Steady state simulation of flow over a throttle body

Aim- To study the flow characteristics of fluid passing over a throttle body in an elbow-shaped tube.

Governing equation- The equation used to solve this case is Navier-Stokes Unsteady equations. It comprises of 5 equations continuity, x-momentum, y-momentum, z-momentum, and energy equation. But for this case, the energy equation is not used since there is no gain or loss of energy and the temperature is constant throughout the simulation.

Objective- The objective of this problem is to simulate fluid flow over a throttle body in an elbow-tube when the throttle is at steady-state i.e zero angle. A base mesh is created with refinement near the throttle body and the pressure, velocity contours plot are made.

Description- First the geometry to be simulated is imported in Converge Studio and then the geometry is checked for any errors. The geometry is grouped into faces so that respective boundary conditions can be assigned and then the case setup is done. For this project, we will be running a steady-state simulation with a number of cycles 15,000 and end time 1s. It is a turbulent flow simulation hence RNG k-epsilon turbulence model is selected. The mesh size used is 1e-3m in all directions. In this project, the throttle body surface is refined because it helps in properly capturing the flow separation taking place and so a fixed embedding of scale 1 is given which means the cell size at the surface will be of 1mm and no. of layers 2.

Geometry-

From the above image you can see the position of the throttle body inside the elbow-tube.

Material-Air

Boundary Condition-Inlet: Pressure inflow of 1.5e+5 Pa

Outlet: Pressure outflow of 1e+5 Pa

Elbow wall and throttle body: Fixed wall

Initial Condition- Pressure:101325 Pa and temperature:300K

Mesh- Mesh size:1e-3m with fixed embedding scale=1 and no. of layers=2.

Results-

Cell count

The above plot shows the no. of cells generated with the mesh size 1mm and fixed embedding. It is about 48,500 cells.

Mass flow rate

In the above plot, bound_id_1 represents inlet, and bound_id_2 represents the outlet. So from the plot it is evident that the simulation as converged as the mass flow rate at the inlet and outlet is almost the same.

Static Pressure line plot

As the air flows towards the outlet the static pressure reduces at the inlet.

Velocity line plot

The velocity at the outlet is higher than the inlet because of the throttle body which reduces the area of the elbow at the center and hence accelerates the air.

Pressure contour

The pressure in the front part of the throttle is high because it is resisting the flowing fluid and hence the fluid gets stagnated at that point. The pressure at the upper and lower parts of the throttle is low because of the small gap.

Velocity contour

The velocity is high at the small gaps at the upper and lower parts of the throttle. The velocity at the outlet region is also high compared to inlet because the air accelerates due to a reduction in the elbow area by the throttle body.

Velocity vector

From this vector plot of velocity we can see how the flow occurs and its direction. And also verify whether the case is running properly or not.

Link to the velocity animation: https://youtu.be/P7bZ1Ds1oYI

Conclusion

From the above contour and line plots we can know how the flow takes place when a throttle body is in a static position.