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Unsteady Setup

12.7.4. Report Generation for Unsteady Case

Create a new drag report definition named unsteady_pod for the drag coefficient on the wall-pod.

Solution → Reports → Definitions → New → Force Report → Drag...

1.Enter unsteady-pod-drag for Name.

2.Enable Report File and Report Plot in the Create group box.

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3.Select wall-pod from the Wall Zones list.

4.Click OK to create the report.

12.7.5. Run Calculations for Unsteady Case

Solution → Run Calculation → Advanced...

•

a.Enter 0.001 for Time Step Size (s).

b.Enter 1000 for Number of Time Steps.

c.Enter 8 for Max Iterations/Time Step.

d.Start recording the transcript.

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Unsteady Setup

File → Write → Start Transcript...

Enter a name for the transcript file.

e.Click Calculate.

It takes approximately 1.7 hours to complete the run on a 12 core machine

f.Stop recording the transcript.

i. File → Write → Stop Transcript...

ii.Save the case and data files ( overset-pod-transient.cas.gz and overset-pod- transient.dat.gz.

12.7.6. Overset Solution Checking

Check overset solution.

Open the transcript file and look for the warning of:

dead->solve cells

Ideally, no cells should go directly from being dead cells to being solve cells. A large number of cells directly converting from dead to solve can affect the accuracy of the solution or cause divergence. If you find that there is a large number of cells that went directly from dead to solve, then you can reduce the time step size to decrease the likelihood of this issue occurring. If there are any dead to solve cells present for this calculation run, the warning is printed as shown below:

WARNING: 1 overset dead->solve cells in interface o-i

Note

Objects move their position with time in transient overset moving mesh cases, requiring dead cells to convert into solve cells. Dead cells do not have proper solution data, so they need to convert to receptor cells to get the required solution information before converting to solve cells. If a dead cell converts directly into a solve cell, it may lack required information and cause an improper result. Refer to "Diagnosing Overset Interface Issues" in the Fluent User's Guide for additional information.

12.7.7. Postprocessing

1.Create contours of static pressure.

Results → Graphics → Contours → Edit...

a.Enable Filled in the Options group box.

b.Ensure Pressure… and Static Pressure are selected from the Contours of drop-down lists.

c.Select the internal surfaces in the list of Surfaces.

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d.Click Display.

e.Close the dialog box.

Note

To capture intermediate images, you can create an animation definition prior to beginning the calculation. This would allow you to view the individual image files as well as an animation of the pod as it falls. For additional information on creating animation definitions, see Animating the Solution in the Fluent User’s Guide.

• ANSYS Fluent: Scene and Animation Creation

2.Plot the center of gravity motion of the pod.

a. Read the pod-motion file into Microsoft Excel and plot flow time vs CG-orientation of the pod.

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Unsteady Setup

b.Plot flow time vs CG-angular orientation of the pod.

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