noise. An example study with NACA 0012 and NACA 0009 airfoils demonstrated a reduction in the trailing edge noise by decreasing the thickness ratio and the lift coefficient, while increasing the chord length to keep the same lift at a constant speed. Both two- and three-dimensional studies demonstrated that the trailing edge noise remains almost constant at low lift coefficients and gets larger at higher lift values. The increase in the noise metric can be dramatic when there is separation on the wing. Three-dimensional effects observed in the wing cases indicate the importance of calculating the noise metric with a characteristic velocity and length scale that vary along the span. The twist change does not have a significant effect on the noise at low lift coefficients, however it may give significant noise reduction at higher lift values. The results obtained in this study show the importance of the lift coefficient, CL, on the airframe noise of a clean wing and favors having a larger wing area to reduce the CL for minimizing the noise. The results also point to the fact that the noise reduction studies should be performed in a multidisciplinary design and optimization framework, since many of the parameters that change the trailing edge noise also affect the other aircraft design requirements. It's hoped that the noise metric developed here can aid in such multidisciplinary design and optimization studies.

Hosder, Serhat

297

Application of Wake Characteristics to Prediction of Broadband Noise of a Multiblade Fan  

NASA Astrophysics Data System (ADS)

In this study, the wake characteristics of an arc blade were measured by the wind tunnel experiment; the characteristics were defined as the width of the wake, diameter of the vortex, ratio of the vortex scale, and the local lift. The influence of the angle of attack on the aerodynamic noise of the blade was quantitatively predicted by using these characteristics. It was clarified experimentally that the sound pressure of the aerodynamic noise becomes small since the gradient of the differential of the lift fluctuation was reduced according to the increase of the angle of attack. The wake characteristics were applied to the prediction of the broadband noise generated from a multiblade fan; the fan noise level distribution was estimated with high accuracy to be in the range from 1000-3000 Hz and was used to analyze the broadband noise of the fan. From the analysis of the fan noise level, it was found that the difference in the relative velocity caused by the biased internal flow was related to the noise levels.

Sasaki, Soichi; Hayashi, Hidechito

298

Deep Ocean Ambient Noise.  

National Technical Information Service (NTIS)

The objective of this report is to provide information on deep ocean ambient noise which can be used in sonar system design and analysis. Guidelines are given for estimating wind-generated noise, oceanic ship traffic noise, biological noise levels, and th...

A. A. Barrios

1967-01-01

299

Noise predictive turbo systems  

Microsoft Academic Search

Iterative decoding has been widely studied for memoryless white Gaussian noise channels. For nonideal channels, e.g., correlated noise channels, iterative decoding combined with iterative noise estimation may improve the performance of the detector. The basic idea is to exploit the decoding results of the previous iteration to estimate the correlated noise so that better decoding results ran be obtained. Furthermore,

Yunxiang Wu; J. R. Cruz

2001-01-01

300

Noise in Synchronized Oscillators  

Microsoft Academic Search

Noise in synchronized oscillators is analyzed using a simple oscillator model. It is shown that the FM noise can be considerably improved by synchronization while the AM noise degrades slightly. It is also shown how the noise spectrum becomes unsymmetrical with respect to the synchronizing freqnency when it differs from the free-running frequency.

K. Kurokawa

1968-01-01

301

Aerodynamic performance of vertical and horizontal axis wind turbines  

NASA Astrophysics Data System (ADS)

The aerodynamic performance of vertical and horizontal axis wind turbines is investigated, and comparison of data of the 17-m Darrieus VAWT with the 60.7-m Mod-1 HAWT and 37.8-m Mod-0A HAWT is discussed. It is concluded that the maximum average measured power coefficients of the VAWT are about 0%-15% higher than those of the HAWTs. It is suggested that vertical wind shear may have lowered the Mod-1 HAWT aerodynamic performance, but, the magnitude of this effect could not be evaluated. It is included that generalizations which refer to the Darrieus VAWT as aerodynamically less efficient than the HAWT should be used carefully.

Maydew, R. C.; Klimas, P. C.

1981-06-01

302

The unsteady aerodynamics of a first stage stator vane row  

NASA Astrophysics Data System (ADS)

The fundamental unsteady aerodynamics on a vane row of an axial flow research compressor stage are experimentally investigated, demonstrating the effects of airfoil camber and steady loading. In particular, the rotor wake generated unsteady surface pressure distributions on the first stage vane row are quantified over a range of operating conditions. These cambered airfoil unsteady data are correlated with predictions from a flat plate cascade inviscid flow model. At the design point, the unsteady pressure difference coefficient data exhibit good correlation with the nonseparated predictions, with the aerodynamic phase lag data exhibiting fair trendwise correlation. The quantitative phase lag differences are associated with the camber of the airfoil. An aft suction surface flow separation region is indicated by the steady state surface static pressure data as the aerodynamic loading is increased. This separation affects the increased incidence angle unsteady pressure data.

Capece, V. R.; Fleeter, S.

1986-03-01

303

Image noise severity metric  

NASA Astrophysics Data System (ADS)

We propose in this paper an image noise severity measurement method that correlates well with human's quality perception on the presence of noise in images. In our approach, a 32x32 pixels mask is used to compute the differences between the original and noise-degraded images in terms of the statistical means and outlier values. These differences are formulated and then compared to the quality scores from the subjective evaluations. The degraded images were distorted by two common types of random noise for images - Gaussian white noise and impulse noise. Experiment results showed that this approach obtained higher correlation compare to classical Peak Signal to Noise Ratio (PSNR) method.

Bong, David B. L.; Khoo, B. E.

2012-04-01

304

Integrated CFD (Computational Fluid Dynamics) Experimental Analysis of Aerodynamic Forces and Moments.  

National Technical Information Service (NTIS)

Aerodynamic analysis using computational fluid dynamics (CFD) is most fruitful when it is combined with a thorough program of wind tunnel testing. The understanding of aerodynamic phenomena is enhanced by the synergistic use of both analysis methods. A te...

J. E. Melton D. D. Robertson S. A. Moyer

1989-01-01

305

Unpowered Aerodynamic Characteristics of a 15-Percent Scale Model of a Twin-Engine Commuter Aircraft.  

National Technical Information Service (NTIS)

An experimental investigation was conducted in the Ames 12-Foot Pressure Wind Tunnel to determine the unpowered aerodynamic characteristics of a 15-percent-scale model of a twin-engine commuter aircraft. Model longitudinal aerodynamic characteristics were...

D. G. Morgan T. L. Galloway B. J. Gambucci

1981-01-01

306

System Dynamic Analysis of a Wind Tunnel Model with Applications to Improve Aerodynamic Data Quality.  

National Technical Information Service (NTIS)

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, ...

R. D. Buehrle

1997-01-01

307

Aerodynamics of intermittent bounds in flying birds  

NASA Astrophysics Data System (ADS)

Flap-bounding is a common flight style in small birds in which flapping phases alternate with flexed-wing bounds. Body lift is predicted to be essential to making this flight style an aerodynamically attractive flight strategy. To elucidate the contributions of the body and tail to lift and drag during the flexed-wing bound phase, we used particle image velocimetry (PIV) and measured properties of the wake of zebra finch ( Taeniopygia guttata, N = 5), flying at 6-10 m s-1 in a variable speed wind tunnel as well as flow around taxidermically prepared specimens ( N = 4) mounted on a sting instrumented with force transducers. For the specimens, we varied air velocity from 2 to 12 m s-1 and body angle from -15° to 50°. The wake of bounding birds and mounted specimens consisted of a pair of counter-rotating vortices shed into the wake from the tail, with induced downwash in the sagittal plane and upwash in parasagittal planes lateral to the bird. This wake structure was present even when the tail was entirely removed. We observed good agreement between force measures derived from PIV and force transducers over the range of body angles typically used by zebra finch during forward flight. Body lift:drag ( L: D) ratios averaged 1.4 in live birds and varied between 1 and 1.5 in specimens at body angles from 10° to 30°. Peak ( L: D) ratio was the same in live birds and specimens (1.5) and was exhibited in specimens at body angles of 15° or 20°, consistent with the lower end of body angles utilized during bounds. Increasing flight velocity in live birds caused a decrease in C L and C D from maximum values of 1.19 and 0.95 during flight at 6 m s-1 to minimum values of 0.70 and 0.54 during flight at 10 m s-1. Consistent with delta-wing theory as applied to birds with a graduated-tail shape, trimming the tail to 0 and 50% of normal length reduced L: D ratios and extending tail length to 150% of normal increased L: D ratio. As downward induced velocity is present in the sagittal plane during upstroke of flapping flight, we hypothesize that body lift is produced during flapping phases. Future efforts to model the mechanics of intermittent flight should take into account that flap-bounding birds may support up to 20% of their weight even with their wings fully flexed.

Tobalske, Bret W.; Hearn, Jason W. D.; Warrick, Douglas R.

2009-05-01

308

Aerodynamics of intermittent bounds in flying birds  

NASA Astrophysics Data System (ADS)

Flap-bounding is a common flight style in small birds in which flapping phases alternate with flexed-wing bounds. Body lift is predicted to be essential to making this flight style an aerodynamically attractive flight strategy. To elucidate the contributions of the body and tail to lift and drag during the flexed-wing bound phase, we used particle image velocimetry (PIV) and measured properties of the wake of zebra finch (Taeniopygia guttata, N = 5), flying at 6-10 m s- 1 in a variable speed wind tunnel as well as flow around taxidermically prepared specimens (N = 4) mounted on a sting instrumented with force transducers. For the specimens, we varied air velocity from 2 to 12 m s- 1 and body angle from -15? to 50?. The wake of bounding birds and mounted specimens consisted of a pair of counterrotating vortices shed into the wake from the tail, with induced downwash in the sagittal plane and upwash in parasagittal planes lateral to the bird. This wake structure was present even when the tail was entirely removed. We observed good agreement between force measures derived from PIV and force transducers over the range of body angles typically used by zebra finch during forward flight. Body lift:drag (L:D) ratios averaged 1.4 in live birds and varied between 1 and 1.5 in specimens at body angles from 10? to 30?. Peak (L:D) ratio was the same in live birds and specimens (1.5) and was exhibited in specimens at body angles of 15? or 20?, consistent with the lower end of body angles utilized during bounds. Increasing flight velocity in live birds caused a decrease in CL and CD from maximum values of 1.19 and 0.95 during flight at 6 m s- 1 to minimum values of 0.70 and 0.54 during flight at 10 m s- 1. Consistent with delta-wing theory as applied to birds with a graduated-tail shape, trimming the tail to 0 and 50% of normal length reduced L:D ratios and extending tail length to 150% of normal increased L:D ratio. As downward induced velocity is present in the sagittal plane during upstroke of flapping flight, we hypothesize that body lift is produced during flapping phases. Future efforts to model the mechanics of intermittent flight should take into account that flap-bounding birds may support up to 20% of their weight even with their wings fully flexed.

Tobalske, Bret W.; Hearn, Jason W. D.; Warrick, Douglas R.

309

Rapporteur's report, session 2: Other sources, including maintenance noise, freightyards, locomotive noise, station noise, etc  

Microsoft Academic Search

The major sources of noise, excluding through train noise, were identified as locomotive noise, maintenance noise and freight marshalling noise. The biggest single problem appeared, from social survey data in the U.K., to be railway maintenance noise, which was difficult to control effectively. Locomotive noise was also a problem and it should be productive to diagnose the sources of noise

J. G. Walker

1979-01-01

310

Aerodynamic development of a lifting body launch vehicle  

SciTech Connect

The Lockheed Martin Reusable Launch Vehicle (RLV) and X-33 demonstrator vehicle incorporate a lifting body aerodynamic design. This design originated from the X-24, HL-20 and ACRV lifting body database. It evolved rapidly through successive wind tunnel tests using stereolithography generated plastic models and rapid data acquisition and analysis. The culmination of this work is a configuration that is close to meeting a goal of at least neutral stability about all axes throughout the operating Mach spectrum. The development process and aerodynamic evolution are described. {copyright} {ital 1997 American Institute of Physics.}

Reaser, J.S. [Lockheed Martin Skunk Works 1011 Lockheed Way Palmdale, California93599 (United States)

1997-01-01

311

Improved Aerodynamic Influence Coefficients for Dynamic Aeroelastic Analyses  

NASA Astrophysics Data System (ADS)

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's evaluation, performed with CFD data calculated by the DLM, is essential to find the natural modes which are most influential on the flutter solutions of the different configurations. Finally, Euler and Navier-Stokes results are used to obtain improved flutter solutions for a subsonic case at Mach 0.7 and dispositions are made to accomplish the same exercise for transonic speeds.

Gratton, Patrice

312

Aerodynamic-structural model of offwind yacht sails  

NASA Astrophysics Data System (ADS)

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 computational force predictions were fair at both wind angles examined. Force predictions were much improved in the overtrimmed setting when the sail was highly stalled and more stable. The same trends in force prediction were seen when employing the aerodynamic-structural model. Predictions were good to fair in the baseline setting but improved in the overtrimmed configuration.

Mairs, Christopher M.

313

Aerodynamics of Dragonfly in Hover: Force measurements and PIV results  

NASA Astrophysics Data System (ADS)

We useda pair of dynamically scaled robotic dragonfly model wings to investigate the aerodynamic effects of wing-wing interaction in dragonflies. We follow the wing kinematics of real dragonflies in hover, while systematically varied the phase difference between the forewing and hindwing. Instantaneous aerodynamic forces and torques were measured on both wings, while flow visualization and PIV results were obtained. The results show that, in hovering flight, wing-wing interaction causes force reduction for both wings at most of the phase angle differences except around 0 degree (when the wings are beating in-phase).

Deng, Xinyan; Hu, Zheng

2009-11-01

314

VALIDATION OF METHODOLOGY FOR ESTIMATING AIRCRAFT UNSTEADY AERODYNAMIC PARAMETERS FROM DYNAMIC WIND TUNNEL TESTS  

Microsoft Academic Search

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

Patrick C. Murphy; Vladislav Klein

315

Identification of aerodynamic coefficients of a kinetic energy projectile from flight data  

Microsoft Academic Search

A technique to identify the aerodynamic coefficients of a kinetic energy (KE) projectile using flight data is proposed. Generally speaking, the flight of a projectile is governed by a six-degree-of-freedom model in which eight aerodynamic coefficients also play a part. We will firstly show that only three of the aerodynamic coefficients have an influence on the measurable quantities (velocity, roll

Hélène Demailly; Franck Delvare; Christophe Grignon; Settie Heddadj; Patrice Bailly

2012-01-01

316

DEVELOPMENT OF A DISCRETE-TIME AERODYNAMIC MODEL FOR CFD BASED AEROELASTIC ANALYSIS  

Microsoft Academic Search

System identification is used to develop an accurate and computationally efficient discrete-time aerodynamic model of a three-dimensional, unsteady CFD solution. This aerodynamic model is then used in place of the unsteady CFD solution in a coupled aeroelastic analysis resulting in a substantial savings in computational time. The methodology has the advantage of producing an explicit mathematical relationship for the aerodynamic

Timothy J. Cowan; Andrew S. Arena; Kajal K. Gupta

317

Extracting micro air vehicles aerodynamic forces and coefficients in free flight using visual motion tracking techniques  

Microsoft Academic Search

This paper describes a methodology to extract aerial vehicles' aerodynamic characteristics from visually tracked trajectory data. The technique is being developed to study the aerodynamics of centimeter-scale aircraft and develop flight simulation models. Centimeter-scale aircraft remains a largely unstudied domain of aerodynamics, for which traditional techniques like wind tunnels and computational fluid dynamics have not yet been fully adapted and

B. F. Mettler

2010-01-01

318

ROBUST AERODYNAMIC AIRFOIL DESIGN OPTIMIZATION AGAINST WIND VARIATIONS FOR MARS EXPLORATORY AIRPLANE  

Microsoft Academic Search

Robust aerodynamic airfoil design optimizations of Mars exploratory airplane against wind variations have been carried out by using DFMOSS coupled with the CFD simula- tion. The present robust optimizations successfully found the airfoil designs with robust aerodynamic performances against wind variations. Obtained airfoil design information about the optimality and the robustness of aerodynamic performances indicated that an airfoil with smaller

Koji Shimoyama; Akira Oyama; Kozo Fujii

319

Wheel-rail noise: impact, random, corrugation and tonal noise  

Microsoft Academic Search

A small survey will be given of wheel-rail contact noise. Distinction is made between impact noise, random noise (amorphous noise), corrugation (rattling noise) and tonal noise (curve shrieking). An account will be given of the causes of the various types of noise, and also of what can be done to diminish them.

J. J. Kalker; F. Périard

1996-01-01

320

Aviation noise effects  

NASA Astrophysics Data System (ADS)

This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carried out under FAA and other Federal funding over the past two decades. Efforts have been made to present the critical findings and conclusions of pertinent research, providing, when possible, a bottom line conclusion, criterion or perspective. Issues related to aviation noise are highlighted, and current policy is presented. Specific topic addressed include: annoyance; Hearing and hearing loss; noise metrics; human response to noise; speech interference; sleep interference; non-auditory health effects of noise; effects of noise on wild and domesticated animals; low frequency acoustical energy; impulsive noise; time of day weightings; noise contours; land use compatibility; and real estate values. This document is designed for a variety of users, from the individual completely unfamiliar with aviation noise to experts in the field.

Newman, J. S.; Beattie, K. R.

