SimScale CAE Forum

Drag Coefficient result?


Hi , I am trying to find the drag coefficient for a body, however when I set up a result control I get one value, but when I go into para view and do calculations though there I get another value.

I get a much lower drag coefficient in para view, then in the result control, so my question is how is Simscale calculating the drag coefficient?

In ParaView I use this equation for drag coefficient : Cd = D / (A * .5 * r * V^2)
where D, drag is in newtons, A is reference in meters, r is density of fluid, and v is velocity of fluid.

Post Processing Viscous Forces

Hi @bluematt2002!

These resources might be helpful for you:

Also feel free to share your project with us so that we can see what setup you have chosen.




@bluematt2002 I presume you are neglecting viscous forces in your paraview calculation? The platform takes this into account for drag coefficient.

You can add the wall shear stress as a result control and use it to calculate the drag component due to viscous forces. If this still produces different results, can you share your method of calculation in paraview?



yes I have wall shear stress as a result control, however I don’t know how to incorporate this into the equation.
My current set up is just calculating drag, then I find the drag coefficient by hand as that is a little faster.
in ParaView, to find drag I have: Normals_zp-1


So for pressure forces you probably do surface normals times pressure. Then integrated respect to area will give forces in x, y and z. For viscous wall shear stress is just force/area so you can do wall shear integrated respect to area, giving the viscous forces in cuz, where the z components in your case should give the total drag force to use in your hand calculations.



what do you mean by integrated? how do I integrate with the calculator filter?

Integrate Variables?


Hi @bluematt2002, yes integrate variables.



When I integrate the wallshearstress_z, is the result given in Pa?


The theory is that tau=f/a integrated f/a.da=f therefore Newton’s.