NUNERICAL SIMULATION OF GYRES IN LAKE BIWA

Abstract

The formation process of three gyres in Lake Biwa, as observed using ADCP, has been simulated by using Large Eddy Simulation (LES). Two different dynamic subgrid-scale (SOS) models-Dynamic Mixed Model (DMM) and Mixed Scaling Formulation Model (MSFM)- are employed to describe stratified non-isotropic SGS stress due to the large disproportion between horizontal and vertical gridspacing in the computational grid.
The driving force of gyre formation is assumed to be differential heating due to heat volume differences between middle-lake and shoreline areas. This condition was created in the simulation by setting the initial temperature distribution in the lake based on field observations. Significant gyre formation patterns are calculated by LES both with DMM and MSFM. Due to the huge disproportion between horizontal and vertical grid spacing, the isotropic SGS model (such as the Smagorinsky Model) does not perform well.