Hostname: page-component-848d4c4894-wzw2p Total loading time: 0 Render date: 2024-04-30T21:43:20.540Z Has data issue: false hasContentIssue false
  • English
  • Français

The diode-array velocimeter

Published online by Cambridge University Press:  26 April 2006

William J. Devenport  and
Edward J. Smith
William J. Devenport
Affiliation:
Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
Edward J. Smith
Affiliation:
Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
Get access Rights & Permissions [Opens in a new window]

Abstract

Diode-array velocimetry is an optical technique for measuring turbulent flows. It involves timing the passage of seed particles through a small section of a light beam by imaging the light they scatter onto one or more photodiode arrays. The arrays have a few carefully shaped elements, the shapes and positions of which are used to control the measurement-volume geometry and thus select the measurement made. Measurement volumes sensitive to velocity, position and acceleration may be designed. Measurements in highly turbulent and reversing flows are possible.

A diode-array velocimeter (DAV) for one-component velocity measurements has been developed to demonstrate this concept. This uses a single laser beam to illuminate particles and a photodiode array with two rectangular elements to sense their motion. The sensitivity of this DAV to electrical noise in the photodiode circuitry decreases with reduction in measurement-volume size. The angle response is closely cosinusoidal to about 60°. Changes to the photodiode-array design could substantially increase this limit.

Measurements of mean velocity, normal turbulence stress and velocity skewness made with this DAV in two attached boundary-layer flows compare well with hot-wire measurements. Useful DAV measurements were made as close as 0.2 mm from the wall. DAV measurements made in a separated flow formed downstream of a fence are also presented. These show all the expected features of the separated shear layer and recirculation including the sub-boundary layer formed beneath the backflow. Histograms measured in the reversing part of this flow show a hole near zero velocity that is a consequence of the imperfections in the DAV angle response and limitations on the maximum transit time. These are not fundamental problems, however, and the hole could be minimized or eliminated by using a different photodiode array design and/or measurement strategy.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 259 , 25 January 1994 , pp. 167 - 189
Copyright
© 1994 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Adams, E. W., Johnston, J. P. & Eaton, J. K. 1984 Experiments on the structure of a turbulent reattaching flow. Rep. MD-43. Dept. of Mech. Engng, Stanford University.
Bearman, P. W. 1971 Corrections for the effect of ambient temperature drift on hot-wire measurements in incompressible flow. DISA Information, vol. 11, pp. 25–30.
Bradbury, L. J. S. & Castro, I. P. 1971 A pulsed-wire technique for velocity measurements in highly turbulent flows. J. Fluid Mech. 49, 657–691.Google Scholar
Boutier, A. & Lefevre, J. 1988 Mosaic laser velocimeter. In 4th Symp. on Applications of Laser Anemometry to Fluid Mechanics, Lisbon, Portugal.
Devenport, W. J. & Smith, E. J. 1993 Development of the one component diode array velocimeter. Rep. VPI-AOE-201. AOE Dept., VPI & SU.
Devenport, W. J. & Sutton, E. P. 1993 An experimental study of two flows through an axisymmetric sudden expansion. Exp Fluids 14, 423–432.Google Scholar
Durst, F., Melling, A. & Whitelaw, J. H. 1981 Principles and Practice of Laser Doppler Anemometry. Academic.
Eaton, J. K. & Johnston, J. P. 1980 Turbulent flow reattachment: an experimental study of the flow and structure behind a backward-facing step. Rep. MD-39. Dept. of Mech. Engng, Stanford University.
Fuchs, W., Albrecht, H., Nobach, H., Tropea, C. & Graham, L. J. W. 1992 Simulation and experimental verification of statistical bias in laser Doppler anemometry including non-homogeneous particle density. In 6th Symp. on Applications of Laser Anemometry to Fluid Mechanics, Lisbon, Portugal.
Hirleman, E. D., Yue, Y., Berman, N. S. & Guan, D. X. 1984 Single laser beam velocimetry (L1V) in turbulent flows. In 2nd Symp. on Applications of Laser Anemometry to Fluid Mechanics, Lisbon, Portugal.
Ohmura, K., Hishada, K. & Maeda, M. 1992 A multi-angle laser-two-focus velocimeter using photodiode arrays. In 6th Symp. on Applications of Laser Anemometry to Fluid Mechanics, Lisbon, Portugal.
Seegmiller, H. L. 1985 Seeding subsonic, transonic and supersonic flows with 0.5 μ polystyrene latex spheres. In Wind Tunnel Seeding Systems of Laser Velocimeters, NASA CP-2393.
Smith, E. J., Rife, M. C. & Devenport, W. J. 1990 Investigations of the small boundary-layer tunnel. Rep. VPI-AOE-177. AOE Dept., VPI & SU.