Accession Number : ADA189607

Title :   Control of Structure in Turbulent Flows: Bifurcating and Blooming Jets.

Descriptive Note : Final rept. 1 Feb 84-31 May 87,

Corporate Author : STANFORD UNIV CA DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Reynolds, W C ; Parekh, D E

PDF Url : ADA189607

Report Date : 10 Oct 1987

Pagination or Media Count : 49

Abstract : The general objective of this work is to control jet flows by properly organizing the dominant large-scale vortex structures. The work has focused on understanding the influence of excitation frequency and amplitude on the large-scale structures of these flows at various Reynolds numbers. Specifically, the effects of dual-mode forcing on the structure, momentum, and mixing characteristics of turbulent jets have been investigated using a combination of laboratory experiments and numerical simulations. The combination of properly-selected axial and orbital excitation has been shown to have dramatic effect on the structure and mixing of round jets. Experiments and numerical simulations show that these phenomena are due to interaction between the large-scale vortices in the jet near field. The position and phasing of these vortices can be altered by relatively weak excitation, causing the jet to divide into two separate jets (bifurcation) or to explode (bloom) in a shower of vortex rings. This report summarizes the key results of studies in water and low-speed air flows.

Descriptors :   *TURBULENT FLOW, *VORTICES, *JET FLOW, AIR FLOW, CONTROL SYSTEMS, EXCITATION, FREQUENCY, LABORATORY TESTS, LOW STRENGTH, LOW VELOCITY, MIXING, MOMENTUM, NUMERICAL ANALYSIS, REYNOLDS NUMBER, RINGS, STRUCTURAL PROPERTIES, STRUCTURES, WATER, JET MIXING FLOW, NEAR FIELD

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE