NUMERICAL-SIMULATION OF 2-DIMENSIONAL BLUNT BODY SAMPLING IN VISCOUS-FLOW

This paper presents a numerical investigation of the aspiration efficiency of a cylindrical blunt body sampler with a forward facing suction opening. The paper (1) describes and validates the numerical procedure for calculating laminar viscous flow around a two-dimensional blunt cylindrical sampler; (2) combines the flow field calculations with particle dynamics to determine the aerosol aspiration efficiency of the sampler as a function of the particle Stokes number, with a physical explanation for the shape of the aspiration efficiency curve; and (3) examines the effects of the suction to freestream velocity ratio, Reynolds number, and suction opening size on the viscous flow field and aspiration efficiency. The results of the study indicate the particle size ranges and flow conditions where the viscous boundary layer affects the aerosol sampling process. Comparing the results from the viscous calculations with results from inviscid calculations shows qualitative agreement but quantitative differences. In particular, the viscous calculation produces generally lower aspiration efficiencies, indicating that the viscous boundary layer can play an important role in particle inhalability.