1985-03-01

321

Analysis of rotor wake aerodynamics during maneuvering flight using a free-vortex wake methodology  

NASA Astrophysics Data System (ADS)

The problem of helicopter rotor wake aerodynamics during maneuvering flight conditions was analyzed using a time-accurate, free-vortex wake methodology. The free-vortex method consists of a Lagrangian representation of the rotor flow field using vortex elements, where the evolution of the flow field is simulated by tracking the free motion of these vortex elements and calculating their induced velocity field. Traditionally, free-vortex methods are inviscid, incompressible models, but in the present approach the viscous effects are incorporated using a viscous splitting method where the viscous and inviscid terms are modeled as successive sub-processes. The rotor aerodynamics and rigid blade flapping dynamics are closely coupled with the wake model and solved for in a consistent manner using the same numerical scheme. Validations of the methodology with experimental data were performed to study the wake response to perturbations in collective and cyclic pitch inputs. The numerical simulations captured all the essential wake dynamics observed in flow visualization. The predictions of the transient inflow and airloads response were found to be in excellent agreement with the available experimental measurements. It was observed that the rotor wake was extremely sensitive to perturbations in collective and cyclic blade pitch inputs. The characteristic wake response was found to be the bundling of the wake vorticity into a vortex ring structure. The evolution, convection and subsequent breakdown of this bundled ring of tip-vortices was found to be highly nonlinear, and occurs with a temporal lag. The nonlinear induced velocity field associated with unsteady wake evolution can cause considerable fluctuations in the rotor airloads time-history if the bundled tip-vortex structure comes into close proximity to the rotor blades. Furthermore, the interaction of these tip-vortices with the blades results in steep gradients in the rotor airloads across the rotor disk, thereby contributing to impulsive rotor noise. Several free-flight maneuver simulations were analyzed to gain better insight into the unsteady, nonlinear wake development under high-rate, large-amplitude maneuvers such as roll to starboard or port, roll reversals, and the quickstop maneuver. It is shown that the rotor wake response in almost all maneuvering flight conditions is highly nonlinear and emphasizes the need to accurately predict the transient wake aerodynamics to obtain accurate estimates of the unsteady rotor airloads and the resulting rotor acoustics.

Ananthan, Shreyas

322

Impact noise from railroads  

NASA Astrophysics Data System (ADS)

Human response to impact noise, generated by wheel flats and rail joints of electric trains, was investigated in a laboratory experiment. The loudness of train noise containing impact components was compared with train noise with no impact components. A method of paired comparisons was used to evaluate the loudness of the test sounds. The results indicate that the wheel flat noise increases the loudness of train noise by 3 dB and the rail joint noise increases it by 5 dB (outdoor listening condition) and 7 dB (indoor listening conditions) at the same equivalent sound energy level.

Kaku, J.; Yamashita, M.

1988-01-01

323

Optimization of Flight Test Maneuvers for Aerodynamic Derivatives Inverse Problem  

Microsoft Academic Search

1. Abstract This work deals with the application of optimization techniques to the determination of aircraft light test input maneuvers for aircraft model identification and aerodynamic parameter estimation. The optimum flight test maneuvers are necessary to increase the efficiency of aircraft identification and parameter estimation algorithms, respecting operational restrictions related to flight safety and limits of the assumed mathematical models.

Nei Salis; Brasil Neto; Luiz Carlos; S. Góes; Benedito Carlos; O. Maciel; Elder Moreira Hemerly

324

Identification of Parameters and Model Structure for Missile Aerodynamics  

Microsoft Academic Search

In this paper, current work on the Aerodynamic Coefficient Estimation (ACES) program for guided missiles is reviewed. A fundamental statistical approach to the problem is taken, and recent developments in the identification of model structure are used including: initial comparison of parametric model structures by subset regression using a leaps and bounds algorithm, refined comparison of different parametric model structures

W. E. Larimore; W. M. Lebow; R. K. Mehra

1985-01-01

325

Aerodynamic aspects on recovery of sounding rocket payload  

Microsoft Academic Search

Aerodynamic experiments for the design of a recovery system for a sounding rocket payload included wind tunnel tests of payload models at high angles of attack over Mach numbers ranging from subsonic to supersonic and airdrop tests of payload models. It was shown that (1) the magnitude of the cross-flow proportionality factor used for predicting the payload normal force coefficient

M. Shirouzu; H. Kubota; Y. Shibato

1980-01-01

326

Numerical Analysis on Aerodynamic Forces on Wiper System  

NASA Astrophysics Data System (ADS)

Flow fields of the window wiper at different wiping angles and vehicle speeds have been simulated in this paper. These results suggest that aerodynamic forces change with the wiping angle. The force peak occurs at certain angle. These results can be a reference for the designer to predict the max lift and drag force when design a new wiper.

Yang, Z. G.; Ju, X. M.; Li, Q. L.

2011-09-01

327

ON AERODYNAMIC AND BOUNDARY LAYER RESISTANCES WITHIN DRY DEPOSITION MODELS  

EPA Science Inventory

There have been many empirical parameterizations for the aerodynamic and boundary layer resistances proposed in the literature, e.g. those of the Meyers Multi-Layer Deposition Model (MLM) used with the nation-wide dry deposition network. Many include arbitrary constants or par...

328

Passive flow control by membrane wings for aerodynamic benefit  

NASA Astrophysics Data System (ADS)

The coupling of passive structural response of flexible membranes with the flow over them can significantly alter the aerodynamic characteristic of simple flat-plate wings. The use of flexible wings is common throughout biological flying systems inspiring many engineers to incorporate them into small engineering flying systems. In many of these systems, the motion of the membrane serves to passively alter the flow over the wing potentially resulting in an aerodynamic benefit. In this study, the aerodynamic loads and the flow field for a rigid flat-plate wing are compared to free trailing-edge membrane wings with two different pre-tensions at a chord-based Reynolds number of approximately 50,000. The membrane was silicon rubber with a scalloped free trailing edge. The analysis presented includes load measurements from a sting balance along with velocity fields and membrane deflections from synchronized, time-resolved particle image velocimetry and digital image correlation. The load measurements demonstrate increased aerodynamic efficiency and lift, while the synchronized flow and membrane measurements show how the membrane motion serves to force the flow. This passive flow control introduced by the membranes motion alters the flows development over the wing and into the wake region demonstrating how, at least for lower angles of attack, the membranes motion drives the flow as opposed to the flow driving the membrane motion.

Timpe, Amory; Zhang, Zheng; Hubner, James; Ukeiley, Lawrence

2013-03-01

329

Aerodynamic analysis of a Mars exploration manned capsule  

NASA Astrophysics Data System (ADS)

The paper deals with the aerodynamic analysis of a manned braking system entering the Mars atmosphere, with the aim to support planetary entry system design studies. The capsule configuration is an axisymmetric blunt body close to the Apollo capsule. Several fully three-dimensional Computational Fluid Dynamics analyses have been performed to assess the flowfield environment around the vehicle to address the aerodynamic performance of the entry capsule within mission exploration to Mars. To this end, a wide range of flow conditions including reacting and non-reacting flow, different angles of attack, and Mach numbers have been investigated and compared. Moreover, non-equilibrium effects on the flowfield around the capsule have been also investigated. Results show that real-gas effects, for all the angles of attach considered, increase both the aerodynamic drag and pitching moment, whereas the lift is only slighted affected. Finally, comparison of the results highlights that experimental and CFD aerodynamic findings available for the Apollo capsule in air adequately represent the static coefficients of the capsule in the Mars atmosphere.

Pezzella, Giuseppe; Viviani, Antonio

2011-12-01

330

Laryngeal Aerodynamics Associated with Oral Contraceptive Use: Preliminary Findings  

ERIC Educational Resources Information Center

|The purpose of this study was to examine possible differences in laryngeal aerodynamic measures during connected speech associated with oral contraceptive (OC) use. Eight women taking an OC, and eight others not taking an OC, participated in the study. Three trials of syllable /p[subscript alpha] /repetitions were obtained using a…

Gorham-Rowan, Mary; Fowler, Linda

2009-01-01

331

Integrated modeling of insect flight: From morphology, kinematics to aerodynamics  

NASA Astrophysics Data System (ADS)

An integrated and rigorous model for the simulation of insect flapping flight is addressed. The method is very versatile, easily integrating the modeling of realistic wing body morphology, realistic flapping-wing and body kinematics, and unsteady aerodynamics in insect flight. A morphological model is built based on an effective differential geometric method for reconstructing geometry of and a specific grid generator for the wings and body; and a kinematic model is constructed capable to mimic the realistic wing body kinematics of flapping flight. A fortified FVM-based NS solver for dynamically moving multi-blocked, overset-grid systems is developed and verified to be self-consistent by a variety of benchmark tests; and evaluation of flapping energetics is established on inertial and aerodynamic forces, torques and powers. Validation of this integrated insect dynamic flight simulator is achieved by comparisons of aerodynamic force-production with measurements in terms of the time-varying and mean lift and drag forces. Results for three typical insect hovering flights (hawkmoth, honeybee and fruitfly) over a wide rang of Reynolds numbers from O(102) to O(104) demonstrate its feasibility in accurately modeling and quantitatively evaluating the unsteady aerodynamic mechanisms in insect flapping flight.

Liu, Hao

2009-02-01

332

Aerodynamic Analysis of a General Purpose Tow Target.  

National Technical Information Service (NTIS)

This report presents the aerodynamic characteristics of a proposed aerial tow target configured to meet the general purpose tow target requirements of the Navy Standard Tow Target System. The General Purpose Tow Target will serve as a target for missile a...

J. B. Smith

1974-01-01

333

Aerodynamic Analysis of a Profile Fighter Tow Target.  

National Technical Information Service (NTIS)

This report presents the aerodynamic characteristics of a proposed aerial tow target configured to meet the requirements of the Navy Standard Tow Target System for a large gunnery target. The Profile Fighter Tow Target will be both size and performance re...

J. B. Smith

1974-01-01

334

Unsteady Aerodynamic Flow Control of a Suspended Axisymmetric Moving Platform  

NASA Astrophysics Data System (ADS)

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

Lambert, Thomas; Vukasinovic, Bojan; Glezer, Ari

2011-11-01

335

Aerodynamic design optimization using sensitivity analysis and computational fluid dynamics  

NASA Astrophysics Data System (ADS)

An efficient aerodynamic shape optimization method based on a computational fluid dynamics/sensitivity analysis algorithm has been developed which determines automatically the geometrical definition of an optimal surface starting from any initial arbitrary geometry. This method is not limited to any number of design variables or to any class of surfaces for shape definition.

Baysal, Oktay; Eleshaky, Mohamad E.

1992-01-01

336

Aerodynamic design optimization using sensitivity analysis and computational fluid dynamics  

Microsoft Academic Search

An efficient aerodynamic shape optimization method based on a computational fluid dynamics\\/sensitivity analysis algorithm has been developed which determines automatically the geometrical definition of an optimal surface starting from any initial arbitrary geometry. This method is not limited to any number of design variables or to any class of surfaces for shape definition.

Oktay Baysal; Mohamad E. Eleshaky

1992-01-01

337

Aerodynamic Drag and Drag Reduction: Energy and Energy Savings (Invited).  

National Technical Information Service (NTIS)

An assessment of the role of fluid dynamic resistance and/or aerodynamic drag and the relationship to energy use in the United States is presented. Existing data indicates that up to 25% of the total energy consumed in the United States is used to overcom...

R. M. Wood

2003-01-01

338

Low Speed Aerodynamics of the X-38 CRV.  

National Technical Information Service (NTIS)

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 a...

N. M. Komerath R. Funk R. G. Ames R. Mahalingam C. Matos

1998-01-01

339

Unsteady Free-Wake Viscous Aerodynamic Analysis of Helicopter Rotors.  

National Technical Information Service (NTIS)

The report contains the results for research on unsteady free-wake viscous aerodynamic analysis of helicopter rotors. The effort may be divided into three general areas. The first deals with further developments of the zeroth-order potential-flow analysis...

L. Morino M. Downey S. Sipcic

1989-01-01

340

Proper Orthogonal Decomposition Extensions For Parametric Applications in Transonic Aerodynamics  

Microsoft Academic Search

Two extensions to the proper orthogonal decom- position (POD) technique are considered for steady aerodynamic applications. The first is to couple the POD approach with a cubic spline interpolation pro- cedure in order to develop fast, low-order models that accurately capture the variation in parameters, such as the angle of attack or inflow Mach number. The second extension is a

T. Bui-Thanh; M. Damodarany

341

Mesh Modification Strategy for Aerodynamic Design through Evolution  

Microsoft Academic Search

In this work a mesh deformation strategy for an aerodynamic simulator used in an automatic design environment is presented. This strategy allows creating different alternatives within an evolutionary design process by following a low computational cost procedure. The mesh used to evaluate de fitness of each alternative in a computational fluid dynamic (CFD) solver doesn't need to bet created for

V. Díaz Casás; F. Lopez Peña; R. J. Duro

2007-01-01

342

Aerodynamic and aeroelastic analysis of bundled cables by numerical simulation  

Microsoft Academic Search

A numerical model for the aerodynamic and aeroelastic analysis of bundled cables, commonly used in energy transmission lines, is presented in this work. The bundles were idealized by a sectional model representing the section at the mid span between two supporting towers. A slightly compressible viscous fluid was considered and the two-dimensional flow was analyzed using a two-step explicit method

A. L. Braun; A. M. Awruch

2005-01-01

343

Review of CFD for wind-turbine wake aerodynamics  

Microsoft Academic Search

This article reviews the state of the art of the numerical calculation of wind-turbine wake aerodynamics. Different CFD techniques for modeling the rotor and the wake are discussed. Regarding rotor modeling, recent advances in the generalized actuator approach and the direct model are discussed, as far as it attributes to the wake description. For the wake, the focus is on

B. Sanderse; Pijl van der S. P; B. Koren

2010-01-01

344

Aerodynamic Optimization of a Solar - Bio Diesel Hybrid Vehicle  

Microsoft Academic Search

Energy efficiency is the most critical aspect for a successful solar powered automobile and much can be gained from the reduction of aer odynamic drag on such a vehicle. Yet, for a solar car to be practical to the everyday driver, it has to be ergonomically feasible, financially sensible, and aesthetically pleasing. This research compares aerodynamic drag calculations produced by

Neal A. Allgood

345

Aerodynamic Characteristics of Fan-Jet STOL Aircraft.  

National Technical Information Service (NTIS)

Research on Fan-Jet STOL aircraft was initiated by NAL in 1975 as a wind-tunnel-based program aimed at the design study of experimental STOL aircraft. Aerodynamic characteristics of the Augmentor Wing type model and the Upper Surface Blowing type models a...

N. Inumaru H. Takahashi K. Hirosue N. Toda N. Kuwano

1983-01-01

346

Prediction of Transient Aerodynamic Inputs on Passenger Cars,  

National Technical Information Service (NTIS)

In order to investigate cross-wind stability, it is required to understand the transient aerodynamic inputs acting on the vehicle body. The paper describes the method to estimate the transient inputs by measuring the pressure fluctuations on the body surf...

H. Takada I. Kohri K. Harigane

1988-01-01

347

Tracheal and central bronchial aerodynamics using virtual bronchoscopy  

NASA Astrophysics Data System (ADS)

Virtual bronchoscopy reconstructions of the airway noninvasively provide useful morphologic information of structural abnormalities such as stenoses and masses. In this paper, we show how virtual bronchoscopy can be used to perform aerodynamic calculations in anatomically realistic models. Pressure and flow patterns in a human airway were computed noninvasively. These showed decreased pressure and increased shear stress in the region of a stenosis.

Summers, Ronald M.; Cebral, Juan R.

2001-05-01

348

Aerodynamic Design of First Stage Turbines for Small Aero Engines.  

National Technical Information Service (NTIS)

Minimization of tip leakeage and limit loading are discussed. Results obtained with a 4.5:1 pressure ratio turbine having an aerodynamic loading of 2.11 indicate that very efficient turbines can be designed in loading and pressure ratio regimes of interes...

U. Okapuu

1987-01-01

349

In-Flight Aerodynamic Measurements of an Iced Horizontal Tailplane.  

National Technical Information Service (NTIS)

The effects of tailplane icing on aircraft dynamics and tailplane aerodynamics were investigated using, NASA's modified DHC-6 Twin Otter icing research aircraft. This flight program was a major element of the four-year NASA/FAA research program that also ...

