External Flow for a Truck: Exercise 6—Analyzing Results
This exercise describes how you analyze the results during and after the simulation. To hide CAD surfaces (not the fluid domain), switch between
Flow Analysis Bodies and
CAD Bodies in the
Show group. Click
XYPlot Panel to view the XY Plot.
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.
|  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] : Flow 0 –75.0 |
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 Variable—Velocity X: [m/s] : Flow
◦ Type—Below Value
◦ Value—0
4. In the Properties panel, View tab, set values for the options as listed below:
◦ Variable—Pressure: [Pa] : Flow
◦ Min— –75.0
◦ Max—0
Viewing the Streamlines in the Domain
| Velocity X: [m/s] : Flow 24 -15 |
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 Particle—Yes
◦ 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:
◦ Variable—Velocity X: [m/s] : Flow
◦ Min— –15
◦ Max— 24
