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RESEARCH PAPERS: Additional Technical Papers

Influence of the Axisymmetric Contraction Ratio on Free-Stream Turbulence

[+] Author and Article Information
V. Ramjee, A. K. M. F. Hussain

Mechanical Engineering Department, University of Houston, Houston, Tex.

J. Fluids Eng 98(3), 506-515 (Sep 01, 1976) (10 pages) doi:10.1115/1.3448386 History: Received June 16, 1976; Online October 12, 2010

Abstract

The effect of axisymmetric contractions of a given shape and of contraction ratios c = 11, 22, 44.5, 64, and 100 on the free-stream turbulence of an incompressible flow has been studied experimentally with hot-wires. It is found that the longitudinal and lateral kinetic energies of turbulence increase along the contraction. The monotonic increase of the longitudinal turbulent kinetic energy with increasing c is in contrast with the linear (Batchelor-Proudman-Ribner-Tucker) theory. The variation of the lateral turbulent kinetic energy with c is in qualitative agreement with the theory; however, the increase is much lower than that predicted by the theory. The linear theory overpredicts the decrease in the longitudinal turbulence intensity with increasing c and under-predicts the decrease in the lateral turbulence intensity with increasing c. For the given flow tunnel, it is found that a contraction ratio c greater than about 45 is not greatly effective in reducing longitudinal turbulence levels further; the lateral turbulent intensity continues to decrease with increasing c. In the design of a low turbulence-level tunnel, the panacea for the reduction of the turbulence level does not lie in an indefinite increase of the contraction ratio alone. Studies with various upstream screens and a given contraction of c = 11 suggest that the exit turbulence intensities are essentially independent of the Reynolds number based on the screen-mesh size or screen-wire diameter of the upstream screen.

Copyright © 1976 by ASME
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