Accession Number : ADP005886

Title :   Oscillating Flow over Bluff Bodies in a U-Shaped Water Tunnel,

Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s) : Sarpakaya, Turgut

Report Date : JUN 1987

Pagination or Media Count : 16

Abstract : The studies deal with sinusoidally oscillating separated and unseparated flows over various types of bluff bodies. First, the characteristics of a large U-shaped vertical water tunnel are described and then the numerical and experimental results obtained with circular cylinders are presented. It is shown that for two-dimensional, attached, and laminar-flow conditions the data are, as expected, in good agreement with the Stokes Wang analysis. The oscillatory viscous flow becomes unstable to axially periodic Taylor-Goertler vortices above a critical Keulegan-Carpenter number K (K = (U sub m)(T)/D) for a given Beta (Beta = D sq/upsilon T). For larger values of K the effects of separation and vortex shedding become increasingly important, eventually leading to a very interesting half Karman vortex street in the transverse direction in the range 8 < K < 13. The discrete vortex model of the separated oscillating flow is shown to provide a reasonably satisfactory explanation of the transverse vortex street. An attempt is also made, through use of an idealized vortex model, to explain the observed flow modes and the cycle-to-cycle variations in forces and pressures in terms of their sensitivity to small stochastic variations in the position of the vortices.

Descriptors :   *UNSTEADY FLOW, *VORTICES, BLUNT BODIES, TWO DIMENSIONAL FLOW, OSCILLATION, FLOW SEPARATION, LAMINAR FLOW, ATTACHMENT, WATER TUNNELS, VISCOUS FLOW, VORTEX SHEDDING, PERIODIC VARIATIONS, CYLINDRICAL BODIES.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE