COMPARISON OF ADCP MEASUREMENTS AND 3D LARGE-EDDY-BASED SIMULATIONS OF FLOW IN SMALL, SHALLOW QUITZDORF RESERVOIR

摘要

ADCP flow measurements were done at two locations within the shallow, polymictic Quitzdorf Reservoir in Saxony, Germany. Both measured profiles yield time-averaged velocity distributions almost opposed to the recorded wind direction. A three-dimensional barotropic Finite Element model based on an anisotropic Large-Eddy turbulence closure scheme is used to reproduce the flow field. By systematically varying the two major model parameters, the SMAGORINSKY coefficient c_s and the absolute bottom roughness k_s, and by comparing the results to the measurements, two parameter combinations with similarly good results can be found. In either case, the model reproduces the measured velocity profiles very well both in magnitude and in shape, which confirms the performance of the turbulence model and the appropriate choice of boundary conditions. The hydrodynamic model explains the discrepancy between wind and flow directions and thus helps to understand the global circulation pattern in the reservoir for the given meteorological conditions. The ambiguity in choosing the best parameter combination may be attributed to the 2D turbulence structure within the water body.