Numerical study of turbulent round free jet

Abstract

In the present study, flow characteristics of turbulent round free jet has been studied numerically. Simulation has been done for a 29 mm diameter jet for four different jet exit velocities ranging from 19.9 m/s to 90 m/s that covers a wide range of Reynolds No. (3.94×104∼1.79×105) based on jet diameter. The main objective of this study is to evaluate the effect of jet exit velocity on mean flow properties of jet flow field (such as centerline velocity profile, jet half-width, mean velocity decay rate, jet spreading rate and self-preservation for velocity) along with turbulence kinetic energy profile and mean turbulent dissipation rate profile in the incompressible speed range (M < 0.3). Finally a two-point similarity analysis has been done to examine the well-known power-law variation and mean turbulent energy dissipation (ε¯) along the axis of turbulent round jet in the context of scale-by-scale energy budget. Turbulent flow field within the computational domain has been obtained by solving Reynolds Averaged Navier-Stokes (RANS) equation with standard κ-ε model using finite volume method. In case of self-preservation (SP) it has been found that SP for velocity attained in the near field (∼3d) that does not depend on jet exit velocity while for turbulence, SP attained in the far field region (x/d ≥ 30) and depends less on the jet exit velocity.