THE INFLUENCE OF SEPARATION ON THE COLLECTION EFFICIENCIES OF OBSTACLES

A mathematical investigation of the mechanism of collection of aerosol particles based on the principle of wide-stream impaction on various collection surfaces has been considered. The systems analysed were infinitely long cylinders of circular, concave or flat shapes placed in aerosol streams and are based on the assumption of potential flow both with and without separation. The results presented in terms of collection efficiency as a function of the generalized Stokes number enable the basic features of the variation of the collection efficiency with particle size, freestream velocity and width of the collection surface to be identified. Comparisons with the experimental results show that the inclusion of separation into the model for the fluid flow past an obstacle placed in a stream of aerosols offers, in general, a better approximation for the collection efficiency of a sampler based on the principle of wide-stream impaction than does the classical potential flow theory without separation.