Control of Round Impinging Jet by Coaxial Annular Sub Jet. Effects of Velocity Ratio on Flow Characteristics.

Abstract

This paper presents experimental and numerical analyses for the flow characteristics of double coaxial pipe jets, which consist of a central round main air jet and a coaxial annular sub air jet, impinging normally onto a flat plate. As the results, it was found that the mean flow characteristics, namely each velocity profile, decay of maximum velocity, spread of jet, and pressure distribution, and the turbulence characteristics, namely each turbulence component and Reynolds shear stress, of a round impinging jet can be controlled by an annular coaxial sub jet. In paticular, turbulent kinetic energy near the flat plate is augmented considerably by the existence of a turbulent shear layer between main and sub jets. The increase in a forced convective heat transfer on the plate is also expected. Numerical analysis was carried out using the k-ε turbulent model.