Research on Bluff-Body Vortex Wakes.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 22, 1995
- Accession Number
- ADA292650
Entities
People
- Anatol Roshko
Organizations
- California Institute of Technology