Near-wall and Turbulence Behavior of Swirl Flows through an Aerodynamic Nozzle

Abstract

It is often a challenge to achieve uniform flow in turbulent swirl flow and to predict the flow within the nozzle as measurement diagnostics face difficulty to capture both mean flow and turbulence. The purpose of this study is to numerically investigate the near wall flow characteristics and turbulent behavior for the effect of different tangential inlet numbers of an incompressible turbulent swirl air jet. In this regard, axial-plus-tangential flow based swirling nozzle is considered for the simulation using finite volume method, where turbulence is approximated by the Shear Stress Transport (SST) k-ω model. The results show that axial and tangential velocity at the wall vicinity response the most. Moreover, the turbulent flow characteristic for no swirl flow is nearly uniform, but for swirl flow it fluctuates abruptly near the inlet section where the swirl has introduced. The skin friction coefficient for 2TP is the maximum for swirl flow and for no swirl condition the skin friction coefficient is nearly uniform. Due to the swirl introduction the pressure drop characteristics near the nozzle center response quickly and near the wall vicinity this property changes slowly. The magnitude of swirl decay fluctuates before the nozzle converging section however after the nozzle converging section the swirl decay is nearly constant. The local swirl near the inlet is highly unpredictable although after the nozzle converging section the local swirl profile is nearly similar for 2TP, 3TP and 4TP.