INFLUENCE OF 2-DIMENSIONAL NONUNIFORM CUR RENTS ON SURFACE-WAVES

Transformation of quasi-monochromatic upstream surface waves propagati ng in a locally two-dimensional nonuniform perturbation of a current i s investigated theoretically and experimentally. A model equation gove rning surface wave amplitude has been derived and solved numerically. The evolution of an initially uniform field of surface waves when the current is suddenly perturbed at an instant is studied within the fram ework of this equation. It is found that there are some distinguished directions, making an angle of about 55 with the current velocity, in which the main variations in surface-wave amplitude occur. The spatial size of the region where the transformation of surface waves is subst antial is much greater than the spatial size of the localized perturba tion of the current. The theoretical model was examined experimentally in a laboratory tank. The nonuniform current was created by a flow ov er an ovaloid and may be considered to be two-dimensional and nonunifo rm near the water surface. The surface waves were generated by a mecha nical wave generator. The two-dimensional distribution of surface-wave amplitudes was registered. The numerical computations of the distribu tion of surface-wave amplitudes performed specially for the experiment al conditions have shown good agreement between experimental data and calculations.