Particle Tracking in Turbulent Transonic Flow Field

SREEKESH KOOKKAL, Suresh Dhaniyala, Clarkson University, Potsdam, NY

     Abstract Number: 553
     Working Group: Aerosol Physics

Abstract
Transonic flow fields are commonly encountered in pressure reduction systems such as critical orifices and in sampling systems on high speed aircraft. Under such conditions flow field calculation is made using Reynolds Averaged Navier-Stokes (RANS) technique. Particle trajectory calculations are generally made using Lagrangian Particle Tracking (LPT) coupled with discrete random walk (DRW) model, where instantaneous velocity is calculated as sum of mean velocity and fluctuating velocity. Conventional DRW models in commercial RANS codes such as ANSYS FLUENT tend to overpredict particle loss due to turbulence in channels and under-predict the role of turbulence in high-speed flow. Here, we use a modified DRW approach that accounts for fluctuating velocity calculated from the RMS turbulence velocity fluctuations and a drift velocity correction term. The drift velocity correction term includes the gradient of Lagrangian time scale and velocity, accounting for particle inertial interaction with turbulent eddies. We evaluate the performance of this improved DRW for three flow conditions: turbulent flow in a channel, flow through a critical orifice, and non-critical flow through an aerosol skimmer system. The numerical predictions are compared against experimental measurements for the three cases. The results from our improved DRW compared to that obtained with conventional DRW will be presented.