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1

A new technique for aerodynamic noise calculation  

NASA Technical Reports Server (NTRS)

A novel method for the numerical analysis of aerodynamic noise generation is presented. The method involves first solving for the time-dependent incompressible flow for the given geometry. This fully nonlinear method that is tailored to extract the relevant acoustic fluctuations seems to be an efficient approach to the numerical analysis of aerodynamic noise generation.

Hardin, J. C.; Pope, D. S.

1992-01-01

2

New aspects of subsonic aerodynamic noise theory  

NASA Technical Reports Server (NTRS)

A theory of aerodynamic noise is presented which differs from Lighthill's theory primarily in the way in which convection of the noise sources is treated. The sound directivity pattern obtained from the present theory agrees better with jet-noise directivity data than does that obtained from Lighthill's theory. The results imply that the shear-noise contribution to jet noise is smaller than previously expected.

Goldstein, M. E.; Howes, W. L.

1973-01-01

3

AERODYNAMIC NOISE CONTROL BY OPTIMAL SHAPE A DISSERTATION  

E-print Network

AERODYNAMIC NOISE CONTROL BY OPTIMAL SHAPE DESIGN A DISSERTATION SUBMITTED TO THE DEPARTMENT of the aerodynamic noise propagated to the far field. The optimization method is a tailored version of the surrogate

Marsden, Alison L.

4

Advanced Noise Control Fan Aerodynamic Performance  

NASA Technical Reports Server (NTRS)

The Advanced Noise Control Fan at the NASA Glenn Research Center is used to experimentally analyze fan generated acoustics. In order to determine how a proposed noise reduction concept affects fan performance, flow measurements can be used to compute mass flow. Since tedious flow mapping is required to obtain an accurate mass flow, an equation was developed to correlate the mass flow to inlet lip wall static pressure measurements. Once this correlation is obtained, the mass flow for future configurations can be obtained from the nonintrusive wall static pressures. Once the mass flow is known, the thrust and fan performance can be evaluated. This correlation enables fan acoustics and performance to be obtained simultaneously without disturbing the flow.

Bozak, Richard F., Jr.

2009-01-01

5

Analysis and optimization of aerodynamic noise in a centrifugal compressor  

Microsoft Academic Search

The numerical methods for the performance analysis and the noise prediction of the centrifugal compressor impeller are developed, which are coupled with the optimization design methodology consisting of response surface method, statistical approach, and genetic algorithm. Navier–Stokes equations with the two-equation (k–?) turbulence model are applied to calculate impeller aerodynamic characteristics, and Ffowcs Williams–Hawkings formulation and boundary element method are

Hyosung Sun; Hyungki Shin; Soogab Lee

2006-01-01

6

An anechoic chamber facility for investigating aerodynamic noise  

NASA Technical Reports Server (NTRS)

The aerodynamic noise facility was designed to be used primarily for investigating the noise-generating mechanisms of high-temperature supersonic and subsonic jets. The facility consists of an anechoic chamber, an exhaust jet silencer, instrumentation equipment, and an air heater with associated fuel and cooling systems. Compressed air, when needed for jet noise studies, is provided by the wind tunnel compressor facility on a continuous basis. The chamber is 8.1 m long, 5.0 m wide, and 3.0 m high. Provisions have been made for allowing outside air to be drawn into the anechoic chamber in order to replenish the air that is entrained by the jet as it flows through the chamber. Also, openings are provided in the walls and in the ceiling for the purpose of acquiring optical measurements. Calibration of the chamber for noise reflections from the wall was accomplished in octave bands between 31.2 Hz and 32 kHz.

Massier, P. F.; Parthasarathy, S. P.

1972-01-01

7

Aerodynamic Performance Measurements for a Forward Swept Low Noise Fan  

NASA Technical Reports Server (NTRS)

One source of noise in high tip speed turbofan engines, caused by shocks, is called multiple pure tone noise (MPT's). A new fan, called the Quiet High Speed Fan (QHSF), showed reduced noise over the part speed operating range, which includes MPT's. The QHSF showed improved performance in most respects relative to a baseline fan; however, a partspeed instability discovered during testing reduced the operating range below acceptable limits. The measured QHSF adiabatic efficiency on the fixed nozzle acoustic operating line was 85.1 percent and the baseline fan 82.9 percent, a 2.2 percent improvement. The operating line pressure rise at design point rotational speed and mass flow was 1.764 and 1.755 for the QHSF and baseline fan, respectively. Weight flow at design point speed was 98.28 lbm/sec for the QHSF and 97.97 lbm/sec for the baseline fan. The operability margin for the QHSF approached 0 percent at the 75 percent speed operating condition. The baseline fan maintained sufficient margin throughout the operating range as expected. Based on the stage aerodynamic measurements, this concept shows promise for improved performance over current technology if the operability limitations can be solved.

Fite, E. Brian

2006-01-01

8

Aerodynamic Performance of Fan-Flow Deflectors for Jet-Noise Reduction  

E-print Network

Aerodynamic Performance of Fan-Flow Deflectors for Jet-Noise Reduction Juntao Xiong, Feng Liu used for reducing jet noise from a supersonic turbofan exhaust with bypass ratio of 2.7. The numerical for jet noise k = turbulent kinetic energy L = lift force M = Mach number p = static pressure q = dynamic

Papamoschou, Dimitri

9

Aerodynamics of Wedge-Shaped Deflectors for Jet Noise Reduction Dimitri Papamoschou*  

E-print Network

Aerodynamics of Wedge-Shaped Deflectors for Jet Noise Reduction Dimitri Papamoschou* , An Vu in the fan exhaust of a turbofan engine can reduce jet noise in a range of azimuthal directions opposite base I. Introduction Suppression of noise from engines of jet aircraft is one of the most topical

Papamoschou, Dimitri

10

Study of Aerodynamic Design Procedure of a Large-Scale Aircraft Noise Suppression Facility  

Microsoft Academic Search

The aerodynamic design procedure of a large-scale aircraft noise suppression facility has been developed. Flow quality required for the engine inlet flow has been determined through basic experiment. Aerodynamic design of the facility has been performed by using wind tunnel experiment and CFD. Important relationship between the length of the facility and the inlet flow quality has been found. The

Masafumi Kawai; Kiyoyuki Nagai; Shigeru Aso

2008-01-01

11

Fan Noise Source Diagnostic Test: Rotor Alone Aerodynamic Performance Results  

NASA Technical Reports Server (NTRS)

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 was conducted to identify the noise sources within a wind tunnel scale model of a turbofan engine and quantify their contribution to the overall system noise level. The fan was part of a 1/5th scale model representation of the bypass stage of a current technology turbofan engine. For the rotor alone testing, the fan and nacelle, including the inlet, external cowl, and fixed area fan exit nozzle, were modeled in the test hardware; the internal outlet guide vanes located behind the fan were removed. Without the outlet guide vanes, the velocity at the nozzle exit changes significantly, thereby affecting the fan performance. As part of the investigation, variations in the fan nozzle area were tested in order to match as closely as possible the rotor alone performance with the fan performance obtained with the outlet guide vanes installed. The fan operating performance was determined using fixed pressure/temperature combination rakes and the corrected weight flow. The performance results indicate that a suitable nozzle exit was achieved to be able to closely match the rotor alone and fan/outlet guide vane configuration performance on the sea level operating line. A small shift in the slope of the sea level operating line was measured, which resulted in a slightly higher rotor alone fan pressure ratio at take-off conditions, matched fan performance at cutback conditions, and a slightly lower rotor alone fan pressure ratio at approach conditions. However, the small differences in fan performance at all fan conditions were considered too small to affect the fan acoustic performance.

Hughes, Christopher E.; Jeracki, Robert J.; Woodward, Richard P.; Miller, Christopher J.

2005-01-01

12

Influence of low-speed aerodynamic performance on airport community noise  

E-print Network

Properly assessing proposed aviation policies requires a thorough trade study of noise, emissions, fuel consumption, and cost. Aircraft low-speed aerodynamic performance is an important driver of all these impacts, and ...

March, Andrew I. (Andrew Irving)

2008-01-01

13

Experimental investigation of the aerodynamic noise radiated by a three-dimensional bluff body  

E-print Network

is caused by the development of aerodynamic structures from different parts of the vehicle (side mirrors noise reduction is an important aspect for the development of cars in the automotive industry a relevant subject for the last decades as car manufacturers are interested in reducing it. That noise

Paris-Sud XI, Université de

14

On aerodynamic noises radiated by the pantograph system of high-speed trains  

NASA Astrophysics Data System (ADS)

Pantograph system of high-speed trains become significant source of aerodynamic noise when travelling speed exceeds 300 km/h. In this paper, a hybrid method of non-linear acoustic solver (NLAS) and Ffowcs Williams-Hawkings (FW-H) acoustic analogy is used to predict the aerodynamic noise of pantograph system in this speed range. When the simulation method is validated by a benchmark problem of flows around a cylinder of finite span, we calculate the near flow field and far acoustic field surrounding the pantograph system. And then, the frequency spectra and acoustic attenuation with distance are analyzed, showing that the pantograph system noise is a typical broadband one with most acoustic power restricted in the medium-high frequency range from 200 Hz to 5 kHz. The aerodynamic noise of pantograph systems radiates outwards in the form of spherical waves in the far field. Analysis of the overall sound pressure level (OASPL) at different speeds exhibits that the acoustic power grows approximately as the 4th power of train speed. The comparison of noise reduction effects for four types of pantograph covers demonstrates that only case 1 can lessen the total noise by about 3 dB as baffles on both sides can shield sound wave in the spanwise direction. The covers produce additional aerodynamic noise themselves in the other three cases and lead to the rise of OASPLs.

Yu, Hua-Hua; Li, Jia-Chun; Zhang, Hui-Qin

2013-06-01

15

Measurement of aerodynamic noise and unsteady flow field around a symmetrical airfoil  

Microsoft Academic Search

The purpose of this paper is to study the physics of aerodynamic noise generation from the symmetrical airfoil of NACA 0018\\u000a in a uniform flow. The relationship between the noise spectrum and the unsteady flow field around the airfoil is studied in\\u000a an acoustic wind tunnel using flow visualization and PIV analysis. The discrete frequency noise was generated from the

N. Fujisawa

2002-01-01

16

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. 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. This topic in depth highlights some fun websites on the science of aerodynamics.The first site (1) provides some general information on aerodynamics. For those wanting a little more on the theory of aerodynamics, the University of Sydney has published this web textbook, Aerodynamics for Students (2). When people think of aerodynamics, they generally think of aviation and flight, which is explained on this site (3). Aerodynamics also has applications in sports, such as tennis, sailing and cycling. This website provides explanations for sports applications whether you are a beginner in the study of aerodynamics or an instructor (4). The next website reviews the aerodynamics of cycling and has a form that lets you Calculate the Aerodynamic Drag and Propulsive Power of a Bicyclist (5). The last site, AeroNet (6), is an interactive site designed to provide information about topics involved with aviation in a fun way for anyone casually interested in flight, someone thinking about aviation as a profession, or a student doing research for physics class.

17

Effects of Nozzle Geometry and Intermittent Injection of Aerodynamic Tab on Supersonic Jet Noise  

NASA Astrophysics Data System (ADS)

Effects of the nozzle geometry and intermittent injection of aerodynamic tabs on exhaust noise from a rectangular plug nozzle were investigated experimentally. In JAXA (Japan Aerospace Exploration Agency), a pre-cooled turbojet engine for an HST (Hypersonic transport) is planned. A 1/100-scaled model of the rectangular plug nozzle is manufactured, and the noise reduction performance of aerodynamic tabs, which is small air jet injection from the nozzle wall, was investigated. Compressed air is injected through the rectangular plug nozzle into the atmosphere at the nozzle pressure ratio of 2.7, which corresponds to the take-off condition of the vehicle. Aerodynamic tabs were installed at the sidewall ends, and 4 kinds of round nozzles and 2 kinds of wedge nozzles were applied. Using a high-frequency solenoid valve, intermittent gas injection is also applied. It is shown that, by use of wedge nozzles, the aerodynamic tab mass flow rate, necessary to gain 2.3dB reduction in OASPL (Overall sound pressure level), decreases by 29% when compared with round nozzles. It is also shown that, by use of intermittent injection, the aerodynamic tab mass flow rate, necessary to gain 2.3dB reduction in OASPL, decreases by about 40% when compared with steady injection. By combination of wedge nozzles and intermittent injection, the aerodynamic tab mass flow rate significantly decreases by 57% when compared with the conventional strategy.

Araki, Mikiya; Sano, Takayuki; Fukuda, Masayuki; Kojima, Takayuki; Taguchi, Hideyuki; Shiga, Seiichi; Obokata, Tomio

18

Comparison of Aerodynamic Noise Propagation Markus P. Rumpfkeil  

E-print Network

;CFD Farfield Ground Plane Nearfield Figure 1. Schematic of the propagation of aircraft pressure Miguel R. Visbal Air Force Research Laboratory, Wright-Patterson AFB, Ohio, 45433, USA In this paper and Motivation Airframe-generated noise is an important component of the total noise radiated from aircraft

Rumpfkeil, Markus Peer

19

Radiation from a double layer jet. [aerodynamic noise  

NASA Technical Reports Server (NTRS)

The aerodynamic radiation caused by two acoustic point sources located symmetrically on the sides of a double layer jet which produces a velocity discontinuity was examined, with attention given to the effect on the sound by the stream. Basic equations were defined in terms of wave propagation in the fluid in motion and a Fourier transformation. It was found that the radiation due to a point source on one side of the jet is enhanced by the presence of sound transmitted from the other side. The effect is expressed as a function of the reflection coefficient, wherein the reflections take place at the vortex interfaces separating the fluid in motion from the fluid at rest. The intensity patterns were determined to be kidney-shaped, lung-shaped, and heart-shaped, and characterized by a deep valley in the directivity pattern. The significance of the findings for STOL aircraft ejector thrust augmentation is mentioned.

Dash, R.

1983-01-01

20

Effects of Aerodynamic Tabs onExhaust Noise from a Rectangular Plug Nozzle  

NASA Astrophysics Data System (ADS)

Effects of aerodynamic tabs on exhaust noise from a rectangular plug nozzle were investigated experimentally. In JAXA (Japan Aerospace Explanation Agency), a pre-cooled turbojet engine for the 1st stage propulsion of a TSTO (Two stage to orbit) is planned. In the present study, a 1/100-scaled model of the rectangular plug nozzle for the pre-cooled turbojet engine is manufactured and the exhaust noise characteristics were investigated. Compressed air is injected through the rectangular plug nozzle into the atmosphere. The nozzle pressure ratio was set at 2.7, which corresponds to the take-off condition of the vehicle. Aerodynamic tabs were installed at the ramp end (Upper AT), the cowl end (Lower AT) and the sidewall end (Side AT). The SPL (Sound pressure level) was measured with a high-frequency microphone. Without AT, the sound spectrum has a broadband peak at which the SPL is around 105dB. For Lower and Side ATs, the OASPL (Overall SPL) of the exhaust noise decreases, especially around ramp end. At the maximum, the OASPL was reduced by 2.4dB with about 2% loss of the main jet total pressure at the cowl exit. It is shown that the aerodynamic tabs are effective in noise reduction in a rectangular plug nozzle.

Araki, Mikiya; Sano, Takayuki; Kojima, Takayuki; Taguchi, Hideyuki; Shiga, Seiichi; Obokata, Tomio

21

Aerodynamic Performance of Scale-Model Turbofan Outlet Guide Vanes Designed for Low Noise  

NASA Technical Reports Server (NTRS)

The design of effective new technologies to reduce aircraft propulsion noise is dependent on an understanding of the noise sources and noise generation mechanisms in the modern turbofan engine. In order to more fully understand the physics of noise in a turbofan engine, a comprehensive aeroacoustic wind tunnel test programs was conducted called the 'Source Diagnostic Test.' The text was cooperative effort between NASA and General Electric Aircraft Engines, as part of the NASA Advanced Subsonic Technology Noise Reduction Program. A 1/5-scale model simulator representing the bypass stage of a current technology high bypass ratio turbofan engine was used in the test. The test article consisted of the bypass fan and outlet guide vanes in a flight-type nacelle. The fan used was a medium pressure ratio design with 22 individual, wide chord blades. Three outlet guide vane design configurations were investigated, representing a 54-vane radial Baseline configuration, a 26-vane radial, wide chord Low Count configuration and a 26-vane, wide chord Low Noise configuration with 30 deg of aft sweep. The test was conducted in the NASA Glenn Research Center 9 by 15-Foot Low Speed Wind Tunnel at velocities simulating the takeoff and approach phases of the aircraft flight envelope. The Source Diagnostic Test had several acoustic and aerodynamic technical objectives: (1) establish the performance of a scale model fan selected to represent the current technology turbofan product; (2) assess the performance of the fan stage with each of the three distinct outlet guide vane designs; (3) determine the effect of the outlet guide vane configuration on the fan baseline performance; and (4) conduct detailed flowfield diagnostic surveys, both acoustic and aerodynamic, to characterize and understand the noise generation mechanisms in a turbofan engine. This paper addresses the fan and stage aerodynamic performance results from the Source Diagnostic Test.

Hughes, Christopher E.

2001-01-01

22

Holographic interferometry technique for rotary wing aerodynamics and noise  

NASA Technical Reports Server (NTRS)

The concepts of holography and holographic interferometry, as applied to the visualization and measurement of the three dimensional flow field near a rotor tip, are previewed, and initial experimental results of investigations of local shock structures and tip vortices behind the blade are presented. An additional method to visualize the flow in a three dimensional manner is demonstrated, and finally, a method to quantitatively measure the three dimensional flow, which will provide the necessary information to help improve helicopter performance and reduce noise, is introduced.

Kittleson, J. K.; Yu, Y. H.

1981-01-01

23

Aerodynamic Measurements of a Gulfstream Aircraft Model With and Without Noise Reduction Concepts  

NASA Technical Reports Server (NTRS)

Steady and unsteady aerodynamic measurements of a high-fidelity, semi-span 18% scale Gulfstream aircraft model are presented. The aerodynamic data were collected concurrently with acoustic measurements as part of a larger aeroacoustic study targeting airframe noise associated with main landing gear/flap components, gear-flap interaction noise, and the viability of related noise mitigation technologies. The aeroacoustic tests were conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the measurements were obtained with the model in landing configuration with the flap deflected at 39º and the main landing gear on and off. Data were acquired at Mach numbers of 0.16, 0.20, and 0.24. Global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Comparison of the present results with those acquired during a previous test shows a significant reduction in the lift experienced by the model. The underlying cause was traced to the likely presence of a much thicker boundary layer on the tunnel floor, which was acoustically treated for the present test. The steady and unsteady pressure fields on the flap, particularly in the regions of predominant noise sources such as the inboard and outboard tips, remained unaffected. It is shown that the changes in lift and drag coefficients for model configurations fitted with gear/flap noise abatement technologies fall within the repeatability of the baseline configuration. Therefore, the noise abatement technologies evaluated in this experiment have no detrimental impact on the aerodynamic performance of the aircraft model.

Neuhart, Dan H.; Hannon, Judith A.; Khorrami, Mehdi R.

2014-01-01

24

Effect of Trailing Edge Flow Injection on Fan Noise and Aerodynamic Performance  

NASA Technical Reports Server (NTRS)

An experimental investigation using trailing edge blowing for reducing fan rotor/guide vane wake interaction noise was completed in the NASA Glenn 9- by 15-foot Low Speed Wind Tunnel. Data were acquired to measure noise, aerodynamic performance, and flow features for a 22" tip diameter fan representative of modern turbofan technology. The fan was designed to use trailing edge blowing to reduce the fan blade wake momentum deficit. The test objective was to quantify noise reductions, measure impacts on fan aerodynamic performance, and document the flow field using hot-film anemometry. Measurements concentrated on approach, cutback, and takeoff rotational speeds as those are the primary conditions of acoustic interest. Data are presented for a 2% (relative to overall fan flow) trailing edge injection rate and show a 2 dB reduction in Overall Sound Power Level (OAPWL) at all fan test speeds. The reduction in broadband noise is nearly constant and is approximately 1.5 dB up to 20 kHz at all fan speeds. Measurements of tone noise show significant variation, as evidenced by reductions of up to 6 dB in the 2 BPF tone at 6700 rpm.: and increases of nearly 2 dB for the 4 BPF tone at approach speed. Aerodynamic performance measurements show the fan with 2 % injection has an overall efficiency that is comparable to the baseline fan and operates, as intended, with nearly the same pressure ratio and mass flow parameters. Hot-film measurements obtained at the approach operating condition indicate that mean blade wake filling in the tip region was not as significant as expected. This suggests that additional acoustic benefits could be realized if the trailing edge blowing could be modified to provide better filling of the wake momentum deficit. Nevertheless, the hot-film measurements indicate that the trailing edge blowing provided significant reductions in blade wake turbulence. Overall, these results indicate that further work may be required to fully understand the proper implementation of injecting flow at/near the trailing edge as a wake filling strategy. However, data do support the notion that noise reductions can be realized not only for tones but perhaps more importantly, also for broadband. Furthermore, the technique can be implemented without adversely effecting overall fan aerodynamic performance.

Fite, E. Brian; Woodward, Richard P.; Podboy, Gary G.

2006-01-01

25

Two-stage, low noise advanced technology fan. Volume 2: Aerodynamic data  

NASA Technical Reports Server (NTRS)

Aerodynamic data from static tests of a two-stage advanced technology fan designed to minimize noise are presented. Fan design conditions include delivery of 209.1kg/sec/sq m (42.85 lbm/sec/sq ft) specific corrected flow at an overall pressure ratio of 1.9 and an adiabatic efficiency of 85.3 percent. The 0.836m (2.74ft) diameter first stage rotor has a hub/tip ratio of 0.4 and 365.8m/sec (1200ft/sec) design tip speed. In addition to the moderate tip speed and pressure rise per stage, other noise control design features involve widely spaced blade rows and proper selection of blade-vane ratios. Aerodynamic data are presented for tests with unifrom and with hub and tip radially distorted inlet flow. Aerodynamic data are also presented for tests of this fan with acoustic treatments, including acoustically treated casing walls, a flowpath exit acoustic ring, and a translating centerbody sonic inlet device. A complete tabulation of the overall performance data, the blade element data, and the power spectral density information relating to turbulence levels generated by the sonic inlet obtained during these tests is included. For vol. 1, see N74-33789.

Harley, K. G.; Odegard, P. A.

1975-01-01

26

Effect of anisotropic turbulence on aerodynamic noise. [Lighthill theory mathematical model for axisymmetric turbulence  

NASA Technical Reports Server (NTRS)

A model based on Lighthill's theory for predicting aerodynamic noise from a turbulent shear flow is developed. This model is a generalization of the one developed by Ribner. It does not require that the turbulent correlations factor into space and time-dependent parts. It replaces his assumption of isotropic turbulence by the more realistic one of axisymmetric turbulence. In the course of the analysis, a hierarchy of equations is developed wherein each succeeding equation involves more assumptions than the preceding equation but requires less experimental information for its use. The implications of the model for jet noise are discussed. It is shown that for the particular turbulence data considered anisotropy causes the high-frequency self-noise to be beamed downstream.

Goldstein, M.; Rosenbaum, B.

1973-01-01

27

Study of aerodynamic noise in low supersonic operation of an axial flow compressor  

NASA Technical Reports Server (NTRS)

A study of compressor noise is presented, based upon supersonic, part-speed operation of a high hub/tip ratio compressor designed for spanwise uniformity of aerodynamic conditions, having straight cylindrical inlet and exit passages for acoustic simplicity. Acoustic spectra taken in the acoustically-treated inlet plenum, are presented for five operating points at each of two speeds, corresponding to relative rotor tip Mach numbers of about 1.01 and 1.12 (60 and 67 percent design speed). These spectra are analyzed for low and high frequency broadband noise, blade passage frequency noise, combination tone noise and "haystack' noise (a very broad peak somewhat below blade passage frequency, which is occasionally observed in engines and fan test rigs). These types of noise are related to diffusion factor, total pressure ratio, and relative rotor tip Mach number. Auxiliary measurements of fluctuating wall static pressures and schlieren photographs of upstream shocks in the inlet are also presented and related to the acoustic and performance data.

Arnoldi, R. A.

1972-01-01

28

Aerodynamic performance of a 1.20-pressure ratio fan stage designed for low noise  

NASA Technical Reports Server (NTRS)

The aerodynamic design and the overall blade element performance of a 51 centimeter diameter fan stage is presented. The stage was designed to minimize the noise generated by rotor stator interactions. The design pressure ratio was 1.20 at a flow of 30.6 kilograms per second and a rotor blade tip speed of 228.6 meters per second. At design speed the rotor peak efficiency was 0.935. The peak efficiency of the stage, however, was 0.824. The radial distribution of rotor performance parameters at peak efficiency and design speed indicated excellent agreement with design values.

Lewis, G. W., Jr.; Moore, R. D.

1976-01-01

29

Lobed Mixer Design for Noise Suppression: Plume, Aerodynamic and Acoustic Data. Volume 2  

NASA Technical Reports Server (NTRS)

A comprehensive database for the acoustic and aerodynamic characteristics of several model-scale lobe mixers of bypass ratio 5 to 6 has been created for mixed jet speeds up to 1080 ft per s at typical take-off (TO) conditions of small-to-medium turbofan engines. The flight effect was simulated for Mach numbers up to 0.3. The static thrust performance and plume data were also obtained at typical TO and cruise conditions. The tests were done at NASA Lewis anechoic dome and ASE's FluiDyne Laboratories. The effect of several lobe mixer and nozzle parameters, such as, lobe scalloping, lobe count, lobe penetration and nozzle length was examined in terms of flyover noise at constant altitude and also noise in the reference frame of the nozzle. This volume is divided into three parts: in the first two parts, we collate the plume survey data in graphical form (line, contour and surface plots) and analyze it; in part 3, we tabulate the aerodynamic data for the acoustics tests and the acoustic data in one-third octave band levels.

Mengle, Vinod G.; Baker, V. David; Dalton, William N.; Bridges, James (Technical Monitor)

2002-01-01

30

Lobed Mixer Design for Noise Suppression Acoustic and Aerodynamic Test Data Analysis  

NASA Technical Reports Server (NTRS)

A comprehensive database for the acoustic and aerodynamic characteristics of several model-scale lobe mixers of bypass ratio 5 to 6 has been created for mixed jet speeds up to 1080 ft/s at typical take-off (TO) conditions of small-to-medium turbofan engines. The flight effect was simulated for Mach numbers up to 0.3. The static thrust performance and plume data were also obtained at typical TO and cruise conditions. The tests were done at NASA Lewis anechoic dome and ASK's FluiDyne Laboratories. The effect of several lobe mixer and nozzle parameters, such as, lobe scalloping, lobe count, lobe penetration and nozzle length was examined in terms of flyover noise at constant altitude. Sound in the nozzle reference frame was analyzed to understand the source characteristics. Several new concepts, mechanisms and methods are reported for such lobed mixers, such as, "boomerang" scallops, "tongue" mixer, detection of "excess" internal noise sources, and extrapolation of flyover noise data from one flight speed to different flight speeds. Noise reduction of as much as 3 EPNdB was found with a deeply scalloped mixer compared to annular nozzle at net thrust levels of 9500 lb for a 29 in. diameter nozzle after optimizing the nozzle length.

Mengle, Vinod G.; Dalton, William N.; Boyd, Kathleen (Technical Monitor); Bridges, James (Technical Monitor)

2002-01-01

31

Interaction of aerodynamic noise with laminar boundary layers in supersonic wind tunnels  

NASA Technical Reports Server (NTRS)

The interaction between incoming aerodynamic noise and the supersonic laminar boundary layer is studied. The noise field is modeled as a Mach wave radiation field consisting of discrete waves emanating from coherent turbulent entities moving downstream within the supersonic turbulent boundary layer. The individual disturbances are likened to miniature sonic booms and the laminar boundary layer is staffed by the waves as the sources move downstream. The mean, autocorrelation, and power spectral density of the field are expressed in terms of the wave shapes and their average arrival rates. Some consideration is given to the possible appreciable thickness of the weak shock fronts. The emphasis in the interaction analysis is on the behavior of the shocklets in the noise field. The shocklets are shown to be focused by the laminar boundary layer in its outer region. Borrowing wave propagation terminology, this region is termed the caustic region. Using scaling laws from sonic boom work, focus factors at the caustic are estimated to vary from 2 to 6 for incoming shocklet strengths of 1 to .01 percent of the free stream pressure level. The situation regarding experimental evidence of the caustic region is reviewed.

Schopper, M. R.

1984-01-01

32

ACTIVE FLOW CONTROL TO REDUCE THE TIP CLEARANCE NOISE AND IMPROVE THE AERODYNAMIC PERFORMANCE OF AXIAL TURBOMACHINES PRESENTED AT FAN NOISE 2003  

Microsoft Academic Search

SUMMARY This paper presents experimental results on active flow control in the impeller blade tip region to reduce the tip clearance noise and improve the aerodynamic performance of axial turbomachines. Air is injected steadily into the tip clearance gap between the tip of the impeller blades and the casing. Slit nozzles are used to inject different mass flow rates at

Lars NEUHAUS; Wolfgang NEISE

33

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

34

Computation of interactional aerodynamics for noise prediction of heavy lift rotorcraft  

NASA Astrophysics Data System (ADS)

Many computational tools are used when developing a modern helicopter. As the design space is narrowed, more accurate and time-intensive tools are brought to bear. These tools are used to determine the effect of a design decision on the performance, handling, stability and efficiency of the aircraft. One notable parameter left out of this process is acoustics. This is due in part to the difficulty in making useful acoustics calculations that reveal the differences between various design configurations. This thesis presents a new approach designed to bridge the gap in prediction capability between fast but low-fidelity Lagrangian particle methods, and slow but high-fidelity Eulerian computational fluid dynamics simulations. A multi-pronged approach is presented. First, a simple flow solver using well-understood and tested flow solution methodologies is developed specifically to handle bodies in arbitrary motion. To this basic flow solver two new technologies are added. The first is an Immersed Boundary technique designed to be tolerant of geometric degeneracies and low-resolution grids. This new technique allows easy inclusion of complex fuselage geometries at minimal computational cost, improving the ability of a solver to capture the complex interactional aerodynamic effects expected in modern rotorcraft design. The second new technique is an extension of a concept from flow visualization where the motion of tip vortices are tracked through the solution using massless particles convecting with the local flow. In this extension of that concept, the particles maintain knowledge of the expected and actual vortex strength. As a post-processing step, when the acoustic calculations are made, these particles are used to augment the loading noise calculation and reproduce the highly-impulsive character of blade-vortex interaction noise. In combination these new techniques yield a significant improvement to the state of the art in rotorcraft blade-vortex interaction noise prediction.

Hennes, Christopher C.

35

Effect of Two Advanced Noise Reduction Technologies on the Aerodynamic Performance of an Ultra High Bypass Ratio Fan  

NASA Technical Reports Server (NTRS)

A wind tunnel experiment was conducted in the NASA Glenn Research Center anechoic 9- by 15-Foot Low-Speed Wind Tunnel to investigate two new advanced noise reduction technologies in support of the NASA Fundamental Aeronautics Program Subsonic Fixed Wing Project. The goal of the experiment was to demonstrate the noise reduction potential and effect on fan model performance of the two noise reduction technologies in a scale model Ultra-High Bypass turbofan at simulated takeoff and approach aircraft flight speeds. The two novel noise reduction technologies are called Over-the-Rotor acoustic treatment and Soft Vanes. Both technologies were aimed at modifying the local noise source mechanisms of the fan tip vortex/fan case interaction and the rotor wake-stator interaction. For the Over-the-Rotor acoustic treatment, two noise reduction configurations were investigated. The results showed that the two noise reduction technologies, Over-the-Rotor and Soft Vanes, were able to reduce the noise level of the fan model, but the Over-the-Rotor configurations had a significant negative impact on the fan aerodynamic performance; the loss in fan aerodynamic efficiency was between 2.75 to 8.75 percent, depending on configuration, compared to the conventional solid baseline fan case rubstrip also tested. Performance results with the Soft Vanes showed that there was no measurable change in the corrected fan thrust and a 1.8 percent loss in corrected stator vane thrust, which resulted in a total net thrust loss of approximately 0.5 percent compared with the baseline reference stator vane set.

Hughes, Christoper E.; Gazzaniga, John A.

2013-01-01

36

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

NASA Technical Reports Server (NTRS)

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.

1991-01-01

37

Piloted Simulation Study of the Effects of High-Lift Aerodynamics on the Takeoff Noise of a Representative High-Speed Civil Transport  

NASA Technical Reports Server (NTRS)

As part of an effort between NASA and private industry to reduce airport-community noise for high-speed civil transport (HSCT) concepts, a piloted simulation study was initiated for the purpose of predicting the noise reduction benefits that could result from improved low-speed high-lift aerodynamic performance for a typical HSCT configuration during takeoff and initial climb. Flight profile and engine information from the piloted simulation were coupled with the NASA Langley Aircraft Noise Prediction Program (ANOPP) to estimate jet engine noise and to propagate the resulting source noise to ground observer stations. A baseline aircraft configuration, which also incorporated different levels of projected improvements in low-speed high-lift aerodynamic performance, was simulated to investigate effects of increased lift and lift-to-drag ratio on takeoff noise levels. Simulated takeoff flights were performed with the pilots following a specified procedure in which either a single thrust cutback was performed at selected altitudes ranging from 400 to 2000 ft, or a multiple-cutback procedure was performed where thrust was reduced by a two-step process. Results show that improved low-speed high-lift aerodynamic performance provides at least a 4 to 6 dB reduction in effective perceived noise level at the FAA downrange flyover measurement station for either cutback procedure. However, improved low-speed high-lift aerodynamic performance reduced maximum sideline noise levels only when using the multiple-cutback procedures.

Glaab, Louis J.; Riley, Donald R.; Brandon, Jay M.; Person, Lee H., Jr.; Glaab, Patricia C.

1999-01-01

38

The Effect of Bypass Nozzle Exit Area on Fan Aerodynamic Performance and Noise in a Model Turbofan Simulator  

NASA Technical Reports Server (NTRS)

The design of effective new technologies to reduce aircraft propulsion noise is dependent on identifying and understanding the noise sources and noise generation mechanisms in the modern turbofan engine, as well as determining their contribution to the overall aircraft noise signature. Therefore, a comprehensive aeroacoustic wind tunnel test program was conducted called the Fan Broadband Source Diagnostic Test as part of the NASA Quiet Aircraft Technology program. The test was performed in the anechoic NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel using a 1/5 scale model turbofan simulator which represented a current generation, medium pressure ratio, high bypass turbofan aircraft engine. The investigation focused on simulating in model scale only the bypass section of the turbofan engine. The test objectives were to: identify the noise sources within the model and determine their noise level; investigate several component design technologies by determining their impact on the aerodynamic and acoustic performance of the fan stage; and conduct detailed flow diagnostics within the fan flow field to characterize the physics of the noise generation mechanisms in a turbofan model. This report discusses results obtained for one aspect of the Source Diagnostic Test that investigated the effect of the bypass or fan nozzle exit area on the bypass stage aerodynamic performance, specifically the fan and outlet guide vanes or stators, as well as the farfield acoustic noise level. The aerodynamic performance, farfield acoustics, and Laser Doppler Velocimeter flow diagnostic results are presented for the fan and four different fixed-area bypass nozzle configurations. The nozzles simulated fixed engine operating lines and encompassed the fan stage operating envelope from near stall to cruise. One nozzle was selected as a baseline reference, representing the nozzle area which would achieve the design point operating conditions and fan stage performance. The total area change from the smallest to the largest nozzle was 12.9 percent of the baseline nozzle area. The results will show that there are significant changes in aerodynamic performance and farfield acoustics as the fan nozzle area is increased. The weight flow through the fan model increased between 7 and 9 percent, the fan and stage pressure dropped between 8 and 10 percent, and the adiabatic efficiency increased between 2 and 3 percent--the magnitude of the change dependent on the fan speed. Results from force balance measurements of fan and outlet guide vane thrust will show that as the nozzle exit area is increased the combined thrust of the fan and outlet guide vanes together also increases, between 2 and 3.5 percent, mainly due to the increase in lift from the outlet guide vanes. In terms of farfield acoustics, the overall sound power level produced by the fan stage dropped nearly linearly between 1 dB at takeoff condition and 3.5 dB at approach condition, mainly due to a decrease in the broadband noise levels. Finally, fan swirl angle survey and Laser Doppler Velocimeter mean velocity and turbulence data obtained in the fan wake will show that the swirl angles and turbulence levels within the wake decrease as the fan nozzle area increases, which helps to explain the drop in the fan broadband noise at all fan speeds.

Hughes, Christopher E.; Podboy, Gary, G.; Woodward, Richard P.; Jeracki, Robert, J.

2013-01-01

39

An experimental means of reducing the overall aerodynamic noise level in a 0.25 m transonic wind tunnel test section  

Microsoft Academic Search

The employment of a ventilated test section wall configuration represents a common approach for achieving transonic Mach numbers in existing transonic wind tunnels. However, the transonic test section walls may produce intensive acoustic disturbances. Measurements performed in a 0.25 m perforated test section indicated a high level of aerodynamic noise. It was found that a screen is quite effective in

B. Medved; D. Prica

1986-01-01

40

Aerodynamic investigations of noise-reducing high-lift systems for passenger transport aircraft.  

E-print Network

?? This diploma thesis captures the three-dimensional implementation of noise-reducing high-liftsystems. A parametric CAD model is developed for the FNG aircraft and different high-lift configurationsare… (more)

Hövelmann, Andreas

2011-01-01

41

Design of low noise airfoil with high aerodynamic performance for use on small wind turbines  

Microsoft Academic Search

Wind power is one of the most reliable renewable energy sources and internationally installed capacity is increasing radically\\u000a every year. Although wind power has been favored by the public in general, the problem with the impact of wind turbine noise\\u000a on people living in the vicinity of the turbines has been increased. Low noise wind turbine design is becoming more

Taehyung Kim; Seungmin Lee; Hogeon Kim; Soogab Lee

2010-01-01

42

Unified aeroacoustics analysis for high speed turboprop aerodynamics and noise. Volume 2: Development of theory for wing shielding  

NASA Technical Reports Server (NTRS)

A unified theory for aerodynamics and noise of advanced turboprops is presented. The theory and a computer code developed for evaluation at the shielding benefits that might be expected by an aircraft wing in a wing-mounted propeller installation are presented. Several computed directivity patterns are presented to demonstrate the theory. Recently with the advent of the concept of using the wing of an aircraft for noise shielding, the case of diffraction by a surface in a flow has been given attention. The present analysis is based on the case of diffraction of no flow. By combining a Galilean and a Lorentz transform, the wave equation with a mean flow can be reduced to the ordinary equation. Allowance is also made in the analysis for the case of a swept wing. The same combination of Galilean and Lorentz transforms lead to a problem with no flow but a different sweep. The solution procedures for the cases of leading and trailing edges are basically the same. Two normalizations of the solution are given by the computer program. FORTRAN computer programs are presented with detailed documentation. The output from these programs compares favorably with the results of other investigators.

Amiet, R. K.

1991-01-01

43

Flap noise and aerodynamic results for model QCSEE over-the-wing configurations. [Quiet Clean Short-haul Experimental Engine program  

NASA Technical Reports Server (NTRS)

Noise spectra in three dimensions and aerodynamic data were measured for a model of the NASA QCSEE (Quiet Clean Short-Haul Experimental Engine) over-the-wing configuration. The effects of flap length, nozzle exhaust velocity, and nozzle geometry were determined using a single nozzle and wing-flap segment. Related tests indicated that the scaled-up model data would be representative of full scale flap noise with the QCSEE engine. The scaled-up QCSEE model data imply that the noise goal will be very nearly attained.

Olsen, W.; Burns, R.; Groesbeck, D.

1977-01-01

44

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

45

Ris-PhD-Report Wind Turbines: Unsteady Aerodynamics and  

E-print Network

Risø-PhD-Report Wind Turbines: Unsteady Aerodynamics and Inflow Noise Brian Riget Broe Risø-PhD-47 Title: Wind Turbines: Unsteady Aerodynamics and Inflow Noise Division: Wind Energy Division Risø-PhD-47(EN) December 2009 Abstract (max. 2000 char.): Aerodynamical noise from wind turbines due

46

Noise  

Microsoft Academic Search

The proliferation of DNA sequence data has generated a concern about the effects of “noise” on phylogeny reconstruction. This concern has led to various recommendations for weighting schemes and for separating data types prior to analysis. A new technique is explored to examine directly how noise influences the stability of parsimony reconstruction. By appending purely random characters onto a matrix

John W Wenzel; Mark E Siddall

1999-01-01

47

Aerodynamic and Acoustic Optimization for Fan Flow Deflection  

E-print Network

Aerodynamic and Acoustic Optimization for Fan Flow Deflection Andrew D. Johnson1 , Juntao Xiong2 reduction of noise perceived by the community while minimizing aerodynamic losses. An adjoint method employs aerodynamic deflectors to direct the fan flow of a separate-flow nozzle downward with respect

Papamoschou, Dimitri

48

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

49

Active Control to Improve the Aerodynamic Performance and Reduce the Tip Clearance Noise of Axial Turbomachines with Steady Air Injection into the Tip Clearance Gap  

Microsoft Academic Search

The secondary flow over the impeller blade tips of axial fans is important for the aerodynamic and acoustic performance of\\u000a the fans. Pressure coefficient and efficiency drop, and the usable range of the performance characteristic is diminished as\\u000a the rotor flow stalls at higher flow rates. By applying active flow control in the tip region of the impeller, it is

L. Neuhaus; W. Neise

50

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  

NASA Astrophysics Data System (ADS)

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 structural geometries for the lowest noise. Among the associated parameters which define USB-PHLS configurations, (1) the location relative to wing/flap and the shape of the exhaust jet nozzle and (2) flow attachment devices are important parameters. Flow characteristics dependence on these parameters and PHLS noise were also obtained. From far field noise spectra overall sound pressure level dependence on jet velocity and coherence across near field surface pressure, it was concluded tht the flap trailing edge noise was the most predominant noise source. Several acoustically treated flaps and serrated trailing edge design techniques were applied to attenuate edge noise.

Maita, M.; Shindo, S.

1981-10-01

51

Aerodynamic noise generated by jet wing/flap interactions of the external USB configuration of STOL aircraft. Part 2: Full scale model experiment using FJR710 turbofan engine  

NASA Astrophysics Data System (ADS)

Acoustic characteristics of the external upper surface blowing (USB) concept of a propulsive lift configuration were studied by full scale model static experiments. Test components included an FJR710 turbofan engine with an acoustically treated nacelle and a USB wing/flap assembly. These were utilized in conjunction with the ground verification testing of the propulsive systems of the National Aerospace Laboratory Quiet STOL Research Aircraft. Results were compared with the previous 8% scale cold flow model data. The defect of shielding provided by the wing/flap surface on aftradiated turbofan engine noise was studied and some attempts were made to reduce USB noise.

Maita, M.; Shindo, S.; Nakayama, S.; Matsuki, M.; Torisaki, T.; Morita, M.; Yoshida, A.; Takeda, K.; Sekine, S.; Kondo, H.

1981-10-01

52

Fluid-structure interaction and aerodynamics damping; Proceedings of the Tenth Biennial Conference on Mechanical Vibration and Noise, Cincinnati, OH, September 10-13, 1985  

Microsoft Academic Search

The response of a two-layer elastic coating to pressure disturbances from a turbulent boundary layer is considered along with the application of the finite element method in the calculation of transmission loss of flat and curved panels, the application of various solution techniques to the calculation of transonic flutter boundaries, and noise transmission of double wall composite shells. Other topics

E. H. Dowell; M. K. Au-Yang

1985-01-01

53

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

54

5th International Meeting Wind Turbine Noise  

E-print Network

1 5th International Meeting on Wind Turbine Noise Denver 28 ­ 30 August 2013 Wind Turbine Noise Broadband noise generated aerodynamically is the dominant noise source for a modern wind turbine(Brooks et, clean energy. While profiting from wind energy, the noise produced by a modern wind turbine becomes

Paris-Sud XI, Université de

55

Aerodynamics of road vehicles  

SciTech Connect

This introduction to aerodynamic aspects of motor vehicle design will be of use both to vehicle designers and students of automobile engineering. Content covers vehicle systems, ventilation and aerodynamic design to reduce drag and increase stability of cars, commercial vehicles and PSVs. Topics considered include automobile aerodynamics; some fundamentals of fluid mechanics; performance of cars and light vans; aerodynamic drag of passenger cars; driving stability in sidewinds; operation, safety and comfort; high-performance vehicle aerodynamics; commercial vehicles; engine cooling systems; heating, ventilation and air conditioning of motor vehicles; wind tunnels for automobile aerodynamics; measuring and testing techniques; and numerical methods for computation of flow around road vehicles.

Hucho, W.H.

1987-01-01

56

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

Microsoft Academic Search

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

F. Bossa; R. Gualdi

1981-01-01

57

Classical Aerodynamic Theory  

NASA Technical Reports Server (NTRS)

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

Jones, R. T. (compiler)

1979-01-01

58

NASA aerodynamics program  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

59

Aerodynamics Antony Jameson  

E-print Network

Chapter 11 Aerodynamics Antony Jameson Stanford University, Stanford, CA, USA 1 Focus Multidimensional Domains 359 6 Time-stepping Schemes 365 7 Aerodynamic Shape Optimization 379 8 Related Chapters 400 Acknowledgment 400 References 400 1 FOCUS AND HISTORICAL BACKGROUND 1.1 Classical aerodynamics

Jameson, Antony

60

Aerodynamics. [Numerical simulation using supercomputers  

SciTech Connect

A projection is made of likely improvements in the economics of commercial aircraft operation due to developments in aerodynamics in the next half-century. Notable among these improvements are active laminar flow control techniques' application to third-generation SSTs, in order to achieve an L/D value of about 20; this is comparable to current subsonic transports, and has the further consequence of reducing cabin noise. Wave-cancellation systems may also be used to eliminate sonic boom overpressures, and rapid-combustion systems may be able to eliminate all pollutants from jet exhausts other than CO/sub 2/.

Graves, R.A. Jr.

1988-01-01

61

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

62

Aerodynamics for Students  

NSDL National Science Digital Library

For those wanting a little more on the theory of aerodynamics, the University of Sydney has published this web textbook, "Aerodynamics for Students". In addition to information on fluid dynamics, flight theory, gas dynamics, propulsion, aircraft performance, and aeroelasticity, the textbook also includes data tables, computer programs, and simulations to aid in the study and understanding of aerodynamics. This textbook is a great resource for undergraduates studying engineering.

2007-12-10

63

Aerodynamic Requirements for BVI Noise Control  

NASA Technical Reports Server (NTRS)

As a rotor blade moves through the air, it sheds vortices. These vortices shed along the length of the blade over time form the wake. The strongest vortices of the wake are those trailing from the tip of the blade. When a rotating blade system moves under certain operating conditions, each blade will impinge on the tip vortices shed by itself or other blades. This impingement is called a blade-vortex interaction, or BVI. Although the blade and trailing tip vortices interact with many different orientations, one of the two extremes, either parallel or perpendicular interaction, is usually modelled. In a perpendicular interaction, the portion of the blade that is actually interacting with the travelling vortex at any given time is very small. A parallel interaction, however, has the largest concurrent interaction with the blade, as a result this case is given the most attention. One of the most commonly studied occurrences of blade-vortex interactions is associated with low-speed descending rotorcraft flight. BVI occur when the tip vortices shed by the blades intersect the plane of the rotor. BVI cause local pressure changes over the blades which are responsible, in part, for the acoustic signature of the rotorcraft. The local pressure changes also cause vibrations which lead to fatigue of both the blades and the mechanical components driving the blades.

Wells, Valana L.

1996-01-01

64

Aerodynamics of sounding rockets at supersonic speeds  

NASA Astrophysics Data System (ADS)

This dissertation presents a practical and low cost method of computing the aerodynamic characteristics of vehicles such as sounding rockets, high speed bombs, projectiles and guided missiles in supersonic flight. The vehicle configuration consists of a slender axisymmetric body with a conical or ogive noise, cylinders, shoulders and boattails, if any, and have sets of two, three or four fins. Geometry of the fin cross section can be single wedge, double wedge, modified single wedge or modified double wedge. First the aerodynamics of the fins and the body are analyzed separately; then fin body and fore and aft fin interferences are accounted for when they are combined to form the total vehicle. Results and formulas documented in this work are the basis of the supersonic portion of the Theoretical Aerodynamic Derivatives (TAD) computer program operating at the NASA Goddard Space Flight Center.

Vira, N. R.

65

High-lift aerodynamics: Prospects and plans  

NASA Technical Reports Server (NTRS)

The emergence of high-lift aerodynamics is reviewed as one of the key technologies to the development of future subsonic transport aircraft. Airport congestion, community noise, economic competitiveness, and safety - the drivers that make high-lift an important technology - are discussed. Attention is given to the potentially synergistic integration of high-lift aerodynamics with two other advanced technologies: ultra-high bypass ratio turbofan engines and hybrid laminar flow control. A brief review of the ongoing high-lift research program at Ames Research Center is presented. Suggestions for future research directions are made with particular emphasis on the development and validation of computational codes and design methods. It is concluded that the technology of high-lift aerodynamics analysis and design should move boldly into the realm of high Reynolds number, three-dimensional flows.

Olson, Lawrence E.

1992-01-01

66

Preconditioning Methods for Multidimensional Aerodynamics  

E-print Network

Preconditioning Methods for Multidimensional Aerodynamics E. Turkel School of Mathematical Sciences of Design Aerodynamics Braunschweig, Germany 1 #12; Contents 1 Introduction 5 1.1 General requirements

Turkel, Eli

67

Uncertainty in Computational Aerodynamics  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

68

Unsteady transonic aerodynamics  

SciTech Connect

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

Nixon, D.

1989-01-01

69

Fan noise and performance  

NASA Technical Reports Server (NTRS)

Tradeoffs between aerodynamic and acoustic properties of various fan configurations led to the selection of a variety of fans that produce noise levels in the range of 100 to 120 PNdb. Fan configuration and design pressure ratio required for specific mission operations depend in part on the type of mission to be performed. Noise data obtained for single-stage low speed fans, single-stage high speed fans, and two-stage fan engines are presented in table form.

Kramer, J. J.; Hartmann, M. J.; Leonard, B. R.; Klapproth, J. F.; Sofrin, T. G.

1972-01-01

70

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

71

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

72

Fundamentals of Modern Unsteady Aerodynamics  

E-print Network

Fundamentals of Modern Unsteady Aerodynamics U. Gulcat Springer, Tiergartenstrasse 17, D-69121 covers the modern topics on unsteady aerodynamics. The classical chapters mostly refer to the aerodynamic, different sorts of wing rock and flapping wing aerodynamics. The so-called classical topics can be found

Nagurka, Mark L.

73

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

74

Transonic aerodynamic design experience  

NASA Technical Reports Server (NTRS)

Advancements have occurred in transonic numerical simulation that place aerodynamic performance design into a relatively well developed status. Efficient broad band operating characteristics can be reliably developed at the conceptual design level. Recent aeroelastic and separated flow simulation results indicate that systematic consideration of an increased range of design problems appears promising. This emerging capability addresses static and dynamic structural/aerodynamic coupling and nonlinearities associated with viscous dominated flows.

Bonner, E.

1989-01-01

75

High speed helicopter noise sources  

NASA Technical Reports Server (NTRS)

The state-of-the art of helicopter rotor impulsive noise is reviewed. A triangulation technique for locating impulsive noise sources is developed using once-per-rev index signals as time references. A computer program (INSL) was written implementing this technique. Applying triangulation to the full-scale UH-1 noise data of NASA/Ames Research Center 40- by 80-Foot Wind Tunnel, three different noise sources are found on the rotor disk. The primary sources of thickness noise are in the second quadrant and on the advancing side of rotor disk. Two aerodynamic sources due to blade/vortex interaction are found in the first quadrant.

Lee, A.

1977-01-01

76

Potential impacts of advanced aerodynamic technology on air transportation system productivity  

NASA Technical Reports Server (NTRS)

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

Bushnell, Dennis M. (editor)

1994-01-01

77

Future Challenges and Opportunities in Aerodynamics  

NASA Technical Reports Server (NTRS)

Investments in aeronautics research and technology have declined substantially over the last decade, in part due to the perception that technologies required in aircraft design are fairly mature and readily available. This perception is being driven by the fact that aircraft configurations, particularly the transport aircraft, have evolved only incrementally, over last several decades. If however, one considers that the growth in air travel is expected to triple in the next 20 years, it becomes quickly obvious that the evolutionary development of technologies is not going to meet the increased demands for safety, environmental compatibility, capacity, and economic viability. Instead, breakthrough technologies will he required both in traditional disciplines of aerodynamics, propulsion, structures, materials, controls, and avionics as well as in the multidisciplinary integration of these technologies into the design of future aerospace vehicles concepts. The paper discusses challenges and opportunities in the field of aerodynamics over the next decade. Future technology advancements in aerodynamics will hinge on our ability, to understand, model, and control complex, three-dimensional, unsteady viscous flow across the speed range. This understanding is critical for developing innovative flow and noise control technologies and advanced design tools that will revolutionize future aerospace vehicle systems and concepts. Specifically, the paper focuses on advanced vehicle concepts, flow and noise control technologies, and advanced design and analysis tools.

Kumar, Ajay; Hefner, Jerry N.

2000-01-01

78

OPTIMALLY DESIGNED PROPELLERS CONSTRAINED BY NOISE (BLADE, SOUND, AIRCRAFT)  

Microsoft Academic Search

A design tool is developed that will produce an optimum geometry for a given trade-off between noise and performance. A vortex lattice model is used for the aerodynamics and a subsonic compact source model for the noise analysis. Optimizing the twist, chord and sweep distributions produced blades with favorable tradeoffs between noise and performance. The techniques used for noise reduction

CHRISTOPHER JOHN MILLER

1984-01-01

79

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

80

Darrieus rotor aerodynamics  

SciTech Connect

Darrieus wind turbines are relatively simple devices. Fixed geometry blades, usually only two or three in number, rotate about a vertical axis providing power to ground mounted power conversion or absorption machinery. No yaw control or power regulation systems are required. This simplicity, however, does not extend to the rotor's aerodynamics. The blade elements travel along circular paths through air whose relative speed and direction are constantly changing. The blade elements operate both unstalled and stalled with aerodynamic stall providing the rotor's inherent power regulation. The blade elements encounter their own wakes and those generated by other elements. These features combine to cause the thorough analysis of Darrieus rotor aerodynamics to be a challenging undertaking.

Klimas, P.C.

1981-01-01

81

High speed civil transport aerodynamic optimization  

NASA Technical Reports Server (NTRS)

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

Ryan, James S.

1994-01-01

82

CFD research, parallel computation and aerodynamic optimization  

NASA Technical Reports Server (NTRS)

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

Ryan, James S.

1995-01-01

83

Noise and noise abatement in fans and blowers: A review  

NASA Astrophysics Data System (ADS)

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 are discussed with respect to the noise radiated from different parts of a fan, e.g. from the fan inlet or outlet, from the fan casing, from the fan as a whole, and to the noise radiated into ducts connected to the fan. Finally, considerations are made, for which classes of fans noise standards can be defined to characterize the noise emission of the various fan types.

Neise, W.

1980-03-01

84

Aerodynamics for Students  

NSDL National Science Digital Library

This Web site serves as an online aerodynamics textbook for college students. Offered by the department of Aerospace, Mechanical, and Mechatronic Engineering at the University of Sydney, the material is divided into several main categories. These include fluid mechanics, aerodynamics, gasdynamics, aircraft performance, and propulsion. Each of these sections has many specific topics that are discussed in detail. There are MATLAB, Excel, and FORTRAN files and data sheets that accompany the reading, but they are best used as reference and are not needed to understand most of the material.

1995-01-01

85

Aeroacoustics and aerodynamic performance of a rotor with flatback airfoils.  

SciTech Connect

The aerodynamic performance and aeroacoustic noise sources of a rotor employing flatback airfoils have been studied in field test campaign and companion modeling effort. The field test measurements of a sub-scale rotor employing nine meter blades include both performance measurements and acoustic measurements. The acoustic measurements are obtained using a 45 microphone beamforming array, enabling identification of both noise source amplitude and position. Semi-empirical models of flatback airfoil blunt trailing edge noise are developed and calibrated using available aeroacoustic wind tunnel test data. The model results and measurements indicate that flatback airfoil noise is less than drive train noise for the current test turbine. It is also demonstrated that the commonly used Brooks, Pope, and Marcolini model for blunt trailing edge noise may be over-conservative in predicting flatback airfoil noise for wind turbine applications.

Paquette, Joshua A.; Barone, Matthew Franklin; Christiansen, Monica (Pennsylvania State University, State College, PA); Simley, Eric (University of Colorado, Boulder, CO)

2010-06-01

86

TIMEINTEGRATION METHODS IN COMPUTATIONAL AERODYNAMICS  

E-print Network

' $ TIME­INTEGRATION METHODS IN COMPUTATIONAL AERODYNAMICS Antony Jameson Department of Aeronautics methods for unsteady problems 4. Conclusions & % #12;' $ Some Examples of Aerodynamic Calculations flow & % #12;' $ Aerodynamic Flow computations AIRPLANE DENSITY from 0.6250 to 1.1000 AIRPLANE CP from

Stanford University

87

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

88

AEROSPACE SCIENCES Applied aerodynamics  

E-print Network

was made in the application of plasma flow-control concepts to practical actu- ators. Under an Air Force labs, and academia in the development of flow-control concepts, novel configuration aerodynamic and the Air Force Research Laboratory (AFRL) to gather information on stability and flight control

Xu, Kun

89

Advanced propeller aerodynamic analysis  

NASA Technical Reports Server (NTRS)

The analytical approaches as well as the capabilities of three advanced analyses for predicting propeller aerodynamic performance are presented. It is shown that two of these analyses use a lifting line representation for the propeller blades, and the third uses a lifting surface representation.

Bober, L. J.

1980-01-01

90

Wind turbine wake aerodynamics  

Microsoft Academic Search

The aerodynamics of horizontal axis wind turbine wakes is studied. The contents is directed towards the physics of power extraction by wind turbines and reviews both the near and the far wake region. For the near wake, the survey is restricted to uniform, steady and parallel flow conditions, thereby excluding wind shear, wind speed and rotor setting changes and yawed

L. J. Vermeer; J. N. Sørensen; A. Crespo

2003-01-01

91

Fitting aerodynamics and propulsion into the puzzle  

NASA Technical Reports Server (NTRS)

The development of an airbreathing single-stage-to-orbit vehicle, in particular the problems of aerodynamics and propulsion integration, is examined. The boundary layer transition on constant pressure surfaces at hypersonic velocities, and the effects of noise on the transition are investigated. The importance of viscosity, real-gas effects, and drag at hypersonic speeds is discussed. A propulsion system with sufficient propulsive lift to enhance the performance of the vehicle is being developed. The difficulties of engine-airframe integration are analyzed.

Johnston, Patrick J.; Whitehead, Allen H., Jr.; Chapman, Gary T.

1987-01-01

92

Pylon Based Jet Noise Suppressors  

Microsoft Academic Search

This investigation examined the potential of pylon-based, deployable flaps to reduce noise of separate-flow turbofan engines with bypass ratio 8. The main function of the flap deflectors is to thicken the low-speed region surrounding the core jet in the downward and sideline directions. The study encompassed acoustic measurements, noise source imaging, mean velocity surveys, and aerodynamic estimates. Three types of

Dimitri Papamoschou

2008-01-01

93

Survey of lift-fan aerodynamic technology  

NASA Technical Reports Server (NTRS)

Representatives of NASA Ames Research Center asked that a summary of technology appropriate for lift-fan powered short takeoff/vertical landing (STOVL) aircraft be prepared so that new programs could more easily benefit from past research efforts. This paper represents one of six prepared for that purpose. The authors have conducted or supervised the conduct of research on lift-fan powered STOVL designs and some of their important components for decades. This paper will first address aerodynamic modeling requirements for experimental programs to assure realistic, trustworthy results. It will next summarize the results or efforts to develop satisfactory specialized STOVL components such as inlets and flow deflectors. It will also discuss problems with operation near the ground, aerodynamics while under lift-fan power, and aerodynamic prediction techniques. Finally, results of studies to reduce lift-fan noise will be presented. The paper will emphasize results from large scale experiments, where available, for reasons that will be brought out in the discussion. Some work with lift-engine powered STOVL aircraft is also applicable to lift-fan technology and will be presented herein. Small-scale data will be used where necessary to fill gaps.

Hickey, David H.; Kirk, Jerry V.

1993-01-01

94

NOISE GENERATION OF BLADE–VORTEX RESONANCE  

Microsoft Academic Search

A numerical study of the aerodynamic noise generated when an airfoil\\/blade in a uniform flow is excited by an oncoming vortical flow is reported. The vortical flow is modelled by a series of flow convected discrete vortices representative of a Karman vortex street. Such noise generation problems due to fluid–blade interaction occur in helicopter rotor and turbomachinery blades. Interactions with

R. C. K. LEUNG; R. M. C. SO

2001-01-01

95

Noise Generation of Blade-Vortex Resonance  

Microsoft Academic Search

A numerical study of the aerodynamic noise generated when an airfoil\\/blade in a uniform flow is excited by an oncoming vortical flow is reported. The vortical flow is modelled by a series of flow convected discrete vortices representative of a Karman vortex street. Such noise generation problems due to fluid-blade interaction occur in helicopter rotor and turbomachinery blades. Interactions with

R. C. K. Leung; R. M. C. So

2001-01-01

96

Aircraft noise prediction program theoretical manual: Rotorcraft System Noise Prediction System (ROTONET), part 4  

NASA Technical Reports Server (NTRS)

This document describes the theoretical methods used in the rotorcraft noise prediction system (ROTONET), which is a part of the NASA Aircraft Noise Prediction Program (ANOPP). The ANOPP code consists of an executive, database manager, and prediction modules for jet engine, propeller, and rotor noise. The ROTONET subsystem contains modules for the prediction of rotor airloads and performance with momentum theory and prescribed wake aerodynamics, rotor tone noise with compact chordwise and full-surface solutions to the Ffowcs-Williams-Hawkings equations, semiempirical airfoil broadband noise, and turbulence ingestion broadband noise. Flight dynamics, atmosphere propagation, and noise metric calculations are covered in NASA TM-83199, Parts 1, 2, and 3.

Weir, Donald S.; Jumper, Stephen J.; Burley, Casey L.; Golub, Robert A.

1995-01-01

97

Sports Ball Aerodynamics  

Microsoft Academic Search

Aerodynamics plays a prominent role in defining the flight of a ball that is struck or thrown through the air in almost all\\u000a ball sports. The main interest is in the fact that the ball can often deviate from its initial straight path, resulting in\\u000a a curved, or sometimes an unpredictable, flight path. It is particularly fascinating that not all

Rabindra D. Mehta

98

aeroacoustics volume 9 number 1 & 2 2010 pages 123143 123 Progress in direct noise computation  

E-print Network

the direct computation of aerodynamic noise with applications to subsonic and supersonic jet noise, to cavityaeroacoustics volume 9 · number 1 & 2 · 2010 ­ pages 123­143 123 Progress in direct noise noise and to self-excited internal flows. 1. INTRODUCTION Direct Noise Computation (DNC) consists

Paris-Sud XI, Université de

99

Enhancing Sound Source Localization with Noise Separation Methods  

E-print Network

Enhancing Sound Source Localization with Noise Separation Methods L. Lamottea , S. Paillasseura , K aerodynamic turbulence of the nozzle. The second example aims to separate and localize combustion noise from to localize noise sources on the object surface. This diagnostic is limited to the identification of the most

Paris-Sud XI, Université de

100

Aerodynamic Shape Optimization Using the Adjoint Method  

E-print Network

Aerodynamic Shape Optimization Using the Adjoint Method Antony Jameson Department of Aeronautics techniques based on control theory for aerodynamic shape design in both inviscid and viscous compressible optimization of transonic wing-body combinations. 1 Introduction: Aerodynamic Design The definition

Jameson, Antony

101

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

102

Numerical Aerodynamic Simulation (NAS)  

NASA Technical Reports Server (NTRS)

The history of the Numerical Aerodynamic Simulation Program, which is designed to provide a leading-edge capability to computational aerodynamicists, is traced back to its origin in 1975. Factors motivating its development and examples of solutions to successively refined forms of the governing equations are presented. The NAS Processing System Network and each of its eight subsystems are described in terms of function and initial performance goals. A proposed usage allocation policy is discussed and some initial problems being readied for solution on the NAS system are identified.

Peterson, V. L.; Ballhaus, W. F., Jr.; Bailey, F. R.

1983-01-01

103

THE RADIATED NOISE FROM ISOTROPIC TURBULENCE WITH APPLICATIONS TO THE THEORY OF JET NOISE  

Microsoft Academic Search

Lighthill [1], in hisTheory of Aerodynamic Noise, considered the noise from a pseudo-finite yet unbounded domain of compressible unsteady flow. The first application of this theory was given by Proudman [2] for the case of isotropic turbulence at low Mach numbers and high Reynolds numbers. More recently, Lilley [3] and Sarkar and Hussaini [4], using Direct Numerical Simulation (DNS), have

G. M. Lilley

1996-01-01

104

Aerodynamic design using numerical optimization  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

105

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

106

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

107

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

108

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.

109

Aerodynamics of sports balls  

NASA Technical Reports Server (NTRS)

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.

1985-01-01

110

Plasma Aerodynamic Control Effectors for Improved Wind Turbine Performance  

SciTech Connect

Orbital Research Inc is developing an innovative Plasma Aerodynamic Control Effectors (PACE) technology for improved performance of wind turbines. The PACE system is aimed towards the design of "smart" rotor blades to enhance energy capture and reduce aerodynamic loading and noise using flow-control. The PACE system will provide ability to change aerodynamic loads and pitch distribution across the wind turbine blade without any moving surfaces. Additional benefits of the PACE system include reduced blade structure weight and complexity that should translate into a substantially reduced initial cost. During the Phase I program, the ORI-UND Team demonstrated (proof-of-concept) performance improvements on select rotor blade designs using PACE concepts. Control of both 2-D and 3-D flows were demonstrated. An analytical study was conducted to estimate control requirements for the PACE system to maintain control during wind gusts. Finally, independent laboratory experiments were conducted to identify promising dielectric materials for the plasma actuator, and to examine environmental effects (water and dust) on the plasma actuator operation. The proposed PACE system will be capable of capturing additional energy, and reducing aerodynamic loading and noise on wind turbines. Supplementary benefits from the PACE system include reduced blade structure weight and complexity that translates into reduced initial capital costs.

Mehul P. Patel; Srikanth Vasudevan; Robert C. Nelson; Thomas C. Corke

2008-08-01

111

Modeling the High Speed Research Cycle 2B Longitudinal Aerodynamic Database Using Multivariate Orthogonal Functions  

NASA Technical Reports Server (NTRS)

The data for longitudinal non-dimensional, aerodynamic coefficients in the High Speed Research Cycle 2B aerodynamic database were modeled using polynomial expressions identified with an orthogonal function modeling technique. The discrepancy between the tabular aerodynamic data and the polynomial models was tested and shown to be less than 15 percent for drag, lift, and pitching moment coefficients over the entire flight envelope. Most of this discrepancy was traced to smoothing local measurement noise and to the omission of mass case 5 data in the modeling process. A simulation check case showed that the polynomial models provided a compact and accurate representation of the nonlinear aerodynamic dependencies contained in the HSR Cycle 2B tabular aerodynamic database.

Morelli, E. A.; Proffitt, M. S.

1999-01-01

112

Unsteady aerodynamics of blade rows  

NASA Technical Reports Server (NTRS)

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

Verdon, Joseph M.

1989-01-01

113

NASA progress in aircraft noise prediction  

NASA Technical Reports Server (NTRS)

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 noise sources, forward speed effects, a layered atmospheric model with molecular absorption, ground impedance effects including excess ground attenuation, and a received noise contouring capability. The present state of ANOPP is described and its accuracy and applicability to the preliminary aircraft design process is assessed. Areas are indicated where further theoretical and experimental research on noise prediction are needed. Topics covered include the elements of the noise prediction problem which are incorporated in ANOPP, results of comparisons of ANOPP calculations with measured noise levels, and progress toward treating noise as a design constraint in aircraft system studies.

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

1981-01-01

114

The Airframe Noise Reduction Challenge  

NASA Technical Reports Server (NTRS)

The NASA goal of reducing external aircraft noise by 10 dB in the near-term presents the acoustics community with an enormous challenge. This report identifies technologies with the greatest potential to reduce airframe noise. Acoustic and aerodynamic effects will be discussed, along with the likelihood of industry accepting and implementing the different technologies. We investigate the lower bound, defined as noise generated by an aircraft modified with a virtual retrofit capable of eliminating all noise associated with the high lift system and landing gear. However, the airframe noise of an aircraft in this 'clean' configuration would only be about 8 dB quieter on approach than current civil transports. To achieve the NASA goal of 10 dB noise reduction will require that additional noise sources be addressed. Research shows that energy in the turbulent boundary layer of a wing is scattered as it crosses trailing edge. Noise generated by scattering is the dominant noise mechanism on an aircraft flying in the clean configuration. Eliminating scattering would require changes to much of the aircraft, and practical reduction devices have yet to receive serious attention. Evidence suggests that to meet NASA goals in civil aviation noise reduction, we need to employ emerging technologies and improve landing procedures; modified landing patterns and zoning restrictions could help alleviate aircraft noise in communities close to airports.

Lockhard, David P.; Lilley, Geoffrey M.

2004-01-01

115

Vortex flow aerodynamics  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

116

Nacelle aerodynamic performance  

NASA Technical Reports Server (NTRS)

The boundary layer transition location was measured on a nacelle shape using the sublimating chemical flow visualization technique. This technique involves coating the surface with a thin film of volatile chemical solid, which, during exposure to a free stream airflow, rapidly sublimates in the turbulent boundary layer as a result of high shear stress and high mass transfer near the surface. Transition is indicated because the chemical coating remains relatively unaffected in the laminar region due to lower shear and low mass transfer. The slow response time of the chemical in a laminar boundary allowed for two test conditions during the same flight. The aircraft was first flown at the desired airspeed and altitude with the noise source off. Once a pattern had developed, the noise source was turned on to the desired setting and a new chemical pattern was sought. In this fashion a direct comparison of the effect of the noise could be determined.

Obara, Clifford J.; Dodbele, S. S.

1987-01-01

117

Acoustics and aerodynamics of over-the-wing thrust reversers  

NASA Technical Reports Server (NTRS)

As part of the Quiet Clean Short-Haul Experimental Engine Program, model tests were conducted to determine the effects of thrust reverser geometric parameters on noise and reverse thrust. The acoustic tests used a 1/6 scale model thrust reverser while the aerodynamic performance tests used a 1/12 scale model reverser. Parameters which were varied in both tests include blocker spacing, blocker height, lip angle, and lip length. The impact of these parameters on peak sideline noise and reverse thrust performance is discussed.

Stimpert, D. L.; Ammer, R. C.

1976-01-01

118

Comparison of direct and indirect combustion noise mechanisms in a model combustor  

E-print Network

's method I. Introduction Over the last five decades, jet and external aerodynamic noises of aircraft have been achieved on fan and jet noise, the relative importance of other noise sources has increasedComparison of direct and indirect combustion noise mechanisms in a model combustor M. Leyko SNECMA

Paris-Sud XI, Université de

119

Parameter identification for nonlinear aerodynamic systems  

NASA Technical Reports Server (NTRS)

Parameter identification for nonlinear aerodynamic systems is examined. It is presumed that the underlying model can be arranged into an input/output (I/O) differential operator equation of a generic form. The algorithm estimation is especially efficient since the equation error can be integrated exactly given any I/O pair to obtain an algebraic function of the parameters. The algorithm for parameter identification was extended to the order determination problem for linear differential system. The degeneracy in a least squares estimate caused by feedback was addressed. A method of frequency analysis for determining the transfer function G(j omega) from transient I/O data was formulated using complex valued Fourier based modulating functions in contrast with the trigonometric modulating functions for the parameter estimation problem. A simulation result of applying the algorithm is given under noise-free conditions for a system with a low pass transfer function.

Pearson, Allan E.

1990-01-01

120

Aerodynamics at the Particle Level  

E-print Network

This paper is intended to clarify some of the rather well-known aerodynamic phenomena. It is also intended to pique the interest of the layman as well as the professional. All aerodynamic forces on a surface are caused by collisions of fluid particles with the surface. While the standard approach to fluid dynamics, which is founded on the fluid approximation, is effective in providing a means of calculating various behavior and properties, it begs the question of causality. The determination of the causes of many of the most important aerodynamic effects requires a microscopic examination of the fluid and of the surface with which it interacts. The Kutta-Joukowski theorem is investigated from first physical principles. It is noted that the circulation does not arise as a physical phenomenon. Various aerodynamic devices are discussed, e.g. rocket engine exhaust diffuser and the perfume atomizer.

Charles A. Crummer

2005-07-15

121

Computational aerodynamics and artificial intelligence  

NASA Technical Reports Server (NTRS)

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

Kutler, P.; Mehta, U. B.

1984-01-01

122

Investigation of aerodynamic braking devices for wind turbine applications  

SciTech Connect

This report documents the selection and preliminary design of a new aerodynamic braking system for use on the stall-regulated AWT-26/27 wind turbines. The goal was to identify and design a configuration that offered improvements over the existing tip brake used by Advanced Wind Turbines, Inc. (AWT). Although the design objectives and approach of this report are specific to aerodynamic braking of AWT-26/27 turbines, many of the issues addressed in this work are applicable to a wider class of turbines. The performance trends and design choices presented in this report should be of general use to wind turbine designers who are considering alternative aerodynamic braking methods. A literature search was combined with preliminary work on device sizing, loads and mechanical design. Candidate configurations were assessed on their potential for benefits in the areas of cost, weight, aerodynamic noise, reliability and performance under icing conditions. As a result, two configurations were identified for further study: the {open_quotes}spoiler-flap{close_quotes} and the {open_quotes}flip-tip.{close_quotes} Wind tunnel experiments were conducted at Wichita State University to evaluate the performance of the candidate aerodynamic brakes on an airfoil section representative of the AWT-26/27 blades. The wind tunnel data were used to predict the braking effectiveness and deployment characteristics of the candidate devices for a wide range of design parameters. The evaluation was iterative, with mechanical design and structural analysis being conducted in parallel with the braking performance studies. The preliminary estimate of the spoiler-flap system cost was $150 less than the production AWT-26/27 tip vanes. This represents a reduction of approximately 5 % in the cost of the aerodynamic braking system. In view of the preliminary nature of the design, it would be prudent to plan for contingencies in both cost and weight.

Griffin, D.A. [R. Lynette & Associates, Seattle, WA (United States)

1997-04-01

123

Noise Reduction Through Circulation Control  

NASA Technical Reports Server (NTRS)

Circulation control technology uses tangential blowing around a rounded trailing edge or a leading edge to change the force and moment characteristics of an aerodynamic body. This technology has been applied to circular cylinders, wings, helicopter rotors, and even to automobiles for improved aerodynamic performance. Only limited research has been conducted on the acoustics of this technology. Since wing flaps contribute to the environmental noise of an aircraft, an alternate blown high lift system without complex mechanical flaps could prove beneficial in reducing the noise of an approaching aircraft. Thus, in this study, a direct comparison of the acoustic characteristics of high lift systems employing a circulation control wing configuration and a conventional wing flapped configuration has been made. These results indicate that acoustically, a circulation control wing high lift system could be considerably more acceptable than a wing with conventional mechanical flaps.

Munro, Scott E.; Ahuja, K. K.; Englar, Robert J.

2003-01-01

124

Noise Reduction Through Circulation Control  

NASA Technical Reports Server (NTRS)

Circulation control technology uses tangential blowing around a rounded trailing edge or a leading edge to change the force and moment characteristics of an aerodynamic body. This technology has been applied to circular cylinders, wings, helicopter rotors, and even to automobiles for improved aerodynamic performance. Only limited research has been conducted on the acoustic of this technology. Since wing flaps contribute to the environmental noise of an aircraft, an alternate blown high lift system without complex mechanical flaps could prove beneficial in reducing the noise of an approaching aircraft. Thus, in this study, a direct comparison of the acoustic characteristics of high lift systems employing a circulation control wing configuration and a conventional wing flapped configuration has been made. These results indicate that acoustically, a circulation control wing high lift system could be considerably more acceptable than a wing with conventional mechanical flaps.

Munro, Scott E.; Ahuja, K. K.; Englar, Robert J.

2005-01-01

125

Noise Generation in Hot Jets  

NASA Technical Reports Server (NTRS)

A prediction method based on the generalized acoustic analogy is presented, and used to evaluate aerodynamic noise radiated from high speed hot jets. The set of Euler equations are split into their respective non-radiating and residual components. Under certain conditions, the residual equations are rearranged to form a wave equation. This equation consists of a third-order wave operator, plus a number of nonlinear terms that are identified with the equivalent sources of sound and their statistical characteristics are modeled. A specialized RANS solver provides the base flow as well as turbulence quantities and temperature fluctuations that determine the source strength. The main objective here is to evaluate the relative contribution from various source elements to the far-field spectra and to show the significance of temperature fluctuations as a source of aerodynamic noise in hot jets.

Khavaran, Abbas; Kenzakowski, Donald C.

2007-01-01

126

Explanation and discovery in aerodynamics  

E-print Network

The purpose of this paper is to discuss and clarify the explanations commonly cited for the aerodynamic lift generated by a wing, and to then analyse, as a case study of engineering discovery, the aerodynamic revolutions which have taken place within Formula 1 in the past 40 years. The paper begins with an introduction that provides a succinct summary of the mathematics of fluid mechanics.

McCabe, G

2005-01-01

127

Explanation and discovery in aerodynamics  

E-print Network

The purpose of this paper is to discuss and clarify the explanations commonly cited for the aerodynamic lift generated by a wing, and to then analyse, as a case study of engineering discovery, the aerodynamic revolutions which have taken place within Formula 1 in the past 40 years. The paper begins with an introduction that provides a succinct summary of the mathematics of fluid mechanics.

Gordon McCabe

2005-12-22

128

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

129

Aerodynamics of a Party Balloon  

NASA Astrophysics Data System (ADS)

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 can be made of drag and buoyant forces, and reasonable estimates can also be made of the Magnus force on a spinning balloon.

Cross, Rod

2007-09-01

130

Introduction. Computational aerodynamics.  

PubMed

The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier-Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used. PMID:17519203

Tucker, Paul G

2007-10-15

131

Rotorcraft noise  

NASA Technical Reports Server (NTRS)

The establishment of a realistic plan for NASA and the U.S. helicopter industry to develop a design-for-noise methodology, including plans for the identification and development of promising noise reduction technology was discussed. Topics included: noise reduction techniques, scaling laws, empirical noise prediction, psychoacoustics, and methods of developing and validing noise prediction methods.

Huston, R. J. (compiler)

1982-01-01

132

On the acoustic and aerodynamic performance of serrated airfoils.  

PubMed

This paper is concerned with the aerodynamic and aeroacoustic performance of airfoils with serrated trailing edges. Although a great deal of research has been directed toward the application of serrations for reducing the trailing-edge noise, the aerodynamic performance of such airfoils has received very little research attention. Sawtooth and slitted-sawtooth trailing edges with specific geometrical characteristics have been shown to be effective in reducing the trailing edge noise over a wide range of frequencies. It has, however, also been shown that they can alter the flow characteristics near the trailing edge, namely the boundary layer thickness and surface-pressure fluctuations, and the wake formation. To better understand the effects of serrations, we shall carry out various acoustic and wind tunnel tests for a NACA6512-10 airfoil with various sawtooth, slitted and slitted-sawtooth trailing edge profiles. Flow measurements are carried out using PIV, LDV and hot-wire anemometry and the steady and unsteady forces on the airfoil are obtained using a three-component force balance system. Results are presented for a wide range of Reynolds numbers and angles of attack. The results have shown that the use of sharp serrations can significantly change the aerodynamic performance and wake characteristics of the airfoil. PMID:25235897

Liu, Xiao; Azarpeyvand, Mahdi; Joseph, Phillip

2014-04-01

133

An Assessment of NASA Glenn's Aeroacoustic Experimental and Predictive Capabilities for Installed Cooling Fans. Part 1; Aerodynamic Performance  

NASA Technical Reports Server (NTRS)

Driven by the need for low production costs, electronics cooling fans have evolved differently than the bladed components of gas turbine engines which incorporate multiple technologies to enhance performance and durability while reducing noise emissions. Drawing upon NASA Glenn's experience in the measurement and prediction of gas turbine engine aeroacoustic performance, tests have been conducted to determine if these tools and techniques can be extended for application to the aerodynamics and acoustics of electronics cooling fans. An automated fan plenum installed in NASA Glenn's Acoustical Testing Laboratory was used to map the overall aerodynamic and acoustic performance of a spaceflight qualified 80 mm diameter axial cooling fan. In order to more accurately identify noise sources, diagnose performance limiting aerodynamic deficiencies, and validate noise prediction codes, additional aerodynamic measurements were recorded for two operating points: free delivery and a mild stall condition. Non-uniformities in the fan s inlet and exhaust regions captured by Particle Image Velocimetry measurements, and rotor blade wakes characterized by hot wire anemometry measurements provide some assessment of the fan aerodynamic performance. The data can be used to identify fan installation/design changes which could enlarge the stable operating region for the fan and improve its aerodynamic performance and reduce noise emissions.

VanZante, Dale E.; Koch, L. Danielle; Wernet, Mark P.; Podboy, Gary G.

2006-01-01

134

Configuration Aerodynamics: Past - Present - Future  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

135

Unsteady aerodynamic analyses for turbomachinery aeroelastic predictions  

NASA Technical Reports Server (NTRS)

Applications for unsteady aerodynamics analysis in this report are: (1) aeroelastic: blade flutter and forced vibration; (2) aeroacoustic: noise generation; (3) vibration and noise control; and (4) effects of unsteadiness on performance. This requires that the numerical simulations and analytical modeling be accurate and efficient and contain realistic operating conditions and arbitrary modes of unsteady excitation. The assumptions of this application contend that: (1) turbulence and transition can be modeled with the Reynolds averaged and using Navier-Stokes equations; (2) 'attached' flow with high Reynolds number will require thin-layer Navier-Stokes equations, or inviscid/viscid interaction analyses; (3) small-amplitude unsteady excitations will need nonlinear steady and linearized unsteady analyses; and (4) Re to infinity will concern inviscid flow. Several computer programs (LINFLO, CLT, UNSVIS, AND SFLOW-IVI) are utilized for these analyses. Results and computerized grid examples are shown. This report was given during NASA LeRC Workshop on Forced Response in Turbomachinery in August of 1993.

Verdon, Joseph M.; Barnett, M.; Ayer, T. C.

1994-01-01

136

Aeroelastic Analysis of Bridges: Effects of Turbulence and Aerodynamic Nonlinearities  

E-print Network

by utilizing an example of a long span suspension bridge with aerodynamic characteristics sensitiveAeroelastic Analysis of Bridges: Effects of Turbulence and Aerodynamic Nonlinearities Xinzhong Chen for capturing the emerging concerns in bridge aerodynamics introduced by aerodynamic nonlinearities

Kareem, Ahsan

137

JET Noise Prediction  

NASA Technical Reports Server (NTRS)

Aerodynamic noise prediction has been an important and challenging research area since James Lighthill first introduced his Acoustic Analogy Approach over fifty years ago. This talk attempts to provide a unified framework for the subsequent theoretical developments in this field. It assumes that there is no single approach that is optimal in all situations and uses the framework as a basis for discussing the strengths weaknesses of the various approaches to this topic. But the emphasis here will be on the important problem of predicting the noise from high speed air jets. Specific results will presented for round jets in the 0.5 to 1.4 Mach number range and compared with experimental data taken on the Glenn SHAR rig. It is demonstrated that non-parallel mean flow effects play an important role in predicting the noise at the supersonic Mach numbers. The results explain the failure of previous attempts based on the parallel flow Lilley model (which has served as the foundation for most jet noise analyses during past two decades).

Goldstein, M. E.; Leib, S. J.

2007-01-01

138

Aerodynamic and acoustic performance of high Mach number inlets  

NASA Technical Reports Server (NTRS)

Experimental results were obtained for two types of high Mach number inlets, one with a translating centerbody and one with a fixed geometry (collapsing cowl) without centerbody. The aerodynamic and acoustic performance of these inlets was examined. The effects of several parameters such as area ratio and length-diameter ratio were investigated. The translating centerbody inlet was found to be superior to the collapsing cowl inlet both acoustically and aerodynamically, particularly for area ratios greater than 1.5. Comparison of length-diameter ratio and area ratio effects on performance near choked flow showed the latter parameter to be more significant. Also, greater high frequency noise attenuation was achieved by increasing Mach number from low to high subsonic values.

Lumsdaine, E.; Clark, L. R.; Cherng, J. C.; Tag, I.

1977-01-01

139

Aerodynamics Research Revolutionizes Truck Design  

NASA Technical Reports Server (NTRS)

During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.

2008-01-01

140

Aerodynamics in air pollution modeling  

SciTech Connect

The aerodynamic effects of structures, urban complexes, and significant topographic features on the mechanism of pollutant transport and dispersion processes in the atmosphere are described. Various treatments of these aerodynamic effects in air pollution modeling are discussed. In view of the complex nature of flow disturbance and pollutant dispersion over structures and terrain obstacles and the general uniqueness of each specific situation, both the reliability of the data base and the suitability of a particular air pollution model must be evaluated. Validation and calibration of models against field measurements are strongly recommended. (7 diagrams, 2 graphs, 47 references)

Wang, H.; Liu, H.

1980-03-01

141

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

142

Measurement and estimation of the aerodynamic resistance  

Microsoft Academic Search

Using two methods of eddy correlation system and evaporation pan to measure respectively the aerodynamic resistance over bare soil surface and maize field, this paper analyses the diurnal variation of the aerodynamic resistance and its relationship with wind speed. Based on direct measurements by eddy correlation system, an evaluation of the aerodynamic resistance models is made. These models include Thom

S. Liu; D. Mao; L. Lu

2006-01-01

143

Langley Symposium on Aerodynamics, volume 1  

NASA Technical Reports Server (NTRS)

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.

Stack, Sharon H. (compiler)

1986-01-01

144

SUCCESSES AND CHALLENGES IN COMPUTATIONAL AERODYNAMICS  

E-print Network

SUCCESSES AND CHALLENGES IN COMPUTATIONAL AERODYNAMICS Antony Jameson Department of Mechanical into two broad categories. First there is the objective of providing reliable aerodynamic predictions of this paper is devoted to the use of computational methods for aerodynamic prediction. This is a comparatively

Jameson, Antony

145

AIAA 99--1467 LOW ORDER AERODYNAMIC  

E-print Network

AIAA 99--1467 LOW ORDER AERODYNAMIC MODELS FOR AEROELASTIC CONTROL OF TURBOMACHINES K.E. Willcox, J of Aeronautics and Astronautics 1801 Alexander Bell Drive, Suite 500, Reston, VA 22091 #12; LOW ORDER AERODYNAMIC order aerodynamic model is developed for aeroelastic analysis of turbomachines. The proper or­ thogonal

Peraire, Jaime

146

Conformal Mapping in Wing Aerodynamics Thomas Johnson  

E-print Network

Conformal Mapping in Wing Aerodynamics Thomas Johnson June 4, 2013 Contents 1 Introduction 1 2 the first complete treatment of conformal mapping in aerodynamics. Near the beginning of the twentieth and aerodynamics. The purpose of this exposition is to give the reader an elementary intro- duction to the use

Morrow, James A.

147

Portfolio Assessment in Aerodynamics Nikos J. Mourtos  

E-print Network

Portfolio Assessment in Aerodynamics Nikos J. Mourtos Department of Mechanical & Aerospace in an aerodynamics course through the use of portfolios is presented. The approach is portable to any engineering student motivation and learning. I. Introduction The aerodynamics course (AE 162) at SJSU is a second

Mourtos, Nikos

148

Aerodynamics and Aeroelastics, WP 2 Flemming Rasmussen  

E-print Network

Aerodynamics and Aeroelastics, WP 2 Flemming Rasmussen Aeroelastic Design Wind Energy Department Risø DTU #12;WP2 Aero-dynamics and Aero-elastics OBJECTIVES 1. Development of nonlinear structural dynamic models (modeling on the micromechanical scale is input from WP3). 2. Advanced aerodynamic models

149

Computational Aerodynamics for Aircraft Design Antony Jameson  

E-print Network

Computational Aerodynamics for Aircraft Design Antony Jameson Abstract This article outlines some to optimize the aerodynamic performance. While computational methods for simulating fluid flow have by now to design more efficient aircraft. One route toward this goal is more precise aerodynamic design

Jameson, Antony

150

CFD-based Optimization for Automotive Aerodynamics  

E-print Network

Chapter 1 CFD-based Optimization for Automotive Aerodynamics Laurent Dumas Abstract The car drag- ments. An overview of the main characteristics of automotive aerodynamics and a detailed presentation.dumas@upmc.fr) 1 #12;2 Laurent Dumas 1.1 Introducing Automotive Aerodynamics 1.1.1 A Major Concern for Car

Dumas, Laurent

151

AERODYNAMICS RESEARCH CENTER MECHANICAL AND AEROSPACE ENGINEERING  

E-print Network

08/03/2007 16:39 1 AERODYNAMICS RESEARCH CENTER MECHANICAL AND AEROSPACE ENGINEERING DEPARTMENT Arlington #12;08/03/2007 16:39 2 AERODYNAMICS RESEARCH CENTER MECHANICAL AND AEROSPACE ENGINEERING:39 3 AERODYNAMICS RESEARCH CENTER MECHANICAL AND AEROSPACE ENGINEERING DEPARTMENT PDEs employ a

Texas at Arlington, University of

152

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

153

Computational Aerodynamics and Aeroacoustics for Wind Turbines  

E-print Network

objective of the research was to develop new computational tools or approaching techniques for analysingComputational Aerodynamics and Aeroacoustics for Wind Turbines #12;#12;Computational Aerodynamics Shen, Wen Zhong Computational Aerodynamics and Aeroacoustics for Wind Turbines Doctor Thesis Technical

154

A full scale bicycle aerodynamics testing methodology  

Microsoft Academic Search

Aerodynamically efficient sport equipment\\/accessories and athlete's body postures are considered to be the fundamental aspect to achieving better outcomes. Like any other speed sports, the aerodynamic optimization is essential in cycling. A standard full scale testing methodology for the aerodynamic optimization of a cyclist along with all accessories (bicycle, helmet, cycling suit, shoes, goggle, etc.) is not well developed and

Harun Chowdhury; Firoz Alam; David Mainwaring

2011-01-01

155

Combustion noise  

NASA Technical Reports Server (NTRS)

A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

Strahle, W. C.

1977-01-01

156

Noise suppression by flexible fan silencers  

SciTech Connect

This paper presents the results on noise testing of a fan only, as well as the results of a steel silencer and of flexible silencers that were connected directly to a fan. On-site facilities and free-field method set by the British Standards Institution were used to measure and then compare the fan only and different practical silencer configuration setups. In order to determine the fan-silencer combination that would give the maximum noise attenuation, total noise intensity, noise contributed to by the fan motor only, as well as aerodynamical noise created through air interacting with the fan parts were considered to obtain decibel readings for the octave bands. Subsequently, the optimal configuration found was the setup with flexible silencers on the fan inlet and the fan outlet. If only one silencer is used, it should be installed on the fan inlet. The aerodynamic noise affects the low frequencies. The flow noise is then overtaken at 1 kHz by the mechanical noise.

Partyka, J. [Laurentian Univ., Sudbury, Ontario (Canada); Kelly, T.R.J.

1995-12-31

157

Unsteady aerodynamics of blade rows  

NASA Technical Reports Server (NTRS)

The requirements placed on an unsteady aerodynamic theory intended for turbomachinery aeroelastic applications are discussed along with a brief description of the various theoretical models that are available to address these requirements. The main emphasis is placed on the description of a linearized inviscid theory which fully accounts for the effects of a nonuniform mean or steady flow on unsteady aerodynamic response. Although this theory has been developed primarily for blade flutter prediction, more general equations are presented which account for unsteady excitations due to incident external aerodynamic disturbances as well as those due to blade motions. The resulting equations consist of a system of three field equations along with conditions imposed at blade, wake and shock surfaces and in the far field. These equations can be solved to determine the fluctuations in all fluid dynamic properties throughout the required solution domain. Example solutions are presented to demonstrate several effects associated with nonuniform steady flows on the linearized unsteady aerodynamic response to prescribed blade motions.

Verdon, J. M.

1987-01-01

158

Semianalytic modeling of aerodynamic shapes  

NASA Technical Reports Server (NTRS)

Equations for the semianalytic representation of a class of surfaces that vary smoothly in cross-sectional shape are presented. Some methods of fitting together and superimposing such surfaces are described. A brief discussion is also included of the application of the theory in various contexts such as computerized lofting of aerodynamic surfaces and grid generation.

Barger, R. L.; Adams, M. S.

1985-01-01

159

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

160

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

161

Aerodynamics of the hovering hummingbird  

Microsoft Academic Search

Despite profound musculoskeletal differences, hummingbirds (Trochilidae) are widely thought to employ aerodynamic mechanisms similar to those used by insects. The kinematic symmetry of the hummingbird upstroke and downstroke has led to the assumption that these halves of the wingbeat cycle contribute equally to weight support during hovering, as exhibited by insects of similar size. This assumption has been applied, either

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

2005-01-01

162

The Aerodynamics of Hummingbird Flight  

Microsoft Academic Search

(Abstract) Hummingbirds fly with their wings almost fully extended during their entire wingbeat. This pattern, associated with having proportionally short humeral bones, long distal wing elements, and assumed to be an adaptation for extended hovering flight, has lead to predictions that the aerodynamic mechanisms exploited by hummingbirds during hovering should be similar to those observed in insects. To test these

Douglas R. Warrick; Bret W. Tobalske; Donald R. Powers; Michael H. Dickinson

163

The aerodynamics of supersonic parachutes  

Microsoft Academic Search

A discussion of the aerodynamics and performance of parachutes flying at supersonic speeds is the focus of this paper. Typical performance requirements for supersonic parachute systems are presented, followed by a review of the literature on supersonic parachute configurations and their drag characteristics. Data from a recent supersonic wind tunnel test series is summarized. The value and limitations of supersonic

1987-01-01

164

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

165

Aerodynamic Measurement Technology  

NASA Technical Reports Server (NTRS)

Ohio State University developed a new spectrally filtered light-scattering apparatus based on a diode laser injected-locked titanium: sapphire laser and rubidium vapor filter at 780.2 nm. When the device was combined with a stimulated Brillouin scattering phase conjugate mirror, the realizable peak attenuation of elastic scattering interferences exceeded 105. The potential of the system was demonstrated by performing Thomson scattering measurements. Under USAF-NASA funding, West Virginia University developed a Doppler global velocimetry system using inexpensive 8-bit charged coupled device cameras and digitizers and a CW argon ion laser. It has demonstrated a precision of +/- 2.5 m/sec in a swirling jet flow. Low-noise silicon-micromachined microphones developed and incorporated in a novel two-tier, hybrid packaging scheme at the University of Florida used printed circuit board technology to realize a MEMS-based directional acoustic array. The array demonstrated excellent performance relative to conventional sensor technologies and provides scaling technologies that can reduce cost and increase speed and mobility.

Burner, Alpheus W.

2002-01-01

166

Assessing Bicyclist and Pedestrian Exposure to Ultrafine Particles: Passive1 Shielding with Noise Barriers2  

E-print Network

to traffic-related air pollutants, including ultrafine23 particles (UFP, particulate matter with aerodynamicAssessing Bicyclist and Pedestrian Exposure to Ultrafine Particles: Passive1 Shielding with Noise exposure to2 ultrafine particles (UFP), particulate matter with aerodynamic diameter less than 0.1 µm

Bertini, Robert L.

167

Empirical Prediction of Aircraft Landing Gear Noise  

NASA Technical Reports Server (NTRS)

This report documents a semi-empirical/semi-analytical method for landing gear noise prediction. The method is based on scaling laws of the theory of aerodynamic noise generation and correlation of these scaling laws with current available test data. The former gives the method a sound theoretical foundation and the latter quantitatively determines the relations between the parameters of the landing gear assembly and the far field noise, enabling practical predictions of aircraft landing gear noise, both for parametric trends and for absolute noise levels. The prediction model is validated by wind tunnel test data for an isolated Boeing 737 landing gear and by flight data for the Boeing 777 airplane. In both cases, the predictions agree well with data, both in parametric trends and in absolute noise levels.

Golub, Robert A. (Technical Monitor); Guo, Yue-Ping

2005-01-01

168

Diagnostic calculations of airframe-radiated noise  

NASA Technical Reports Server (NTRS)

Methods of calculating airframe noise due to the following components are presented: wings and stabilizers, flaps, landing gear 'self-noise', landing gear bay (wheel well) oscillations, separated flow interaction with edges of cavities, and doors associated with gear deployment. The predominant source mechanisms were dipole-like in nature, being related to the local fluctuating aerodynamic forces on struts, airfoil edges, cavity edges, etc. Available data are converted into semiempirical prediction methods to enable a tentative rank ordering of noise sources. A sample application of these prediction procedures is carried out for a typical CTOL passenger jet using actual aircraft parameters, where available.

Hayden, R. E.; Kadman, Y.; Bliss, D. B.; Africk, S. A.

1975-01-01

169

Tandem Cylinder Noise Predictions  

NASA Technical Reports Server (NTRS)

In an effort to better understand landing-gear noise sources, we have been examining a simplified configuration that still maintains some of the salient features of landing-gear flow fields. In particular, tandem cylinders have been studied because they model a variety of component level interactions. The present effort is directed at the case of two identical cylinders spatially separated in the streamwise direction by 3.7 diameters. Experimental measurements from the Basic Aerodynamic Research Tunnel (BART) and Quiet Flow Facility (QFF) at NASA Langley Research Center (LaRC) have provided steady surface pressures, detailed off-surface measurements of the flow field using Particle Image Velocimetry (PIV), hot-wire measurements in the wake of the rear cylinder, unsteady surface pressure data, and the radiated noise. The experiments were conducted at a Reynolds number of 166 105 based on the cylinder diameter. A trip was used on the upstream cylinder to insure a fully turbulent shedding process and simulate the effects of a high Reynolds number flow. The parallel computational effort uses the three-dimensional Navier-Stokes solver CFL3D with a hybrid, zonal turbulence model that turns off the turbulence production term everywhere except in a narrow ring surrounding solid surfaces. The current calculations further explore the influence of the grid resolution and spanwise extent on the flow and associated radiated noise. Extensive comparisons with the experimental data are used to assess the ability of the computations to simulate the details of the flow. The results show that the pressure fluctuations on the upstream cylinder, caused by vortex shedding, are smaller than those generated on the downstream cylinder by wake interaction. Consequently, the downstream cylinder dominates the noise radiation, producing an overall directivity pattern that is similar to that of an isolated cylinder. Only calculations based on the full length of the model span were able to capture the complete decay in the spanwise correlation, thereby producing reasonable noise radiation levels.

Lockhard, David P.; Khorrami, Mehdi R.; CHoudhari, Meelan M.; Hutcheson, Florence V.; Brooks, Thomas F.; Stead, Daniel J.

2007-01-01

170

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

171

Airfoil self noise - Effect of scale  

NASA Astrophysics Data System (ADS)

Key data from a comprehensive airfoil broadband self-noise study are reported. Attention here is restricted to two-dimensional sharp trailing-edge models. The models include seven NACA 0012 airfoil sections and five 'flat plate' sections with chordlengths ranging from 2.54 to 60.96 cm. Testing parameters include flow velocity, angle of attack to the flow, and boundary layer turbulence through natural transition and through tripping. Detailed aerodynamic measurements, of pertinence to the scaling problem of airfoil self-noise, were conducted in the near-wake of the trailing edges. Presented are mean and rms turbulent velocity profiles as well as boundary layer thicknesses and integral thickness parameters for a large range of conditions. The noise spectra of the self-noise sources were determined by the use of a cross-spectral technique. The spectra were normalized using the measured aerodynamic parameters in order to evaluate the most common scaling law now in use. An examination of the Reynolds number dependence of the overall self-noise levels has revealed a new and useful scaling result. This result appears to quantify the transition between turbulent-boundary-layer trailing edge noise and laminar-boundary-layer vortex shedding noise.

Brooks, T. F.; Marcolini, M. A.

1983-04-01

172

Airfoil self noise - Effect of scale  

NASA Technical Reports Server (NTRS)

Key data from a comprehensive airfoil broadband self-noise study are reported. Attention here is restricted to two-dimensional sharp trailing-edge models. The models include seven NACA 0012 airfoil sections and five 'flat plate' sections with chordlengths ranging from 2.54 to 60.96 cm. Testing parameters include flow velocity, angle of attack to the flow, and boundary layer turbulence through natural transition and through tripping. Detailed aerodynamic measurements, of pertinence to the scaling problem of airfoil self-noise, were conducted in the near-wake of the trailing edges. Presented are mean and rms turbulent velocity profiles as well as boundary layer thicknesses and integral thickness parameters for a large range of conditions. The noise spectra of the self-noise sources were determined by the use of a cross-spectral technique. The spectra were normalized using the measured aerodynamic parameters in order to evaluate the most common scaling law now in use. An examination of the Reynolds number dependence of the overall self-noise levels has revealed a new and useful scaling result. This result appears to quantify the transition between turbulent-boundary-layer trailing edge noise and laminar-boundary-layer vortex shedding noise.

Brooks, T. F.; Marcolini, M. A.

1983-01-01

173

Integrated aerodynamic/dynamic optimization of helicopter rotor blades  

NASA Technical Reports Server (NTRS)

An integrated aerodynamic/dynamic optimization procedure is used to minimize blade weight and 4 per rev vertical hub shear for a rotor blade in forward flight. The coupling of aerodynamics and dynamics is accomplished through the inclusion of airloads which vary with the design variables during the optimization process. Both single and multiple objective functions are used in the optimization formulation. The Global Criteria Approach is used to formulate the multiple objective optimization and results are compared with those obtained by using single objective function formulations. Constraints are imposed on natural frequencies, autorotational inertia, and centrifugal stress. The program CAMRAD is used for the blade aerodynamic and dynamic analyses, and the program CONMIN is used for the optimization. Since the spanwise and the azimuthal variations of loading are responsible for most rotor vibration and noise, the vertical airload distributions on the blade, before and after optimization, are compared. The total power required by the rotor to produce the same amount of thrust for a given area is also calculated before and after optimization. Results indicate that integrated optimization can significantly reduce the blade weight, the hub shear and the amplitude of the vertical airload distributions on the blade and the total power required by the rotor.

Chattopadhyay, Aditi; Walsh, Joanne L.; Riley, Michael F.

1989-01-01

174

Control of helicopter rotorblade aerodynamics  

NASA Technical Reports Server (NTRS)

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

Fabunmi, James A.

1991-01-01

175

Computer Simulation of Aircraft Aerodynamics  

NASA Technical Reports Server (NTRS)

The role of Ames Research Center in conducting basic aerodynamics research through computer simulations is described. The computer facilities, including supercomputers and peripheral equipment that represent the state of the art, are described. The methodology of computational fluid dynamics is explained briefly. Fundamental studies of turbulence and transition are being pursued to understand these phenomena and to develop models that can be used in the solution of the Reynolds-averaged Navier-Stokes equations. Four applications of computer simulations for aerodynamics problems are described: subsonic flow around a fuselage at high angle of attack, subsonic flow through a turbine stator-rotor stage, transonic flow around a flexible swept wing, and transonic flow around a wing-body configuration that includes an inlet and a tail.

Inouye, Mamoru

1989-01-01

176

Viking entry aerodynamics and heating  

NASA Technical Reports Server (NTRS)

The characteristics of the Mars entry including the mission sequence of events and associated spacecraft weights are described along with the Viking spacecraft. Test data are presented for the aerodynamic characteristics of the entry vehicle showing trimmed alpha, drag coefficient, and trimmed lift to drag ratio versus Mach number; the damping characteristics of the entry configuration; the angle of attack time history of Viking entries; stagnation heating and pressure time histories; and the aeroshell heating distribution as obtained in tests run in a shock tunnel for various gases. Flight tests which demonstrate the aerodynamic separation of the full-scale aeroshell and the flying qualities of the entry configuration in an uncontrolled mode are documented. Design values selected for the heat protection system based on the test data and analysis performed are presented.

Polutchko, R. J.

1974-01-01

177

Preliminary Aerodynamic Investigation of Fan Rotor Blade Morphing  

NASA Technical Reports Server (NTRS)

Various new technologies currently under development may enable controlled blade shape variability, or so-called blade morphing, to be practically employed in aircraft engine fans and compressors in the foreseeable future. The current study is a relatively brief, preliminary computational fluid dynamics investigation aimed at partially demonstrating and quantifying the aerodynamic potential of fan rotor blade morphing. The investigation is intended to provide information useful for near-term planning, as well as aerodynamic solution data sets that can be subsequently analyzed using advanced acoustic diagnostic tools, for the purpose of making fan noise comparisons. Two existing fan system models serve as baselines for the investigation: the Advanced Ducted Propulsor fan with a design tip speed of 806 ft/sec and a pressure ratio of 1.294, and the Source Diagnostic Test fan with a design tip speed of 1215 ft/sec and a pressure ratio of 1.470. Both are 22-in. sub-scale, low-noise research fan/nacelle models that have undergone extensive experimental testing in the 9- by 15-foot Low Speed Wind Tunnel at the NASA Glenn Research Center. The study, restricted to fan rotor blade morphing only, involves a fairly simple blade morphing technique. Specifically, spanwise-linear variations in rotor blade-section setting angle are applied to alter the blade shape; that is, the blade is linearly retwisted from hub to tip. Aerodynamic performance comparisons are made between morphed-blade and corresponding baseline configurations on the basis of equal fan system thrust, where rotor rotational speed for the morphed-blade fan is varied to change the thrust level for that configuration. The results of the investigation confirm that rotor blade morphing could be a useful technology, with the potential to enable significant improvements in fan aerodynamic performance. Even though the study is very limited in scope and confined to simple geometric perturbations of two existing fan systems, the aerodynamic effectiveness of blade morphing is demonstrated by the configurations analyzed. In particular, for the Advanced Ducted Propulsor fan it is demonstrated that the performance levels of the original variable-pitch baseline design can be achieved using blade morphing instead of variable pitch, and for the Source Diagnostic Test fan the performance at important off-design operating points is substantially increased with blade morphing.

Tweedt, Daniel L.

2012-01-01

178

Aerodynamic resistance of coppiced poplar  

Microsoft Academic Search

The aerodynamic resistance to the transfer of heat and water vapour, of a canopy of coppiced poplar (Populustrichocarpa×deltoides) was estimated as the sum of three components; the bulk leaf boundary layer, within-canopy, and roughness-sublayer resistances. These components were calculated from measurements of wind speed and leaf area distribution. Account was taken of enhanced transfer of heat and water vapour over

Robin L Hall

2002-01-01

179

Aerodynamic Design Using Neural Networks  

NASA Technical Reports Server (NTRS)

The design of aerodynamic components of aircraft, such as wings or engines, involves a process of obtaining the most optimal component shape that can deliver the desired level of component performance, subject to various constraints, e.g., total weight or cost, that the component must satisfy. Aerodynamic design can thus be formulated as an optimization problem that involves the minimization of an objective function subject to constraints. A new aerodynamic design optimization procedure based on neural networks and response surface methodology (RSM) incorporates the advantages of both traditional RSM and neural networks. The procedure uses a strategy, denoted parameter-based partitioning of the design space, to construct a sequence of response surfaces based on both neural networks and polynomial fits to traverse the design space in search of the optimal solution. Some desirable characteristics of the new design optimization procedure include the ability to handle a variety of design objectives, easily impose constraints, and incorporate design guidelines and rules of thumb. It provides an infrastructure for variable fidelity analysis and reduces the cost of computation by using less-expensive, lower fidelity simulations in the early stages of the design evolution. The initial or starting design can be far from optimal. The procedure is easy and economical to use in large-dimensional design space and can be used to perform design tradeoff studies rapidly. Designs involving multiple disciplines can also be optimized. Some practical applications of the design procedure that have demonstrated some of its capabilities include the inverse design of an optimal turbine airfoil starting from a generic shape and the redesign of transonic turbines to improve their unsteady aerodynamic characteristics.

Rai, Man Mohan; Madavan, Nateri K.

2003-01-01

180

A comprehensive analytical model of rotorcraft aerodynamics and dynamics. Part 1: Analysis development  

NASA Technical Reports Server (NTRS)

Structural, inertia, and aerodynamic models were combined to form a comprehensive model of rotor aerodynamics and dynamics that is applicable to a wide range of problems and a wide class of vehicles. A digital computer program is used to calculate rotor performance, loads, and noise; helicopter vibration and gust response; flight dynamics and handling qualities; and system aeroelastic stability. The analysis is intended for use in the design, testing, and evaluation of rotors and rotorcraft, and to be a basis for further development of rotary wing theories.

Johnson, W.

1980-01-01

181

A comprehensive analytical model of rotorcraft aerodynamics and dynamics. Part 3: Program manual  

NASA Technical Reports Server (NTRS)

The computer program for a comprehensive analytical model of rotorcraft aerodynamics and dynamics is described. This analysis is designed to calculate rotor performance, loads, and noise; the helicopter vibration and gust response; the flight dynamics and handling qualities; and the system aeroelastic stability. The analysis is a combination of structural, inertial, and aerodynamic models that is applicable to a wide range of problems and a wide class of vehicles. The analysis is intended for use in the design, testing, and evaluation of rotors and rotorcraft and to be a basis for further development of rotary wing theories.

Johnson, W.

1980-01-01

182

Applied aerodynamics: Challenges and expectations  

NASA Technical Reports Server (NTRS)

Aerospace is the leading positive contributor to this country's balance of trade, derived largely from the sale of U.S. commercial aircraft around the world. This powerfully favorable economic situation is being threatened in two ways: (1) the U.S. portion of the commercial transport market is decreasing, even though the worldwide market is projected to increase substantially; and (2) expenditures are decreasing for military aircraft, which often serve as proving grounds for advanced aircraft technology. To retain a major share of the world market for commercial aircraft and continue to provide military aircraft with unsurpassed performance, the U.S. aerospace industry faces many technological challenges. The field of applied aerodynamics is necessarily a major contributor to efforts aimed at meeting these technological challenges. A number of emerging research results that will provide new opportunities for applied aerodynamicists are discussed. Some of these have great potential for maintaining the high value of contributions from applied aerodynamics in the relatively near future. Over time, however, the value of these contributions will diminish greatly unless substantial investments continue to be made in basic and applied research efforts. The focus: to increase understanding of fluid dynamic phenomena, identify new aerodynamic concepts, and provide validated advanced technology for future aircraft.

Peterson, Victor L.; Smith, Charles A.

1993-01-01

183

Rotor noise  

NASA Technical Reports Server (NTRS)

The physical characteristics and sources of rotorcraft noise as they exist today are presented. Emphasis is on helicopter-like vehicles, that is, on rotorcraft in nonaxial flight. The mechanisms of rotor noise are reviewed in a simple physical manner for the most dominant sources of rotorcraft noise. With simple models, the characteristic time- and frequency-domain features of these noise sources are presented for idealized cases. Full-scale data on several rotorcraft are then reviewed to allow for the easy identification of the type and extent of the radiating noise. Methods and limitations of using scaled models to test for several noise sources are subsequently presented. Theoretical prediction methods are then discussed and compared with experimental data taken under very controlled conditions. Finally, some promising noise reduction technology is reviewed.

Schmitz, F. H.

1991-01-01

184

Advances in tilt rotor noise prediction  

NASA Technical Reports Server (NTRS)

The two most serious tilt rotor external noise problems, hover noise and blade-vortex interaction noise, are studied. The results of flow visualization and inflow velocity measurements document a complex, recirculating highly unsteady and turbulent flow due to the rotor-wing-body interactions characteristic of tilt rotors. The wing under the rotor is found to obstruct the inflow, causing a deficit in the inflow velocities over the inboard region of the rotor. Discrete frequency harmonic thickness and loading noise mechanisms in hover are examined by first modeling tilt rotor hover aerodynamics and then applying various noise prediction methods using the WOPWOP code. The analysis indicates that the partial ground plane created by the wing below the rotor results in a primary sound source for hover.

George, A. R.; Coffen, C. D.; Ringler, T. D.

1992-01-01

185

[Transmeatal aerodynamical otoendoscopy for otitis media].  

PubMed

This study was designed to compare the efficacy of various methods of transmeatal aerodynamical otoendoscopy based on the examination of 60 patients presenting with acute suppurative otitis media (CSOM), chronic suppurative otitis media (CSOM), exudative and adhesive otitis media. Transmeatal aerodynamical otoendoscopy was performed with the use of otobarohydroendoscope. The results of the study demonstrate the advantages of the transmeatal aerodynamical otoendoscopic technique for the examination of the patients presenting with different clinical forms of otitis media. PMID:23250522

Ageenko, I V

2012-01-01

186

Computational aerodynamics applications to transport aircraft design  

NASA Technical Reports Server (NTRS)

Examples are cited in assessing the effect that computational aerodynamics has had on the design of transport aircraft. The application of computational potential flow methods to wing design and to high-lift system design is discussed. The benefits offered by computational aerodynamics in reducing design cost, time, and risk are shown to be substantial.These aerodynamic methods have proved to be particularly effective in exposing inferior or poor aerodynamic designs. Particular attention is given to wing design, where the results have been dramatic.

Henne, P. A.

1983-01-01

187

Airframe noise  

NASA Technical Reports Server (NTRS)

Current understanding of airframe noise was reviewed as represented by experiment at model and full scale, by theoretical modeling, and by empirical correlation models. The principal component sources are associated with the trailing edges of wing and tail, deflected trailing edge flaps, flap side edges, leading edge flaps or slats, undercarriage gear elements, gear wheel wells, fuselage and wing boundary layers, and panel vibration, together with many minor protrusions like radio antennas and air conditioning intakes which may contribute significantly to perceived noise. There are also possibilities for interactions between the various mechanisms. With current engine technology, the principal airframe noise mechanisms dominate only at low frequencies, typically less than 1 kHz and often much lower, but further reduction of turbomachinery noise in particular may make airframe noise the principal element of approach noise at frequencies in the sensitive range.

Crighton, David G.

1991-01-01

188

Noise Protection  

NASA Technical Reports Server (NTRS)

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

189

THE AERODYNAMICS OF THE BRITISH LATE TRIASSIC KUEHNEOSAURIDAE  

E-print Network

THE AERODYNAMICS OF THE BRITISH LATE TRIASSIC KUEHNEOSAURIDAE by KOEN STEIN* , COLIN PALMER been limited. Here, we provide a thorough aerodynamic analysis of both genera of British kuehneosaur words: Kuehneosauridae, Diapsida, Late Triassic, glid- ing, aerodynamics. The Kuehneosauridae

Benton, Michael

190

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

191

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

192

Anechoic wind tunnel study of turbulence effects on wind turbine broadband noise  

NASA Technical Reports Server (NTRS)

This paper describes recent results obtained at MIT on the experimental and theoretical modelling of aerodynamic broadband noise generated by a downwind rotor horizontal axis wind turbine. The aerodynamic broadband noise generated by the wind turbine rotor is attributed to the interaction of ingested turbulence with the rotor blades. The turbulence was generated in the MIT anechoic wind tunnel facility with the aid of biplanar grids of various sizes. The spectra and the intensity of the aerodynamic broadband noise have been studied as a function of parameters which characterize the turbulence and of wind turbine performance parameters. Specifically, the longitudinal integral scale of turbulence, the size scale of turbulence, the number of turbine blades, and free stream velocity were varied. Simultaneous measurements of acoustic and turbulence signals were made. The sound pressure level was found to vary directly with the integral scale of the ingested turbulence but not with its intensity level. A theoretical model based on unsteady aerodynamics is proposed.

Loyd, B.; Harris, W. L.

1995-01-01

193

Aerodynamic performance of centrifugal compressors  

SciTech Connect

Saving money with an efficient pipeline system design depends on accurately predicting compressor performance and ensuring that it meets the manufacturer's guaranteed levels. When shop testing with the actual gas is impractical, an aerodynamic test can ascertain compressor efficiency, but the accuracy and consistency of data acquisition in such tests is critical. Low test-pressure levels necessitate accounting for the effects of Reynolds number and heat transfer. Moreover, the compressor user and manufacturer must agree on the magnitude of the corrections to be applied to the test data.

Sayyed, S.

1981-12-01

194

Environmental Noise  

NASA Astrophysics Data System (ADS)

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

Rumberg, Martin

195

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

196

Noise Meter  

MedlinePLUS

... only 2 minutes can become dangerous to the human ear! Content on this page requires a newer version of Adobe Flash Player. Download Noise Meter (.exe file) Download and play the Noise Meter file on any computer, even if Flash is not installed. Print page ...

197

Linearized unsteady aerodynamics for turbomachinery aeroelastic applications  

Microsoft Academic Search

The unsteady aerodynamic analyses developed for turbomachinery aeroelastic predictions must be appliable to the moderate through high frequency unsteady flows that are excited by structural motions and aerodynamic interactions between adjacent blade rows and occur over a wide range of operating conditions. In addition, because of the large number of controlling parameters involved, there is a stringent requirement on computational

Joseph M. Verdon

1992-01-01

198

Distributed Aerodynamic Sensing and Processing Toolbox  

NASA Technical Reports Server (NTRS)

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

Brenner, Martin; Jutte, Christine; Mangalam, Arun

2011-01-01

199

Review of aerodynamic design in the Netherlands  

NASA Technical Reports Server (NTRS)

Aerodynamic design activities in the Netherlands, which take place mainly at Fokker, the National Aerospace Laboratory (NLR), and Delft University of Technology (TUD), are discussed. The survey concentrates on the development of the Fokker 100 wing, glider design at TUD, and research at NLR in the field of aerodynamic design. Results are shown to illustrate these activities.

Labrujere, Th. E.

1991-01-01

200

Numerical Analysis of Flapping Wing Aerodynamics  

Microsoft Academic Search

Flapping-wing aerodynamics recently has generated a great deal of interest and increasing research effort because of the potential application in micro-air vehicles. The objective of this study is to critically review the recent progress of CFD analysis of flapping- wing aerodynamics. Critical parameters like flapping modes, frequency and amplitude for optimal thrust generation and propulsive efficiency are identified. Current gaps

M. A. Ashraf; J. C. S. Lai; J. Young

201

Aerodynamic considerations of blended wing body aircraft  

Microsoft Academic Search

In this paper, we present a progressive aerodynamic study of a blended wing body (BWB) configuration within a European project, MOB (A computational design engine incorporating multi-disciplinary design and optimisation for blended wing body configuration). The paper starts with an overview of various blended wing body aircraft design projects in relation to their aerodynamic behaviour. After a theoretical assessment of

N. Qin; A. Vavalle; A. Le Moigne; M. Laban; K. Hackett; P. Weinerfelt

2004-01-01

202

Future Computer Requirements for Computational Aerodynamics  

NASA Technical Reports Server (NTRS)

Recent advances in computational aerodynamics are discussed as well as motivations for and potential benefits of a National Aerodynamic Simulation Facility having the capability to solve fluid dynamic equations at speeds two to three orders of magnitude faster than presently possible with general computers. Two contracted efforts to define processor architectures for such a facility are summarized.

1978-01-01

203

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

204

Orion Crew Module Aerodynamic Testing  

NASA Technical Reports Server (NTRS)

The Apollo-derived Orion Crew Exploration Vehicle (CEV), part of NASA s now-cancelled Constellation Program, has become the reference design for the new Multi-Purpose Crew Vehicle (MPCV). The MPCV will serve as the exploration vehicle for all near-term human space missions. A strategic wind-tunnel test program has been executed at numerous facilities throughout the country to support several phases of aerodynamic database development for the Orion spacecraft. This paper presents a summary of the experimental static aerodynamic data collected to-date for the Orion Crew Module (CM) capsule. The test program described herein involved personnel and resources from NASA Langley Research Center, NASA Ames Research Center, NASA Johnson Space Flight Center, Arnold Engineering and Development Center, Lockheed Martin Space Sciences, and Orbital Sciences. Data has been compiled from eight different wind tunnel tests in the CEV Aerosciences Program. Comparisons are made as appropriate to highlight effects of angle of attack, Mach number, Reynolds number, and model support system effects.

Murphy, Kelly J.; Bibb, Karen L.; Brauckmann, Gregory J.; Rhode, Matthew N.; Owens, Bruce; Chan, David T.; Walker, Eric L.; Bell, James H.; Wilson, Thomas M.

2011-01-01

205

Aerodynamics of the hovering hummingbird.  

PubMed

Despite profound musculoskeletal differences, hummingbirds (Trochilidae) are widely thought to employ aerodynamic mechanisms similar to those used by insects. The kinematic symmetry of the hummingbird upstroke and downstroke has led to the assumption that these halves of the wingbeat cycle contribute equally to weight support during hovering, as exhibited by insects of similar size. This assumption has been applied, either explicitly or implicitly, in widely used aerodynamic models and in a variety of empirical tests. Here we provide measurements of the wake of hovering rufous hummingbirds (Selasphorus rufus) obtained with digital particle image velocimetry that show force asymmetry: hummingbirds produce 75% of their weight support during the downstroke and only 25% during the upstroke. Some of this asymmetry is probably due to inversion of their cambered wings during upstroke. The wake of hummingbird wings also reveals evidence of leading-edge vortices created during the downstroke, indicating that they may operate at Reynolds numbers sufficiently low to exploit a key mechanism typical of insect hovering. Hummingbird hovering approaches that of insects, yet remains distinct because of effects resulting from an inherently dissimilar-avian-body plan. PMID:15973407

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

2005-06-23

206

Nonlinear Response of Composite Panels Under Combined Acoustic Excitation and Aerodynamic Pressure  

NASA Technical Reports Server (NTRS)

A finite element formulation is presented for the analysis of large deflection response of composite panels subjected to aerodynamic pressure- at supersonic flow and high acoustic excitation. The first-order shear deformation theory is considered for laminated composite plates, and the von Karman nonlinear strain-displacement relations are employed for the analysis of large deflection panel response. The first-order piston theory aerodynamics and the simulated Gaussian white noise are employed for the aerodynamic and acoustic loads, respectively. The nonlinear equations of motion for an arbitrarily laminated composite panel subjected to a combined aerodynamic and acoustic pressures are formulated first in structure node degrees-of-freedom. The system equations are then transformed and reduced to a set of coupled nonlinear equations in modal coordinates. Modal participation is defined and the in-vacuo modes to be retained in the analysis are based on the modal participation values. Numerical results include root mean square values of maximum deflections, deflection and strain response time histories, probability distributions, and power spectrum densities. Results showed that combined acoustic and aerodynamic loads have to be considered for panel analysis and design at high dynamic pressure values.

Abdel-Motagaly, K.; Duan, B.; Mei, C.

1999-01-01

207

Solve valve noise and cavitation problems  

SciTech Connect

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 of the savings from reduced downtime and lower maintenance costs. Pressure reducing valves used on gases or high pressure steam valves, such as turbine bypass valves, convert substantial energy into heat and a lower pressure level. Unfortunately, this can only be done by accelerating the gas in one or more orifices and then decelerating it rapidly again through a turbulence mechanism or super-sonic shock cells. This causes a lot of noise and vibration. Valve engineering science has made substantial strides in the past few years, and one is now able to predict cavitation and aerodynamic sound levels before a valve is purchased. Similarly, newer valve sizes incorporate features that reduce noise and cavitation effects. Some other minor problems are resonant plug vibration and flashing. The paper discusses how to predict aerodynamic sound, how close can one estimate the sound level, cavitation, and incorrect installation.

Baumann, H.D. [Fisher Controls International, Inc., St. Louis, MO (United States)

1997-03-01

208

Aerodynamics of electrically driven freight pipeline system  

SciTech Connect

This paper examines the aerodynamic characteristics of a freight pipeline system in which freight capsules are individually propelled by electrical motors. The fundamental difference between this system and the more extensively studied pneumatic capsule pipeline is the different role played by aerodynamic forces. In a driven system the propelled capsules are resisted by aerodynamic forces and, in reaction, pump air through the tube. In contrast, in a pneumatically propelled system external blowers pump air through the tubes, and this provides the thrust for the capsules. An incompressible transient analysis is developed to study the aerodynamics of multiple capsules in a cross-linked two-bore pipeline. An aerodynamic friction coefficient is used as a cost parameter to compare the effects of capsule blockage and headway and to assess the merits of adits and vents. The authors conclude that optimum efficiency for off-design operation is obtained with long platoons of capsules in vented or adit connected tubes.

Lundgren, T.S.; Zhao, Y.

2000-06-01

209

YC-14 interior noise measurements program  

NASA Astrophysics Data System (ADS)

A test and preliminary analysis program was conducted to develop a data base and initial understanding of the interior noise of a Upper Surface Blowing STOL airplane using the YC-14 as a test vehicle. A data base has been secured consisting of concurrent cabin noise; exterior fuselage fluctuating pressures; fuselage wall vibrations; and associated aerodynamic, propulsive, and mechanical performance values covering the normal operating envelope of the airplane. Results from preliminary analysis of data show orderly and intuitively reasonable trends. The resultant data base is judged capable of supporting further detailed analysis.

Butzel, L. M.

1981-03-01

210

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

211

Aeroacoustic Study of a High-Fidelity Aircraft Model: Part 1- Steady Aerodynamic Measurements  

NASA Technical Reports Server (NTRS)

In this paper, we present steady aerodynamic measurements for an 18% scale model of a Gulfstream air-craft. The high fidelity and highly-instrumented semi-span model was developed to perform detailed aeroacoustic studies of airframe noise associated with main landing gear/flap components and gear-flap interaction noise, as well as to evaluate novel noise reduction concepts. The aeroacoustic tests, being conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel, are split into two entries. The first entry, completed November 2010, was entirely devoted to the detailed mapping of the aerodynamic characteristics of the fabricated model. Flap deflections of 39?, 20?, and 0? with the main landing gear on and off were tested at Mach numbers of 0.16, 0.20, and 0.24. Additionally, for each flap deflection, the model was tested with the tunnel both in the closed-wall and open-wall (jet) modes. During this first entry, global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Preliminary analysis of the measured forces indicates that lift, drag, and stall characteristics compare favorably with Gulfstream?s high Reynolds number flight data. The favorable comparison between wind-tunnel and flight data allows the semi-span model to be used as a test bed for developing/evaluating airframe noise reduction concepts under a relevant environment. Moreover, initial comparison of the aerodynamic measurements obtained with the tunnel in the closed- and open-wall configurations shows similar aerodynamic behavior. This permits the acoustic and off-surface flow measurements, planned for the second entry, to be conducted with the tunnel in the open-jet mode.

Khorrami, Mehdi R.; Hannon, Judith A.; Neuhart, Danny H.; Markowski, Gregory A.; VandeVen, Thomas

2012-01-01

212

Computation of Supersonic Jet Mixing Noise Using PARC Code With a kappa-epsilon Turbulence Model  

NASA Technical Reports Server (NTRS)

A number of modifications have been proposed in order to improve the jet noise prediction capabilities of the MGB code. This code which was developed at General Electric, employees the concept of acoustic analogy for the prediction of turbulent mixing noise. The source convection and also refraction of sound due to the shrouding effect of the mean flow are accounted for by incorporating the high frequency solution to Lilley's equation for cylindrical jets (Balsa and Mani). The broadband shock-associated noise is estimated using Harper-Bourne and Fisher's shock noise theory. The proposed modifications are aimed at improving the aerodynamic predictions (source/spectrum computations) and allowing for the non- axisymmetric effects in the jet plume and nozzle geometry (sound/flow interaction). In addition, recent advances in shock noise prediction as proposed by Tam can be employed to predict the shock-associated noise as an addition to the jet mixing noise when the flow is not perfectly expanded. Here we concentrate on the aerodynamic predictions using the PARC code with a k-E turbulence model and the ensuing turbulent mixing noise. The geometry under consideration is an axisymmetric convergent-divergent nozzle at its design operating conditions. Aerodynamic and acoustic computations are compared with data as well as predictions due to the original MGB model using Reichardt's aerodynamic theory.

Khavaran, A.; Kim, C. M.

1999-01-01

213

On the application of acoustic 'mirror', 'telescope' and 'polar correlation' techniques to jet noise source location  

Microsoft Academic Search

Three techniques for determining jet noise sources are discussed, the acoustic mirror, telescope, and polar correlation methods. In order to formulate a direct, self-consistent comparison of the methods, relevant jet aerodynamic and acoustic parameters are considered. It is noted that the techniques are limited by the spatial resolution which restricts them to jet noise at higher Strouhal and Mach numbers

H. V. Fuchs

1978-01-01

214

Numerical and analytical modelling of entropy noise in a supersonic nozzle with a shock  

E-print Network

Numerical and analytical modelling of entropy noise in a supersonic nozzle with a shock M. Leyko and Candel [F. Marble, S. Candel, Acoustic disturbances from gas nonuniformities convected through a nozzle Over the last five decades, jet and external aerodynamic noises of aircraft have been substantially r

Boyer, Edmond

215

Numerical and analytical modelling of entropy noise in a supersonic nozzle with a shock  

E-print Network

Numerical and analytical modelling of entropy noise in a supersonic nozzle with a shock M. Leyko a and Candel [Acoustic disturbances from gas nonuniformities convected through a nozzle, Journal of Sound. 1. Introduction Over the last five decades, jet and external aerodynamic noises of aircraft have

Nicoud, Franck

216

Rarefaction Effects in Hypersonic Aerodynamics  

NASA Astrophysics Data System (ADS)

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

Riabov, Vladimir V.

2011-05-01

217

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

2012-01-01

218

System for determining aerodynamic imbalance  

NASA Technical Reports Server (NTRS)

A system is provided for determining tracking error in a propeller or rotor driven aircraft by determining differences in the aerodynamic loading on the propeller or rotor blades of the aircraft. The system includes a microphone disposed relative to the blades during the rotation thereof so as to receive separate pressure pulses produced by each of the blades during the passage thereof by the microphone. A low pass filter filters the output signal produced by the microphone, the low pass filter having an upper cut-off frequency set below the frequency at which the blades pass by the microphone. A sensor produces an output signal after each complete revolution of the blades, and a recording display device displays the outputs of the low pass filter and sensor so as to enable evaluation of the relative magnitudes of the pressure pulses produced by passage of the blades by the microphone during each complete revolution of the blades.

Churchill, Gary B. (inventor); Cheung, Benny K. (inventor)

1994-01-01

219

High angle of attack: Aerodynamics  

NASA Technical Reports Server (NTRS)

The ability to predict high angle of attack, nonlinear, aerodynamic characteristics of flight vehicles, including aircraft, has made significant progress in the last 25 years using computational tools and analyses. The key technological element which has made these analyses possible is the ability to account for the influence of the shed vortical flow, prevalent in this angle of attack range, on geometries of interest. Using selected analysis techniques, applications have also been made to wing design in order to improve their high speed maneuver performance. Various techniques, associated with different levels of accuracy, exist to model this vortical flow influence. The ones included in this paper cover: suction analogy with extensions; free vortex filaments; free vortex sheet modeling; and Euler and Navier-Stokes solutions. Associated relevant features of vortices are also addressed, including: the wing and flow conditions which cause vortex formation; and how the vortex strength varies with angle of attack and wing sweep.

Lamar, John E.

1992-01-01

220

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. PMID:22778638

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

2012-01-01

221

Cyclostationary spectral analysis for the measurement and prediction of wind turbine swishing noise  

NASA Astrophysics Data System (ADS)

This paper introduces cyclostationary spectral analysis as a new approach to analyzing and predicting the aerodynamic noise generated by wind turbines. This method is able to reveal new insights into the periodic character of the noise signal and is therefore ideally suited to the study of wind turbine noise. A new formulation is presented for the time variation of the noise spectrum due to wind turbines thereby providing insight into the character of the periodic variation in noise referred to as 'swishing'. The character and mechanism of swishing noise is analyzed in detail.

Cheong, Cheolung; Joseph, Phillip

2014-07-01

222

Noise Pollution  

Microsoft Academic Search

Noise is playing an ever-increasing role in our lives and seems a regrettable but ultimately avoidable corollary of current\\u000a technology. The trend toward the use of more automated equipment, sports and pleasure craft, high-wattage stereo, larger construction\\u000a machinery, and the increasing numbers of ground vehicles and aircraft has created a gradual acceptance of noise as a natural\\u000a byproduct of progress.

James P. Chambers

223

Transpiration Control Of Aerodynamics Via Porous Surfaces  

NASA Technical Reports Server (NTRS)

Quasi-active porous surface used to control pressure loading on aerodynamic surface of aircraft or other vehicle, according to proposal. In transpiration control, one makes small additions of pressure and/or mass to cavity beneath surface of porous skin on aerodynamic surface, thereby affecting rate of transpiration through porous surface. Porous skin located on forebody or any other suitable aerodynamic surface, with cavity just below surface. Device based on concept extremely lightweight, mechanically simple, occupies little volume in vehicle, and extremely adaptable.

Banks, Daniel W.; Wood, Richard M.; Bauer, Steven X. S.

1993-01-01

224

Performance aerodynamics of aeroassisted orbital transfer vehicles  

NASA Technical Reports Server (NTRS)

A method for predicting the performance aerodynamics of aeroassisted orbital transfer vehicles was developed based on techniques that were used in the aerodynamic databook of the Space Shuttle orbiter and theories from the Hypersonic Arbitrary Body Program. The method spans the entire flight profile of the aeroassisted orbital transfer vehicles from the extreme high altitude non-continuum regime to the highly viscous continuum regime. Results from this method are compared with flight data from the Shuttle orbiter, Apollo Capsule, and the Viking Aeroshell. Finally, performance aerodynamics are estimated for three aeroassisted orbital transfer vehicles that range from low to high lift-to-drag ratio configurations.

Wilhite, A. W.; Arrington, J. P.; Mccandless, R. S.

1984-01-01

225

AERODYNAMICS RESEARCH CENTER MECHANICAL AND AEROSPACE ENGINEERING DEPARTMENT  

E-print Network

09/03/2007 10:42 1 AERODYNAMICS RESEARCH CENTER MECHANICAL AND AEROSPACE ENGINEERING DEPARTMENT Engineering DepartmentMechanical and Aerospace Engineering Department Aerodynamic Research CenterAerodynamic AssociateGraduate Research Associate #12;09/03/2007 10:42 2 AERODYNAMICS RESEARCH CENTER MECHANICAL

Texas at Arlington, University of

226

The External Aerodynamics of Canine Olfaction Gary S. Settles*  

E-print Network

The External Aerodynamics of Canine Olfaction Gary S. Settles* , Douglas A. Kester** , Lori J Literature on the External Aerodynamics of Olfaction B. Precedent Literature on Aerodynamic Sampling Technology III. Canine Olfaction Experiments IV. The Design of an Aerodynamic Sniffer A. Background B

Settles, Gary S.

227

Aerodynamic Shape Optimization Techniques Based On Control Theory  

E-print Network

Aerodynamic Shape Optimization Techniques Based On Control Theory Antony Jameson1 and Luigi for aerodynamic shape design in both inviscid and viscous compressible flow. The theory is applied to a system optimization of complex configurations. 1 Introduction: Aerodynamic Design The definition of the aerodynamic

Jameson, Antony

228

Aerodynamic Shape Optimization for Aircraft Design Antony Jameson  

E-print Network

Aerodynamic Shape Optimization for Aircraft Design Antony Jameson Department of Aeronautics for Aircraft Design #12;#12; Aerodynamic Design Tradeoffs A good first estimate of performance is provided/55 Aerodynamic Shape Optimization for Aircraft Design #12;#12; Aerodynamic Design Tradeoffs The drag coefficient

Stanford University

229

1997 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 1; Configuration Aerodynamics  

NASA Technical Reports Server (NTRS)

The High-Speed Research Program and NASA Langley Research Center sponsored the NASA High-Speed Research Program Aerodynamic Performance Workshop on February 25-28, 1997. The workshop was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High-Lift, Flight Controls, Supersonic Laminar Flow Control, and Sonic Boom Prediction. The workshop objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientist and engineers working HSCT aerodynamics. In particular, single- and multi-point optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT Motion Simulator results were presented along with executive summaries for all the Aerodynamic Performance technology areas.

Baize, Daniel G. (Editor)

1999-01-01

230

Adaptive Neuro-Fuzzy Methodology for Noise Assessment of Wind Turbine  

PubMed Central

Wind turbine noise is one of the major obstacles for the widespread use of wind energy. Noise tone can greatly increase the annoyance factor and the negative impact on human health. Noise annoyance caused by wind turbines has become an emerging problem in recent years, due to the rapid increase in number of wind turbines, triggered by sustainable energy goals set forward at the national and international level. Up to now, not all aspects of the generation, propagation and perception of wind turbine noise are well understood. For a modern large wind turbine, aerodynamic noise from the blades is generally considered to be the dominant noise source, provided that mechanical noise is adequately eliminated. The sources of aerodynamic noise can be divided into tonal noise, inflow turbulence noise, and airfoil self-noise. Many analytical and experimental acoustical studies performed the wind turbines. Since the wind turbine noise level analyzing by numerical methods or computational fluid dynamics (CFD) could be very challenging and time consuming, soft computing techniques are preferred. To estimate noise level of wind turbine, this paper constructed a process which simulates the wind turbine noise levels in regard to wind speed and sound frequency with adaptive neuro-fuzzy inference system (ANFIS). This intelligent estimator is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method. PMID:25075621

Shamshirband, Shahaboddin; Petkovic, Dalibor; Hashim, Roslan; Motamedi, Shervin

2014-01-01

231

1999 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 1; Configuration Aerodynamics  

NASA Technical Reports Server (NTRS)

NASA's High-Speed Research Program sponsored the 1999 Aerodynamic Performance Technical Review on February 8-12, 1999 in Anaheim, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in the areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High Lift, and Flight Controls. The review objectives were to: (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working on HSCT aerodynamics. In particular, single and midpoint optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented, along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program. This Volume 1/Part 1 publication covers configuration aerodynamics.

Hahne, David E. (Editor)

1999-01-01

232

Integrated aerodynamic fin and stowable TVC vane system  

NASA Astrophysics Data System (ADS)

An aerodynamic fin and stowable jet vane system preferably for rocket motor missile applications to control roll, pitch, and yaw, in either the aerodynamic or thrust flight control conditions, has a retractable and stowable aerodynamic vane integrated with a stowable aerodynamic vane integrated with a stowable thrust vector reaction steering system on a common support. The integrated aerodynamic fins and thrust vector control reduce the overall missile mainframe dimensions and are mounted on a single, space saving support.

Danielson, Arnold O.

1994-06-01

233

Device for Reducing Vehicle Aerodynamic Resistance.  

National Technical Information Service (NTIS)

A device for reducing vehicle aerodynamic resistance for vehicles having a generally rectangular body disposed above rear wheels, comprising a plurality of load bearing struts attached to the bottom of the rectangular body adjacent its sides, a plurality ...

S. C. Graham

2004-01-01

234

Uniaxial aerodynamic attitude control of artificial satellites  

NASA Technical Reports Server (NTRS)

Within the context of a simple mechanical model the paper examines the movement of a satellite with respect to the center of masses under conditions of uniaxial aerodynamic attitude control. The equations of motion of the satellite take account of the gravitational and restorative aerodynamic moments. It is presumed that the aerodynamic moment is much larger than the gravitational, and the motion equations contain a large parameter. A two-parameter integrated surface of these equations is constructed in the form of formal series in terms of negative powers of the large parameter, describing the oscillations and rotations of the satellite about its lengthwise axis, approximately oriented along the orbital tangent. It is proposed to treat such movements as nominal undisturbed motions of the satellite under conditions of aerodynamic attitude control. A numerical investigation is made for the above integrated surface.

Sazonov, V. V.

