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1

Aircraft aerodynamic noise during approach  

NASA Astrophysics Data System (ADS)

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

Parant, J. L.

2

Minimum Energy Guidance for Aerodynamically Controlled Missiles  

Microsoft Academic Search

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

Robert Wes Morgan; Hal Tharp; Thomas L. Vincent

2011-01-01

3

Aerodynamics.  

National Technical Information Service (NTIS)

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

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

1989-01-01

4

Aerodynamic levitation : an approach to microgravity.  

SciTech Connect

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

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

2000-12-05

5

Embedded Parallelization Approach for Optimization in Aerodynamic Design  

Microsoft Academic Search

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

S. Peigin; Boris Epstein

2004-01-01

6

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

National Technical Information Service (NTIS)

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

R. M. Wood

2003-01-01

7

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

Microsoft Academic Search

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

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

2012-01-01

8

Systematic approach to analyzing and reducing aerodynamic drag of heavy vehicles  

Microsoft Academic Search

This paper presents an approach for reducing aerodynamic drag of heavy vehicles by systematically analyzing trailer components using existing computational tools and moving on to the analyses of integrated tractor-trailers using advanced computational tools. Experimental verification and validation are also an important part of this approach. The project is currently in the development phase while we are in the process

R. McCallen; F. Browand; A. Leonard; W. Rutledge

1997-01-01

9

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

National Technical Information Service (NTIS)

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

D. J. Homan

1977-01-01

10

Systematic approach to analyzing and reducing aerodynamic drag of heavy vehicles  

SciTech Connect

This paper presents an approach for reducing aerodynamic drag of heavy vehicles by systematically analyzing trailer components using existing computational tools and moving on to the analyses of integrated tractor-trailers using advanced computational tools. Experimental verification and validation are also an important part of this approach. The project is currently in the development phase while we are in the process of constructing a Multi-Year Program Plan. Projects I and 2 as described in this paper are the anticipated project direction. Also included are results from past and current related activities by the project participants which demonstrate the analysis approach.

McCallen, R.; Browand, F.; Leonard, A.; Rutledge, W.

1997-09-16

11

Optimal shape design of aerodynamic configurations: A Newton-Krylov approach  

NASA Astrophysics Data System (ADS)

Optimal shape design of aerodynamic configurations is a challenging problem due to the nonlinear effects of complex flow features such as shock waves, boundary layers, and separation. A Newton-Krylov algorithm is presented for aerodynamic design using gradient-based numerical optimization. The flow is governed by the two-dimensional compressible Navier-Stokes equations in conjunction with a one-equation turbulence model, which are discretized on multi-block structured grids. The discrete-adjoint method is applied to compute the objective function gradient. The adjoint equation is solved using the preconditioned generalized minimal residual (GMRES) method. A novel preconditioner is introduced, and together with a complete differentiation of the discretized Navier-Stokes and turbulence model equations, this results in an accurate and efficient evaluation of the gradient. The gradient is obtained in just one-fifth to one-half of the time required to converge a flow solution. Furthermore, fast flow solutions are obtained using the same preconditioned GMRES method in conjunction with an inexact-Newton approach. Optimization constraints are enforced through a penalty formulation, and the resulting unconstrained problem is solved via a quasi-Newton method. The performance of the new algorithm is demonstrated for several design examples that include lift enhancement, where the optimal position of a flap is determined within a high-lift configuration, lift-constrained drag minimization at multiple transonic operating points, and the computation of a Pareto front based on competing objectives. In all examples, the gradient is reduced by several orders of magnitude, indicating that a local minimum has been obtained. Overall, the results show that the new algorithm is among the fastest presently available for aerodynamic shape optimization and provides an effective approach for practical aerodynamic design.

Nemec, Marian

12

Horizontal Axis Wind Energy Conversion System with Aerodynamic Blade Pitch Control  

Microsoft Academic Search

The horizontal axis wind turbine converts wind into electrical energy and includes a pitch control vane with a flyweight mechanism on each rotor blade to provide aerodynamic efficiency at operating wind velocities, near constant speed and zero lift pitch of the rotor blades when speeds exceed the design speed of the system. A gravity neutralization means composed of a bevel

Rossman

1983-01-01

13

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

Microsoft Academic Search

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

A. K. Barlas

2007-01-01

14

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

PubMed

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

Nakata, Toshiyuki; Liu, Hao

2011-08-10

15

Aerodynamic flutter analysis of cable-supported bridges by multi-mode and full-mode approaches  

Microsoft Academic Search

A brief history of bridge flutter analysis is presented first. It is followed by an examination of a multi-mode procedure and a more comprehensive full-mode approach in aerodynamic flutter analysis of long-span cable-supported bridges. Particularly, when the span is very long and\\/or the structural stiffness is not fully implemented, a combination of more than two structural vibration modes can have

Y. J. Ge; H. Tanaka

2000-01-01

16

Intelligent aerodynamic\\/propulsion flight control for flight safety: a nonlinear adaptive approach  

Microsoft Academic Search

This paper presents an intelligent fault tolerant flight control system that blends aerodynamic and propulsion actuation for safe flight operation in the presence of actuator failures. Fault tolerance is obtained by a nonlinear adaptive control strategy based on on-line learning neural networks and actuator reallocation scheme. The adaptive control block incorporates a recently developed technique for adaptation in the presence

Moshe Idan; Matthew Johnson; Anthony J. Calise; John Kaneshige

2001-01-01

17

An approach for the development of an aerodynamic-structural interaction numerical simulation for aeropropulsion systems  

SciTech Connect

Traditionally, aeropropulsion structural performance and aerodynamic performance have been designed separately and later mated together via flight testing. In today`s atmosphere of declining resources, it is imperative that more productive ways of designing and verifying aeropropulsion performance and structural interaction be made available to the aerospace industry. One method of obtaining a more productive design and evaluation capability is through the use of numerical simulations. Currently, Lawrence Livermore National Laboratory has developed a generalized fluid/structural interaction code known as ALE3D. This code is capable of characterizing fluid and structural interaction for components such as the combustor, fan/stators, inlet and/or nozzles. This code solves the 3D Euler equations and has been applied to several aeropropulsion applications such as a supersonic inlet and a combustor rupture simulation. To characterize aerodynamic-structural interaction for rotating components such as the compressor, appropriate turbomachinery simulations would need to be implemented within the ALE3D structure. The Arnold Engineering Development Center is currently developing a three-dimensional compression system code known as TEACC (Turbine Engine Analysis Compressor Code). TEACC also solves the 3D Euler equations and is intended to simulate dynamic behavior such as inlet distortion, surge or rotating stall. The technology being developed within the TEACC effort provides the necessary turbomachinery simulation for implementation into ALE3D. This paper describes a methodology to combine three-dimensional aerodynamic turbomachinery technology into the existing aerodynamic-structural interaction simulation, ALE3D to obtain the desired aerodynamic and structural integrated simulation for an aeropropulsion system.

Naziar, J. [Boeing Commerical Airplane Group, Seattle, WA (United States). Propulsion Research; Couch, R. [Lawrence Livermore National Lab., CA (United States); Davis, M. [Sverdrup Technology, Inc., Arnold Air Force Base, TN (United States). Arnold Engineering Development Center

1996-01-01

18

Laboratory evaluation of fan/filter units' aerodynamic and energy performance  

SciTech Connect

The paper discusses the benefits of having a consistent testing method to characterize aerodynamic and energy performance of FFUs. It presents evaluation methods of laboratory-measured performance of ten relatively new, 1220 mm x 610 mm (or 4 ft x 2 ft) fan-filter units (FFUs), and includes results of a set of relevant metrics such as energy performance indices (EPI) based upon the sample FFUs tested. This paper concludes that there are variations in FFUs' performance, and that using a consistent testing and evaluation method can generate compatible and comparable FFU performance information. The paper also suggests that benefits and opportunities exist for our method of testing FFU energy performance to be integrated in future recommended practices.

Xu, Tengfang; Jeng, Ming-Shan

2004-07-27

19

PREFACE: Aerodynamic sound Aerodynamic sound  

Microsoft Academic Search

The modern theory of aerodynamic sound originates from Lighthill's two papers in 1952 and 1954, as is well known. I have heard that Lighthill was motivated in writing the papers by the jet-noise emitted by the newly commercialized jet-engined airplanes at that time. The technology of aerodynamic sound is destined for environmental problems. Therefore the theory should always be applied

Sadao Akishita

2010-01-01

20

Hypersonic Aerodynamics.  

National Technical Information Service (NTIS)

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

S. M. Bogdonoff

1975-01-01

21

Aerodynamic Drag.  

National Technical Information Service (NTIS)

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

1973-01-01

22

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

23

Energy based aerodynamic modeling: increasing fidelity of fixed-wing constructive entities  

Microsoft Academic Search

Distributed Mission Operations (DMO) is an ideal setting for practicing Beyond Visual Range air-to-air tactics. Hardware and software limitations often dictate the use of simplified aerodynamic models for control of fixed wing constructive entities within synthetic environments. In many tactical situations the long range fight will disintegrate into close-in air combat, which for a variety of reason is difficult to

Mitch Pohlman; Clinton Kam

2007-01-01

24

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

25

Awesome Aerodynamics!  

NSDL National Science Digital Library

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

2010-01-01

26

Missile Aerodynamics: NEAR Conference on Missile Aerodynamics.  

National Technical Information Service (NTIS)

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

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

1988-01-01

27

Aerodynamic parameter estimation of an Unmanned Aerial Vehicle based on extended kalman filter and its higher order approach  

Microsoft Academic Search

Aerodynamic parameter estimation provides an effective way for aerospace system modelling using measured data from flight test, especially for the purpose of developing elaborate simulation environments and control systems design of Unmanned Aerial Vehicle (UAV) with short design cycles and reduced cost. However, parameter identification of airplane dynamics is complicated because of its nonlinear identification models and the combination of

Li Meng; Liu Li; S. M. Veres

2010-01-01

28

Aerodynamic performance of a transonic turbine guide vane with trailing edge coolant ejection. Part 1: Experimental approach  

Microsoft Academic Search

Inlet guide vanes (IGV) of high-temperature gas turbines require an effective trailing edge cooling. But this cooling significantly influences the aerodynamic performance caused by the unavoidable thickening of the trailing edge and the interference of the cooling flow with the main flow. As part of a comprehensive research program, an inlet guide vane was designed and manufactured with two different

C. Kapteijn; J. Amecke; V. Michelassi

1996-01-01

29

A unified approach to aerodynamic damping and drag/lift instabilities, and its application to dry inclined cable galloping  

NASA Astrophysics Data System (ADS)

Inclined cables of cable-stayed bridges often experience large amplitude vibrations. One of the potential excitation mechanisms is dry inclined cable galloping, which has been observed in wind tunnel tests but which has not previously been fully explained theoretically. In this paper, a general expression is derived for the quasi-steady aerodynamic damping (positive or negative) of a cylinder of arbitrary cross-section yawed/inclined to the flow, for small amplitude vibrations in any plane. The expression covers the special cases of conventional quasi-steady aerodynamic damping, Den Hartog galloping and the drag crisis, as well as dry inclined cable galloping. A nondimensional aerodynamic damping parameter governing this behaviour is proposed, which is a function of only the Reynolds number, the angle between the wind velocity and the cable axis, and the orientation of the vibration plane. Measured static force coefficients from wind tunnel tests have been used with the theoretical expression to predict values of this parameter. Two main areas of instability (i.e. negative aerodynamic damping) have been identified, both in the critical Reynolds number region, one of which was previously observed in separate wind tunnel tests on a dynamic cable model. The minimum values of structural damping required to prevent dry inclined cable galloping are defined, and other factors in the behaviour in practice are discussed.

MacDonald, J. H. G.; Larose, G. L.

2006-02-01

30

Analysis of Prop-Fan/Airframe Aerodynamic Integration.  

National Technical Information Service (NTIS)

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

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

1978-01-01

31

Aerodynamics of Horizontal Axis Wind Turbines  

Microsoft Academic Search

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

J. Gordon Leishman

32

Identification of Aerodynamic Coefficients of Ground Vehicles Using Neural Network  

Microsoft Academic Search

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

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

2007-01-01

33

Multicomponent Aerodynamic Magnetoelectric Balance.  

National Technical Information Service (NTIS)

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

N. P. Levitskii

1973-01-01

34

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

35

Dynamic Soaring: Aerodynamics for Albatrosses  

ERIC Educational Resources Information Center

|Albatrosses have evolved to soar and glide efficiently. By maximizing their lift-to-drag ratio "L/D", albatrosses can gain energy from the wind and can travel long distances with little effort. We simplify the difficult aerodynamic equations of motion by assuming that albatrosses maintain a constant "L/D". Analytic solutions to the simplified…

Denny, Mark

2009-01-01

36

Aerodynamic performance of a transonic turbine guide vane with trailing edge coolant ejection. Part 1: Experimental approach  

SciTech Connect

Inlet guide vanes (IGV) of high-temperature gas turbines require an effective trailing edge cooling. But this cooling significantly influences the aerodynamic performance caused by the unavoidable thickening of the trailing edge and the interference of the cooling flow with the main flow. As part of a comprehensive research program, an inlet guide vane was designed and manufactured with two different trailing edge shapes. The results from the cascade tests show that the flow behavior upstream of the trailing edge remains unchanged. The homogeneous values downstream show higher turning and higher losses for the cut-back blade, especially in the supersonic range. Additional tests were conducted with carbon dioxide ejection, in order to analyze the mixing process downstream of the cascade.

Kapteijn, C.; Amecke, J. [Deutsche Forschungsanstalt fuer Luft-und Raumfahrt e.V., Goettingen (Germany). Inst. fuer Stroemungsmechanik; Michelassi, V. [Univ. of Florence (Italy). Dept. of Energetics

1996-07-01

37

Aerodynamics and Performance Testing of the VAWT.  

National Technical Information Service (NTIS)

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

P. C. Klimas

1981-01-01

38

Computational fluid dynamics analysis of cyclist aerodynamics: performance of different turbulence-modelling and boundary-layer modelling approaches.  

PubMed

This study aims at assessing the accuracy of computational fluid dynamics (CFD) for applications in sports aerodynamics, for example for drag predictions of swimmers, cyclists or skiers, by evaluating the applied numerical modelling techniques by means of detailed validation experiments. In this study, a wind-tunnel experiment on a scale model of a cyclist (scale 1:2) is presented. Apart from three-component forces and moments, also high-resolution surface pressure measurements on the scale model's surface, i.e. at 115 locations, are performed to provide detailed information on the flow field. These data are used to compare the performance of different turbulence-modelling techniques, such as steady Reynolds-averaged Navier-Stokes (RANS), with several k-epsilon and k-omega turbulence models, and unsteady large-eddy simulation (LES), and also boundary-layer modelling techniques, namely wall functions and low-Reynolds number modelling (LRNM). The commercial CFD code Fluent 6.3 is used for the simulations. The RANS shear-stress transport (SST) k-omega model shows the best overall performance, followed by the more computationally expensive LES. Furthermore, LRNM is clearly preferred over wall functions to model the boundary layer. This study showed that there are more accurate alternatives for evaluating flow around bluff bodies with CFD than the standard k-epsilon model combined with wall functions, which is often used in CFD studies in sports. PMID:20488446

Defraeye, Thijs; Blocken, Bert; Koninckx, Erwin; Hespel, Peter; Carmeliet, Jan

2010-05-21

39

A simple extension of “An alternative approach to sea surface aerodynamic roughness” by Zhiqiu Gao, Qing Wang, and Shouping Wang  

NASA Astrophysics Data System (ADS)

Based on the data previously collected during the Humidity Exchange over the Sea Main Experiment (HEXMAX), the methods used to parameterize aerodynamic roughness (z0), friction velocity (u*), and the neutral drag coefficient (CDN) under moderate wind speed conditions originally proposed by Gao et al. (2006) were extended by using the nondimensional significant wave height (gHs/u*2 or gHs/U10N2) instead of wave age (cp/u* or cp/U10N), where g is the acceleration of gravity, Hs is the significant wave height, U10Nis the horizontal wind speed at 10-m height under the neutral atmospheric condition, andcp is the phase velocity of the peak wave spectrum. The results show (1) u* = 0.024U10N(gHs/U10N2)-1/4, (2) z0 = 10 × exp[-4.797(gHs/u*2)1/6] or z0 = 10 × exp[-16.613(gHs/U10N2)1/4], and (3) CDN = 0.007(gHs/u*2)-1/3 or CDN = 5.76 × 10-4(gHs/U10N2)-1/2. The present parameterization schemes were experimentally tested.

Gao, Zhiqiu; Wang, Linlin; Bi, Xueyan; Song, Qingtao; Gao, Yuchao

2012-08-01

40

Beginner's Guide to Aerodynamics  

NSDL National Science Digital Library

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

2007-12-07

41

Aerodynamic characteristics of the TARP (Toroidal Accelerator Rotor Platform) wind energy conversion system  

Microsoft Academic Search

Augmented wind energy conversion systems (WECS) are designed to increase the ambient wind velocity at the turbine blades. The Toroidal Accelerator Rotor Platform (TARP) is an augmenting structure for use with horizontal axis WECS. Its shape resembles that of a horizontally oriented wheel rim and is intended to be built into or retrofitted onto structures built for other purposes, which

R. E. Duffy; C. Jaran; C. Ungermann

1980-01-01

42

Theoretical and experimental study on the aerodynamic characteristics of a horizontal axis wind turbine  

Microsoft Academic Search

The aerodynamic performance characteristics of a horizontal axis wind turbine (HAWT) were investigated theoretically by an analysis involving a combination of momentum, energy and blade element theory by means of the strip element method, and experimentally by the use of a subscale demonstration model. In this study, two approaches involving combination analysis are made use of, namely, the thrust–torque and

Koki Kishinami; Hiroshi Taniguchi; Jun Suzuki; Hiroshi Ibano; Takashi Kazunou; Masato Turuhami

2005-01-01

43

Aerodynamics of runback ice accretions  

NASA Astrophysics Data System (ADS)

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

Whalen, Edward A.

44

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

45

Aerodynamics of Transport Aircraft Spoiler Solutions  

Microsoft Academic Search

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

U. JUNG; C. BREITSAMTER

46

Constrained optimization of aerodynamic shapes via minimization of total drag  

Microsoft Academic Search

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

S. Peigin; B. Epstein

2005-01-01

47

State of the art in wind turbine aerodynamics and aeroelasticity  

NASA Astrophysics Data System (ADS)

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

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

2006-06-01

48

Aerodynamics and performance testing of the VAWT  

NASA Astrophysics Data System (ADS)

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

Klimas, P. C.

49

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

50

The Dutch energy transition approach  

Microsoft Academic Search

The article describes the Dutch energy transition approach as an example of an industrial policy approach for sustainable\\u000a growth. It is a corporatist approach for innovation, enrolling business in processes of transitional change that should lead\\u000a to a more sustainable energy system. A broad portfolio of options is being supported. A portfolio of options is generated\\u000a in a bottom-up, forward

René Kemp

2010-01-01

51

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

52

Hybrid methods for inverse aerodynamic design  

Microsoft Academic Search

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

Ashok Gopalarathnam

1999-01-01

53

Aerodynamics of Parachutes.  

National Technical Information Service (NTIS)

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

D. J. Cockrell A. D. Young

1987-01-01

54

Aerodynamic Lifting Force.  

ERIC Educational Resources Information Center

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

Weltner, Klaus

1990-01-01

55

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

56

State of the art in wind turbine aerodynamics and aeroelasticity  

Microsoft Academic Search

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

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

2006-01-01

57

DOE's Effort to Reduce Truck Aerodynamic Drag-Joint Experiments and Computations Lead to Smart Design  

SciTech Connect

At 70 miles per hour, overcoming aerodynamic drag represents about 65% of the total energy expenditure for a typical heavy truck vehicle. The goal of this US Department of Energy supported consortium is to establish a clear understanding of the drag producing flow phenomena. This is being accomplished through joint experiments and computations, leading to the 'smart' design of drag reducing devices. This paper will describe our objective and approach, provide an overview of our efforts and accomplishments, and discuss our future direction.

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

2004-06-17

58

Wind turbine aerodynamics research needs assessment  

NASA Astrophysics Data System (ADS)

A prioritized list is developed for wind turbine aerodynamic research needs and opportunities which could be used by the Department of Energy program management team in detailing the DOE Five-Year Wind Turbine Research Plan. The focus of the Assessment was the basic science of aerodynamics as applied to wind turbines, including all relevant phenomena, such as turbulence, dynamic stall, three-dimensional effects, viscosity, wake geometry, and others which influence aerodynamic understanding and design. The study was restricted to wind turbines that provide electrical energy compatible with the utility grid, and included both horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT). Also, no economic constraints were imposed on the design concepts or recommendations since the focus of the investigation was purely scientific.

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

1986-01-01

59

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

60

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

61

Freight Wing Trailer Aerodynamics  

Microsoft Academic Search

Freight Wing Incorporated utilized the opportunity presented by this DOE category one Inventions and Innovations grant to successfully research, develop, test, patent, market, and sell innovative fuel and emissions saving aerodynamic attachments for the trucking industry. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck's fuel consumption. However, significant design

Sean Graham; Patrick Bigatel

2004-01-01

62

Aerodynamics of stretched flames  

Microsoft Academic Search

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

Chung-Jen Sun

1998-01-01

63

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

64

Aerodynamics of high-speed railway train  

Microsoft Academic Search

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

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

2002-01-01

65

Study of the Aerodynamic Interference Effects during Aerial Refueling.  

National Technical Information Service (NTIS)

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

E. H. Hoganson

1983-01-01

66

Aerodynamics problems of space probes in comet atmosphere  

Microsoft Academic Search

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

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

1985-01-01

67

Utility of Radiometric–aerodynamic Temperature Relations for Heat Flux Estimation  

Microsoft Academic Search

In many land-surface models using bulk transfer (one-source) approaches, the application of radiometric surface temperature\\u000a observations in energy flux computations has given mixed results. This is due in part to the non-unique relationship between\\u000a the so-called aerodynamic temperature, which relates to the efficiency of heat exchange between the land surface and overlying\\u000a atmosphere, and a surface temperature measurement from a

William P. Kustas; Martha C. Anderson; John M. Norman; Fuqin Li

2007-01-01

68

HYSHOT-2 Aerodynamics  

NASA Astrophysics Data System (ADS)

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

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

2005-02-01

69

Applied computational aerodynamics  

Microsoft Academic Search

The present volume discusses the original development of the panel method, the mapping solutions and singularity distributions of linear potential schemes, the capabilities of full-potential, Euler, and Navier-Stokes schemes, the use of the grid-generation methodology in applied aerodynamics, subsonic airfoil design, inverse airfoil design for transonic applications, the divergent trailing-edge airfoil innovation in CFD, Euler and potential computational results for

Henne

1990-01-01

70

Hybrid methods for inverse aerodynamic design  

NASA Astrophysics Data System (ADS)

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

Gopalarathnam, Ashok

71

Aerodynamics: The Mathematical Implications  

NSDL National Science Digital Library

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

Smikle, Hermine E.

2000-03-11

72

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

73

Aerodynamics of runback ice accretions  

Microsoft Academic Search

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

Edward A. Whalen

2007-01-01

74

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

75

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

76

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.

77

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

Microsoft Academic Search

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

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

2000-01-01

78

DOE Project on Heavy Vehicle Aerodynamic Drag  

Microsoft Academic Search

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

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

2007-01-01

79

Aerodynamic characteristics of the TARP (Toroidal Accelerator Rotor Platform) wind energy conversion system. Final report, 1978-1979  

Microsoft Academic Search

Augmented wind energy conversion systems are designed to increase the ambient wind velocity at the turbine blades. The Toroidal Accelerator Rotor Platform (TARP) is an innovative, augmenting structure for use with horizontal axis WECS. Its shape resembles that of a horizontally-oriented wheel rim and is intended to be built into or retrofitted onto structures built for other purposes, which could

R. E. Duffy; C. Jaran; C. Ungermann

1980-01-01

80

Projectiles and aerodynamic forces  

NASA Astrophysics Data System (ADS)

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

Armstrong, H. L.

1984-09-01

81

Certain Problems of Experimental Aerodynamics.  

National Technical Information Service (NTIS)

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

S. M. Gorlin

1975-01-01

82

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

83

The Aerodynamics of Bird Flight  

NASA Astrophysics Data System (ADS)

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

Spedding, Geoffrey

2002-11-01

84

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

Microsoft Academic Search

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

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

1999-01-01

85

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

Microsoft Academic Search

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

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

2004-01-01

86

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

Microsoft Academic Search

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

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

1999-01-01

87

Impulse-Based Dynamic Simulation of Articulated Rigid Bodies with Aerodynamics  

Microsoft Academic Search

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

Chia-Da Lee; Li-Chen Fu

2006-01-01

88

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

Microsoft Academic Search

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

Christian Masson; Christophe Sibuet Watters; École de Technologie Supérieure

89

Aerodynamics of Wiffle Balls  

NASA Astrophysics Data System (ADS)

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

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

2003-11-01

90

An energy approach to crack closure  

Microsoft Academic Search

Crack closure is analyzed using an energy approach whereby it is shown that crack closure does not completely shield the input mechanical energy to the crack tip at a load below the crack opening load Pop if the compliance below Pop is non-zero. An equivalent shielding stress intensity range is defined by the energy release rate against crack closure. From

X. J. Wu

1995-01-01

91

Observational approaches to understanding dark energy  

Microsoft Academic Search

Illuminating the nature of dark energy is one of the most important challenges in cosmology today. In this review I discuss several promising observational approaches to understanding dark energy, in the context of the recommendations by the U.S. Dark Energy Task Force and the ESA-ESO Working Group on Fundamental Cosmology.

