[mo_na]

Dear all,

I am trying to calculate the drag coefficient for a body, that is doing a pitch motion in regular waves. (I attached a sketch to give you an idea of the setup.)

Drag coefficient: cd=2*Fd/(rho*U*|U|*A)
Fd: Drag force, calculated with forces function
A: reference area
rho: density

I figured that I can't use the forceCoeffs function, because U is not the free stream velocity in this case, but the relative velocity between the body and the fluid particles.
So the velocity I need here is U=u(t)-v(t), where u(t) is the flow velocity in drag direction (x) and v(t) the velocity of the body, also in x-direction. (Please correct me if I am wrong here)

Now I am wondering if any of you have some advice how to obtain those two values.

1)u(t)
This value varies throughout the flow filed around the body, so should I set several probes and then take an average value or try to pick a characteristic point?

2)v(t)
I am already outputting the angular velocity omega of the body. With v=omega*radius I will obtain the tangential velocity. But how can I obtain the x-component from that?


My plan is to calculate cd(t) in postprocessing with all these above values.
Any suggestions on how to do this are very appreciated!

Cheers,
Mona