The interface between two simple fluids between two oscillating vertical planes

The shape of the interface between two simple fluids having nearly the same densities which are contained between two oscillating vertical planes has been calculated by the method of domain perturbation pivoted about the rest state. The analysis has been carried out through second order in the amplitude of the oscillation velocity. The existence of the shearing motion on the interface has been considered by incorporating the spatial dependence of the primary motion on the vertical coordinate as well as on the transverse coordinate. This has led to an enhancement of the normal stress effect and thus results in predicting a higher rise in the interface than that in the case when no shearing motion is assumed to exist on the interface.