CFD Online Discussion Forums - Finding out Thrust and Moment of Verical Axis Propeller

Create a report definition that computes the desired forces and moments.
Plot these forces and moments to the screen during the solve process. (Optional).
Output these values using the Report Files tool and perform statistical calculations with 3rd party software (eg. Excel, MATLAB). (Optional).
Create custom field functions of the force and moment reports.
Select the field functions from the Sampling Options dialog box on the Run Calculations task page.

Fluent will then compute the statistical properties for the reports you have setup at the specified time intervals and make that information available to you for post processing within Fluent.

See Section 29.14.4. Postprocessing for Time-Dependent Problems
of the Fluent User Guide for more information.

Quote:

If you enable the Data Sampling for Time Statistics option in the Run Calculation Task Page (see Performing Time-Dependent Calculations for details), ANSYS Fluent will compute the time average (mean) of the instantaneous values, the root-mean-square, and the root-mean-square-errors of those quantities and custom field functions that are enabled/selected in the Sampling Options dialog box.

The Time Sampled displays the time over which data has been sampled for the postprocessing of the mean, RMS, and RMSE values. For most quantities, as long as the time step size has been constant, dividing this by the time step size yields the number of data sets that have been collected. However, special consideration is required In the case of discrete phase quantities. As noted in Reporting of Unsteady DPM Statistics, sampling of DPM quantities occurs only when parcels pass through a cell, not necessarily at each specified sampling interval. Therefore, the number of samples of the DPM quantities taken during the sampled time period is stored in the separate postprocessing variable, Accum DPM Parcels in Cell. If the time step size is varied, every contribution of data sets sampled is automatically weighted by the current time step size.

The mean, root-mean-square(RMS), and root-mean-square-error (RMSE) values for solution variables will be available in the Unsteady Statistics... category (or the Unsteady DPM Statistics... category for discrete phase quantities) of the variable selection drop-down list that appears in postprocessing dialog boxes. For example, in the Contours dialog box, you could select Unsteady Statistics... and RMSE-uns-custom-functon-0 for the Contours of drop-down lists in order to display the root-mean-square-errors of a custom field function named uns-custom-functon-0.