Most general post-processing can happen within ANSYS Fluent itself; however, for more powerful tools to visualize complex datasets, Ensight has superior performance and capability.

Pressure Contour Sweep with Line Integrated Convolution (Surface Flow Display)

A pressure contour sweep with line integrated convolution (LIC) from the front and back of the car is a great analysis tool as it shows both the pressure and flow field around the car. This video analyzing an F1 car spends over half of the time looking at a pressure contour sweep with LICs.

To start, import the exported Ensight Case Gold file into Ensight. If you want to show the symmetrical view, select all the parts and then click on “visual symmetry”.

Open

If the origin of the part is not on the symmetry plane, we will have to create one. To do this, select the symmetry plane, right click, and select “place cursor”

Open

Select all the parts again (selecting the symmetry plane deselects everyting else). Then back in the part visual symmetry window, make sure “specify origin” is checked, and click “get cursor tool”. Set the type from none to mirror. Select one of the mirror planes and check to ensure it is properly mirrored.

Then hide everything except for the enclosure. Create a clip plane and select the enclosure. Set the mesh slice direction to either X, Y, or Z. Select “create with selected parts”. In the clip parameters box, you can move the clip plane forwards and backwards along the selected slice direction.

To create the pressure contour on the clip plane, click on the contours button, set the variable to pressure, and select the clip plane before creating the contour. This will create a contour plot that does not show any color plot but instead the pressure isobars.

To display the colors, right click on the clip plane->color by->select variable->scalars->pressure. The clip plane should now be colored. The bounds of the pressures are automatically set and can be too large, resulting in a clip plane that appears to be only one color (that being said, the pressure can be visually constant along smooth sections, so moving it to the front of the nosecone or the wings can easily show high or low pressure regions if the pressure range is correct). To fix this, right click on pressure in the variables window and select “edit palette”. Play with the lower and upper bounds of the pressure until the results are good.

You can now hide the enclosure and contour part so the only visible item is the clip plane with the pressure distribution. If you edit the clip plane and move the clip parameter slider, you will see the clip plane move along the length of the car with the pressure changing as it moves.

To add LICs to this cross section, select the clip plane and click on the “color/transparency” button to open the surface property editor tab. Scroll down to the surface flow display tab and select properties. The LICs should be representative of the velocity, but since the velocity at the surface of the car is zero due to the no-slip condition, we must offset the surface on which Ensight measures the velocity to show a representative condition. To do so, select create/edit a surface vector, select velocity as the variable, and set the offset to something small (0.001 for example).

Click create. The variable for the surface flow display should automatically be set to it and it should be something along the lines of ENSSurfVel. Int he surface property editor window, check the “show flow texture” box and the LICs should appear on the clip plane.

Now if you edit the clip plane and move it along the cars length, you should see both the LICs and the pressure contour adapting.

To create a pressure sweep animation of this from the front to back of the car, first determine the clip max and min position, number of frames, and animation delta.

Clip max/min: Where the clip plane starts/ends. Generally this should be placed right behind the high-pressure region in front of the nose, and can end when the car’s wake begins dissipating.

Number of frames: Also the number of slices the pressure surface sweep will take along the car.

Animation delta: How far along the car’s length the clip plane will move with each frame. It is equal to the difference of the clip maximum and minimum positions divided by the number of frames.

As you sweep the clip plane, the Value box shows the current position. For this example, we will take the front of the car as 1.739841e+00, and the end of the car as -2.447472e+00. If we want 250 frames, then the animation delta will be .

Move the clip plane all the way to the beginning (the max position previously set). This should be where you want the animation to begin. Next, create the flip book animation by clicking the flipbook button in the toolbar.

Check to make sure the clip plane is selected the view is correct, then click the Load button to begin generating the frames. If the animation appears to be going backwards, top the generation, and change the sign on the animation delta value of the clip plane to the opposite.

The flipbook window should automatically open. You can play and step through the frames with the controls in the window.

To export this animation, select file->export->animation. Select the checkmark for both flipbook: play and reset.