# Torque on solid surface

Hi everyone,

I’m trying to calculate torque on a solid surface, by the method already included in Palabos it always return the force on the whole surface. As momentumBGK, we can just get the drag and lift in the example ‘computeDrag’.

Do anyone know how to do this simply?

Thanks,
C.l

Hi C.I,

I think that what you are looking for is in palabos/src/offLattice/
-> ReduceImmersedTorque3D : public PlainReductiveBoxProcessingFunctional3D

Isn’t it?

mars

Thanks Francesco, nice to see you again.
I’ve also noticed that function. I have a bit questions, that can I also use this function for all other kind of offlattice BC or it is just for immerseBoundary? Furthermore, is can I get the pressure on the geometry surface to do some post procession?

Thanks again,
C.l

Hi C.I.

I think that if you represent your wall with ImmersedWallData3D you can use it with whatever offLattice boundary condition as long you store the force in the vertices. Anyway, if you can’t, you can still take inspiration to write your dataprocessor following ReduceImmersedTorque3D as a model.

mars

Francesco,

Thanks, I know that now. So there’s basically no different from Offlattice and Immerse BC in most result? Then, for convenience in Palabos(implemented) I can directly use IBM to make things easier.

C.I

I’m not sure to understand and if I’m able to answer. But I guess that the point is not the type of boundary condition, but with data-structure you are using to represent the surface…
In the immersed boundary method, in palabos, the surface is represented with a collection of points (particles) with normals, but this doesn’t mean that with the same information you can’t implement an other boundary condition or you can not use this representation to do other operations…

mars

Yeah, thank you very much Fran.
I think that’s what I need. So the surface in PALABOS will be represent by a structure of points? Then I can also treat on these point. I hope am right.
C.l