COMBINED REFRACTION DIFFRACTION OF SHORT-WAVES IN LARGE COASTAL REGIONS

A method for solving the combined refraction-diffraction equation in large domains is described. This equation is modified to the reduced wave equation, and the elliptic, boundary-value problem is solved by the marching or "Error Vector Propagation" method. The solution method is direct, and eliminates the computer storage problems associated with large matrices obtained in standard methods. This efficiency is obtained at the cost of resolution of the shorter wave components in a direction normal to the incident wave direction. As such, the method is limited by the paraxial approximation encountered in the parabolic equation method of solving the oceanwave refraction-diffraction problem. But it overcomes the other limitation of the parabolic approximation, in that it allows backscattering and propagation in the - x direction. Therefore it is possible to accommodate reflecting structures such as seawalls along the downwave boundary of the domain, and its computational convenience allows it to be applied to large coastal regions to study wave refraction and diffraction. The method has been tested for several cases, and some results are presented. The model compares very well with other model solutions and observed data. 1988.

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