Temporal evolution of the density distribution of a straight incoming wave that interacts with CHs of different shapes. (a) Interaction of a wave that consists of a purely enhanced pulse with a circular CH. (b) Circular CH and a CW that includes a density enhancement at the wave front and a depletion region in the rear part of the incoming wave. (c) Elliptical CH. (d) Symmetric convex CH. (e) Symmetric concave CH. (f) Asymmetric concave CH. (f) Purely enhanced pulse with an asymmetric concave CH.