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• #6145
sahilbhapkar30
Participant

Hello,

I would like to ask if I could calculate drag and lift forces on my cuboid geometry. Is it possible to calculate it? I tried implementing the Drag setup as per the cylinder2d/3d setup but I am getting infinite value for my cuboid geometry. Is it only that drag and lift can be calculated for spherical bodies?

Thankyou

#6146
Keymaster

No, the functors used to calculate lift and drag in e.g. cylinder(2,3)d support arbitrary shapes.

However, I am unsure what you mean by “drag of cuboid geometry”. The `CuboidGeometry` class describes the block decomposition of the simulation domain and not the obstacle geometry of which you want to calculate flow coefficients.

#6148
sahilbhapkar30
Participant

When I tried implementing the drag and lift for my inlet and outlet which are in cuboid shape,

SuperLatticePhysDrag3D<T,DESCRIPTOR> drag( sLattice, superGeometry, 3, converter ); // for inlet
SuperLatticePhysDrag3D<T,DESCRIPTOR> drag2( sLattice, superGeometry, 4, converter ); // for outlet

T dragA[3];
int input1[0];
drag( dragA, input1 );
clout << “; drag_inlet=” << dragA[0] << “; lift_inlet=” << dragA[1] << endl;

T dragB[3];
int input2[0];
drag2( dragB, input2 );
clout << “; drag_outlet=” << dragB[0] << “; lift_outlet=” << dragB[1] << endl;

I am getting inf value for drag_inlet and drag_outlet and same for lift as well. Could you tell me the reason for this inf value?

I did not understand the meaning of the sentence you said in your comment:

The CuboidGeometry class describes the block decomposition of the simulation domain and not the obstacle geometry of which you want to calculate flow coefficients.

Thank-you

#6158
Keymaster

The drag functor assumes that the given material number / indicator describes the boundary of the object for which the drag and lift coefficients are to be computed. You can see this in action e.g. in our cylinder(2,3)d examples.

What I meant by my other comment is that the cuboid geometry and material numbers describe different concepts. Asking for flow coefficients of a `CuboidGeometry` doesn’t make sense in OpenLB terminology. However, rereading your initial comment: Maybe you did not mean the `CuboidGeometry` class but the flow around cuboid shapes?

#6161
sahilbhapkar30
Participant

Yes,actually I mean the flow around the cuboid shapes.

As per my above comment, I have described my drag definition at the inlet and outlet. However, I am getting infinite value at the inlet and outlet.

I tried setting the drag definition even for bstep2d/3d (Cuboid Shape geometry) and found similar infinite value for drag coefficient and lift. That is the reason I asked whether Drag force is calculated using Stokes Law. If it is calculating by Stokes Law, the Radius of Curvature in the cuboid geometry would be taken to be infinite.