Yun Wang; Homer L. Dodge; W. Brooks

2007-01-01

92

Approaches to Sustainable Energy Consumption Patterns  

Microsoft Academic Search

Unsustainable consumption mostly refers to energy resources and materials’ utilization, fostered by human activity. Therefore,\\u000a energy consumption represents a major challenge when approaching sustainable development issues. Despite many environmental\\u000a strategies relying on improvements in energy and material efficiency, the World’s energy demand is likely to increase in line\\u000a with its population. In addition, cultural patterns of human activities are closely

Damjan Krajnc; Rebeka Lukman; Peter Glavic

93

Low Dimensional Modeling And Computational Analysis of Dragonfly Wing Aerodynamics  

NASA Astrophysics Data System (ADS)

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

Ren, Yan; Wan, Hui; Dong, Haibo

2011-11-01

94

An Approximate Analysis of Wing Unsteady Aerodynamics.  

National Technical Information Service (NTIS)

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

W. R. Wells

1979-01-01

95

Aerodynamic Simulation of Ice Accretion on Airfoils.  

National Technical Information Service (NTIS)

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

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

2011-01-01

96

Identification of Parameters and Model Structure for Missile Aerodynamics  

Microsoft Academic Search

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

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

1985-01-01

97

Proper Orthogonal Decomposition Extensions For Parametric Applications in Transonic Aerodynamics  

Microsoft Academic Search

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

T. Bui-Thanh; M. Damodarany

98

Review of CFD for wind-turbine wake aerodynamics  

Microsoft Academic Search

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

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

2010-01-01

99

Aerodynamic Characteristics of NACA4402 in Low Reynolds Number Flows  

Microsoft Academic Search

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

Ryoji Takaki

2006-01-01

100

Aerodynamic performance of thin wings at low Reynolds numbers  

Microsoft Academic Search

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

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

2007-01-01

101

Introduction to generalized functions with applications in aerodynamics and aeroacoustics  

Microsoft Academic Search

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

F. Farassat

1994-01-01

102

Unsteady aerodynamics modeling for flight dynamics application  

NASA Astrophysics Data System (ADS)

In view of engineering application, it is practicable to decompose the aerodynamics into three components: the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration, the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch, yaw, roll, and coupled yawroll large-amplitude oscillations. The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics, respectively. The results show that: (1) unsteady aerodynamics has no effect upon the existence of trim points, but affects their stability; (2) unsteady aerodynamics has great effects upon the existence, stability, and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously. Furthermore, the dynamic responses of the aircraft to elevator deflections are inspected. It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft. Finally, the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.

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

2012-02-01

103

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

104

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

105

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

106

Rotary wing aerodynamically generated noise  

Microsoft Academic Search

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

F. J. Schmitz; H. A. Morse

1982-01-01

107

Rotor/Body Aerodynamic Interactions.  

National Technical Information Service (NTIS)

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

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

1983-01-01

108

ENPEP: An integrated approach to energy planning  

SciTech Connect

Many models have been developed to analyze various aspects of the energy system. The Energy and Power Evaluation Program (ENPEP) is a set of microcomputer-based energy planning tools that are designed to provide an integrated analysis capability. ENPEP begins with a macroeconomic analysis, develops an energy demand forecast based on this analysis, carries out an integrated supply/demand analysis for the entire energy system, evaluates the electric system component of the energy system in detail, and determines the impacts of alternative configurations. This approach is an enhancement of existing techniques in that it places emphasis on looking at the electric system as an integral part of the entire energy supply system. Also, it explicitly considers the impacts the power system has on the rest of the energy system and on the economy as a whole.

Hamilton, B.P.; Cirillo, R.R.; Buehring, W.A.

1992-01-01

109

ENPEP: An integrated approach to energy planning  

SciTech Connect

Many models have been developed to analyze various aspects of the energy system. The Energy and Power Evaluation Program (ENPEP) is a set of microcomputer-based energy planning tools that are designed to provide an integrated analysis capability. ENPEP begins with a macroeconomic analysis, develops an energy demand forecast based on this analysis, carries out an integrated supply/demand analysis for the entire energy system, evaluates the electric system component of the energy system in detail, and determines the impacts of alternative configurations. This approach is an enhancement of existing techniques in that it places emphasis on looking at the electric system as an integral part of the entire energy supply system. Also, it explicitly considers the impacts the power system has on the rest of the energy system and on the economy as a whole.

Hamilton, B.P.; Cirillo, R.R.; Buehring, W.A.

1992-09-01

110

Aerodynamic and aeroelastic analysis of bundled cables by numerical simulation  

Microsoft Academic Search

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

A. L. Braun; A. M. Awruch

2005-01-01

111

Aerodynamic Optimization of a Solar - Bio Diesel Hybrid Vehicle  

Microsoft Academic Search

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

Neal A. Allgood

112

Measurement technology for micro-scale aerodynamics  

NASA Astrophysics Data System (ADS)

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

Martin, Michael James

113

Improving the efficiency of aerodynamic shape optimization  

NASA Astrophysics Data System (ADS)

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

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

1994-01-01

114

Multiprocessing on supercomputers for computational aerodynamics  

SciTech Connect

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

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

1991-01-01

115

Modified PROMETHEE approach for assessing energy technologies  

Microsoft Academic Search

Purpose – The purpose of this paper is to elaborate a multi-criteria methodology for the performance assessment of energy supply technologies, which also takes into account the dynamics of technological change. Design\\/methodology\\/approach – The approach chosen is based on the multi-criteria outranking methodology Preference Ranking Organisation METHod for Enrichment Evaluations (PROMETHEE), which is linked to the concept of technology's life

Julia Oberschmidt; Jutta Geldermann; Jens Ludwig; Meike Schmehl

2010-01-01

116

Improved Aerodynamic Influence Coefficients for Dynamic Aeroelastic Analyses  

NASA Astrophysics Data System (ADS)

Currently at Bombardier Aerospace, aeroelastic analyses are performed using the Doublet Lattice Method (DLM) incorporated in the NASTRAN solver. This method proves to be very reliable and fast in preliminary design stages where wind tunnel experimental results are often not available. Unfortunately, the geometric simplifications and limitations of the DLM, based on the lifting surfaces theory, reduce the ability of this method to give reliable results for all flow conditions, particularly in transonic flow. Therefore, a new method has been developed involving aerodynamic data from high-fidelity CFD codes which solve the Euler or Navier-Stokes equations. These new aerodynamic loads are transmitted to the NASTRAN aeroelastic module through improved aerodynamic influence coefficients (AIC). A cantilevered wing model is created from the Global Express structural model and a set of natural modes is calculated for a baseline configuration of the structure. The baseline mode shapes are then combined with an interpolation scheme to deform the 3-D CFD mesh necessary for Euler and Navier-Stokes analyses. An uncoupled approach is preferred to allow aerodynamic information from different CFD codes. Following the steady state CFD analyses, pressure differences ( DeltaCp), calculated between the deformed models and the original geometry, lead to aerodynamic loads which are transferred to the DLM model. A modal-based AIC method is applied to the aerodynamic matrices of NASTRAN based on a least-square approximation to evaluate aerodynamic loads of a different wing configuration which displays similar types of mode shapes. The methodology developed in this research creates weighting factors based on steady CFD analyses which have an equivalent reduced frequency of zero. These factors are applied to both the real and imaginary part of the aerodynamic matrices as well as all reduced frequencies used in the PK-Method which solves flutter problems. The modal-based AIC method's evaluation, performed with CFD data calculated by the DLM, is essential to find the natural modes which are most influential on the flutter solutions of the different configurations. Finally, Euler and Navier-Stokes results are used to obtain improved flutter solutions for a subsonic case at Mach 0.7 and dispositions are made to accomplish the same exercise for transonic speeds.

Gratton, Patrice

117

Modular Approach to Physics: Energy and Orbits  

NSDL National Science Digital Library

This resource is a simulation-based activity relating to gravitational potential energy (GPE) as a function of satellite-earth distance. Users may adjust the speed and initial position of a satellite in earth's gravitational field. Visible vectors and energy bar graphs help the learner determine how to apply the law of energy conservation to predict the speed of an object moving in earth's gravitational field. Included in the "Help" section is a detailed lesson plan with suggested supplementary activities. This item is part of a larger collection of simulation-based physics modules sponsored by the MAP project (Modular Approach to Physics).

2008-08-15

118

Analysis of aerodynamic pendulum oscillations  

NASA Astrophysics Data System (ADS)

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

Selyutskiy, Yury D.

2012-11-01

119

March 2000 Working Group Meeting on Heavy Vehicle Aerodynamic DragL Presentations and Summary of Comments and Conclusions  

Microsoft Academic Search

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory on March 16, 2000. The purpose of the meeting was to present technical details on the experimental and computational plans and approaches and provide an update on progress in the analysis of experimental results, model developments, simulations, and an investigation of an aerodynamic device.

R. McCallen; D. Flowers; T. Dunn; J. Owens; F. Browand; M. Hammache; A. Loenard; M. Brady; K. Salari; W. Rutledge; R. Scheckler; J. Ross; B. Storms; J. T. Heineck; T Arledge

2000-01-01

120

Global nonlinear aerodynamic model identification based on NARMAX model  

Microsoft Academic Search

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

Hui Xia; Xianyu Meng; Qingwei Chen

2010-01-01

121

Aerodynamics of a rolling airframe missile  

Microsoft Academic Search

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

L. E. Tisserand

1981-01-01

122

The efficiency of aerodynamic force production in Drosophila.  

PubMed

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

Lehmann, F O

2001-12-01

123

Computational approaches for RNA energy parameter estimation  

PubMed Central

Methods for efficient and accurate prediction of RNA structure are increasingly valuable, given the current rapid advances in understanding the diverse functions of RNA molecules in the cell. To enhance the accuracy of secondary structure predictions, we developed and refined optimization techniques for the estimation of energy parameters. We build on two previous approaches to RNA free-energy parameter estimation: (1) the Constraint Generation (CG) method, which iteratively generates constraints that enforce known structures to have energies lower than other structures for the same molecule; and (2) the Boltzmann Likelihood (BL) method, which infers a set of RNA free-energy parameters that maximize the conditional likelihood of a set of reference RNA structures. Here, we extend these approaches in two main ways: We propose (1) a max-margin extension of CG, and (2) a novel linear Gaussian Bayesian network that models feature relationships, which effectively makes use of sparse data by sharing statistical strength between parameters. We obtain significant improvements in the accuracy of RNA minimum free-energy pseudoknot-free secondary structure prediction when measured on a comprehensive set of 2518 RNA molecules with reference structures. Our parameters can be used in conjunction with software that predicts RNA secondary structures, RNA hybridization, or ensembles of structures. Our data, software, results, and parameter sets in various formats are freely available at http://www.cs.ubc.ca/labs/beta/Projects/RNA-Params.

Andronescu, Mirela; Condon, Anne; Hoos, Holger H.; Mathews, David H.; Murphy, Kevin P.

2010-01-01

124

Brief Introduction to the Soviet Central Research Institute of Aerodynamics.  

National Technical Information Service (NTIS)

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

Y. Yongziao Z. Ruqing

1985-01-01

125

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

126

Numerical simulation of aerodynamics and dynamics of wind turbines  

Microsoft Academic Search

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

Dmytro Redchyts

2007-01-01

127

Aerodynamic performance of thin wings at low Reynolds numbers  

Microsoft Academic Search

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

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

2009-01-01

128

Aerodynamics of a Cryogenic Semi-Tanker  

Microsoft Academic Search

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

Jason Ortega; Kambiz Salari

2009-01-01

129

Freight Wing Trailer Aerodynamics Final Technical Report  

Microsoft Academic Search

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

Sean Graham

2007-01-01

130

Recent progress in aerodynamic design optimization  

Microsoft Academic Search

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

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

1999-01-01

131

Membrane wing aerodynamics for micro air vehicles  

Microsoft Academic Search

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

Yongsheng Lian; Wei Shyy; Dragos Viieru; Baoning Zhang

2003-01-01

132

Aerodynamics and performance testing of the VAWT  

NASA Astrophysics Data System (ADS)

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

Klimas, P. C.

133

Aerodynamic tests of Darrieus wind turbine blades  

Microsoft Academic Search

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

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

1983-01-01

134

Aerodynamic flow visualization in the ONERA facilities  

Microsoft Academic Search

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

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

1977-01-01

135

Aerodynamics for the Mars Phoenix Entry Capsule.  

National Technical Information Service (NTIS)

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

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

2008-01-01

136

Aerodynamics and performance testing of the VAWT  

Microsoft Academic Search

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

P. C. Klimas

1981-01-01

137

Summary Analysis of the Gemini Entry Aerodynamics.  

National Technical Information Service (NTIS)

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

A. M. Whitnah D. B. Howes

1972-01-01

138

Cricket Ball Aerodynamics: Myth Versus Science.  

National Technical Information Service (NTIS)

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

R. D. Mehta

2000-01-01

139

Aerodynamic Simulation of Runback Ice Accretion.  

National Technical Information Service (NTIS)

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

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

2009-01-01

140

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

141

Aerodynamic Noise: a Critical Survey  

NASA Astrophysics Data System (ADS)

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

Talotte, C.

2000-03-01

142

A Kinematical Approach to Dark Energy Studies  

SciTech Connect

We present and employ a new kinematical approach to cosmological ''dark energy'' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q{sub 0} and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all {Lambda}CDM models have j(t) = 1 (constant), which facilitates simple tests for departures from the {Lambda}CDM paradigm. Applying our model to the three best available sets of redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for a late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t) = j, we measure q{sub 0} = -0.81 {+-} 0.14 and j = 2.16{sub -0.75}{sup +0.81}, results that are consistent with {Lambda}CDM at about the 1{sigma} confidence level. A standard ''dynamical'' analysis of the same data, employing the Friedmann equations and modeling the dark energy as a fluid with an equation of state parameter, w (constant), gives {Omega}{sub m} = 0.306{sub -0.040}{sup +0.042} and w = -1.15{sub -0.18}{sup +0.14}, also consistent with {Lambda}CDM at about the 1{sigma} level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible. Our results provide further interesting support for the concordance {Lambda}CDM paradigm.

Rapetti, David; Allen, Steven W.; Amin, Mustafa A.; Blandford, Roger D.; /KIPAC, Menlo Park

2006-06-06

143

Aerodynamic Characteristics of NACA4402 in Low Reynolds Number Flows  

NASA Astrophysics Data System (ADS)

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

Takaki, Ryoji

144

Analysis and Comparison of Several Methods for Computing Aerodynamic Compressibility and Interference Effects up to Critical Mach Numbers.  

National Technical Information Service (NTIS)

Analytical approaches are considered which might be used to improve and extend current aerodynamic analysis to include the compressibility effects up to and including critical mach numbers. The Rayleigh-Janzen solution is considered for both small disturb...

F. W. Martin J. Purvis J. E. Burkhalter B. D. Martin

1977-01-01

145

On cup anemometer rotor aerodynamics.  

PubMed

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

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

2012-05-10

146

On Cup Anemometer Rotor Aerodynamics  

PubMed Central

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

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

2012-01-01

147

Unsteady Aerodynamics of Insect Flight  

NASA Astrophysics Data System (ADS)

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

Wang, Z. Jane

2000-03-01

148

Analyzing mistuned multi-stage turbomachinery rotors with aerodynamic effects  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

149

Aerodynamics and interaction noise of streamlined bodies in nonuniform flows  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

150

Aerodynamic Design of AN Ariane 5 Reusable Booster STAGE*  

NASA Astrophysics Data System (ADS)

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

Eggers, Th.

2005-02-01

151

Aerodynamic Design Criteria for Class 8 Heavy Vehicles Trailer Base Devices to Attain Optimum Performance  

Microsoft Academic Search

Lawrence Livermore National Laboratory (LLNL) as part of its Department of Energy (DOE), Energy Efficiency and Renewable Energy (EERE), and Vehicle Technologies Program (VTP) effort has investigated class 8 tractor-trailer aerodynamics for many years. This effort has identified many drag producing flow structures around the heavy vehicles and also has designed and tested many new active and passive drag reduction

K Salari; J Ortega

2010-01-01

152

Research on the stability of overload-control for aerodynamic missiles  

Microsoft Academic Search

The overload-control approach was developed and applied to aerodynamic missiles in order to solve the problem of nonminimum phase of the acceleration control. It controlled the overload and the angle acceleration, but it didn't control the attitude variables in order to acquire high maneuverability. Sliding mode control (SMC) was adopted in this approach to design a control law of the

Wenjin Gu; Hongchao Zhao; Yun'an Hu

2004-01-01

153

Aerodynamics of Power Plant Installation, Part I.  

National Technical Information Service (NTIS)

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

1965-01-01

154

Aerodynamic Interference Effects on Tilting Proprotor Aircraft.  

National Technical Information Service (NTIS)

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

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

1977-01-01

155

Aerodynamic Validation of Emerging Projectile Configurations.  

National Technical Information Service (NTIS)

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

S. W. Lun

2011-01-01

156

Aerodynamic and Gasdynamic Effects in Cosmogony.  

National Technical Information Service (NTIS)

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

S. J. Weidenschilling

2005-01-01

157

Projectile Aerodynamic Jump Due to Lateral Impulsives.  

National Technical Information Service (NTIS)

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

G. R. Cooper

2003-01-01

158

Experimental Facilities and Modelling for Rarefied Aerodynamics.  

National Technical Information Service (NTIS)

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

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

2011-01-01

159

Review of Aerodynamics for Wind Turbines  

NASA Astrophysics Data System (ADS)

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

Snel, Herman

2003-07-01

160

Steady Incompressible Variable Thickness Shear Layer Aerodynamics.  

National Technical Information Service (NTIS)

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

M. R. Chi

1976-01-01

161

Conformable M3 Microsystems for Aerodynamic Control.  

National Technical Information Service (NTIS)

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

H. Chih-Ming T. Yu-Chong

1998-01-01

162

Unstructured Mesh Algorithms for Aerodynamic Calculations.  

National Technical Information Service (NTIS)

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

D. J. Mavriplis

1992-01-01

163

Aerodynamics of Seeing on Large Transport Aircraft.  

National Technical Information Service (NTIS)

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

W. C. Rose

1986-01-01

164

Torso Experienced Aerodynamic Forces Experienced during Ejection.  

National Technical Information Service (NTIS)

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

A. J. Nestle

1981-01-01

165

Coupled Aerodynamic-Thermal-Structural (CATS) Analysis.  

National Technical Information Service (NTIS)

Coupled Aerodynamic-Thermal-Structural (CATS) Analysis is a focused effort within the Numerical Propulsion System Simulation (NPSS) program to streamline multidisciplinary analysis of aeropropulsion components and assemblies. Multidisciplinary analysis of...

1995-01-01

166

Unsteady Aerodynamics Experiment Phase V: Test Configuration and Available Data Campaigns  

SciTech Connect

The main objective of the Unsteady Aerodynamics Experiment is to provide information needed to quantify the full-scale, three-dimensional, unsteady aerodynamic behavior of horizontal-axis wind turbines (HAWTs). To accomplish this, an experimental wind turbine configured to meet specific research objectives was assembled and operated at the National Renewable Energy Laboratory (NREL). The turbine was instrumented to characterize rotating-blade aerodynamic performance, machine structural responses, and atmospheric inflow conditions. Comprehensive tests were conducted with the turbine operating in an outdoor field environment under diverse conditions. Resulting data are used to validate aerodynamic and structural dynamics models, which are an important part of wind turbine design and engineering codes. Improvements in these models are needed to better characterize aerodynamic response in both the steady-state post-stall and dynamic-stall regimes. Much of the effort in the first phase of the Unsteady Aerodynamics Experiment focused on developing required data acquisition systems. Complex instrumentation and equipment was needed to meet stringent data requirements while operating under the harsh environmental conditions of a wind turbine rotor. Once the data systems were developed, subsequent phases of experiments were then conducted to collect data for use in answering specific research questions. A description of the experiment configuration used during Phase V of the experiment is contained in this report.

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

2001-08-30

167

Numerical simulations for transonic aerodynamic flows  

Microsoft Academic Search

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

Yau Shu Wong; Hong Jiang

1991-01-01

168

Recent progress in aerodynamic design optimization  

NASA Astrophysics Data System (ADS)

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

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

1999-05-01

169

Aerodynamics of missiles with slotted fin configurations  

Microsoft Academic Search

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

G. L. Abate; G. L. Winchenbach

1991-01-01

170

Rudolf Hermann, wind tunnels and aerodynamics  

NASA Astrophysics Data System (ADS)

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

Lundquist, Charles A.; Coleman, Anne M.

2008-04-01

171

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

172

Atmospheric tests of trailing-edge aerodynamic devices  

SciTech Connect

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

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

1998-01-01

173

Aerodynamic Characteristics of Wing Profiles for Wind Generators  

NASA Astrophysics Data System (ADS)

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

Colidiuc, Alexandra; Suatean, Bogdan; Galetuse, Stelian

2011-09-01

174

Computational prediction of flow and aerodynamic characteristics for an elliptic airfoil at low Reynolds number  

NASA Astrophysics Data System (ADS)

Lifting surfaces of unmanned aerial vehicles (UAV) are often operated in low Reynolds number (Re) ranges, wherein the transition of boundary layer from laminar-to-turbulent plays a more significant role than in high-Re aerodynamics applications. This poses a challenge for traditional computational fluid dynamics (CFD) simulations, since typical modeling approaches assume either fully laminar or fully turbulent flow. In particular, the boundary layer state must be accurately predicted to successfully determine the separation behavior which significantly influences the aerodynamic characteristics of the airfoil. Reynolds-averaged Navier-Stokes (RANS) based CFD simulations of an elliptic airfoil are performed for time-varying angles of attack, and results are used to elucidate relevant flow physics and aerodynamic data for an elliptic airfoil under realistic operating conditions. Results are also used to evaluate the performance of several different RANS-based turbulence modeling approaches for this class of flowfield.

Chitta, Varun

175

The execution of wind energy projects 1986 - 1992 between China Aerodynamics Research and Development Centre (CARDC) and The Aeronautical Research Institute of Sweden (FFA)  

Microsoft Academic Search

The execution of the first phase agreement on wind energy projects, covering the period from 1986 to 1992, is summarized. The following are addressed: wind tunnel tests of a 2.2 m and 2.8 m diameter turbine, a 5.35 m turbine in stationary yaw operation, pressure measurements, wall interference correction, a 5.35 m diameter turbine under yaw control, visualization of the

He Dexin; Sven-Erik Thor

1993-01-01

176

Disaggregation of home energy display data using probabilistic approach  

Microsoft Academic Search

Home energy displays are emerging home energy management devices. Their energy saving potential is limited, because most display whole-home electricity consumption data. We propose a new approach to disaggregation electricity consumption by individual appliances and\\/or end uses that would enhance the effectiveness of home energy displays. The proposed method decomposes a system of appliance models into tuplets of appliances overlapping

Michael Zeifman

2012-01-01

177

Disaggregation of home energy display data using probabilistic approach  

Microsoft Academic Search

Home energy displays are emerging home energy management devices. However, their energy savings potential is limited, because most display whole-home electricity consumption data. We propose a new approach to disaggregation electricity consumption by individual appliances and\\/or end uses that would enhance the effectiveness of home energy displays.

Michael Zeifman; Kurt Roth

2012-01-01

178

Turbine disk cavity aerodynamics and heat transfer  

NASA Astrophysics Data System (ADS)

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

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

1992-07-01

179

Aerodynamic Flow Control using Distributed Active Bleed  

NASA Astrophysics Data System (ADS)

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

Kearney, John M.; Glezer, Ari

2010-11-01

180

Aerodynamic tests of Darrieus wind turbine blades  

SciTech Connect

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

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

1983-03-01

181

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

182

Modeling new approaches for electric energy efficiency  

SciTech Connect

To align utilities and consumers' interests, three incentive methods have emerged to foster efficiency: shared savings, bonus return on equity, and energy service company. A fourth incentive method, virtual power plant, is being proposed by Duke Energy. (author)

Munns, Diane

2008-03-15

183

High-speed aerodynamic design of space vehicle and required hypersonic wind tunnel facilities  

NASA Astrophysics Data System (ADS)

Problems associated with the aerodynamic design of space vehicles with emphasis of the role of hypersonic wind tunnel facilities in the development of the vehicle are considered. At first, to identify wind tunnel and computational fluid dynamics (CFD) requirements, operational environments are postulated for hypervelocity vehicles. Typical flight corridors are shown with the associated flow density: real gas effects, low density flow, and non-equilibrium flow. Based on an evaluation of these flight regimes and consideration of the operational requirements, the wind tunnel testing requirements for the aerodynamic design are examined. Then, the aerodynamic design logic and optimization techniques to develop and refine the configurations in a traditional phased approach based on the programmatic design of space vehicle are considered. Current design methodology for the determination of aerodynamic characteristics for designing the space vehicle, i.e., (1) ground test data, (2) numerical flow field solutions and (3) flight test data, are also discussed. Based on these considerations and by identifying capabilities and limits of experimental and computational methods, the role of a large conventional hypersonic wind tunnel and the high enthalpy tunnel and the interrelationship of the wind tunnels and CFD methods in actual aerodynamic design and analysis are discussed.

Sakakibara, Seizou; Hozumi, Kouichi; Soga, Kunio; Nomura, Shigeaki

184

14 CFR 23.371 - Gyroscopic and aerodynamic loads.  

Code of Federal Regulations, 2013 CFR

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

2013-01-01

185

Mathematical Modeling of the Aerodynamic Characteristics in Flight Dynamics.  

National Technical Information Service (NTIS)

Basic concepts involved in the mathematical modeling of the aerodynamic response of an aircraft to arbitrary maneuvers are reviewed. The original formulation of an aerodynamic response in terms of nonlinear functionals is shown to be compatible with a der...

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

1984-01-01

186

Static Aerodynamics of the Mars Exploration Rover Entry Capsule.  

National Technical Information Service (NTIS)

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

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

2005-01-01

187

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

National Technical Information Service (NTIS)

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

M. V. Ol

2010-01-01

188

Research of the Rotational Effects on the Aerodynamics Characteristics of Horizontal Axis Wind Turbine  

Microsoft Academic Search

The flow Held of the NREL phase VI horizontal axis wind turbine has been modeled with a full 3-D steady\\/unsteady RANS approach. In the investigations a full Navier Stokes code FLUENT is used instead of engineering models. The calculations are compared with the measurements of the Unsteady aerodynamic experiment at the NASA Ames wind tunnel at wind speeds between 8

Rui Yang; Ren-Nian Li

2009-01-01

189

Adaptive Compensation of Aerodynamic Effects during Takeoff and Landing Manoeuvres for a Scale Model Autonomous Helicopter  

Microsoft Academic Search

Control of a scale model autonomous helicopter during takeoff and landing manoeuvres has proved to be an extremely difficult problem. This is a consequence of the slowly time-varying and environment dependent nature of the aerodynamic forces encountered along with the high sensitivity of the helicopter to collective pitch changes during these manoeuvres. In this paper we propose a novel approach

R. Mahony; T. Hamel

2001-01-01

190

Numerical simulations for transonic aerodynamic flows  

NASA Astrophysics Data System (ADS)

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

Wong, Yau Shu; Jiang, Hong

1991-04-01

191

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

NASA Astrophysics Data System (ADS)

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

Rinehart, Christopher; McMichael, James; Glezer, Ari

2002-11-01

192

Energy-efficient Housing Design. A combined approach  

Microsoft Academic Search

Energy-efficient Housing Design explains how to combine passive solar, superinsulation, and earth-shelter techniques to create the most energy-efficient, cost-effective housing designs. It addresses the concerns of architects, planners, contractors, developers, and homeowners, providing layouts for suburban tract housing and construction plans and details, as well as cost and performance analyses. Contents: Current approaches to Energy-efficient Design. Superinsulation Methods. Combining Approaches.

1985-01-01

193

INTEGRATED DESIGN OF ALTERNATIVE ENERGY OPTIONS - A MULTICRITERIA APPROACH  

Microsoft Academic Search

Energy planning has come a long way during the 20th century from an intuitive approach to a full-scale discipline, incorporating technological and economic dimensions. The latter include both the micro- and the macro- level, whereas the technological framework covers energy, technology, thermodynamics and thermo-economic approaches. It is only during the last two decades that the environmental aspects of energy conversion

Heracles Polatidis; Dias Haralambopoulos

2005-01-01

194

Design, aerodynamics and autonomy of the DelFly.  

PubMed

One of the major challenges in robotics is to develop a fly-like robot that can autonomously fly around in unknown environments. In this paper, we discuss the current state of the DelFly project, in which we follow a top-down approach to ever smaller and more autonomous ornithopters. The presented findings concerning the design, aerodynamics and autonomy of the DelFly illustrate some of the properties of the top-down approach, which allows the identification and resolution of issues that also play a role at smaller scales. A parametric variation of the wing stiffener layout produced a 5% more power-efficient wing. An experimental aerodynamic investigation revealed that this could be associated with an improved stiffness of the wing, while further providing evidence of the vortex development during the flap cycle. The presented experiments resulted in an improvement in the generated lift, allowing the inclusion of a yaw rate gyro, pressure sensor and microcontroller onboard the DelFly. The autonomy of the DelFly is expanded by achieving (1) an improved turning logic to obtain better vision-based obstacle avoidance performance in environments with varying texture and (2) successful onboard height control based on the pressure sensor. PMID:22617112

de Croon, G C H E; Groen, M A; De Wagter, C; Remes, B; Ruijsink, R; van Oudheusden, B W

2012-05-22

195

Aerodynamics of flapping wings with fluttering trailing edges  

Microsoft Academic Search

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

Liang Zhao; Zheng Hu; Jesse Roll; Xinyan Deng

2010-01-01

196

A Study of Aerodynamics of Low Reynolds Number Flexible Airfoils  

Microsoft Academic Search

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

Jian Tang; Dragos Viieru; Wei Shyy

197

Preliminary Studies on Aerodynamic Control with Direct Current Discharge at Hypersonic Speed  

NASA Astrophysics Data System (ADS)

A new idea of an aerodynamic control device for hypersonic vehicles using plasma discharges is presented. The effect of DC plasma discharge on a hypersonic flow is examined with both experiments and CFD analyses. It is revealed that the surface pressure upstream of plasma area significantly increases, which would be preferable in realizing a new aerodynamic control devices. Such pressure rise is also observed in the result of analyses of the Navier-Stokes equations with energy addition that simulates the Joule heating of a plasma discharge. It is revealed that the pressure rise due to the existence of the plasma discharge can be qualitatively explained as an effect of Joule heating.

Watanabe, Yasumasa; Takama, Yoshiki; Imamura, Osamu; Watanuki, Tadaharu; Suzuki, Kojiro

198

Aerodynamic shape and structural topology design of helicopter rotor cross-sections using a genetic algorithm  

NASA Astrophysics Data System (ADS)

The Genetic Algorithm (GA) is a computational model of natural selection that has useful applications in engineering design problems. Unlike traditional optimization methods, the GA does not require an initial starting point and provides a global search. This makes the GA well-suited to complex problems, such as the design of helicopter rotor blades. Previous efforts demonstrated that a GA can be used for aerodynamic shape design or beam cross-section topology design. The combination of the two concerns has not previously been fully addressed. A multidisciplinary approach combining structural and aerodynamic concerns for optimal topology design of rotor blades provides potential benefit to the rotorcraft design process. This research combines the aerodynamic shape and structural topology into a single problem statement, with the intent of discovering non-traditional rotor blade cross-section forms. The resulting problem is difficult to approach using traditional methods, so a GA is used to generate solutions to the problem. Designs generated with this approach could be further refined to obtain practical designs with improved performance in terms of aerodynamic and/or structural considerations.

Fanjoy, David William

2001-12-01

199

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

200

Aerodynamic drag in cycling: methods of assessment.  

PubMed

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

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

2011-09-01

201

Macro aerodynamic devices controlled by micro systems  

Microsoft Academic Search

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

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

1997-01-01

202

COMPUTER ANALYSIS OF INDUSTRIAL BATCH DRYER AERODYNAMICS  

Microsoft Academic Search

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

C. T. Kiranoudis; N. C. Markatos

1998-01-01

203

Aerodynamic noise prediction using grey model  

Microsoft Academic Search

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

Long Shuangli; Nie Hong; Li Lei; Xu Xin

2010-01-01

204

Containerless processing of ceramics by aerodynamic levitation  

Microsoft Academic Search

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

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

1996-01-01

205

Aerodynamics of a cycling team in a time trial: does the cyclist at the front benefit?  

Microsoft Academic Search

When seasonal journeys take place in nature, birds and fishes migrate in groups. This provides them not only with security but also a considerable saving of energy. The power they need to travel requires overcoming aerodynamic or hydrodynamic drag forces, which can be substantially reduced when the group travels in an optimal arrangement. Also in this area, humans imitate nature,

A. Íñiguez-de-la Torre; J. Íñiguez

2009-01-01

206

Aerodynamics of a Cycling Team in a Time Trial: Does the Cyclist at the Front Benefit?  

ERIC Educational Resources Information Center

|When seasonal journeys take place in nature, birds and fishes migrate in groups. This provides them not only with security but also a considerable saving of energy. The power they need to travel requires overcoming aerodynamic or hydrodynamic drag forces, which can be substantially reduced when the group travels in an optimal arrangement. Also in…

Iniguez-de-la Torre, A.; Iniguez, J.

2009-01-01

207

Recent darrieus Vertical-Axis Wind Turbine aerodynamical experiments at Sandia National Laboratories  

NASA Astrophysics Data System (ADS)

The aerodynamics of airfoils operating in the vertical axis wind turbine (VAWT) environment were examined. The experiments are intended to reduce VAWT cost of energy an increase system reliability. The experiments include: (1) chordwise pressure surveys; (2) circumferential blade acceleration surveys; (3) effects of blade camber; (4) pitch and offset; (5) blade blowing; and (6) use of sections designed specifically for VAWT application.

Klimas, P. C.

208

Recent Darrieus vertical axis wind turbine aerodynamical experiments at Sandia National Laboratories  

NASA Astrophysics Data System (ADS)

Experiments contributing to the understanding of the aerodynamics of airfoils operating in the vertical axis wind turbine (VAWT) environment are described. These experiments are ultimately intended to reduce VAWT cost of energy and increase system reliability. They include chordwise pressure surveys, circumferential blade acceleration surveys, effects of blade camber, pitch and offset, blade blowing, and use of sections designed specifically for VAWT application.

Klimas, P. C.

1981-05-01

209

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

210

Recent Darrieus vertical-axis wind turbine aerodynamical experiments at Sandia National Laboratories  

SciTech Connect

Experiments contributing to the understanding of the aerodynamics of airfoils operating in the vertical axis wind turbine (VAWT) environment are described. These experiments are ultimately intended to reduce VAWT cost of energy and increase system reliability. They include chordwise pressure surveys, circumferential blade acceleration surveys, effects of blade camber, pitch and offset, blade blowing, and use of sections designed specifically for VAWT application.

Klimas, P.C.

1981-01-01

211

Aerodynamics of a Cycling Team in a Time Trial: Does the Cyclist at the Front Benefit?  

ERIC Educational Resources Information Center

When seasonal journeys take place in nature, birds and fishes migrate in groups. This provides them not only with security but also a considerable saving of energy. The power they need to travel requires overcoming aerodynamic or hydrodynamic drag forces, which can be substantially reduced when the group travels in an optimal arrangement. Also in…

Iniguez-de-la Torre, A.; Iniguez, J.

2009-01-01

212

On Löwdin's projection technique and the energy-corrected approaches  

NASA Astrophysics Data System (ADS)

Recently, a new energy correction to standard approaches of the coupled-cluster (CC) method has been proposed, namely the so-called (complete) renormalized CC method [K. Kowalski and P. Piecuch, J. Chem. Phys. 113, 5644 (2000) and references therein], as well as the energy-corrected CCSD approach [X. Li and J. Paldus, J. Chem. Phys. 117, 1941 (2002) and references therein], which are based on the method of moments of the CC method of Kowalski and Piecuch [Computational Chemistry: Reviews of Current Trends (World Scientific, Singapore, 2000), Vol. 5, p. 1]. These methods provide an efficient and noniterative, and thus less demanding, approach than do the iterative approaches and avoid, e.g., the fallacies of the standard CCSD(T) method. We show how this type of energy corrections may be related to Löwdin's projection and bracketing techniques and also to a standard extrapolation scheme which is applied here to the results of the new energy corrections.

Meißner, Holger

2003-08-01

213

Energy awareness: a comprehensive approach. Final report  

SciTech Connect

The University of Wisconsin-Superior conducted an intradisciplinary Faculty Development Project during the 1982-1983 year. Twenty-three teachers including 5 women and 18 men from that many schools participated in the project. They attended a 2-week on-campus summer workshop and many also attended the follow-up meeting. The latter was to finalize the plans for introducing Energy Education in participants' high schools. Participants' summer activities consisted of: (1) socials and group dynamics - 6 hrs; (2) laboratory training - 24 hrs; (3) classroom instruction - 18 hrs; (4) field trips - 16 hrs; (5) viewing films in energy and related topics plus listening to the guest speakers - 6 hrs; (6) group discussions for the development of teaching materials in Energy Education - 6 hrs; and (7) taking written examinations - 4 hrs. Those who successfully completed these activities earned 3 quarter graduate credits in a science discipline of choice. Energy Resource Center was created to provide additional information in energy and related areas. The Center displayed multiple copies of over 100 different publications which allowed teachers to compile the materials of their choices and usefulness. In addition, numerous handouts were given during the laboratory and classroom sessions.

Vaishnav, D.D.

1984-02-29

214

Measuring energy efficiency in economics: Shadow value approach  

NASA Astrophysics Data System (ADS)

For decades, academic scholars and policy makers have commonly applied a simple average measure, energy intensity, for studying energy efficiency. In contrast, we introduce a distinctive marginal measure called energy shadow value (SV) for modeling energy efficiency drawn on economic theory. This thesis demonstrates energy SV advantages, conceptually and empirically, over the average measure recognizing marginal technical energy efficiency and unveiling allocative energy efficiency (energy SV to energy price). Using a dual profit function, the study illustrates how treating energy as quasi-fixed factor called quasi-fixed approach offers modeling advantages and is appropriate in developing an explicit model for energy efficiency. We address fallacies and misleading results using average measure and demonstrate energy SV advantage in inter- and intra-country energy efficiency comparison. Energy efficiency dynamics and determination of efficient allocation of energy use are shown through factors impacting energy SV: capital, technology, and environmental obligations. To validate the energy SV, we applied a dual restricted cost model using KLEM dataset for the 35 US sectors stretching from 1958 to 2000 and selected a sample of the four sectors. Following the empirical results, predicted wedges between energy price and the SV growth indicate a misallocation of energy use in stone, clay and glass (SCG) and communications (Com) sectors with more evidence in the SCG compared to the Com sector, showing overshoot in energy use relative to optimal paths and cost increases from sub-optimal energy use. The results show that energy productivity is a measure of technical efficiency and is void of information on the economic efficiency of energy use. Decomposing energy SV reveals that energy, capital and technology played key roles in energy SV increases helping to consider and analyze policy implications of energy efficiency improvement. Applying the marginal measure, we also contributed to energy efficiency convergence analysis employing the delta-convergence and unconditional & conditional beta-convergence concepts, investigating economic energy efficiency differences across the four US sectors using panel data models. The results show that, in terms of technical and allocative energy efficiency, the energy-intensive sectors, SCG and textile mill products, tend to catch the energy extensive sectors, the Com and furniture & fixtures, being conditional on sector-specific characteristics. Conditional convergence results indicate that technology, capital and energy are crucial factors in determining energy efficiency differences across the US sectors, implying that environmental or energy policies, and technological changes should be industry specific across the US sectors. The main finding is that the marginal value measure conveys information on both technical and allocative energy efficiency and accounts for all costs and benefits of energy consumption including environmental and externality costs.

Khademvatani, Asgar

215

Resistor Emulation Approach to Low-Power Energy Harvesting  

Microsoft Academic Search

This paper presents an approach and associated circuitry for harvesting near maximum output from low power sources in the 100 muW range for miniature wireless devices. A set of converter topologies and control approaches are presented together with detailed efficiency analysis and a design example for a buck-boost based energy harvesting converter using commercially available discrete circuitry. Experimental results are

Thurein S. Paing; Regan Zane

2006-01-01

216

A System Design Approach for Unattended Solar Energy Harvesting Supply  

Microsoft Academic Search

Remote devices, such as sensors and communications devices, require continuously available power. In many applications, conventional approaches are too expensive, too large, or unreliable. For short-term needs, primary batteries may be used. However, they do not scale up well for long-term installations. Instead, energy harvesting methods must be used. Here, a system design approach is introduced that results in a

Jonathan W. Kimball; Brian T. Kuhn; Robert S. Balog

2009-01-01

217

An unsteady aerodynamic formulation for efficient rotor tonal noise prediction  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

218

Numerical simulation of aerodynamics and dynamics of wind turbines  

NASA Astrophysics Data System (ADS)

Processes of aerodynamics and dynamics are described by incompressible Reynolds averaged Navier-Stokes equations and the equation of wind turbine rotation. Three one-equation turbulence models SA, SARC and SALSA are used. Incompressible Navier-Stokes equations were solved in time-accurate manner using the method of pseudocompressibility and Rogers-Kwak scheme. The finite-volume approach in generalized coordinates was used. Verification of the developed CFD algorithms and codes is carried out on the problems on flow around fixed and rotating cylinders. Comparison of turbulence models is given for a flow around the NACA 4412 airfoil. Instantaneous streamlines, vorticity fields and hysteresis of the unsteady aerodynamic characteristics are discussed for an oscillating NACA 0015 airfoil. It is shown that SALSA model demonstrates its advantages on massive flow separation and dynamic stall. Results of numerical simulation for wind turbine rotors with different geometrical characteristics and different number of blades are presented. Physical features of the flow near wind turbine blades, such as boundary layer separation and flow interactions between the blades are discussed.

Redchyts, Dmytro

2007-11-01

219

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

220

Symmetry energy within the BHF approach  

NASA Astrophysics Data System (ADS)

We analyze the correlations of the slope and curvature parameters of the symmetry energy with the neutron skin thickness of neutron-rich isotopes, and the crust-core transition density in neutron stars. Microscopic Brueckner-Hartree-Fock results are compared with those obtained with several Skyrme and relativistic mean field models. Our results confirm that there is an inverse correlation between the neutron skin thickness and the transition density.

Vidaña, Isaac; Providência, Constança; Polls, A.; Rios, Arnau

2012-02-01

221

October 1998 working group meeting on heavy vehicle aerodynamic drag: presentations and summary of comments and conclusions  

SciTech Connect

A Working Group 1Meeting on Heavy Vehicle Aerodynamic Drag was held at NASA Ames Research Center, Moffett Field, California on October 22, 1998. The purpose of the meeting was to present an overview of the computational and experimental approach for modeling the integrated tractor-trailer benchmark geometry called the Sandia IModel and to review NASA? s test plan for their experiments in the 7 ft x 10 ft wind tunnel. The present and projected funding situation was also discussed. Presentations were given by representatives from the Department of Energy (DOE) Office of Transportation Technology Office of Heavy Vehicle Technology (OHVT). Lawrence Livermore National Laboratory (LLNL), Sandia National Laboratories (SNL), and NASA Ames Research Center. This report contains the technical presentations (viewgraphs) delivered at the Meeting, briefly summarizes the comments and conclusions. and outlines the future action items.

Browand, F; Heineck, J T; Leonard, A; McBride, D; McCallen, R; Ross, J; Rutledge, W; Salari, K; Storms, B

1998-10-01

222

Performance of SMA-reinforced composites in an aerodynamic profile  

NASA Astrophysics Data System (ADS)

Within the European collaborative applied fundamental research project ADAPT, fundamentals of SMA-reinforced composites were evaluated and the specific manufacturing techniques for these composites developed and realised. The involved partners are listed at the end. To demonstrate applicability of these composites a realistically scaled aerodynamic profile of around 0.5m span by 0.5m root chord was designed, manufactured and assembled. The curved skins were manufactured as SMA composites with two layers of SMA-wires integrated into the layup of aramid fibre prepregs. All SMA wires were connected such that they can be operated as individual sets of wires and at low voltages, similar to the conditions for electrical energy generation in a real aircraft. The profile was then mounted on a vibration test rig and activated and excited by a shaker at its tip which allowed to test the dynamic performance of the profile under different external loading conditions with various internal actuation conditions through the SMA wires. The paper includes some background of the design and manufacturing of the aerodynamic profile and will discuss some of the results determined recently on the test rig. A view with regard to future wind tunnel testing will be given as well.

Simpson, John; Boller, Christian

2002-07-01

223

The problem with the “portfolio approach” in American energy policy  

Microsoft Academic Search

One predominant theme in American energy and electricity policy is the idea of a “portfolio approach,” or that society must\\u000a embrace an assortment of different energy technologies simultaneously. This article argues that such a strategy, in practice,\\u000a is (a) biased, since fossil fuel and nuclear technologies have been heavily favored; (b) opaque, obscuring the different full\\u000a social costs of energy

Benjamin K. Sovacool

2008-01-01

224

Analytical approach to backscattering of low-energy electrons  

NASA Astrophysics Data System (ADS)

The backscattered flux and energy of electrons when a monoenergetic electron is incident in a gas at any pitch angle are calculated using an approach based on spatial yield spectra. The four-dimensional yield spectrum function is defined and the equations for calculating the backscattered flux and energy are derived. The calculated backscattered flux and energy are compared to the data of Mantas and Walker (1976) and the data correlate well.

Haider, S. A.; Singhal, R. P.

1986-12-01

225

Energy-efficient Housing Design. A combined approach  

SciTech Connect

Energy-efficient Housing Design explains how to combine passive solar, superinsulation, and earth-shelter techniques to create the most energy-efficient, cost-effective housing designs. It addresses the concerns of architects, planners, contractors, developers, and homeowners, providing layouts for suburban tract housing and construction plans and details, as well as cost and performance analyses. Contents: Current approaches to Energy-efficient Design. Superinsulation Methods. Combining Approaches. Design Characteristics with the Combined Approach. Materials and Construction Methods. Wall and Roof Design. Windows and Window Protection. Passive Solar Storage Methods. Winter Heating Performance. The Passive Solar Storage System. Designing for Summer Cooling. Analyzing Cost-effectiveness. Construction Cost with Energy-efficient Design. The Balance Sheet. Site Planning. Landscaping the Lot. Subdivision-planning Methods. Streetscape and Landscape. Appendices.

Lane, J.

1985-01-01

226

Hydrodynamics and aerodynamics - Cross fertilisation in research and design  

NASA Astrophysics Data System (ADS)

Areas of intersection between theory and applications in hydrodynamics and aerodynamics are investigated. Fluid mechanics principles involve the minimization of drag and considers the energy exchange between a craft and its wake, which leads to boundary layer examinations. The effects of surface roughness and of turbulent boundary layers are applicable to both seagoing and airborne craft, as are flow separation and vortical flows. Boundary layer control and reenergizing of the boundary layer with redirected vortex energy are discussed. Vortex interaction studies are prominent in the design of offshore oil rig platforms, where orbital wave motion is equivalent to vortex occurrence, and interaction is modelled as flow over a cylinder. Descriptions are given of the design of foil-like shapes, wind-propelled commercial ships, and other applications are presented.

Pearcey, H. H.

1982-01-01

227

Aerodynamic Self Excitation of a Taut Elastic Ribbon  

NASA Astrophysics Data System (ADS)

The investigators analyzed, both theoretically and experimentally, the motion of a taut ribbon of elastic material in an air stream to show that the resulting standing-wave motion is a manifestation of self excitation. Self excitation is a phenomenon in which the oscillatory motion of the object extracts energy from a steady energy source. Such a ribbon simulates the motion of the human vocal folds as well as that of unstable bridge ``galloping,'' such as is famously exemplified in the Tacoma Narrows bridge collapse. The phenomenon discussed in this talk is also relevant to aerodynamic flutter and the ``quaking'' of leaves of trees in the breeze. Chief among the findings of this work is the origin of inharmonic modes of oscillation of a self excited ribbon.

Matteson, Sam; Lambert, David

2011-10-01

228

Performance of an aerodynamic particle separator  

SciTech Connect

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

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

1996-12-31

229

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

230

Aerodynamic interference between two Darrieus wind turbines  

SciTech Connect

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

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

1981-04-01

231

Aerodinamica da Turbina de Tipo Wells com Geometria Fixa e Variavel (Aerodynamics of the Wells-Type Turbine of Fixed and Variable Geometry).  

National Technical Information Service (NTIS)

The thesis presents a theoretical and experimental investigation concerning the aerodynamic performance of the Wells turbine, a self-rectifying axial-flow turbine suitable for energy extraction from reciprocating air flow, as encountered in the oscillatin...

L. M. de Carvalho Gato

1988-01-01

232

Aerodynamic design of winged space vehicle  

Microsoft Academic Search

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

Yoshifumi Inatani; Koichi Yonemoto

1988-01-01

233

Variable-Fidelity Aerodynamic Shape Optimization  

Microsoft Academic Search

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

Leifur Leifsson; Slawomir Koziel

234

Unsteady aerodynamics of fluttering and tumbling plates  

Microsoft Academic Search

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

U. P ESAVENTO; Z. J ANE W ANG

2005-01-01

235

Aerodynamic characteristics of flapping motion in hover  

Microsoft Academic Search

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

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

2008-01-01

236

CFD calculations of S809 aerodynamic characteristics  

Microsoft Academic Search

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

Walter P. Wolfe; Stuart S. Ochs

1997-01-01

237

Aeroelastic coupling of geometrically nonlinear structures and linear unsteady aerodynamics: Two formulations  

NASA Astrophysics Data System (ADS)

Two different time domain formulations of integrating commonly used frequency-domain unsteady aerodynamic models based on a modal approach with full order finite element models for structures with geometric nonlinearities are presented. Both approaches are tailored to flight vehicle configurations where geometric stiffness effects are important but where deformations are moderate, flow is attached, and linear unsteady aerodynamic modeling is adequate, such as low aspect ratio wings or joined-wing and strut-braced wings at small to moderate angles of attack. Results obtained using the two approaches are compared using both planar and non-planar wing configurations. Sub-critical and post-flutter speeds are considered. It is demonstrated that the two methods lead to the same steady solution for the sub-critical case after the transients subside. It is also shown that the two methods predict the amplitude and frequency of limit cycle oscillation (when present) with the same accuracy.

