External Flow for a Truck: Exercise 6—Analyzing Results
This exercise describes how you analyze the results during and after the simulation. The visualization and analysis of the results proceed through contours on sections, plots and streamlines. To hide CAD surfaces (not the fluid domain), switch between Flow Analysis Bodies and CAD Bodies in the Show group. Clear any variable display by selecting No Selection in the Legend drop-down. Click XYPlot Panel to view the XY Plot.
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1. To show/hide selected geometric entities, click Show in View Panel.
2. To change the color scheme, click on More in the Legend and select between Blue Red and Blue Purple.
Plotting the Pressure Force
1. In the Flow Analysis Tree, under Boundary Conditions > General Boundaries, click Default.
2. Select all the boundaries under Default.
3. Click XYPlot. A new entity xyplot1 is added in the Flow Analysis Tree under Results > Derived Surfaces > XY Plots.
4. Select xyplot1.
5. In the Properties panel, set Variable to [Flow] Pressure Force X.
6. Set Mode to Combine Lines.
7. Click Stop and Run, if required.
Plotting the Shear Force
1. In the Flow Analysis Tree, under Boundary Conditions > General Boundaries, click Default.
2. Select all the boundaries under Default.
3. Click XYPlot. A new entity xyplot2 is added in the Flow Analysis Tree under Results > Derived Surfaces > XY Plots.
4. Select xyplot2.
5. In the Properties panel, set Variable to [Flow] Shear Force X.
6. Set Mode to Combine Lines.
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The drag force on the surfaces of the truck is the sum of the pressure and shear forces.
7. Click Stop and Run, if required.
Plotting the Drag Coefficient
1. In the Flow Analysis Tree, under Physics, select Common.
2. Click XYPlot. A new entity xyplot3 is added in the Flow Analysis Tree under Results > Derived Surfaces > XY Plots.
3. Select xyplot3.
4. In the Properties panel, set Variable to Drag force or Coefficient_of_Drag.
5. Click Stop and Run, if required.
Viewing an Isosurface of Points with Pressue At 0
Pressure
Pa
1. Click Flow Analysis > Isosurface. A new entity Isosurface 01 appears under Derived Surfaces in the Flow Analysis Tree.
2. Select Isosurface 01.
3. In the Properties panel, Model tab, set values for the options as listed below:
Isosurface VariableVelocity X: [m/s] : Flow
TypeBelow Value
Value—0
4. In the Properties panel, View tab, set values for the options as listed below:
VariablePressure: [Pa] : Flow
Min— –75.0
Max—0
Viewing the Streamlines in the Domain
Velocity X
m/s
1. In the Flow Analysis Tree, under Boundary Conditions > General Boundaries, click Default.
2. Under Default, select CAB and TRAILER.
3. In the Properties panel, Model tab, under Streamline, select the following values for the options listed:
Release ParticleYes
Number of Particles—70
4. Add Streamline01 to the Flow Analysis Tree and select it.
5. In the Properties panel, Model tab, select the following values for the options listed:
Line Thickness—0.03
Animation Time Size—0.1
6. In the Properties panel, View tab, select the following values for the options listed:
VariableVelocity X: [m/s] : Flow
Min— –15
Max— 24
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