Plane Couette flow of viscoplastic materials along a slippery vibrating wall

Hence vibrations of moderate or high-velocity amplitude applied to adherent or slippery walls enhance plane Couette flow rates for viscoplastic materials. With moderate values of this amplitude, longitudinal vibrations may be 1.5-2 times more efficient than transverse vibrations with an equivalent cost. However, if for technological reasons transverse vibrations have to be preferred, they can also produce significant results. In any case, coating flows should benefit from an adequate application of ultrasound at the wall.