This keyword allows the user to specify the criterion used to automatically stop a run when it converges.

Note that this keyword should not be used as the sole method for determining convergence. Convergence should be monitored throughout a run by tracking residuals, integrated forces, moments, and mass flow, and/or flow variables at particular locations. See the Convergence Monitoring section for more detail.

Structured Grids

The options available for structured grids are:

	LEVEL		Check for maximum residual less than val.
	ORDER		Check for reducing maximum residual by val orders of magnitude.

When the specified convergence level has been reached for all zones, the calculation will stop. The default, when the CONVERGE keyword isn't used, is a four-order of magnitude decrease in the maximum residual.

If Newton iteration is being used, this keyword specifies the convergence criterion within a Newton time step. The overall global convergence criterion is specified using the NEWTON keyword.

See Also: LOADS, HISTORY, NEWTON, TEST 128

Unstructured Grids

For unstructured grids, specifying CONVERGE LOAD tells Wind-US to stop the calculation when the forces and/or moments on user-specified surfaces (and/or subsets of surfaces) have leveled off within a specified tolerance. The LOADS keyword block must also be used to specify the surfaces and/or subsets, and whether forces and/or moments should be computed. The forces and moments used with CONVERGE LOAD will be the sum of the pressure and viscous values, if VISCOUS is included in the surface/subset specification in the LOADS block.

As part of the process, the flux dissipation and/or slope limiting parameters are adjusted in each zone to drive them to limiting values. For the Rusanov scheme, the flux dissipation and slope limiting parameters are driven to 0.1 (or lower) and 3.5 (or higher), respectively. For the Roe scheme, the slope limiting parameter is driven to 2.5 (or higher). CONVERGE LOAD cannot be used with the HLLE scheme. The starting values for these smoothing parameters are normally set using the SMOOTHING keyword, but should be defaulted when the CONVERGE keyword is being used.

Convergence is checked every ncyc cycles, with a default of 50. The flux dissipation and/or slope limiting parameters are adjusted when the relative changes in the forces and moments on the specified surfaces within the current zone are all below the value val. The default for val, when the CONVERGE keyword isn't used, is 0.2.

Convergence is assumed when the flux dissipation and/or slope limiting parameters have reached their limiting values in all zones, and the maximum relative change in the forces and moments, summed over all the zones, is less than 0.01. (The convergence criterion of 0.01 may be changed using DEBUG 24).

See Also: LOADS, SMOOTHING, DEBUG 24