DAObjFuncForce fixedDirection for AoA-dependent drag/lift directions

[walidmoustafabadawy]

Hello everyone,

I'm using DAFoam for field inversion on an airfoil at AoA = 17°, using a mesh aligned with AoA = 0°, while changing the inlet velocity direction and hence the direction of the forces.

When I define the drag and lift directions using fixedDirection (see pic1), I get the following error:

FOAM FATAL ERROR:
the magnitude of the direction parameter is not 1.0!

The case runs fine for AoA = 0° when using:

[1, 0, 0] (Drag)
[0, 0, 1] (Lift)

I tried defining the drag and lift directions in different ways (see pic2). The vector norm prints as 1, but when used in fixedDirection it gives the same error. It looks like there is a strict check on the magnitude of the direction vector to be exactly 1.

Is there a way to go around this, or a recommended way to compute drag and lift aligned with the freestream direction when AoA is introduced via the inlet velocity?

Thanks in advance.

[friedenhe]

Check the flowAxis and normalAxis in your patchV setup in inputInfo. In your case, the flowAxis should be x and normalAxis should be z

[walidmoustafabadawy]

Dear Professor He,

Thank you very much your reply.
I tried explicitly adding the inputInfo/patchV with flowAxis = x and normalAxis = z inside the forces objective, but I am still observing the same issue.
For reference, I am only using a forces objective, and the AoA is introduced directly from the inlet velocity in the OpenFOAM case (not through any daOptions)
I am sharing my runscript below for clarity in case I am missing something subtle in the setup.
I really appreciate your help on this.

################################################################################################
#!/usr/bin/env python

=============================================================================

Imports

=============================================================================

from mpi4py import MPI
from dafoam import PYDAFOAM, optFuncs
import numpy as np
gcomm = MPI.COMM_WORLD

U0 = 51.4815
A0=1
rho0=1

alpha = 17.0 * np.pi / 180.0
dragDir = [float(np.cos(alpha)),0.0,float(np.sin(alpha))]
liftDir = [-float(np.sin(alpha)),0.0,float(np.cos(alpha))]
#print("CD direction:", dragDir)
#print("norm:", np.linalg.norm(dragDir))

Set the parameters for optimization

daOptions = {
"solverName": "DASimpleFoam",
"primalMinResTol": 1.0e-12,
"primalMinResTolDiff": 1e10,
#"primalBC": {"U0": {"variable": "U", "patches": ["inlet"], "value": [U0, 0, 0]}, "useWallFunction": True},
"checkMeshThreshold": {
"maxAspectRatio": 1.0e8,
"maxNonOrth": 70.0,
"maxSkewness": 4.0,
"maxIncorrectlyOrientedFaces": 0,
},

"objFunc": {
    "CD": {
        "part1": {
            "type": "force",
            "source": "patchToFace",
            "patches": ["airfoil"],
            "directionMode": "fixedDirection",
            "direction": [0.956304756, 0.0, 0.292371687],#dragDir,#[0.956305, 0.0, 0.292372],#[1, 0, 0], 
            "scale": 1.0/(0.5*U0*U0*A0*rho0),
            "addToAdjoint": True,
        }
    },
    "CL": {
        "part1": {
            "type": "force",
            "source": "patchToFace",
            "patches": ["airfoil"],
            "directionMode": "fixedDirection",
            "direction":[-0.292371687, 0.0, 0.956304756],#liftDir,#[-0.292372, 0.0, 0.956305], #[0, 0, 1],
            "scale": 1.0/(0.5*U0*U0*A0*rho0),
            "addToAdjoint": True,
        }
    },
},

}

DASolver = PYDAFOAM(options=daOptions, comm=gcomm)
DASolver()
###################################################################################################