1983-01-01

235

Aerodynamic Characterization of a Modern Launch Vehicle  

NASA Technical Reports Server (NTRS)

A modern launch vehicle is by necessity an extremely integrated design. The accurate characterization of its aerodynamic characteristics is essential to determine design loads, to design flight control laws, and to establish performance. The NASA Ares Aerodynamics Panel has been responsible for technical planning, execution, and vetting of the aerodynamic characterization of the Ares I vehicle. An aerodynamics team supporting the Panel consists of wind tunnel engineers, computational engineers, database engineers, and other analysts that address topics such as uncertainty quantification. The team resides at three NASA centers: Langley Research Center, Marshall Space Flight Center, and Ames Research Center. The Panel has developed strategies to synergistically combine both the wind tunnel efforts and the computational efforts with the goal of validating the computations. Selected examples highlight key flow physics and, where possible, the fidelity of the comparisons between wind tunnel results and the computations. Lessons learned summarize what has been gleaned during the project and can be useful for other vehicle development projects.

Hall, Robert M.; Holland, Scott D.; Blevins, Jhn A.

2011-01-01

236

HSR Aerodynamic Performance Status and Challenges  

NASA Technical Reports Server (NTRS)

This paper describes HSR (High Speed Research) Aerodynamic Performance Status and Challenges. The topics include: 1) Aero impact on HSR; 2) Goals and Targets; 3) Progress and Status; and 4) Remaining Challenges. This paper is presented in viewgraph form.

Gilbert, William P.; Antani, Tony; Ball, Doug; Calloway, Robert L.; Snyder, Phil

1999-01-01

237

16.100 Aerodynamics, Fall 2002  

E-print Network

This course extends fluid mechanic concepts from Unified Engineering to the aerodynamic performance of wings and bodies in sub/supersonic regimes. 16.100 generally has four components: subsonic potential flows, including ...

Darmofal, David L.

238

Aerodynamic gas gates for flare units  

Microsoft Academic Search

Layouts are described for the most productive aerodynamic gates for flare unit pipes with the minimum dimensions. Parameters\\u000a are analyzed for patented gates of two types noted for their structural simplicity.

V. I. Panchenko; Ya. F. Magaril; A. A. Nazarov; Ya. S. Shpaner; R. G. Gimranov

2009-01-01

239

Aerodynamic and Aeroelastic Insights using Eigenanalysis  

NASA Technical Reports Server (NTRS)

This paper presents novel analytical results for eigenvalues and eigenvectors produced using discrete time aerodynamic and aeroelastic models. An unsteady, incompressible vortex lattice aerodynamic model is formulated in discrete time; the importance of several modeling parameters is examined. A detailed study is made of the behavior of the aerodynamic eigenvalues both in discrete and continuous time. The aerodynamic model is then incorporated into aeroelastic equations of motion. Eigenanalyses of the coupled equations produce stability results and modal characteristics which are valid for critical and non-critical velocities. Insight into the modeling and physics associated with aeroelastic system behavior is gained by examining both the eigenvalues and the eigenvectors. Potential pitfalls in discrete time model construction and analysis are examined.

Heeg, Jennifer; Dowell, Earl H.

2004-01-01

240

Vertical Landing Aerodynamics of Reusable Rocket Vehicle  

NASA Astrophysics Data System (ADS)

The aerodynamic characteristics of a vertical landing rocket are affected by its engine plume in the landing phase. The influences of interaction of the engine plume with the freestream around the vehicle on the aerodynamic characteristics are studied experimentally aiming to realize safe landing of the vertical landing rocket. The aerodynamic forces and surface pressure distributions are measured using a scaled model of a reusable rocket vehicle in low-speed wind tunnels. The flow field around the vehicle model is visualized using the particle image velocimetry (PIV) method. Results show that the aerodynamic characteristics, such as the drag force and pitching moment, are strongly affected by the change in the base pressure distributions and reattachment of a separation flow around the vehicle.

Nonaka, Satoshi; Nishida, Hiroyuki; Kato, Hiroyuki; Ogawa, Hiroyuki; Inatani, Yoshifumi

241

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

242

Twenty years' progress in steam turbine aerodynamics  

SciTech Connect

This paper presents a history of the progress made in power plant capacities. The role of aerodynamics in steam turbine development is discussed. The workings of an air research laboratory and a steam research laboratory are explained.

Wallon, M.; Vincent de Paul, M. (Alsthom, Le Bourget (FR)); Anis, A. (Alsthom International, Inc., New York, NY (US))

1989-01-01

243

Efficient aerodynamic shape optimization in MDO context  

NASA Astrophysics Data System (ADS)

Multidisciplinary analysis is necessary to reach physically meaningful optimum designs. For aero-structural shape optimization this means coupling two disciplines--aerodynamics and structural mechanics. In this paper, the sensitivity evaluation for aerodynamic shape optimization is considered, while taking into account the static aeroelastic effects introduced by the variations in the aerodynamic forces, which are associated with changes in the aerodynamic shape. Due to the high computational cost of a finite difference evaluation step for such a coupled problem, an extension of the adjoint approach to aeroelasticity is necessary for an efficient calculation of the sensitivities. The implementation, validation and application of such a method in the MDO context described above are presented.

Fazzolari, Antonio; Gauger, Nicolas R.; Brezillon, Joel

2007-06-01

244

Aerodynamic and Aeroelastic Insights using Eigenanalysis  

NASA Technical Reports Server (NTRS)

This paper presents novel analytical results for eigenvalues and eigenvectors produced using discrete time aerodynamic and aeroelastic models. An unsteady, incompressible vortex lattice aerodynamic model is formulated in discrete time; the importance of several modeling parameters is examined. A detailed study is made of the behavior of the aerodynamic eigenvalues both in discrete and continuous time. The aerodynamic model is then incorporated into aeroelastic equations of motion. Eigenanalyses of the coupled equations produce stability results and modal characteristics which are valid for critical and non-critical velocities. Insight into the modeling and physics associated with aeroelastic system behavior is gained by examining both the eigenvalues and the eigenvectors. Potential pitfalls in discrete time model construction and analysis are examined.

Heeg, Jennifer; Dowell, Earl H.

1999-01-01

245

The aerodynamics of the beautiful game  

E-print Network

We consider the aerodynamics of football, specifically, the interaction between a ball in flight and the ambient air. Doing so allows one to account for the characteristic range and trajectories of balls in flight, as well ...

Bush, John W. M.

2013-01-01

246

Aerodynamics of a rolling airframe missile  

NASA Astrophysics Data System (ADS)

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 configuration that exercises canard steering in phase with body roll position. Measurements were made with the model spinning at steady-state roll rates ranging from 15 to 40 Hz over an angle-of-attack range up to about 16 deg. This short, exploratory investigation has demonstrated that a better understanding and a more complete definition of the aerodynamics of rolling, steering vehicles can be developed by way of simulative wind-tunnel testing.

Tisserand, L. E.

1981-05-01

247

Electromyographic responses to aerodynamic vs. drop handlebars  

E-print Network

differences not revealed by metabolic testing. In this study the electromyography of the rectus femoris, biceps femoris, gluteus maximus, gluteus medius, and low back were recorded during cycling with both aerodynamic handlebars and drop handlebars, Although...

Layne, Donald Jodel

2012-06-07

248

Aerodynamic Analyses Requiring Advanced Computers, Part 1  

NASA Technical Reports Server (NTRS)

Papers are presented which deal with results of theoretical research on aerodynamic flow problems requiring the use of advanced computers. Topics discussed include: viscous flows, boundary layer equations, turbulence modeling and Navier-Stokes equations, and internal flows.

1975-01-01

249

Aerodynamic Analyses Requiring Advanced Computers, part 2  

NASA Technical Reports Server (NTRS)

Papers given at the conference present the results of theoretical research on aerodynamic flow problems requiring the use of advanced computers. Topics discussed include two-dimensional configurations, three-dimensional configurations, transonic aircraft, and the space shuttle.

1975-01-01

250

Jet noise suppression by porous plug nozzles  

NASA Technical Reports Server (NTRS)

Jet noise suppression data presented earlier by Maestrello for porous plug nozzles were supplemented by the testing of a family of nozzles having an equivalent throat diameter of 11.77 cm. Two circular reference nozzles and eight plug nozzles having radius ratios of either 0.53 or 0.80 were tested at total pressure ratios of 1.60 to 4.00. Data were taken both with and without a forward motion or coannular flow jet, and some tests were made with a heated jet. Jet thrust was measured. The data were analyzed to show the effects of suppressor geometry on nozzle propulsive efficiency and jet noise. Aerodynamic testing of the nozzles was carried out in order to study the physical features that lead to the noise suppression. The aerodynamic flow phenomena were examined by the use of high speed shadowgraph cinematography, still shadowgraphs, extensive static pressure probe measurements, and two component laser Doppler velocimeter studies. The different measurement techniques correlated well with each other and demonstrated that the porous plug changes the shock cell structure of a standard nozzle into a series of smaller, periodic cell structures without strong shock waves. These structures become smaller in dimension and have reduced pressure variations as either the plug diameter or the porosity is increased, changes that also reduce the jet noise and decrease thrust efficiency.

Bauer, A. B.; Kibens, V.; Wlezien, R. W.

1982-01-01

251

Aerodynamic response analysis of wind turbines  

Microsoft Academic Search

Wind energy has received increasing attention in the same way as energy crisis and environmental deterioration. The aerodynamic\\u000a response of wind turbines is the major problem in wind turbine design. Blade element momentum theory was used to study the\\u000a aerodynamic thrusts of the blades on the tower. Iterative solutions were used to calculate the axial flow induction factor\\u000a for each

Jing Li; Jianyun Chen; Xiaobo Chen

2011-01-01

252

Improvement of vehicle aerodynamics by wake control  

Microsoft Academic Search

The rear-end shape of a car is one of the most important parts from the view point of aerodynamics. It governs the aerodynamic characteristics of the car, especially drag and rear lift. However, a rear-end shape like a spoiler often increases drag on recent low-drag cars. In this paper, the relation of rear-end shape to drag and lift is studied

Hitoshi Fukuda; Kazuo Yanagimoto; Hiroshi China; Kunio Nakagawa

1995-01-01

253

The Effects of Crosswind Flight on Rotor Harmonic Noise Radiation  

NASA Technical Reports Server (NTRS)

In order to develop recommendations for procedures for helicopter source noise characterization, the effects of crosswinds on main rotor harmonic noise radiation are assessed using a model of the Bell 430 helicopter. Crosswinds are found to have a significant effect on Blade-Vortex Interaction (BVI) noise radiation when the helicopter is trimmed with the fuselage oriented along the inertial flight path. However, the magnitude of BVI noise remains unchanged when the pilot orients the fuselage along the aerodynamic velocity vector, crabbing for zero aerodynamic sideslip. The effects of wind gradients on BVI noise are also investigated and found to be smaller in the crosswind direction than in the headwind direction. The effects of crosswinds on lower harmonic noise sources at higher flight speeds are also assessed. In all cases, the directivity of radiated noise is somewhat changed by the crosswind. The model predictions agree well with flight test data for the Bell 430 helicopter captured under various wind conditions. The results of this investigation would suggest that flight paths for future acoustic flight testing are best aligned across the prevailing wind direction to minimize the effects of winds on noise measurements when wind cannot otherwise be avoided.

Greenwood, Eric; Sim, Ben W.

2013-01-01

254

Aerodynamic performances of three fan stator designs operating with rotor having tip speed of 337 meters per second and pressure ratio of 1.54. 1: Experimental performance  

NASA Technical Reports Server (NTRS)

The aerodynamic performances of four stator-blade rows are presented and evaluated. The aerodynamic designs of two of these stators were compromised to reduce noise, a third design was not. On a calculated operating line passing through the design point pressure ratio, the best stator had overall pressure-ratio and efficiency decrements of 0.031 and 0.044, respectively, providing a stage pressure ratio of 1.483 and efficiency of 0.865. The other stators showed some correctable deficiencies due partly to the design compromises for noise. In the end-wall regions blade-element losses were significantly less for the shortest chord studied.

Gelder, T. F.

1980-01-01

255

Reduction of Background Noise in the NASA Ames 40- by 80-Foot Wind Tunnel  

NASA Technical Reports Server (NTRS)

Background noise in both open-jet and closed wind tunnels adversely affects the signal-to-noise ratio of acoustic measurements. To measure the noise of increasingly quieter aircraft models, the background noise will have to be reduced by physical means or through signal processing. In a closed wind tunnel, such as the NASA Ames 40- by 80- Foot Wind Tunnel, the principle background noise sources can be classified as: (1) fan drive noise; (2) microphone self-noise; (3) aerodynamically induced noise from test-dependent hardware such as model struts and junctions; and (4) noise from the test section walls and vane set. This paper describes the steps taken to minimize the influence of each of these background noise sources in the 40 x 80.

Jaeger, Stephen M.; Allen, Christopher S.; Soderman, Paul T.; Olson, Larry E. (Technical Monitor)

1995-01-01

256

Crackling noise.  

PubMed

Crackling noise arises when a system responds to changing external conditions through discrete, impulsive events spanning a broad range of sizes. A wide variety of physical systems exhibiting crackling noise have been studied, from earthquakes on faults to paper crumpling. Because these systems exhibit regular behaviour over a huge range of sizes, their behaviour is likely to be independent of microscopic and macroscopic details, and progress can be made by the use of simple models. The fact that these models and real systems can share the same behaviour on many scales is called universality. We illustrate these ideas by using results for our model of crackling noise in magnets, explaining the use of the renormalization group and scaling collapses, and we highlight some continuing challenges in this still-evolving field. PMID:11258379

Sethna, J P; Dahmen, K A; Myers, C R

2001-03-01

257

Fourier functional analysis for unsteady aerodynamic modeling  

NASA Technical Reports Server (NTRS)

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

Lan, C. Edward; Chin, Suei

1991-01-01

258

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

259

Parachute Aerodynamics From Video Data  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

260

The aerodynamics of supersonic parachutes  

SciTech Connect

A discussion of the aerodynamics and performance of parachutes flying at supersonic speeds is the focus of this paper. Typical performance requirements for supersonic parachute systems are presented, followed by a review of the literature on supersonic parachute configurations and their drag characteristics. Data from a recent supersonic wind tunnel test series is summarized. The value and limitations of supersonic wind tunnel data on hemisflo and 20-degree conical ribbon parachutes behind several forebody shapes and diameters are discussed. Test techniques were derived which avoided many of the opportunities to obtain erroneous supersonic parachute drag data in wind tunnels. Preliminary correlations of supersonic parachute drag with Mach number, forebody shape and diameter, canopy porosity, inflated canopy diameter and stability are presented. Supersonic parachute design considerations are discussed and applied to a M = 2 parachute system designed and tested at Sandia. It is shown that the performance of parachutes in supersonic flows is a strong function of parachute design parameters and their interactions with the payload wake.

Peterson, C.W.

1987-06-01

261

Aerodynamics of a hybrid airship  

NASA Astrophysics Data System (ADS)

The objective of this paper is to present the results of a numerical study of the aerodynamic parameters of a wingless and a winged-hull airship. The total forces and moment coefficients of the airships have been computed over a range of angles. The results obtained show that addition of a wing to a conventional airship increases the lift has three times the lifting force at positive angle of attack as compared to a wingless airship whereas the drag increases in the range of 19% to 58%. The longitudinal and directional stabilities were found to be statically stable, however, both the conventional airship and the hybrid or winged airships were found to have poor rolling stability. Wingless airship has slightly higher longitudinal stability than a winged airship. The winged airship has better directional stability than the wingless airship. The wingless airship only possesses static rolling stability in the range of yaw angles of -5° to 5°. On the contrary, the winged airship initially tested does not possess rolling stability at all. Computational fluid dynamics (CFD) simulations show that modifications to the wing placement and its dihedral have strong positive effect on the rolling stability. Raising the wings to the center of gravity and introducing a dihedral angle of 5° stabilizes the rolling motion of the winged airship.

Andan, Amelda Dianne; Asrar, Waqar; Omar, Ashraf A.

2012-06-01

262

Radially leaned outlet guide vanes for fan source noise reduction  

NASA Technical Reports Server (NTRS)

Two quiet engine program half scale fans one with a subsonic and the other with a supersonic fan tip speed at takeoff were run with 30 degree leaned and radial outlet guide vanes. Acoustic data at takeoff fan speed on the subsonic tip speed fan showed decreases in 200-foot sideline noise of from 1 to 2 PNdb. The supersonic tip speed fan a takeoff fan speed, however, showed noise increases of up 3 PNdb and a decrease in fan efficiency. At approach fan speed, the subsonic tip speed fan showed a noise decrease of 2.3 PNdb at the 200-foot sideline maximum angle and an increase in efficiency. The supersonic tip speed fan showed noise increase of 3.5 PNdb and no change in efficiency. The decrease in fan efficiency and the nature of the noise increase largely high frequency broadband noise lead to the speculation that an aerodynamic problem occurred.

Kazin, S. B.

1973-01-01

263

Mystery Noises  

NSDL National Science Digital Library

In this game (4th activity on the page) about hearing, learners test their ability to identify various sounds without looking. Suggestions for the sounds include shaking coins, tearing paper, and bouncing a ball. The educator can make the sounds or learners can take turns producing the noises. This activity page includes a link to background information about the ear and hearing.

Chudler, Eric H.

2009-01-01

264

1999 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 1; Configuration Aerodynamics  

NASA Technical Reports Server (NTRS)

NASA's High-Speed Research Program sponsored the 1999 Aerodynamic Performance Technical Review on February 8-12, 1999 in Anaheim, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in the areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High Lift, and Flight Controls. The review objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working on HSCT aerodynamics. In particular, single and midpoint optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented, along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program. This Volume 1/Part 2 publication covers the design optimization and testing sessions.

Hahne, David E. (Editor)

1999-01-01

265

UPWIND, Aerodynamics and aero-elasticity Rotor aerodynamics in atmospheric shear flow  

E-print Network

with zero shear over the rotor disc. In the present work, time true simulations of a rotor in an atmospheric of shear over the rotor disc is typically observed during nights with strongly stable boundary layersUPWIND, Aerodynamics and aero-elasticity Rotor aerodynamics in atmospheric shear flow Niels N

266

Modeling Powered Aerodynamics for the Orion Launch Abort Vehicle Aerodynamic Database  

NASA Technical Reports Server (NTRS)

Modeling the aerodynamics of the Orion Launch Abort Vehicle (LAV) has presented many technical challenges to the developers of the Orion aerodynamic database. During a launch abort event, the aerodynamic environment around the LAV is very complex as multiple solid rocket plumes interact with each other and the vehicle. It is further complicated by vehicle separation events such as between the LAV and the launch vehicle stack or between the launch abort tower and the crew module. The aerodynamic database for the LAV was developed mainly from wind tunnel tests involving powered jet simulations of the rocket exhaust plumes, supported by computational fluid dynamic simulations. However, limitations in both methods have made it difficult to properly capture the aerodynamics of the LAV in experimental and numerical simulations. These limitations have also influenced decisions regarding the modeling and structure of the aerodynamic database for the LAV and led to compromises and creative solutions. Two database modeling approaches are presented in this paper (incremental aerodynamics and total aerodynamics), with examples showing strengths and weaknesses of each approach. In addition, the unique problems presented to the database developers by the large data space required for modeling a launch abort event illustrate the complexities of working with multi-dimensional data.

Chan, David T.; Walker, Eric L.; Robinson, Philip E.; Wilson, Thomas M.

2011-01-01

267

1998 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 1; Configuration Aerodynamics  

NASA Technical Reports Server (NTRS)

NASA's High-Speed Research Program sponsored the 1998 Aerodynamic Performance Technical Review on February 9-13, in Los Angeles, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High-Lift, and Flight Controls. The review objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working HSCT aerodynamics. In particular, single and multi-point optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program.

McMillin, S. Naomi (Editor)

1999-01-01

268

Spring 2011 ME706 Acoustics and Aerodynamic Sound ME706 Acoustics and Aerodynamic Sound  

E-print Network

Spring 2011 ME706 Acoustics and Aerodynamic Sound ME706 Acoustics and Aerodynamic Sound Instructor theory of acoustics; they will serve as an introduction to acoustics for those new to the subject. Great care will be taken to discuss underlying fluid mechanical and acoustic concepts. A considerable number

269

On-road and wind-tunnel measurement of motorcycle helmet noise.  

PubMed

The noise source mechanisms involved in motorcycling include various aerodynamic sources and engine noise. The problem of noise source identification requires extensive data acquisition of a type and level that have not previously been applied. Data acquisition on track and on road are problematic due to rider safety constraints and the portability of appropriate instrumentation. One way to address this problem is the use of data from wind tunnel tests. The validity of these measurements for noise source identification must first be demonstrated. In order to achieve this extensive wind tunnel tests have been conducted and compared with the results from on-track measurements. Sound pressure levels as a function of speed were compared between on track and wind tunnel tests and were found to be comparable. Spectral conditioning techniques were applied to separate engine and wind tunnel noise from aerodynamic noise and showed that the aerodynamic components were equivalent in both cases. The spectral conditioning of on-track data showed that the contribution of engine noise to the overall noise is a function of speed and is more significant than had previously been thought. These procedures form a basis for accurate experimental measurements of motorcycle noise. PMID:23967933

Kennedy, J; Carley, M; Walker, I; Holt, N

2013-09-01

270

1997 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 1; Configuration Aerodynamics  

NASA Technical Reports Server (NTRS)

The High-Speed Research Program and NASA Langley Research Center sponsored the NASA High-Speed Research Program Aerodynamic Performance Workshop on February 25-28, 1997. The workshop was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in area of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High-Lift, Flight Controls, Supersonic Laminar Flow Control, and Sonic Boom Prediction. The workshop objectives were to (1) report the progress and status of HSCT aerodyamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientist and engineers working HSCT aerodynamics. In particular, single- and multi-point optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT Motion Simulator results were presented along with executive summaries for all the Aerodynamic Performance technology areas.

Baize, Daniel G. (Editor)

1999-01-01

271

In vivo recording of aerodynamic force with an aerodynamic force platform  

E-print Network

Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on tethered experiments with robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here we demonstrate a new aerodynamic force platform (AFP) for nonintrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is ...

Lentink, David; Ingersoll, Rivers

2014-01-01

272

Aerodynamic heating in hypersonic flows  

NASA Technical Reports Server (NTRS)

Aerodynamic heating in hypersonic space vehicles is an important factor to be considered in their design. Therefore the designers of such vehicles need reliable heat transfer data in this respect for a successful design. Such data is usually produced by testing the models of hypersonic surfaces in wind tunnels. Most of the hypersonic test facilities at present are conventional blow-down tunnels whose run times are of the order of several seconds. The surface temperatures on such models are obtained using standard techniques such as thin-film resistance gages, thin-skin transient calorimeter gages and coaxial thermocouple or video acquisition systems such as phosphor thermography and infrared thermography. The data are usually reduced assuming that the model behaves like a semi-infinite solid (SIS) with constant properties and that heat transfer is by one-dimensional conduction only. This simplifying assumption may be valid in cases where models are thick, run-times short, and thermal diffusivities small. In many instances, however, when these conditions are not met, the assumption may lead to significant errors in the heat transfer results. The purpose of the present paper is to investigate this aspect. Specifically, the objectives are as follows: (1) to determine the limiting conditions under which a model can be considered a semi-infinite body; (2) to estimate the extent of errors involved in the reduction of the data if the models violate the assumption; and (3) to come up with correlation factors which when multiplied by the results obtained under the SIS assumption will provide the results under the actual conditions.

Reddy, C. Subba

1993-01-01

273

The aerodynamics of insect flight.  

PubMed

The flight of insects has fascinated physicists and biologists for more than a century. Yet, until recently, researchers were unable to rigorously quantify the complex wing motions of flapping insects or measure the forces and flows around their wings. However, recent developments in high-speed videography and tools for computational and mechanical modeling have allowed researchers to make rapid progress in advancing our understanding of insect flight. These mechanical and computational fluid dynamic models, combined with modern flow visualization techniques, have revealed that the fluid dynamic phenomena underlying flapping flight are different from those of non-flapping, 2-D wings on which most previous models were based. In particular, even at high angles of attack, a prominent leading edge vortex remains stably attached on the insect wing and does not shed into an unsteady wake, as would be expected from non-flapping 2-D wings. Its presence greatly enhances the forces generated by the wing, thus enabling insects to hover or maneuver. In addition, flight forces are further enhanced by other mechanisms acting during changes in angle of attack, especially at stroke reversal, the mutual interaction of the two wings at dorsal stroke reversal or wing-wake interactions following stroke reversal. This progress has enabled the development of simple analytical and empirical models that allow us to calculate the instantaneous forces on flapping insect wings more accurately than was previously possible. It also promises to foster new and exciting multi-disciplinary collaborations between physicists who seek to explain the phenomenology, biologists who seek to understand its relevance to insect physiology and evolution, and engineers who are inspired to build micro-robotic insects using these principles. This review covers the basic physical principles underlying flapping flight in insects, results of recent experiments concerning the aerodynamics of insect flight, as well as the different approaches used to model these phenomena. PMID:14581590

Sane, Sanjay P

2003-12-01

274

Low Noise Research Fan Stage Design  

NASA Technical Reports Server (NTRS)

This report describes the design of a Low Noise ADP Research Fan stage. The fan is a variable pitch design which is designed at the cruise pitch condition. Relative to the cruise setting, the blade is closed at takeoff and opened for reverse thrust operation. The fan stage is a split flow design with fan exit guide vanes and core stators. This fan stage design was combined with a nacelle and engine core duct to form a powered fan/nacelle, subscale model. This model is intended for use in aerodynamic performance, acoustic and structural testing in a wind tunnel. The model has a 22-inch outer fan diameter and a hub-to-top ratio of 0.426 which permits the use of existing NASA fan and cowl force balance designs and rig drive system. The design parameters were selected to permit valid acoustic and aerodynamic comparisons with the PW 17-inch rig previously tested under NASA contract. The fan stage design is described in detail. The results of the design axisymmetric analysis at aerodynamic design condition are included. The structural analysis of the fan rotor and attachment is described including the material selections and stress analysis. The blade and attachment are predicted to have adequate low cycle fatigue life, and an acceptable operating range without resonant stress or flutter. The stage was acoustically designed with airfoil counts in the fan exit guide vane and core stator to minimize noise. A fan-FEGV tone analysis developed separately under NASA contract was used to determine these airfoil counts. The fan stage design was matched to a nacelle design to form a fan/nacelle model for wind tunnel testing. The nacelle design was developed under a separate NASA contract. The nacelle was designed with an axisymmetric inlet, cowl and nozzle for convenience in testing and fabrication. Aerodynamic analysis of the nacelle confirmed the required performance at various aircraft operating conditions.

Hobbs, David E.; Neubert, Robert J.; Malmborg, Eric W.; Philbrick, Daniel H.; Spear, David A.

1995-01-01

275

Test-section noise of the Ames 7 by 10-foot wind tunnel no. 1  

NASA Technical Reports Server (NTRS)

An investigation was made of the test-section noise levels at various wind speeds in the Ames 7- by 10-Foot Wind Tunnel No. 1. No model was in the test section. Results showed that aerodynamic noise from various struts used to monitor flow conditions in the test section dominated the wind-tunnel background noise over much of the frequency spectrum. A tapered microphone stand with a thin trailing edge generated less noise than did a constant-chord strut with a blunt trailing edge. Noise from small holes in the test-section walls was insignificant.

Soderman, P. T.

1976-01-01

276

Missile Aerodynamics for Ascent and Re-entry  

NASA Technical Reports Server (NTRS)

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

Watts, Gaines L.; McCarter, James W.

2012-01-01

277

Take-off aerodynamics in ski jumping.  

PubMed

The effect of aerodynamic forces on the force-time characteristics of the simulated ski jumping take-off was examined in a wind tunnel. Vertical and horizontal ground reaction forces were recorded with a force plate installed under the wind tunnel floor. The jumpers performed take-offs in non-wind conditions and in various wind conditions (21-33 m s(-1)). EMGs of the important take-off muscles were recorded from one jumper. The dramatic decrease in take-off time found in all jumpers can be considered as the result of the influence of aerodynamic lift. The loss in impulse due to the shorter force production time with the same take-off force is compensated with the increase in lift force, resulting in a higher vertical velocity (V(v)) than is expected from the conventional calculation of V(v) from the force impulse. The wind conditions emphasized the explosiveness of the ski jumping take-off. The aerodynamic lift and drag forces which characterize the aerodynamic quality of the initial take-off position (static in-run position) varied widely even between the examined elite ski jumpers. According to the computer simulation these differences can decisively affect jumping distance. The proper utilization of the prevailing aerodynamic forces before and during take-off is a very important prerequisite for achieving a good flight position. PMID:11266669

Virmavirta, M; Kivekäs, J; Komi, P V

2001-04-01

278

Control of maglev vehicles with aerodynamic and guideway disturbances  

NASA Technical Reports Server (NTRS)

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

1994-01-01

279

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

280

An analysis of blade vortex interaction aerodynamics and acoustics  

NASA Technical Reports Server (NTRS)

The impulsive noise associated with helicopter flight due to Blade-Vortex Interaction, sometimes called blade slap is analyzed especially for the case of a close encounter of the blade-tip vortex with a following blade. Three parts of the phenomena are considered: the tip-vortex structure generated by the rotating blade, the unsteady pressure produced on the following blade during the interaction, and the acoustic radiation due to the unsteady pressure field. To simplify the problem, the analysis was confined to the situation where the vortex is aligned parallel to the blade span in which case the maximum acoustic pressure results. Acoustic radiation due to the interaction is analyzed in space-fixed coordinates and in the time domain with the unsteady pressure on the blade surface as the source of chordwise compact, but spanwise non-compact radiation. Maximum acoustic pressure is related to the vortex core size and Reynolds number which are in turn functions of the blade-tip aerodynamic parameters. Finally noise reduction and performance are considered.

Lee, D. J.

1985-01-01

281

Significance of shock structure on supersonic jet mixing noise of axisymmetric nozzles  

NASA Technical Reports Server (NTRS)

One of the key technical elements in NASA's high speed research program is reducing the noise level to meet the federal noise regulation. The dominant noise source is associated with the supersonic jet discharged from the engine exhaust system. Whereas the turbulence mixing is largely responsible for the generation of the jet noise, a broadband shock-associated noise is also generated when the nozzle operates at conditions other than its design. For both mixing and shock noise components, because the source of the noise is embedded in the jet plume, one can expect that jet noise can be predicted from the jet flowfield computation. Mani et al. developed a unified aerodynamic/acoustic prediction scheme by applying an extension of Reichardt's aerodynamic model to compute turbulent shear stresses which are utilized in estimating the strength of the noise source. Although this method produces a fast and practical estimate of the jet noise, a modification by Khavaran et al. has led to an improvement in aerodynamic solution. The most notable feature in this work is that Reichardt's model is replaced with the computational fluid dynamics (CFD) solution of Reynolds-averaged Navier-Stokes equations. The major advantage of this work is that the essential, noise-related flow quantities such as turbulence intensity and shock strength can be better predicted. The predictions were limited to a shock-free design condition and the effect of shock structure on the jet mixing noise was not addressed. The present work is aimed at investigating this issue. Under imperfectly expanded conditions the existence of the shock cell structure and its interaction with the convecting turbulence structure may not only generate a broadband shock-associated noise but also change the turbulence structure, and thus the strength of the mixing noise source. Failure in capturing shock structures properly could lead to incorrect aeroacoustic predictions.

Kim, Chan M.; Krejsa, Eugene A.; Khavaran, Abbas

1994-01-01

282

Community noise sources and noise control issues  

NASA Technical Reports Server (NTRS)

The topics covered include the following: community noise sources and noise control issues; noise components for turbine bypass turbojet engine (TBE) turbojet; engine cycle selection and noise; nozzle development schedule; NACA nozzle design; NACA nozzle test results; nearly fully mixed (NFM) nozzle design; noise versus aspiration rate; peak noise test results; nozzle test in the Low Speed Aeroacoustic Facility (LSAF); and Schlieren pictures of NACA nozzle.

Nihart, Gene L.

1992-01-01

283

Aerodynamic and acoustic behavior of a YF-12 inlet at static conditions  

NASA Technical Reports Server (NTRS)

An aeroacoustic test program to determine the cause of YF-12 inlet noise suppression was performed with a YF-12 aircraft at ground static conditions. Data obtained over a wide range of engine speeds and inlet configurations are reported. Acoustic measurements were made in the far field and aerodynamic and acoustic measurements were made inside the inlet. The J-58 test engine was removed from the aircraft and tested separately with a bellmouth inlet. The far field noise level was significantly lower for the YF-12 inlet than for the bellmouth inlet at engine speeds above 5500 rpm. There was no evidence that noise suppression was caused by flow choking. Multiple pure tones were reduced and the spectral peak near the blade passing frequency disappeared in the region of the spike support struts at engine speeds between 6000 and 6600 rpm.

Bangert, L. H.; Feltz, E. P.; Godby, L. A.; Miller, L. D.

1981-01-01

284

Design of low noise wind turbine blades using Betz and Joukowski concepts  

NASA Astrophysics Data System (ADS)

This paper presents the aerodynamic design of low noise wind turbine blades using Betz and Joukowski concepts. The aerodynamic model is based on Blade Element Momentum theory whereas the aeroacoustic prediction model is based on the BPM model. The investigation is started with a 3MW baseline/reference turbine rotor with a diameter of 80 m. To reduce the noise emission from the baseline rotor, the rotor is reconstructed with the low noise CQU-DTU-LN1 series of airfoils which has been tested in the acoustic wind tunnel located at Virginia Tech. Finally, 3MW low noise turbine rotors are designed using the concepts of Betz and Joukowski, and the CQU-DTU-LN1 series of airfoils. Performance analysis shows that the newly designed turbine rotors can achieve an overall noise reduction of 6 dB and 1.5 dB(A) with a similar power output as compared to the reference rotor.

Shen, W. Z.; Hrgovan, I.; Okulov, V.; Zhu, W. J.; Madsen, J.

2014-06-01

285

Hydrodynamic noise-Murray Strasberg's legacy.  

PubMed

The decade of the 1950s provided us with the beginnings of sub-disciplines of acoustics that we now call aeroacoustics and hydroacoustics. In the beginning, the attention was placed on mechanisms relevant to the aeronautical engineering and the early rocket and space vehicle communities. Accordingly, much published work at the time dealt with jet noise and structural fatigue resulting from that noise and from turbulent boundary layer excitation. In 1956, Murray Strasberg and Hugh Fitzpatrick published a seminal paper, "Hydrodynamic Sources of Sound", 1st Hydrodynamics Symposium. This paper put the aerodynamic noise theory of Lighthill (1952) in the context of Navy application and defined relevant source types. A. Prosperetti will discuss Murray's legacy regarding bubble noise and cavitation discussed in that paper. I will discuss the other interest of Murray: i.e., flow induced vibration and sound. Although he published little on this subject the impact that he had on others who did was important. Accordingly, Murray had continuing impact on the developing knowledgebase of flow-induced sound and vibration, and we will use the area of TBL noise as an example of how concepts in flow noise and vibration have evolved under Murray's career span. PMID:25235559

Blake, William

2014-04-01

286

Status of Nozzle Aerodynamic Technology at MSFC  

NASA Technical Reports Server (NTRS)

This viewgraph presentation provides information on the status of nozzle aerodynamic technology at MSFC (Marshall Space Flight Center). The objectives of this presentation were to provide insight into MSFC in-house nozzle aerodynamic technology, design, analysis, and testing. Under CDDF (Center Director's Discretionary Fund), 'Altitude Compensating Nozzle Technology', are the following tasks: Development of in-house ACN (Altitude Compensating Nozzle) aerodynamic design capability; Building in-house experience for all aspects of ACN via End-to-End Nozzle Test Program; Obtaining Experimental Data for Annular Aerospike: Thrust eta, TVC (thrust vector control) capability and surface pressures. To support selection/optimization of future Launch Vehicle propulsion we needed a parametric design and performance tool for ACN. We chose to start with the ACN Aerospike Nozzles.

