Experimental study on the influence of drift flow on the propagation characteristics of wind waves in shallow lakes

Wind waves are mostly in the development stage in areas such as shallow lakes and other places with limited wind blowing range and water depth. The surface drift flow generated by wind may affect the propagation characteristics of the wind waves. Wave parameters, such as wave celerity and wavelength, are difficult to be obtained through the dispersion relations of the linear wave theory. To accurately forecast the parameters of the wind wave in shallow lakes, the influence of drift flow on wind wave propagation in a wind tunnel was investigated by considering the characteristics of shallow lake's limited blowing range and water depth. The results showed that the drift flow, stokes flow and surface flow were all positively correlated with the wind speeds. With the increase of wind speed, the ratio of the drift flow to the surface flow gradually decreased and stabilized at the value of 75%. The drift flow could promote the wave celerity and wavelength, especially for small-scale waves. Nonlinearity of waves suppressed the effect of drift flow on the wave celerity and wavelength. The empirical dispersion relation of wind waves and empirical relation of dominant frequency wave celerity, considering the influences of drift flow, are established.