Simultaneous Measurement of the Velocity and Pressure in a Plane Jet (Estimation of Conditional Averaged Value and Diffusion Term in the Intermittent Region)

Abstract

The simultaneous measurement of the velocity and pressure in a plane jet has been performed by using a combined probe that consists of an X-type hot-wire probe and a static pressure probe. Firstly, the conditional ensemble averaged statics are investigated on the basis of the intermittency function obtained from the velocity signal by the hot-wire sensor set in the intermittent region of a plane jet. Secondly, the validity of the models for a turbulent and pressure diffusion term is investigated. The measurement results show that the cross-streamwise profile of the diffusion term in the turbulent energy transport equation differs significantly, according to the state of the flow (turbulent or non-turbulent flow) in the intermittent region. By decomposing the diffusion term into two terms, i.e., the turbulent diffusion term and the pressure diffusion term and estimating each term separately, it is found that the cross-streamwise profile of the pressure diffusion term is virtually the same, irrespective of the state of the flow in the intermittent region. This indicates that the difference in the cross-steramwise profile of the diffusion term is cause by the difference in the turbulent diffusion term. In addition, the evaluation of the two kinds of gradient diffusion models of the Reynolds stress transport equation shows that the model constants become constant and the validity of these models can be confirmed except for the region near the jet centerline and intermittent region. Finally, it is shown that both slow-part and rapid-part of the velocity-pressure correlation term must be modeled appropriately to predict the velocity-pressure correlation correctly.