Ruf, Joseph H.; McDaniels, David M.; Smith, Bud; Owens, Zachary

2002-01-01

287

Aerodynamics of magnetic levitation (MAGLEV) trains  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

288

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

289

History of the numerical aerodynamic simulation program  

NASA Technical Reports Server (NTRS)

The Numerical Aerodynamic Simulation (NAS) program has reached a milestone with the completion of the initial operating configuration of the NAS Processing System Network. This achievement is the first major milestone in the continuing effort to provide a state-of-the-art supercomputer facility for the national aerospace community and to serve as a pathfinder for the development and use of future supercomputer systems. The underlying factors that motivated the initiation of the program are first identified and then discussed. These include the emergence and evolution of computational aerodynamics as a powerful new capability in aerodynamics research and development, the computer power required for advances in the discipline, the complementary nature of computation and wind tunnel testing, and the need for the government to play a pathfinding role in the development and use of large-scale scientific computing systems. Finally, the history of the NAS program is traced from its inception in 1975 to the present time.

Peterson, Victor L.; Ballhaus, William F., Jr.

1987-01-01

290

Nonlinear aerodynamic modeling using multivariate orthogonal functions  

NASA Technical Reports Server (NTRS)

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

Morelli, Eugene A.

1993-01-01

291

Summary analysis of the Gemini entry aerodynamics  

NASA Technical Reports Server (NTRS)

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, 8, 10, 11, and 12 missions. For the Gemini, 5, 8, 10, 11, and 12 missions, the flight-generated lift-to-drag ratios and corresponding angles of attack are compared with the wind tunnel data. These comparisons show that the flight generated lift-to-drag ratios are consistently lower than were anticipated from the tunnel data. Numerous data uncertainties are cited that provide an insight into the problems that are related to an analysis of flight data developed from instrumentation systems, the primary functions of which are other than the evaluation of flight aerodynamic performance.

Whitnah, A. M.; Howes, D. B.

1972-01-01

292

Aerodynamic properties of spherical balloon wind sensors.  

NASA Technical Reports Server (NTRS)

A first-order theory of the fluctuating lift and drag coefficients associated with the aerodynamically induced motions of rising and falling spherical wind sensors is developed. The equations of motion of a sensor are perturbed about an equilibrium state in which the buoyancy force balances the mean vertical drag force. It is shown that, to within first order in perturbation quantities, the aerodynamic lift force is confined to the horizontal, and the fluctuating drag force associated with fluctuations in the drag coefficient acts along the vertical. The perturbation equations are transformed with Fourier-Stieltjes integrals. The resulting equations lead to relationships between the power spectra of the aerodynamically induced velocity components and the spectra of the fluctuating lift and drag coefficients.

Fichtl, G. H.; Demandel, R. E.; Krivo, S. J.

1972-01-01

293

Physics of badminton shuttlecocks. Part 1 : aerodynamics  

NASA Astrophysics Data System (ADS)

We study experimentally shuttlecocks dynamics. In this part we show that shuttlecock trajectory is highly different from classical parabola. When one takes into account the aerodynamic drag, the flight of the shuttlecock quickly curves downwards and almost reaches a vertical asymptote. We solve the equation of motion with gravity and drag at high Reynolds number and find an analytical expression of the reach. At high velocity, this reach does not depend on velocity anymore. Even if you develop your muscles you will not manage to launch the shuttlecock very far because of the ``aerodynamic wall.'' As a consequence you can predict the length of the field. We then discuss the extend of the aerodynamic wall to other projectiles like sports balls and its importance.

Cohen, Caroline; Darbois Texier, Baptiste; Quéré, David; Clanet, Christophe

2011-11-01

294

Aerodynamic/acoustic performance of YJ101/double bypass VCE with coannular plug nozzle  

NASA Technical Reports Server (NTRS)

Results of a forward Variable Area Bypass Injector test and a Coannular Nozzle test performed on a YJ101 Double Bypass Variable Cycle Engine are reported. These components are intended for use on a Variable Cycle Engine. The forward Variable Area Bypass Injector test demonstrated the mode shifting capability between single and double bypass operation with less than predicted aerodynamic losses in the bypass duct. The acoustic nozzle test demonstrated that coannular noise suppression was between 4 and 6 PNdB in the aft quadrant. The YJ101 VCE equipped with the forward VABI and the coannular exhaust nozzle performed as predicted with exhaust system aerodynamic losses lower than predicted both in single and double bypass modes. Extensive acoustic data were collected including far field, near field, sound separation/ internal probe measurements as Laser Velocimeter traverses.

Vdoviak, J. W.; Knott, P. R.; Ebacker, J. J.

1981-01-01

295

Control of Environmental Noise  

ERIC Educational Resources Information Center

Discusses the physical properties, sources, physiological effects, and legislation pertaining to noise, especially noise characteristics in the community. Indicates that noise reduction steps can be taken more intelligently after determination of the true noise sources and paths. (CC)

Jensen, Paul

1973-01-01

296

Silicon carbide whiskers: Characterization and aerodynamic behaviors  

SciTech Connect

Silicon carbide (SiC) whiskers are fiberlike materials with a wide range of industrial applications. Industrial hygiene samplings of the material are taken to monitor and control possible exposures to workers. This study characterizes an SiC whisker in detail, including its width-length distribution, aspect ratio, particle density, and aerodynamic size distribution. The SiC whiskers were aerosolized, and samples from a filter, cascade impactor, and aerosol centrifuge were taken. The diameter-length distribution of SiC fibers determined by electron microscopy from filter samples was found to follow the bivariate lognormal distribution. The aerodynamic size of a fiber aerosol depends not only on the particle dimension and density but also on the orientation of its axis with respect to flow. The results show that the aerodynamic size distribution obtained from the impactor was consistent with the predicted value, assuming the long axis of the fiber was parallel to the flow toward the collection substrate. On the other hand, the aerodynamic size in the aerosol centrifuge was consistent with results for a perpendicular orientation. A larger aerodynamic size (20--25%) was obtained in the case of impactor data as compared with centrifuge data. The respirable fraction estimated from the cascade impactor data was 65%, consistent with the estimate from bivariate analysis (67%) but smaller than the estimated fraction from the aerosol centrifuge (76%). The results show that the data obtained with the bivariate analysis of fiber dimensions had good correlation with the cascade impactor data, and this approach can be used to predict the aerodynamic size distribution and the size-selective fractions for fiber aerosols from filter samples.

Cheng, Y.S.; Smith, S.M.; Johnson, N.F. [Inhalation Toxicology Research Inst., Albuquerque, NM (United States)] [Inhalation Toxicology Research Inst., Albuquerque, NM (United States); Powell, Q.H. [Univ. of New Mexico, Albuquerque, NM (United States)] [Univ. of New Mexico, Albuquerque, NM (United States)

1995-10-01

297

Rarefaction Effects in Hypersonic Aerodynamics Vladimir V. Riabov  

E-print Network

Rarefaction Effects in Hypersonic Aerodynamics Vladimir V. Riabov Department of Mathematics Monte-Carlo (DSMC) technique is used for numerical analysis of rarefied-gas hypersonic flows near. Keywords: DSMC method, aerodynamic coefficients, hypersonic flows, similarity parameters, torus, spinning

Riabov, Vladimir V.

298

Visualization of aerodynamic flow fields using photorefractive crystals  

E-print Network

Visualization of aerodynamic flow fields using photorefractive crystals A. Hafiz, R. Magnusson, J holographyinphotorefractive crystals isapplied for visualization of aerodynamic flow fields. The interferograms obtained presented are obtained using ahigh-powercwargon laserand iron dopedlithium niobate crystals

Texas at Arlington, University of

299

Aerodynamic detuning analysis of an unstalled supersonic turbofan cascade  

NASA Technical Reports Server (NTRS)

An approach to passive flutter control is aerodynamic detuning, defined as designed passage-to-passage differences in the unsteady aerodynamic flow field of a rotor blade row. Thus, aerodynamic detuning directly affects the fundamental driving mechanism for flutter. A model to demonstrate the enhanced supersonic aeroelastic stability associated with aerodynamic detuning is developed. The stability of an aerodynamically detuned cascade operating in a supersonic inlet flow field with a subsonic leading edge locus is analyzed, with the aerodynamic detuning accomplished by means of nonuniform circumferential spacing of adjacent rotor blades. The unsteady aerodynamic forces and moments on the blading are defined in terms of influence coefficients in a manner that permits the stability of both a conventional uniformally spaced rotor configuration as well as the detuned nonuniform circumferentially spaced rotor to be determined. With Verdon's uniformly spaced Cascade B as a baseline, this analysis is then utilized to demonstrate the potential enhanced aeroelastic stability associated with this particular type of aerodynamic detuning.

Hoyniak, D.; Fleeter, S.

1985-01-01

300

Aerodynamic Heating Measurements on Hypersonic Flight Exoerunebt (HYFLEX) Vehicle.  

National Technical Information Service (NTIS)

Aerodynamic heating on the Hypersonic Flight Experiment vehicle was measured using newly developed sensors, calibrated by lamp heating tests. These sensors were shown to be of sue for flight measurement purposes. The results of the aerodynamic heating mea...

K. Fujii, S. Watanabe, M. Shirouzu, Y. Inoue, T. Kurotaki, T. Koyama, S. Tsuda, N. Hirabayashi

2000-01-01

301

Air flow testing on aerodynamic truck  

NASA Technical Reports Server (NTRS)

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

1975-01-01

302

Wind turbine blade aerodynamics: The combined experiment  

SciTech Connect

Data obtained from the National Renewable Energy Laboratory site test of a wind turbine (The Combined Experiment) was analyzed specifically to capture information regarding the aerodynamic loading experienced by such machines. The analysis showed that inflow conditions were extremely variable and that these inflows yielded three different operational regimes. Each regime produces very different aerodynamic loading conditions that must be tolerated by the turbine. The two conditions not predicted from wind tunnel data are being subjected to further analyses to provide new guidelines for both designers and operators.

Robinson, M.C.; Luttges, M.W.; Miller, M.S.; Shipley, D.E.; Young, T.S. [Colorado Univ., Boulder, CO (United States). Dept. of Aerospace Engineering Sciences

1994-08-01

303

Influence of aerodynamic forces in ice shedding  

NASA Technical Reports Server (NTRS)

Stresses in accreted ice on a typical airfoil impact ice caused by aerodynamic forces have been studied using finite element analyses. The objective of this study is to determine the significance of these stresses relative to values needed to cause ice shedding. In the case studied, stresses are not significant (less than 10 percent) when compared to the fracture value for airspeeds below a Mach number of 0.45. Above this velocity, the influence of aerodynamic forces on impact ice stresses should be considered in analyses of ice shedding.

Scavuzzo, R. J.; Chu, M. L.; Ananthaswamy, V.

1991-01-01

304

Aerodynamic: Applications of Force and Flow  

NSDL National Science Digital Library

This resource guide from the Middle School Portal 2 project, written specifically for teachers, provides links to exemplary resources including background information, lessons, career information, and related national science education standards. Although there is a great deal of historical information about aerodynamics that could be discussed here, we purposely narrowed the stream of resources to those that encourage students to experiment with technological design and function. Given these learning experiences, student should be prepared to articulate preferences in vehicle design and understand how the principles of aerodynamics influence vehicle performance.

Briggs, Quentin

2005-03-01

305

Unstructured mesh algorithms for aerodynamic calculations  

NASA Technical Reports Server (NTRS)

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 emphasized. The various aspects required for the efficient and accurate solution of aerodynamic flows are addressed. These include mesh generation, mesh adaptivity, solution algorithms, convergence acceleration, and turbulence modeling. Computations of viscous turbulent two-dimensional flows and inviscid three-dimensional flows about complex configurations are demonstrated. Remaining obstacles and directions for future research are also outlined.

Mavriplis, D. J.

1992-01-01

306

Method of reducing drag in aerodynamic systems  

NASA Technical Reports Server (NTRS)

In the present method, boundary layer thickening is combined with laminar flow control to reduce drag. An aerodynamic body is accelerated enabling a ram turbine on the body to receive air at velocity V sub 0. The discharge air is directed over an aft portion of the aerodynamic body producing boundary layer thickening. The ram turbine also drives a compressor by applying torque to a shaft connected between the ram turbine and the compressor. The compressor sucks in lower boundary layer air through inlets in the shell of the aircraft producing laminar flow control and reducing drag. The discharge from the compressor is expanded in a nozzle to produce thrust.

Hrach, Frank J. (inventor)

1993-01-01

307

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

308

On Noise Assessment for Blended Wing Body Aircraft  

NASA Technical Reports Server (NTRS)

A system noise study is presented for the blended-wing-body (BWB) aircraft configured with advanced technologies that are projected to be available in the 2025 timeframe of the NASA N+2 definition. This system noise assessment shows that the noise levels of the baseline configuration, measured by the cumulative Effective Perceived Noise Level (EPNL), have a large margin of 34 dB to the aircraft noise regulation of Stage 4. This confirms the acoustic benefits of the BWB shielding of engine noise, as well as other projected noise reduction technologies, but the noise margins are less than previously published assessments and are short of meeting the NASA N+2 noise goal. In establishing the relevance of the acoustic assessment framework, the design of the BWB configuration, the technical approach of the noise analysis, the databases and prediction tools used in the assessment are first described and discussed. The predicted noise levels and the component decomposition are then analyzed to identify the ranking order of importance of various noise components, revealing the prominence of airframe noise, which holds up the levels at all three noise certification locations and renders engine noise reduction technologies less effective. When projected airframe component noise reduction is added to the HWB configuration, it is shown that the cumulative noise margin to Stage 4 can reach 41.6 dB, nearly at the NASA goal. These results are compared with a previous NASA assessment with a different study framework. The approaches that yield projections of such low noise levels are discussed including aggressive assumptions on future technologies, assumptions on flight profile management, engine installation, and component noise reduction technologies. It is shown that reliable predictions of component noise also play an important role in the system noise assessment. The comparisons and discussions illustrate the importance of practical feasibilities and constraints in aircraft system noise studies, which include aerodynamic performance, propulsion efficiency, flight profile limitation and many other factors. For a future aircraft concept to achieve the NASA N+2 noise goal it will require a range of fully successful noise reduction technology developments.

Guo, Yueping; Burley, Casey L; Thomas, Russell H.

2014-01-01

309

Investigation of noise suppression by sonic inlets for turbofan engines. Volume 1: Program summary  

NASA Technical Reports Server (NTRS)

Results of a program for sonic inlet technology development are presented. This program includes configuration and mechanical design selection of concepts, aerodynamic design description of the models, and results of test evaluation. Several sonic inlet concepts were tested and compared for aerodynamic and acoustic performance. Results of these comparative evaluations are presented. Near-field measurements were taken inside several of the inlet models. Results of these tests are discussed with respect to the effect of Mach number gradients on noise attenuation and rotor shock wave attenuation, and boundary layer effects on noise propagation. The test facilities and experimental techniques employed are described briefly.

Klujber, F.; Bosch, J. C.; Demetrick, R. W.; Robb, W. L.

1973-01-01

310

A Fan Design that Meets the NASA Aeronautics Noise Goals  

NASA Technical Reports Server (NTRS)

A fan concept was previously identified that would meet the NASA aeronautics goal of a 20 EPNdB reduction in aircraft noise. This was a 2-stage fan with a pressure ratio of 1.15 and a 460 ft/sec tip speed. The 2 stages were identical so that, with the proper synchrophasing, noise from one stage could be used to cancel noise from the other stage. This paper documents the aerodynamic design of the 2-stage fan concept in a 22-in. diameter size for testing in the NASA Glenn 9- by 15-ft wind tunnel. A set of rotor and stator coordinates are listed in the report. Stress and flutter analyses were done on these blades and showed that the design was structurally viable. A noise prediction code, using the blade coordinates and fan flows, indicated that the 2-stage fan would meet the goal of a 20 dB reduction in fan noise.

Dittmar, James; Tweedt, Daniel; Jeracki, Robert; Envia, Edmaine; Bartos, Karen; Slater, John

2003-01-01

311

OUTLINE FOR Chapter 3 AERODYNAMICS (W2-1-1)  

E-print Network

2013/4/22 1 OUTLINE FOR Chapter 3 AERODYNAMICS (W2-1-1) BERNOULLI'S EQUATION & integration AERODYNAMICS (W2-1-2) BERNOULLI'S EQUATION #12;2013/4/22 2 BERNOULLI'S EQUATION FOR AN IRROTATION FLOW AERODYNAMICS (W2-1-2.1) VENTURI TUBE AERODYNAMICS (W2-1-3) #12;2013/4/22 3 PITOT-STATIC TUBE for subsonic

Leu, Tzong-Shyng "Jeremy"

312

Noise Pollution  

NSDL National Science Digital Library

This learning activity from the Advanced Technology Environmental and Energy Center (ATEEC) will provide students with a field exercise that allows them to measure noise pollution and interpret the data collected. The field exercise should take about 2-3 hours to complete, depending upon travel time to sample sites, and requires a few additional materials which are detailed in the lesson. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

Winterbottom, Wesley L.

2011-02-14

313

Noise Abatement  

NASA Technical Reports Server (NTRS)

SMART, Sound Modification and Regulated Temperature compound, is a liquid plastic mixture with exceptional energy and sound absorbing qualities. It is derived from a very elastic plastic which was an effective noise abatement material in the Apollo Guidance System. Discovered by a NASA employee, it is marketed by Environmental Health Systems, Inc. (EHS). The product has been successfully employed by a diaper company with noisy dryers and a sugar company with noisy blowers. The company also manufactures an audiometric test booth and acoustical office partitions.

1983-01-01

314

Efficient Helicopter Aerodynamic and Aeroacoustic Predictions on Parallel Computers  

NASA Technical Reports Server (NTRS)

This paper presents parallel implementations of two codes used in a combined CFD/Kirchhoff methodology to predict the aerodynamics and aeroacoustics properties of helicopters. The rotorcraft Navier-Stokes code, TURNS, computes the aerodynamic flowfield near the helicopter blades and the Kirchhoff acoustics code computes the noise in the far field, using the TURNS solution as input. The overall parallel strategy adds MPI message passing calls to the existing serial codes to allow for communication between processors. As a result, the total code modifications required for parallel execution are relatively small. The biggest bottleneck in running the TURNS code in parallel comes from the LU-SGS algorithm that solves the implicit system of equations. We use a new hybrid domain decomposition implementation of LU-SGS to obtain good parallel performance on the SP-2. TURNS demonstrates excellent parallel speedups for quasi-steady and unsteady three-dimensional calculations of a helicopter blade in forward flight. The execution rate attained by the code on 114 processors is six times faster than the same cases run on one processor of the Cray C-90. The parallel Kirchhoff code also shows excellent parallel speedups and fast execution rates. As a performance demonstration, unsteady acoustic pressures are computed at 1886 far-field observer locations for a sample acoustics problem. The calculation requires over two hundred hours of CPU time on one C-90 processor but takes only a few hours on 80 processors of the SP2. The resultant far-field acoustic field is analyzed with state of-the-art audio and video rendering of the propagating acoustic signals.

Wissink, Andrew M.; Lyrintzis, Anastasios S.; Strawn, Roger C.; Oliker, Leonid; Biswas, Rupak

1996-01-01

315

Global design optimization for aerodynamics and rocket propulsion components  

NASA Astrophysics Data System (ADS)

Modern computational and experimental tools for aerodynamics and propulsion applications have matured to a stage where they can provide substantial insight into engineering processes involving fluid flows, and can be fruitfully utilized to help improve the design of practical devices. In particular, rapid and continuous development in aerospace engineering demands that new design concepts be regularly proposed to meet goals for increased performance, robustness and safety while concurrently decreasing cost. To date, the majority of the effort in design optimization of fluid dynamics has relied on gradient-based search algorithms. Global optimization methods can utilize the information collected from various sources and by different tools. These methods offer multi-criterion optimization, handle the existence of multiple design points and trade-offs via insight into the entire design space, can easily perform tasks in parallel, and are often effective in filtering the noise intrinsic to numerical and experimental data. However, a successful application of the global optimization method needs to address issues related to data requirements with an increase in the number of design variables, and methods for predicting the model performance. In this article, we review recent progress made in establishing suitable global optimization techniques employing neural-network- and polynomial-based response surface methodologies. Issues addressed include techniques for construction of the response surface, design of experiment techniques for supplying information in an economical manner, optimization procedures and multi-level techniques, and assessment of relative performance between polynomials and neural networks. Examples drawn from wing aerodynamics, turbulent diffuser flows, gas-gas injectors, and supersonic turbines are employed to help demonstrate the issues involved in an engineering design context. Both the usefulness of the existing knowledge to aid current design practices and the need for future research are identified.

Shyy, Wei; Papila, Nilay; Vaidyanathan, Rajkumar; Tucker, Kevin

2001-01-01

316

Comparison of the Coulter Multisizer and Aerodynamic Particle Sizer for obtaining the aerodynamic particle size of irregularly shaped dust  

E-print Network

When studying air quality it is often necessary to measure the aerodynamic size distribution of particles. True aerodynamic diameter must be measured using a gravitational settling method, which is impractical. Other methods exist that use other...

McClure, Joshua Wayne

2012-06-07

317

Reference values and improvement of aerodynamic drag in professional cyclists  

Microsoft Academic Search

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.

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

2008-01-01

318

APPLIED AERODYNAMICS Instructor: Prof. T.S. Leu ()  

E-print Network

1 APPLIED AERODYNAMICS Instructor: Prof. T.S. Leu () Department of Aeronautics and Astronautics Course goals : (1) (2) (3) (4)(4) (5) #12;2 Textbook Anderson, J D Jr., "Fundamentals of Aerodynamics" 5: Fundamental Principle Introduction to Aerodynamics Fundamental Principle and Equations of Fluid Mechanmics

Leu, Tzong-Shyng "Jeremy"

319

A Genetic Algorithm for Multiobjective Design Optimization in Aerodynamics and  

E-print Network

A Genetic Algorithm for Multiobjective Design Optimization in Aerodynamics and Electromagnetics R. The objective functions in the optimization problem measure the aerodynamic feasibil­ ity based on the drag been optimized with respect to only one discipline such as aerodynamics or electromagnetics. Although

Coello, Carlos A. Coello

320

Journal of Wind Engineering and Industrial Aerodynamics 90 (2002) 639642  

E-print Network

Journal of Wind Engineering and Industrial Aerodynamics 90 (2002) 639­642 Discussion Discussion; accepted 27 December 2001 Abstract The authors (J. Wind Eng. Ind. Aerodynam. 89 (2001) 341) presented a time domain framework for predicting the buffeting response of slender structures utilizing aerodynamic

Chen, Xinzhong

321

AERODYNAMIC OPTIMIZATION BASED ON THE EULER AND NAVIERSTOKES EQUATIONS USING  

E-print Network

AERODYNAMIC OPTIMIZATION BASED ON THE EULER AND NAVIER­STOKES EQUATIONS USING UNSTRUCTURED GRIDS Graduate Committee #12; Aerodynamic Optimization Based on the Euler and Navier­Stokes Equations Using Abstract The overall problem area addressed is that of efficient aerodynamic shape design through the use

Peraire, Jaime

322

System Identification of Post Stall Aerodynamics for UAV Perching  

E-print Network

System Identification of Post Stall Aerodynamics for UAV Perching Warren Hoburg and Russ Tedrake. The relevant transient aerodynamics at high angle of attack are not addressed today by control-accessible aerodynamic models. In this work, we present a set of physically-inspired basis functions which have enabled

Tedrake, Russ

323

Aerodynamics simulation of operating rooms N. El Gharbi*  

E-print Network

Aerodynamics simulation of operating rooms N. El Gharbi* A. Benzaoui*R. Bennacer** * Faculty. Keywords: Operating room, aerodynamics simulation, turbulent model, comfort, Airflow, Indoor air quality distribution scheme. To ensure these optimal conditions, a study of the aerodynamics flow in a conditioned

Paris-Sud XI, Université de

324

Fifty Years of Aerodynamics: Successes, Challenges, and Opportunities  

E-print Network

Fifty Years of Aerodynamics: Successes, Challenges, and Opportunities T.E. Nelson * D.W. Zingg, Canada. E-mail: tnelson@dehavilland.ca ** Senior Canada Research Chair in Computational Aerodynamics-mail: dwz@oddjob.utias.utoronto.ca Received 22 January 2004. PART I: AIRCRAFT DEVELOPMENT, AERODYNAMIC

Zingg, David W.

325

COPYRIGHT 2003 by ASME AERODYNAMICS OF TIP LEAKAGE FLOWS  

E-print Network

COPYRIGHT 2003 by ASME 1 AERODYNAMICS OF TIP LEAKAGE FLOWS NEAR PARTIAL SQUEALER RIMS IN AN AXIAL of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial of these "partial squealer tips" and their chordwise position are varied to find an optimal aerodynamic tip

Camci, Cengiz

326

Journal of Wind Engineering and Industrial Aerodynamics 91 (2003) 15111528  

E-print Network

Journal of Wind Engineering and Industrial Aerodynamics 91 (2003) 1511­1528 New frontiers in aerodynamic tailoring of long span bridges: an advanced analysis framework Xinzhong Chen*, Ahsan Kareem Nat analysis have been made utilizing realistic aerodynamic force modeling for bridges with bluff sections

Chen, Xinzhong

327

Body Force Model for the Aerodynamics of Inclined Perforated Surfaces  

E-print Network

Body Force Model for the Aerodynamics of Inclined Perforated Surfaces Juntao Xiong, Andrew Johnson.2514/1.J051699 This is a joint experimental and computational research effort on the aerodynamics aspects of the aerodynamics of wedge FFDs. The following sections present the experimental

Papamoschou, Dimitri

328

Journal of Wind Engineering and Industrial Aerodynamics 89 (2001) 13351350  

E-print Network

Journal of Wind Engineering and Industrial Aerodynamics 89 (2001) 1335­1350 Nonlinear response. The nonlinear unsteady aerodynamic forces are modeled based on static force coefficients, flutter derivatives incorporates frequency dependent parameters of unsteady aerodynamic forces by utilizing a rational function

Chen, Xinzhong

329

Robust Multi-Objective Optimization in Aerodynamics using MGDA  

E-print Network

Robust Multi-Objective Optimization in Aerodynamics using MGDA Daigo Maruyama N° 8428-00919215,version1-16Dec2013 #12;Robust Multi-Objective Optimization in Aerodynamics using MGDA Daigo: This study deals with robust design optimization strategies in aerodynamics

Boyer, Edmond

330

Aerodynamic Admittance Function of Tall Buildings Ahsan Kareemb  

E-print Network

Aerodynamic Admittance Function of Tall Buildings Yin Zhoua Ahsan Kareemb a Malouf Engineering Int, Notre Dame, USA ABSTRACT: The aerodynamic admittance function (AAF) has been widely invoked to relate in the high frequency range were noted. KEYWORDS: Aerodynamic admittance function; Wind effects; Tall

Kareem, Ahsan

331

NUMERICAL AND EXPERIMENTAL INVESTIGATIONS INTO THE AERODYNAMICS OF  

E-print Network

NUMERICAL AND EXPERIMENTAL INVESTIGATIONS INTO THE AERODYNAMICS OF DRAGONFLY FLIGHT. A Dissertation is in the public domain. #12;NUMERICAL AND EXPERIMENTAL INVESTIGATIONS INTO THE AERODYNAMICS OF DRAGONFLY FLIGHT direction very rapidly. Exactly how they use their wings to generate aerodynamic forces remains unknown

Wang, Z. Jane

332

Aerodynamic Optimization Under a Range of Operating Conditions  

E-print Network

Aerodynamic Optimization Under a Range of Operating Conditions David W. Zingg and Samy Elias University of Toronto, Toronto, Ontario M3H 5T6, Canada DOI: 10.2514/1.23658 In aerodynamic design, good developed that can ef ciently perform aerodynamic shape optimization [1­6]. The designer speci es

Zingg, David W.

333

Ris-R-1543(EN) Aerodynamic investigation of Winglets on  

E-print Network

Risø-R-1543(EN) Aerodynamic investigation of Winglets on Wind Turbine Blades using CFD Jeppe of the aerodynamics around a wind turbine blade with a winglet using Computational Fluid Dynamics, CFD. Five winglets Johansen and Niels N. Sørensen Title: Aerodynamic investigation of Winglets on Wind Turbine Blades using

334

14 CFR 23.371 - Gyroscopic and aerodynamic loads.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Gyroscopic and aerodynamic loads. 23.371 Section 23.371...Loads § 23.371 Gyroscopic and aerodynamic loads. (a) Each engine mount...designed for the gyroscopic, inertial, and aerodynamic loads that result, with the...

2010-01-01

335

14 CFR 23.371 - Gyroscopic and aerodynamic loads.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Gyroscopic and aerodynamic loads. 23.371 Section 23.371...Loads § 23.371 Gyroscopic and aerodynamic loads. (a) Each engine mount...designed for the gyroscopic, inertial, and aerodynamic loads that result, with the...

2011-01-01

336

14 CFR 23.371 - Gyroscopic and aerodynamic loads.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Gyroscopic and aerodynamic loads. 23.371 Section 23.371...Loads § 23.371 Gyroscopic and aerodynamic loads. (a) Each engine mount...designed for the gyroscopic, inertial, and aerodynamic loads that result, with the...

2012-01-01

337

14 CFR 23.371 - Gyroscopic and aerodynamic loads.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Gyroscopic and aerodynamic loads. 23.371 Section 23.371...Loads § 23.371 Gyroscopic and aerodynamic loads. (a) Each engine mount...designed for the gyroscopic, inertial, and aerodynamic loads that result, with the...

2013-01-01

338

Index for aerodynamic data from the Bumblebee program  

NASA Technical Reports Server (NTRS)

The Bumblebee program, was designed to provide a supersonic guided missile. The aerodynamics program included a fundamental research effort in supersonic aerodynamics as well as a design task in developing both test vehicles and prototypes of tactical missiles. An index of aerodynamic missile data developed in this program is presented.

Cronvich, L. L.; Barnes, G. A.

1978-01-01

339

International collaborative research in wind turbine rotor aerodynamics  

Microsoft Academic Search

Five organizations from four countries are collaborating to conduct detailed wind turbine aerodynamic test programs. Fullscale atmospheric testing will be conducted on turbines configured to measure aerodynamic forces on rotating airfoils. The purpose of these test programs is to come to a better understanding of the steady and unsteady aerodynamic behavior of wind turbine rotors, and provide information needed to

D. A. Simms; C. P. Butterfield

1993-01-01

340

Device for Reducing Vehicle Aerodynamic Resistance.  

National Technical Information Service (NTIS)

A device for reducing vehicle aerodynamic resistance for vehicles having a generally rectangular flat front face comprising a plurality of load bearing struts of a predetermined size attached to the flat front face adjacent the sides and top thereof, a pa...

S. C. Graham

2004-01-01

341

Recent Experiments at the Gottingen Aerodynamic Institute  

NASA Technical Reports Server (NTRS)

This report presents the results of various experiments carried out at the Gottingen Aerodynamic Institute. These include: experiments with Joukowski wing profiles; experiments on an airplane model with a built-in motor and functioning propeller; and the rotating cylinder (Magnus Effect).

Ackeret, J

1925-01-01

342

User's guide to program FLEXSTAB. [aerodynamics  

NASA Technical Reports Server (NTRS)

A manual is presented for correctly submitting program runs in aerodynamics on the UNIVAC 1108 computer system. All major program modules are included. Control cards are documented for the user's convenience, and card parameters are included in order to provide some idea as to reasonable time estimates for the program modules.

Cavin, R. K., III; Colunga, D.

1975-01-01

343

Aerodynamic characteristics of an oscillating airfoil  

Microsoft Academic Search

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

R. H. Wickens

1986-01-01

344

Nozzle Aerodynamic Stability During a Throat Shift  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted on the internal aerodynamic stability of a family of two-dimensional (2-D) High Speed Civil Transport (HSCT) nozzle concepts. These nozzles function during takeoff as mixer-ejectors to meet acoustic requirements, and then convert to conventional high-performance convergent-divergent (CD) nozzles at cruise. The transition between takeoff mode and cruise mode results in the aerodynamic throat and the minimum cross-sectional area that controls the engine backpressure shifting location within the nozzle. The stability and steadiness of the nozzle aerodynamics during this so called throat shift process can directly affect the engine aerodynamic stability, and the mechanical design of the nozzle. The objective of the study was to determine if pressure spikes or other perturbations occurred during the throat shift process and, if so, identify the caused mechanisms for the perturbations. The two nozzle concepts modeled in the test program were the fixed chute (FC) and downstream mixer (DSM). These 2-D nozzles differ principally in that the FC has a large over-area between the forward throat and aft throat locations, while the DSM has an over-area of only about 10 percent. The conclusions were that engine mass flow and backpressure can be held constant simultaneously during nozzle throat shifts on this class of nozzles, and mode shifts can be accomplished at a constant mass flow and engine backpressure without upstream pressure perturbations.

Kawecki, Edwin J.; Ribeiro, Gregg L.

2005-01-01

345

Aerodynamic Shape Optimization Using the Adjoint Method  

Microsoft Academic Search

These Lecture Notes review the formulation and application of optimization techniques based on control theory for aerodynamic shape design in both inviscid and viscous compressible o w. The theory is applied to a system dened by the partial dieren tial equations of the o w, with the boundary shape acting as the control. The Frechet derivative of the cost function

Antony Jameson

346

Identification of aerodynamic models for maneuvering aircraft  

NASA Technical Reports Server (NTRS)

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

Chin, Suei; Lan, C. Edward

1990-01-01

347

Efficient Global Aerodynamic Modeling from Flight Data  

NASA Technical Reports Server (NTRS)

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

Morelli, Eugene A.

2012-01-01

348

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

349

Aerodynamic analysis of an isolated vehicle wheel  

NASA Astrophysics Data System (ADS)

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

Le?niewicz, P.; Kulak, M.; Karczewski, M.

2014-08-01

350

A Generic Nonlinear Aerodynamic Model for Aircraft  

NASA Technical Reports Server (NTRS)

A generic model of the aerodynamic coefficients was developed using wind tunnel databases for eight different aircraft and multivariate orthogonal functions. For each database and each coefficient, models were determined using polynomials expanded about the state and control variables, and an othgonalization procedure. A predicted squared-error criterion was used to automatically select the model terms. Modeling terms picked in at least half of the analyses, which totalled 45 terms, were retained to form the generic nonlinear aerodynamic (GNA) model. Least squares was then used to estimate the model parameters and associated uncertainty that best fit the GNA model to each database. Nonlinear flight simulations were used to demonstrate that the GNA model produces accurate trim solutions, local behavior (modal frequencies and damping ratios), and global dynamic behavior (91% accurate state histories and 80% accurate aerodynamic coefficient histories) under large-amplitude excitation. This compact aerodynamics model can be used to decrease on-board memory storage requirements, quickly change conceptual aircraft models, provide smooth analytical functions for control and optimization applications, and facilitate real-time parametric system identification.

Grauer, Jared A.; Morelli, Eugene A.

