A calibration calculation of the drag coefficient of simple bodies
 

Good day.

To calibrate the calculations, we performed a test calculation of the drag coefficient and resistance force for bodies of a simple shape.
Cylinder - 0.77
Cylinder by face - 1
Cube - 1.17
Square plate 1.84
Hemisphere by face 0.67
Hemisphere 0.66
Sphere 0.066
Airfoil 0.07

Flow 3 m/sec2
Case prepared in CfdOF for FreeCad

Drag coefficient is about 15% above average published experimental values
Airfoil have the same coefficient as sphere.

Calibration it is need for catamarans hulls hydrodynamic passports.
Any advice for more accurate calibration is really appreciated.

Sphere pressure and flow velocity
Attachment 94177
Cube pressure distribution
Cube flow velocity
Attachment 94180
Attachment 94181

You should try to run tutorial example: tutorials/multiphase/interFoam/RAS/DTCHull


It should match this reference:
Reference for the Duisburg Test Case (DTC):
Moctar, O. E., Shigunov, V., & Zorn, T. (2012).
Duisburg test case: Post-Panamax container ship for benchmarking.
Ship Technology Research, 59(3), 50-64.
DOI:10.1179/str.2012.59.3.004



These cases have a free surface. Next modify the case to match your catamaran.


On your validation effort:

1. The sphere plot looks symmetric front to back. That should not be, because there will be separation.
2. The drag on the airfoil is too high.
3. The plots don't show the grid which is a must for troubleshooting.