ARTICLE:

• JET DIFFUSION CONTROL BY ACOUSTICALLY DRIVEN SECONDARY FILM FLOW VISUALIZATION OF CONTROLLED JET STRUCTURE  download article

N. Miyagi
Nihon University, Tokyo, Japan

H. Fujita
Nihon University, Tokyo, Japan

Motoaki Kimura
Department of Mechanical Engineering, College of Science and Technology, Nihon University, 1-8, Kanda Surugadai, Chiyodaku, Tokyo 101-8308, Japan

H. Shoji
Nihon University, Tokyo, Japan

ABSTRACT

The diffusion characteristics of a jet with outside film flow, with and without acoustic excitation on the film flow are studied experimentally. The flow visualization of the jet structure in streamwise and crosswise sections is performed in order to understand the mechanism of diffusion restraint and promotion. As a result, it is confirmed that the diffusion of the jet can be controlled by giving the velocity difference between the main stream and the film flow, and by giving acoustic excitation on the film flow. When the film flow velocity is half of the mainstream velocity, the diffusion is restrained regardless of the acoustic excitation. When the film flow velocity is the same as the mainstream velocity, proper acoustic excitation can promote the jet diffusion. The difference between the restraint and promotion of the jet diffusion depends on the development of vortex rings and longitudinal vortices in the jet.

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