NUMERICAL PREDICTION OF THE PERFORMANCE OF A SHROUDED PROBE SAMPLING IN TURBULENT-FLOW

A numerical simulation is presented for the performance of a shrouded probe sampling at a zero yaw angle to a turbulent flow stream. The mean turbulent flow is calculated using the standard kappa-epsilon turbulence closure model. The trajectories of particles in the flow field are simulated by solving the corresponding Lagrangian equation of particle motion which includes such effects as inertia, drag, gravity, Saffman force, and turbulent diffusion. Three parameters describing the performance of a sampling probe-aspiration ratio, transmission ratio, and wall loss-are calculated by tracking a large number of particles. Computations are carried out for free stream velocities of 8.9, 15.6, and 21 m/s, and for particle sizes of 5, 10, and 15 mum aerodynamic equivalent diameter. A comparison is made between the numerically calculated and the experimentally measured values of wall loss and aspiration ratio. The agreement between the numerical prediction and the experimental data is good. The maximum difference is 6% for aspiration ratio and 11% for the wall losses.