Steady state simulation of flow over a throttle body

In this challenge, flow over a throttle body is simulated under steady-state conditions using converge 3.0. Two cases are investigated, at the first throttle body is completely open and in the second case, the throttle body is partially open (rotated by 25 degrees).

Physical Setup:

General	Steady State Pressure Based
Model	RNG K-`ε`
Materials	Air (77% N2, 23% O2)
Monitors	Average Velocity at Outlet
Boundary Conditions	Inlet (1.5e5 Pa) and Outlet (1e5) Elbow-Wall and Throttle (Walls)

Flow of Project in Converge:

1. Provided geometry is dropped in the Converge workspace.
2. Boundaries are named using appropriate names.
3. Normal directions are checked to be in line with the geometry and flow.
4. Diagnosis is performed to check any discrepancies in geometry.
5. Then appropriate species are selected for the fluid.
6. Simulation Parameters along with the steady-state monitor are set.
7. Boundary conditions are set to the appropriate regions and their corresponding values.
8. The base grid of the considered step size is inserted along with respective directions and fixed embedding is inserted accordingly.
9. Variables for post-processing and time intervals for writing the output and restart files are set and selected.
10. All the input files are stored at the desired location.
11. All the stored input files are executed using the command editor. These input files are executed by Converge Solver in the background.
12. Then the executed files generate the output folder in which data files after every selected cycle intervals are stored which are post-processed for the graphical results.

Mesh Generation:

A base grid of 2e-3m with fixed embedding near the throttle walls for the scale of 3 and 2 embedded layers is used for all the cases to create the fine body fitted contours over the throttle.

Case1:

Here Throttle valve is completely open.

Geometry:

Mesh:

Total Cells:

Velocity Contour:

Pressure Contour:

Stream Lines:

Velocity Vectors:

Pressure at Inlet and Outlet:

Mass Flow Rate:

Velocity:

From the above figures, it is clear that the results are converged. The mass flow rate through the inlet is the same as the mass flow rate through the outlet. The pressure is higher at the obstructing face of the throttle and less at the trailing edge and there is the scope of the recirculating zone being created at the trailing edge owing to reduced pressure. Through the edges of the throttle along the flow direction, the velocity is higher at the zone where the pressure is less which is evident from the contours of pressure and velocity.

Case2:

As we are investigating the steady-state case, the throttle cannot be rotated over the cycles. To rotate the throttle during the simulation, a transient study has to be performed. However, we can fix the throttle geometry before we begin the steady-state simulation. In this case, the throttle is rotated over 25 degrees.

Geometry:

Unlike the previous case, throttle valve is rotated over 25 degrees w.r.t. its axis.

Mesh:

The throttle is visible as a rectangle, as we cut through the z-normal.

Total Cells:

Pressure Contour:

Pressure is higher at the upstream and lowers at the downstream. Moreover, as we are viewing through the z-normal, we observe the similar pattern within the upstream and downstream, respectively.

Velocity Contour:

Velocity is higher near the gap of throttle where the pressure is lower which is evident from pressure contour.

Stream Lines:

Both the leading and trailing surfaces of throttle are shown below. The pressure is higher at the leading surface as it is obstructing the flow and lower at the trailing surface.

Velocity Vector:

Pressure at Inlet and Outlet:

Mass Flow Rate:

Velocity:

From the above figures, it is clear that the results are converged. The mass flow rate through the inlet is the same as the mass flow rate through the outlet. The pressure is higher at the obstructing face of the throttle and less at the trailing edge and there is the scope of the recirculating zone being created at the trailing edge owing to reduced pressure. Through the edges of the throttle along the flow direction, the velocity is higher at the zone where the pressure is less which is evident from the contours of pressure and velocity.