Type 1 Analysis Results (Output File)

[AircraftPerson]

Hi, I have a few questions regarding the interpretation of loads and moments in a Type 1 Analysis Results. I’m running the v7.57 version of flow5. After a simulation has completed and a specific angle of attack is selected to view the results (output files) I would appreciate some clarification on the following points:

1. Coordinate System
   • What coordinate system are the reported loads Fx, Fy, and Fz expressed in?

2. Output File Force Summation
   • I have observed that the summed value of Fx from the output file for the lifting surfaces appears to be the Geometrical Axes Value – Wind Axes Value (Fx_geo – Fx_wind). Is this correct?

3. Moment Coordinate System
   • In which coordinate system are the reported moments (Cm_i, Cm_v) and Bending Moment in?

4. Strip Forces (Nx, Ny, Nz)
   • In the detailed strip output, what coordinate system are the force components Nx, Ny, and Nz defined in?

I would greatly appreciate any clarification that can be provided, as I would like to ensure I am interpreting the output data correctly.
Thank you very much for your time and assistance.

[techwinder]

1. Geometry axes
2. Not sure what is meant by "force summation"?
3. All values are in geometry axes
4. Geometry axes
   André

[AircraftPerson]

Thank you for answering the questions, André.

In regard to 2., force summation as in, when I sum the forces for Fx for a lifting surface for a single angle of attack value in excel (in column P), the sum of those forces in equal to the value 'Fx_Geo - Fx_Wind' as seen in the flow5 in the bottom-left box (which has the information about the current run - polar type, method, inertia, aero derivatives, total forces). Is this intentional?

Thank you.

[techwinder]

The program outputs Fx_geo in the file. It is a numerical coincidence if it appears to be the difference between forces calculated in wind and geometry axes.
The values in the operating point's property box are not calculated by pressure summation but from the cross-flow kinetic enery in the far-field plane. This far-field method is more precise and reliable than the force obtained by pressure summation. The pressure forces are only used to calculate moments.
André

[AircraftPerson]

Okay, understood.
Thank you for the response André.