[palarcon]

Hello everybody

I'm working on topology optimization with OpenFOAM and I'm using and adapting the solver adjointShapeOptimizationFoam.
In order to do that, I need to compute and print the objective function used on that solver (which is not the same used on the paper which is based on).
The real objective function used in this solver is the total pressure drop, which mathematically is



which is the total pressure at the inlet minus the total pressure at the outlet.
I'm not sure about the implementation into my solver, mainly for the differential part .

My current implementation is

objective_inlet  = sum((p.boundaryField()[objPatchList[0]] + 0.5*magSqr(U.boundaryField()[objPatchList[0]])));
objective_outlet = sum((p.boundaryField()[objPatchList[1]] + 0.5*magSqr(U.boundaryField()[objPatchList[1]])));
objective = objective_outlet - objective_inlet;

where objPatchList[0] is the inlet and objPatchList[1] is the oulet.

My question is, should I multiply objective_inlet and objective_outlet by mesh.magSf()[objPatchList[X]] in order to account for the differential in the analytical expression?

PS: I know that I posted a similar question some time ago, but my knowledge of the problem was different at that time.

[Bloerb]

You need to multiply each face value with its area before the summation.

const scalarField& pFace = p.boundaryField()["inlet"];
const scalarField& areaFace = mesh.magSf().boundaryField()["inlet"];

areaPatch = sum(areaFace);
pressureSum = sum(pFace);
IntegralPressure = sum(areaFace*pFace);

// Is not equal to 
IntegralPressure = areaPatch*pressureSum

You might also want to consider gSum...

[palarcon]

Sorry for the late reply, but I was solving other problems related to my code.
I'm trying to code what you suggest me, but when I try to add the lines I have compilations errors.
For example, if I only add the first line

const scalarField& pFace = p.boundaryField()["inlet"];

I get the following error

error: invalid conversion from ‘const char*’ to ‘Foam::label {aka int}’ [-fpermissive]

do you have any advise?

Originally Posted by Bloerb

You need to multiply each face value with its area before the summation.

const scalarField& pFace = p.boundaryField()["inlet"];
const scalarField& areaFace = mesh.magSf().boundaryField()["inlet"];

areaPatch = sum(areaFace);
pressureSum = sum(pFace);
IntegralPressure = sum(areaFace*pFace);

// Is not equal to 
IntegralPressure = areaPatch*pressureSum

You might also want to consider gSum...

[palarcon]

I was able to code all of the previous, but my last question is, which definition of IntegralPressure is the correct one for my case?

Originally Posted by Bloerb

You need to multiply each face value with its area before the summation.

const scalarField& pFace = p.boundaryField()["inlet"];
const scalarField& areaFace = mesh.magSf().boundaryField()["inlet"];

areaPatch = sum(areaFace);
pressureSum = sum(pFace);
IntegralPressure = sum(areaFace*pFace);

// Is not equal to 
IntegralPressure = areaPatch*pressureSum

You might also want to consider gSum...