Demasi, L.; Livne, E.

2009-07-01

238

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

239

Computational Aerodynamics of Insects' Flapping Flight  

NASA Astrophysics Data System (ADS)

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

Yang, Kyung Dong; Kyung, Richard

2011-11-01

240

Aerodynamic Design Criteria for Class 8 Heavy Vehicles Trailer Base Devices to Attain Optimum Performance  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) as part of its Department of Energy (DOE), Energy Efficiency and Renewable Energy (EERE), and Vehicle Technologies Program (VTP) effort has investigated class 8 tractor-trailer aerodynamics for many years. This effort has identified many drag producing flow structures around the heavy vehicles and also has designed and tested many new active and passive drag reduction techniques and concepts for significant on the road fuel economy improvements. As part of this effort a database of experimental, computational, and conceptual design for aerodynamic drag reduction devices has been established. The objective of this report is to provide design guidance for trailer base devices to improve their aerodynamic performance. These devices are commonly referred to as boattails, base flaps, tail devices, and etc. The information provided here is based on past research and our most recent full-scale experimental investigations in collaboration with Navistar Inc. Additional supporting data from LLNL/Navistar wind tunnel, track test, and on the road test will be published soon. The trailer base devices can be identified by 4 flat panels that are attached to the rear edges of the trailer base to form a closed cavity. These devices have been engineered in many different forms such as, inflatable and non-inflatable, 3 and 4-sided, closed and open cavity, and etc. The following is an in-depth discussion with some recommendations, based on existing data and current research activities, of changes that could be made to these devices to improve their aerodynamic performance. There are 6 primary factors that could influence the aerodynamic performance of trailer base devices: (1) Deflection angle; (2) Boattail length; (3) Sealing of edges and corners; (4) 3 versus 4-sided, Position of the 4th plate; (5) Boattail vertical extension, Skirt - boattail transition; and (6) Closed versus open cavity.

Salari, K; Ortega, J

2010-12-13

241

A modeling approach to energy savings of flying Canada geese using computational fluid dynamics.  

PubMed

A flapping flight mechanism of the Canada goose (Branta canadensis) was estimated using a two-jointed arm model in unsteady aerodynamic performance to examine how much energy can be saved in migration. Computational fluid dynamics (CFD) was used to evaluate airflow fields around the wing and in the wake. From the distributions of velocity and pressure on the wing, it was found that about 15% of goose flight energy could be saved by drag reduction from changing the morphology of the wing. From the airflow field in the wake, it was found that a pair of three-dimensional spiral flapping advantage vortices (FAV) was alternately generated. We quantitatively deduced that the optimal depth (the distance along the flight path between birds) was around 4m from the wing tip of a goose ahead, and optimal wing tip spacing (WTS, the distance between wing tips of adjacent birds perpendicular to the flight path) ranged between 0 and -0.40m in the spanwise section. It was found that a goose behind can save about 16% of its energy by induced power from FAV in V-formation. The phase difference of flapping between the goose ahead and behind was estimated at around 90.7° to take full aerodynamic benefit caused by FAV. PMID:23261397

Maeng, Joo-Sung; Park, Jae-Hyung; Jang, Seong-Min; Han, Seog-Young

2012-12-19

242

Dynamical dark energy models dynamical system approach  

NASA Astrophysics Data System (ADS)

We study the Friedmann-Robertson-Walker model with dynamical dark energy modelled in terms of the equation of state p X = w X ( a( z)) ? X in which the coefficient w X is parameterized by the scale factor a or redshift z. We use methods of qualitative analysis of differential equations to investigate the space of all admissible solutions for all initial conditions on the two-dimensional phase plane. We show advantages of representing this dynamics as a motion of a particle in the one-dimensional potential V( a). One of the features of this reduction is the possibility of investigating how typical big rip singularities are in the future evolution of the model. The properties of potential function V can serve as a tool for qualitative classification of all evolution paths. Some important features like resolution of the acceleration problem can be simply visualized as domains on the phase plane. Then one is able to see how large is the class of solutions (labelled by the inset of the initial conditions) leading to the desired property.

Szyd?owski, Marek; Hrycyna, Orest

2006-01-01

243

Asymmetric demand for energy: A cointegration approach  

NASA Astrophysics Data System (ADS)

This paper uses time series data in a study of the demand for energy. One goal is to compare the results from the traditional autoregressive distributed lag (ADL) model to the error correction model (ECM) using cointegration. The second goal is to determine if the demand elasticity is asymmetric with respect to increasing and decreasing prices. This paper discusses three topics that are important to the use of time series data. The first topic is the presence and consequences unit roots which are common in time series data. The second topic is the identification of cointegrated variables and the third topic is a development of the ECM. This results in a model that can be used in either a single equation or multivariate system context and it will estimate both long run and short run elasticities. Asymmetry theory and its implications are studied along with an investigation into competing methods of creating the asymmetric variables. Simulations provided evidence that the use of dummy variables results in biased estimates and that the cumulative difference method of Wolffram/Houck gives valid estimates. The results of the empirical part of the paper show that the short run estimates of the ADL model are like those of the error correction model, but the cointegration method's long run estimates are better since they are known to be consistent and asymptotically unbiased. Tests for asymmetry do not support the theory of asymmetric long run price elasticities; however there is evidence to support the presence of asymmetric demand in the short run.

Maclean, Thomas Frank

1997-12-01

244

Four-stage computational technology with adaptive numerical methods for computational aerodynamics  

NASA Astrophysics Data System (ADS)

Computational aerodynamics is a key technology in aircraft design which is ahead of physical experiment and complements it. Of course all three components of computational modeling are actively developed: mathematical models of real aerodynamic processes, numerical algorithms, and high-performance computing. The most impressive progress has been made in the field of computing, though with a considerable complication of computer architecture. Numerical algorithms are developed more conservative. More precisely, they are offered and theoretically justified for more simple mathematical problems. Nevertheless, computational mathematics now has amassed a whole palette of numerical algorithms that can provide acceptable accuracy and interface between modern mathematical models in aerodynamics and high-performance computers. A significant step in this direction was the European Project ADIGMA whose positive experience will be used in International Project TRISTAM for further movement in the field of computational technologies for aerodynamics. This paper gives a general overview of objectives and approaches intended to use and a description of the recommended four-stage computer technology.

Shaydurov, V.; Liu, T.; Zheng, Z.

2012-10-01

245

Study of aerodynamic methods for improving truck fuel economy  

Microsoft Academic Search

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

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

1978-01-01

246

A study of aerodynamic methods for improving truck fuel economy  

Microsoft Academic Search

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

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

1978-01-01

247

Inverse aerodynamic design applications using the MGM hybrid formulation  

Microsoft Academic Search

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

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

2009-01-01

248

Economic evaluations of solar thermal energy systems using a levelized energy cost approach  

Microsoft Academic Search

This paper discusses a Levelized Energy Cost (LEC) approach to economic evaluations of solar thermal power plants. Levelized Energy Costs are life cycle costs that include a plant's capital cost, total operation and maintenance cost, taxes, interest, and return on investment. A LEC approach provides an economically correct treatment of these costs and allows an evaluation of alternative solar thermal

T. A. Williams; J. A. Dirks

1985-01-01

249

Application of strand meshes to complex aerodynamic flow fields  

NASA Astrophysics Data System (ADS)

We explore a new approach for viscous computational fluid dynamics calculations for external aerodynamics around geometrically complex bodies that incorporates nearly automatic mesh generation and efficient flow solution methods. A prismatic-like grid using "strands" is grown a short distance from the body surface to capture the viscous boundary layer, and adaptive Cartesian grids are used throughout the rest of the domain. The approach presents several advantages over established methods: nearly automatic grid generation from triangular or quadrilateral surface tessellations, very low memory overhead, automatic mesh adaptivity for time-dependent problems, and fast and efficient solvers from structured data in both the strand and Cartesian grids.The approach is evaluated for complex geometries and flow fields. We investigate the effects of strand length and strand vector smoothing to understand the effects on computed solutions. Results of three applications using the strand-adaptive Cartesian approach are given, including a NACA wing, isolated V-22 (TRAM) rotor in hover, and the DLR-F6 wing-body transport. The results from these cases show that the strand approach can successfully resolve near-body and off-body features as well as or better than established methods.

Katz, Aaron; Wissink, Andrew M.; Sankaran, Venkateswaran; Meakin, Robert L.; Chan, William M.

2011-07-01

250

Reference values and improvement of aerodynamic drag in professional cyclists.  

PubMed

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

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

2008-02-01

251

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

252

A multicriteria lifespan energy efficiency approach to intelligent building assessment  

Microsoft Academic Search

This paper presents a multicriteria decision-making model for lifespan energy efficiency assessment of intelligent buildings (IBs). The decision-making model called IBAssessor is developed using an analytic network process (ANP) method and a set of lifespan performance indicators for IBs selected by a new quantitative approach called energy–time consumption index (ETI). In order to improve the quality of decision-making, the authors

Zhen Chen; Derek Clements-Croome; Ju Hong; Heng Li; Qian Xu

2006-01-01

253

Experimental Investigation of Hypersonic Flow and Plasma Aerodynamic Actuation Interaction  

NASA Astrophysics Data System (ADS)

For hypersonic flow, it was found that the most effective plasma actuator is derived from an electromagnetic perturbation. An experimental study was performed between hypersonic flow and plasma aerodynamic actuation interaction in a hypersonic shock tunnel, in which a Mach number of 7 was reached. The plasma discharging characteristic was acquired in static flows. In a hypersonic flow, the flow field can affect the plasma discharging characteristics. DC discharging without magnetic force is unstable, and the discharge channel cannot be maintained. When there is a magnetic field, the energy consumption of the plasma source is approximately three to four times larger than that without a magnetic field, and at the same time plasma discharge can also affect the hypersonic flow field. Through schlieren pictures and pressure measurement, it was found that plasma discharging could induce shockwaves and change the total pressure and wall pressure of the flow field.

Sun, Quan; Cheng, Bangqin; Li, Yinghong; Cui, Wei; Yu, Yonggui; Jie, Junhun

2013-09-01

254

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

SciTech Connect

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California. Companion computer simulations are being performed by Sandia National Laboratories, Lawrence Livermore National Laboratory, and California Institute of Technology using state-of-the-art techniques, with the intention of implementing more complex methods in the future.

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

1999-04-01

255

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

SciTech Connect

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California. Companion computer simulations are being performed by Sandia National Laboratories, Lawrence Livermore National Laboratory, and California Institute of Technology using state-of-the-art techniques, with the intention of implementing more complex methods in the future.

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

1999-12-31

256

CFD based unsteady aerodynamic modeling for rotor aeroelastic analysis  

NASA Astrophysics Data System (ADS)

A Computational Fluid Dynamics (CFD) analysis is developed for 3-D rotor unsteady aerodynamic load prediction. It is then coupled to a rotor structural analysis for predicting aeroelastic blade response, airloads and vibration. The CFD analysis accounts for the elastic deformations using a dynamically deforming mesh system. All the rotor blades are assumed to be identical, therefore to reduce the computational complexity the CFD calculations are performed for a single blade. This accounts for the near wake flow field. But the far wake effects because of the trailed tip vortices from all the blades have to be included separately. This is achieved by the use of the field velocity approach, which is a method for modeling unsteady flows via apparent grid movement. In this method, the induced velocity field caused by the trailed vortex wake is included by modifying the grid time metrics. The CFD method developed is systematically validated for a range of problems starting from simple 2-D model problems to full scale forward flight cases. The CFD analysis shows significant improvements in airloads prediction compared to a table lookup based lifting-line analysis. The CFD analysis is then used to investigate the fundamental mechanisms of rotor vibration. It is found that both the normal forces and pitching moments are dominated by three dimensional aerodynamic effects. The curvature introduced by the blade elasticity appears to play a key role in the generation of the vibratory harmonics in airloads. The pitching moments near the blade tip (85% outboard) are significantly affected by transonic tip relief effects. The fundamental understanding of rotor vibrations gained from this study is then used to develop generic corrections for improving the accuracy of a lifting line analysis. Finally the CFD analysis developed is coupled with an advanced comprehensive rotor aeroelastic analysis. The coupling procedure is formulated in a way such that there is an exchange of information between the structural model and CFD model every rotor revolution. The coupled CFD/structure scheme is found to considerably improve the prediction of rotor vibratory airloads compared to the baseline rotor aeroelastic analysis which uses a lifting line based aerodynamic model.

Sitaraman, Jayanarayanan

257

Energy-guided learning approach to compressive FD-OCT.  

PubMed

High quality, large size volumetric imaging of biological tissue with optical coherence tomography (OCT) requires large number and high density of scans, which results in large data acquisition volume. This may lead to corruption of the data with motion artifacts related to natural motion of biological tissue, and could potentially cause conflicts with the maximum permissible exposure of biological tissue to optical radiation. Therefore, OCT can benefit greatly from different approaches to sparse or compressive sampling of the data where the signal is recovered from its sub-Nyquist measurements. In this paper, a new energy-guided compressive sensing approach is proposed for improving the quality of images acquired with Fourier domain OCT (FD-OCT) and reconstructed from sparse data sets. The proposed algorithm learns an optimized sampling probability density function based on the energy distribution of the training data set, which is then used for sparse sampling instead of the commonly used uniformly random sampling. It was demonstrated that the proposed energy-guided learning approach to compressive FD-OCT of retina images requires 45% fewer samples in comparison with the conventional uniform compressive sensing (CS) approach while achieving similar reconstruction performance. This novel approach to sparse sampling has the potential to significantly reduce data acquisition while maintaining image quality. PMID:23388927

Schwartz, Shimon; Liu, Chenyi; Wong, Alexander; Clausi, David A; Fieguth, Paul; Bizheva, Kostadinka

2013-01-14

258

Reduced density matrix hybrid approach: Application to electronic energy transfer  

SciTech Connect

Electronic energy transfer in the condensed phase, such as that occurring in photosynthetic complexes, frequently occurs in regimes where the energy scales of the system and environment are similar. This situation provides a challenge to theoretical investigation since most approaches are accurate only when a certain energetic parameter is small compared to others in the problem. Here we show that in these difficult regimes, the Ehrenfest approach provides a good starting point for a dynamical description of the energy transfer process due to its ability to accurately treat coupling to slow environmental modes. To further improve on the accuracy of the Ehrenfest approach, we use our reduced density matrix hybrid framework to treat the faster environmental modes quantum mechanically, at the level of a perturbative master equation. This combined approach is shown to provide an efficient and quantitative description of electronic energy transfer in a model dimer and the Fenna-Matthews-Olson complex and is used to investigate the effect of environmental preparation on the resulting dynamics.

Berkelbach, Timothy C.; Reichman, David R. [Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 (United States); Markland, Thomas E. [Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305 (United States)

2012-02-28

259

Data driven signal processing: an approach for energy efficient computing  

Microsoft Academic Search

The computational switching activity of digital CMOS circuits can be dynamically minimized by designing algorithms that exploit signal statistics. This results in processors that have time-varying power requirements and perform computation on demand. An approach is presented to minimize the energy dissipation per data sample in variable-load DSP systems by adaptively minimizing the power supply voltage for each sample using

Anantha Chandrakasan; Vadim Gutnik; Thucydides Xanthopoulos

1996-01-01

260

Aerodynamic yawing moment characteristics of bird wings.  

PubMed

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

Sachs, Gottfried

2005-06-21

261

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

262

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.

263

GAs for aerodynamic shape design II: multiobjective optimization and multi-criteria design  

Microsoft Academic Search

The lecture focuses on multi-objective genetic algorithms with hybrid capabilities, and on their application to multi-criteria design problems. A short introduction to multi- point aerodynamic shape design is given, and the advantages of a multi-objective opti- mization approach to this problem are outlined. The introduction of basic concepts of multi-objective optimization is followed by the description of a multiple objective

D. Quagliarella; A. Vicini

264

Two-Dimensional Aerodynamic Models of Insect Flight for Robotic Flapping Wing Mechanisms of Maximum Efficiency  

Microsoft Academic Search

In the “modified quasi-steady” approach, two-dimensional (2D) aerodynamic models of flapping wing motions are analyzed with focus on different types of wing rotation and different positions of rotation axis to explain the force peak at the end of each half stroke. In this model, an additional velocity of the mid chord position due to rotation is superimposed on the translational

Thien-Tong Nguyen; Doyoung Byun

2008-01-01

265

Experimental Investigation on the Aerodynamic Characteristics of a Biomimetic Flapping Wing with Macro-fiber Composites  

Microsoft Academic Search

This study describes the development of a bio-mimetic flapping wing and the aerodynamic characteristics of a flexible flapping wing. First, the flapping wing is designed to produce flapping, twisting, and camber motions by using a bio-mimetic design approach. A structural model for a macro-fiber composite (MFC) actuator is established, and structural analysis of a smart flapping wing with the actuator

Dae-Kwan Kim; Hong-Il Kim; Jae-Hung Han; Ki-Jung Kwon

2008-01-01

266

Low-energy hadronic interactions beyond the current algebra approach  

NASA Astrophysics Data System (ADS)

Within chiral perturbation theory at the quark level (CHPT)q with linear realization of chiral U(3) × U(3) symmetry the new low-energy AP3-interaction, produced by convergent box-constituent-quark-loop diagrams, is obtained, and its contributions to processes of low-energy interactions of low-lying mesons are investigated. The new interaction goes beyond the framework of the low-energy current algebra approach and effective chiral Lagrangians with linear realization of chiral symmetry, constructed at the hadronic level.

Ivanov, A. N.; Troitskaya, N. I.; Nagy, M.

1993-06-01

267

Aerodynamic performance of osculating-cones waveriders at high altitudes  

NASA Astrophysics Data System (ADS)

The steady-state aerodynamic characteristics of three-dimensional waverider configurations immersed in hypersonic rarefied flows are investigated. Representative geometries are generated using an inverse design procedure, the method of osculating cones, which defines an exit plane shock shape and approximates the flow properties of the compression surface by assuming that each spanwise station along the shock profile lies within a region of locally conical flow. Vehicle surface and flow field properties are predicted using the direct simulation Monte Carlo method, a probabilistic numerical scheme in which simulated molecules are followed through representative collisions with each other and solid surfaces, and subsequent deterministic displacement. The aerodynamic properties of high- and low-Reynolds number waverider geometries, optimized for maximum lift-to-drag ratio and subject to mission-oriented constraints, are contrasted with results from reference caret and delta wings with similar internal volumes to quantify the relevance and advantage of the waverider concept at high altitudes. The high-Reynolds number waverider, optimized for the continuum regime at Minfinity = 4 and Reinfinity = 250 million, was the focus of recent wind tunnel testing for near on-design and off-design conditions, including low subsonic speeds. The present work extends the previous analyses into the high-altitude regime. The low-Reynolds number waverider, optimized at Minfinity = 20 and Reinfinity = 2.5 million, is studied to determine if optimization potential exists for a high-Mach number waverider at high altitudes. A characteristic length of 5 m is assumed for both waverider configurations, representative of a hypersonic missile concept. The geometries are aerodynamically evaluated over a parametric space consisting of an altitude variation of 95 km to 150 km and an angle of attack range of --5° to 10°. The effect of off-design Mach number on the performance of the high-Reynolds number waverider is also considered. At Minfinity = 4 in level flight, from 95 km to 105 km, the lift-to-drag ratio of the volume-matched caret wing is superior to that of the osculating-cones waverider optimized for Minfinity = 4 and Re infinity = 250 million. From 105 km to 150 km, the performance of the osculating-cones waverider is slightly superior to that of caret and delta wings due to the degree of concavity of its lower surface. At off-design conditions, the performance of the three configurations approaches a common free-molecular limit. At Minfinity = 20 in level flight, the lift-to-drag ratio of the osculating-cones waverider optimized for Minfinity = 20 and Reinfinity = 2.5 million is similar to a volume-matched caret wing, due to the caret wing's enhanced lift coefficient. At higher angles of attack, the superior drag characteristics of the osculating-cones waverider produces an increased lift-to-drag ratio over that of the reference configurations from 95 km to 120 km. At higher altitudes, the performance of the three configurations approaches a common free-molecular limit. Maximum lift-to-drag ratio does not exceed unity for the configurations studied over the chosen high-altitude parametric space, which is consistent with previous investigations. Results support the hypothesis that potential for aerodynamic optimization exists at high altitudes for realistic, volume-oriented waverider configurations.

Graves, Rick Evan

268

Fluidization technologies: Aerodynamic principles and process engineering.  

PubMed

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

Dixit, Rahul; Puthli, Shivanand

2009-11-01

269

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.

270

Community-based Energy Model: A Novel Approach to Developing Sustainable Energy  

Microsoft Academic Search

Conventional energy development and management systems are centralized and grid-connected, making the setup vulnerable and unsustainable. In this paper, a new energy development and management model is proposed. This proposed approach aims at utilizing available natural resources and considers the community as the main stakeholder to implement the model. Locally produced wastes are considered as one source for generating energy

M. I. Khan; A. B. Chhetri; M. R. Islam

2007-01-01

271

Aerodynamics of laminar separation flutter at a transitional Reynolds number  

NASA Astrophysics Data System (ADS)

Experimental observations of self-sustained pitch oscillations of a NACA 0012 airfoil at transitional Reynolds numbers were recently reported. The aeroelastic limit cycle oscillations, herein labelled as laminar separation flutter, occur in the range 5.0×104?Rec?1.3×105. They are well behaved, have a small amplitude and oscillate about ?=0°. It has been speculated that laminar separation leading to the formation of a laminar separation bubble, occurring at these Reynolds numbers, plays an essential role in these oscillations. This paper focuses on the Rec=7.7×104 case, with the elastic axis located at 18.6% chord. Considering that the experimental rig acts as a dynamic balance, the aerodynamic moment is derived and is empirically modelled as a generalized Duffing-van-der-Pol nonlinearity. As expected, it behaves nonlinearly with pitch displacement and rate. It also indicates a dynamically unstable equilibrium point, i.e. negative aerodynamic damping. In addition, large eddy simulations of the flow around the airfoil undergoing prescribed simple harmonic motion, using the same amplitude and frequency as the aeroelastic oscillations, are performed. The comparison between the experiment and simulations is conclusive. Both approaches show that the work done by the airflow on the airfoil is positive and both have the same magnitude. The large eddy simulation (LES) computations indicate that at ?=0°, the pitching motion induces a lag in the separation point on both surfaces of the airfoil resulting in negative pitching moment when pitching down, and positive moment when pitching up, thus feeding the LCO.

Poirel, D.; Yuan, W.

2010-10-01

272

Joint computational and experimental aerodynamics research on a reentry vehicle  

SciTech Connect

This paper seeks to improve the synergism between computational aerodynamics and wind tunnel experimentation. In this paper, experimental and computational results are presented for a hypersonic vehicle configuration at Mach 8. Comparisons are made between experimental and computational results in order to improve the accuracy of both approaches. The basic vehicle configuration is a spherically blunted cone with a slice parallel with the axis of the vehicle. The half-angle of the cone is 10 deg. and the ratio of spherical nose radius to base radius in 10%. Onto the slice portion of the vehicle can be attached flaps with three different deflection angles; 10, 20, and 30 deg. All of the experimental results were obtained in the Sandia Mach 8 long duration, blow-down, hypersonic wind tunnel. Flow visualization results include surface oil flow, spark schlieren, and liquid crystal photographs and video. The liquid crystals were used as an aid in verifying that a laminar boundary layer existed over the entire body. An extensive uncertainty analysis was conducted to estimate quantitatively the accuracy of the measurement. Computational aerodynamic force and moment predictions are compared with the wind tunnel data. The Sandia Parabolized Navier-Stokes code is used to generate solutions for the sliced vehicle (no flap) and partial solutions for the flapped vehicle. For the geometry with the flap, an axially separated flow occurs and a time iterative Navier-Stokes code is used to provide comparisons with the data. This paper presents a portion of the results given in earlier works and also discusses new experimental results with this configuration.

Not Available

1991-01-01

273

Multi-Objective Six Sigma Approach Applied to Robust Airfoil Design for Mars Airplane  

Microsoft Academic Search

A new optimization approach for robust design, design for multi-objective six sigma (DFMOSS) has been developed and applied to robust aerodynamic airfoil design for Mars exploratory airplane. The present robust aerodynamic airfoil design optimization using DFMOSS successfully showed the trade-off information between maximization and robust- ness improvement in aerodynamic performance by a single optimization run without careful input parameter tuning.

Koji Shimoyama; Akira Oyama; Kozo Fujii

2007-01-01

274

Final Report 02-ERD-056 Active Load Control& Mitigation Using Microtabs: A Wind Energy Application  

Microsoft Academic Search

With public concern over the security and reliability of our existing electricity infrastructure and the resurgence of wind energy, the wind industry offers an immediate, first point of entry for the application and demonstration of an active load control technology. An innovative microtab approach is being investigated and demonstrated for active aerodynamic load control applications under the mid-year LDRD (June-Sept.

