30.4.1 Generating a Force, Moment, or Center of Pressure Report

To obtain a report (for selected wall zones) of forces along a specified vector, moments about a specified center and along a specified axis, or the center of pressure, use the Force Reports dialog box (Figure  30.4.1).

Reports Forces Set Up...

Figure 30.4.1: The Force Reports Dialog Box

The steps for generating the report are as follows:

1.   Specify the type of report in which you are interested by selecting Forces, Moments, or Center of Pressure from the Options list.

2.   Define the settings associated with report you are generating:

(a)   For a force report, enter the X, Y, and Z components of the Force Vector along which the forces will be computed.

(b)   For a moment report, enter the X, Y, and Z coordinates of the Moment Center about which the moments will be computed, as well as the X, Y, and Z components of the Moment Axis along which the moments will be computed.

(c)   For a center of pressure report, define the line (for 2D geometries) or plane (for 3D geometries) on which you want to calculate the center of pressure. The line or plane must have one of its coordinate values fixed (e.g., a line defined as $y=10$). Select the axis ( X, Y, or Z) in the Coordinate group box, and then enter the fixed Value. See the example at the end of this section for further details.

If $F_x$ (the $x$-component of the force) is zero, then either the Y or Z coordinate can be fixed. If $F_y$ is zero, then either the X or Z coordinate can be fixed. If $F_z$ is zero, then either the X or Y coordinate can be fixed.

3.   In the Wall Zones list, select the wall zone(s) for which you want a report of the forces, moments, or pressure center.

If you have a large number of wall zones, it may be useful to specify a Wall Name Pattern and click Match. This selects all of the wall zones with names that match the specified pattern. For example, if you specify out*, all walls whose names begin with out (e.g., outer-wall-top, outside-wall) will be selected automatically. If a wall zone that matches the name pattern is already selected when Match is clicked, it will be deselected. If you specify out?, all walls whose names consist of out followed by a single character will be selected (or deselected, if they are already selected).

4.   Click Save Output Parameter.... The Save Output Parameter dialog box (Figure  30.3.2) will open where you will specify the name of the newly created output parameter, or overwrite an existing output parameter of the same type. The default report name format is report-type-n (e.g. force-1).

After the output parameter is created, it is listed in the Parameters dialog box. You can create any number of output parameters of this report type.

5.   Click the Print button if you want the results displayed in the console window, or click Write... to save it to a file.

If you selected Forces under Options, the pressure force, viscous force (if appropriate), total forces, pressure coefficient, viscous coefficient, and total coefficients for each selected wall zone will be displayed or saved.

If you selected Moments, the pressure moments, viscous moments (if appropriate), total moments, pressure coefficient, viscous coefficient and total coefficients for the wall zones about the specified center will be displayed or saved. Additionally, the moments and coefficients in the direction of the specified axis will be displayed or saved. The report will include the values for the individual wall zones, as well as the net values for all of the wall zones combined. See this section in the separate Theory Guide for details about computing forces and moments.

If you selected Center of Pressure, then ANSYS FLUENT displays or saves the coordinates about which the moment is zero.

You cannot save your output parameter if Center of Pressure is selected.

Note that the reported force and moment coefficients are a function of the values entered in the Reference Values task page (as described in this section in the separate Theory Guide). Therefore, appropriate values must be entered in the Reference Values task page to get meaningful results.

Example

To demonstrate how you would generate and interpret the center of pressure report, consider an airfoil of chord length 1 m (shown in Figure  30.4.2).

Figure 30.4.2: An Airfoil with its Computed Center of Pressure

Open the Force Reports dialog box and perform the steps that follow.

Reports Forces Set Up...

Figure 30.4.3: The Force Reports Dialog Box for a Center of Pressure Report

1.   Select Center of Pressure from the Options list.

2.   Define the line on which the center of pressure will be calculated. In this case, the Y coordinate for the line has a fixed Value of 10.

3.   Select the Wall Zones that are relevant for the computation.

4.   Click Print to have the coordinates of the center of pressure displayed in the console window.

The report generated will be in the following form:

Pressure Center Coordinates (in m): 
	X = 0.41267981
	Y = 10