T. P. Ratvasky J. F. VanZante

1999-01-01

350

Aerodynamic forces of revolving hummingbird wings and wing models  

Microsoft Academic Search

A central challenge to the study of animal aerodynamics has been the measurement offerees generated by flapping wings. Relative to wings of other birds, hummingbird wings are of particular interest in that the smaller species operate in more viscous regimes (5000

Douglas L. Altshuler; Robert Dudley; Charles P. Ellington

2004-01-01

351

Aerodynamic analysis of a Mars exploration manned capsule  

Microsoft Academic Search

The paper deals with the aerodynamic analysis of a manned braking system entering the Mars atmosphere, with the aim to support planetary entry system design studies. The capsule configuration is an axisymmetric blunt body close to the Apollo capsule. Several fully three-dimensional Computational Fluid Dynamics analyses have been performed to assess the flowfield environment around the vehicle to address the

Giuseppe Pezzella; Antonio Viviani

2011-01-01

352

Aerodynamic calculational methods for curved-blade Darrieus VAWT WECS  

Microsoft Academic Search

Calculation of aerodynamic performance and load distributions for curved-blade wind turbines is discussed. Double multiple stream tube theory, and the uncertainties that remain in further developing adequate methods are considered. The lack of relevant airfoil data at high Reynolds numbers and high angles of attack, and doubts concerning the accuracy of models of dynamic stall are underlined. Wind tunnel tests

R. J. Templin

1985-01-01

353

Aerodynamic Characteristics of Telescopic Aerospikes with Multiple-Row-Disk  

Microsoft Academic Search

This paper reports experimental studies on telescopic aerospikes with multiple disks. The telescopic aerospike is useful as an aerodynamic control device; however, changing its length causes a buzz phenomenon, which many researchers have reported. The occurrence of buzzing might be critical to the vehicle because it brings about severe pressure oscillations on the surface. Disks on the shaft produce stable

Hiroaki Kobayashi; Yusuke Maru; Tetsuya Sato

2007-01-01

354

Take-off and Aerodynamic Characteristics of a Taketombo  

Microsoft Academic Search

The taketombo is a traditional flying toy of Japan transmitted from old times. Since the taketombo is made of a bamboo, it is also called the bamboo dragonfly. The taketombo consists of two parts, the wing and the shaft. The wing generates the lift, and the shaft is for giving rotation to the taketombo. However, the take-off and aerodynamic characteristics

Kunio Yasuda

2008-01-01

355

Improvement in Aerodynamic Characteristics of a Paraglider Wing Canopy  

Microsoft Academic Search

To determine the parameters which can improve the overall performance of a paraglider wing canopy, we have been investigating the fundamental aerodynamic characteristics of an inflatable cell model which is designed to represent the dynamic behaviors of each cell comprising the wing canopy. This paper describes the results of a series of wind tunnel experiments. It is shown that significant

Mohammad Mashud; Akira Umemura

2006-01-01

356

Aerodynamic Characteristics of NACA4402 in Low Reynolds Number Flows  

Microsoft Academic Search

Gas flow over a two-dimensional airfoil at very low Reynolds number is investigated in order to understand basic aerodynamic characteristics related to design of Micro Air Vehicle (MAV) for planetary exploration. Before the investigations, verification was conducted for the current numerical approach, which are commonly used and validated for high Reynolds number flow analysis, showing good applicability for low Reynolds

Ryoji Takaki

2006-01-01

357

Single annular combustor: Experimental investigations of aerodynamics, dynamics and emissions  

Microsoft Academic Search

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

Bassam Sabry Mohammad

2010-01-01

358

Aerodynamic performance of thin wings at low Reynolds numbers  

Microsoft Academic Search

Purpose – This study seeks to explore the aerodynamic performance of wings with different shapes at low Reynolds numbers. Design\\/methodology\\/approach – The airfoils of these wings are made from aluminum plates, and the maximum cord length and wingspan are 15 cm. Wings A to D are plates with 6 percent Gottingen camber but different wing planforms. The forward-half sections of

J. L. Lin; C. Y. Wei; C. Y. Lin

2007-01-01

359

Prediction of Unsteady Aerodynamic Coefficients at High Angles of Attack.  

National Technical Information Service (NTIS)

The nonlinear indicial response method is used to model the unsteady aerodynamic coefficients in the low speed longitudinal oscillatory wind tunnel test data of the 0.1 scale model of the F-16XL aircraft. Exponential functions are used to approximate the ...

B. N. Pamadi P. C. Murphy V. Klein J. M. Brandon

2001-01-01

360

Aerodynamic Drag Reduction Apparatus For Wheeled Vehicles In Ground Effect  

DOEpatents

An apparatus for reducing the aerodynamic drag of a wheeled vehicle in a flowstream, the vehicle having a vehicle body and a wheel assembly supporting the vehicle body. The apparatus includes a baffle assembly adapted to be positioned upstream of the wheel assembly for deflecting airflow away from the wheel assembly so as to reduce the incident pressure on the wheel assembly.

Ortega, Jason M. (Pacifica, CA); Salari, Kambiz (Livermore, CA)

2005-12-13

361

The efficiency of aerodynamic force production in Drosophila.  

PubMed

Total efficiency of aerodynamic force production in insect flight depends on both the efficiency with which flight muscles turn metabolic energy into muscle mechanical power and the efficiency with which this power is converted into aerodynamic flight force by the flapping wings. Total efficiency has been estimated in tethered flying fruit flies Drosophila by modulating their power expenditures in a virtual reality flight simulator while simultaneously measuring stroke kinematics, locomotor performance and metabolic costs. During flight, muscle efficiency increases with increasing flight force production, whereas aerodynamic efficiency of lift production decreases with increasing forces. As a consequence of these opposite trends, total flight efficiency in Drosophila remains approximately constant within the kinematic working range of the flight motor. Total efficiency is broadly independent of different profile power estimates and typically amounts to 2-3%. The animal achieves maximum total efficiency near hovering flight conditions, when the beating wings produce flight forces that are equal to the body weight of the insect. It remains uncertain whether this small advantage in total efficiency during hovering flight was shaped by evolutionary factors or results from functional constraints on both the production of mechanical power by the indirect flight muscles and the unsteady aerodynamic mechanisms in flapping flight. PMID:11733168

Lehmann, F O

2001-12-01

362

Introduction to generalized functions with applications in aerodynamics and aeroacoustics  

Microsoft Academic Search

Generalized functions have many applications in science and engineering. One useful aspect is that discontinuous functions can be handled as easily as continuous or differentiable functions and provide a powerful tool in formulating and solving many problems of aerodynamics and acoustics. Furthermore, generalized function theory elucidates and unifies many ad hoc mathematical approaches used by engineers and scientists. We define

F. Farassat

1994-01-01

363

Aerodynamic Characteristics of the Parachute Stabilized a-21 Cargo Container.  

National Technical Information Service (NTIS)

A study was conducted to determine the basic aerodynamic coefficients of the aerial delivery system of the A-21 cargo container and the optimum parachute-riser configurations for its stabilization during the high velocity stage of the delivery. A method w...

S. K. Ibrahim

1965-01-01

364

Experimental aerodynamic characteristics of missiles with square cross sections  

Microsoft Academic Search

A series of quantitative and qualitative tests were conducted to expand the aerodynamic data base of square cross-section missiles. Quantitative tests included measuring forces and moments acting on square missiles, and measuring flowfield pressures on the leeward side of square missiles at various configurations and orientations in a subsonic wind tunnel. Force and moment data is presented showing the effects

G. J. Zollars; R. T. Yechout; D. C. Daniel; L. E. Lijewski

1983-01-01

365

Some aerodynamic aspects of engine secondary air systems  

Microsoft Academic Search

Internal cooling air systems of turbomachines contain various fluid flow components, i.e. rotating holes, tapping configurations, coverplates, labyrinth seals etc., for which only the basic aerodynamics are known. Numerical calculations for these elements are carried out and compared with test results showing fair agreement in general. For most of the components of internal air systems there is a serious lack

H. Zimmermann

1989-01-01

366

Bat wing structures important for aerodynamics and rigidity (Mammalia, chiroptera)  

Microsoft Academic Search

From comparisons between bat wing structures and aerofoils and high-lift devices with known aerodynamic data, from the aeronautical literature, deductions are made regarding the function of some bat wing structures. Special arrangements in the hand wing add to rigidity and reduce the demands for powerful muscles and thick digits, thereby reducing the mass of the wing.1.The anterior part of the

Ulla M. Norberg

1972-01-01

367

Aerodynamic isotope separation processes for uranium enrichment: process requirements  

Microsoft Academic Search

The pressing need for enriched uranium to fuel nuclear power reactors, requiring that as many as ten large uranium isotope separation plants be built during the next twenty years, has inspired an increase of interest in isotope separation processes for uranium enrichment. Aerodynamic isotope separation processes have been prominently mentioned along with the gas centrifuge process and the laser isotope

Malling; G. F. Von Halle

1976-01-01

368

Fine particle counting with aerodynamic particle focusing and corona charging  

Microsoft Academic Search

The conceptual design and evaluation of a fine particle sizing and counting instrument are introduced in this paper. A corresponding laboratory prototype was developed by coupling aerodynamic particle focusing with corona charging techniques that could detect particle sizes down to 25nm in diameter. Comparison between the prototype and a condensation particle counter (CPC) using identical monodisperse particles showed that the

Z. C. Tan; A. S. Wexler

2007-01-01

369

Historical view of long-span bridge aerodynamics  

Microsoft Academic Search

Some features of bridge aerodynamics of wind engineering are reviewed at this time, in view of the collapse of the Tacoma Narrows Bridge and also to celebrate Professor Alan G. Davenport's 40 years of contribution to the field. Primary highlighted topics are: description of motion-dependent forces for flutter instability, presentation of gust responses caused by turbulent winds and suppression problems

Toshio Miyata

2003-01-01

370

Economics of Railroad Automobile Rack Car Aerodynamic Drag.  

National Technical Information Service (NTIS)

A program was established to evaluate in detail the causes of the excessive aerodynamic drag of automobile rack cars discovered by the New York Central System (now the Penn Central) and the economics of drag-reducing design modifications. The program cons...

R. W. Luebke

1969-01-01

371

Embedded Parallelization Approach for Optimization in Aerodynamic Design  

Microsoft Academic Search

A new efficient parallelization strategy for optimization of aerodynamic shapes is proposed. The optimization method employs a full Navier-Stokes solver for accurate estimation of the objective function. As such it requires huge computational resources which makes efficient parallelization crucial for successful promotion of the method to an engineering environment. The algorithm is based on a multilevel embedded parallelization approach, which

S. Peigin; Boris Epstein

2004-01-01

372

System identification technology for estimating reentry vehicle aerodynamic coefficients  

Microsoft Academic Search

This paper describes the development and application of a system identification technology to obtain accurate estimates of maneuvering reentry vehicle aerodynamic coefficients from flight data. The impact of the specific maneuvering reentry vehicle characteristics on system identification is described and appropriate solutions are proposed. Examples illustrate the effectiveness of the technology.

Narendra K. Gupta; W. Earl Hall

1977-01-01

373

CFD based unsteady aerodynamic modeling for rotor aeroelastic analysis  

Microsoft Academic Search

A Computational Fluid Dynamics (CFD) analysis is developed for 3-D rotor unsteady aerodynamic load prediction. It is then coupled to a rotor structural analysis for predicting aeroelastic blade response, airloads and vibration. The CFD analysis accounts for the elastic deformations using a dynamically deforming mesh system. All the rotor blades are assumed to be identical, therefore to reduce the computational

Jayanarayanan Sitaraman

2003-01-01

374

Aerodynamic Performances of Corrugated Dragonfly Wings at Low Reynolds Numbers  

Microsoft Academic Search

The cross-sections of dragonfly wings have well-defined corrugated configurations, which seem to be not very suitable for flight according to traditional airfoil design principles. However, previous studies have led to surprising conclusions of that corrugated dragonfly wings would have better aerodynamic performances compared with traditional technical airfoils in the low Reynolds number regime where dragonflies usually fly. Unlike most of

Masatoshi Tamai; Guowei He; Hui Hu

2006-01-01

375

Simplified dragonfly airfoil aerodynamics at Reynolds numbers below 8000  

Microsoft Academic Search

Effective aerodynamics at Reynolds numbers lower than 10 000 is of great technological interest and a fundamental scientific challenge. The current study covers a Reynolds number range of 2000-8000. At these Reynolds numbers, natural insect flight could provide inspiration for technology development. Insect wings are commonly characterized by corrugated airfoils. In particular, the airfoil of the dragonfly, which is able

David-Elie Levy; Avraham Seifert

2009-01-01

376

Advancements in adaptive aerodynamic technologies for airfoils and wings  

Microsoft Academic Search

Although aircraft operate over a wide range of flight conditions, current fixed-geometry aircraft are optimized for only a few of these conditions. By altering the shape of the aircraft, adaptive aerodynamics can be used to increase the safety and performance of an aircraft by tailoring the aircraft for multiple flight conditions. Of the various shape adaptation concepts currently being studied,

Jeffrey Keith Jepson

2006-01-01

377

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

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

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

378

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

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

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

379

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

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

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

380

Evaluation of thermographic phosphor technology for aerodynamic model testing  

SciTech Connect

The goal for this project was to perform technology evaluations applicable to the development of higher-precision, higher-temperature aerodynamic model testing at Arnold Engineering Development Center (AEDC) in Tullahmoa, Tennessee. With the advent of new programs for design of aerospace craft that fly at higher speeds and altitudes, requirements for detailed understanding of high-temperature materials become very important. Model testing is a natural and critical part of the development of these new initiatives. The well-established thermographic phosphor techniques of the Applied Technology Division at Oak Ridge National Laboratory are highly desirable for diagnostic evaluation of materials and aerodynamic shapes as studied in model tests. Combining this state-of-the-art thermographic technique with modern, higher-temperature models will greatly improve the practicability of tests for the advanced aerospace vehicles and will provide higher precision diagnostic information for quantitative evaluation of these tests. The wavelength ratio method for measuring surface temperatures of aerodynamic models was demonstrated in measurements made for this project. In particular, it was shown that the appropriate phosphors could be selected for the temperature range up to {approximately}700 {degree}F or higher and emission line ratios of sufficient sensitivity to measure temperature with 1% precision or better. Further, it was demonstrated that two-dimensional image- processing methods, using standard hardware, can be successfully applied to surface thermography of aerodynamic models for AEDC applications.

Cates, M.R.; Tobin, K.W.; Smith, D.B.

1990-08-01

381

Aerodynamic evaluation of two compact radial-inflow turbine rotors  

Microsoft Academic Search

The aerodynamic evaluation of two highly loaded compact radial turbine rotors was conducted at the NASA Lewis Research Center Small Engine Component Test Facility (SECTF). The experimental results were used for proof-of-concept, for modeling radial inflow turbine rotors, and for providing data for code verification. Two rotors were designed to have a shorter axial length, up to a 10-percent reduced

P. Susan Simonyi; Richard J. Roelke; Roy G. Stabe; Brentley C. Nowlin; Danielle Dicicco

1995-01-01

382

Aerodynamics and flight performance of flapping wing micro air vehicles  

NASA Astrophysics Data System (ADS)

Research efforts in this dissertation address aerodynamics and flight performance of flapping wing aircraft (ornithopters). Flapping wing aerodynamics was studied for various wing sizes, flapping frequencies, airspeeds, and angles of attack. Tested wings possessed both camber and dihedral. Experimental results were analyzed in the framework of momentum theory. Aerodynamic coefficients and Reynolds number are defined using a reference velocity as a vector sum of a freestream velocity and a strokeaveraged wingtip velocity. No abrupt stall was observed in flapping wings for the angle of attack up to vertical. If was found that in the presence of a freestream lift of a flapping wing in vertical position is higher than the propulsive thrust. Camber and dihedral increased both lift and thrust. Lift-curve slope, and maximum lift coefficient increased with Reynolds number. Performance model of an ornithopter was developed. Parametric studies of steady level flight of ornithopters with, and without a tail were performed. A model was proposed to account for wing-sizing effects during hover. Three micro ornithopter designs were presented. Ornithopter flight testing and data-logging was performed using a telemetry acquisition system, as well as motion capture technology. The ability of ornithopter for a sustained flight and a presence of passive aerodynamic stability were shown. Flight data were compared with performance simulations. Close agreement in terms of airspeed and flapping frequency was observed.

Silin, Dmytro

383

Aerodynamic characteristics of proposed assured crew return capability (ACRC) configurations  

Microsoft Academic Search

The aerodynamic characteristics of seven reentry configurations suggested as possible candidate vehicles to return crew members from the U.S. Space Station Freedom to earth has been reviewed. The shapes varied from those capable of purely ballistic entry to those capable of gliding entry and fromk parachute landing to conventional landing. Data were obtained from existing (published and unpublished) sources and

George M. Ware; Bernard Spencer Jr.; John R. Micol

1989-01-01

384

Take-off and Aerodynamic Characteristics of a Taketombo  

NASA Astrophysics Data System (ADS)

The taketombo is a traditional flying toy of Japan transmitted from old times. Since the taketombo is made of a bamboo, it is also called the bamboo dragonfly. The taketombo consists of two parts, the wing and the shaft. The wing generates the lift, and the shaft is for giving rotation to the taketombo. However, the take-off and aerodynamic characteristics are not yet studied. Then, to study the take-off and aerodynamic characteristics of a taketombo, free flight test and wind tunnel test were performed. Free flight test of the taketombo were carried out to obtain base line data to experiment in the wind tunnel test. Flight data of the taketombo at the take-off in free air was reduced by analyzing the flight path from the high speed video which recorded the take-off flights of the taketombo. A wind tunnel test was conducted using two wing section models, normal and super taketombos. Forces were measured to investigate aerodynamic characteristics of the wing section of two taketombos. The aerodynamic characteristics of normal and super taketombos were compared.

