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Problem Specification
1. Create Geometry in GAMBIT
2. Mesh Geometry in GAMBIT
3. Specify Boundary Types in GAMBIT
4. Set Up Problem in FLUENT
5. Solve!
6. Analyze Results
7. Refine Mesh
Problem 1
Problem 2

Step 4: Set Up Problem in FLUENT

If you have skipped the previous mesh generation steps 1-3, you can download the mesh by right-clicking on this link. Save the file as nozzle.msh in your working directory. You can then proceed with the flow solution steps below.

Launch FLUENT

Start > Programs > Fluent Inc > FLUENT 6.3.26 > FLUENT 6.3.26

Select 2ddp from the list of options and click Run.

Import File

Main Menu > File > Read > Case...

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The following should appear in the FLUENT window:

Check that the displayed information is consistent with our expectations of the nozzle grid.

Check and Display Grid

First, we check the grid to make sure that there are no errors.

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Look at specific parts of the grid by choosing each boundary (centerline, inlet, etc) listed under Surfaces in the Grid Display menu. Click to select and click again to deselect a specific boundary. Click Display after you have selected your boundaries.

Define Solver Properties

Define > Models > Solver...

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Under Space, choose Axisymmetric. This will solve the axisymmetric form of the governing equations.

Click OK.

Define > Models > Viscous

Select Inviscid under Model.

Click OK. This means the solver will neglect the viscous terms in the governing equations.

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Make sure there is a check box next to Energy Equation and click OK.

Define > Materials

Select air under Fluid materials. Under Properties, choose Ideal Gas next to Density. You should see the window expand. This means FLUENT uses the ideal gas equation of state to relate density to the static pressure and temperature.

Click Change/Create. Close the window.

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We'll work in terms of absolute rather than gauge pressures in this example. So set Operating Pressure in the Pressure box to 0.

Click OK.

It is important that you set the operating pressure correctly in compressible flow calculations since FLUENT uses it to compute absolute pressure to use in the ideal gas law.

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Set the total pressure (noted as Gauge Total Pressure in FLUENT) at the inlet to 101,325 Pa as specified in the problem statement. For a subsonic inlet, Supersonic/Initial Gauge Pressure is the initial guess value for the static pressure. This initial guess value can be calculated from the 1D analysis since we know the area ratio at the inlet. This value is 99,348 Pa. Note that this value will be updated by the code. After you have entered the values, click OK to close the window.

Check that under the Thermal tab, the Total Temperature is 300 K. Click OK.

Using the same steps as above, pick pressure-outlet as the boundary condition for the outlet surface. Then, when the Pressure Outlet window comes up, set the pressure to 3738.9 as specified in the problem statement. Click OK.

Set the centerline zone to axis boundary type.

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