The propagation of whispering gallery waves near a concave (from the side of the wave field) boundary having a flat point is studied. As in [4], the problem that arises for an equation of Schrodinger type is solved by the method of grids. The results of the computations are presented as shadow figures.In this work we consider the two-dimensional problem of the propagation of whispering gallery waves near a concave (from the side of the wave field) boundary having a flat point,i.e., a point at which the curvature of the boundary has a zero of multiplicity two. If the medium is inhomogeneous the role of the curvature of the boundary is played by the so-called effective curvature of the boundary (see, e.g., [i, 2]). In this case the problem consists in describing the behavior of whispering gallery waves in neighborhood of the zero (of multiplicity two) of the effective curvature of the boundary.In both these cases we obtain the same problem for the leading term of the asymptotics of the wave field at high frequencies.The initial assumptions consist in the following. It is assumed that the wave field satisfies the Helmholtz equation with a variable speed C (MJ and vanishes on the reflecting (smooth) boundary F , i.e., (~+Lo'~C-~U=0 ,UIF =0 We denote by ~ and ~, respectively, the arc length of the curve ~ and the coordinate along the normal to ~ at the point 6 (~>0 on the side of ~ , where the wave process is considered). Suppose that the effective curvature ~(3) of the boundary ~ in a neighborhood of the point ~=0 has the form ~.~)=~6~ + 0(33) with a constant ~>0. It is assumed that for 8~0 there is one whispering gallery wave, and it is required to describe its behavior for 6~0 9Using the boundary-layer method,* we obtain the following problem for the leading term of the wave field U as oO--oo . In the region ~0 ,~6 ~oo,+oo) it is required to find a solution ~(~,~# of the equation
co.1) ~f--~D~ +which vanishes at 3C=0 , foreach te(-oo,+~) is square-integrable on the semiaxis ~=~0 (i.e., W e[~(0,o~) ), and as ~---~o has prescribed asymptotics ~o in the sense of 6~(0,oo) , ao (i.e, Jl~-~ol~d~--0 as ~---oo ). The function ~o in the present case is given by 0 *We shall not consider here the derivation of the corresponding formulas, since it is altogether analogous to the derivation presented in [3] for the case of a simple zero of the effective curvature of the boundary.