Specifying Boundary Conditions

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Simulation set-up

Companion Files: baffledPipe.iges

  1. Start the M-Star Pre-Processor via Windows Start Menu

  2. Pre-Process ? Import Tank

    1. Open baffledPipe.iges file

    2. Accept default orientation

    3. Accept the default origin location

  • The “up” direction points anti-parallel to the direction of gravitational acceleration

  • The “Origin” is a point inside the tank that is to be mapped to the center of the model viewer.

  1. Pre-Process -> Add Inlet or Outlet

    1. Specify name: InletOutlet_1

    2. Specify hydraulic diameter: 0.1 m

    3. Choose “Pick”

    4. Click on the lower z-plane of the lattice domain (see below: z-axis is pointing into the screen)

    5. Select a point near the center of the opening.

    6. Click Next in the Inlet Outet Wizard Window.

    7. Observe a new purple arrow on your domain, indicating the existence of an opening.

    8. Define Type: Inlet-Velocity

    9. Specify an InletVelocity of 1 m/s

    10. Click Finish

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Picking the inlet seed point

  1. Pre-Process –> Add Inlet or Outlet

    1. The Inlet Outlet Wizard window will open

    2. Specify name: InletOutlet_2

    3. Specify hydraulic diameter: 0.1 m

    4. Choose to “Pick”

    5. Click on the upper z-plane of the green lattice domain see orientation below: the z-axis is pointing away the screen)

    6. Select near the center of the opening.

    7. Click Next in the Inlet Outet Wizard Window.

    8. Observe a new purple arrow on your domain, indicating the existence of an opening.

    9. Define Type: Outlet-Pressure

    10. Specify an OutletPressure of 101300 Pa

    11. Click Finish

Picking the outlet seed point

Picking the outlet seed point

Tip

-Impellers and other moving objects may be added to any open system.

  1. Select the Simulation Component

    1. Specify Resolution on Reference Length: 30

    2. Specify runtime: 60 s

    3. Specify CheckPointInterval: 30 s

    4. Specify data output: 0.05 s

    5. Specify slice output: 0.1 s

    6. Specify volume output: 1 s

Simulation Execution

  1. Solve –> Run Solver

    1. Choose an appropriate output location

    2. Specify an appropriate number of cores

Model Post Processing

  1. Browse to your output directory in Windows. Browse to your output directory in Windows

  2. In Excel or another text editor, open the files /data/inletOutlet_0.dat and inletOutlet_1.dat

    1. Plot the time-evolution of the velocity for both data sets on a single plot

    2. Plot the time-evolution of the pressure for both data sets on a single plot

  1. Start M-Star Post via Windows Start Menu

  2. Browse to your output directory in Windows

  3. Open the slices.txt in ParaView

  4. Press the MStarPost button.

  5. Press the 3D view tab

  6. Press the green play button to animate the flow

  7. Inspect the time-evolution of the velocity and pressure on the InletOutlet0 tab

  8. Inspect the time-evolution of the velocity and pressure on the InletOutlet1 tab

Note

  • The pressure at the inlet should converge to a steady state value

  • The steady-state inlet and outlet velocities should be consistent for this system.

  • If the inlet/exit flow rates are disparate, consider decreasing the Courant number to 0.015