[Jan.Östh]

Dear all

I'm planning to do some pre-processing of external aerodynamics cfd simulations in Paraview. I have figured out how to compute the pressure drag in Paraview, and the friction drag shouldn't be any problem either.

My question regards the calculation of the accumulated drag over a body, that is, to compute the drag on the body as a function of the body's length. Does anyone know if it is possible to combine filters to get this, or if there's a pre-defined filter that can be used.

Best regards
Jan

[Jan.Östh]

To be a little more general for those of you not familiar to the concept of cumulative drag on bodies, I will try to explain in general terms what I want to accomplish.

I have a closed body surrounded by the fluid flow. The streamwise direction is aligned with the x-axis in a Cartesian coordinate system. On the body I have a property F = F(x,y,z) for all (x,y,z) on the body.

The function F_acc = F_acc(x'), which is what I want to compute, is then given by the integral equation F_acc(x') = Int_{delta Body(x')} F dS

Here, the surface "delta Body(x')" is a subset of the original body, defined by the local coordinate x'.
x' starts at the front of the body and extends downstream in the direction of the x-axis in the global coordinate system. Thus, for instance, delta Body(x' = 0.5) represents cutting the original body in half and keeping the front part.

The question regards if it's possible in a easy way to compute the integral Int_{delta Body(x')} F dS in Paraview.

I see a way to do this the 'manual' way, just by slicing up the body into pieces and doing an integration over each piece, and then collecting the results from each integration into a plot, however, it's a bit inconvenient.

Any tips are welcomed.

[Jan.Östh]

I just found out that this feature is already present as an in-built run-time post processing in OpenFOAM v.2.2 and later versions:

http://www.openfoam.org/version2.2.0...processing.php

updated forces - forces and force coefficients can now be additionally written into data bins, along a user-defined direction, as shown below for the motorbike tutorial case:

I was still using v2.1.