Specifying Boundary Conditions¶

Simulation set-up
Companion Files: baffledPipe.iges
Start the M-Star Pre-Processor via Windows Start Menu
Pre-Process ? Import Tank
Open baffledPipe.iges file
Accept default orientation
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.
Pre-Process -> Add Inlet or Outlet
Specify name: InletOutlet_1
Specify hydraulic diameter: 0.1 m
Choose “Pick”
Click on the lower z-plane of the lattice domain (see below: z-axis is pointing into the screen)
Select a point near the center of the opening.
Click Next in the Inlet Outet Wizard Window.
Observe a new purple arrow on your domain, indicating the existence of an opening.
Define Type: Inlet-Velocity
Specify an InletVelocity of 1 m/s
Click Finish

Fig. 1 Picking the inlet seed point¶
Pre-Process –> Add Inlet or Outlet
The Inlet Outlet Wizard window will open
Specify name: InletOutlet_2
Specify hydraulic diameter: 0.1 m
Choose to “Pick”
Click on the upper z-plane of the green lattice domain see orientation below: the z-axis is pointing away the screen)
Select near the center of the opening.
Click Next in the Inlet Outet Wizard Window.
Observe a new purple arrow on your domain, indicating the existence of an opening.
Define Type: Outlet-Pressure
Specify an OutletPressure of 101300 Pa
Click Finish

Fig. 2 Picking the outlet seed point¶
Tip
-Impellers and other moving objects may be added to any open system.
Select the Simulation Component
Specify Resolution on Reference Length: 30
Specify runtime: 60 s
Specify CheckPointInterval: 30 s
Specify data output: 0.05 s
Specify slice output: 0.1 s
Specify volume output: 1 s
Simulation Execution
Solve –> Run Solver
Choose an appropriate output location
Specify an appropriate number of cores
Model Post Processing
Browse to your output directory in Windows. Browse to your output directory in Windows
In Excel or another text editor, open the files /data/inletOutlet_0.dat and inletOutlet_1.dat
Plot the time-evolution of the velocity for both data sets on a single plot
Plot the time-evolution of the pressure for both data sets on a single plot
Start M-Star Post via Windows Start Menu
Browse to your output directory in Windows
Open the slices.txt in ParaView
Press the MStarPost button.
Press the 3D view tab
Press the green play button to animate the flow
Inspect the time-evolution of the velocity and pressure on the InletOutlet0 tab
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