[Davitt]

Hello everyone,

I realize this may be a bit of an elementary question, as such I'm posting it here in the main forum...

I'm trying to calculate the Total Drag on a curved 3D surface. I know that total drag consists of both pressure and friction drag.
Pressure drag is calculated by integrating the normal pressure/stress on the surface body while the Friction drag is calculated by integrating the viscous/shear stress on the surface body.

I'm using COMSOL and it provides the x, y and z components of normal pressure/stress and viscous/shear stress. I understand how to use this to calculate the Total Drag on a 2D planar surface.

My question is how do I use this information to calculate the Total Drag on the 3D curved surface?

Any help will be greatly appreciated (also if anyone knows of any resources such a books or anything that can aid in understanding this topic better please mention them)

Thanks
Davitt

[tas38]

Each face of the surface will be defined by a local normal. Projecting the local pressure
and shear stress onto the normal and tangential directions, respectively, and multiplying by the area of the face provides the contribution to the total drag for that face. Sum up all the faces and you have the total drag.

[Davitt]

Thanks tas38...I'll give it a shot

Davitt

[Davitt]

Hey tas, quick question...you mentioned that each surface will be defined by a local normal. Do you think that this will also be the case with a cylindrical coordinate system?

[tas38]

Yes. Applies to cylindrical coordinate system as well. If cartesian, basis vectors of the normal are (x,y,z). For cylindrical, the basis vectors for the normal are (r,$\theta$,z)