2014-01-01

351

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

352

Aerodynamic beam generator for large particles  

DOEpatents

A new type of aerodynamic particle beam generator is disclosed. This generator produces a tightly focused beam of large material particles at velocities ranging from a few feet per second to supersonic speeds, depending on the exact configuration and operating conditions. Such generators are of particular interest for use in additive fabrication techniques.

Brockmann, John E. (Albuquerque, NM); Torczynski, John R. (Albuquerque, NM); Dykhuizen, Ronald C. (Albuquerque, NM); Neiser, Richard A. (Albuquerque, NM); Smith, Mark F. (Albuquerque, NM)

2002-01-01

353

Nonlinear aerodynamic modeling using multivariate orthogonal functions  

NASA Technical Reports Server (NTRS)

The problem to be addressed in this work is that of modeling nondimensional force and moment aerodynamic coefficients over the entire subsonic envelope. The particular application discussed here is the Z force coefficient for the F-18 High Angle of Attack Research Vehicle (HARV).

Morelli, Eugene A.

1993-01-01

354

Aerodynamic Properties of Spherical Balloon Wind Sensors  

Microsoft Academic Search

A first-order theory of the fluctuating lift and drag coefficients associated with the aerodynamically induced motions of rising and falling spherical wind sensors is developed. The equations of motion of a sensor are perturbed about an equilibrium state in which the buoyancy force balances the mean vertical drag force. It is shown that, to within first order in perturbation quantities,

George H. Fichtl; R. E. Demandel; S. J. Krivo

1972-01-01

355

Plasma Enhanced Aerodynamics of Wind Turbine Blades  

Microsoft Academic Search

A series of computer simulations was conducted to determine the optimal method for reducing the chord length of large wind turbine blades while incorporating advanced flow control to offset the resulting loss in aerodynamic performance. The dominant building trend in the wind energy industry of turbines with progressively larger diameters provided the inspiration for this study. By reducing the chord

John Cooney; Thomas Corke; Robert Nelson

2009-01-01

356

AERODYNAMIC CLASSIFICATION OF FIBERS WITH AEROSOL CENTRIFUGES  

EPA Science Inventory

The constituent particles of many ambient and workplace aerosols of health effects concerns are of fibrous and aggregate geometric shapes. he sites of deposition in the human respiratory system are primarily related to the mass median aerodynamic diameters of inhaled particle siz...

357

Prediction of XV-15 tilt rotor discrete frequency aeroacoustic noise with WOPWOP  

NASA Technical Reports Server (NTRS)

The results, methodology, and conclusions of noise prediction calculations carried out to study several possible discrete frequency harmonic noise mechanisms of the XV-15 Tilt Rotor Aircraft in hover and helicopter mode forward flight are presented. The mechanisms studied were thickness and loading noise. In particular, the loading noise caused by flow separation and the fountain/ground plane effect were predicted with calculations made using WOPWOP, a noise prediction program developed by NASA Langley. The methodology was to model the geometry and aerodynamics of the XV-15 rotor blades in hover and steady level flight and then create corresponding FORTRAN subroutines which were used an input for WOPWOP. The models are described and the simplifying assumptions made in creating them are evaluated, and the results of the computations are presented. The computations lead to the following conclusions: The fountain/ground plane effect is an important source of aerodynamic noise for the XV-15 in hover. Unsteady flow separation from the airfoil passing through the fountain at high angles of attack significantly affects the predicted sound spectra and may be an important noise mechanism for the XV-15 in hover mode. The various models developed did not predict the sound spectra in helicopter forward flight. The experimental spectra indicate the presence of blade vortex interactions which were not modeled in these calculations. A need for further study and development of more accurate aerodynamic models, including unsteady stall in hover and blade vortex interactions in forward flight.

Coffen, Charles D.; George, Albert R.

1990-01-01

358

A study of helicopter main rotor noise in hover  

Microsoft Academic Search

Some fundamental aspects of rotor noise generation and radiation are presented. Data on which the study is based were obtained during a hover test at the NASA Ames Outdoor Aerodynamic Research Facility of a one-sixth-scale, four-bladed, helicopter rotor. The test site provided an open environment ideal for acquiring good acoustic data. Information is presented on the delineation between the acoustic

C. Kitaplioglu; C. Kinney

1986-01-01

359

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

360

Acoustic and aerodynamic performance of a 1.83-meter (6-ft) diameter 1.25-pressure-ratio fan (QF-8)  

NASA Technical Reports Server (NTRS)

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, including absence of inlet guide vanes, low rotor blade tip speed, low aerodynamic blade loading, and long axial spacing between the rotor and stator blade rows. The fan was operated with five exhaust nozzle areas. The stage noise levels generally increased with a decrease in nozzle area. Separation of the acoustic one-third octave results into broadband and pure-tone components showed the broadband noise to be greater than the corresponding pure-tone components. The sideline perceived noise was highest in the rear quadrants. The acoustic results of QF-8 were compared with those of two similar STOL application fans in the test series. The QF-8 had somewhat higher relative noise levels than those of the other two fans. The aerodynamic results of QF-8 and the other two fans were compared with corresponding results from 50.8-cm (20-in.) diam scale models of these fans and design values. Although the results for the full-scale and scale models of the other two fans were in reasonable agreement for each design, the full-scale fan QF-8 results showed poor performance compared with corresponding model results and design expectations. Facility effects of the full-scale fan QF-8 installation were considered in analyzing this discrepancy.

Woodward, R. P.; Lucas, J. G.

1976-01-01

361

Acoustic tests of duct-burning turbofan jet noise simulation  

NASA Technical Reports Server (NTRS)

The results of a static acoustic and aerodynamic performance, model-scale test program on coannular unsuppressed and multielement fan suppressed nozzle configurations are summarized. The results of the static acoustic tests show a very beneficial interaction effect. When the measured noise levels were compared with the predicted noise levels of two independent but equivalent conical nozzle flow streams, noise reductions for the unsuppressed coannular nozzles were of the order of 10 PNdB; high levels of suppression (8 PNdB) were still maintained even when only a small amount of core stream flow was used. The multielement fan suppressed coannular nozzle tests showed 15 PNdB noise reductions and up to 18 PNdB noise reductions when a treated ejector was added. The static aerodynamic performance tests showed that the unsuppressed coannular plug nozzles obtained gross thrust coefficients of 0.972, with 1.2 to 1.7 percent lower levels for the multielement fan-suppressed coannular flow nozzles. For the first time anywhere, laser velocimeter velocity profile measurements were made on these types of nozzle configurations and with supersonic heated flow conditions. Measurements showed that a very rapid decay in the mean velocity occurs for the nozzle tested.

Knott, P. R.; Stringas, E. J.; Brausch, J. F.; Staid, P. S.; Heck, P. H.; Latham, D.

1978-01-01

362

Scaling of airfoil self-noise using measured flow parameters  

NASA Astrophysics Data System (ADS)

Data from an airfoil broadband self-noise study are reported. Attention here is restricted to two-dimensional models at zero angle of attack to the flow. The models include seven NACA 0012 airfoil sections and five flat plate sections with chordlengths ranging from 2.54 to 60.96 cm. Testing parameters include flow velocity to 71.3 m/s and boundary-layer turbulence through natural transition and by tripping. Detailed aerodynamic measurements are conducted in the near-wake of the sharp trailing edges. The noise spectra of the self-noise sources are determined by the use of a cross-spectral technique. The acoustic data are normalized using the measured aerodynamic parameters in order to evaluate a commonly used scaling law. An examination of the Reynolds number dependence of the normalized overall levels has revealed a useful scaling result. This result appears to quantify the transition between turbulent boundary-layer trailing-edge noise and laminar boundary-layer vortex shedding noise.

Brooks, T. F.; Marcolini, M. A.

1985-02-01

363

Scaling of airfoil self-noise using measured flow parameters  

NASA Technical Reports Server (NTRS)

Data from an airfoil broadband self-noise study are reported. Attention here is restricted to two-dimensional models at zero angle of attack to the flow. The models include seven NACA 0012 airfoil sections and five flat plate sections with chordlengths ranging from 2.54 to 60.96 cm. Testing parameters include flow velocity to 71.3 m/s and boundary-layer turbulence through natural transition and by tripping. Detailed aerodynamic measurements are conducted in the near-wake of the sharp trailing edges. The noise spectra of the self-noise sources are determined by the use of a cross-spectral technique. The acoustic data are normalized using the measured aerodynamic parameters in order to evaluate a commonly used scaling law. An examination of the Reynolds number dependence of the normalized overall levels has revealed a useful scaling result. This result appears to quantify the transition between turbulent boundary-layer trailing-edge noise and laminar boundary-layer vortex shedding noise.

Brooks, T. F.; Marcolini, M. A.

1985-01-01

364

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

365

Wind turbine trailing edge aerodynamic brakes  

SciTech Connect

Five trailing-edge devices were investigated to determine their potential as wind-turbine aerodynamic brakes, and for power modulation and load alleviation. Several promising configurations were identified. A new device, called the spoiler-flap, appears to be the best alternative. It is a simple device that is effective at all angles of attack. It is not structurally intrusive, and it has the potential for small actuating loads. It is shown that simultaneous achievement of a low lift/drag ratio and high drag is the determinant of device effectiveness, and that these attributes must persist up to an angle of attack of 45{degree}. It is also argued that aerodynamic brakes must be designed for a wind speed of at least 45 m/s (100 mph).

Migliore, P G [National Renewable Energy Lab., Golden, CO (United States); Miller, L S [Wichita State Univ., KS (United States). Dept. of Aerospace Engineering; Quandt, G A

1995-04-01

366

Aerodynamic shape optimization of arbitrary hypersonic vehicles  

NASA Technical Reports Server (NTRS)

A new method was developed to optimize, in terms of aerodynamic wave drag minimization, arbitrary (nonaxisymmetric) hypersonic vehicles in modified Newtonian flow, while maintaining the initial volume and length of the vehicle. This new method uses either a surface fitted Fourier series to represent the vehicle's geometry or an independent point motion algorithm. In either case, the coefficients of the Fourier series or the spatial locations of the points defining each cross section were varied and a numerical optimization algorithm based on a quasi-Newton gradient search concept was used to determine the new optimal configuration. Results indicate a significant decrease in aerodynamic wave drag for simple and complex geometries at relatively low CPU costs. In the case of a cone, the results agreed well with known analytical optimum ogive shapes. The procedure is capable of accepting more complex flow field analysis codes.

Dulikravich, George S.; Sheffer, Scott G.

1991-01-01

367

Flight Test Maneuvers for Efficient Aerodynamic Modeling  

NASA Technical Reports Server (NTRS)

Novel flight test maneuvers for efficient aerodynamic modeling were developed and demonstrated in flight. Orthogonal optimized multi-sine inputs were applied to aircraft control surfaces to excite aircraft dynamic response in all six degrees of freedom simultaneously while keeping the aircraft close to chosen reference flight conditions. Each maneuver was designed for a specific modeling task that cannot be adequately or efficiently accomplished using conventional flight test maneuvers. All of the new maneuvers were first described and explained, then demonstrated on a subscale jet transport aircraft in flight. Real-time and post-flight modeling results obtained using equation-error parameter estimation in the frequency domain were used to show the effectiveness and efficiency of the new maneuvers, as well as the quality of the aerodynamic models that can be identified from the resultant flight data.

Morelli, Eugene A.

2011-01-01

368

Transonic and supersonic ground effect aerodynamics  

NASA Astrophysics Data System (ADS)

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

Doig, G.

2014-08-01

369

Noise reduction for centrifugal fan with non-isometric forward-swept blade impeller  

Microsoft Academic Search

To reduce the noise of the T9-19No.4A centrifugal fan, whose impeller has equidistant forward-swept blades, two new impellers\\u000a with different blade spacing were designed and an experimental study was conducted. Both the fan’s aerodynamic performance\\u000a and noise were measured when the two redesigned impellers were compared with the original ones. The test results are discussed\\u000a in detail and the effect

Jianfeng Ma; Datong Qi; Yijun Mao

2008-01-01

370

Aerodynamic and Acoustic Performance of Two Choked-Flow Inlets Under Static Conditions  

NASA Technical Reports Server (NTRS)

Tests were conducted to determine the aerodynamic and acoustic performance of two choking flow inlets under static conditions. One inlet choked the flow in the cowl throat by an axial translation of the inlet centerbody. The other inlet employed a translating grid of airfoils to choke the flow. Both inlets were sized to fit a 13.97 cm diameter fan with a design weight flow of 2.49 kg/sec. The inlets were operated in both the choked and unchoked modes over a range of weight flows. Measurements were made of inlet pressure recovery, flow distortion, surface static pressure distribution, and fan noise suppression. Choking of the translating centerbody inlet reduced blade passing frequency noise by 29 db while yielding a total pressure recovery of 0.985. Noise reductions were also measured at 1/3-octave band center frequencies of 2500, 5000, and 20,000 cycles. The translating grid inlet gave a total pressure recovery of 0.968 when operating close to the choking weight flow. However, an intermittent high intensity noise source was encountered with this inlet that precluded an accurate measurement of inlet noise suppression.

Miller, B. A.; Abbott, J. M.

1972-01-01

371

Flight-Test Fixture For Aerodynamic Research  

NASA Technical Reports Server (NTRS)

Second-generation flight-test fixture (FTF-II) developed to be used as generic test bed for research in aerodynamics and fluid mechanics. Highly instrumented finlike structure mounted on lower fuselage surface of F-15B airplane. Modular configuration makes possible to modify FTF-II to satisfy variety of flight-test requirements. Fixture used at airspeeds up to mach 2.0.

Richwine, David M.; Del Frate, John H.

1995-01-01

372

The aerodynamics of hovering flight in Drosophila.  

PubMed

Using 3D infrared high-speed video, we captured the continuous wing and body kinematics of free-flying fruit flies, Drosophila melanogaster, during hovering and slow forward flight. We then 'replayed' the wing kinematics on a dynamically scaled robotic model to measure the aerodynamic forces produced by the wings. Hovering animals generate a U-shaped wing trajectory, in which large drag forces during a downward plunge at the start of each stroke create peak vertical forces. Quasi-steady mechanisms could account for nearly all of the mean measured force required to hover, although temporal discrepancies between instantaneous measured forces and model predictions indicate that unsteady mechanisms also play a significant role. We analyzed the requirements for hovering from an analysis of the time history of forces and moments in all six degrees of freedom. The wing kinematics necessary to generate sufficient lift are highly constrained by the requirement to balance thrust and pitch torque over the stroke cycle. We also compare the wing motion and aerodynamic forces of free and tethered flies. Tethering causes a strong distortion of the stroke pattern that results in a reduction of translational forces and a prominent nose-down pitch moment. The stereotyped distortion under tethered conditions is most likely due to a disruption of sensory feedback. Finally, we calculated flight power based directly on the measurements of wing motion and aerodynamic forces, which yielded a higher estimate of muscle power during free hovering flight than prior estimates based on time-averaged parameters. This discrepancy is mostly due to a two- to threefold underestimate of the mean profile drag coefficient in prior studies. We also compared our values with the predictions of the same time-averaged models using more accurate kinematic and aerodynamic input parameters based on our high-speed videography measurements. In this case, the time-averaged models tended to overestimate flight costs. PMID:15939772

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

2005-06-01

373

Aerodynamic design of propfan powered transports  

NASA Technical Reports Server (NTRS)

A case study is presented of the design of efficient propfan transport aircraft configurations, employing standard subsonic and transonic computed codes that have been modified to account for slipstream effects. After numerically simulating the aerodynamics of the interaction of the wing/nacelle configuration with the swirling slipstream, interference effects are assessed and design procedures are provided which may reduce adverse interference phenomena. These procedures are demonstrated for the case of the design of a Mach 0.8-cruise turboprop aircraft.

Aljabri, A. S.

1983-01-01

374

Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines  

NASA Astrophysics Data System (ADS)

This textbook is a collection of technical papers that were presented at the 10th International Symposium on Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines held September 8-11, 2003 at Duke University in Durham, North Carolina. The papers represent the latest in state of the art research in the areas of aeroacoustics, aerothermodynamics, computational methods, experimental testing related to flow instabilities, flutter, forced response, multistage, and rotor-stator effects for turbomachinery.

Hall, Kenneth C.; Kielb, Robert E.; Thomas, Jeffrey P.

375

Smart morphable surfaces for aerodynamic drag control.  

PubMed

Smart Morphable Surfaces enable switchable and tunable aerodynamic drag reduction of bluff bodies. Their topography, resembling the morphology of golf balls, can be custom-generated through a wrinkling instability on a curved surface. Pneumatic actuation of these patterns results in the control of the drag coefficient of spherical samples by up to a factor of two, over a range of flow conditions. PMID:24956072

Terwagne, Denis; Brojan, Miha; Reis, Pedro M

2014-10-01

376

Aerodynamics of High-Speed Trains  

Microsoft Academic Search

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

Joseph A. Schetz

2001-01-01

377

Hydrodynamic and aerodynamic breakup of liquid sheets  

NASA Technical Reports Server (NTRS)

The effect of hydrodynamic, aerodynamic and liquid surface forces on the mean drop diameter of water sprays that are produced by the breakup of nonswirling and swirling water sheets in quiescent air and in airflows similar to those encountered in gas turbine combustors is investigated. The mean drop diameter is used to characterize fuel sprays and it is a very important factor in determining the performance and exhaust emissions of gas turbine combustors.

Ingebo, R.

1982-01-01

378

Aerodynamic design lowers truck fuel consumption  

NASA Technical Reports Server (NTRS)

Energy-saving concepts in truck design are emerging from developing new shapes with improved aerodynamic flow properties that can reduce air-drag coefficient of conventional tractor-trailers without requiring severe design changes or compromising load-carrying capability. Improvements are expected to decrease somewhat with increased wind velocities and would be affected by factors such as terrain, driving techniques, and mechanical condition.

Steers, L.

1978-01-01

379

Aerodynamic loading on a cylinder behind an airfoil  

NASA Astrophysics Data System (ADS)

The interaction between the wake of a rotor blade and a downstream cylinder holds the key to the understanding and control of electronic cooling fan noise. In this paper, the aerodynamic characteristics of a circular cylinder are experimentally studied in the presence of an upstream NACA 4412 airfoil for the cylinder-diameter-based Reynolds numbers of Red=2,100 20,000, and the airfoil chord-length-based Reynolds numbers of Rec=14,700 140,000. Lift and drag fluctuations on the cylinder, and the longitudinal velocity fluctuations of the flow behind the cylinder were measured simultaneously using a load cell and two hot wires, respectively. Data analysis shows that unsteady forces on the cylinder increase significantly in the presence of the airfoil wake. The dependence of the forces on two parameters is investigated, that is, the lateral distance (T) between the airfoil and the cylinder, and the Reynolds number. The forces decline quickly as T increases. For Rec<60,000, the vortices shed from the upstream airfoil make a major contribution to the unsteady forces on the cylinder compared to the vortex shedding from the cylinder itself. For Rec>60,000, no vortices are generated from the airfoil, and the fluctuating forces on the cylinder are caused by its own vortex shedding.

Zhang, H. J.; Huang, L.; Zhou, Y.

2005-05-01

380

Noise group overview Avia0on Noise  

E-print Network

) � Jet noise � Wavepacket models � Data-driven approaches to understanding subsonic, turbulent jet-noise (Jordan, Colonius, Bres, Zhang, Towne, Lele) � Double-peaked wavepackets in supersonic jet noise (Nichols) � Control � LaVce-Boltzmann aeroacous8c

Wang, Wei

381

Noise sustained propagation: Local versus global noise  

Microsoft Academic Search

We expand on prior results on noise supported signal propagation in arrays of coupled bistable elements. We present and compare experimental and numerical results for kink propagation under the influence of local and global fluctuations. As demonstrated previously for local noise, an optimum range of global noise power exists for which the medium acts as a reliable transmission ``channel.'' We

M. Löcher; N. Chatterjee; F. Marchesoni; W. L. Ditto; E. R. Hunt

2000-01-01

382

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

383

Aerodynamics of a rigid curved kite wing  

E-print Network

A preliminary numerical study on the aerodynamics of a kite wing for high altitude wind power generators is proposed. Tethered kites are a key element of an innovative wind energy technology, which aims to capture energy from the wind at higher altitudes than conventional wind towers. We present the results obtained from three-dimensional finite volume numerical simulations of the steady air flow past a three-dimensional curved rectangular kite wing (aspect ratio equal to 3.2, Reynolds number equal to 3x10^6). Two angles of incidence -- a standard incidence for the flight of a tethered airfoil (6{\\deg}) and an incidence close to the stall (18{\\deg}) -- were considered. The simulations were performed by solving the Reynolds Averaged Navier-Stokes flow model using the industrial STAR-CCM+ code. The overall aerodynamic characteristics of the kite wing were determined and compared to the aerodynamic characteristics of the flat rectangular non twisted wing with an identical aspect ratio and section (Clark Y profil...

Maneia, Gianmauro; Tordella, Daniela; Iovieno, Michele

2013-01-01

384

Improving the aerodynamics of top fuel dragsters  

SciTech Connect

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

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

1998-07-01

385

Aerodynamic Design Opportunities for Future Supersonic Aircraft  

NASA Technical Reports Server (NTRS)

A discussion of a diverse set of aerodynamic opportunities to improve the aerodynamic performance of future supersonic aircraft has been presented and discussed. These ideas are offered to the community in a hope that future supersonic vehicle development activities will not be hindered by past efforts. A number of nonlinear flow based drag reduction technologies are presented and discussed. The subject technologies are related to the areas of interference flows, vehicle concepts, vortex flows, wing design, advanced control effectors, and planform design. The authors also discussed the importance of improving the aerodynamic design environment to allow creativity and knowledge greater influence. A review of all of the data presented show that pressure drag reductions on the order of 50 to 60 counts are achievable, compared to a conventional supersonic cruise vehicle, with the application of several of the discussed technologies. These drag reductions would correlate to a 30 to 40% increase in cruise L/D (lift-to-drag ratio) for a commercial supersonic transport.

Wood, Richard M.; Bauer, Steven X. S.; Flamm, Jeffrey D.

2002-01-01

386

Asymmetric Uncertainty Expression for High Gradient Aerodynamics  

NASA Technical Reports Server (NTRS)

When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

Pinier, Jeremy T

2012-01-01

387

Integrated aerodynamic-structural-control wing design  

NASA Technical Reports Server (NTRS)

The aerodynamic-structural-control design of a forward-swept composite wing for a high subsonic transport aircraft is considered. The structural analysis is based on a finite-element method. The aerodynamic calculations are based on a vortex-lattice method, and the control calculations are based on an output feedback control. The wing is designed for minimum weight subject to structural, performance/aerodynamic and control constraints. Efficient methods are used to calculate the control-deflection and control-effectiveness sensitivities which appear as second-order derivatives in the control constraint equations. To suppress the aeroelastic divergence of the forward-swept wing, and to reduce the gross weight of the design aircraft, two separate cases are studied: (1) combined application of aeroelastic tailoring and active controls; and (2) aeroelastic tailoring alone. The results of this study indicated that, for this particular example, aeroelastic tailoring is sufficient for suppressing the aeroelastic divergence, and the use of active controls was not necessary.

Rais-Rohani, M.; Haftka, R. T.; Grossman, B.; Unger, E. R.

1992-01-01

388

NOISE SOURCE IDENTIFICATION IN A PROPFAN MODEL BY MEANS OF ACOUSTICAL NEAR FIELD MEASUREMENTS  

Microsoft Academic Search

For the exploration of the dominant aerodynamic noise sources, the pressure fluctuations in the exit plane (near field) of the propfan model CRISP (Counter Rotating Integrated Shrouded Propfan) were measured with conventional 1\\/4 inch microphones. The pressure field of the tone components was resolved into a distribution of duct modes. Knowledge of the dominant modes allows conclusions about the dominant

F. Holste; W. Neise

1997-01-01

389

Direct computation of the noise radiated by a subsonic cavity flow and application of integral methods  

Microsoft Academic Search

The goal of this paper is to investigate the acoustic field generated by the flow over a cavity using two different and complementary numerical methods. First, a Direct Numerical Simulation of the 2-D compressible Navier–Stokes equations is performed to obtain directly the radiated noise. The results of the acoustic and aerodynamic fields are compared to the experimental data in the

X. Gloerfelt; C. Bailly; D. Juvé

2003-01-01

390

Performance and Noise Trade-Offs on a Civil Airliner with Over-the-Wing Engines  

E-print Network

at this time) is the Blended-Wing-Body(BWB) concept,3 which greatly improves aerodynamic efficiency as wellPerformance and Noise Trade-Offs on a Civil Airliner with Over-the-Wing Engines Stephen Powell to achieve further significant reductions. One option is to install the engines over the wings so

Sóbester, András

391

Flow patterns and noise of a choked gas jet expanding into a duct  

Microsoft Academic Search

Axisymmetric, choked air outflow into a duct with an abrupt enlargement of its cross-section was investigated in order to establish the relations between the flow pattern and the aerodynamic noise generated. Four main kinds of flow structure, possessing different acoustic properties, were found in the cases studied of the outflow from convergent circular and annular nozzles. These patterns correspond to

K. J. Witczak

1976-01-01

392

Vibration and noise radiation from a panel excited by a turbulent flow  

E-print Network

jet anechoic wind tunnel at the Institute of Sound and Vibration Research, where a very low noise flow attempts have been made to develop theoretical models of the aerodynamic excitation using CFD (Compu and Vibration Research (ISVR) open jet anechoic wind tunnel was used because it provides a high speed flow

Paris-Sud XI, Université de

393

Noise and blast  

NASA Technical Reports Server (NTRS)

Noise and blast environments are described, providing a definition of units and techniques of noise measurement and giving representative booster-launch and spacecraft noise data. The effects of noise on hearing sensitivity and performance are reviewed, and community response to noise exposure is discussed. Physiological, or nonauditory, effects of noise exposure are also treated, as are design criteria and methods for minimizing the noise effects of hearing sensitivity and communications. The low level sound detection and speech reception are included, along with subjective and behavioral responses to noise.

Hodge, D. C.; Garinther, G. R.

1973-01-01

394

A Survey of Challenges in Aerodynamic Exhaust Nozzle Technology for Aerospace Propulsion Applications  

NASA Technical Reports Server (NTRS)

The current paper discusses aerodynamic exhaust nozzle technology challenges for aircraft and space propulsion systems. Technology advances in computational and experimental methods have led to more accurate design and analysis tools, but many major challenges continue to exist in nozzle performance, jet noise and weight reduction. New generations of aircraft and space vehicle concepts dictate that exhaust nozzles have optimum performance, low weight and acceptable noise signatures. Numerous innovative nozzle concepts have been proposed for advanced subsonic, supersonic and hypersonic vehicle configurations such as ejector, mixer-ejector, plug, single expansion ramp, altitude compensating, lobed and chevron nozzles. This paper will discuss the technology barriers that exist for exhaust nozzles as well as current research efforts in place to address the barriers.

Shyne, Rickey J.

2002-01-01

395

Effect of blade wrap angle on efficiency and noise of small radial fan impellers—A computational and experimental study  

NASA Astrophysics Data System (ADS)

Radial impellers have several technical applications. Regarding their aerodynamic performance, they are well optimized nowadays, but this is in general not true regarding acoustics. This work was therefore concerned with analyzing the flow structures inside isolated radial impellers together with the far-field sound radiated from them in order to optimize the aerodynamic and acoustic performance. Both numerical and experimental techniques were applied in order to study the effect of varying wrap angle and otherwise identical geometric configuration on aerodynamics and acoustics of the radial impellers. The results give a detailed insight into the processes leading to sound generation in radial impellers. Measurements were performed using laser Doppler anemometry for the flow field and microphone measurements to analyze the radiated noise. In addition, unsteady aerodynamic simulations were carried out to calculate the compressible flow field. An acoustic analogy was employed to compute far-field noise. Finally, the phenomena responsible for tonal noise and the role of the wrap angle could be identified. Using this knowledge, design guidelines are given to optimize the impeller with respect to the radiated noise. This work shows that improved aerodynamic efficiency for isolated impellers does not automatically lead to a smaller flow-induced sound radiation.

Scheit, C.; Karic, B.; Becker, S.

2012-02-01

396

Exploratory study to induce fan noise in the test section of the NASA Langley full-scale wind tunnel  

NASA Technical Reports Server (NTRS)

Measures to reduce the intensity of fan noise in the NASA Langley 30 ft x 60 ft subsonic wind tunnel were sought. Measurements were first performed to document existing aerodynamic and acoustic conditions. The purpose of these experiments was to (1) obtain the transfer function between the sound power output of the fan and the sound pressure on the test platform, (2) evaluate the sound attenuation around the tunnel circuit, (3) measure simultaneously the flow profile and the turbulence spectrum of the inflow to the fan and the noise on the test platform, and (4) perform flow observations and identify secondary noise sources. Subsequently, these data were used to predict (1) the relative contribution of the major aerodynamic parameters to total fan noise and (2) the effect of placing a dissipative silencer in the collector duct upstream of the fan. Promising noise control measures were identified and recommendations were made on how to evaluate them.

Ver, I. L.; Hayden, R. E.; Myles, M. M.; Murray, B. E.

1975-01-01

397

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

398

Aerodynamic characteristics of airplanes at high angles of attack  

NASA Technical Reports Server (NTRS)

An introduction to, and a broad overiew of, the aerodynamic characteristics of airplanes at high angles of attack are provided. Items include: (1) some important fundamental phenomena which determine the aerodynamic characteristics of airplanes at high angles of attack; (2) static and dynamic aerodynamic characteristics near the stall; (3) aerodynamics of the spin; (4) test techniques used in stall/spin studies; (5) applications of aerodynamic data to problems in flight dynamics in the stall/spin area; and (6) the outlook for future research in the area. Although stalling and spinning are flight dynamic problems of importance to all aircraft, including general aviation aircraft, commercial transports, and military airplanes, emphasis is placed on military configurations and the principle aerodynamic factors which influence the stability and control of such vehicles at high angles of attack.

Chambers, J. R.; Grafton, S. B.

1977-01-01

399

A large-scale computer facility for computational aerodynamics  

SciTech Connect

The combination of computer system technology and numerical modeling have advanced to the point that computational aerodynamics has emerged as an essential element in aerospace vehicle design methodology. To provide for further advances in modeling of aerodynamic flow fields, NASA has initiated at the Ames Research Center the Numerical Aerodynamic Simulation (NAS) Program. The objective of the Program is to develop a leading-edge, large-scale computer facility, and make it available to NASA, DoD, other Government agencies, industry and universities as a necessary element in ensuring continuing leadership in computational aerodynamics and related disciplines. The Program will establish an initial operational capability in 1986 and systematically enhance that capability by incorporating evolving improvements in state-of-the-art computer system technologies as required to maintain a leadership role. This paper briefly reviews the present and future requirements for computational aerodynamics and discusses the Numerical Aerodynamic Simulation Program objectives, computational goals, and implementation plans.

Bailey, F.R.; Balhaus, W.F.

1985-02-01

400

Jet noise prediction using different turbulent scales  

NASA Astrophysics Data System (ADS)

The turbulent energy dissipation rate time-scale and length-scale has been routinely used for the prediction of noise from turbulent flows, particularly jet streams. However, this is not the only possible choice. In general, scales evolving in a turbulent medium are threefold. First, those associated with the mean flow; second, those attributed to the turbulence and the mean flow interactions; and third, scales related to the turbulence-turbulence interactions. In this paper, special attention will be paid to further study of the underlying physics of aerodynamic noise by examining various time-scales. To do so, three time scales, namely, dissipation, production, and strain rate time scales, are defined and used in the source modelling to emphasis the effect of the turbulence structures at different jet regions on the jet noise production mechanism. The required mean value and turbulence parameters are obtained using a modified k - ? turbulence model, and Lighthill’s Acoustic Analogy is used for the prediction of the emanated noise.

Self, Rod H.; Azarpeyvand, Mahdi

2009-05-01

401

Estimation of Unsteady Aerodynamic Models from Flight Test Data  

NASA Technical Reports Server (NTRS)

This report summarizes the activities in aerodynamic model estimation from flight data. In addition to public presentations at the AIAA Atmospheric Flight Mechanics Conferences, two presentations at Boeing-Seattle were made during personal trips. These are discussed in the following: 1. Methodology of Aerodynamic Model Estimation from Flight Data. 2. Applications of F-16XL aerodynamic modeling. 3. Modeling of turbulence response. 5. Presentations at Boeing-Seattle. 6. Recommendations. and 7. References.

Lan, C. Edward

2003-01-01

402

Fundamental Aspects of the Aerodynamics of Turbojet Engine Combustors  

NASA Technical Reports Server (NTRS)

Aerodynamic considerations in the design of high performance combustors for turbojet engines are discussed. Aerodynamic problems concerning the preparation of the fuel-air mixture, the recirculation zone where primary combustion occurs, the secondary combustion zone, and the dilution zone were examined. An aerodynamic analysis of the entire primary chamber ensemble was carried out to determine the pressure drop between entry and exit. The aerodynamics of afterburn chambers are discussed. A model which can be used to investigate the evolution of temperature, pressure, and rate and efficiency of combustion the length of the chamber was developed.

Barrere, M.

1978-01-01

403

Workshop on Aircraft Surface Representation for Aerodynamic Computation  

NASA Technical Reports Server (NTRS)

Papers and discussions on surface representation and its integration with aerodynamics, computers, graphics, wind tunnel model fabrication, and flow field grid generation are presented. Surface definition is emphasized.

Gregory, T. J. (editor); Ashbaugh, J. (editor)

1980-01-01

404

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

405

PrandtlPlane High–Lift System Preliminary Aerodynamic Design.  

E-print Network

??An analysis of low-speed aerodynamics for an unconventional aircraft configuration has been carried out. This configuration, named Prandtlplane, implements Prandtl's Best Wing System for low… (more)

Iezzi, Giuseppe

2006-01-01

406

Vibration and noise  

NASA Astrophysics Data System (ADS)

A distinction is made between noise and pseudo-noise, noting the work of James Lighthill, and the different types of vibrations they excite are described. Consideration is given to noise produced by vortices and techniques for noise and vibration measurement are discussed.

Legendre, R.

1981-06-01

407

Noise and Helping Behavior  

Microsoft Academic Search

Three experiments were conducted in natural settings to examine the effects of noise on helping behavior. Individuals who were briefly exposed to high intensity construction noise were found to be less likely to help another person than were those exposed to noise of a considerably lower intensity. In addition, high noise levels interfered more with verbal help than with physical

Richard A. Page

1977-01-01

408

Noise, Health, and Architecture.  

ERIC Educational Resources Information Center

There is reasonable agreement that hearing impairment is related to noise exposure. This hearing loss due to noise is considered a serious health injury, but there is still difficulty in delineating the importance of noise related to people's general non-auditory well-being and health. Beside hearing loss, noise inhibits satisfactory speech…

Beranek, Leo L.

409

Non-Markovian noise  

SciTech Connect

The properties of non-Markovian noises with exponentially correlated memory are discussed. Considered are dichotomic noise, white shot noise, Gaussian white noise, and Gaussian colored noise. The stationary correlation functions of the non-Markovian versions of these noises are given by linear combinations of two or three exponential functions (colored noises) or of the [delta] function and exponential function (white noises). The non-Markovian white noises are well defined only when the kernel of the non-Markovian master equation contains a nonzero admixture of a Markovian term. Approximate equations governing the probability densities for processes driven by such non-Markovian noises are derived, including non-Markovian versions of the Fokker-Planck equation and the telegrapher's equation. As an example, it is shown how the non-Markovian nature changes the behavior of the driven linear process.