Nakafuji

2003-01-01

275

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

276

Direct identification offlutter derivatives and aerodynamic admittances ofbridge decks  

Microsoft Academic Search

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

Ming Gu; Xian-Rong Qin

2004-01-01

277

Chemical Fractionation in Chondrites by Aerodynamic Sorting of Chondritic Materials  

Microsoft Academic Search

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

E. R. D. Scott; H. Haack

1993-01-01

278

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

279

The Influence of Windshield on Aerodynamic Performance of VAWT  

Microsoft Academic Search

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

Hu Yonghai; Tong Zhengming

2009-01-01

280

Experimental Investigation on Aerodynamic Characteristics of a Paraglider Wing  

Microsoft Academic Search

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

Mohammad Mashud; Akira Umemura

2006-01-01

281

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD  

Microsoft Academic Search

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

W. P. Wolfe; S. S. Ochs

1997-01-01

282

Predicting Aerodynamic Characteristics of Typical Wind Turbine Airfoils Using CFD  

Microsoft Academic Search

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

Walter P. Wolfe

1997-01-01

283

Flat-plate aerodynamics at very low Reynolds number  

Microsoft Academic Search

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

Quanhua Sun; Iain D. Boyd

2004-01-01

284

How Autopilot Requirements Constrain the Aerodynamic Design of Homing Missiles  

Microsoft Academic Search

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

F. William Nesline; Mark L. Nesline

1984-01-01

285

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

286

July 1999 working group meeting on heavy vehicle aerodynamic drag: presentations and summary of comments and conclusions  

Microsoft Academic Search

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at University of Southern California, Los Angeles, California on July 30, 1999. The purpose of the meeting was to present technical details on the experimental and computational plans and approaches and provide an update on progress in obtaining experimental results, model developments, and simulations. The focus of the meeting

M Brady; F Browand; D Flowers; M Hammache; G Landreth; A Leonard; R McCallen; J Ross; W Rutledge; K Salari

1999-01-01

287

March 1999 working group meeting on heavy vehicle aerodynamic drag: presentations and summary of comments and conclusions  

Microsoft Academic Search

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory, Livermore, California on March 11, 1999. The purpose of the meeting was to present technical details on the experimental and computational plans and approaches and provide an update on progress in obtaining experimental results, model developments, and simulations. The focus of the meeting was

M Brady; F Browand; R McCallen; J Ross; K Salari

1999-01-01

288

October 1998 working group meeting on heavy vehicle aerodynamic drag: presentations and summary of comments and conclusions  

Microsoft Academic Search

A Working Group 1Meeting on Heavy Vehicle Aerodynamic Drag was held at NASA Ames Research Center, Moffett Field, California on October 22, 1998. The purpose of the meeting was to present an overview of the computational and experimental approach for modeling the integrated tractor-trailer benchmark geometry called the Sandia IModel and to review NASA� s test plan for their experiments

F Browand; J T Heineck; A Leonard; D McBride; R McCallen; J Ross; W Rutledge; K Salari; B Storms

1998-01-01

289

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

290

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

291

Unsteady aerodynamic models for agile flight at low Reynolds numbers  

NASA Astrophysics Data System (ADS)

This work develops low-order models for the unsteady aerodynamic forces on a wing in response to agile maneuvers at low Reynolds number. Model performance is assessed on the basis of accuracy across a range of parameters and frequencies as well as of computational efficiency and compatibility with existing control techniques and flight dynamic models. The result is a flexible modeling procedure that yields accurate, low-dimensional, state-space models. The modeling procedures are developed and tested on direct numerical simulations of a two-dimensional flat plate airfoil in motion at low Reynolds number, Re=100, and in a wind tunnel experiment at the Illinois Institute of Technology involving a NACA 0006 airfoil pitching and plunging at Reynolds number Re=65,000. In both instances, low-order models are obtained that accurately capture the unsteady aerodynamic forces at all frequencies. These cases demonstrate the utility of the modeling procedure developed in this thesis for obtaining accurate models for different geometries and Reynolds numbers. Linear reduced-order models are constructed from either the indicial response (step response) or realistic input/output maneuvers using a flexible modeling procedure. The method is based on identifying stability derivatives and modeling the remaining dynamics with the eigensystem realization algorithm. A hierarchy of models is developed, based on linearizing the flow at various operating conditions. These models are shown to be accurate and efficient for plunging, pitching about various points, and combined pitch and plunge maneuvers, at various angle of attack and Reynolds number. Models are compared against the classical unsteady aerodynamic models of Wagner and Theodorsen over a large range of Strouhal number and reduced frequency for a baseline comparison. Additionally, state-space representations are developed for Wagner's and Theodorsen's models, making them compatible with modern control-system analysis. A number of computational tools are developed throughout this work. Highly unsteady maneuvers are visualized using finite-time Lyapunov exponent fields, which highlight separated flows and wake structures. A new fast method of computing these fields is presented. In addition, we generalize the immersed boundary projection method computations to use a moving base flow, which allows for the simulation of complex geometries undergoing large motions with up to an order of magnitude speed-up. The methods developed in this thesis provide a systematic approach to identify unsteady aerodynamic models from analytical, numerical, or experimental data. The resulting models are shown to be reduced-order models of the linearized Navier-Stokes equations that are expressed in state-space form, and they are, therefore, both efficient and accurate. The specific form of the model, which separates added-mass forces, quasi-steady lift, and transient forces, guarantees that the resulting models are accurate over the entire range of frequencies. Finally, the models are low-dimensional linear systems of ordinary differential equations, so that they are compatible with existing flight dynamic models as well as a wealth of modern control techniques.

Brunton, Steven L.

292

DOE's effort to reduce truck aerodynamic drag through joint experiments and computations  

Microsoft Academic Search

Class 8 tractor-trailers are responsible for 11-12% of the total US consumption of petroleum. Overcoming aero drag represents 65% of energy expenditure at highway speeds. Most of the drag results from pressure differences and reducing highway speeds is very effective. The goal is to reduce aerodynamic drag by 25% which would translate to 12% improved fuel economy or 4,200 million

Kambiz Salari; Fred Browand; Kidambi Sreenivas; W. David Pointer; Lafayette Taylor; Ramesh Pankajakshan; David Whitfield; Dennis Plocher; Jason M. Ortega; Tai Merzel; Rose McCallen; Stephen M Walker; James T Heineck; Basil Hassan; Christopher John Roy; B. Storms; James Ross; Robert Englar; Mike Rubel; Anthony Leonard; Charles Radovich; Craig Eastwood; John Paschkewitz; Paul Castellucci; Lawrence Justin. DeChant

2005-01-01

293

DOE Project on Heavy Vehicle Aerodynamic Drag FY 2005 Annual Report  

Microsoft Academic Search

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

R C McCallen; K Salari; J Ortega; P Castellucci; C Eastwood; J Paschkewitz; W D Pointer; L J DeChant; B Hassan; F Browand; C Radovich; T Merzel; D Plocher; J Ross; B Storms; J T Heineck; S Walker; C J Roy

2005-01-01

294

Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds  

NASA Astrophysics Data System (ADS)

The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. Elastic energy deposited in the bed by the impacting grain creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains from closed to open packing, and grains are consequently able to eject themselves forcefully from the impact site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. There is a great temptation to draw parallels with cratering produced by meteorite impacts, but a rigorous search for common modelling ground between the two phenomena has not been conducted at this time. For every impact of an aerodynamically energized grain, there are several hundred grains ejected into the wind for the high-energy transport that might occur on Mars. Many of these grains will themselves become subject to the boundary layer's aerodynamic lift forces (their motion will not immediately die and add to the creep population), and these grains will become indistinguishable from those lifted entirely by aerodynamic forces. As each grain impacts the bed, it will eject even more grains into the flow. A cascading effect will take place, but because it must be finite in its growth, damping will occur as the number of grains set in motion causes mid-air collisions that prevent much of the impact energy from reaching the surface of the bed -thus creating a dynamic equilibrium in a high-density saltation cloud. It is apparent that for a given impact energy, the stress field permits a smaller volume of grains to convert to open packing as the size of the bed grains increases, or as the energy of the "percussive" grain decreases

Marshall, J. R.; Borucki, J.; Bratton, C.

1999-09-01

295

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

SciTech Connect

The objective of this report is: (1) Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles; and (2) Establish a database of experimental, computational, and conceptual design information, and demonstrate potential of new drag-reduction devices. The approaches used were: (1) Develop and demonstrate the ability to simulate and analyze aerodynamic flow around heavy truck vehicles using existing and advanced computational fluid dynamics (CFD) tools; (2) Through an extensive experimental effort, generate an experimental data base for code validation; (3) Using experimental data base, validate computations; (4) Provide industry with design guidance and insight into flow phenomena from experiments and computations; and (5) Investigate aero devices (e.g., base flaps, tractor-trailer gap stabilizer, underbody skirts and wedges, blowing and acoustic devices), provide industry with conceptual designs of drag reducing devices, and demonstrate the full-scale fuel economy potential of these devices.

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

2004-11-18

296

March 2000 Working Group Meeting on Heavy Vehicle Aerodynamic DragL Presentations and Summary of Comments and Conclusions  

SciTech Connect

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory on March 16, 2000. The purpose of the meeting was to present technical details on the experimental and computational plans and approaches and provide an update on progress in the analysis of experimental results, model developments, simulations, and an investigation of an aerodynamic device. The focus of the meeting was a review of University of Southern California's (USC) experimental plans and results, NASA Ames experimental plans, the computational results from Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories (SNL) for the integrated tractor-trailer benchmark geometry called the Ground Transportation System (GTS) Model, and turbulence model development and benchmark simulation for a rounded cube from California Institute of Technology (Caltech). Much of the meeting discussion involved deficiencies in commercial software, needed modeling improvements, and the importance of detailed data for code validation. The present and projected budget and funding situation was also discussed. Presentations were given by representatives from the Department of Energy (DOE) Office of Transportation Technology Office of Heavy Vehicle Technology (OHVT), LLNL, SNL, NASA Ames, USC, and Caltech. Representatives from Argonne National Laboratory also participated via telephone. This report contains the technical presentations (viewgraphs) delivered at the Meeting, briefly summarizes the comments and conclusions, and outlines the future action items. There were 3 major issues raised at the meeting. (1) Our funding is inadequate to satisfy industries request for high Reynolds number experimentation and computation. Plans are to respond to the DOD and DOE requests for proposals, which require a 50-50 cost share with industry, to acquire funding for high Reynolds number experiments at NASA Ames. (2) The deficiencies in commercial software, the need for model improvements and validation, and the unavailability of a detailed database for advanced model validation needs to be recognized. (3) The need for industrial collaboration appears to be a requirement for acquiring funding.

McCallen, R.; Flowers, D.; Dunn, T.; Owens, J.; Browand, F.; Hammache, M.; Loenard, A.; Brady, M.; Salari, K.; Rutledge, W.; Scheckler, R.; Ross, J.; Storms, B.; Heineck, J.T.; Arledge, T

2000-05-15

297

A challenging approach for renewable energy market development  

Microsoft Academic Search

This study demonstrates a challenging production-based and market-driven approach for the development of renewable energy (RE) market. The organized data in our research show that the countries that adopt more RE policies appear to generate more RE products. Among those instruments, incentives\\/subsidies for production are common and decisive to the popularization of RE products.Recently, the primary RE policy goal for

Ching-Hui Liao; Hsin-Hung Ou; Shang-Lien Lo; Pei-Te Chiueh; Yue-Hwa Yu

2011-01-01

298

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

Microsoft Academic Search

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

G. F. Aiello; M. C. Bateman

1979-01-01

299

Free energies of ferroelectric crystals from a microscopic approach  

NASA Astrophysics Data System (ADS)

The free energy of barium titanate is computed around the Curie temperature as a function of polarization P? from the first-principles derived Effective Hamiltonian of Zhong, Vanderbilt and Rabe [Phys. Rev. Lett. 73 (1994) 1861], through Molecular Dynamics simulations coupled to the method of the Thermodynamic Integration. The algorithms used to fix the temperature (Nosé-Hoover) and/or the pressure/stress (Parrinello-Rahman), combined with fixed-polarization molecular dynamics, allow to compute a Helmholtz free energy (fixed volume/strain) or a Gibbs free energy (fixed pressure/stress). The main feature of this approach is to calculate the gradient of the free energy in the 3-D space (P, P, P) from the thermal averages of the forces acting on the local modes, that are obtained by Molecular Dynamics under the constraint of fixed P?. This work extends the method presented in [Phys. Rev. B 79 (2009) 064101] to the calculation of the Gibbs free energy and presents new features about the computation of the free energy of ferroelectric crystals from a microscopic approach. A careful analysis of the states of constrained polarization is performed at T=280 K (?15-17 K below T) especially at low order parameter. These states are found reasonably homogeneous for small supercell size (L=12 and L=16), until inhomogeneous states are observed at low order parameter for large supercells (L=20). The effect of this evolution towards multidomain configurations on the mean force and free energy curves is shown. However, for reasonable supercell sizes (L=12), the free energy curves obtained are in very good agreement with phenomenological Landau potentials of the literature and the states of constrained polarization are homogeneous. Moreover, the free energy obtained is quite insensitive to the supercell size from L=12 to L=16 at T=280 K, suggesting that interfacial contributions, if any, are negligible at these sizes around T. The method allows a numerical estimation of the free energy barrier separating the paraelectric from the ferroelectric phase at T (?G?0.012-0.015 meV/5-atom cell). However, our tests evidence phase separation at low temperature and low order parameter, in agreement with the results of Tröster et al. [Phys. Rev. B 72 (2005) 094103]. Finally, the natural decomposition of the forces into onsite, short-range, dipole-dipole and elastic-local mode interaction allows to make the same decomposition of the free energy. Some parts of this decomposition can be directly calculated from the coefficients of the Effective Hamiltonian.

Geneste, Grégory

2010-04-01

300

CFD calculations of S809 aerodynamic characteristics  

SciTech Connect

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

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

1997-01-01

301

Experimental Aerodynamics of Mesoscale Trailing Edge Actuators  

NASA Astrophysics Data System (ADS)

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

Solovitz, Stephen; Eaton, John

2001-11-01

302

Beyond robins: aerodynamic analyses of animal flight  

PubMed Central

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

Hedenstrom, Anders; Spedding, Geoffrey

2008-01-01

303

Methods of reducing vehicle aerodynamic drag  

SciTech Connect

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

Sirenko V.; Rohatgi U.

2012-07-08

304

Exploring the Fast Ignition Approach to Fusion Energy  

SciTech Connect

Probably the most famous equation in physics is Einstein's E=mc{sup 2}, which was contained within his fifth and final paper that was published in 1905. It is this relationship between energy ( E) and mass ( m) that the fusion process exploits to generate energy. When two isotopes of hydrogen (normally Deuterium and Tritium (DT)) fuse they form helium and a neutron. In this process some of the mass of the hydrogen is converted into energy. In the fast ignition approach to fusion a large driver (such as the NIF laser) is used to compress the DT fuel to extremely high densities and then is ''sparked'' by a high intensity, short-pulse laser. The short-pulse laser energy is converted to an electron beam, which then deposits its energy in the DT fuel. The energy of the electrons in this beam is so large that the electron's mass is increased according to Einstein theory of relativity. Understanding the transport of this relativistic electron beam is critical to the success of fast ignition and is the subject of this poster.

Town, R J; Chung, H; Cottrill, L A; Foord, M; Hatchett, S P; Key, M H; Langdon, A B; Lasinski, B F; Lund, S; Mackinnon, A J; McCandless, B C; Patel, P K; Sharp, W L; Snavely, R A; Still, C H; Tabak, M

2005-04-18

305

Conversion of Phase II Unsteady Aerodynamics Experiment Data to Common Format  

SciTech Connect

A vast amount of aerodynamic, structural, and turbine performance data were collected during three phases of the National Renewable Energy Laboratory's Unsteady Aerodynamics Experiment (UAE). To compare data from the three phases, a similar format of engineering unit data is required. The process of converting Phase II data from a previous engineering unit format to raw integer counts is discussed. The integer count files can then be input to the new post-processing software, MUNCH. The resulting Phase II engineering unit files are in a common format with current and future UAE engineering unit files. An additional objective for changing the file format was to convert the Phase II data from English units to SI units of measurement.

Hand, M. M.

1999-07-19

306

Wind Turbine Aerodynamics Prediction Using Free-Wake Method in Axial Flow  

NASA Astrophysics Data System (ADS)

Wind turbine aerodynamics remains a particularly challenging and crucial research for wind energy industry. The blade element momentum theory is the most widely used in predicting the performance of wind turbine, since the method is simple and fast numerical algorithm. The flow field generated by rotary wing is considerably important and complicated, however, the BEM method has some limitations to model the unsteady effects. To overcome these limitations, the aerodynamic analysis using a time-marching free-vortex wake method was performed in this paper. Moreover, the inboard region of the blade experience a delay in stall and enhanced values of the normal force coefficient because of rotational boundary layer augmentation and three-dimensional effects. For this reason, Raj-Selig stall delay model was applied in this research. The numerical results were compared with experimental data, and the present results show excellent agreement with experiment.

Jeong, Min-Soo; Yoo, Seung-Jae; Lee, In

307

Aerodynamic Performance Enhancement of a Finite Span Wind Turbine Blade using Synthetic Jets  

NASA Astrophysics Data System (ADS)

Modern wind turbines undergo significant changes in pitch angle and structural loading through a revolution. Recent developments in flow control techniques, coupled with increased interest in green energy technologies, have led to interest in applying these techniques to wind turbines, in an effort to increase power output and reduce structural stress associated with widely varying loading. This reduction in structural stress could lead to reduced operational costs associated with the maintenance cycle. The effect of active flow control on the aerodynamic and structural aspects of finite span blade was investigated experimentally. When synthetic jets were employed the effect on aerodynamic performance and structural vibrations, during static and dynamic pitch conditions, was significant. In order to investigate if the jets can be actuated for less time (reduce their power consumption), they were actuated during only a portion of the pitch cycle or using pulse modulation. The results showed that these techniques result in significant reduction in the hysteresis loop and the structural vibrations.

Taylor, Keith; Leong, Chia Min; Amitay, Michael

2011-11-01

308

Aerodynamics of a cycling team in a time trial: does the cyclist at the front benefit?  

NASA Astrophysics Data System (ADS)

When seasonal journeys take place in nature, birds and fishes migrate in groups. This provides them not only with security but also a considerable saving of energy. The power they need to travel requires overcoming aerodynamic or hydrodynamic drag forces, which can be substantially reduced when the group travels in an optimal arrangement. Also in this area, humans imitate nature, which is especially evident in the practice of outdoor sports and motor competitions. Cycle races, in which speeds of up to 15 m s-1 are frequent, offer great opportunities to appreciate the advantage of travelling in a group. Here we present a brief analysis of the aerodynamics of a cycling team in a time-trial challenge, showing how each rider is favoured according to his position in the group. We conclude that the artificial tail wind created by the team also benefits the cyclist at the front by about 5%.

Íñiguez-de-la Torre, A.; Íñiguez, J.

2009-11-01

309

July 2004 Working Group Meeting on Heavy Vehicle Aerodynamic Drag: Presentation, Summary of Comments, and Conclusions  

SciTech Connect

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held in Portland, Oregon on July 1, 2004. The purpose of the meeting was to provide a summary of achievements, discuss pressing issues, present a general overview of future plans, and to provide a forum for dialogue with the Department of Energy (DOE) and industry representatives. The meeting was held in Portland, because the DOE Aero Team participated in an exclusive session on Heavy Truck Vehicle Aerodynamic Drag at the 34th AIAA Fluid Dynamics Conference and Exhibit in Portland on the morning of July 1st, just preceding our Working Group meeting. Even though the paper session was on the last day of the Conference, the Team presented to a full room of interested attendees.

McCallen, R; Salari, K; Ortega, J; Castellucci, P; Eastwood, C; DeChant, L; Hassan, B; Browand, F; Arcas, D; Ross, J; Heineck, J; Storms, B; Walker, S; Leonard, A; Roy, C; Whitfield, D; Pointer, D; Sofu, T; Englar, R; Funk, R

2004-08-17

310

DOE Project on Heavy Vehicle Aerodynamic Drag FY 2005 Annual Report  

SciTech Connect

Class 8 tractor-trailers consume 11-12% of the total US petroleum use. At high way speeds, 65% of the energy expenditure for a Class 8 truck is in overcoming aerodynamic drag. The project objective is to improve fuel economy of Class 8 tractor-trailers by providing guidance on methods of reducing drag by at least 25%. A 25% reduction in drag would present a 12% improvement in fuel economy at highway speeds, equivalent to about 130 midsize tanker ships per year. Specific goals include: (1) Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles; and (2) Establish a database of experimental, computational, and conceptual design information, and demonstrate the potential of new drag-reduction devices.

McCallen, R C; Salari, K; Ortega, J; Castellucci, P; Eastwood, C; Paschkewitz, J; Pointer, W D; DeChant, L J; Hassan, B; Browand, F; Radovich, C; Merzel, T; Plocher, D; Ross, J; Storms, B; Heineck, J T; Walker, S; Roy, C J

2005-11-14

311

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

Microsoft Academic Search

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

Li Xing-Wei; Pan Xiao

2008-01-01

312

Fourier analysis of the aerodynamic behavior of cup anemometers  

NASA Astrophysics Data System (ADS)

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

Pindado, Santiago; Pérez, Imanol; Aguado, Maite

2013-06-01

313

September 2002 Working Group Meeting on Heavy Vehicle Aerodynamic Drag: Presentations and Summary of Comments and Conclusions  

Microsoft Academic Search

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at NASA Ames Research Center on September 23, 2002. The purpose of the meeting was to present and discuss technical details on the experimental and computational work in progress and future project plans. Representatives from the Department of Energy (DOE)\\/Office of Energy Efficiency and Renewable Energy\\/Office of FreedomCAR &

McCallen

2002-01-01

314

A Multi-Year Program Plan for the Aerodynamic Design of Heavy Vehicles  

SciTech Connect

The project tasks and deliverables are as follows: Computations and Experiments--(1) Simulation and analysis of a range of generic shapes, simplified to more complex, representative of tractor and integrated tractor-trailer flow characteristics using computational tools, (2) The establishment of an experimental data base for tractor-trailer models for code/computational method development and validation. The first shapes to be considered will be directed towards the investigation of tractor-trailer gaps and mismatch of tractor-trailer heights. (3) The evaluation and documentation of effective computational approaches for application to heavy vehicle aerodynamics based on the benchmark results with existing and advanced computational tools compared to experimental data, and (4) Computational tools and experimental methods for use by industry, National Laboratories, and universities for the aerodynamic modeling of heavy truck vehicles. Evaluation of current and new technologies--(1) The evaluation and documentation of current and new technologies for drag reduction based on published literature and continued communication with the heavy vehicle industry (e.g., identification and prioritization of tractor-trailer drag-sources, blowing and/or suction devices, body shaping, new experimental methods or facilities), and the identification and analysis of tractor and integrated tractor-trailer aerodynamic problem areas and possible solution strategies. (2) Continued industrial site visits. It should be noted that ''CFD tools'' are not only the actual computer codes, but descriptions of appropriate numerical solution methods. Part of the project effort will be to determine the restrictions or avenues for technology transfer.

None

2001-09-01

315

Simulation-based aerodynamic design of high-lift devices in ground effect  

NASA Astrophysics Data System (ADS)

A simulation-based aerodynamic design tool is developed for multi-element high-lift airfoils operating in ground effect. A control theory approach is adopted, using the compressible Navier-Stokes equations as the basis for viscous design of airfoil element shapes and relative positioning. Particular considerations of aerodynamic design, high-lift systems, and the ground effect are described, and the suitability of aerodynamic shape optimization of such systems is discussed. The model of fluid flow and its discretization for solution on digital computers is investigated. A cell-centered finite-volume explicit multigrid method is used to solve both the flow and adjoint systems utilizing structured multiblock meshes. The adjoint equations for shape optimization are developed using a continuous adjoint formulation, and implemented with a moving ground boundary condition for the first time. A suite of test cases verified and validated the numerical algorithms and implementation. Realistic case studies were performed, demonstrating significant performance improvements over the baseline configurations. These included two free-air multi-element airfoil drag minimizations, and in addition two inverted two-element airfoil drag minimizations in ground effect.

Melvin, Arron Hector

316

A back-reaction approach to dark energy  

NASA Astrophysics Data System (ADS)

This thesis is mainly about how to set up and carry out in a physically meaningful way the idea of back-reaction, according to which dark energy could be an effective source. There are, broadly speaking, two distinct approaches. One is focused on how cosmological observables are affected by inhomogeneities, while the other is focused on a theoretical description of the inhomogeneous universe by means of a mean-field description. Both approaches, however, share the idea of smoothing out inhomogeneities. We developed this duality in the interpretation of the back-reaction by means of toy models based on the Lemaitre-Tolman-Bondi solution of Einstein's equations. In particular we focused on voids expanding faster than the background solution.

