Week 4.1: Project - Steady state simulation of flow over a throttle body

Aim: to setup and run the steady state simulation for flow over throttle body.

Geometry

• Import geometry
  
• extract the internal volume
  
• Close the openings
  
• Assign boundaries
  • Inlet
  • Outlet
  • Elbow wall
    
  • Throttle
    
• Check diagnostics
  
  Everything seems perfect as per diagnostic result.

Case setup

• Application type: Time based
  
  
• Materials
  gas simulation
  predefined mixture: Air
  
  
• Gas simulation
  Equation of state: Redich-Kwong
  Critical temperature: 133K
  Critical pressure: 3770000Pa
  
  
• Global transport properties
  turbulent Prandtl number: 0.9
  Turbulent Schmidt number: 0.8
  
  
• Reaction mechanism
  Available species `O_2` and `N_2`
  
  
• Run parameters
  Solver: steady state
  Simulation mode: Full hydrodynamic
  Gas flow solver: Compressible
  
  
  
  
  
  
  
  
  
  
• Simulation time parameter
  Start time par: 0 cycle
  end time: 15000 cycles
  Initial time step: 1e-9Sec
  Minimum time step: 1e-9sec
  maximum time step: 1sec
  
  
  
• Solver parameter
  Navier-stokes solver scheme: PISO
  Navier-stock solver type: pressure based
  
  
  
  
  
  
  
• Boundary
  • Inlet
    • Boundary type: INFLOW
    • Pressure: 150000Pa
    • Temperature: 300K
    • Species: `O_2` and `N_2`
      
      
  • Outlet
    
    • Boundary type: OUTFLOW
    • Pressure: 100000Pa
    • Temperature: 300K
    • Species: `O_2` and `N_2`
      
      
  • Elbow
    
    • Boundary type: wall
      
  • Throttle
    • Boundary type: wall
      
      
• Regions and initialization
  
  
• Turbulance modelling
  • Turbulance model: RNG K-`epsilon`
    
• Base grid
  • Grid size: 1mm
    
    
  • Fixed Embedding
    • Entity type: boundary
    • Boundary ID: Throttle
    • Mode: sequential
    • Scale:3
    • Embedded layers:2
    • Start time: 1 cycle
    • End time : 15000 cycle
      
      
• Output files
  

Result and outputs

mass flow rate

Average Mass flow rate at inlet is -0.045kg/sec and at outlet 0.045kg/sec. From above plot we can conclude that simulation reaches steady state approximately after 850 cycles.

Average velocity

average velocity at inlet is -125m/sec and at outlet 175m/sec. from the above plot we can conclude that simulation has attain steady state after 800 cycles.

Total pressure

Total average pressure at inlet is 150000 Pa and at outlet 121000 Pa. From the above plot we can conclude that simulation has attained steady state after 700 cycles.

Total cells

Mesh

Velocity contour

Pressure contour

Pressure contour video link

https://youtu.be/oaCvW0v2q_0

Velocity contour video link

https://youtu.be/zC35093MCck

Conclusion

• Velocity and pressure is higher at throttle from inlet side but lower at other side of the throttle because of flow separation is taking place which is causing wake region.
• From The mass flow rate plot, we can observe that mass flow rate at inlet is same as outlet so we can say that flow is steady state.