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 mea n turbulent flow is calculated using the standard kappa-epsilon turbul ence closure model. The trajectories of particles in the flow field ar e simulated by solving the corresponding Lagrangian equation of partic le motion which includes such effects as inertia, drag, gravity, Saffm an force, and turbulent diffusion. Three parameters describing the per formance of a sampling probe-aspiration ratio, transmission ratio, and wall loss-are calculated by tracking a large number of particles. Com putations 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 equiv alent diameter. A comparison is made between the numerically calculate d and the experimentally measured values of wall loss and aspiration r atio. The agreement between the numerical prediction and the experimen tal data is good. The maximum difference is 6% for aspiration ratio an d 11% for the wall losses.