Yasuda, Kunio

385

Active vibration and noise alleviation in rotorcraft using microflaps  

NASA Astrophysics Data System (ADS)

This work presents a comprehensive analysis of active Gurney flaps, or microflaps, for on blade control of noise and vibration in rotorcraft. The initial portion of the work considered the two-dimensional unsteady aerodynamic characteristics of three different oscillating microflap configurations using a compressible computational fluid dynamics (CFD) flow solver. Among these the configuration most suitable for rotorcraft applications was chosen. An unsteady reduced order aerodynamic model (ROM) was developed for the microflap using the Rational Function Approximation approach and CFD based oscillatory aerodynamic load data. The resulting ROM is a state-space, time-domain model that accounts for unsteadiness, compressibility and time-varying freestream effects. The ROM was validated against direct CFD calculations for a wide range of flow conditions showing excellent agreement. Subsequently, the ROM was then incorporated into a comprehensive rotorcraft simulation code featuring a free-wake model, an acoustic prediction tool, and fully coupled flap-lag-torsional blade dynamics. The higher harmonic control (HHC) algorithm was used to simulate closed-loop active control with a 1.5% chord microflap on a hingeless rotor configuration resembling the MBB BO-105. Three span-wise configurations, single, dual, and a five-microflap configuration were considered. Results indicate that the microflap can achieve reductions ranging from 3-6 dB in the blade-vortex interaction (BVI) noise. Vibration reduction ranging from 70-90% was also demonstrated at both low-speed and high-speed flight conditions. It was also found that reduction in BVI noise results in an increase in vibrations and vice versa, a trend also noted in previous active control studies employing HHC and conventional partial span trailing-edge flaps. Next, simultaneous BVI noise and vibration reduction was studied. A reduction of 2-3 dB in the advancing and retreating side noise combined with a 55% reduction in the vibratory loads was achieved using the five-microflap configuration. The 1.5% chord microflap was also compared to a 20% chord plain trailing-edge flap showing similar effectiveness in reducing vibration and noise. Finally, a new approach for dealing with actuator saturation in the HHC algorithm was developed using nonlinear constrained optimization techniques. The optimization approach takes less computational time compared to the previous approaches while yielding better performance in the case of multiple control surfaces.

Padthe, Ashwani Kumar

386

Comparison of reentry-vehicle dynamic models for the estimation of nonsymmetrical aerodynamic coefficients  

SciTech Connect

Two different mathematical models are used to estimate the aerodynamic coefficients for a reentry vehicle. One model assumes that the aerodynamic coefficients are symmetric and the other does not. An actual reentry vehicle develops an asymmetric shape as the heatshield and nosetip ablate. A comparison of the two models is made as a function of the aerodynamic asymmetry to illustrate the errors made in using the symmetric model when the aerodynamics are asymmetric. The asymmetric model is shown to always be capable of correctly estimating the asymmetric aerodynamic coefficients for the simulations considered in this paper.

McDowell, J.L.; Williamson, W.E. Jr.

1982-01-01

387

Noise in Semiconductor Devices  

NASA Astrophysics Data System (ADS)

The devices under study are Si JFETs, Si MOSFETs, GaAs MESFETs, and AlGaAs/GaAs MODFETs. For Si JFETs, by way of two gates--one normal control gate and one substrate gate we can minimize the generation-recombination noise by proper biasing these two gates to study the 1/f noise source. Chapter four gives the noise studies about MOSFETs both p channel and n channel. We derived the equations for the number fluctuation model and the mobility fluctuation model. The measurements of MOSFETs show presence of the number fluctuation noise. We also discuss 1/f noise and thermal noise in weak inversion, limiting 1/f noise, and flicker noise related with gate-voltage-dependent mobility. In GaAs MESFETs we observe the 1/f noise through diffusion noise to thermal noise. For the low-frequency diffusion noise, the Poole-Frenkel effect gives a shift of the corner frequency and from the noise spectra versus temperature, we can deduce the activation energy. At negative gate bias and floating drain the drain shows thermal noise, but when the gate is biased positively so that it draws gate current it will contribute excess noise to the floating drain. The current noise spectra at both the gate and the floating drain show an I('2mV1/V) relationship, which is common for the Schottky barrier diodes. Low frequency noise measurements in MODFETs, at a given frequency the equivalent saturated current varies as the square of the applied voltage, as expected for a fluctuating resistor, and saturates when the characteristic saturates. Measurements on ungated devices shine light on the degration factors in MODFETs and locate the noise sources in MODFETs. Chapter seven is a very practical approach to study the noise performance of those devices applied in high frequency applications. It starts from the background of the theory. Then when the device D.C. characterizations, scattering parameters, microwave noise figure, thermal noise measurement, and low frequency noise measurements, one can have a complete characterization of the device and give a real guidance for low noise device development.

Duh, Kuang-Hann George

388

Investigation of the transient aerodynamic phenomena associated with passing manoeuvres  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

389

Propagation of Environmental Noise  

ERIC Educational Resources Information Center

Solutions for environmental noise pollution lie in systematic study of many basic processes such as reflection, scattering, and spreading. Noise propagation processes should be identified in different situations and assessed for their relative importance. (PS)

Lyon, R. H.

1973-01-01

390

A Review of Railway Noise Research and Results Since the 5th Iwrn in Voss (norway)  

NASA Astrophysics Data System (ADS)

Since the 1995 International Workshop on Railway Noise in Voss, two major elements may be considered as influential to railway noise research: -- there is a clear and strong demand, at the European level as well as nationally for reducing railway noise in terms of operational solutions, especially for freight traffic, -- theoretical developments for modelling rolling noise (which is the major source of noise for conventional speed) reached a point where operational developments of low noise solutions could be successfully carried out with the Twins model. Accordingly, research focused on developing such low noise solutions for rolling noise, investigating subsidiary and still unanswered questions, and addressing outstanding problems related to aerodynamic noise. In parallel to these propagation and annoyance studies were the subject of continuing interests, either with practical results or detailed on-going studies. Finally, modelling interior noise either with modal approaches for lower frequencies, or with SEA for higher frequencies, have proved successful in the case of high speed. Emerging subjects involve a revival of groundborne vibration modelling, roughness generation studies and decision management systems to get the greatest benefit from various potential solutions.

Gautier, P.-E.

2000-03-01

391

A SYSTEM FOR PROVIDING QUALITY OF TESTING, AND ACCURACY OF DETERMINING AERODYNAMIC CHARACTERISTICS OF MODELS AT TSNIIMASH FACILITIES  

Microsoft Academic Search

Together with progress and enhancement of flight vehicles, requirements imposed on a level of onground aerodynamic development and accuracy of experimental determination of aerodynamic characteristics rises. In this connection problems are discussed related to accuracy of determining aerodynamic characteristics through the balance test technique, which is generally used for experimental investigations. Inaccuracy of measurements during experimental investigation of an aerodynamic

V. A. Kozlovsky; M. Lipnitsky; V. I. Lapygin

392

Tow-Ship Noise.  

National Technical Information Service (NTIS)

Geoacoustic inversion from tow-ship noised data acquired on a horizontal towed array is discussed. Through simulations and experimental results, it is shown that even very quiet ships radiate sufficient noise power to enable self-noise inversion of basic ...

W. A. Kuperman W. S. Hodgkiss

2004-01-01

393

Noise model beamforming  

Microsoft Academic Search

Adaptive beamformers are usually based on the premise that noise is stationary and Gaussian, and hence completely characterized by a covariance matrix. The standard approach then attempts to use measured data to estimate that covariance and form a set of beamformer weights that optimally rejects the estimated noise. This standard method may not be robust to mismatch between real noise

Catherine H. Frazier; Iman W. Schurman; Bruce K. Newhall

2003-01-01

394

The hovercraft noise problem  

Microsoft Academic Search

This paper deals with the hovercraft noise problem from two distinct points of view. At the outset, hovercraft noise is reviewed in relation to the noise associated with other means of transport. While hovercraft appear to be rather less noisy than aircraft of comparable installed power, they tend to be much noisier than conventional surface transport. It is concluded that,

R. L. Wheeler; G. F. Donno

1966-01-01

395

On lattice quantization noise  

Microsoft Academic Search

We present several results regarding the properties of a random vector, uniformly distributedover a lattice cell. This random vector is the quantization noise of a lattice quantizer at highresolution, or the noise of a dithered lattice quantizer at all distortion levels. We find thatfor the optimal lattice quantizers this noise is wide-sense stationary and white. Any desirablenoise spectra may be

Ram Zamir; Meir Feder

1996-01-01

396

Noise Control Legislation  

Microsoft Academic Search

The national Environmental Protection Agency is expected to issue its recommendations on noise legislation some time during the latter part of 1973. This agency will assume primary responsibility for enforcing noise limits on new products, such as vehicles, construction equipment, electrical equipment, etc. Primary responsibility for community noise control will remain with local governments. Local EPA’s, now involved in air

William A. Smith

1973-01-01

397

Dragline noise survey  

NASA Astrophysics Data System (ADS)

It is estimated that 70%-90% of miners have enough noise induced hearing loss (NIHL) to be classified as a disability (NIOSH, Publication No. 76-172, 1976; Franks, NIOSH Internal Report, 1996). In response, NIOSH is conducting a cross-sectional survey of the mining industry in order to determine the sources of mining noise and offer recommendations on how to mitigate high noise levels, and bring mining operations into compliance with the recent mining noise regulation: 30CFR, Part 62. This paper will outline the results from noise surveys of eight draglines which operate in above-ground coal mining operations. The data recorded include noise dosimetry in conjunction with time-at-task studies and 1/3-octave sound level (Leq, Lmin, and Lmax) measurements. The 1/3-octave band readings were used to create noise contour maps which allowed the spatial and frequency information of the noise to be considered. Comparison of Lmin and Lmax levels offer insight into the variability of the noise levels inside the dragline. The potential for administrative controls is limited due to consistently high noise levels throughout the deck. Implementation of engineering controls is also hindered by the size and number of the noise sources and the frequency content of the noise.

Vipperman, Jeffrey S.; Bauer, Eric R.

2002-05-01

398

Some calculated effects of non-uniform inflow on the radiated noise of a large wind turbine  

NASA Astrophysics Data System (ADS)

Far field computations were performed for a large wind turbine to evaluate the effects of non-uniform aerodynamic loading over the rotor disk. A modified version of the Farassat/Nystrom propeller noise prediction program was applied to account for the variations in loading due to inflow interruption by the upstream support tower. The computations indicate that for the uniform inflow case, relatively low noise levels are generated and the first rotational harmonic dominated the spectrum. For cases representing wake flow deficiences due to the tower structure, subtantially increased noise levels for all harmonics are indicated, the greatest increases being associated with the higher order harmonics.

Greene, G. C.; Hubbard, H. H.

1980-05-01

399

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

PubMed

Wing morphology correlates with flight performance and ecology among adult birds, yet the impact of wing development on aerodynamic capacity is not well understood. Recent work using chukar partridge (Alectoris chukar), a precocial flier, indicates that peak coefficients of lift and drag (C(L) and C(D)) and lift-to-drag ratio (C(L):C(D)) increase throughout ontogeny and that these patterns correspond with changes in feather microstructure. To begin to place these results in a comparative context that includes variation in life-history strategy, we used a propeller and force-plate model to study aerodynamic force production across a developmental series of the altricial-flying mallard (Anas platyrhynchos). We observed the same trend in mallards as reported for chukar in that coefficients of vertical (C(V)) and horizontal force (C(H)) and C(V):C(H) ratio increased with age, and that measures of gross-wing morphology (aspect ratio, camber and porosity) in mallards did not account for intraspecific trends in force production. Rather, feather microstructure (feather unfurling, rachis width, feather asymmetry and barbule overlap) all were positively correlated with peak C(V):C(H). Throughout ontogeny, mallard primary feathers became stiffer and less transmissive to air at both macroscale (between individual feathers) and microscale (between barbs/barbules/barbicels) levels. Differences between species were manifest primarily as heterochrony of aerodynamic force development. Chukar wings generated measurable aerodynamic forces early (<8 days), and improved gradually throughout a 100 day ontogenetic period. Mallard wings exhibited delayed aerodynamic force production until just prior to fledging (day 60), and showed dramatic improvement within a condensed 2-week period. These differences in timing may be related to mechanisms of escape used by juveniles, with mallards swimming to safety and chukar flap-running up slopes to take refuge. Future comparative work should test whether the need for early onset of aerodynamic force production in the chukar, compared with delayed, but rapid, change in the mallard wing, leads to a limited repertoire of flight behavior in adult chukar compared with mallards. PMID:22855612

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

2012-08-01

400

Analyzing mistuned multi-stage turbomachinery rotors with aerodynamic effects  

NASA Astrophysics Data System (ADS)

A great deal of research has been conducted on accurately modeling large cyclic structures such as turbomachinery rotors. Accurate modeling of realistic industrial turbomachinery requires overcoming several challenges. The first is the excessively large size of the finite element models (FEMs) needed, which can contain millions of degrees of freedom per stage of the rotor. The second challenge is the presence of small random variations in the structural properties known as mistuning, which arise from operational wear and/or manufacturing tolerances, and destroy the cyclic symmetry of the FEMs. The third is the complexity of turbomachinery models, which often include multiple stages that often have a mismatched computational grid at the interface between stages. The fourth challenge is associated with modeling the aerodynamic loads on the turbomachinery rotor. Much research has been conducted to overcome the first two challenges. By combining cyclic symmetry analysis and component mode mistuning (CMM), compact single-stage reduced order models (ROMs) can be created to accurately capture the free and forced response of these systems. These highly efficient ROMs can be developed from single sector calculations and can be of the order of the number of sectors in the stage. Recently, the third challenge associated with the complexity of modeling multiple stages has been addressed by the authors. Their method uses cyclic symmetry and CMM to form single-stage ROMs (using only single sector models and single sector calculations), and then combines these single-stage ROMs by projecting the motion along the interface between stages along a set of harmonic shape functions. This method allows for the creation of compact ROMs of multi-stage systems with mistuning using sector only calculations. The fourth challenge has been addressed only for single-stage systems by computing a complex aerodynamic matrix (which contains stiffness and damping terms) using an iterative approach. In this work, some of the effects of the aerodynamics on multi-stage systems are explored. The methodology consists of first creating efficient structural ROMs of a multi-stage rotor using the method previously developed, and then iteratively calculating the complex aerodynamic matrices for each stage. A new way to account for the effects of a shift in frequency due to mistuning on the complex aerodynamic matrix is also proposed. Additionally, a new classification of complex multi-stage aeroelastic modes is introduced. The presented results focus on exploring the influences of the aerodynamics and mistuning on the multi-stage response. A variety of numerical results are analyzed for two stages of an industrial rotor.

D'Souza, Kiran; Jung, Chulwoo; Epureanu, Bogdan I.

2013-10-01

401

Bolometer noise: nonequilibrium theory.  

PubMed

New theoretical results for noise in cryogenic bolometers are derived. Johnson noise is reduced by as much as 60% by electrothermal feedback from the bias supply. Phonon noise in the thermal link is reduced by as much as 30% relative to the usual equilibrium formula. Photon noise in the Rayleigh-Jeans limit is computed with attention to the attenuation of the photon correlations in the light beam. Basic results on bolometer responsivity, time constant, and thermal properties are presented in a new and convenient form. Excess 1/f and contact shot noise are also discussed. PMID:20389816

Mather, J C

1982-03-15

402

Propeller noise reduction by means of unsymmetrical blade-spacing  

NASA Astrophysics Data System (ADS)

The noise reduction potential of propellers with circumferentially unsymmetrical blade-spacing is predicted on theoretical grounds and substantiated through both aerodynamic and aeroacoustic full scale wind tunnel experiments. To avoid potential balancing problems such propellers have two (or several) pairs of opposite blades, each such pair constituting a symmetrical two-blade propeller. Spacing angles between these individual blade pairs are optimized towards achieving minimum A-weighted noise radiation in the plane of rotation. The result is then compared with the corresponding noise level from a symmetrical reference propeller with the same total number of geometrically identical blades. The study reveals that the value of the optimum spacing angle depends almost entirely on the operational helical blade-tip Mach number, assuming values of about 40 deg at a Mach number of O.5 and decreasing to 15 deg at a Mach number of 0.8. The noise reduction to be achieved from such unsymmetrical blade-spacing is limited to about 4 dB(A) in the direction of maximum noise radiation since the related acoustic effect is due to interference between the sound pressure signatures of the individual blades. It is found that both the harmonic sound pressure level spectrum and the acoustic directivity pattern is affected.

Dobrzynski, W.

1993-05-01

403

Noise emission of propfans due to the inflow distortions  

NASA Astrophysics Data System (ADS)

The noise emission of counter rotating propellers (CRP) was investigated theoretically and by experiments giving special emphasis to the influence of CRP inflow distortions and to the aerodynamics interaction between the rotors. Experiments were conducted using a 0.6 m scale model CRP with 5 blades on the front rotor and 6 blades on the rear rotor in an open-jet wind tunnel for take off and landing conditions. The emitted sound power was measured in the wind tunnel reverberation room, measurements of noise directivity were performed in the acoustic nearfield. The velocity distributions in the inflow and downwash of the CRP were analyzed as well as the flow between the rotor planes. Additional noise power measurement were conducted using a 1 ft. scale model 8 x 8 CRP. A system of computer programs has been developed to predict the emitted noise fields starting with the distorted flow and calculating steady and unsteady blade loads as a function of the radial positions. Measurements of the noise levels and the sound spectrum are in good agreement with the theoretical predictions.

Loelgen, Th.; Neuwerth, G.

404

Active noise cancellation algorithms for impulsive noise  

NASA Astrophysics Data System (ADS)

Impulsive noise is an important challenge for the practical implementation of active noise control (ANC) systems. The advantages and disadvantages of popular filtered-X least mean square (FXLMS) ANC algorithm and nonlinear filtered-X least mean M-estimate (FXLMM) algorithm are discussed in this paper. A new modified FXLMM algorithm is also proposed to achieve better performance in controlling impulsive noise. Computer simulations and experiments are carried out for all three algorithms and the results are presented and analyzed. The results show that the FXLMM and modified FXLMM algorithms are more robust in suppressing the adverse effect of sudden large amplitude impulses than FXLMS algorithm, and in particular, the proposed modified FXLMM algorithm can achieve better stability without sacrificing the performance of residual noise when encountering impulses.

Li, Peng; Yu, Xun

2013-04-01

405

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD  

SciTech Connect

An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-e model, is not appropriate at angles of attack with flow separation. 14 refs., 28 figs., 4 tabs.

Wolfe, W.P. [Sandia National Labs., Albuquerque, NM (United States); Ochs, S.S. [Iowa State Univ., Ames, IA (United States). Aerospace Engineering Dept.

1997-09-01

406

Dry deposition onto aerodynamic surfaces and vegetation. Final report  

SciTech Connect

Carnegie-Mellon University measured dry deposition of aerosols and nitric acid gas to aerodynamic surrogate surfaces in three sets of field experiments. The first field study was during the Southern California Air Quality Study (SCAQS) in June and July 1988. The second set was during the extension of SCAQS in August and September. Both these sets of measurements were conducted at the Bernard Biological Station and at Claremont McKenna College in Claremont, CA. The third experiment involved sampling at Emerald Lake in Sequoia National Park. The first field study included measurements of deposition of Waxleaf Privet, Canary Island Pine, and Japanese Privet. All three studies used Teflon plates and nylon filters set into an aerodynamic surface to measure particle and gas deposition.

Wu, Y.L.; Davidson, C.

1989-02-17

407

Aerodynamic Characteristics of NACA4402 in Low Reynolds Number Flows  

NASA Astrophysics Data System (ADS)

Gas flow over a two-dimensional airfoil at very low Reynolds number is investigated in order to understand basic aerodynamic characteristics related to design of Micro Air Vehicle (MAV) for planetary exploration. Before the investigations, verification was conducted for the current numerical approach, which are commonly used and validated for high Reynolds number flow analysis, showing good applicability for low Reynolds number flow analysis. Flow around NACA4402 has been investigated for the condition of Mach number of 0.1 and Reynolds number of 1,000. Investigation shows that Reynolds number has a substantial influence on aerodynamic characteristics of the airfoil in low Reynolds number flow. In contrast, Mach number has a slight influence in comparison with Reynolds number.

Takaki, Ryoji

408

Influence of a humidor on the aerodynamics of baseballs  

NASA Astrophysics Data System (ADS)

We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. We measure the change in diameter and weight of baseballs as a function of relative humidity in which the balls are stored. The trajectories of pitched and batted baseballs are modeled to assess the difference between those stored at 30% relative humidity versus 50% relative humidity. We find that a drier baseball will curve slightly more than a humidified one for a given pitch velocity and rotation rate. We also find that aerodynamics alone would add 2 ft to the distance a wetter baseball ball is hit. This increased distance is compensated by a 6 ft reduction in the batted distance due to the change in the coefficient of restitution of the ball. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% relative humidity since 2002.

Meyer, Edmund R.; Bohn, John L.

2008-11-01

409

Approximate aerodynamic analysis for horizontal axis wind turbines  

NASA Astrophysics Data System (ADS)

An approximate analysis for the performance of horizontal wind turbines is presented. The analysis assumes constant aerodynamic coefficients and small angles. The analysis is based on disk impulse and blade element theories and results in two models with closed-form equations. One model has a constant interference factor and the other has a variable interference factor. Performance estimates agree closely with those obtained from a more sophisticated analysis. Because the models exist in closed-form equations, performance can be estimated using a hand-held calculator. The models can easily handle changes in aerodynamic coefficients and changes in blade planform. The models are well-suited for preliminary design and cost studies and for performance estimates for small manufacturers.

Beans, E. W.

1983-06-01

410

Aerodynamic shape optimization of Airfoils in 2-D incompressible flow  

NASA Astrophysics Data System (ADS)

An optimization framework was developed for maximizing the region of 2-D airfoil immersed in laminar flow with enhanced aerodynamic performance. It uses genetic algorithm over a population of 125, across 1000 generations, to optimize the airfoil. On a stand-alone computer, a run takes about an hour to obtain a converged solution. The airfoil geometry was generated using two Bezier curves; one to represent the thickness and the other the camber of the airfoil. The airfoil profile was generated by adding and subtracting the thickness curve from the camber curve. The coefficient of lift and drag was computed using potential velocity distribution obtained from panel code, and boundary layer transition prediction code was used to predict the location of onset of transition. The objective function of a particular design is evaluated as the weighted-average of aerodynamic characteristics at various angles of attacks. Optimization was carried out for several objective functions and the airfoil designs obtained were analyzed.

Rangasamy, Srinivethan; Upadhyay, Harshal; Somasekaran, Sandeep; Raghunath, Sreekanth

2010-11-01

411

Minimizing the Trailing Edge Noise from Rotor-Only Axial Fans Using Design Optimization  

NASA Astrophysics Data System (ADS)

Numerical design optimization was used to minimize the trailing edge noise of rotor-only axial fans. The design variables were: hub radius, number of blades, rotational speed of the rotor and spanwise distributions of chord length, stagger angle and camber angle. Imposed constraints assured a minimum pressure rise and non-stalled flow conditions across the blades. A blade element model was used to calculate the aerodynamic performance of the fan and, furthermore, provided velocities used in the calculation of the trailing edge noise. Optimizations were made to (1) minimize trailing edge noise, (2) maximize efficiency, and (3) minimize the rotational speed of the rotor. The resulting designs were compared and the potential benefit of minimizing the trailing edge noise was found to be large. Also, the trailing edge noise was minimized while a constraint was imposed on the efficiency. It was found that a considerable noise reduction could be gained with only a limited reduction in fan efficiency. Finally, the dependency of the minimum trailing edge noise on the size of the hub radius was examined. From this, a hub radius existed, for which a minimum trailing edge noise was obtained, and small variations in hub radius could be made with only a limited increase in trailing edge noise.

Sørensen, D. N.

2001-10-01

412

Identification of aerodynamic coefficients with a neural network  

Microsoft Academic Search

The components of a framework for the procurement, identification, and employment of aerodynamic coefficients are developed. The basic structure follows the estimation-before-modeling (EBM) technique. In the EBM methodology, state estimation and model determination are broken into two independent steps. An extended Kalman-Bucy filter and a modified Bryson-Frazier smoother are used to estimate state and force histories from a measurement vector.

Kristina Anne Richardson

2000-01-01

413

Anodized aluminum pressure sensitive paint for unsteady aerodynamic applications  

Microsoft Academic Search

A comprehensive study of anodized aluminum pressure sensitive paint (AA-PSP) is documented. The study consisted of the development of AA-PSP and its application to unsteady aerodynamic fields at atmospheric conditions. Luminophore application mechanism and two-component application on anodized aluminum was studied for the development. Two-component application includes hydrophobic-coated AA-PSP and bi-luminophore system. It was found that the polarity of solvents

Hirotaka Sakaue

2003-01-01

414

Influence of Wake Models on Calculated Tiltrotor Aerodynamics  

Microsoft Academic Search

Comparisons of measured and calculated aerodynamic behavior of a tiltrotor model are presented. The test of the Tilt Rotor Aeroacoustic Model (TRAM) with a single, 1\\/4-scale V- 22 rotor in the German-Dutch Wind Tunnel (DNW) provides an extensive set of aeroacoustic, performance, and structural loads data. The calculations were performed using the rotorcraft comprehensive analysis CAMRAD II. Presented are comparisons

Wayne Johnson

2002-01-01

415

Rationalizing the bumps on whale flippers using basic aerodynamic theory  

NASA Astrophysics Data System (ADS)

Recent experiments and numerics demonstrated that bumps on the leading edge of humpback whale flippers can lead to an increase in the lift/drag ratio and an increase in the stall angle, as compared to smooth flippers. Using basic aerodynamic theory (potential flow around a Joukowski profile, combined with lifting-line theory) we attempt to rationalize the experimental and numerical findings. We use this basic theory to find perturbations which could lead to an increase in stall angle.

van Nierop, Ernst; Alben, Silas; Brenner, Michael

2006-11-01

416

Prediction of Aerodynamic Interactions of Helicopter Rotor on its Fuselage  

Microsoft Academic Search

An iterative and full-coupled rotor\\/fuselage aerodynamic interaction analytical method is developed based upon the rotor free wake model and the 3-D fuselage panel model. A close vortex\\/surface interaction model using the Analytical\\/Numerical Matching (ANM) was adopted in the method in order to simulate effectively the unsteady close interaction between the rotor tip-vortex and fuselage surface. By the analytical method, the

Guo-hua XU; Qi-jun ZHAO; Zheng GAO; Jing-gen ZHAO

2002-01-01

417

The Legacy of Camillo Possio to Unsteady Aerodynamics  

Microsoft Academic Search

First a brief overview is given of Camillo Possio’s short but outstanding and fruitful career. This is followed by an outline\\u000a of the state of the art in flutter and unsteady aerodynamic research, and the challenges and problems like high-speed flight\\u000a that arose in aircraft development at that time. Possio’s first publications on gas dynamic and supersonic problems are reviewed.

R. Voss

2005-01-01

418

Optimum Aerodynamic Design Using the Navier–Stokes Equations  

Microsoft Academic Search

:   This paper describes the formulation of optimization techniques based on control theory for aerodynamic shape design in viscous\\u000a compressible flow, modeled by the Navier–Stokes equations. It extends previous work on optimization for inviscid flow. The\\u000a theory is applied to a system defined by the partial differential equations of the flow, with the boundary shape acting as\\u000a the control. The

A. Jameson; L. Martinelli; N. A. Pierce

1998-01-01

419

Flow Physics and Stokes’ Theorem in Wind Turbine Aerodynamics  

Microsoft Academic Search

A viscous lift theorem is derived from a momentum balance and Stokes’ theorem around one section of a wind turbine blade.\\u000a The theorem is a generalization of the classical Kutta-Zhukovsky lift theorem and is validated for 2D attached and separated\\u000a flow. The application of the viscous lift theorem within a coupled Navier-Stokes\\/Vortex-Panel solver gives insight into the\\u000a complex 3D aerodynamics

Sven Schmitz; Jean-Jacques Chattot

420

Numerical investigation of aerodynamic characteristics of a new wind turbine  

Microsoft Academic Search

Present work conducts computer simulations with the Computational Fluid Dynamics (CFD) software package Fluent as a modeling tool to explore aerodynamic characteristics of a newly designed wind turbine for electricity generation. The governing equations consisting of three-dimensional, time-dependent conservation of mass and momentum are solved. The k-? turbulence model is adopted for the turbulent flow computation. The three-dimensional, tapered and

Pey-Shey Wu; Mien-Ying Kung; Hung-Yun Wu; Chin-Jen Chang

2010-01-01

421

Effect of flapping trajectories on the dragonfly aerodynamics  

Microsoft Academic Search

The effects of translational, figure-eight and double-figure-eight flapping trajectories on the dragonfly aerodynamics were\\u000a numerically studied by solving the Navier-Stokes equations. There is a common characteristic regarding the lift\\/drag force\\u000a coefficients that the downstroke flapping provides the lift forces while the upstroke flapping creates the thrust forces for\\u000a different flapping trajectories. The maximum lift force coefficient exceeds five for the

Jinliang Xu; Chuangxin Zhao; Yongli Zhang; Yang Zhang

2006-01-01

422

Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications  

Microsoft Academic Search

Successful application of gas discharges in aerodynamics requires their efficient generation, sustaining and control at supersonic or hypersonic flow conditions. Wall-free plasma formations that meet the requirements may then act as time-controlled and space-localized actuators to modify the flow. Potential candidates for this challenging task are plasmas contained in open or linear-cavity microwave field structures. We present and discuss direct

Svetozar Popovic

2006-01-01

423

Aerodynamic calculational methods for curved-blade Darrieus VAWT WECS  

NASA Astrophysics Data System (ADS)

Calculation of aerodynamic performance and load distributions for curved-blade wind turbines is discussed. Double multiple stream tube theory, and the uncertainties that remain in further developing adequate methods are considered. The lack of relevant airfoil data at high Reynolds numbers and high angles of attack, and doubts concerning the accuracy of models of dynamic stall are underlined. Wind tunnel tests of blade airbrake configurations are summarized.

Templin, R. J.

1985-03-01

424

Optimization of a synthetic jet actuator for aerodynamic stall control  

Microsoft Academic Search

The numerical simulation of aerodynamic stall control using a synthetic jet actuator is presented and the automatic optimization of the control parameters is investigated. Unsteady Reynolds-averaged Navier–Stokes equations are solved on unstructured grids using a near-wall low-Reynolds number turbulence closure to simulate the effects of a synthetic jet, located at 12% of the chord from the leading edge of a

Régis Duvigneau; Michel Visonneau

2006-01-01

425

Numerical simulation of aerodynamics and dynamics of wind turbines  

Microsoft Academic Search

Processes of aerodynamics and dynamics are described by incompressible Reynolds averaged Navier-Stokes equations and the equation of wind turbine rotation. Three one-equation turbulence models SA, SARC and SALSA are used. Incompressible Navier-Stokes equations were solved in time-accurate manner using the method of pseudocompressibility and Rogers-Kwak scheme. The finite-volume approach in generalized coordinates was used. Verification of the developed CFD algorithms

Dmytro Redchyts

2007-01-01

426

Aerodynamic stability of cable-supported bridges using CFRP cables  

Microsoft Academic Search

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based\\u000a on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables\\u000a are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical\\u000a investigations on the aerodynamic

Xin-jun Zhang; Lei-dong Ying

2007-01-01

427

Aerodynamic performance of thin wings at low Reynolds numbers  

Microsoft Academic Search

Purpose – The purpose of this paper is to explore the aerodynamic performance of wings with different shapes at low Reynolds numbers. Design\\/methodology\\/approach – The airfoils of these wings are made from aluminum plates, and the maximum chord length and wingspan are 15 cm. Wings A-D are plates with 6 percent Gottingen camber but different wing platforms. The forward-half sections

Jih-Lung Lin; Chin-Yi Wei; Chi-Yu Lin

2009-01-01

428

The Aerodynamics of Free-Flight Maneuvers in Drosophila  

Microsoft Academic Search

Using three-dimensional infrared high-speed video, we captured the wing and body kinematics of free-flying fruit flies as they performed rapid flight maneuvers. We then ``replayed'' the wing kinematics on a dynamically scaled robotic model to measure the aerodynamic forces produced by the wings. The results show that a fly generates rapid turns with surprisingly subtle modifications in wing motion, which

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

2003-01-01

429

Aerodynamic heating of ballistic missile including the effects of gravity  

Microsoft Academic Search

The aerodynamic heating of a ballistic missile due to only convection is analysed taking into consideration the effects of\\u000a gravity. The amount of heat transferred to the wetted area and to the nose region has been separately determined, unlike A\\u000a Miele’s treatise without consideration of gravity. The peak heating rates to the wetted area and to the nose of the

S. N. Maitra

2000-01-01

430

Aerodynamic Optimization of the Arc-Wing Missile  

Microsoft Academic Search

The aerodynamic performance of hypersonic missiles can be improved effectively by assembling the arc wings. With considering\\u000a the security of the missile, both the axial assembling angle and the leading edge of the wings are optimized based on the\\u000a CFD computation and the Nelder-Mead method. The CFD analysis of the optimized and the original configuration show that the\\u000a increase of

K. Cui; G. W. Yang

431

Aerodynamic characteristics research on wide-speed range waverider configuration  

Microsoft Academic Search

Waverider generated from a given flow field has a high lift-to-drag ratio because of attached bow shock on leading edge. However,\\u000a leading edge blunt and off-design condition can make bow shock off leading edge and have unfavorable influence on aerodynamic\\u000a characteristics. So these two problems have always been concerned as important engineering science issues by aeronautical\\u000a engineering scientists. In this

FaMin Wang; HaiHe Ding; MaiFang Lei

2009-01-01

432

High altitude, high angle-of-attack reentry vehicle aerodynamics  

Microsoft Academic Search

Experimental, theoretical, and systems investigations of the high altitude, high angle-of-attack performance of hypersonic reentry vehicles are presented. An exact free-molecular-flow theory, which includes the effects of angle-of-attack, reveals that spin will induce a side force and yawing moment in the direction opposite to that predicted by the inviscid continuum theory. Probabilistic aerodynamic modeling techniques in the transition regime are

A. M. Morrison; K. Y. Chien; C. Fiscina; S. Pronchick

1982-01-01

433

Aerodynamics of an Airfoil at Ultra-Low Reynolds Number  

Microsoft Academic Search

A comprehensive experimental study is conducted of the aerodynamic characteristics of an NACA0012 airfoil over a large range\\u000a of angle (?) of attack and low- to ultra-low cord Reynolds numbers, 5.3×103 - 5.1×104, which is of both fundamental and practical importance. While the mean and fluctuating lift and drag coefficients were measured\\u000a using a load cell, the detailed flow structure

Y. Zhou; H. Yang

2009-01-01

434

Aerodynamic Optimization of Supersonic Transport at Near-Sonic Regime  

Microsoft Academic Search

Recently, an airplane cruising at near-sonic regime is watched with keen interest. The Sonic-Cruiser, of which the Boeing Company has examined and challenged the development, is the most remarkable case. In this paper, motivated by this trend, aerodynamic performance optimization for an airplane cruising at near-sonic regime is discussed based on CFD simulations. NAL's experimental supersonic airplane, called NEXST-1, was

Wataru Yamazaki; Kisa Matsushima; Shigeru Obayashi; Kazuhiro Nakahashi

2003-01-01

435

Application of CFD to Rail Car and Locomotive Aerodynamics  

Microsoft Academic Search

CFD methods have been employed to solve a number of efficiency, safety and operational problems related to the aerodynamics\\u000a of rail cars and locomotives. This paper reviews three case studies: 1) numerical models were employed to quantify the drag\\u000a characteristics of two external railcar features; namely, well car side-posts and inter-platform gaps. The effects of various\\u000a design modifications on train

James C. Paul; Richard W. Johnson; Robert G. Yates

436

Newton's aerodynamic problem in the presence of friction  

Microsoft Academic Search

.   This paper delivers an extension to a celebrated solution of Newton on the shape of the profile of an axisymmetric rigid\\u000a body which, under prescribed length and caliber, has the least aerodynamic resistance. Newton assumed that the drag exerted\\u000a by the surrounding gas on the body is exclusively due to the smooth impact of small gaseous particles against its

Dirk Horstmann; Bernd Kawohl; Piero Villaggio

2002-01-01

437

Effects of exposure to sulfur mustard on speech aerodynamics.  

PubMed

Sulfur mustard is an alkylating agent with highly cytotoxic properties even at low exposure. It was used widely against both military and civilian population by Iraqi forces in the Iraq-Iran war (1983-1988). Although various aspects of mustard gas effects on patients with chemical injury have been relatively well characterized, its effects on speech are still evolving. We evaluated aerodynamics of speech in male patients following sulfur mustard inhalation. In a case-control study patients with chemical injuries (n=19) along with age and sex-matched healthy control group (n=20) were selected. Aerodynamic analyses were performed by using the Glasgow Airflow Measurement System (known as ST1 dysphonia). Results indicated that except mean flow rate, there were statistically significant differences in vital capacity, phonation time, phonation volume, vocal velocity index, total expired volume and phonation quotient of patients between experimental and control groups (P<0.05). This study demonstrated mustard gas can impair different parameters of speech aerodynamics. Learning outcomes: As a result of this activity, the reader will be able to describe: (1) the evaluation of air flow in relation to speech system dysfunction and efficiency; (2) the effect of sulfur mustard known as mustard gas on respiratory physiology. PMID:21310428

Heydari, Fatemeh; Ghanei, Mostafa

2011-01-19

438

Atmospheric tests of trailing-edge aerodynamic devices  

SciTech Connect

An experiment was conducted at the National Renewable Energy Laboratory`s (NREL`s) National Wind Technology Center (NWTC) using an instrumented horizontal-axis wind turbine that incorporated variable-span, trailing-edge aerodynamic brakes. The goal of the investigation was to directly compare results with (infinite-span) wind tunnel data and to provide information on how to account for device span effects during turbine design or analysis. Comprehensive measurements were used to define effective changes in the aerodynamic and hinge-moment coefficients, as a function of angle of attack and control deflection, for three device spans (7.5%, 15%, and 22.5%) and configurations (Spoiler-Flap, vented sileron, and unvented aileron). Differences in the lift and drag behavior are most pronounced near stall and for device spans of less than 15%. Drag performance is affected only minimally (about a 30% reduction from infinite-span) for 15% or larger span devices. Interestingly, aerodynamic controls with vents or openings appear most affected by span reductions and three-dimensional flow.

Miller, L.S.; Huang, S. [Wichita State Univ., KS (United States); Quandt, G.A.

1998-01-01

439

Wind Tunnel Tests on Aerodynamic Characteristics of Advanced Solid Rocket  

NASA Astrophysics Data System (ADS)

The Advanced Solid Rocket is being developed by JAXA (Japan Aerospace Exploration Agency). Since its configuration has been changed very recently, its aerodynamic characteristics are of great interest of the JAXA Advanced Solid Rocket Team. In this study, we carried out wind tunnel tests on the aerodynamic characteristics of the present configuration for Mach 1.5. Six test cases were conducted with different body configurations, attack angles, and roll angles. A six component balance, oilflow visualization, Schlieren images were used throughout the experiments. It was found that, at zero angle-of-attack, the flow around the body were perturbed and its drag (axial force) characteristics were significantly influenced by protruding body components such as flanges, cable ducts, and attitude control units of SMSJ (Solid Motor Side Jet), while the nozzle had a minor role. With angle-of-attack of five degree, normal force of CN? = 3.50±0.03 was measured along with complex flow features observed in the full-component model; whereas no crossflow separations were induced around the no-protuberance model with CN? = 2.58±0.10. These values were almost constant with respect to the angle-of-attack in both of the cases. Furthermore, presence of roll angle made the flow more complicated, involving interactions of separation vortices. These data provide us with fundamental and important aerodynamic insights of the Advanced Solid Rocket, and they will be utilized as reference data for the corresponding numerical analysis.

Kitamura, Keiichi; Fujimoto, Keiichiro; Nonaka, Satoshi; Irikado, Tomoko; Fukuzoe, Moriyasu; Shima, Eiji

440

Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications  

NASA Astrophysics Data System (ADS)

Successful application of gas discharges in aerodynamics requires their efficient generation, sustaining and control at supersonic or hypersonic flow conditions. Wall-free plasma formations that meet the requirements may then act as time-controlled and space-localized actuators to modify the flow. Potential candidates for this challenging task are plasmas contained in open or linear-cavity microwave field structures. We present and discuss direct observations of aerodynamic effects activated or modified by wall-free discharges. Further, we compare two generic types of wall-free discharges. First group, applicable for inlet-type structures, consists of a periodic series of microwave-induced plasmoids generated in a linear cavity, using the outgoing wave from a microwave antenna and the reflected wave from a nearby on-axis concave reflector. The plasmoids are spaced at half-wavelength separations according to the standing-wave pattern. The plasmoids are enhanced by an ``effective focusing'' in the near field of the antenna (Fresnel region) as a result of diffraction effects and mode structure. Second group, applicable to supersonic and hypersonic boundary layers, are the surface microwave discharges enhanced by a structure of Hertz dipoles. Standard microwave discharge phenomenology, such as microwave breakdown, mode structure and plasma parameters, is revisited to present a quantitative interpretation of the observed effects. Special attention is given to complex phenomena specific to flow-plasma interaction (double electric layers, ionization waves, instabilities), which provide the physical basis for localized heating in the aerodynamic flow.

Popovic, Svetozar

2006-10-01

441

Aerodynamic Design of AN Ariane 5 Reusable Booster STAGE*  

NASA Astrophysics Data System (ADS)

A the winged liquid fly-back booster (LFBB) is one of the partially reusable space transportation systems considered within the German future space launcher technology research program ASTRA. The regarded system consists of two booster stages, which are attached to the expendable Ariane 5 core stage at an upgraded future technology level. The main area of interest of the presented aerodynamic study is the return flight after the staging procedure which dominates the layout of the LFBB. The present paper discusses the aerodynamic refinement of an existing LFBB design, focussing on its longitudinal stability and trim. Detailed aerodynamic parameter CL? CL ???? studies are performed based on Euler calculations. Force measurements and selected Navier-Stokes simulations confirm this approach. They point out that a LFBB configuration may be designed primarily based on Euler simulations. The discussion of the numerical results and their comparison with experimental results shows that it is possible to adapt the originally given LFBB proposal in a way that it allows a nearly indifferent flight along the complete return trajectory and that it additionally enables a very robust trim behaviour.

Eggers, Th.

2005-02-01

442

Dynamic control of a bistable wing under aerodynamic loading  

NASA Astrophysics Data System (ADS)

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.

Bilgen, Onur; Arrieta, Andres F.; Friswell, Michael I.; Hagedorn, Peter

2013-02-01

443

Aerodynamic applications of Newton- Krylov-Schwarz solvers  

NASA Astrophysics Data System (ADS)

Parallel implicit solution methods are increasingly important in aerodynamics, since reliable low-residual solutions at elevated CFL number are prerequisite to such large-scale applications of aerodynamic analysis codes as aeroelasticity and optimization. In this chapter, a class of nonlinear implicit methods and a class of linear implicit methods are defined and illustrated. Their composition forms a class of methods with strong potential for parallel implicit solution of aerodynamics problems. Newton-Krylov methods are suited for nonlinear problems in which it is unreasonable to compute or store a true Jacobian, given a strong enough preconditioner for the inner linear system that needs to be solved for each Newton correction. In turn, Krylov-Schwarz iterative methods are suited for the parallel implicit solution of multidimensional systems of linearized boundary value problems. Schwarz-type domain decomposition preconditioning provides good data locality for parallel implementations over a range of granularities. These methods are reviewed separately, illustrated with CFD applications, and composed in a class of methods named Newton-Krylov-Schwarz.

Keyes, David E.

444

Unsteady aerodynamics and gust response in compressors and turbines  

SciTech Connect

A comprehensive series of experiments and analyses was performed on compressor and turbine blading to evaluate the ability of current, practical, engineering/analysis models to predict unsteady aerodynamic loading of modern gas turbine blading. This is part of an ongoing effort to improve methods for preventing blading failure. The experiments were conducted in low-speed research facilities capable of simulating the relevant aerodynamic features of turbomachinery. Unsteady loading on compressor and turbine blading was generated by upstream wakes and, additionally for compressors, by a rotating inlet distortion. Fast-response hot-wire anemometry and pressure transducers embedded in the airfoil surfaces were used to determine the aerodynamic gusts and resulting unsteady pressure responses acting on the airfoils. This is the first time that gust response measurements for turbines have been reported in the literature. Several different analyses were used to predict the unsteady component of the blade loading: (1) a classical flat-plate analysis, (2) a two-dimensional linearized flow analysis with a frozen gust model, (3) a two-dimensional linearized flow analysis with a distorted gust model, (4) a two-dimensional linearized Euler analysis, and (5) a two-dimensional nonlinear Euler analysis. Also for the first time, a detailed comparison of these analyses methods is made and the importance of properly accounting for both vortical and potential disturbances is demonstrated. The predictions are compared with experiment and their abilities assessed to help guide designers in using these prediction schemes.

Manwaring, S.R.; Wisler, D.C. (Aerodynamics Research Lab., Cincinnati, OH (United States). GE Aircraft Engines)

1993-10-01

445

Environmental noise in Beijing  

NASA Astrophysics Data System (ADS)

Beijing is a city under rapid development. More than 60% of the complaints on the environment comes from noise pollution. With a road system of total length of 4200 km and thousands of construction sites, road traffic, and construction are the most important noise sources in Beijing. One third of its population of nearly 14 million inhabitants and more than 3 million visitors is influenced by traffic noise and 16% of its inhabitants are living along various roads and expressways. A series of noise control measures have been taken since the early 1980s, such as road system reconstruction and improvement, industrial noise source control, vehicle noise control, as well as various administrative steps, which reduced the traffic noise by 7 dBA with the number and average flux of vehicles multiplied by more than three times and kept the city in a day-night average level around 64 dBA. In this paper, the environmental noise legislation in Beijing is briefly introduced. The historical progress in noise control is reviewed. The noise pollution up-to-date is given and discussed. Some possible improvements and potential opportunities are presented.

Tian, Jing; Wang, Yi

2001-05-01

446

Urban Noise Protection  

NASA Astrophysics Data System (ADS)

Noise belongs to the severest environmental impairments in towns, with road traffic being the most annoying noise source. The reduction of these impairments and the precaution against new noise impacts is an important task of the communities. However, many of the potential abatement measures are not in the responsibility of the communities. In most European countries, noise emission regulations for road and rail vehicles and outdoor machinery are nowadays enforced by the European Union. Noise reception limits are generally enforced by national laws. Therefore, efficient noise abatement in towns has to be coordinated with the regional, national and supranational, i.e. European noise policy. The most important fields of action for the urban noise abatement are the roads, railways and airports with heavy traffic. For the avoidance of health risks due to noise here short-term reductions are needed, which can generally be achieved only by a combination of measures for which different stakeholders are responsible. This underlines the importance of integrated and coordinated noise abatement concepts.

Jäcker-Cüppers, Michael

447

Experimental study of aerodynamic damping in arrays of vibrating cantilevers  

NASA Astrophysics Data System (ADS)

Cantilever structures vibrating in a fluid are encountered in numerous engineering applications. The aerodynamic loading from a fluid can have a large effect on both the resonance frequency and damping, and has been the subject of numerous studies. The aerodynamic loading on a single beam is altered when multiple beams are configured in an array. In such situations, neighboring beams interact through the fluid and their dynamic behavior is modified. In this work, aerodynamic interactions between neighboring cantilever beams operating near their first resonance mode and vibrating at amplitudes comparable to their widths are experimentally explored. The degree to which two beams become coupled through the fluid is found to be sensitive to vibration amplitude and proximity of neighboring components in the array. The cantilever beams considered are slender piezoelectric fans (approximately 6 cm in length), and are caused to vibrate in-phase and out-of-phase at frequencies near their fundamental resonance values. Aerodynamic damping is expressed in terms of the quality factor for two different array configurations and estimated for both in-phase and out-of-phase conditions. The two array configurations considered are for neighboring fans placed face-to-face and edge-to-edge. It is found that the damping is greatly influenced by proximity of neighboring fans and phase difference. For the face-to-face configuration, a reduction in damping is observed for in-phase vibration, while it is greatly increased for out-of-phase vibration; the opposite effect is seen for the edge-to-edge configuration. The resonance frequencies also show a dependence on the phase difference, but these changes are small compared to those observed for damping. Correlations are developed based on the experimental data which can be used to predict the aerodynamic damping in arrays of vibrating cantilevers. The distance at which the beams no longer interact is quantified for both array configurations. Understanding the fluid interactions between neighboring vibrating beams is essential for predicting the dynamic behavior of such arrays and designing them for practical applications.

Kimber, M.; Lonergan, R.; Garimella, S. V.

2009-11-01

448

Noise in electromigrated nanojunctions  

NASA Astrophysics Data System (ADS)

Noise measurements are a probe beyond simple electronic transport that can reveal additional information about electronic correlations and inelastic processes. Here we report noise measurements in individual electromigrated nanojunctions, examining the evolution from the many-channel regime to the tunneling regime, using a radio frequency technique. While we generally observe the dependence of noise on bias expected for shot noise, in approximately 12% of junction configurations we find discrete changes in the bias dependence at threshold values of the bias, consistent with electronic excitation of local vibrational modes. Moreover, with some regularity we find significant mesoscopic variation in the magnitude of the noise in particular junctions even with small changes in the accompanying conductance. In another ˜17% of junctions we observe pronounced asymmetries in the inferred noise magnitude as a function of bias polarity, suggesting that investigators should be concerned about current-driven ionic motion in the electrodes even at biases well below those used for deliberate electromigration.

Wheeler, P. J.; Chen, Ruoyu; Natelson, D.

2013-04-01

449

Lifting surface theory to predict aerodynamic forces induced by oscillating blades under interaction of three bladerows  

NASA Astrophysics Data System (ADS)

The paper presents the unsteady lifting surface theory to predict unsteady aerodynamic forces on blades of aerodynamically coupled three annular bladerows. Blades of any one bladerow are assumed to be vibrating. The bladerows are assumed to be individually rotating with arbitrary rotational velocities, and therefore the model can be reduced to a rotor/stator/rotor model or a counter-rotating multi-rotor system model by appropriately specifying rotational velocity parameters. The details of the mathematical formulations and the solution procedures are described. Numerical studies were conducted. The disturbances produced by a simple harmonic blade vibration are composed of multiple frequency components because of aerodynamic interaction between bladerows in mutual rotational motions. Relative magnitudes of the frequency components of the unsteady aerodynamic forces are made clear. Not only the effects of nonoscillating neighboring bladerows on the unsteady aerodynamic response of the oscillating bladerow, but also the unsteady aerodynamic forces on nonoscillating neighboring bladerows induced by the oscillating bladerow are investigated.

Namba, Masanobu; Nakagawa, Hiroyuki; Kubo, Ayumi

2009-10-01

450

Jet Noise: Since 1952  

Microsoft Academic Search

:   Jet noise research was initiated by Sir James Lighthill in 1952. Since that time, the development of jet noise theory has\\u000a followed a very tortuous path. This is, perhaps, not surprising for the understanding of jet noise is inherently tied to the\\u000a understanding of turbulence in jet flows. Even now, our understanding of turbulence is still tenuous. In the

Christopher K. W. Tam

1998-01-01

451

Estimating computational noise.  

SciTech Connect

Computational noise in deterministic simulations is as ill-defined a concept as can be found in scientific computing. When coupled with adaptive strategies, the effects of finite precision destroy smoothness of the simulation output and complicate subsequent analysis. Following the work of Hamming on roundoff errors, we present a new algorithm, ECnoise, for quantifying the noise level of a computed function. Our theoretical framework is based on stochastic noise but does not assume a specific distribution for the noise. For the deterministic simulations considered, ECnoise produces reliable results in a few function evaluations and offers new insights into building blocks of large scale simulations.

More', J. J.; Wild, S. M. (Mathematics and Computer Science)

2011-01-01

452

Reliability, synchrony and noise  

PubMed Central

The brain is noisy. Neurons receive tens of thousands of highly fluctuating inputs and generate spike trains that appear highly irregular. Much of this activity is spontaneous—uncoupled to overt stimuli or motor outputs—leading to questions about the functional impact of this noise. Although noise is most often thought of as disrupting patterned activity and interfering with the encoding of stimuli, recent theoretical and experimental work has shown that noise can play a constructive role—leading to increased reliability or regularity of neuronal firing in single neurons and across populations. These results raise fundamental questions about how noise can influence neural function and computation.

Ermentrout, G. Bard; Galan, Roberto F.; Urban, Nathaniel N.

