I looked at your jpeg. You could do this in Flow Simulation by making a goal for drag force and using water as the fluid. If you don't have Flow Simulation, maybe FlowXpress can do it.
If the probe is simple as you show you should find resistance for a round object in your fluids book. Don't need the complication of CDF when there is a simpler (and arguably more accurate) solution. Do students still keep books?
I'm with Mark, I am a little rusty so double check me on this.
Get Drag Coef from Chart using Re #
For a cylinder
Re#= (Diam Cyl*Density*Velocity)/Absoulte Viscosity
Area = Diameter*Length
Density = 62.3lbm/ft^3
Absolute Viscosity = 2.050E-5 lbf-sec/ft
gc=32.2 lbm-ft/lbf-sec^2 (for a cylinder)
I looked at the jpeg only. Not sure what the scale is but you should be very concerned about VIV (vortex induced vibration). You can do hand calcs to get the natural frequency of vibration to not be close to the range of vortex shedding frequencies that will be present. You also need to consider the added mass of the fluid and the probe in calculating the natural frequency of the probe. Other things that maybe important are the stiffening effects of the mean drag load on the natural frequency, the stiffness of the support system and actuator as well. I would stick a fairing around the probe but it depends on how the former works out.