Spatial Simple Waves on a Shear Flow

The paper studies simple waves of the shallow‐water equations describing three‐dimensional wave motions of a rotational liquid in a free‐boundary layer. Simple wave equations are derived for the general case. The existence of unsteady or steady simple waves adjacent continuously to a given steady shear flow along a characteristic surface is proved. Exact solutions of the equations describing steady simple waves were found. These solutions can be treated as extension of Prandtl–Mayer waves for sheared flows. For shearless flows, a general solution of the system of equations describing unsteady spatial simple waves was found.