Department of Oceanography
Dalhousie University
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PO Box 15000
Halifax, NS, B3H 4R2
Canada
Not updating viscosities on a restart would mean there is no recalculation (rescaling) of viscosities during nonlinear iterations. During the calculations the gauss point viscosity values that are read from the restart file are used and are not reset. No resetting occurs during either time stepping or within nonlinear iterations.
The purpose of not updating viscosities is to determine the sensitivity of the model behaviour to gravitational forcing alone at a certain point in the calculation. The calculation is restarted with the model viscosity values that were computed for the timestep saved in the restart file. These viscosities are treated as linear 'effective viscosities' in order to decompose the velocity field into tectonic (forced by the velocity boundary conditions) and gravitational components. For the restart the velocity boundary conditions are set to very small values, so that the calculation calculates that part of the velocity field that is gravitationally forced. The tectonic component of the velocity filed is calculated by subtracting the gravitational velocity field from the total velocity field. This method of computation should only be used for this type of decomposition at a particular time. It is not valid for multi-timesteps.
Note: Remember to reduce the velocity boundary conditions to small values or zero.
Users should also make sure that this type of decomposition is valid for their model.
This page was last modified on
Wednesday, 03-Aug-2011 10:07:51 ADT
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