Week 4.1: Project Steady state simulation of flow over a throttle body
Aim
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Post process the results and show pressure and velocity contours.
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Show the mesh (i.e surface with edges)
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Show the plots for pressure, velocity, mass flow rate and total cell count.
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Create an animation in which it throttle movement should be visible.
Introduction
- A throttle is the mechanism by which fluid flow is managed by constriction or obstruction.
An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term 'throttle' has come to refer, informally, to any mechanism by which the power or speed of an engine is regulated, such as a car's accelerator pedal. What is often termed a throttle (in an aviation context) is also called a thrust lever, particularly for jet engine powered aircraft. For a steam locomotive, the valve which controls the steam is known as the regulator.
Geometry
Throttle valve
Setup
- Time based simulation is set
- Material is set to air contains 0.77 of nitrogen and 0.23 of oxygen also species involvemnt is also enabled
- species is enabled and reaction mechanism is disabled
- In run parameters enregy involvement is disabled as we dont want temperature analysis
- Steady state monitor is turned on
- Under steady state monitor mass flow rate is selected to check the convergency of the solution with sample size is set to 1000 and monitor start delay to 8000. Minimum cycles to be executed is set to 8000
- Under simulation time parameter cycles to be executed is set from 0 to 15000,initial and minimum time step is set to 1e-9 whereas the maximum time step is to 1. The maximum CFL for convection is set to 1
- Under solver paramteres,under steady state solver the maximum CFL limit of convection is set to a value less than 1 which is 0.8 inorder to avoid the chances of divergance
- A new region containing air is created in 'region and initialisation' and the initial pressure is set to 1e-5 pa
- Boundary conditions are set and shown the screen shots
- RANS model is selected under turbulance model
- In grid control fixed embedding is enabled and under fixed embedding scale is set to 3 and the number of layers is set to 2
- Finally normals were checked an ensured that they were pointing inside of the geometry
Running the simulation
- Inorder to run the simulation the input files are exported to a specified folder
- Then 'mpiexec.exe' file is copied from the convergent science directory -> converge -> 3.0.16 -> bin -> mpi -> intel64 -> bin
- Also another file named 'converge.exe' is also copied and pasted to the same folder . This file is availible in the Convergent_Science -> CONVERGE -> 3.0.16 -> bin -> msmpi folder
- CYGWIN is run as administrator and navigated to the folder containing the input files
- Then the following command is typed to start the calculation 'mpiexec.exe -n 4 converge.exe restricted' to run with 4 processors
Post processing
- After running the simulation the output files are availble in the same folder
- We can check whether the simulation has converged or not using the convergant studio line plotting, mass flow rate , velocity , pressure at inlet and outlet are obtained here
- For extracting the contour we need 3D files in output folder to be opened through paraview
- So inorder to make the files readable in paraview they are converted to either vtk file or case file. The conversion is done in Post processing in Convergant studio
Outputs
Mesh
Plots
Mass flow rate at Inlet (ID 1) and Outlet (ID 2)
Average Velocity at Inlet and Outlet
Total Pressure at Inlet and Outlet
- Using the above plots we can ensure that the solution is converged
- Also the values are obtained
Contours
- Velocity contours
- Pressure Contour
Vector plot
Conclusion
- A steady state simulation of flow over a throttle body is done
- Obtained necessary contours and plots
- Visualised behaviour of flow over a throttle body using vectors
- A screen shot of the mesh was also obtained