Chimera remove strategy solve

[adityaghantasala]

Description
Following the issue #6748 and the recommendation of the technical committee, the following PR removes the explicit Solve() function calls from the fs strategy of the chimera application.

Changelog
Adds a local SolveStrategy function to the fs_strategy of the chimera app. And uses it to solve the momentum and pressure strategies. This function calls the Initialize, InitializeSolutionStep, SolveSolutionStep and FinializeSolutionStep in that sequence and returns the norm of the solution vector back.

[philbucher]

this is exactly what one should NOT do
=> those calls come from the AnalysisStage and shouldn't be done internally

[adityaghantasala]

For fractional step strategy, this is not possible as there are two (momentum and pressure) internal strategies which should be called at different places. That is why it is done like this.

[adityaghantasala]

Check how and where this function is called and used.

[philbucher]

Then I guess the FractionalStep Strategy hasn't been refactored yet
@rubenzorrilla can you comment?

[adityaghantasala]

I believe that for fractional step solver, this is inevitable !
Each "Solve" of the fractional step looks something as follows

SolveSoltuionStep() # Of complete fractional step solver 
    SetFractionalStep(1)
    TillConvergence :
        SolveMomentumStrategy() # HERE : SolveStrategy() is used

    ComputeOSSProjections()
    Compute/Update/Backup Pressure()
    SetFractionalStep(2)
    .... BunchOfOtherOpps()
    SolvePressureStrategy()  # HERE : SolveStrategy() is used
    UpdateEndOfStepVelocity()

So I am not sure if this would fit in the AnalysisStage. Also AnalysisStage does not have access to all those intermediate steps and functions !

[philbucher]

I think instead of SolveStrategy only SolveSolutionStep should be called

[rubenzorrilla]

I didn't have time to remove the Solve from the base FSStrategy. In any case, I think it would be better to first take care of that and then update the Chimera one accordingly.

[adityaghantasala]

@rubenzorrilla Thank you for the comment. If you have gone through my changes here and you say this is the way to go , I can do it in the fluid dynamics application.