CHARACTERIZATIONS OF THE CRITICAL STOKES NUMBER FOR POTENTIAL AND VISCOUS FLOWS

The impaction on symmetrical obstacles placed in uniform streams of ae rosols is investigated. The governing equations of motion are nonlinea r differential equations involving a parameter called the Stokes numbe r. The study differentiates between the critical value of the Stokes n umber on the centre-line, k(cr), below which no particles reach the st agnation point in finite time, and the critical value of the Stokes nu mber on the obstacle, K-cr, below which no particles may be deposited on the obstacle in finite time. Based on the properties of the centre- line fluid velocity of the potential and viscous flows past a variety of symmetrically shaped obstacles, upper and lower bounds of k(cr) and K-cr are established. Furthermore, using a numerical procedure for so lving nonlinear differential equations with unknown parameters the cri tical values of k(cr) and K-cr are obtained.