Spreading of a non-Newtonian liquid drop over a homogeneous rough surface

The spreading of a non-Newtonian liquid drop over a homogeneous rough surface is theoretically analyzed in the case of complete wetting. Using the energy approach, a relation is derived among the surface roughness, spreading rate of the drop and the contact angle. It is shown that non-Newtonian liquid drop spreads faster over rough surface than smooth surface. Further, it is observed that a shear thickening liquid (n > 1) spreads with faster speed than a shear thinning liquid (n < 1) over a rough surface.