Spherical Particles and Drops at High Peclet Numbers

Spherical Particles and Drops at High Peclet Numbers 

In what follows we restrict ourselves to the case of high Peclet numbers, in which there are no closed streamlines in the flow. 

The diffusion boundary layer in problem (4.12.1), (4.12.2) is first adjacent to the particle surface and then rapidly spreads over the flow region with the subsequent exponential relaxation to a steady state. The characteristic relaxation time rr is of the order of Pe-2 3 for a solid particle and of the order of Pe-1 for bubbles and drops of moderate viscosity. 

The following approximate formula for the time dependence of the mean Sherwood number for an arbitrary steady-state flow past spherical particles, drops, and bubbles was obtained by the method of asymptotic analogies in [357]  

Equation (4.12.3) gives a valid asymptotic result for any flow field in both limit cases r - 0 and r — oo. 

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