Fulinski, A. (Institute of Physics, Jagellonian University, Reymonta 4, PL-30-059 Krakow (Poland))

1994-10-01

410

Noise Pollution Clearinghouse  

NSDL National Science Digital Library

The Noise Pollution Clearinghouse (NPC) is a nonprofit organization devoted to collecting, disseminating, and archiving information resources relevant to the study of noise pollution. The NPC site contains an online library of related publications, a law library of proposed and current noise legislation, excerpts and summaries of recent noise pollution news stories, an annotated collection of online resources and information tools, and an annotated directory with links to other noise organizations. The entire clearinghouse is searchable by keyword.

411

Health Effects of Noise Pollution  

MedlinePLUS

... effects of noise pollution Health effects of noise pollution People of all ages, including children, teens, young ... noises around them. The health effects of noise pollution include: Hearing loss. Noise-induced hearing loss usually ...

412

DEVELOPMENT OF THE UNIVERSITY OF TEXAS AT ARLINGTON AERODYNAMICS RESEARCH CENTER  

E-print Network

DEVELOPMENT OF THE UNIVERSITY OF TEXAS AT ARLINGTON AERODYNAMICS RESEARCH CENTER Donald R. Wilson+ The University of Texas at Arlington Arlington, Texas 76019 Abstract The Aerodynamics Research Center (ARC research and educational programs in experimental aerodynamics, aerothernlodynamics and propulsion. When

Texas at Arlington, University of

413

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

414

Aerodynamic Focusing of Nanoparticles: II. Numerical Simulation of Particle Motion Through Aerodynamic Lenses  

Microsoft Academic Search

We have developed a numerical simulation methodology that is able to accurately characterize the focusing performance of aerodynamic lens systems. The commercial computational fluid dynamics (CFD) software FLUENT was used to simulate the gas flow field. Particle trajectories were tracked using the Lagrangian approach. Brownian motion of nanoparticles was successfully incorporated in our numerical simulations. This simulation tool was then

Xiaoliang Wang; Ashok Gidwani; Steven L. Girshick; Peter H. McMurry

2005-01-01

415

Effects of ice accretions on aircraft aerodynamics  

NASA Astrophysics Data System (ADS)

This article is a systematic and comprehensive review, correlation, and assessment of test results available in the public domain which address the aerodynamic performance and control degradations caused by various types of ice accretions on the lifting surfaces of fixed wing aircraft. To help put the various test results in perspective, overviews are provided first of the important factors and limitations involved in computational and experimental icing simulation techniques, as well as key aerodynamic testing simulation variables and governing flow physics issues. Following these are the actual reviews, assessments, and correlations of a large number of experimental measurements of various forms of mostly simulated in-flight and ground ice accretions, augmented where appropriate by similar measurements for other analogous forms of surface contamination and/or disruptions. In-flight icing categories reviewed include the initial and inter-cycle ice accretions inherent in the use of de-icing systems which are of particular concern because of widespread misconceptions about the thickness of such accretions which can be allowed before any serious consequences occur, and the runback/ridge ice accretions typically associated with larger-than-normal water droplet encounters which are of major concern because of the possible potential for catastrophic reductions in aerodynamic effectiveness. The other in-flight ice accretion category considered includes the more familiar large rime and glaze ice accretions, including ice shapes with rather grotesque features, where the concern is that, in spite of all the research conducted to date, the upper limit of penalties possible has probably not been defined. Lastly, the effects of various possible ground frost/ice accretions are considered. The concern with some of these is that for some types of configurations, all of the normally available operating margins to stall at takeoff may be erased if these accretions are not adequately removed prior to takeoff. Throughout this review, important voids in the available database are highlighted, as are instances where previous lessons learned have tended to be overlooked.

Lynch, Frank T.; Khodadoust, Abdollah

2001-11-01

416

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.

417

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

418

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.

419

Aerodynamics/ACEE: aircraft energy efficiency  

SciTech Connect

An overview is presented of a 10 year program managed by NASA which seeks to make possible the most efficient use of energy for aircraft propulsion and lift as well as provide a technology that can be used by U.S. manufacturers of air transports and engines. Supercritical wings, winglets, vortex drag reduction, high lift, active control, laminar flow control, and aerodynamics by computer are among the topics discussed. Wind tunnel models in flight verification of advanced technology, and the design, construction and testing of various aircraft structures are also described.

Not Available

1981-01-01

420

Aerodynamic prediction techniques for hypersonic configuration design  

NASA Technical Reports Server (NTRS)

An investigation of approximate theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at moderate hypersonic speeds was performed. Emphasis was placed on approaches that would be responsive to preliminary configuration design level of effort. Potential theory was examined in detail to meet this objective. Numerical pilot codes were developed for relatively simple three dimensional geometries to evaluate the capability of the approximate equations of motion considered. Results from the computations indicate good agreement with higher order solutions and experimental results for a variety of wing, body, and wing-body shapes for values of the hypersonic similarity parameter M delta approaching one.

1981-01-01

421

Aerodynamic sound generation caused by viscous processes  

NASA Astrophysics Data System (ADS)

A theoretical investigation of the effects of viscosity on aerodynamic sound generation by unheated low Mach-number flow is discussed. By means of the method of matched asymptotic expansions, which allows for a consistent estimation of the order of magnitude of each term in the hydrodynamic flow field as well as in the sound field, an analytical solution in terms of a multipole expansion is derived. The physical interpretation of the mathematical outcome of various theories by Morfey (1976), Kempton (1976), Hardin, and Kambe and Minota (1983) is compared and re-examined.

Obermeier, F.

1985-03-01

422

Report of the Panel on Aerodynamics  

NASA Technical Reports Server (NTRS)

Progress in aerodynamics over the past 50 years has been evidenced by the development of increasingly sophisticated and efficient flight vehicles throughout the flight spectrum. Advances have generally arisen in an evolutionary manner from experience gained in wind tunnel testing, flight testing, and improvements in analytical and computational capabilities. As a result of this evolutionary development, both military and commercial vehicles operate at a relatively high efficiency level. This observation plus the fact that airplanes have not changed appreciably in outward appearance over recent years has led some skeptics to conclude incorrectly that aerodynamics is a mature technology, with little to be gained from further developments in the field. It is of interest to note that progress in aerodynamics has occurred without a thorough understanding of the fundamental physics of flow, turbulence, vortex dynamics, and separated flow, for example. The present understanding of transition, turbulence, and boundary layer separation is actually very limited. However, these fundamental flow phenomena provide the key to reducing the viscous drag of aircraft. Drag reduction provides the greatest potential for increased flight efficiency from the standpoint of both saving energy and maximizing performance. Recent advances have led to innovative concepts for reducing turbulent friction drag by modifying the turbulent structure within the boundary layer. Further advances in this basic area should lead to methods for reducing skin friction drag significantly. The current challenges for military aircraft open entirely new fields of investigation for the aerodynamicist. The ability through very high speed information processing technology to totally integrate the flight and propulsion controls can permit an aircraft to fly with "complete abandon," avoiding departure, buffet, and other undesirable characteristics. To utilize these new control concepts, complex aerodynamic phenomena will have to be understood, predicted, and controlled. Current requirements for military aircraft include configuration optimization through a widened envelope from subsonic to supersonic and from low to high angles of attack. This task is further complicated by requirements for control of observables. These challenging new designs do not have the luxury of a large experimental data base from which to optimize for various parameter combinations. Consequently, there exists a strong need for better techniques, both experimental and computational, to permit design optimization in a complete sense.

Bradley, Richard G.; Bushnell, Dennis

1984-01-01

423

Aerodynamic design trends for commercial aircraft  

NASA Technical Reports Server (NTRS)

Recent research on advanced-configuration commercial aircraft at DFVLR is surveyed, with a focus on aerodynamic approaches to improved performance. Topics examined include transonic wings with variable camber or shock/boundary-layer control, wings with reduced friction drag or laminarized flow, prop-fan propulsion, and unusual configurations or wing profiles. Drawings, diagrams, and graphs of predicted performance are provided, and the need for extensive development efforts using powerful computer facilities, high-speed and low-speed wind tunnels, and flight tests of models (mounted on specially designed carrier aircraft) is indicated.

Hilbig, R.; Koerner, H.

1986-01-01

424

Aerodynamics/ACEE: Aircraft energy efficiency  

NASA Technical Reports Server (NTRS)

An overview is presented of a 10 year program managed by NASA which seeks to make possible the most efficient use of energy for aircraft propulsion and lift as well as provide a technology that can be used by U.S. manufacturers of air transports and engines. Supercritical wings, winglets, vortex drag reduction, high lift, active control, laminar flow control, and aerodynamics by computer are among the topics discussed. Wind tunnel models in flight verification of advanced technology, and the design, construction and testing of various aircraft structures are also described.

1981-01-01

425

Landing-gear noise prediction using high-order finite difference schemes  

NASA Astrophysics Data System (ADS)

Aerodynamic noise from a generic two-wheel landing-gear model is predicted by a CFD/FW-H hybrid approach. The unsteady flow-field is computed using a compressible Navier-Stokes solver based on high-order finite difference schemes and a fully structured grid. The calculated time history of the surface pressure data is used in an FW-H solver to predict the far-field noise levels. Both aerodynamic and aeroacoustic results are compared to wind tunnel measurements and are found to be in good agreement. The far-field noise was found to vary with the 6th power of the free-stream velocity. Individual contributions from three components, i.e. wheels, axle and strut of the landing-gear model are also investigated to identify the relative contribution to the total noise by each component. It is found that the wheels are the dominant noise source in general. Strong vortex shedding from the axle is the second major contributor to landing-gear noise. This work is part of Airbus LAnding Gear nOise database for CAA validatiON (LAGOON) program with the general purpose of evaluating current CFD/CAA and experimental techniques for airframe noise prediction.

Liu, Wen; Wook Kim, Jae; Zhang, Xin; Angland, David; Caruelle, Bastien

2013-07-01

426

A climatology of formation conditions for aerodynamic contrails  

NASA Astrophysics Data System (ADS)

Aircraft at cruise levels can cause two kinds of contrails, the well known exhaust contrails and the less well-known aerodynamic contrails. While the possible climate impact of exhaust contrails has been studied for many years, research on aerodynamic contrails began only a few years ago and nothing is known about a possible contribution of these ice clouds to climate impact. In order to make progress in this respect, we first need a climatology of their formation conditions and this is given in the present paper. Aerodynamic contrails are defined here 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. Furthermore, 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 argue 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.

2013-11-01

427

Helicopter rotor trailing edge noise. [noise prediction  

NASA Technical Reports Server (NTRS)

A two dimensional section of a helicopter main rotor blade was tested in an acoustic wind tunnel at close to full-scale Reynolds numbers to obtain boundary layer data and acoustic data for use in developing an acoustic scaling law and testing a first principles trailing edge noise theory. Results were extended to the rotating frame coordinate system to develop a helicopter rotor trailing edge noise prediction. Comparisons of the calculated noise levels with helicopter flyover spectra demonstrate that trailing edge noise contributes significantly to the total helicopter noise spectrum at high frequencies. This noise mechanism is expected to control the minimum rotor noise. In the case of noise radiation from a local blade segment, the acoustic directivity pattern is predicted by the first principles trailing edge noise theory. Acoustic spectra are predicted by a scaling law which includes Mach number, boundary layer thickness and observer position. Spectrum shape and sound pressure level are also predicted by the first principles theory but the analysis does not predict the Strouhal value identifying the spectrum peak.

Schlinker, R. H.; Amier, R. K.

1981-01-01

428

The aerodynamic and acoustic characteristics of an over-the-wing target-type thrust reverser model  

NASA Technical Reports Server (NTRS)

A static test of a large-scale, over-the-wing (OTW) powered-lift model was performed. The OTW propulsion system had been modified to incorporate a simple target-type thrust reverser as well as the normal rectangular OTW exhaust nozzle. Tests were performed in both the reverse thrust and approach configurations. The thrust reverser noise created by jet turbulence mixing and the OTW approach noise were both low frequency and broadband. When scaled to a 45,400-kg (100,000-lb) aircraft, the thrust reverser and approach configurations produced peak 152-m (500-ft) sideline perceived noise levels of 110 and 105 PNdB, respectively. The aerodynamic performance of the model showed that 50% or greater reverser effectiveness can be achieved without experiencing ingestion of exhaust gas or ground debris into the engine inlets.

Falarski, M. D.

1976-01-01

429

The Prediction and Analysis of Jet Flows and Scattered Turbulent Mixing Noise About Flight Vehicle Airframes  

NASA Technical Reports Server (NTRS)

Jet flows interacting with nearby surfaces exhibit a complex behavior in which acoustic and aerodynamic characteristics are altered. The physical understanding and prediction of these characteristics are essential to designing future low noise aircraft. A new approach is created for predicting scattered jet mixing noise that utilizes an acoustic analogy and steady Reynolds-averaged Navier-Stokes solutions. A tailored Green's function accounts for the propagation of mixing noise about the air-frame and is calculated numerically using a newly developed ray tracing method. The steady aerodynamic statistics, associated unsteady sound source, and acoustic intensity are examined as jet conditions are varied about a large at plate. A non-dimensional number is proposed to estimate the effect of the aerodynamic noise source relative to jet operating condition and airframe position. The steady Reynolds-averaged Navier-Stokes solutions, acoustic analogy, tailored Green's function, non- dimensional number, and predicted noise are validated with a wide variety of measurements. The combination of the developed theory, ray tracing method, and careful implementation in a stand-alone computer program result in an approach that is more first principles oriented than alternatives, computationally efficient, and captures the relevant physics of fluid-structure interaction.

Miller, Steven A.

2014-01-01

430

The Prediction and Analysis of Jet Flows and Scattered Turbulent Mixing Noise about Flight Vehicle Airframes  

NASA Technical Reports Server (NTRS)

Jet flows interacting with nearby surfaces exhibit a complex behavior in which acoustic and aerodynamic characteristics are altered. The physical understanding and prediction of these characteristics are essential to designing future low noise aircraft. A new approach is created for predicting scattered jet mixing noise that utilizes an acoustic analogy and steady Reynolds-averaged Navier-Stokes solutions. A tailored Green's function accounts for the propagation of mixing noise about the airframe and is calculated numerically using a newly developed ray tracing method. The steady aerodynamic statistics, associated unsteady sound source, and acoustic intensity are examined as jet conditions are varied about a large flat plate. A non-dimensional number is proposed to estimate the effect of the aerodynamic noise source relative to jet operating condition and airframe position.The steady Reynolds-averaged Navier-Stokes solutions, acoustic analogy, tailored Green's function, non-dimensional number, and predicted noise are validated with a wide variety of measurements. The combination of the developed theory, ray tracing method, and careful implementation in a stand-alone computer program result in an approach that is more first principles oriented than alternatives, computationally efficient, and captures the relevant physics of fluid-structure interaction.

Miller, Steven A. E.

2014-01-01

431

Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel  

NASA Technical Reports Server (NTRS)

Three supersonic helical tip speed propellers were tested in the NASA Lewis 8- by 6-foot wind tunnel. This is a perforated-wall wind tunnel but it does not have acoustic damping material on its walls. The propellers were tested at tunnel through flow Mach numbers of 0.6, 0.7, 0.75, 0.8, and 0.85 with different rotational speeds and blade setting angles. The three propellers, which had approximately the same aerodynamic performance, incorporated different plan forms and different amounts of sweep and yielded different near field noise levels. The acoustically designed propeller had 45 deg of tip sweep and was significantly quieter at M = 0.8 cruise than the straight bladed propeller. The intermediate 30 deg tip sweep propeller, which was swept for aerodynamic purposes, exhibited noise that was between the other two propellers. Noise trends with varying helical tip Mach number and blade loading were also observed.

Dittmar, J. H.; Jeracki, R. J.; Blaha, B. J.

1979-01-01

432

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

433

The Aerodynamic Resistance to a Sphere Rotating at High Speed  

Microsoft Academic Search

An attempt has been made to adapt the technique of magnetic suspension of steel rotors to the study of high-speed aerodynamic problems. Surface speeds up to ca. 800 m\\/s are possible. The advantages and shortcomings of the technique from the aerodynamic point of view are discussed together with the different regimes of flow at present attainable with the apparatus. The

F. P. Bowden; R. G. Lord

1963-01-01

434

Estimating aerodynamic resistance of rough surfaces using angular reflectance  

Microsoft Academic Search

Current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance, and over-estimate the erodible area by assuming it is not covered by roughness elements. We address these shortfalls with a new model which estimates aerodynamic roughness length (z0) using angular reflectance of a rough surface. The new model

Adrian Chappell; Scott Van Pelt; Ted Zobeck; Zhibao Dong

2010-01-01

435

Development of aerodynamics for a solar race car  

Microsoft Academic Search

The dominant factor of a solar car is running resistance, especially aerodynamic drag; and the reduction of the CD (drag coefficient)× A (frontal projected area) value is a crucial task to maximize the performance of a solar car. This paper will introduce the aerodynamic approach of the '96 Honda solar car which participated in the World Solar Challenge, the world's

Hiroyuki Ozawa; Sumio Nishikawa; Dai Higashida

1998-01-01

436

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

437

OUTLINE FOR Chapter 4 AERODYNAMICS (W3-1-1)  

E-print Network

NACA 2412 AIRFOIL CHARACTERISTICS Moment coefficient about the c/4 Aerodynamic Center: about the c/42013/4/22 1 OUTLINE FOR Chapter 4 AERODYNAMICS (W3-1-1) AIRFOIL NOMENCLATURE The leading edge-digit" series: ( http://www.ppart.de/programming/java/profiles/NACA4.html ) Example: NACA 2412 (2% camber at 40

Leu, Tzong-Shyng "Jeremy"

438

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

439

Aerodynamic Analysis Of Voice In Persons With Laryngopharyngeal Reflux  

Microsoft Academic Search

Objectives of the study: The individuals with laryngopharyngeal reflux are prone for aspiration of refluxed contents and so there is a need for aerodynamic evaluation in these individuals. Hence, the present study investigated the aerodynamic characteristics in individuals with Laryngopharyngeal reflux. Study design: Prospective control group design. Method: Thirty laryngopharyngeal reflux subjects and 30 normal subjects participated in the study.

Radish Kumar; Jayashree S. Bhat

440

Analysis of satellite laser ranging data to investigate satellite aerodynamics  

Microsoft Academic Search

In Low Earth Orbit (LEO) (under 1500 km) the effects of aerodynamic forces upon the trajectory of a satellite are far from negligible when compared to the accuracy of instrumentation flown on remote sensing satellites. To accurately calculate the net aerodynamic force, the atmospheric conditions and the interactions between the surface and the atmosphere need to be known continuously. There

I. K. Harrison; G. G. Swinerd

1995-01-01

441

Experimental aerodynamics research on a hypersonic vehicle  

SciTech Connect

Aerodynamic force and moment measurements and flow visualization results are presented for a hypersonic vehicle configuration at Mach 8. The basic vehicle configuration is a spherically blunted 10[degree] half-angle cone with a slice parallel with the axis of the vehicle. On the slice portion of the vehicle, a flap could be attached so that deflection angles of 10[degree], 20[degree] and 30[degree] could be obtained. All of the experimental results were obtained in the Sandia Mach 8 hypersonic wind tunnel for laminar boundary layer conditions. Flow visualization results include shear stress sensitive liquid crystal photographs, surface streak flow photographs (using liquid crystals), and spark schlieren photographs and video. The liquid crystals were used as an aid in verifying that a laminar boundary layer existed over the entire body. The surface flow photo-graphs show attached and separated flow on both the leeside of the vehicle and near the flap. A detailed uncertainty analysis was conducted to estimate the contributors to body force and moment measurement uncertainty. Comparisons are made with computational results to evaluate both the experimental and numerical results. This extensive set of high-quality experimental force and moment measurements is recommended for use in the calibration and validation of relevant computational aerodynamics codes.

Oberkampf, W.L.; Aeschliman, D.P.; Tate, R.E.; Henfling, J.F.

1993-04-01

442

Experimental aerodynamics research on a hypersonic vehicle  

SciTech Connect

Aerodynamic force and moment measurements and flow visualization results are presented for a hypersonic vehicle configuration at Mach 8. The basic vehicle configuration is a spherically blunted 10{degree} half-angle cone with a slice parallel with the axis of the vehicle. On the slice portion of the vehicle, a flap could be attached so that deflection angles of 10{degree}, 20{degree} and 30{degree} could be obtained. All of the experimental results were obtained in the Sandia Mach 8 hypersonic wind tunnel for laminar boundary layer conditions. Flow visualization results include shear stress sensitive liquid crystal photographs, surface streak flow photographs (using liquid crystals), and spark schlieren photographs and video. The liquid crystals were used as an aid in verifying that a laminar boundary layer existed over the entire body. The surface flow photo-graphs show attached and separated flow on both the leeside of the vehicle and near the flap. A detailed uncertainty analysis was conducted to estimate the contributors to body force and moment measurement uncertainty. Comparisons are made with computational results to evaluate both the experimental and numerical results. This extensive set of high-quality experimental force and moment measurements is recommended for use in the calibration and validation of relevant computational aerodynamics codes.

Oberkampf, W.L.; Aeschliman, D.P.; Tate, R.E.; Henfling, J.F.

1993-04-01

443

(Aerodynamic focusing of particles and heavy molecules)  

SciTech Connect

By accelerating a gas containing suspended particles or large molecules through a converging nozzle, the suspended species may be focused and therefore used to write fine lines on a surface. Our objective was to study the limits on how narrow this focal region could be as a function of particle size. We find that, for monodisperse particles with masses m{sub p} some 3.6 {times} 10{sup 5} times larger than the molecular mass m of the carrier gas (diameters above some 100{angstrom}), there is no fundamental obstacle to directly write submicron features. However, this conclusion has been verified experimentally only with particles larger than 0.1 {mu}m. Experimental, theoretical and numerical studies on the defocusing role of Brownian motion for very small particles or heavy molecules have shown that high resolution (purely aerodynamic) focusing is impossible with volatile molecules whose masses are typically smaller than 1000 Dalton. For these, the minimal focal diameter after optimization appears to be 5{radical}(m/m{sub p}) times the nozzle diameter d{sub n}. But combinations of focused lasers and aerodynamic focusing appear as promising for direct writing with molecular precursors. Theoretical and numerical schemes capable of predicting the evolution of the focusing beam, including Brownian motion effects, have been developed, although further numerical work would be desirable. 11 refs.

de la Mora, J.F.

1990-01-08

444

Cricket Ball Aerodynamics: Myth Versus Science  

NASA Technical Reports Server (NTRS)

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 responsible for the nonlinear flight or "swing" of a cricket ball were identified several years ago and many papers have been published on the subject. In the last 20 years or so, several experimental investigations have been conducted on cricket ball swing, which revealed the amount of attainable swing, and the parameters that affect it. A general overview of these findings is presented with emphasis on the concept of late swing and the effects of meteorological conditions on swing. In addition, the relatively new concept of "reverse" swing, how it can be achieved in practice and the role in it of ball "tampering", are discussed in detail. A discussion of the "white" cricket ball used in last year's World Cup, which supposedly possesses different swing properties compared to a conventional red ball, is also presented.

Mehta, Rabindra D.; Koga, Demmis J. (Technical Monitor)

2000-01-01

445

Air flow testing on aerodynamic truck  

NASA Technical Reports Server (NTRS)

This photograph illustrates a standard passenger van modified at the Dryden Flight Research Center to investigate the aerodynamics of trucks. The resulting vehicle--re-fashioned with sheet metal--resembled a motor home, with rounded vertical corners on the vehicle's front and rear sections. For subsequent tests, researchers installed a 'boat tail' structure, shown in the photograph. During a decade spanning the 1970s and 1980s, Dryden researchers conducted tests to determine the extent to which adjustments in the shape of trucks reduced aerodynamic drag and improved efficiency. During the tests, the vehicle's sides were fitted with tufts, or strings, that showed air flow. The investigators concluded that rounding the vertical corners front and rear reduced drag by 40 percent, yet decreased the vehicle's internal volume by only 1.3 percent. Rounding both the vertical and horizontal corners cut drag by 54 percent, resulting in a three percent loss of internal volume. A second group of tests added a faired underbody and a boat tail, the latter feature resulting in drag reduction of about 15 percent.

1981-01-01

446

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

447

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

448

Cascade flutter analysis with transient response aerodynamics  

NASA Technical Reports Server (NTRS)

Two methods for calculating linear frequency domain aerodynamic coefficients from a time marching Full Potential cascade solver are developed and verified. In the first method, the Influence Coefficient, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier Transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers.

Bakhle, M. A.; Mahajan, A. J.; Keith, T. G., Jr.; Stefko, G. L.

1991-01-01

449

Cascade flutter analysis with transient response aerodynamics  

NASA Technical Reports Server (NTRS)

Two methods for calculating linear frequency domain aerodynamic coefficients from a time-marching Full-Potential cascade solver are developed and verified. In the first method, the Influence Coefficient method, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response method, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers using both flat plates and actual airfoils.

Bakhle, Milind A.; Mahajan, Aparajit J.; Keith, Theo G., Jr.; Stefko, George L.

1991-01-01

450

Rotor/wing aerodynamic interactions in hover  

NASA Technical Reports Server (NTRS)

An experimental and theoretical investigation of rotor/wing aerodynamic interactions in hover is described. The experimental investigation consisted of both a large-scale and small-scale test. A 0.658-scale, V-22 rotor and wing was used in the large-scale test. Wind download, wing surface pressure, rotor performance, and rotor downwash data from the large-scale test are presented. A small-scale experiment was conducted to determine how changes in the rotor/wing geometry affected the aerodynamic interactions. These geometry variations included the distance between the rotor and wing, wing incidence angle, and configurations both with the rotor axis at the tip of the wing (tilt rotor configuration) and with the rotor axis at the center of the wing (compound helicopter configuration). A wing with boundary-layer control was also tested to evaluate the effect of leading and trailing edge upper surface blowing on the wing download. A computationally efficient, semi-empirical theory was developed to predict the download on the wing. Finally, correlations between the theoretical predictions and test data are presented.

Felker, F. F.; Light, J. S.

1986-01-01

451

Influence of surrounding structures upon the aerodynamic and acoustic performance of the outdoor unit of a split air-conditioner  

NASA Astrophysics Data System (ADS)

DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics(CFD) and computational aerodynamic acoustics(CAA) simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures(i.e. the heat sink, the bell-mouth type shroud and the outlet grille) upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring's size and throat's depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %(i.e. 100 m3·h-1) at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.

Wu, Chengjun; Liu, Jiang; Pan, Jie

2014-07-01

452

Impact of computers on aerodynamics research and development  

SciTech Connect

Factors motivating the development of computational aerodynamics as a discipline are traced back to the limitations of the tools available to the aerodynamicist before the development of digital computers. Governing equations in exact and approximate forms are discussed together with approaches to their numerical solution. Example results obtained from the successively refined forms of the equations are presented and discussed, both in the context of levels of computer power required and the degree of the effect that their solution has on aerodynamic research and development. Factors pacing advances in computational aerodynamics are identified, including the amount of computational power required to take the next major step in the discipline. Finally, the Numerical Aerodynamic Simulation (NAS) Program--with its 1987 target of achieving a sustained computational rate of 1 billion floating-point operations per second operating on a memory of 240 million words--is briefly discussed in terms of its projected effect on the future of computational aerodynamics.

Peterson, V.L.

1984-01-01

453

Impact of computers on aerodynamics research and development  

NASA Technical Reports Server (NTRS)

Factors motivating the development of computational aerodynamics as a discipline are traced back to the limitations of the tools available to the aerodynamicist before the development of digital computers. Governing equations in exact and approximate forms are discussed together with approaches to their numerical solution. Example results obtained from the successively refined forms of the equations are presented and discussed, both in the context of levels of computer power required and the degree of the effect that their solution has on aerodynamic research and development. Factors pacing advances in computational aerodynamics are identified, including the amount of computational power required to take the next major step in the discipline. Finally, the Numerical Aerodynamic Simulation (NAS) Program - with its 1987 target of achieving a sustained computational rate of 1 billion floating-point operations per second operating on a memory of 240 million words - is briefly discussed in terms of its projected effect on the future of computational aerodynamics.

Peterson, V. L.

1984-01-01

454

Review of Integrated Noise Model (INM) Equations and Processes  

NASA Technical Reports Server (NTRS)

The FAA's Integrated Noise Model (INM) relies on the methods of the SAE AIR-1845 'Procedure for the Calculation of Airplane Noise in the Vicinity of Airports' issued in 1986. Simplifying assumptions for aerodynamics and noise calculation were made in the SAE standard and the INM based on the limited computing power commonly available then. The key objectives of this study are 1) to test some of those assumptions against Boeing source data, and 2) to automate the manufacturer's methods of data development to enable the maintenance of a consistent INM database over time. These new automated tools were used to generate INM database submissions for six airplane types :737-700 (CFM56-7 24K), 767-400ER (CF6-80C2BF), 777-300 (Trent 892), 717-200 (BR7 15), 757-300 (RR535E4B), and the 737-800 (CFM56-7 26K).

Shepherd, Kevin P. (Technical Monitor); Forsyth, David W.; Gulding, John; DiPardo, Joseph

2003-01-01

455

Application of Passive Porous Treatment to Slat Trailing Edge Noise  

NASA Technical Reports Server (NTRS)

Porous trailing-edge treatment is investigated as a passive means for slat noise reduction by using time-accurate simulations based on Reynolds-averaged Navier-Stokes equations. For the model scale high-lift configuration used during previous experiments in the Low-Turbulence Pressure Tunnel at NASA Langley Research Center, application of the proposed treatment over a minute fraction of the slat surface area is shown to mitigate the noise impact of the trailing edge, with no measurable aerodynamic penalty. Assessment of the pressure fluctuations in the vicinity of the treated edge indicates a potential noise reduction in excess of 20 dB. The primary mechanism underlying this reduction is related to the reduced strength of Strouhal shedding from the finite thickness trailing edge. A secondary effect of the treatment involves an upward shift in the Strouhal-shedding frequency to a frequency band of reduced auditory sensitivity in a full-scale application.

Khorrami, Mehdi R.; Choudhari, Meelan M.

2003-01-01

456

The radiated noise from isotropic turbulence and heated jets  

NASA Technical Reports Server (NTRS)

Our understanding of aerodynamic noise has its foundations in the work of Sir James Lighthill (1952), which was the first major advance in acoustics since the pioneering work of Lord Rayleigh in the last century. The combination of Lighthill's theory of aerodynamic noise as applied to turbulent flows and the experimental growing database from the early 1950's was quickly exploited by various jet propulsion engine designers in reducing the noise of jet engines at takeoff and landing to levels marginally acceptable to communities living in the neighborhoods of airports. The success in this noise containment led to the rapid growth of fast economical subsonic civil transport aircraft worldwide throughout the 1960's and has continued to the present day. One important factor in this success story has been the improvements in the engine cycle that have led to both reductions in specific fuel consumption and noise. The second is the introduction of Noise Certification, which specifies the maximum noise levels at takeoff and landing that all aircraft must meet before they can be entered on the Civil Aircraft Register. The growing interest in the development of a new supersonic civil transport to replace 'Concorde' in the early years of the next century has led to a resurgence of interest in the more challenging problem of predicting the noise of hot supersonic jets and developing means of aircraft noise reduction at takeoff and landing to meet the standards now accepted for subsonic Noise Certification. The prediction of aircraft noise to the accuracy required to meet Noise Certification requirements has necessitated reliance upon experimental measurements and empirically derived laws based on the available experimental data bases. These laws have their foundation in the results from Lighthill's theory, but in the case of jet noise, where the noise is generated in the turbulent mixing region with the external ambient fluid, the complexity of the turbulent motion has prevented the full deployment of Lighthill's theory from being achieved. However, the growth of the supercomputer and its applications in the study of the structure of turbulent shear flows in both unbounded and wall bounded flows, which complements and in certain cases extends the work of the few dedicated experimental groups working in this field for the past forty years, provides an opportunity and challenge to accurately predict the noise from jets. Moreover a combination of numerical and laboratory experiments offers the hope that in the not too distant future the physics of noise generation and flow interaction will be better understood and it will then be possible to not only improve the accuracy of noise prediction but also to explore and optimize schemes for noise reduction. The present challenge is to provide time and space accurate numerical databases for heated subsonic and supersonic jets to provide information on the fourth-order space-time covariance of Lighthill's equivalent stress tensor, T(ij), which governs the characteristics of the farfield radiated noise and the total acoustic power. Validation with available experimental databases will establish how close Lighthill's theory is to the accurate prediction of the directivity and spectrum of jet noise and the total acoustic power, and the need, in the applications of the theory, to include the effects of flow-acoustic interaction.

Lilley, G. M.

1995-01-01

457

EDITORIAL: Advanced Measurement Techniques in Aerodynamics Advanced Measurement Techniques in Aerodynamics  

NASA Astrophysics Data System (ADS)

This issue of Measurement Science and Technology contains a special feature section with selected papers from the EWA International workshop on Advanced Measurement Techniques in Aerodynamics, which was held at the Delft University of Technology, Delft, The Netherlands, 31 March-1 April 2008. The workshop was funded by the European Windtunnel Association (EWA, www.eu-ewa.aero), which is an EU-funded network established in 2004 under the European Sixth Framework Programme with the goal of integrating and standardizing the different capabilities of European wind tunnels and related flow measurement techniques. The workshop was organized with the objective of stimulating discussion among leading European universities, research institutes and industry in the field of advanced aerodynamics measurement techniques, in order to provide a transfer of new ideas from upstream research centres to wind tunnel operators and industrial users. Non-intrusive flow diagnostic techniques nowadays offer renewed capabilities for industrial wind-tunnel applications. Particle image velocimetry (PIV) plays a leading role for particular applications (unsteady and complex flows, rotorcraft aerodynamics, turbulent separated flows) and can provide solutions that cannot be achieved with conventional techniques (e.g. in the analysis of vortex flows). This formed the main motivation to revise the state-of-the-art of PIV along with other non-intrusive optical techniques such as PSP, DGV and BOS. The two-day workshop contained sessions dedicated to several specific topics: rotorcraft aerodynamics applications; state-of-the-art of high-speed PIV and configurations for time-resolved measurements; three-dimensional PIV; non-intrusive load characterization by PSP and PIV. The main conclusion emerging from the closing discussion was that the new capabilities offered by time-resolved PIV are of great scientific and industrial interest for application to unsteady flows and in particular to the determination of unsteady aerodynamic forces and loads. We believe that this workshop provided a useful framework facilitating the transfer of new ideas from developer to the user communities. At the same time the workshop provided the upstream research community with important feedback about the areas of relevance for industrial aerodynamics.

van Oudheusden, B. W.; Scarano, F.

2009-07-01

458

Noise level evaluation of dental handpieces.  

PubMed

We evaluated the noise level of fourteen air-driven handpieces, six low speed (less than 20,000 rev/min) and eight high speed (greater than 160,000 rev/min), with respect to a three-directional co-ordinate system and distances of 6, 12 and 18 in. in each chosen direction. A two-way analysis of variance of the noise level