For this simulation I think no special consideration for force calculation is required just be sure about the values of x, y and z force vectors for force calculation. For more accuracy the fluid zone should be rotated by using frame motion in the Cell Zone Conditions of the solver if not done already. To know more on different options available for setting frame motion to cell zones, please refer to the link of Ansys Fluent User Guide given below
7.2. Cell Zone Conditions (ansys.com)
Velocity contour would help in resolving the issue.
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