2008-01-01

453

Noise in biological circuits  

SciTech Connect

Noise biology focuses on the sources, processing, and biological consequences of the inherent stochastic fluctuations in molecular transitions or interactions that control cellular behavior. These fluctuations are especially pronounced in small systems where the magnitudes of the fluctuations approach or exceed the mean value of the molecular population. Noise biology is an essential component of nanomedicine where the communication of information is across a boundary that separates small synthetic and biological systems that are bound by their size to reside in environments of large fluctuations. Here we review the fundamentals of the computational, analytical, and experimental approaches to noise biology. We review results that show that the competition between the benefits of low noise and those of low population has resulted in the evolution of genetic system architectures that produce an uneven distribution of stochasticity across the molecular components of cells and, in some cases, use noise to drive biological function. We review the exact and approximate approaches to gene circuit noise analysis and simulation, and reviewmany of the key experimental results obtained using flow cytometry and time-lapse fluorescent microscopy. In addition, we consider the probative value of noise with a discussion of using measured noise properties to elucidate the structure and function of the underlying gene circuit. We conclude with a discussion of the frontiers of and significant future challenges for noise biology.

Simpson, Michael L [ORNL; Allen, Michael S. [University of Tennessee, Knoxville (UTK); Cox, Chris D. [University of Tennessee, Knoxville (UTK); Dar, Roy D. [University of Tennessee, Knoxville (UTK); Karig, David K [ORNL; McCollum, James M. [Miami University; Cooke, John F [ORNL

2009-01-01

454

Geometric/aerodynamic equivalent diameter ratios of ash aggregate aerosols collected in burning Kuwaiti well fields  

NASA Astrophysics Data System (ADS)

The ratio of aerodynamic equivalent diameter to geometric diameter was found for aerosols collected at ground-level from burning oil fields in Kuwait. Ash and soil aerosols collected using an eight-stage DRUM impactor were geometrically sized by scanning electron microscopy. Ash aggregates are shown to have a geometric diameter over an order of magnitude larger than their aerodynamic value. Additionally, ash aggregates showed changes in both particle and aggregate morphology with aerodynamic size.

Reid, Jeffrey S.; Cahill, Thomas A.; Wakabayashi, Paul H.; Dunlap, Michael R.

455

Extracting micro air vehicles aerodynamic forces and coefficients in free flight using visual motion tracking techniques  

Microsoft Academic Search

This paper describes a methodology to extract aerial vehicles’ aerodynamic characteristics from visually tracked trajectory\\u000a data. The technique is being developed to study the aerodynamics of centimeter-scale aircraft and develop flight simulation\\u000a models. Centimeter-scale aircraft remains a largely unstudied domain of aerodynamics, for which traditional techniques like\\u000a wind tunnels and computational fluid dynamics have not yet been fully adapted and

B. F. Mettler

2010-01-01

456

Design of Autopilot for Aerodynamic\\/Reaction-Jet Multiple Control Missile  

Microsoft Academic Search

A new scheme of reaction-jet\\/aerodynamic multi-control missile using pose controlled pulse-engine is present. In this scheme, aerodynamic is used as feedback control, and reaction-jet is feed-forward control. In the first part, the model of the multi-control system is given; then, the aerodynamic controller is designed by using pole assignment, and the reaction-jet controller has been designed by using the term

Qi SHeng Sui; Xin Li; Yong Hua Fan

2008-01-01

457

Platform noise estimation and mitigation  

US Patent & Trademark Office Database

A method and apparatus for platform noise estimation and mitigation are provided. An embodiment of a method for mitigating noise may include receiving a data signal in a system platform, where the data signal includes a received pseudo noise sequence. Noise on the system platform may be estimated based on the received pseudo noise sequence. In some embodiments the noise on the system platform may be mitigated based on the noise estimate for the system platform.

Guo; Yongfang (Sunnyvale, CA); Tsui; Ernest T. (Cupertino, CA)

2011-05-03

458

Rotor blade unsteady aerodynamic gust response to inlet guide vane wakes  

SciTech Connect

A series of experiments is performed in an extensively instrumented axial flow research compressor to investigate the fundamental flow physics of wake-generated periodic rotor blade row unsteady aerodynamics at realistic values of the reduced frequency. Unique unsteady data are obtained that describe the fundamental unsteady aerodynamic gust interaction phenomena on the first-stage rotor blades of a research axial flow compressor generated by the wakes from the inlet guide vanes. In these experiments, the effects of steady blade aerodynamic loading and the aerodynamic forcing function, including both the transverse and chordwise gust components, and the amplitude of the gusts, are investigated and quantified.

Manwaring, S.R.; Fleetner, S. (Purdue Univ., West Lafayette, IN (United States). School of Mechanical Engineering)

1993-01-01

459

Noise in Mutually Synchronized Oscillators  

Microsoft Academic Search

The noise output of two mutually synchronized oscillators has been calculated. It is shown how the two oscillators contribute to the noise. The AM noise of the combined output signal turned out to be considerably increased compared to the AM noise of the free-running oscillators. The FM noise can be improved by proper choice of parameters. To check the theory

W. O. Schlosser

1968-01-01

460

Supersonic Jet Noise Reduction  

NASA Astrophysics Data System (ADS)

Three noise reduction technologies have been examined experimentally as they have been applied to overexpanded, perfectly expanded and underexpanded supersonic jets from convergent-divergent nozzles. The technologies include chevrons, fluidic injection and fluidically enhanced chevrons. The flowfield was measured by shadowgraph and particle image velocimetry (PIV). The acoustics were measured by near and far-field microphone. Chevrons were shown to reduce or eliminate screech, reduce broadband shock associated noise and reduce mixing noise. Fluidic injection was shown to reduce screech, reduce broadband shock associated noise and mixing noise. It also shifts the shock-associated noise peaks to higher frequency and generates increased high frequency noise as chevrons do. The fluidic injection produces the same reduction near x/D = 10 at mid frequencies and the same increase in high frequencies near the nozzle as chevrons. Both noise reduction techniques reduce the size of the large scale structures and so both reduce BBSN by the same mechanism. The principal difference between chevrons and fluidic injection is that for constant injection mass flow the effectiveness of fluidic injection increases with decreasing values of Mj while for chevrons the trend is reversed.

Gutmark, Ephraim; Heeb, Nick; Liu, Junhui; Kailasanath, Kailas

2011-11-01

461

Word Identification in Noise.  

ERIC Educational Resources Information Center

|Notes that speech intelligibility has traditionally been measured by presenting words mixed in noise to listeners for identification at different signal-to-noise ratios. The words are produced in isolation or in sequence contexts where the predictability of specific items can be varied. Emphasizes that the technique provides valuable data about…

Pisoni, David B.

1996-01-01

462

Noise in miniature microphones  

NASA Astrophysics Data System (ADS)

The internal noise spectrum in miniature electret microphones of the type used in the manufacture of hearing aids is measured. An analogous circuit model of the microphone is empirically fit to the measured data and used to determine the important sources of noise within the microphone. The dominant noise source is found to depend on the frequency. Below 40 Hz and above 9 kHz, the dominant source is electrical noise from the amplifier circuit needed to buffer the electrical signal from the microphone diaphragm. Between approximately 40 Hz and 1 kHz, the dominant source is thermal noise originating in the acoustic flow resistance of the small hole pierced in the diaphragm to equalize barometric pressure. Between approximately 1 kHz and 9 kHz, the noise originates in the acoustic flow resistances of sound entering the microphone and propagating to the diaphragm. To further reduce the microphone internal noise in the audio band requires attacking these sources. A prototype microphone having reduced acoustical noise is measured and discussed.

Thompson, Stephen C.; Lopresti, Janice L.; Ring, Eugene M.; Nepomuceno, Henry G.; Beard, John J.; Ballad, William J.; Carlson, Elmer V.

2002-02-01

463

Topological Noise Removal  

Microsoft Academic Search

Meshes obtained from laser scanner data often contain topological noise due to inaccuracies in the scanning and merging process. This topological noise complicates sub- sequent operations such as remeshing, parameterization and smoothing. We introduce an approach that removes unnecessary nontrivial topology from meshes. Using a local wave front traversal, we discover the local topolo- gies of the mesh and identify

Igor Guskov; Zoë J. Wood

2001-01-01

464

Ambient infrasound noise  

Microsoft Academic Search

The ambient infrasound noise environment is characterized for 21 globally distributed infrasound arrays in the frequency band of 0.03 to 7 Hz. Power Spectral Density (PSD) is measured for one site of each array for 21 intervals at each of four times of day from January 2003 through January 2004. The ambient noise at infrasound stations is highly variable by

J. Roger Bowman; G. Eli Baker; Manochehr Bahavar

2005-01-01

465

Helicopter internal noise  

Microsoft Academic Search

Compared to fixed wing aircraft, helicopter interior noise is higher, and subjectively more annoying. This is mainly due to discrete frequencies by the main transmission system, and also from other components like main and tail rotor, engines, or cooling fans. Up to now, mainly passive measures have been used for interior noise reduction. Despite intensive experimental and theoretical investigation to

G. Niesl; E. Laudien

1994-01-01

466

Diode Random Noise Generator.  

National Technical Information Service (NTIS)

The noise generator utilizes the reverse breakdown characteristic of avalanche diodes. In the circuit the noise output of one diode randomly varies the bias voltage of a second diode. The circuit includes a power supply, a bias resistor, a coupling capaci...

E. Hirschmann G. N. Kambouris

1965-01-01

467

Aircraft turbofan noise  

Microsoft Academic Search

Turbofan noise generation and suppression in aircraft engines are reviewed. The chain of physical processes which connect unsteady flow interactions with fan blades to far field noise is addressed. Mechanism identification and description, duct propagation, radiation and acoustic suppression are discussed. The experimental technique of fan inflow static tests are discussed. Rotor blade surface pressure and wake velocity measurements aid

J. F. Groeneweg; E. J. Rice

1983-01-01

468

Effects of Background Noise on Total Noise Annoyance.  

National Technical Information Service (NTIS)

Two experiments were conducted to assess the effects of combined community noise sources on annoyance. The first experiment baseline relationships between annoyance and noise level for three community noise sources (jet aircraft flyovers, traffic and air ...

K. F. Willshire

1987-01-01

469

Aerodynamic sound generated by a wing of complex geometry  

NASA Astrophysics Data System (ADS)

The aerodynamic sound produced by a wing in unsteady flow is computed numerically. A boundary element method is used to calculate both the aerodynamic flow and the sound radiated in an attempt to provide a unified and computationally efficient method. This method is intended to help fill the gap between numerically expensive techniques (e.g., RANS, LES) and analytical methods which are available only for a small subset of the wing geometries of interest. The advances made in the current research are through the incorporation of several previously developed techniques in boundary element and vortex methods and their aggregate application to the present aerodynamic sound problem. The method is capable of modeling general three-dimensional wing geometries with a multiple number of wing elements (e.g., flaps) and with thin shear layer wakes that evolve freely with the unsteady flow. The passage of a vortex filament, which also evolves freely and nonlinearly, can be simulated to study the Blade-Vortex Interaction (BVI) problem. Validations with two-dimensional analytical solutions for parallel BVI show that the lift spectra are computed to within 1 dB up to nondimensional frequencies (scaled by the freestream velocity and the half-chord length) of about 10 using only 40 panels along a streamwise wing section. The parallel BVI problem was used to investigate the effects of wing geometry. These results show that the high frequency response is significantly reduced for high thickness, camber, sweep, and taper, but is increased for high angle of attack and flap deflection angle. The most important parameters affecting the BVI signal is observed to be the minimum separation distance between the vortex filament and the wing. It is shown that the correct separation distance is only achieved when the vortex is modeled as evolving freely and nonlinearly.

Wood, Trevor Howard

2002-09-01

470

A New Aerodynamic Parametrization for Real Urban Surfaces  

NASA Astrophysics Data System (ADS)

This study conducted large-eddy simulations (LES) of fully developed turbulent flow within and above explicitly resolved buildings in Tokyo and Nagoya, Japan. The more than 100 LES results, each covering a 1,000 × 1,000 m2 area with 2-m resolution, provide a database of the horizontally-averaged turbulent statistics and surface drag corresponding to various urban morphologies. The vertical profiles of horizontally-averaged wind velocity mostly follow a logarithmic law even for districts with high-rise buildings, allowing estimates of aerodynamic parameters such as displacement height and roughness length using the von Karman constant = 0.4. As an alternative derivation of the aerodynamic parameters, a regression of roughness length and variable Karman constant was also attempted, using a displacement height physically determined as the central height of drag action. Although both the regression methods worked, the former gives larger (smaller) values of displacement height (roughness length) by 20-25 % than the latter. The LES database clearly illustrates the essential difference in bulk flow properties between real urban surfaces and simplified arrays. The vertical profiles of horizontally-averaged momentum flux were influenced by the maximum building height and the standard deviation of building height, as well as conventional geometric parameters such as the average building height, frontal area index, and plane area index. On the basis of these investigations, a new aerodynamic parametrization of roughness length and displacement height in terms of the five geometric parameters described above was empirically proposed. The new parametrizations work well for both real urban morphologies and simplified model geometries.

Kanda, Manabu; Inagaki, Atsushi; Miyamoto, Takashi; Gryschka, Micha; Raasch, Siegfried

2013-08-01

471

Aerodynamic size associations of natural radioactivity with ambient aerosols  

SciTech Connect

The aerodynamic size of /sup 214/Pb, /sup 212/Pb, /sup 210/Pb, /sup 7/Be, /sup 32/P, /sup 35/S (as SO/sub 4//sup 2 -/), and stable SO/sub 4//sup 2 -/ was measured using cascade impactors. The activity distribution of /sup 212/Pb and /sup 214/Pb, measured by alpha spectroscopy, was largely associated with aerosols smaller than 0.52 ..mu..m. Based on 46 measurements, the activity median aerodynamic diameter of /sup 212/Pb averaged 0.13 ..mu..m (sigma/sub g/ = 2.97), while /sup 214/Pb averaged 0.16 ..mu..m (sigma/sub g/ = 2.86). The larger median size of /sup 214/Pb was attributed to ..cap alpha..-recoil depletion of smaller aerosols following decay of aerosol-associated /sup 218/Po. Subsequent /sup 214/Pb condensation on all aerosols effectively enriches larger aerosols. /sup 212/Pb does not undergo this recoil-driven redistribution. Low-pressure impactor measurements indicated that the mass median aerodynamic diameter of SO/sub 4//sup 2 -/ was about three times larger than the activity median diameter /sup 212/Pb, reflecting differences in atmospheric residence times as well as the differences in surface area and volume distributions of the atmospheric aerosol. Cosmogenic radionuclides, especially /sup 7/Be, were associated with smaller aerosols than SO/sub 4//sup 2 -/ regardless of season, while /sup 210/Pb distributions in summer measurements were similar to sulfate but smaller in winter measurements. Even considering recoil following /sup 214/Po ..cap alpha..-decay, the avervage /sup 210/Pb labeled aerosol grows by about a factor of two during its atmospheric lifetime. The presence of 5 to 10% of the /sup 7/Be on aerosols greater than 1 ..mu..m was indicative of post-condensation growth, probably either in the upper atmosphere or after mixing into the boundary layer.

Bondietti, E.A.; Papastefanou, C.; Rangarajan, C.

1986-04-01

472

Simplified dragonfly airfoil aerodynamics at Reynolds numbers below 8000  

NASA Astrophysics Data System (ADS)

Effective aerodynamics at Reynolds numbers lower than 10 000 is of great technological interest and a fundamental scientific challenge. The current study covers a Reynolds number range of 2000-8000. At these Reynolds numbers, natural insect flight could provide inspiration for technology development. Insect wings are commonly characterized by corrugated airfoils. In particular, the airfoil of the dragonfly, which is able to glide, can be used for two-dimensional aerodynamic study of fixed rigid wings. In this study, a simplified dragonfly airfoil is numerically analyzed in a steady free-stream flow. The aerodynamic performance (such as mean and fluctuating lift and drag), are first compared to a ``traditional'' low Reynolds number airfoil: the Eppler-E61. The numerical results demonstrate superior performances of the corrugated airfoil. A series of low-speed wind and water tunnel experiments were performed on the corrugated airfoil, to validate the numerical results. The findings indicate quantitative agreement with the mean wake velocity profiles and shedding frequencies while validating the two dimensionality of the flow. A flow physics numerical study was performed in order to understand the underlying mechanism of corrugated airfoils at these Reynolds numbers. Airfoil shapes based on the flow field characteristics of the corrugated airfoil were built and analyzed. Their performances were compared to those of the corrugated airfoil, stressing the advantages of the latter. It was found that the flow which separates from the corrugations and forms spanwise vortices intermittently reattaches to the aft-upper arc region of the airfoil. This mechanism is responsible for the relatively low intensity of the vortices in the airfoil wake, reducing the drag and increasing the flight performances of this kind of corrugated airfoil as compared to traditional low Reynolds number airfoils such as the Eppler E-61.

Levy, David-Elie; Seifert, Avraham

2009-07-01

473

FLPP IXV Re-Entry Vehicle, Hypersonic Aerodynamics Characterisation  

NASA Astrophysics Data System (ADS)

The general objective of the IXV project (Intermediate eXperimental Vehicle), led by NGL Prime in the framework of the ESA FLPP programme (Future Launchers Preparatory Programme), is to improve European capabilities in the strategic field of atmospheric re-entry for space transportation, exploration, and scientific applications. One of the key objectives and challenges of the IXV project is the vehicle re-entry guidance and control demonstration which requires an accurate determination of the aerodynamic characteristics. This paper deals with all the aerodynamic characterization in the hypersonic flow regime. Wind tunnel tests (WTT) and CFD matrices have been defined in order to provide good coverage of the foreseen flight domain, account for uncertainties, and exploit the synergy between experimental and computational activity. WTT have been performed in DLR-H2K (M=6 and 8.7) and ONERA-S4Ma (M=10) facilities, gathering forces and moment data, as well as pressure in key areas. Consistency of the two campaigns results will be addressed. These results have highlighted some flow peculiarities in the deflected flap region. Comparisons with CFD show good agreement with ground experimental results. For flight conditions, real gas and viscous effects play a significant role in the trim conditions that only CFD can currently address; this identification was supported by different partners involved in the project (CFS engineering, DLR, CIRA, and the University of Rome) providing a valuable description of key flow phenomena affecting aerodynamic characteristics. Moreover, at high altitude, limited DSMC computations have been performed for bridging function correction.