Marra, Valerio

2008-03-01

317

Adaptive flow control of low-Reynolds number aerodynamics using dielectric barrier discharge actuator  

NASA Astrophysics Data System (ADS)

Aerodynamic performance of low-Reynolds number flyers, for a chord-based Reynolds number of 105 or below, is sensitive to wind gusts and flow separation. Active flow control offers insight into fluid physics as well as possible improvements in vehicle performance. While facilitating flow control by introducing feedback control and fluidic devices, major challenges of achieving a target aerodynamic performance under unsteady flow conditions lie on the high-dimensional nonlinear dynamics of the flow system. Therefore, a successful flow control framework requires a viable as well as accessible control scheme and understanding of underlying flow dynamics as key information of the flow system. On the other hand, promising devices have been developed recently to facilitate flow control in this flow regime. The dielectric barrier discharge (DBD) actuator is such an example; it does not have moving parts and provides fast impact on the flow field locally. In this paper, recent feedback flow control studies, especially those focusing on unsteady low-Reynolds number aerodynamics, are reviewed. As an example of an effective flow control framework, it is demonstrated that aerodynamic lift of a high angle-of-attack wing under fluctuating free-stream conditions can be stabilized using the DBD actuator and an adaptive algorithm based on general input-output models. System nonlinearities and control challenges are discussed by assessing control performance and the variation of the system parameters under various flow and actuation conditions. Other fundamental issues from the flow dynamics view point, such as the lift stabilization mechanism and the influence on drag fluctuation are also explored. Both potentiality and limitation of the linear modeling approach are discussed. In addition, guidelines on system identification and the controller and actuator setups are suggested.

Cho, Young-Chang; Shyy, Wei

2011-10-01

318

Investigating Complex Aerodynamic Flows with a Laser Velocimeter.  

National Technical Information Service (NTIS)

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

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

1976-01-01

319

Aerodynamic Characteristics of Passenger Vehicle/Trailer Combinations.  

National Technical Information Service (NTIS)

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

J. W. Zellner

1982-01-01

320

Aerodynamics of flapping wings with fluttering trailing edges  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

321

Aerodynamic and Related Hydrodynamic Studies Using Water Facilities.  

National Technical Information Service (NTIS)

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

1987-01-01

322

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

National Technical Information Service (NTIS)

The Johns Hopkins University/Applied Physics Laboratory, JHU/API, in support of Lawrence Livermore National Laboratory, LLNL, is conducting aerodynamic, trajectory, and structural analysis of the Advanced Single Stage Technology Rapid Insertion Demonstrat...

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

1994-01-01

323

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD.  

National Technical Information Service (NTIS)

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

W. P. Wolfe S. S. Ochs

1997-01-01

324

Computerized Data Catalog and Retrieval System for Deployable Aerodynamic Decelerators.  

National Technical Information Service (NTIS)

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

T. J. Hogan J. J. Schauer

1967-01-01

325

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

National Technical Information Service (NTIS)

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

J. E. Fidler M. C. Bateman

1974-01-01

326

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

ERIC Educational Resources Information Center

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

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

1994-01-01

327

Low-Density Aerodynamics of the Stardust Sample Return Capsule.  

National Technical Information Service (NTIS)

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

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

2004-01-01

328

Computational Investigation of the Aerodynamic Effects on Fluidic Thrust Vectoring.  

National Technical Information Service (NTIS)

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

K. A. Deere

2000-01-01

329

Energy in Physical Planning: An Approach to Calculating Energy Requirements for Heating, Transportation and Other Forms of Infrastructure.  

National Technical Information Service (NTIS)

In a study entitled Energy in Physical Planning. An approach to calculating energy requirements for heating, transportation and other forms of infrastructure a method is presented for making tentative calculations on the use of energy in various physical ...

J. Lamm B. Nielsen P. Wennerhag

1982-01-01

330

Aerodynamic size association of 7Be in ambient aerosols  

Microsoft Academic Search

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

C. Papastefanou; A. Ioannidou

1995-01-01

331

ROBUST STRUCTURAL DESIGN FOR ACTIVE AEROELASTIC WING WITH AERODYNAMIC UNCERTAINTIES  

Microsoft Academic Search

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

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

2000-01-01

332

Aerodynamics and design for ultra-low Reynolds number flight  

Microsoft Academic Search

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

Peter Josef Kunz

2003-01-01

333

Numerical investigation of unsteady aerodynamic characteristics of a pitching missile  

Microsoft Academic Search

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

Lizhi Yang; Minghai Wang; Zhenghong Gao

2011-01-01

334

Advanced Aerodynamic Design of Passive Porosity Control Effectors  

Microsoft Academic Search

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

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

2001-01-01

335

On the aerodynamic and aeroelastic response of a bridge tower  

Microsoft Academic Search

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

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

2011-01-01

336

REVIEW OF X-33 HYPERSONIC AERODYNAMIC AND AEROTHERMODYNAMIC DEVELOPMENT  

Microsoft Academic Search

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

Richard A. Thompson

2000-01-01

337

Aerodynamics of an Australian Rules Foot Ball and Rugby Ball  

Microsoft Academic Search

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

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

338

An Energy Approach to Capillary-Driven Thin Film Folding  

NASA Astrophysics Data System (ADS)

Capillary-driven self-assembly methods provide a promising tool to fabricate three-dimensional, micro- or millimeter scale structures. Recently, we explored the self-assembly of 3D photovoltaic devices from Si thin films through equilibrium considerations of fluid-solid interactions (Guo, et al. 2009, Li, et al. 2010). In the present study, an alternative approach, the minimization of the total free energy is employed to investigate the interactions between fluid droplet and a flexible thin film. Variation of a 2D energy functional, comprising the surface energy of the fluid and the bending energy of the thin film, yields governing equations and boundary conditions. Through direct simulations with Surface Evolver (Brakke 2008), the shape of the droplet and the thin film at the equilibrium state is obtained. A critical thin film length necessary for complete enclosure of the fluid droplet, and thus successful device self-assembly, is determined and compared with the experimental study of Guo et al. (2009). Augmenting the formalism, we obtain an upper bound of the thin film length, beyond which gravity is dominant. The current 2D study can be extended into 3D. Critical parameters obtained from these analyses can be used to guide device fabrication and manufacturing.

Li, Huan; Hsia, K. Jimmy; Hilgenfeldt, Sascha

2010-11-01

339

Dynamic energy budget approaches for modelling organismal ageing  

PubMed Central

Ageing is a complex multifactorial process involving a progressive physiological decline that, ultimately, leads to the death of an organism. It involves multiple changes in many components that play fundamental roles under healthy and pathological conditions. Simultaneously, every organism undergoes accumulative ‘wear and tear’ during its lifespan, which confounds the effects of the ageing process. The scenario is complicated even further by the presence of both age-dependent and age-independent competing causes of death. Various manipulations have been shown to interfere with the ageing process. Calorie restriction, for example, has been reported to increase the lifespan of a wide range of organisms, which suggests a strong relation between energy metabolism and ageing. Such a link is also supported within the main theories for ageing: the free radical hypothesis, for instance, links oxidative damage production directly to energy metabolism. The Dynamic Energy Budgets (DEB) theory, which characterizes the uptake and use of energy by living organisms, therefore constitutes a useful tool for gaining insight into the ageing process. Here we compare the existing DEB-based modelling approaches and, then, discuss how new biological evidence could be incorporated within a DEB framework.

van Leeuwen, Ingeborg M. M.; Vera, Julio; Wolkenhauer, Olaf

2010-01-01

340

Dynamic energy budget approaches for modelling organismal ageing.  

PubMed

Ageing is a complex multifactorial process involving a progressive physiological decline that, ultimately, leads to the death of an organism. It involves multiple changes in many components that play fundamental roles under healthy and pathological conditions. Simultaneously, every organism undergoes accumulative 'wear and tear' during its lifespan, which confounds the effects of the ageing process. The scenario is complicated even further by the presence of both age-dependent and age-independent competing causes of death. Various manipulations have been shown to interfere with the ageing process. Calorie restriction, for example, has been reported to increase the lifespan of a wide range of organisms, which suggests a strong relation between energy metabolism and ageing. Such a link is also supported within the main theories for ageing: the free radical hypothesis, for instance, links oxidative damage production directly to energy metabolism. The Dynamic Energy Budgets (DEB) theory, which characterizes the uptake and use of energy by living organisms, therefore constitutes a useful tool for gaining insight into the ageing process. Here we compare the existing DEB-based modelling approaches and, then, discuss how new biological evidence could be incorporated within a DEB framework. PMID:20921044

van Leeuwen, Ingeborg M M; Vera, Julio; Wolkenhauer, Olaf

2010-11-12

341

Aerodynamic Performances of Corrugated Dragonfly Wings at Low Reynolds Numbers  

NASA Astrophysics Data System (ADS)

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

Tamai, Masatoshi; He, Guowei; Hu, Hui

2006-11-01

342

The trouble with chemical energy: why understanding bond energies requires an interdisciplinary systems approach.  

PubMed

Helping students understand "chemical energy" is notoriously difficult. Many hold inconsistent ideas about what energy is, how and why it changes during the course of a chemical reaction, and how these changes are related to bond energies and reaction dynamics. There are (at least) three major sources for this problem: 1) the way biologists talk about chemical energy (which is also the way we talk about energy in everyday life); 2) the macroscopic approach to energy concepts that is common in physics and physical sciences; and 3) the failure of chemistry courses to explicitly link molecular with macroscopic energy ideas. From a constructivist perspective, it is unlikely that students can, without a coherent understanding of such a central concept, attain a robust and accurate understanding of new concepts. However, changes are on the horizon, guided by the increasing understanding that difficult concepts require coherent, well-designed learning progressions and the new National Research Council Framework for K-12 Science Education. We provide supporting evidence for our assertions and suggestions for an interdisciplinary learning progression designed to better approach the concept of bond energies, a first step in an understanding chemical energy and behavior of reaction systems that is central to biological systems. PMID:23737636

Cooper, Melanie M; Klymkowsky, Michael W

2013-01-01

343

Aerodynamic Flow Control of a Maneuvering Airfoil  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

344

Aerodynamic characteristics of an oscillating airfoil  

NASA Astrophysics Data System (ADS)

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

Wickens, R. H.

1986-03-01

345

Aerodynamics of high aspect-ratio sails  

NASA Astrophysics Data System (ADS)

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

Crook, Andrew; Gerritsen, Margot

2003-11-01

346

Recent advances in transonic axial compressor aerodynamics  

NASA Astrophysics Data System (ADS)

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

Biollo, Roberto; Benini, Ernesto

2013-01-01

347

Oscillating cascade aerodynamics at large mean incidence  

SciTech Connect

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

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

1998-01-01

348

Japan's Residential Energy Demand Outlook to 2030 Considering Energy Efficiency Standards"Top-Runner Approach"  

SciTech Connect

As one of the measures to achieve the reduction in greenhouse gas emissions agreed to in the"Kyoto Protocol," an institutional scheme for determining energy efficiency standards for energy-consuming appliances, called the"Top-Runner Approach," was developed by the Japanese government. Its goal is to strengthen the legal underpinnings of various energy conservation measures. Particularly in Japan's residential sector, where energy demand has grown vigorously so far, this efficiency standard is expected to play a key role in mitigating both energy demand growth and the associated CO2 emissions. This paper presents an outlook of Japan's residential energy demand, developed by a stochastic econometric model for the purpose of analyzing the impacts of the Japan's energy efficiency standards, as well as the future stochastic behavior of income growth, demography, energy prices, and climate on the future energy demand growth to 2030. In this analysis, we attempt to explicitly take into consideration more than 30 kinds of electricity uses, heating, cooling and hot water appliances in order to comprehensively capture the progress of energy efficiency in residential energy end-use equipment. Since electricity demand, is projected to exhibit astonishing growth in Japan's residential sector due to universal increasing ownership of electric and other appliances, it is important to implement an elaborate efficiency standards policy for these appliances.

Lacommare, Kristina S H; Komiyama, Ryoichi; Marnay, Chris

2008-05-15

349

Aerodynamic and aeroelastic analysis of bundled cables by numerical simulation  

NASA Astrophysics Data System (ADS)

A numerical model for the aerodynamic and aeroelastic analysis of bundled cables, commonly used in energy transmission lines, is presented in this work. The bundles were idealized by a sectional model representing the section at the mid span between two supporting towers. A slightly compressible viscous fluid was considered and the two-dimensional flow was analyzed using a two-step explicit method with an arbitrary Eulerian Lagrangean description. A Taylor series expansion was used in time and the classical Galerkin technique with the finite element method were used for space discretization. Turbulence was modeled using large eddy simulation with the classical Smagorinsky?s sub-grid scale model. The set of cables forms a single body with elastic constrains working mechanically coupled, being each cable linked to the others by spacers. The fluid structure interaction was taken into account considering equilibrium and compatibility conditions at the fluid solid interfaces, and the resulting dynamical equilibrium equation was solved using the Newmark's method.

Braun, A. L.; Awruch, A. M.

2005-06-01

350

Micro air vehicle-motivated computational biomechanics in bio-flights: aerodynamics, flight dynamics and maneuvering stability  

NASA Astrophysics Data System (ADS)

Aiming at developing an effective tool to unveil key mechanisms in bio-flight as well as to provide guidelines for bio-inspired micro air vehicles (MAVs) design, we propose a comprehensive computational framework, which integrates aerodynamics, flight dynamics, vehicle stability and maneuverability. This framework consists of (1) a Navier-Stokes unsteady aerodynamic model; (2) a linear finite element model for structural dynamics; (3) a fluid-structure interaction (FSI) model for coupled flexible wing aerodynamics aeroelasticity; (4) a free-flying rigid body dynamic (RBD) model utilizing the Newtonian-Euler equations of 6DoF motion; and (5) flight simulator accounting for realistic wing-body morphology, flapping-wing and body kinematics, and a coupling model accounting for the nonlinear 6DoF flight dynamics and stability of insect flapping flight. Results are presented based on hovering aerodynamics with rigid and flexible wings of hawkmoth and fruitfly. The present approach can support systematic analyses of bio- and bio-inspired flight.

Liu, Hao; Nakata, Toshiyuki; Gao, Na; Maeda, Masateru; Aono, Hikaru; Shyy, Wei

2010-12-01

351

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

PubMed

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

Lee, Seunghoon; Lee, Seungmin; Lee, Soogab

2013-02-01

352

Evidence that aerodynamic effects, including dynamic stall, dictate HAWT structural loads and power generation in highly transient time frames  

SciTech Connect

Aerodynamic data collected from the National Renewable Energy Laboratory`s Combined Experiment have shown three distinct performance regimes when the turbine is operated under relatively steady flow conditions. Operating at blade angles of attack below static stall, excellent agreement is achieved with two-dimensional wind tunnel data. Around the static stall angle, the cycle average normal force produced is greater than the static test data. Span locations near the hub produce extremely large values of normal force coefficient, well in excess of the two-dimensional data results. These performance regimes have been shown to be a function of the three-dimensional flow structure and cycle averaged dynamic stall effects. Power generation and root bending moments have also been shown to be directly dependent on the inflow wind velocity. Aerodynamic data, including episodes of dynamic stall, have been correlated on a cycle by cycle basis with the structural and power generation characteristics of a horizontal axis wind turbine. Instantaneous unsteady forces and resultant power generation indicate that peak transient levels can significantly exceed cycle averaged values. Strong coupling between transient aerodynamic and resonant response of the turbine was also observed. These results provide some initial insight into the contribution of unsteady aerodynamics on undesirable turbine structural response and fatigue life.

Shipley, D.E.; Miller, M.S.; Robinson, M.C.; Luttges, M.W. [Colorado Univ., Boulder, CO (United States). Dept. of Aerospace Engineering Sciences; Simms, D.A. [National Renewable Energy Lab., Golden, CO (United States)

1994-08-01

353

Evidence that aerodynamic effects, including dynamic stall, dictate HAWT structural loads and power generation in highly transient time frames  

NASA Astrophysics Data System (ADS)

Aerodynamic data collected from the National Renewable Energy Laboratory's Combined Experiment have shown three distinct performance regimes when the turbine is operated under relatively steady flow conditions. Operating at blade angles of attack below static stall, excellent agreement is achieved with two-dimensional wind tunnel data. Around the static stall angle, the cycle average normal force produced is greater than the static test data. Span locations near the hub produce extremely large values of normal force coefficient, well in excess of the two-dimensional data results. These performance regimes have been shown to be a function of the three-dimensional flow structure and cycle averaged dynamic stall effects. Power generation and root bending moments have also been shown to be directly dependent on the inflow wind velocity. Aerodynamic data, including episodes of dynamic stall, have been correlated on a cycle by cycle basis with the structural and power generation characteristics of a horizontal axis wind turbine. Instantaneous unsteady forces and resultant power generation indicate that peak transient levels can significantly exceed cycle averaged values. Strong coupling between transient aerodynamic and resonant response of the turbine was also observed. These results provide some initial insight into the contribution of unsteady aerodynamics on undesirable turbine structural response and fatigue life.

Shipley, D. E.; Miller, M. S.; Robinson, M. C.; Luttges, M. W.; Simms, D. A.

1994-08-01

354

A "TEST OF CONCEPT" COMPARISON OF AERODYNAMIC AND MECHANICAL RESUSPENSION MECHANISMS FOR PARTICLES DEPOSITED ON FIELD RYE GRASS (SECALS CERCELE). PART 2. THRESHOLD MECHANICAL ENERGIES FOR RESUSPENSION PARTICLE FLUXES  

EPA Science Inventory

Kinetic energy from the oscillatory impacts of the grass stalk against a stationary object was measured with a kinetic energy measuring device. These energy inputs were measured as part of a resuspension experiment of uniform latex microspheres deposited on a single rye grass see...

355

Aerodynamics support of research instrument development  

NASA Astrophysics Data System (ADS)

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

Miller, L. Scott

1990-09-01

356

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

National Technical Information Service (NTIS)

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

M. V. Cook F. Heydari

1985-01-01

357

Integrated lighting approach saves energy in post office facilities  

SciTech Connect

The United States Postal Service (USPS) has made numerous efforts to improve the lighting quality and efficiency in their facilities. These efforts have included both traditional retrofits such as the transition to T8 lamps/electronic ballasts and more experimental approaches such as light pipes and sulfur lamps. However, these efforts have focused primarily on their industrial and plant facilities and have had little impact on their small and medium sized facilities, which comprise roughly 90% of their total building stock. These efforts have also neglected the affinity between task and ambient lighting functions.The objective of this project was to develop and demonstrate an integrated lighting system that saves energy while improving the lighting distribution and quality in small and medium sized USPS facilities. Work included the evolution of a novel task lighting fixture designed explicitly to improve the light distribution within the carrier case letter sorting station. The new t ask light system was developed to work in combination with a high efficiency, low-glare ambient lighting system mounted on the ceiling. The use of high-performance task lighting allowed the ambient lighting component to be reduced, thereby limiting the amount of glare produced and reducing the amount of energy consumed.

Mitchell, Jeffrey C.; Siminovitch, Michael J.; Page, Eric R.; Gauna, Kevin W.; Avery, Douglas A.

2000-06-01

358

Aerodynamic parameters of across-wind self-limiting vibration for square sections after lock-in in smooth flow  

NASA Astrophysics Data System (ADS)

The paper aims to identify the across-wind aerodynamic parameters of two-dimensional square section structures after the lock-in stage from the response measurements of wind tunnel tests under smooth wind flow conditions. Firstly, a conceivable self-limiting model was selected from the existent literature and the revisit of the analytical solution shows that the aerodynamic parameters (linear and nonlinear aerodynamic dampings Y1 and ?, and aerodynamic stiffness Y2) are not only functions of the section shape and reduced wind velocity but also dependent on both the mass ratio (mr) and structural damping ratio (?) independently, rather than on the Scruton number as a whole. Secondly, the growth-to-resonance (GTR) method was adopted for identifying the aerodynamic parameters of four different square section models (DN1, DN2, DN3 and DN4) by varying the density ranging from 226 to 409 kg/m3. To improve the accuracy of the results, numerical optimization of the curve-fitting for experimental and analytical response in time domain was performed to finalize the results. The experimental results of the across-wind self-limiting steady-state amplitudes after lock-in stage versus the reduced wind velocity show that, except the tail part of the DN1 case slightly decreases indicating a pure vortex-induced lock-in persists, the DN2, DN3 and DN4 cases have a trend of monotonically increasing with the reduced wind velocity, which shows an asymptotic combination with the galloping behavior. Due to such a combination effect, all three aerodynamic parameters decrease as the reduced wind velocity increases and asymptotically approaches to a constant at the high branch. In the DN1 case, the parameters Y1 and Y2 decrease as the reduced wind velocity increases while the parameter ? slightly reverses in the tail part. The 3-dimensional surface plot of the Y1, ? and Y2 curves further show that, excluding the DN1 case, the parameters in the DN2, DN3 and DN4 cases almost follow a symmetric concave-up distribution versus the density under the same reduced wind velocity. This indicates that the aerodynamic parameters in the DN3 case are the minima along the density distribution.

Wu, Jong-Cheng; Chang, Feng-Jung

2011-08-01

359

Algorithm for determining the aerodynamic characteristics of a freely flying object from discrete data of ballistic experiment. Part 2  

NASA Astrophysics Data System (ADS)

In part 1 of this paper, an algorithm for numerically solving the inverse problem of motion of a solid through the atmosphere is described that constitutes the basis for identifying the aerodynamic characteristics of an object from trajectory data and the respective identification procedure is presented. In part 2, methods evaluating the significance of desired parameters and adequacy of a mathematical model of motion, approaches to metrological certification of experimental equipment, and results of testing the algorithm are discussed.

Bobashev, S. V.; Mende, N. P.; Popov, P. A.; Sakharov, V. A.; Berdnikov, V. A.; Viktorov, V. A.; Oseeva, S. I.; Sadchikov, G. D.

2009-04-01

360

Generating Particle Beams of Controlled Dimensions and Divergence: I. Theory of Particle Motion in Aerodynamic Lenses and Nozzle Expansions  

Microsoft Academic Search

A particle beam is produced when a particle-laden gas expands through a nozzle into a vacuum. This work discusses the theoretical basis of a novel method for producing highly collimated and tightly focused particle beams. The approach is to pass the particle-laden gas through a series of axisymmetric contractions and enlargements (so-called aerodynamic lenses) before the nozzle expansion. Particles are

Peng Liu; Paul J. Ziemann; David B. Kittelson; Peter H. McMurry

1995-01-01

361

Policy approaches to renewable energy investment in the Mediterranean region  

NASA Astrophysics Data System (ADS)

Europe's climate policy objective of 20% renewable energy by 2020, and the call by the IPCC to reduce greenhouse gas emissions by 80% by 2050, pose major challenges for the European Union. Several policy options are available to move towards these objectives. In this paper, we will address the most critical policy and governance issues associated with one particular approach to scaling up renewable energy resources: reliance on large-scale energy generation facilities outside the European continent, such as onshore and offshore wind farms and concentrating solar power (CSP) facilities in the Mediterranean region. Several feasibility studies completed over the past three years (German Aerospace Center 2006; German Aerospace Center 2005; Czisch, Elektrotechnik 2005, p. 488; Lorenz, Pinner, Seitz, McKinsey Quarterly 2008, p.10; German Aerospace Center 2005; Knies 2008, The Club of Rome; Khosla, Breaking the Climate Deadlock Briefing Papers, 2008, p.19) have convincingly demonstrated that large-scale wind and CSP projects ought to be very attractive for a number of reasons, including cost, reliability of power supply, and technological maturity. According to these studies it would be technically possible for Europe to rely on large-scale wind and CSP for the majority of its power needs by 2050—indeed enough to completely replace its reliance on fossil fuels for power generation—at competitive cost over its current, carbon intensive system. While it has been shown to be technically feasible to develop renewable resources in North Africa to account for a large share of Europe's energy needs, doing so would require sustained double digit rates of growth in generating and long-distance transmission capacity, and would potentially require a very different high voltage grid architecture within Europe. Doing so at a large scale could require enormous up-front investments in technical capacity, financial instruments and human resources. What are the policy instruments best suited to achieving such growth quickly and smoothly? What bottlenecks—in terms of supply chains, human capital, finance, and transmission capacity—need to be anticipated and addressed if the rate of capacity growth is to be sustained over several decades? What model of governance would create a safe investment climate in consistence with new EU legislation (i.e. EU Renewable Energy Directive) as well as expected post-Kyoto targets and mechanisms? The material that we present here is based on a series of workshops held between November 2008 and January 2009, in which a wide range of stakeholders expressed their views about the fundamental needs for policy intervention. Supplementing the results from these workshops have been additional expert interviews, and basic financial modeling. One of the interesting results from this research is the need for a multi-pronged approach. First, there is a need for a support scheme, potentially compatible with in all cases supplementing the EU REN Directive, that would create a stable market for North African electricity in Europe. Second, there is a need for policies that facilitate the formation of public private partnerships in North Africa, as the specific investment vehicle, as a way to manage some of the uncertainties associated with large-scale investments in the region. Third, attention has to be paid to the development of supply chains within the Mediterranean region, as a way of ensuring the compatibility of such investments with sustainable development.

Patt, A.; Komendantova, N.; Battaglini, A.; Lilliestam, J.; Williges, K.

2009-04-01

362

The streamlined site assessment methodology: A new approach for wind energy site assessment  

Microsoft Academic Search

This research develops superior approaches to the traditional site assessment process, as well as novel strategies that offer a distinct advantage over the traditional process. Two major contributions are presented: new analysis approaches for site assessment, and new technical approaches to wind resource monitoring. Two new analysis approaches for wind energy site assessment are developed. The first is a method

Matthew A. Lackner

2008-01-01

363

Measuring energy efficiency in economics: Shadow value approach  

Microsoft Academic Search

For decades, academic scholars and policy makers have commonly applied a simple average measure, energy intensity, for studying energy efficiency. In contrast, we introduce a distinctive marginal measure called energy shadow value (SV) for modeling energy efficiency drawn on economic theory. This thesis demonstrates energy SV advantages, conceptually and empirically, over the average measure recognizing marginal technical energy efficiency and

Asgar Khademvatani

2010-01-01

364

Aerodynamic performance of vertical and horizontal axis wind turbines  

NASA Astrophysics Data System (ADS)

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

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

1981-06-01

365

The unsteady aerodynamics of a first stage stator vane row  

NASA Astrophysics Data System (ADS)

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

Capece, V. R.; Fleeter, S.

