Numerical investigation on inhomogeneous wind and its effects to mass transport

Surface wind is generally considered one of the major forces in shallow lakes as well as large water bodies, as it induces energy that forms horizontal currents over the water surface. Wind is typically inhomogeneous in space, which instantaneously induces distinctive surface movements compared to that of homogeneous wind. In this study, the Weather Research and Forecasting coupled with the Large Eddy Simulation (WRF-LES) model was employed in an attempt to simulate realistic wind over the shallow Lake Kasumigaura of Japan. Based on the modeled data, an integrated wind non-uniformity analysis, which directly derives the coefficient of variance (Cv) for wind speed and direction in various spatial scales using 2D mean filter technique, was developed. With this analysis, the time variation of the mean Cv_spd and Cv_dir were obtained to classify wind speed and wind direction non-uniformity levels. Finally, each representative snapshot of wind cases (spatially homogeneous and spatially inhomogeneous) was chosen based on the corresponding value of wind speed to simulate and develop an understanding of the effects of non-uniformity on mass transport in the lake using a numerical tracking analysis of floating particle. Although different levels of inhomogeneous wind field illustrated their effects on surface particle transport, the effects on this lake environment were relatively minor.