Tran, Ph.; Dormieux, M.; Fontaine, J.; Gülhan, A.; Tribot, J.-P.; Binetti, P.; Walloschek, T.

2009-01-01

474

The effect of inlet turbulence and strut generated disturbances on turbomachinery noise  

NASA Astrophysics Data System (ADS)

This thesis presents results of an investigation in which turbomachine rotor sound spectra variations were correlated with aerodynamic measurements of the inlet turbulence, strut wake, and vortex flow strength. Aerodynamic measurements that were made included mean velocity and turbulence intensity profiles, and the axial length scales. Inlet turbulence data indicate that the major effect of the flow contraction appears to be the elongation of atmospheric turbulent eddies from 20 cm to 200 cm. Eddies of this size dominate the generation of blade passing frequency (BPF) noise. Reducing the eddy size by the use of a grid revealed the vortex flow strength to be the second major source of noise at BPF. A doubling of vortex flow strength produced a 6 dB increase in the source pressure level (SPL) of the first BPF. The variation of the SPL with the decay of the strut wake was small. The SPL showed less than a 2 dB change with a doubling of the wake turbulence intensity or the velocity defect. The measured sound spectra were compared with predicted trends from two different analyses. The results of this comparison further supported the conclusion that the strut wake structure was not as effective in producing noise at the vortex strength or the inlet turbulent eddies. A discussion of the relative importance of various sources of noise due to the flow field is given.

Trunzo, R.

1980-09-01

475

Aerodynamic characteristics of flying fish in gliding flight.  

PubMed

The flying fish (family Exocoetidae) is an exceptional marine flying vertebrate, utilizing the advantages of moving in two different media, i.e. swimming in water and flying in air. Despite some physical limitations by moving in both water and air, the flying fish has evolved to have good aerodynamic designs (such as the hypertrophied fins and cylindrical body with a ventrally flattened surface) for proficient gliding flight. Hence, the morphological and behavioral adaptations of flying fish to aerial locomotion have attracted great interest from various fields including biology and aerodynamics. Several aspects of the flight of flying fish have been determined or conjectured from previous field observations and measurements of morphometric parameters. However, the detailed measurement of wing performance associated with its morphometry for identifying the characteristics of flight in flying fish has not been performed yet. Therefore, in the present study, we directly measure the aerodynamic forces and moment on darkedged-wing flying fish (Cypselurus hiraii) models and correlated them with morphological characteristics of wing (fin). The model configurations considered are: (1) both the pectoral and pelvic fins spread out, (2) only the pectoral fins spread with the pelvic fins folded, and (3) both fins folded. The role of the pelvic fins was found to increase the lift force and lift-to-drag ratio, which is confirmed by the jet-like flow structure existing between the pectoral and pelvic fins. With both the pectoral and pelvic fins spread, the longitudinal static stability is also more enhanced than that with the pelvic fins folded. For cases 1 and 2, the lift-to-drag ratio was maximum at attack angles of around 0 deg, where the attack angle is the angle between the longitudinal body axis and the flying direction. The lift coefficient is largest at attack angles around 30?35 deg, at which the flying fish is observed to emerge from the sea surface. From glide polar, we find that the gliding performance of flying fish is comparable to those of bird wings such as the hawk, petrel and wood duck. However, the induced drag by strong wing-tip vortices is one of the dominant drag components. Finally, we examine ground effect on the aerodynamic forces of the gliding flying fish and find that the flying fish achieves the reduction of drag and increase of lift-to-drag ratio by flying close to the sea surface. PMID:20833919

Park, Hyungmin; Choi, Haecheon

2010-10-01

476

How Bumps on Whale Flippers Delay Stall: An Aerodynamic Model  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments have shown that bumps on the leading edge of model humpback whale flippers cause them to “stall” (i.e., lose lift dramatically) more gradually and at a higher angle of attack. Here we develop an aerodynamic model which explains the observed increase in stall angle. The model predicts that as the amplitude of the bumps is increased, the lift curve flattens out, leading to potentially desirable control properties. We find that stall delay is insensitive to the wavelength of the bumps, in accordance with experimental observations.

van Nierop, Ernst A.; Alben, Silas; Brenner, Michael P.

2008-02-01

477

How bumps on whale flippers delay stall: an aerodynamic model.  

PubMed

Wind tunnel experiments have shown that bumps on the leading edge of model humpback whale flippers cause them to "stall" (i.e., lose lift dramatically) more gradually and at a higher angle of attack. Here we develop an aerodynamic model which explains the observed increase in stall angle. The model predicts that as the amplitude of the bumps is increased, the lift curve flattens out, leading to potentially desirable control properties. We find that stall delay is insensitive to the wavelength of the bumps, in accordance with experimental observations. PMID:18352375

van Nierop, Ernst A; Alben, Silas; Brenner, Michael P

2008-02-07

478

Some aerodynamic aspects of engine secondary air systems  

NASA Astrophysics Data System (ADS)

Internal cooling air systems of turbomachines contain various fluid flow components, i.e. rotating holes, tapping configurations, coverplates, labyrinth seals etc., for which only the basic aerodynamics are known. Numerical calculations for these elements are carried out and compared with test results showing fair agreement in general. For most of the components of internal air systems there is a serious lack of test data. It is shown that the situation can be relieved by applying numerical methods, which should also be used to improve and extend the empirical correlations in the air systems computer programs.

Zimmermann, H.

1989-06-01

479

Aerodynamic Characteristics of Wing Profiles for Wind Generators  

NASA Astrophysics Data System (ADS)

The information presented in this paper suggests that the power generated by the oscillating wing have significant advantages. Parallel information will be presented for two different types of aerodynamic airfoils. The advantages and disadvantages of each airfoil type will be evaluated. A series of equations will be determined to verify if the power generated by an oscillating airfoil is higher than the one generated by a fixed airfoil. Additional, these airfoils will be used to determine the wind energy produced by a wind turbine. Any energetic system which converts the free wind into energy is an advantage system.

Colidiuc, Alexandra; Suatean, Bogdan; Galetuse, Stelian

2011-09-01

480

Aerodynamic Performance of Wind Turbine with Horizontal Axis  

NASA Astrophysics Data System (ADS)

In this paper, the blade arodynamic outline of a 100 kW horizontal axis wind turbine is designed based on the strip theory using low Reynolds number and high lift airfoils. A 1/34 scale model is used to investigate the aerodynamic performance of the prototype by means of wind tunnel test. Based on some similitude criterion and reasonable correction of arodynamic coefficient, the data of prototype can be deduced from the experimente data. Comparared with the theory analysis, the power output can reach the design performance.

Liu, P. Q.; Zhu, J. Y.; Zhao, W. L.

2011-09-01

481

Aerodynamic design considerations for a free-flying ducted propeller  

SciTech Connect

The design philosophy for a free-flying vehicle powered by a ducted propeller is presented from an aerodynamic viewpoint. Airframe design concentrates on duct inlet lip curvature, diffuser angle, and methods of vehicle control. Wind tunnel test results are given to evaluate two inlet designs, two exit designs, and the effect of external appendages such as a camera pod or a forebody. Finally, a simple, analytic method of ducted propeller blade design is presented and the results compared with an existing ducted propeller blade. 14 refs., 28 figs., 2 tabs.

Weir, R.J.

1988-01-01

482

Aerodynamics of two-dimensional slotted bluff bodies  

SciTech Connect

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

Takahashi, F.; Higuchi, H.

1988-04-30

483

Noise Characteristics of Eight Helicopters.  

National Technical Information Service (NTIS)

This report describes the noise characteristics of eight Helicopters during level flyovers, simulated approaches, and hover. The data were obtained during an FAA/DOT Helicopter Noise Program to acquire a data base for possible helicopter noise regulatory ...

E. J. Rickley H. C. True

1977-01-01

484

Noise contaminated transmittance  

SciTech Connect

The authors compare the efficiency of a classifier based on probabilistic neural networks and the general least squares method. Both methods must accommodate noise due to uncertainty in the measured spectrum at each wavelength. The evaluation of both methods is based on a simulated transmittance spectrum, in which the received signal is supplemented by an additive admixture of noise. To obtain a realistic description of the noise model, they generate several hundred laser pulses for each wavelength under consideration. These pulses have a predetermined correlation matrix for different wavelengths; furthermore, they are composed of three components accounting for the randomness of the observed spectrum. The first component is the correlated 1/f noise; the second component is due to uncorrelated 1/f noise; the third one is the uncorrelated white noise. The probabilistic neural network fails to retrieve the species concentration correctly for large noise levels; on the other hand, its predictions being confined to a fixed number of concentration bins, the network produces relatively small variances. To a large extent, the general least square method avoids the false alarms. It reproduces the average concentrations correctly; however, the concentration variances can be large.

Zardecki, A.; McVey, B.D.; Nelson, D.H. [and others

1997-09-01

485

Aerodynamic Properties of Urban Areas Derived from Analysis of Surface Form  

Microsoft Academic Search

Several methods to determine the aerodynamic characteristics of a site through analysis of its surface form (morphometry) are considered in relation to cities. The measures discussed include zero-plane displacement length (zd), roughness length (z 0), depth of the roughness sublayer, and aerodynamic conductance. A sensitivity analysis is conducted on seven formulas to estimate zd and nine to estimate z 0,

C. S. B. Grimmond; T. R. Oke

1999-01-01

486

Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns  

SciTech Connect

The primary objective of the insteady aerodynamics experiment was to provide information needed to quantify the full-scale, three-dimensional aerodynamic behavior of horizontal-axis wind turbines. This report is intended to familiarize the user with the entire scope of the wind tunnel test and to support the use of the resulting data.

Hand, M. M.; Simms, D. A.; Fingersh, L. J.; Jager, D. W.; Cotrell, J. R.; Schreck, S.; Larwood, S. M.

2001-12-01

487

Feasibility study of a novel method for real-time aerodynamic coefficient estimation  

Microsoft Academic Search

In this work, a feasibility study of a novel technique for the real-time identification of uncertain nonlinear aircraft aerodynamic coefficients has been conducted. The major objective of this paper is to investigate the feasibility of a system for parameter identification in a real-time flight environment. This system should be able to calculate aerodynamic coefficients and derivative information using typical pilot

Phillip M. Gurbacki

2010-01-01

488

Determination of aerodynamic diameters of pollen grains and their agglomerates for Western Siberia plants  

NASA Astrophysics Data System (ADS)

Results of determination of aerodynamic characteristics of 17 plants dominating the ecosystem of Western Siberia are reported. Pollen of cereals and woody plants was examined. The sedimentation velocities of single pollen grains and their agglomerates were determined. The data obtained were used to calculate the aerodynamic diameters of pollen grains of all investigated plants.

Istomin, V. L.; Koutsenogii, K. P.; Golovko, V. V.

2012-12-01

489

Sports ball aerodynamics: A numerical study of the erratic motion of soccer balls  

Microsoft Academic Search

The application of the commercial CFD code, FLUENT, to sports ball aerodynamics was assessed and a validated 3D analysis technique was established for balls that have been scanned with a 3D laser scanner or drawn in CAD. The technique was used to examine the effects of surface geometry on the aerodynamic behaviour of soccer balls by comparing the flow around

S. Barber; S. B. Chin; M. J. Carré

2009-01-01

490

Progress in Reducing Aerodynamic Drag for Higher Efficiency of Heavy Duty Trucks (Class 7-8)  

Microsoft Academic Search

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation

Rose McCallen; Richard Couch; Juliana Hsu; Fred Browand; Mustapha Hammache; Anthony Leonard; Mark Brady; Kambiz Salari; Walter Rutledge; James Ross; Bruce Storms; J. T. Heineck; David Driver; James Bell; Gregory Zilliac

1999-01-01

491

Aerodynamic Drag of Heavy Vehicles (Class 7-8): Simulation and Benchmarking  

Microsoft Academic Search

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. Experimental validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the

Rose McCallen; Dan Flowers; Tim Dunn; Jerry Owens; Fred Browand; Mustapha Hammache; Anthony Leonard; Mark Brady; Kambiz Salari; Walter Rutledge; James Ross; Bruce Storms; David Driver J. T. Heineck; James Bell; Steve Walker; Gregory Zilliac

2000-01-01

492

FY 2004 Annual Report: DOE Project on Heavy Vehicle Aerodynamic Drag  

Microsoft Academic Search

The objective of this report is: (1) Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles; and (2) Establish a database of experimental, computational, and conceptual design information, and demonstrate potential of new drag-reduction devices. The approaches used were: (1) Develop and demonstrate the ability to simulate and analyze aerodynamic flow around heavy truck vehicles

R C McCallen; K Salari; J Ortega; P Castellucci; C Eastwood; K Whittaker; L J DeChant; C J Roy; J L Payne; B Hassan; W D Pointer; F Browand; M Hammache; T Hsu; J Ross; D Satran; J T Heineck; S Walker; D Yaste; R Englar; A Leonard; M Rubel; P Chatelain

2004-01-01

493

Progress in reducing aerodynamic drag for higher efficiency of heavy duty trucks (class 7-8)  

Microsoft Academic Search

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation

M Brady; F Browand; M Hammache; J T Heineck; A Leonard; R McCallen; J Ross; W Rutledge; K Salari; B Storms

1999-01-01

494

Development of Pneumatic Aerodynamic Devices to Improve the Performance, Economics, and Safety of Heavy Vehicles  

Microsoft Academic Search

Under contract to the DOE Office of Heavy Vehicle Technologies, the Georgia Tech Research Institute (GTRI) is developing and evaluating pneumatic (blown) aerodynamic devices to improve the performance, economics, stability and safety of operation of Heavy Vehicles. The objective of this program is to apply the pneumatic aerodynamic aircraft technology previously developed and flight-tested by GTRI personnel to the design

Robert J. Englar

2000-01-01

495

Impulse-Based Dynamic Simulation of Articulated Rigid Bodies with Aerodynamics  

Microsoft Academic Search

We propose a physically-based modeling approach to generate effect of aerodynamics. We take the impulse-based method that allows us to treat, articulation, contact, collision in a unified manner. We use the concept of dynamic pressure which is the pressure related to the relative wind velocity, and is frequently adopted in flight simulation and wing design. Moreover, we calculate the aerodynamics

Chia-Da Lee; Li-Chen Fu

2006-01-01

496

Rotor blade unsteady aerodynamic gust response to inlet guide vane wakes  

Microsoft Academic Search

A series of experiments is performed in an extensively instrumented axial flow research compressor to investigate the fundamental flow physics of wake-generated periodic rotor blade row unsteady aerodynamics at realistic values of the reduced frequency. Unique unsteady data are obtained that describe the fundamental unsteady aerodynamic gust interaction phenomena on the first-stage rotor blades of a research axial flow compressor

S. R. Manwaring; S. Fleetner

1993-01-01

497

New frontiers in aerodynamic tailoring of long span bridges: an advanced analysis framework  

Microsoft Academic Search

Significant developments in bridge aeroelastic analysis have been made utilizing realistic aerodynamic force modeling for bridges with bluff sections under turbulent winds. With these developments as a background, this paper highlights state-of-the-art developments in the aeroelastic analysis and identifies new frontiers in aerodynamic tailoring of long span bridges. Challenges in the aeroelastic analysis are pointed out that include: the modeling

Xinzhong Chen; Ahsan Kareem

2003-01-01

498

Effect of Chord Flexure on Aerodynamic Performance of a Flapping Wing  

Microsoft Academic Search

Inspired by the fact that a high flexible wing in nature generates high aerodynamic performance, we investigated the aerodynamic performance of the flapping wing with different chord flexures. The unsteady, incompressible, and viscous flow over airfoil NACA0012 in a plunge motion was analyzed by using Navier-Stokes equation. Grid deformation, in which finite element and interpolation ideas are mixed, was introduced

Tuyen Quang Le; Jin Hwan Ko; Doyoung Byun; Soo Hyung Park; Hoon Choel Park

2010-01-01

499

Moving actuator surfaces : A new concept for wind turbine aerodynamic analysis  

Microsoft Academic Search

The actuator disk is a concept often used in wind turbine aerodynamics, where the action of the turbine on the flow is averaged over time and space. This simplification stills retain sufficient physical information for wind turbine aerodynamic design. Its limitations are essentially related to the impossibility to model the blade shed vorticity. This paper presents a more general approach

Christian Masson; Christophe Sibuet Watters; École de Technologie Supérieure

500

Progress in smart rotor research for wind turbines: experimental and computational approaches to active aerodynamic control  

Microsoft Academic Search

Active distributed aerodynamic control for load reduction on wind turbine blades is an innovative concept, inspired by rotorcraft research, often named as smart rotor control. In this stage of research, unsteady aerodynamic models and small scale experimental setups are developed, investigating the potential and implementation of such concepts. This paper describes a successful wind tunnel experiment on a dynamically scaled

A. K. Barlas

2007-01-01