... = e(?s ? ?) [2] µc is then obtained by experiment or estimated from the Einstein relation using the volumetric solids concentration C, a constant k``(for a given shape of particle, 2.5 for spheres) and the liquid viscosity µ:- µc = µ(1 + k``C) [3] This appears to be OK for C <0.02 above which µc = µ exp(k``C/(1? a`C)) [4] where a` is another constant (0.609 for spheres). 2) As above but, get rid of K`` and introduce a functional dependence on voidage (e) and denote relative motion up:- x2(?s ? ?c)g up = ?????.f(e) [5] 18µc As fractional area for fluid flow is e, fluid velocity is uc(1? e)/e (That is a downward flux of particles uc ? C balanced by an equal upward flux of liquid confined to flow in the voids.) 1? e uc Then up = uc + uc ?? = ? [6] e e Experimental Evidence: (Steinour) f(e) = 10 ?1.82(1? e) [7] As ...

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