Internal resistance to transfer

The relative importance of the rear part of the drops compared with solid spheres was noted by Garner and also by Terjesen (T3). Garner (G4, Gil) and others (Al) showed that at moderate Reynolds numbers, up to 2500, most of the transfer takes place in the front part of the solid spheres ahead of the separation point. However, no frontal diffusion into liquid drops could be detected at high rates of fall (G2), whereas it was readily noticeable behind the drop. Thorsen and Terjesen (T3) concluded that the relative importance of the front and rear for drops and solid spheres is reversed, beginning with Reynolds numbers above 20. This hypothesis does not account for the extreme case where internal circulation is reversed (LI7), probably due to higher transfer rates at the front and to the nonnegligible internal resistance to transfer. 

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