The Development of a Laser Doppler Velocimetry System for Unsteady Separated Flow Research PDF Download
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Author: R. A. Kadlec
Publisher:
ISBN:
Category : Laser Doppler velocimeter
Languages : en
Pages : 28
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Book Description
The Frank J. Seiler Research Laboratory (FJSRL) at the U.S. Air Force Academy is conducting a comprehensive experimental research program to study unsteady, separated flows and, in particular, the dynamic stall of oscillating airfoils. The aim of this study is to achieve a clearer understanding into the physical mechanisms responsible for dynamic stall and to capitalize on these unique stall features by using them to improve the turn performance and maneuverability of flight vehicles. The objective of one phase of this experimental research program has been to adapt a general purpose Laser Doppler VElocimetry (LDV) two velocity component system to dynamic stall experiments in the Subsonic Wind Tunnel at the USAFA. The preliminary design of the LDV system, its special constraints and the characterization of system signal and noise parameters are described. Results presented for the initial operation of the LDV system demonstrate its performance capabilities. It has been observed that accurate measurements in the wind tunnel environment can be achieved only when optical noise produced by scattered laser light from wind tunnel surfaces is minimized. While the LDV system configuration satisfies all constraints related to the USAFA Subsonic Wind Tunnel geometry and is capable of accurate velocity measurements in the two-dimensional flow field surrounding an airfoil, a reconfiguration of the system is suggested to improve optical alignment procedures and overall system signal-to-noise ratio. (Author).
Author: R. A. Kadlec
Publisher:
ISBN:
Category : Laser Doppler velocimeter
Languages : en
Pages : 28
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Book Description
The Frank J. Seiler Research Laboratory (FJSRL) at the U.S. Air Force Academy is conducting a comprehensive experimental research program to study unsteady, separated flows and, in particular, the dynamic stall of oscillating airfoils. The aim of this study is to achieve a clearer understanding into the physical mechanisms responsible for dynamic stall and to capitalize on these unique stall features by using them to improve the turn performance and maneuverability of flight vehicles. The objective of one phase of this experimental research program has been to adapt a general purpose Laser Doppler VElocimetry (LDV) two velocity component system to dynamic stall experiments in the Subsonic Wind Tunnel at the USAFA. The preliminary design of the LDV system, its special constraints and the characterization of system signal and noise parameters are described. Results presented for the initial operation of the LDV system demonstrate its performance capabilities. It has been observed that accurate measurements in the wind tunnel environment can be achieved only when optical noise produced by scattered laser light from wind tunnel surfaces is minimized. While the LDV system configuration satisfies all constraints related to the USAFA Subsonic Wind Tunnel geometry and is capable of accurate velocity measurements in the two-dimensional flow field surrounding an airfoil, a reconfiguration of the system is suggested to improve optical alignment procedures and overall system signal-to-noise ratio. (Author).
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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Book Description
Author: William Joseph Yanta
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 64
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Book Description
Results are presented for an experimental program which investigated the application of an LDV technique in supersonic flows. This paper presents an analysis of the behavior of light-scattering particles in rapidly accelerating or shock decelerated flows, an evaluation of particle production techniques and the results of several velocity measurements. Measurements included the velocity distribution along the nozzle centerline and flow over a diamond airfoil in a Mach 3 tunnel and velocity profiles for a turbulent boundary layer in a Mach 4.8 facility. It is demonstrated that LDV measurements can be made consistently with errors of less than five percent if the particle lag is considered. (Author).
Author:
Publisher:
ISBN:
Category : Fuel
Languages : en
Pages : 1092
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Book Description
Author: Steven Dale Hedrick
Publisher:
ISBN:
Category :
Languages : en
Pages : 73
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Book Description
The primary goal of this thesis was the development of an experimental technique, and supporting software, for the acquisition and analysis of unsteady velocity data generated by an oscillating airfoil. This research was in support of a major investigation of the compressibility effects on dynamic stall. The experimental procedure involved schlieren flow visualization for comparison of steady and unsteady flow fields, and for determination of parameters for further study. Laser Doppler velocimetry was employed for obtaining velocity data in the airfoil wake. For unsteady data, the airfoil was oscillated in pitch about its quarter chord. The data analysis produced wake profile plots representing the flow field distributed by the airfoil. Results were obtained for steady and unsteady conditions. Keywords: Laser doppler velocimetry, Schlieren flow visualization, Dynamic stall.
Author:
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ISBN:
Category :
Languages : en
Pages : 906
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A new laser based flow interrogation system, capable of simultaneous measurement of planar three-component velocity data, was constructed and tested. The Virginia Tech Doppler Global Velocimeter (DGV) system was designed for use in the Virginia Tech Stability Wind Tunnel as a tool for investigating complex three-dimensional separated flow regions. The systems was designed for robustness, ease of use, and for acquisition of low uncertainty velocity data. A series of tests in the Stability Tunnel were conducted to determine the how well the new DGV system met these goals. Extensive calibration tests proved the system is capable of measuring the frequency shifts of scattered laser light, and therefore velocity. However, equipment failures and inadequate flow seed density prevented accurate velocity measurements in the separated wake region behind a 6:1 prolate spheroid. Detailed uncertainty analysis techniques demonstrated that, under the proper conditions, the system is capable of making velocity measurements with approximately +/- 2m/s uncertainty.
Author:
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 302
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Book Description
Author:
Publisher:
ISBN:
Category : Fuel
Languages : en
Pages : 666
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Book Description
Author: Alain Boutier
Publisher: John Wiley & Sons
ISBN: 1118569334
Category : Science
Languages : en
Pages : 436
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Book Description
In fluid mechanics, velocity measurement is fundamental in order to improve the behavior knowledge of the flow. Velocity maps help us to understand the mean flow structure and its fluctuations, in order to further validate codes. Laser velocimetry is an optical technique for velocity measurements; it is based on light scattering by tiny particles assumed to follow the flow, which allows the local fluid flow velocity and its fluctuations to be determined. It is a widely used non-intrusive technique to measure velocities in fluid flows, either locally or in a map. This book presents the various techniques of laser velocimetry, as well as their specific qualities: local measurements or in plane maps, mean or instantaneous values, 3D measurements. Flow seeding with particles is described with currently used products, as well as the appropriate aerosol generators. Post-processing of data allows us to extract synthetic information from measurements and to perform comparisons with results issued from CFD codes. The principles and characteristics of the different available techniques, all based on the scattering of light by tiny particles embedded in the flow, are described in detail; showing how they deliver different information, either locally or in a map, mean values and turbulence characteristics.
