Accession Number : ADA292650

Title :   Research on Bluff-Body Vortex Wakes.

Descriptive Note : Final technical rept. 1 Jan 90-30 Jun 94,

Corporate Author : CALIFORNIA INST OF TECH PASADENA GRADUATE AERONAUTICAL LABS

Personal Author(s) : Roshko, Anatol

PDF Url : ADA292650

Report Date : 22 FEB 1995

Pagination or Media Count : 8

Abstract : Comparison of laboratory experiments and computational results for two dimensional flows showed that, in impulsively started flows, laboratory flows are two dimensional in the early stages and that three dimensional effects develop after acceleration is complete. In fully developed flow the mean and fluctuating forces are considerably lower (up to 50%) in the laboratory flows (ie with three dimensionality) than in the two dimensional numerical simulations. The experiments in tow tank and water tunnel also revealed the existence of long-time modulations of vortex shedding forces. These have the form of bursts with duration of order 10 vortex shedding periods. A novel method of introducing controlled spanwise components of velocity into otherwise two dimensional flow, at low Reynolds number was to give the cylinder an axial (spanwise) motion, either a steady translation or a periodic oscillation. For unsteady, periodic axial oscillation of the cylinder, the experiments showed how the ratio of the spanwise period to the vortex shedding period determines the patterns of vortex dislocation in the wake, how regimes of chaos are formed and how shedding frequency and wake spectra are affected. (AN)

Descriptors :   *VORTEX SHEDDING, *WAKE, *TWO DIMENSIONAL FLOW, VELOCITY, MATHEMATICAL MODELS, ALGORITHMS, COMPUTERIZED SIMULATION, EXPERIMENTAL DATA, ACCELERATION, COMPARISON, NUMERICAL ANALYSIS, COMPUTATIONAL FLUID DYNAMICS, THREE DIMENSIONAL, DISLOCATIONS, DRAG, MODULATION, NAVIER STOKES EQUATIONS, INVISCID FLOW, REYNOLDS NUMBER, OSCILLATION, WATER TUNNELS, AXIAL FLOW.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE