33.17.1 Solution Steering Dialog Box

The Solution Steering dialog box is used to set the parameters that control the solution steering strategy. Solution steering will typically perform full multigrid (FMG) initialization followed by two iterative stages (Stage 1 and Stage 2). The purpose of Stage 1 is to navigate the solution from the difficult initial phase of the solution toward convergence by insuring maximum stability. During this stage, the solution is advanced gradually from 1st-order accuracy to maximum accuracy (user specified and typically 2nd-order) at a constant low CFL value. In Stage 2, the solution is driven hard towards convergence by regular adjustments of the CFL value to insure fast convergence as well as to prevent possible divergence. In Stage 2, the residual history is monitored and analyzed through regular intervals to determine if an increase or decrease in CFL value is needed to obtain fast convergence or to prevent divergence. See Section  26.19 for details.

Controls

Steering Settings   allows you to modify the steering parameters used in Stages 1 and 2.

Stage 1   allows you to set parameters relating to stage 1.

Duration   is the number of iterations in stage 1. The CFL number used during these iterations is set in the Initial field, in the Courant Number group box.

Stage 2   allows you to set parameters relating to stage 2.

Update the Courant Number   allows you to update the Courant number either Immediately, or After a specified number of iterations.

Courant Number Update Interval   defines the frequency at which the Courant number is updated.

Courant Number   allows you to set the starting ( Initial) and maximum allowed ( Maximum) Courant number values. The solution steering algorithm will not allow the solver to exceed the maximum Courant number, but will allow the solver to use a Courant number less than the initial Courant number if divergence in the solution has occurred.

Explicit Under-Relaxation Factor   allows the solution to be under-relaxed to improve convergence.

Default   resets any changes made to the parameters to their original default values.

FMG Settings   allows you to set FMG parameters. For more information about FMG initialization, refer to Section  26.10.

Number of Multigrid Levels   allows you to set the number of multigrid levels.

Number of Cycles   allows you to set the number of cycles for a selected level.

FMG Courant Number   allows you to set the FMG Courant number.

Default   resets any changes to the original default values.