1986-03-01

366

Aerodynamic gradient-based optimization using computational fluid dynamics and discrete sensitivities for practical problems  

NASA Astrophysics Data System (ADS)

A gradient-based shape optimization methodology based on quasi-analytical sensitivities has been developed for practical three-dimensional aerodynamic applications. The flow analysis has been rendered by a fully implicit, finite-volume formulation of the Euler and Thin Layer Navier-Stokes (TLNS) equations. The flow equations and aerodynamic sensitivity equation have been solved using an alternating-direction-implicit (ADI) algorithm for memory efficiency. A wing geometry model based on space-surface and planform parameterization has been utilized. The present methodology and its components have been tested via several comparisons. Initially, the inviscid flow analysis for a wing has been compared with those obtained using an unfactored, Preconditioned Conjugate Gradient (PCG) approach, and an independent Computational Fluid Dynamics (CFD) code which has been extensively validated. Then, the viscous laminar flow analysis for a wing has been compared with that obtained using again the extensively validated CFD code. Next, the sensitivities computed with the present method have been compared with those obtained using the finite-difference and the PCG approaches. Effects of convergence tolerance on the flowfield sensitivities have been shown. Also, effects of grid size and viscosity on the flow analysis, sensitivity analysis and the shape optimization have been established. Despite the expected increase in the computational time, the results indicate that shape optimization problems, which require large numbers of grid points, can be resolved with a gradient-based approach. The new procedure has been demonstrated in the design of a cranked arrow wing at Mach 2.4, with coarse and fine grid based computations performed with Euler and TLNS equations. The influence of the initial constraints on the geometry and aerodynamics of the optimized shape has been explored. Various final shapes generated for an identical initial problem formulation but with different optimization path options (coarse or fine grid, Euler or TLNS) have been aerodynamically evaluated via a common fine grid TLNS based analysis. The efficacy of these design options has been evaluated by comparing net performance improvement in tandem with the CPU time requirements. Results show that fluid dynamic and sensitivity analyses using ADI compare well with the PCG method and CFL3D code. The ADI method reduces the memory storage but increases the computing time as compared to the PCG method. It is demonstrated that the inherent larger size of optimization problems can be accommodated by using the ADI method. The presently developed optimization procedure is capable of learning aerodynamic lessons during the evolution of optimized shapes. Initial constraints conditions show significant bearing on the optimization results. Results demonstrate that to produce an aerodynamically efficient design, it is imperative to include viscous physics in the optimization procedure with proper resolution. However, if CPU time constraints do not permit this option, it is advantageous to incorporate inadequately resolved viscous flow physics in lieu of properly resolved inviscid flow physics. Based upon the present results, it is recommended that to better utilize computational resources, a number of viscous coarse grid cases using the PCG (preferably) or ADI method, should initially be explored to improve optimization problem definition, design space and initial shape. Optimized shapes should be analyzed using high fidelity (viscous fine grid resolution) flow analysis to evaluate their true performance potential. Subsequently, a viscous fine grid-based shape optimization should be conducted, using ADI method, to accurately obtain the final optimized shape.

Pandya, Mohagna Jayendrarai

367

March 1999 working group meeting on heavy vehicle aerodynamic drag: presentations and summary of comments and conclusions  

SciTech Connect

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory, Livermore, California on March 11, 1999. The purpose of the meeting was to present technical details on the experimental and computational plans and approaches and provide an update on progress in obtaining experimental results, model developments, and simulations. The focus of the meeting was a review of the experimental results for the integrated tractor-trailer benchmark geometry called the Sandia Model in the NASA Ames 7 ft x 10 ft wind tunnel. The present and projected budget and funding situation was also discussed. Presentations were given by representatives from the Department of Energy (DOE) Office of Transportation Technology Office of Heavy Vehicle Technology (OHVT), Lawrence Livermore National Laboratory (LLNL), Sandia National Laboratories (SNL), University of Southern California (USC), California Institute of Technology (Caltech), and NASA Ames Research Center.This report contains the technical presentations (viewgraphs) delivered at the Meeting, briefly summarizes the comments and conclusions, and outlines the future action items.

Brady, M; Browand, F; McCallen, R; Ross, J; Salari, K

1999-03-01

368

July 1999 working group meeting on heavy vehicle aerodynamic drag: presentations and summary of comments and conclusions  

SciTech Connect

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at University of Southern California, Los Angeles, California on July 30, 1999. The purpose of the meeting was to present technical details on the experimental and computational plans and approaches and provide an update on progress in obtaining experimental results, model developments, and simulations. The focus of the meeting was a review of University of Southern California's (USC) experimental plans and results and the computational results from Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories (SNL) for the integrated tractor-trailer benchmark geometry called the Sandia Model. Much of the meeting discussion involved the NASA Ames 7 ft x 10 ft wind tunnel tests and the need for documentation of the results. The present and projected budget and funding situation was also discussed. Presentations were given by representatives from the Department of Energy (DOE) Office of Transportation Technology Office of Heavy Vehicle Technology (OHVT), LLNL, SNL, USC, and California Institute of Technology (Caltech). This report contains the technical presentations (viewgraphs) delivered at the Meeting, briefly summarizes the comments and conclusions, and outlines the future action items.

Brady, M; Browand, F; Flowers, D; Hammache, M; Landreth, G; Leonard, A; McCallen, R; Ross, J; Rutledge, W; Salari, K

1999-08-16

369

A multi-paradigm modeling approach for energy systems analysis  

NASA Astrophysics Data System (ADS)

Energy plays a vital role in the world today, driving industry and allowing for technologies ingrained throughout the routines of daily life. The complex interactions, evolution, long time scales of change, and critical nature of the energy system makes modeling and analysis crucial to developing insight on how the evolution of energy systems can be shaped. What is needed is not the development of a uniform model, but a flexible, open framework that allows for the integration of existing and future models. The framework should be flexible to allow the evolution of the questions examined with the model and open to allow sub-model reuse and refinement. The multi-paradigm modeling framework presented here offers this capability. The goal of this modeling framework is to create a dynamic and flexible modeling environment that allows for the level of abstraction of each sub-system to differ and evolve, creating a model which can be used to evaluate how changes in one system can affect other linked systems at differing time-scales and levels of aggregation. The framework is particularly useful for modeling systems that are not yet fully defined due to the flexibility inherent in the approach and the concept of technology pipelines for modeling endogenous technological change has also been introduced to model technological progression. The introduction of PHEVs to the transportation system will provide a strong link between it and the electricity system, dramatically changing both systems. Before policies that regulate this transformational technology are enacted it is critical that the limits of the system are examined to prevent the propagation of unintended consequences. Detailed electricity supply and demand models have been developed and combined with a transportation simulator in order to gauge the impact of PHEV introduction on electricity load profiles and vehicle emissions. In addition, the ability of a complementary technology, vehicle-to-grid power systems, to aid in the integration of large amounts of wind power into the electricity system has been examined. Finally, since the intermittency of wind energy is the chief obstacle towards expanded wind power integration, statistical methods for wind forecasting over large geographic areas have been investigated.

Hodge, Bri-Mathias Scott

370

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

National Technical Information Service (NTIS)

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

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

1989-01-01

371

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

National Technical Information Service (NTIS)

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

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

1981-01-01

372

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

National Technical Information Service (NTIS)

The research investigates the effect of wind tunnel model system dynamics on measured aerodynamic data. During wind tunnel tests designed to obtain lift and drag data, the required aerodynamic measurements are the steady-state balance forces and moments, ...

R. D. Buehrle

1997-01-01

373

Aerodynamics of intermittent bounds in flying birds  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

374

Aerodynamics of intermittent bounds in flying birds  

NASA Astrophysics Data System (ADS)

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

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

375

Aerodynamic development of a lifting body launch vehicle  

SciTech Connect

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

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

1997-01-01

376

Aerodynamic-structural model of offwind yacht sails  

NASA Astrophysics Data System (ADS)

An aerodynamic-structural model of offwind yacht sails was created that is useful in predicting sail forces. Two sails were examined experimentally and computationally at several wind angles to explore a variety of flow regimes. The accuracy of the numerical solutions was measured by comparing to experimental results. The two sails examined were a Code 0 and a reaching asymmetric spinnaker. During experiment, balance, wake, and sail shape data were recorded for both sails in various configurations. Two computational steps were used to evaluate the computational model. First, an aerodynamic flow model that includes viscosity effects was used to examine the experimental flying shapes that were recorded. Second, the aerodynamic model was combined with a nonlinear, structural, finite element analysis (FEA) model. The aerodynamic and structural models were used iteratively to predict final flying shapes of offwind sails, starting with the design shapes. The Code 0 has relatively low camber and is used at small angles of attack. It was examined experimentally and computationally at a single angle of attack in two trim configurations, a baseline and overtrimmed setting. Experimentally, the Code 0 was stable and maintained large flow attachment regions. The digitized flying shapes from experiment were examined in the aerodynamic model. Force area predictions matched experimental results well. When the aerodynamic-structural tool was employed, the predictive capability was slightly worse. The reaching asymmetric spinnaker has higher camber and operates at higher angles of attack than the Code 0. Experimentally and computationally, it was examined at two angles of attack. Like the Code 0, at each wind angle, baseline and overtrimmed settings were examined. Experimentally, sail oscillations and large flow detachment regions were encountered. The computational analysis began by examining the experimental flying shapes in the aerodynamic model. In the baseline setting, the computational force predictions were fair at both wind angles examined. Force predictions were much improved in the overtrimmed setting when the sail was highly stalled and more stable. The same trends in force prediction were seen when employing the aerodynamic-structural model. Predictions were good to fair in the baseline setting but improved in the overtrimmed configuration.

Mairs, Christopher M.

377

Aerodynamics of Dragonfly in Hover: Force measurements and PIV results  

NASA Astrophysics Data System (ADS)

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

Deng, Xinyan; Hu, Zheng

2009-11-01

378

Approaches to Teaching Energy. Energy and Ourselves/Energy for the Consumer. Children's Learning in Science Project.  

ERIC Educational Resources Information Center

During the period 1984-1986, over 30 teachers from the Yorkshire (England) region have worked in collaboration with the Children's Learning in Science Project (CLIS) developing and testing teaching schemes in the areas of energy, particle theory, and plant nutrition. The project is based upon the constructivist approach to teaching. This guide…

Leeds Univ. (England). Centre for Studies in Science and Mathematics Education.

379

Analysis of the Aerodynamic Orbital Transfer Capabilities of a Winged Re-Entry Vehicle  

NASA Astrophysics Data System (ADS)

The ability to perform an inclination change maximizes the maneuverability of an orbiting space vehicle. Most maneuvers utilize a combined plane change and orbital transfer to the new orbit. This costs more in terms of energy and fuel than an in-plane change of orbits. The amount of DeltaV and fuel required for such an energy-intensive inclination change exceeds the benefit of performing the maneuver. However, this paper demonstrates that a winged re-entry vehicle, based on the currently proposed X-3 7, has the necessary thrust to change planes and then perform an in-plane transfer to achieve a new orbit. Using SIMULINKTM and LABVIEW simulation tools, this research found that the use of the aerodynamic lift of a winged re-entry vehicle produced more than 120 of inclination change with the minimal DeltaV achievable. Through small orbital maneuvers and atmospheric re-entry, the aerodynamics of the lift vector demonstrated that the spacecraft retained sufficient energy to prevent perigee collapse using an orbital regulation code to control throttle selling.

Pienkowski, John P.

2002-09-01

380

Multiscale approaches for studying energy transduction in dynein  

PubMed Central

Cytoplasmic dynein is an important motor that drives all minus-end directed movement along microtubules. Dynein is a complex motor whose processive motion is driven by ATP-hydrolysis. Dynein's run length has been measured to be several millimetres with typical velocities in the order of a few nanometres per second. Therefore, the average time between steps is a fraction of a second. When this time scale is compared with typical time scales for protein side chain and backbone movements (~10?9 s and ~10?5 s, respectively), it becomes clear that a multi-timescale modelling approach is required to understand energy transduction in this protein. Here, we review recent efforts to use computational and mathematical modelling to understand various aspects of dynein's chemomechanical cycle. First, we describe a structural model of dynein's motor unit showing a heptameric organization of the motor subunits. Second, we describe our molecular dynamics simulations of the motor unit that are used to investigate the dynamics of the various motor domains. Third, we present a kinetic model of the coordination between the two dynein heads. Lastly, we investigate the various potential geometries of the dimer during its hydrolytic and stepping cycle.

Serohijos, Adrian W. R.; Tsygankov, Denis; Liu, Shubin; Elston, Timothy C.; Dokholyan, Nikolay V.

2010-01-01

381

Approaching chemical accuracy with density functional calculations: Diatomic energy corrections  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) is widely used to predict materials properties, but the local density approximation (LDA) and generalized gradient approximation (GGA) exchange-correlation functionals are known to poorly predict the energetics of reactions involving molecular species. In this paper, we obtain corrections for the O2, H2, N2, F2, and Cl2 molecules within the Perdew-Burke-Enzerhof GGA, Perdew-Wang GGA, and Perdew-Zunger LDA exchange-correlation functionals by comparing DFT-calculated formation energies of oxides, hydrides, nitrides, fluorides, and chlorides to experimental values. We also show that the choice of compounds used to obtain the correction is significant, and we use a leave-one-out cross-validation approach to rigorously determine the proper fit set. We report confidence intervals with our correction values, which quantifies the variation caused by the choice of fit set after outlier removal. The remaining variation in the correction values is of the order of 1 kcal/mol, which indicates that chemical accuracy is a realistic goal for these systems.

Grindy, Scott; Meredig, Bryce; Kirklin, Scott; Saal, James E.; Wolverton, C.

2013-02-01

382

Wing motion measurement and aerodynamics of hovering true hoverflies.  

PubMed

Most hovering insects flap their wings in a horizontal plane (body having a large angle from the horizontal), called `normal hovering'. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane (body being approximately horizontal). In the present paper, wing and body kinematics of four freely hovering true hoverflies were measured using three-dimensional high-speed video. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic forces of the insects. The stroke amplitude of the hoverflies was relatively small, ranging from 65 to 85 deg, compared with that of normal hovering. The angle of attack in the downstroke (?50 deg) was much larger that in the upstroke (?20 deg), unlike normal-hovering insects, whose downstroke and upstroke angles of attack are not very different. The major part of the weight-supporting force (approximately 86%) was produced in the downstroke and it was contributed by both the lift and the drag of the wing, unlike the normal-hovering case in which the weight-supporting force is approximately equally contributed by the two half-strokes and the lift principle is mainly used to produce the force. The mass-specific power was 38.59-46.3 and 27.5-35.4 W kg(-1) in the cases of 0 and 100% elastic energy storage, respectively. Comparisons with previously published results of a normal-hovering true hoverfly and with results obtained by artificially making the insects' stroke planes horizontal show that for the true hoverflies, the power requirement for inclined stroke-plane hover is only a little (<10%) larger than that of normal hovering. PMID:21832126

Mou, Xiao Lei; Liu, Yan Peng; Sun, Mao

2011-09-01

383

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

Microsoft Academic Search

A basic problem in flight dynamics is the mathematical formulation of the aerodynamic model for aircraft. This study is part of an ongoing effort at NASA Langley to develop a more general formulation of the aerodynamic model for aircraft that includes nonlinear unsteady aerodynamics and to develop appropriate test techniques that facilitate identification of these models. A methodology for modeling

Patrick C. Murphy; Vladislav Klein

384

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

Microsoft Academic Search

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

Ilhan Bayraktar

2002-01-01

385

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

Microsoft Academic Search

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

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

386

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

Microsoft Academic Search

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

B. F. Mettler

2010-01-01

387

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

Microsoft Academic Search

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

Koji Shimoyama; Akira Oyama; Kozo Fujii

388

A 'Reference Building' Approach to Building Energy Performance Standards for Single-Family Residences.  

National Technical Information Service (NTIS)

A reference building approach to building energy performance standards (BEPS) is described in this report which could serve as a framework for the further development of energy standards for new single-family residences. Each proposed new building design ...

S. R. Petersen J. L. Heldenbrand

1980-01-01

389

Residential energy conservation outreach activities: A new federal approach  

NASA Astrophysics Data System (ADS)

An evaluation of the Department of Energy's residential energy conservation outreach activities is presented. The contribution that outreach can make in achieving energy conservation is examined. The effectiveness of alternative techniques and DOE's current program and management are also examined.

1981-02-01

390

Theoretical and Experimental Evaluation of Aerodynamic Lenses for Producing Particle Beams of Controlled Dimensions and Divergence.  

NASA Astrophysics Data System (ADS)

A particle beam is produced when a particle-laden gas expands through a nozzle into a vacuum. This work discusses a method of producing very narrow and highly collimated particle beams. The approach is to pass the particle-laden gas through a series of axisymmetric contractions and enlargements (so called aerodynamic lenses) before the nozzle expansion. Particles are confined closely to the axis alter passing through these lenses. Since particles close to the axis experience small radial drag forces, they stay close to the axis during nozzle expansion and therefore form a narrow particle beam downstream. The major effects that limit the minimum beam width are Brownian motion and lift forces on particles during nozzle expansion. Lift -force effects often occur for non-spherical particles and are often greater than Brownian-motion effects. A particle -beam-forming apparatus consisting of a variable number of lenses in series followed by an accelerating nozzle was developed for the application in a Particle Beam Mass Spectrometer (PBMS). This instrument is to measure ultrafine particles (0.01 ~ 0.5 murm m) in low pressure (>= 0.1 torr) environments such as those in semiconductor processing equipment. The experimental evaluations showed that as more lenses were added the particle beam widths were reduced asymptotically to the minimum values. For spherical particles these minimum values are in good agreement with those predicted from a Brownian-motion model. For non-spherical particles these minimum widths are often much larger than the Brownian limit, which is consistent with theoretical predictions based on lift forces. A Low -Pressure Laser Particle Detector (LPLPD) using aerodynamic lenses was also developed and evaluated in this work. Because of its high particle counting efficiencies (~ 100%) and small flow resistance, it is suitable for detecting particles in exhaust lines of semiconductor processing equipment. This work demonstrates that aerodynamic lenses are an effective means for separating particles from a carrier gas and confining them to the centerline of symmetric flows.

Liu, Peng

391

Aerodynamic Characteristics of Flapping Motion of a Two- Dimensional Wing Model Shaped Like a Dragonfly Wing Section  

NASA Astrophysics Data System (ADS)

This paper describes the aerodynamic characteristics of the flapping motion of a dragonfly wing model. The orbit and feathering angle of a dragonfly wing were measured using a high-speed video camera. The measurement data was used to formulate two mathematical models: linear and Fourier models. The aerodynamic characteristics of a thin plate and dragonfly wing models, which were investigated using a numerical simulation, revealed that the linear model generated a high vertical force during descent and high thrust force during ascent. Although the Fourier model could not generate a high thrust force during ascent, it generated a higher vertical force than the linear model. During the flapping motion in both the models, a marginal difference was observed between the forces generated at the top and bottom. When the feathering angle approached the stroke angle, the resultant force direction acting on the wing models was reversed.

Tsuyuki, Koji; Sudo, Seiichi; Igarashi, Saburo

392

A statistical approach linking energy management to maintenance and production factors  

Microsoft Academic Search

This research has addressed a quantitative approach for improving energy management through applying statistical techniques aimed at identifying and controlling factors linked to energy consumption rates at manufacturing plants. The paper presents analysis and results of multiple linear regression models used to establish the significance of a number of energy related management factors in controlling energy usage. Regression models constructed

Amjed Al-Ghanim

2003-01-01

393

An integrated renewable energy park approach for algal biofuel production in United States  

Microsoft Academic Search

Algal biomass provides viable third generation feedstock for liquid transportation fuel that does not compete with food crops for cropland. However, fossil energy inputs and intensive water usage diminishes the positive aspects of algal energy production. An integrated renewable energy park (IREP) approach is proposed for aligning renewable energy industries in resource-specific regions in United States for synergistic electricity and

Bobban Subhadra; Mark Edwards

2010-01-01

394

Optimization of Flight Test Maneuvers for Aerodynamic Derivatives Inverse Problem  

Microsoft Academic Search

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

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

395

Aerodynamic aspects on recovery of sounding rocket payload  

Microsoft Academic Search

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

M. Shirouzu; H. Kubota; Y. Shibato

1980-01-01

396

Numerical Analysis on Aerodynamic Forces on Wiper System  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

397

ON AERODYNAMIC AND BOUNDARY LAYER RESISTANCES WITHIN DRY DEPOSITION MODELS  

EPA Science Inventory

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

398

Passive flow control by membrane wings for aerodynamic benefit  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

399

Aerodynamic analysis of a Mars exploration manned capsule  

NASA Astrophysics Data System (ADS)

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

Pezzella, Giuseppe; Viviani, Antonio

2011-12-01

400

Laryngeal Aerodynamics Associated with Oral Contraceptive Use: Preliminary Findings  

ERIC Educational Resources Information Center

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

Gorham-Rowan, Mary; Fowler, Linda

2009-01-01

401

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

NASA Astrophysics Data System (ADS)

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

Liu, Hao

2009-02-01

402

Aerodynamic Analysis of a General Purpose Tow Target.  

National Technical Information Service (NTIS)

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

J. B. Smith

1974-01-01

403

Aerodynamic Analysis of a Profile Fighter Tow Target.  

National Technical Information Service (NTIS)

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

J. B. Smith

1974-01-01

404

Unsteady Aerodynamic Flow Control of a Suspended Axisymmetric Moving Platform  

NASA Astrophysics Data System (ADS)

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

Lambert, Thomas; Vukasinovic, Bojan; Glezer, Ari

2011-11-01

405

Aerodynamic design optimization using sensitivity analysis and computational fluid dynamics  

NASA Astrophysics Data System (ADS)

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

Baysal, Oktay; Eleshaky, Mohamad E.

1992-01-01

406

Aerodynamic design optimization using sensitivity analysis and computational fluid dynamics  

Microsoft Academic Search

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

Oktay Baysal; Mohamad E. Eleshaky

1992-01-01

407

Low Speed Aerodynamics of the X-38 CRV.  

National Technical Information Service (NTIS)

This project was performed in support of the engineering development of the NASA X-38 Crew Return Vehicle (CRV)system. Wind tunnel experiments were used to visualize various aerodynamic phenomena encountered by the CRV during the final stages of descent a...

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

1998-01-01

408

Unsteady Free-Wake Viscous Aerodynamic Analysis of Helicopter Rotors.  

National Technical Information Service (NTIS)

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

L. Morino M. Downey S. Sipcic

1989-01-01

409

Mesh Modification Strategy for Aerodynamic Design through Evolution  

Microsoft Academic Search

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

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

2007-01-01

410

Aerodynamic Characteristics of Fan-Jet STOL Aircraft.  

National Technical Information Service (NTIS)

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

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

1983-01-01

411

Prediction of Transient Aerodynamic Inputs on Passenger Cars,  

National Technical Information Service (NTIS)

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

H. Takada I. Kohri K. Harigane

1988-01-01

412

Tracheal and central bronchial aerodynamics using virtual bronchoscopy  

NASA Astrophysics Data System (ADS)

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

Summers, Ronald M.; Cebral, Juan R.

2001-05-01

413

Aerodynamic Design of First Stage Turbines for Small Aero Engines.  

National Technical Information Service (NTIS)

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

U. Okapuu

1987-01-01

414

In-Flight Aerodynamic Measurements of an Iced Horizontal Tailplane.  

National Technical Information Service (NTIS)

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

T. P. Ratvasky J. F. VanZante

1999-01-01

415

Aerodynamic forces of revolving hummingbird wings and wing models  

Microsoft Academic Search

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

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

2004-01-01

416

Aerodynamic analysis of a Mars exploration manned capsule  

Microsoft Academic Search

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

Giuseppe Pezzella; Antonio Viviani

2011-01-01

417

Aerodynamic calculational methods for curved-blade Darrieus VAWT WECS  

Microsoft Academic Search

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

R. J. Templin

1985-01-01

418

Aerodynamic Characteristics of Telescopic Aerospikes with Multiple-Row-Disk  

Microsoft Academic Search

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

Hiroaki Kobayashi; Yusuke Maru; Tetsuya Sato

2007-01-01

419

Take-off and Aerodynamic Characteristics of a Taketombo  

Microsoft Academic Search

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

Kunio Yasuda

2008-01-01

420

Improvement in Aerodynamic Characteristics of a Paraglider Wing Canopy  

Microsoft Academic Search

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

Mohammad Mashud; Akira Umemura

2006-01-01

421

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

Microsoft Academic Search

The present work investigates the aerodynamics, dynamics and emissions of a Single Cup Combustor Sector. The Combustor resembles a real Gas Turbine Combustor with primary, secondary and dilution zones (also known as fuel rich dome combustor). The research is initiated by studying the effect of the combustor front end geometry on the flow field. Two different exit configurations (one causes

Bassam Sabry Mohammad

2010-01-01

422

Prediction of Unsteady Aerodynamic Coefficients at High Angles of Attack.  

