OPEN BOUNDARY CONDITIONS FOR A NUMERICAL SHELF SEA MODEL

摘要

The barotropic numerical shelf sea model of the Institute of Atmospheric Physics, Chinese Academy of Sciences, is outlined first. For computing economy, a splitting method is applied by dividing the governing equations into three stages which are integrated with different time-steps. Open boundary conditions suitable for the different stages are derived from the locally linearized versions of the split governing equations. For the adjustment stage, the governing equations are converted to an equivalent set of characteristic equations, which represent waves propagating into or out of the computational domain. The outgoing waves are described by characteristic equations, while the incoming waves are suppressed by a nonreflecting boundary condition. For the development stage, general analytical solutions are found. At outflow points the boundary values at the upper time-level are obtained from data at the present time-level within and on the boundary via the analytical solutions, while the boundary values at inflow points remain constant in time. For the forcing-dissipation stage no boundary conditions are necessary. Numerical verification of the proposed open boundary conditions is described; the results are satisfactory. (C) 1995 Academic Press, Inc. [References: 7]