Project Transient simulation of flow over a throttle body using Converge CFD

Procedures:

1. Preparing a channel to stimulate simple flow using Converge CFD.
2. Setting up the boundary conditions & simulation setup.
3. Base Grid meshing is to be
   • dx = dy = dz = 2e-3m.
4. Using CYGWIN to execute the CFD solver.
5. Use Converge CFD to post convert the output files to ParaView format.
6. Paraview to Post Processing the results.

Inputs:

• Inlet Pressure = 150000 Pa
• Outlet Pressure = 100000 Pa
• Channel Length L = 0.2 m
• Flow type = Turbulent
• Fluid Medium = Air (Nitrogen, Oxygen)
• Throttle Position = 0° to 25° (for 0 to 2 ms)
• Throttle Position = 25° (for 2 to 4 ms)
• Throttle Position = 25° to 0° (for 4 to 8 ms)

Calculation:

Average Flow rate of air at the inlet is 191 m/s. (Refer from Steady-State Flow Plots).

So total time taken for the air to flow across the pipe can be calculated by,

t=L/u

where t = Total Time (sec)

L = Length of pipe (m)

u = Average velocity of air in a steady condition (m/s)

So, t = 0.2 / 191

t = 0.001047 sec.

So the minimum time required for setting up for completing this simulation will be 0.001047 sec.

But in this simulation, the total time (End-Time) is set to 0.004 sec. This was done to capture the flow of air which will attain steady state as the throttle valve goes stationary at the end of the simulation.

Pre-Processing & Setting up Boundry Conditions:

Processing for Case-Steady Flow:

Meshing:

Velocity Contour:

The above figures show the velocity contour at throttle opened condition (0°).

Above figure shows the velocity contour at throttle rotated condition (25°).

Pressure Contour:

The above figure show the pressure contour at throttle opened condition (0°).

Above figure shows the pressure contour at throttle rotated condition (25°).

Post_Processing for Case-Steady Flow:

Average Velocity Plot:

Mass Flow Rate plot:

Pressure Plot:

Plot for Total Cells Count per Processor :

Verdict:

• We can see from the results that when the mesh is finer the contours profile looks detailed at the throttle position as it was created with 2 embedded layers & scaling to 3.
• From the velocity & flow rate plots, we can see that the inlet profile is inversely proportional to the outlet profile. This shows us that the flow is conservative as masses were conserved during the flow.
• At first, the flow is unsteady as the throttle rotates from 0° to 25° for 1st quarter time. When throttle gets back to its original position (0°), we can see that the flow tries to attain steady state which can be confirmed from the above plots.