National Technical Information Service (NTIS)

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

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

2001-01-01

423

Aerodynamic Drag Reduction Apparatus For Wheeled Vehicles In Ground Effect  

DOEpatents

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

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

2005-12-13

424

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

National Technical Information Service (NTIS)

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

S. K. Ibrahim

1965-01-01

425

Experimental aerodynamic characteristics of missiles with square cross sections  

Microsoft Academic Search

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

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

1983-01-01

426

Some aerodynamic aspects of engine secondary air systems  

Microsoft Academic Search

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

H. Zimmermann

1989-01-01

427

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

Microsoft Academic Search

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

Ulla M. Norberg

1972-01-01

428

Aerodynamic isotope separation processes for uranium enrichment: process requirements  

Microsoft Academic Search

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

Malling; G. F. Von Halle

1976-01-01

429

Fine particle counting with aerodynamic particle focusing and corona charging  

Microsoft Academic Search

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

Z. C. Tan; A. S. Wexler

2007-01-01

430

Historical view of long-span bridge aerodynamics  

Microsoft Academic Search

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

Toshio Miyata

2003-01-01

431

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

National Technical Information Service (NTIS)

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

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

2005-01-01

432

Economics of Railroad Automobile Rack Car Aerodynamic Drag.  

National Technical Information Service (NTIS)

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

R. W. Luebke

1969-01-01

433

System identification technology for estimating reentry vehicle aerodynamic coefficients  

Microsoft Academic Search

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

Narendra K. Gupta; W. Earl Hall

1977-01-01

434

CFD based unsteady aerodynamic modeling for rotor aeroelastic analysis  

Microsoft Academic Search

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

Jayanarayanan Sitaraman

2003-01-01

435

Aerodynamic Performances of Corrugated Dragonfly Wings at Low Reynolds Numbers  

Microsoft Academic Search

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

Masatoshi Tamai; Guowei He; Hui Hu

2006-01-01

436

Simplified dragonfly airfoil aerodynamics at Reynolds numbers below 8000  

Microsoft Academic Search

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

David-Elie Levy; Avraham Seifert

2009-01-01

437

Advancements in adaptive aerodynamic technologies for airfoils and wings  

Microsoft Academic Search

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

Jeffrey Keith Jepson

2006-01-01

438

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

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

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

439

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

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

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

440

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

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

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

441

Evaluation of thermographic phosphor technology for aerodynamic model testing  

SciTech Connect

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

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

1990-08-01

442

Aerodynamic evaluation of two compact radial-inflow turbine rotors  

Microsoft Academic Search

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

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

1995-01-01

443

Aerodynamics and flight performance of flapping wing micro air vehicles  

NASA Astrophysics Data System (ADS)

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

Silin, Dmytro

444

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

Microsoft Academic Search

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

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

1989-01-01

445

Take-off and Aerodynamic Characteristics of a Taketombo  

NASA Astrophysics Data System (ADS)

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

Yasuda, Kunio

446

Dark matter and dark energy: approaches and constraints  

NASA Astrophysics Data System (ADS)

We will introduce problems of Dark Matter (DM) and Dark Energy (DE), namely we will describe a development of these concepts and their present status. We will demonstrate ap-proaches to these problems. As specific issues we will discuss limits on DM concentration near the black hole at the Galactic Center and ways to solve DE problem introducing alternative theories of gravity such as f (R)-theories. The existence of dark matter (DM) at scales of few pc down to 10-5 pc around the centers of galaxies and in particular in the Galactic Center region has been considered in the literature. Under the assumption that such a DM clump, principally constituted by non-baryonic matter (like WIMPs) does exist at the center of our galaxy, the study of the ?-ray emission from the Galactic Center region allows us to constrain both the mass and the size of this DM sphere. Moreover, if a DM cusp does exist around the Galactic Center it could modify the trajectories of stars moving around it in a sensible way depending on the DM mass distribution. Here, we discuss the constraints that can be obtained with the orbit analysis of stars (as S2 and S16) moving inside the DM concentration with present and next generations of large telescopes. In particular, consideration of the S2 star apoastron shift may allow improving limits on the DM mass and size. We will describe severe constraints from Solar system data on parameters f (R) = Rn theories, where n = 1 corresponds to the standard general relativistic case. 1. A. F. Zakharov, A.A. Nucita, F. De Paolis, G. Ingrosso: Solar system constraints on Rn gravity, Phys. Rev. D 74, 107101, (2006). 2. A. F. Zakharov, A.A. Nucita, F. De Paolis, G. Ingrosso: Apoastron shift constraints on dark matter distribution at the Galactic Center, Phys. Rev. D 76, 062001, (2007). 3. A.F. Zakharov, S. Capozziello, F. De Paolis, G. Ingrosso, A.A. Nucita, The Role of Dark Matter and Dark Energy in Cosmological Models: Theoretical Overview, Space Sci. Rev. 148, 301-313(2009).

Zakharov, Alexander

447

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

SciTech Connect

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

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

1982-01-01

448

Investigation of the transient aerodynamic phenomena associated with passing manoeuvres  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

449

Optimal energy restoration in radial distribution systems using a genetic approach and graph chain representation  

Microsoft Academic Search

Several approaches have been developed to restore energy in distribution systems after the interruption of services for part of the system. In order to achieve the energy restoration plan, these approaches usually perform the restoration for circuits with specific features. Additionally, they are not able to deal with large outage zones. This paper develops a method using Genetic algorithms for

A. C. B. Delbem; A. de Carvalho; N. G. Bretas

2003-01-01

450

a Renormalized Hvt Approach and Energies of a Lambda-PARTICLE in Hypernuclei  

Microsoft Academic Search

An investigation is carried out to consider a renormalized quantum mechanical HVT approach in the context of s-power series expansions for the Schrödinger energy eigenvalues of a particle moving in a central potential well belonging to a fairly wide class of potential wells. This approach is designed and applied in detail to estimate energies of a Lambda in hypernuclei. The

C. A. Efthimiou; M. E. Grypeos; C. G. Koutroulos; K. J. Oyewumi; Th. Petridou

2011-01-01

451

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

452

Energy in physical planning: an approach to calculating energy requirements for heating, transportation and other forms of infrastructure  

SciTech Connect

An approach to calculating energy requirements for heating, transportation and other forms of infrastructure a method is presented for making tentative calculations on the use of energy in various physical structures. A series of cases which indicate how the energy consumption in a given area can be determined and provide basic data for various planning and decision-making situations.

Lamm, J.; Nielsen, B.; Wennerhag, P.

1982-01-01

453

An energy conservation approach to adsorbate-induced surface stress and the extraction of binding energy using nanomechanics  

Microsoft Academic Search

Surface stress induced by molecular adsorption in three different binding processes has been studied experimentally using a microcantilever sensor. A comprehensive free-energy analysis based on an energy conservation approach is proposed to explain the experimental observations. We show that when guest molecules bind to atoms\\/molecules on a microcantilever surface, the released binding energy is retained in the host surface, leading

Lal A. Pinnaduwage; Vassil I. Boiadjiev; John E. Hawk; Anthony C. Gehl; Gayanath W. Fernando; L. C. Rohana Wijewardhana

2008-01-01

454

Renewable Energy Technology and Path Creation: A Multi-scalar Approach to Energy Transition in the UK  

Microsoft Academic Search

This paper examines the potential contribution of UK regions for developing and deploying renewable energy technologies to achieve the government target of obtaining 20% of its energy from renewable sources by 2020. The paper argues for a multi-scalar approach to energy transition theory and policy. National-scale processes and policies need to be complemented by regional and local policies in order

Jürgen Essletzbichler

2012-01-01

455

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

Microsoft Academic Search

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

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

456

Energy Conservation in Industry; The Present Approach, The Future Opportunities.  

National Technical Information Service (NTIS)

Possible opportunities for industry to conserve energy through the introduction of new technology are considered. These new technology options may offer far greater savings of energy and of all other resources required in production than modifying the ope...

C. A. Berg

1979-01-01

457

The energy balance of the earth' surface : a practical approach  

Microsoft Academic Search

This study is devoted to the energy balance of the earth's surface with a special emphasis on practical applications. A simple picture of the energy exchange processes that take place at the ground is the following. Per unit time and area an amount of radiant energy is supplied to the surface. This radiation originates partly from the sun, but an~

Bruin de H. A. R

1982-01-01

458

Regulatory and voluntary approaches for enhancing building energy efficiency  

Microsoft Academic Search

Buildings are the dominant energy consumers in modern cities but their consumption can be largely cut back through improving efficiency, which is an effective means to lessen greenhouse gas emissions and slow down depletion of non-renewable energy resources. However, the potential energy cost saving alone is hardly a sufficient incentive to investing into improvement measures, unless the cost of using

W. L. Lee; F. W. H. Yik

2004-01-01

459

Method for multiaxial fatigue life prediction using energy approaches.  

National Technical Information Service (NTIS)

Fatigue criteria based on the concept of damage energy have been proposed and evaluated with experimental fatigue data generated under uniaxial as well as biaxial loading conditions. Most of the energy-based methods utilize plastic energy of stress-strain...

K. C. Liu

1991-01-01

460

Game-theory approach to consumer incentives for solar energy  

Microsoft Academic Search

Solar energy is currently not competitive with fossil fuels. Fossil fuel price increases may eventually allow solar to compete, but incentives can change the relative price between fossil fuel and solar energy, and make solar compete sooner. Examples are developed of a new type of competitive game using solar energy incentives. Competitive games must have players with individual controls and

J. K. Sharp

1981-01-01

461

Energy modelling for technology assessment: the MARKAL approach  

Microsoft Academic Search

The primary objective of energy policy in many countries is to change the structure of their energy systems so as to reduce the dependence on imported oil. A large amount of funds is spent on energy research and development. The technologies competing for such funds have widely varying characteristics. These relate to costs and benefits, technical performance, environmental effects, the

Stefan Rath-Nagel; Kenneth Stocks

1982-01-01

462

Rocket-borne Ion Mass Spectrometer for the Mesosphere That is Pumped by Rocket Aerodynamics  

NASA Astrophysics Data System (ADS)

The mesospheric region close to the mesopause is populated by electrons, ions and aerosol particles. The number density of aerosol particles may exceed that of the background plasma creating conditions where the free electron density is reduced. Understanding the full charge balance of the region requires the simultaneous detection of electrons, charged aerosol particles and ions. Rocket borne instruments for the measurement of electrons and aerosols are readily available. Mass spectrometers for ions have been flown that were evacuated by cryogenic vacuum pumps with liquid helium or neon. There have not been flights since 1993 because these instruments required expensive deliveries of cryogens and frequent refilling. Advances in (1) aerodynamic modeling, (2) mass spectrometer design, and (3) ion detection technology make possible a new approach to mass spectrometry in the mesosphere in which the spectrometer is pumped by the flow around the rocket. A miniature Rotating Field Mass Analyzer (RFMS) is presented that is suitable for the measurement of ions in from 70 km upward. RFMS has a 2 x 2 x 20 mm3 velocity selection cell and utilizes and advanced ion detector that is capable of single ions operation mode at these altitudes. The instrument is pumped by the aerodynamic effect of the supersonic payload. A prototype version of RFMS is under laboratory testing.

Sternovsky, Zoltan; Smith, Steven; Robertson, Scott

463

Newton-Krylov-Schwarz methods for aerodynamics problems : compressible and incompressible flows on unstructured grids.  

SciTech Connect

We review and extend to the compressible regime an earlier parallelization of an implicit incompressible unstructured Euler code [9], and solve for flow over an M6 wing in subsonic, transonic, and supersonic regimes. While the parallelization philosophy of the compressible case is identical to the incompressible, we focus here on the nonlinear and linear convergence rates, which vary in different physical regimes, and on comparing the performance of currently important computational platforms. Multiple-scale problems should be marched out at desired accuracy limits, and not held hostage to often more stringent explicit stability limits. In the context of inviscid aerodynamics, this means evolving transient computations on the scale of the convective transit time, rather than the acoustic transit time, or solving steady-state problems with local CFL numbers approaching infinity. Whether time-accurate or steady, we employ Newton's method on each (pseudo-) timestep. The coupling of analysis with design in aerodynamic practice is another motivation for implicitness. Design processes that make use of sensitivity derivatives and the Hessian matrix require operations with the Jacobian matrix of the state constraints (i.e., of the governing PDE system); if the Jacobian is available for design, it may be employed with advantage in a nonlinearly implicit analysis, as well.

Kaushik, D. K.; Keyes, D. E.; Smith, B. F.

1999-02-24

464

Ambient aerodynamic ionization source for remote analyte sampling and mass spectrometric analysis.  

PubMed

The use of aerodynamic devices in ambient ionization source development has become increasingly prevalent in the field of mass spectrometry. In this study, an air ejector has been constructed from inexpensive, commercially available components to incorporate an electrospray ionization emitter within the exhaust jet of the device. This novel aerodynamic device, herein termed remote analyte sampling, transport, and ionization relay (RASTIR) was used to remotely sample neutral species in the ambient and entrain them into an electrospray plume where they were subsequently ionized and detected using a linear ion trap Fourier transform mass spectrometer. Two sets of experiments were performed in the ambient environment to demonstrate the device's utility. The first involved the remote (approximately 1 ft) vacuum collection of pure sample particulates (i.e., dry powder) from a glass slide, entrainment and ionization at the ESI emitter, and mass spectrometric detection. The second experiment involved the capture (vacuum collection) of matrix-assisted laser desorbed proteins followed by entrainment in the ESI emitter plume, multiple charging, and mass spectrometric detection. This approach is in principle a RASTIR-assisted matrix-assisted laser desorption electrospray ionization source (Sampson, J. S.; Hawkridge, A. M.; Muddiman, D. C. J. Am. Soc. Mass Spectrom. 2006, 17, 1712-1716; Rapid Commun. Mass Spectrom. 2007, 21, 1150-1154.). A detailed description of the device construction, operational parameters, and preliminary small molecule and protein data are presented. PMID:18529018

Dixon, R Brent; Sampson, Jason S; Hawkridge, Adam M; Muddiman, David C

2008-06-05

465

Computationally fast harmonic balance methods for unsteady aerodynamic predictions of helicopter rotors  

NASA Astrophysics Data System (ADS)

A harmonic balance technique for the analysis of unsteady flows about helicopter rotors in forward flight and hover is presented in this paper. The aerodynamics of forward flight are highly nonlinear, with transonic flow on the advancing blade, subsonic flow on the retreating blade, and stalled flow over the inner portion of the rotor. Nevertheless, the unsteady flow is essentially periodic in time making it well suited for frequency domain analysis. The present method uses periodic boundary conditions that allows one to model the flow field on a computational grid around a single helicopter blade, no matter the actual blade count. Using this approach, we compute several solutions, each one corresponding to one of several instants in time over one period. These time levels are coupled to each other through a spectral time derivative operator in the interior of the computational domain and through the far-field and periodic boundary conditions around the boundary of the domain. In this paper, we apply the method to the three-dimensional Euler equations (although the method can also be applied to three-dimensional viscous flows), and examine the steady and unsteady aerodynamics about wings and rotors.

Ekici, Kivanc; Hall, Kenneth C.; Dowell, Earl H.

2008-06-01

466

Non-intrusive aerodynamic loads analysis of an aircraft propeller blade  

NASA Astrophysics Data System (ADS)

The flow field in a cross-sectional plane of a scaled Beaver DHC aircraft propeller has been measured by means of a stereoscopic PIV setup. Phase-locked measurements are obtained in a rotational frequency range from 18,900 to 21,000 rpm, at a relative Mach number of 0.6 at ¾ propeller radius. The use of an adapted formulation of the momentum equation in differential form for rotating frame of references, integrated with isentropic relations as boundary conditions, allowed to compute the pressure field around the blade and the surface pressure distribution directly from the velocity data in the compressible regime. The procedure, extended to the computation of the aerodynamic lift and drag coefficients by a momentum contour integral approach, proved to be able to couple the aerodynamical loads to the flow field on the moving propeller blade, comparing favorably with a numerical simulation of the entire scaled model. Results are presented for two propeller rotation speeds and three different yawing angles.

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

2011-08-01

467

A novel approach to assess post-yield energy dissipation of bone in tension  

Microsoft Academic Search

In this study, we proposed a novel approach to assess the energy dissipation during the post-yield deformation of bone. Based on the stress–strain behavior in an incremental and cyclic loading–unloading–reloading scheme in uniaxial tension, we partitioned the post-yield energy dissipation of bone into three distinct pathways: released elastic strain energy (Uer); irreversible energy (Ui); and hysteresis energy (Uh). Among them,

Xiaodu Wang; Jeffry S. Nyman

2007-01-01

468

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

PubMed

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

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

2012-08-01

469

Aerodynamic roughness length estimation from very high-resolution imaging LIDAR observations over the Heihe basin in China  

NASA Astrophysics Data System (ADS)

Roughness length of land surfaces is an essential variable for the parameterisation of momentum and heat exchanges. The growing interest in the estimation of the surface turbulent flux parameterisation from passive remote sensing leads to an increasing development of models, and the common use of simple semi-empirical formulations to estimate surface roughness. Over complex surface land cover, these approaches would benefit from the combined use of passive remote sensing and land surface structure measurements from Light Detection And Ranging (LIDAR) techniques. Following early studies based on LIDAR profile data, this paper explores the use of imaging LIDAR measurements for the estimation of the aerodynamic roughness length over a heterogeneous landscape of the Heihe river basin, a typical inland river basin in the northwest of China. The point cloud obtained from multiple flight passes over an irrigated farmland area were used to separate the land surface topography and the vegetation canopy into a Digital Elevation Model (DEM) and a Digital Surface Model (DSM) respectively. These two models were then incorporated in two approaches: (i) a strictly geometrical approach based on the calculation of the plan surface density and the frontal surface density to derive a geometrical surface roughness; (ii) a more aerodynamic approach where both the DEM and DSM are introduced in a Computational Fluid Dynamics model (CFD). The inversion of the resulting 3-D wind field leads to a fine representation of the aerodynamic surface roughness. Examples of the use of these three approaches are presented for various wind directions together with a cross-comparison of results on heterogeneous land cover and complex roughness element structures.

Colin, J.; Faivre, R.

2010-12-01

470

A Bayesian Approach to Comparing Cosmic Ray Energy Spectra  

NASA Astrophysics Data System (ADS)

A common problem in ultra-high energy cosmic ray physics is the comparison of energy spectra. The question is whether the spectra from two experiments or two regions of the sky agree within their statistical and systematic uncertainties. We develop a method to directly compare energy spectra for ultra-high energy cosmic rays from two different regions of the sky in the same experiment without reliance on agreement with a theoretical model of the energy spectra. The consistency between the two spectra is expressed in terms of a Bayes factor, defined here as the ratio of the likelihood of the two-parent source hypothesis to the likelihood of the one-parent source hypothesis. Unlike other methods, for example ?2 tests, the Bayes factor allows for the calculation of the posterior odds ratio and correctly accounts for non-Gaussian uncertainties. The latter is particularly important at the highest energies, where the number of events is very small.

BenZvi, S. Y.; Connolly, B. M.; Pfendner, C. G.; Westerhoff, S.

2011-09-01

471

Maximum energy yield approach for CPV tracker design  

NASA Astrophysics Data System (ADS)

Foton HC Systems has developed a new CPV tracker model, specially focused on its tracking efficiency and the effect of the tracker control techniques on the final energy yield of the system. This paper presents the theoretical work carried out into determining the energy yield for a CPV system, and illustrates the steps involved in calculating and understanding how energy consumption for tracking is opposed to tracker pointing errors. Additionally, the expressions to compute the optimum parameters are presented and discussed.

Aldaiturriaga, E.; González, O.; Castro, M.

2012-10-01

472

Advancements in adaptive aerodynamic technologies for airfoils and wings  

NASA Astrophysics Data System (ADS)

Although aircraft operate over a wide range of flight conditions, current fixed-geometry aircraft are optimized for only a few of these conditions. By altering the shape of the aircraft, adaptive aerodynamics can be used to increase the safety and performance of an aircraft by tailoring the aircraft for multiple flight conditions. Of the various shape adaptation concepts currently being studied, the use of multiple trailing-edge flaps along the span of a wing offers a relatively high possibility of being incorporated on aircraft in the near future. Multiple trailing-edge flaps allow for effective spanwise camber adaptation with resulting drag benefits over a large speed range and load alleviation at high-g conditions. The research presented in this dissertation focuses on the development of this concept of using trailing-edge flaps to tailor an aircraft for multiple flight conditions. One of the major tasks involved in implementing trailing-edge flaps is in designing the airfoil to incorporate the flap. The first part of this dissertation presents a design formulation that incorporates aircraft performance considerations in the inverse design of low-speed laminar-flow adaptive airfoils with trailing-edge cruise flaps. The benefit of using adaptive airfoils is that the size of the low-drag region of the drag polar can be effectively increased without increasing the maximum thickness of the airfoil. Two aircraft performance parameters are considered: level-flight maximum speed and maximum range. It is shown that the lift coefficients for the lower and upper corners of the airfoil low-drag range can be appropriately adjusted to tailor the airfoil for these two aircraft performance parameters. The design problem is posed as a part of a multidimensional Newton iteration in an existing conformal-mapping based inverse design code, PROFOIL. This formulation automatically adjusts the lift coefficients for the corners of the low-drag range for a given flap deflection as required for the airfoil-aircraft matching. Examples are presented to illustrate the flapped-airfoil design approach for a general aviation aircraft and the results are validated by comparison with results from post-design aircraft performance computations. Once the airfoil is designed to incorporate a TE flap, it is important to determine the most suitable flap angles along the wing for different flight conditions. The second part of this dissertation presents a method for determining the optimum flap angles to minimize drag based on pressures measured at select locations on the wing. Computational flow simulations using a panel method are used "in the loop" for demonstrating closed-loop control of the flaps. Examples in the paper show that the control algorithm is successful in correctly adapting the wing to achieve the target lift distributions for minimizing induced drag while adjusting the wing angle of attack for operation of the wing in the drag bucket. It is shown that the "sense-and-adapt" approach developed is capable of handling varying and unpredictable inflow conditions. Such a capability could be useful in adapting long-span flexible wings that may experience significant and unknown atmospheric inflow variations along the span. To further develop the "sense-and-adapt" approach, the method was tested experimentally in the third part of the research. The goal of the testing was to see if the same results found computationally can be obtained experimentally. The North Carolina State University subsonic wind tunnel was used for the wind tunnel tests. Results from the testing showed that the "sense-and-adapt" approach has the same performance experimentally as it did computationally. The research presented in this dissertation is a stepping stone towards further development of the concept, which includes modeling the system in the Simulink environment and flight experiments using uninhabited aerial vehicles.

Jepson, Jeffrey Keith

473

Running hot water: A systems approach to energy conservation  

NASA Astrophysics Data System (ADS)

Ways to conserve energy in domestic hot water systems are discussed. Examination of the Swedish situation shows that centralized systems, where water heating is a subsidiary of space heating, waste energy because water cools in the pipes after use, and the entire system must operate in summer. Also, water temperature is often much higher than required. Solar panels, individual water heaters, heat pumps, and heat exchangers could contribute to energy conservation, but changes in consumer behavior can also be extremely effective. For example, dish washing energy requirements were reduced by 80% in one neighborhood by giving each apartment a plastic bowl for washing up.

Wulff, P.

1982-03-01

474

Scaling trends in energy recovery logic: an analytical approach  

NASA Astrophysics Data System (ADS)

This paper presents an analytical model to study the scaling trends in energy recovery logic. The energy performance of conventional CMOS and energy recovery logic are compared with scaling the design and technology parameters such as supply voltage, device threshold voltage and gate oxide thickness. The proposed analytical model is validated with simulation results at 90 nm and 65 nm CMOS technology nodes and predicts the scaling behavior accurately that help us to design an energy-efficient CMOS digital circuit design at the nanoscale. This research work shows the adiabatic switching as an ultra-low-power circuit technique for sub-100 nm digital CMOS circuit applications.

Kanungo, Jitendra; Dasgupta, S.

2013-08-01

475

Practical Diagnostic Approach of Energy Consumption and Systematic Fault of AC System  

Microsoft Academic Search

Due to the vast amount of energy consumption of AC (Air Conditioning) systems, the reasonable design, optimal operation and efficient management of AC systems are inevitable and necessary to the whole city energy management (CEM). To achieve these objectives, the verification of systematic characteristics, practical approaches of energy consumption and systematic fault diagnosis of AC systems should be taken as

Weijie Zhang; Jieqing Jia; Xiaokang Sheng

2010-01-01

476

Computational Approach in Determination of {sup 233}U and {sup 233}Th Fermi Energy  

SciTech Connect

There are several methods to get Fermi energy such as hermit polynomial expansion and Wigner-Kirkwood expansion, these are analytical method. In this paper will be discussed numerical approach of calculating Fermi energy of {sup 233}Th and {sup 233}U nuclei. Our work demonstrates the simple technique of determining Fermi energy.

Kurniadi, R.; Perkasa, Y. S.; Waris, A. [Nuclear Physics Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung (Indonesia)

2010-12-23

477

An investigation on the main influencing dynamics in renewable energy development: A systems approach  

Microsoft Academic Search

Renewable energies will have a significant share in the future world's energy portfolio. Hence, optimum policy making to develop renewable energies' market is of high importance. To do so, obtaining comprehensive, integrated, and appropriate understanding of dynamics of the development is necessary for decision makers. This paper is to make that understanding through a systems approach. Using causal loop diagram,

Seyed Hossein Hosseini; Seyed Farid Ghaderi; G. Hamed Shakouri