calculation of coeff. of drag of cylinders (M=1.3)

jehanzeb

i have problems calculating coefficeint of drag using fluent; for the flow over cylinder (L/d = 10) ,Mach no.= 1.3 i am solving in 2-D

The flow field seems to be ok , but the problem is with the "refference values" i set for the calculation of coefficients. I have given the frontal area according to the problem and the values such as velocity and rho is of free stream.

The Question is:

How does i get to know the right valvue for the "Depth"? (as it changes the coefficient drastically). "Length" on the other hand does not have an influence. Fluent manuall also does not say much about it.

I am solving in 2-D with L/d = 10 and length of the cylinder parellel to the flow direction.

What will we set the "Depth" in "Refference Values" and why ?