Channel flow of smectic films

The hydrodynamics of smectic films at an air-water interface is discussed, with particular focus on the viscous response of the film under flow normal to the layers. The corrections to the response functions of the smectic ph ase, arising from the coupling between the flow and the smectic order param eter, are calculated. The results for the effective viscosity are illustrat ed by analyzing smectic film flow in a channel geometry. Two Limiting cases of the how, namely, motion dominated by dislocation-induced shear-softenin g and dislocation-free motion dominated by the permeation mode of mass tran sfer, are studied. The effect of drag from a finite depth liquid subphase i s considered. The results rue compared to those for hexatic and liquid film s.