GAS-PARTICLE FLOWS ABOUT A COBRA PROBE WITH PURGING

The detailed flow behaviour around a special purpose four-hole Cobra P itot pressure probe with purging is investigated computationally in ga s and gas-particle flows. The incompressible steady state Navier-Stoke s equations for the gas phase are solved numerically using a general p urpose computational fluid dynamics code. Computational results are pr esented at a typical Reynolds number of 2 x 10(3). The use of purging gas blown out of the pressure ports to prevent particle blockage is mo delled, providing design and operational data: (1) on the effects of p urging gas on the calibration characteristics of the probe, and (2) th e effectiveness of purging on particle blockage prevention. A Lagrangi an procedure is used to calculate the particle trajectories via a one way coupling formulation. A continuous purging velocity of 30% of the freestream velocity prevents blockage by solid particles and allows a monotonic calibration to be maintained.