Week 10: Proportional Valve simulation

                                                         Proportional Valve Simulation

• Aim:

 SImulate a steady state flow of a proportional value with different pressure ratios and capture the pressure force acting on the spindle and tabulate the results while using it with and without AMR. Also perform a FSI transient simulation where we capture the spindle move from its position due to fluid pressure.

- Objective:

you need to set up and run 6 cases for proportional valve as shown below,

• 3 cases without Adaptive Mesh Refinement (AMR) 
  • Lift = 3 mm
  • Lift = 4 mm
  • Lift = 5 mm
• 3 cases with Adaptive Mesh Refinement (AMR)
  • Lift = 3 mm
  • Lift = 4 mm
  • Lift = 5 mm
• Run the case with FSI model and show the results.

• Theory:

1. Proportional Valve:

A proportional valve provides a change in output pressure or flow in the same ratio as the change in the input, for example if the input doubles then the output will also double. Proportional valves can be interconnected with the output from one being used as the input to another. 

Increasing the current increases the strength of the magnetic field and, in turn, the force of attraction (or repulsion) on the magnetic material. A proportional valve has a geometry to ensure a constant field strength, at a given current, over the stroke of the magnet.

• Procedure:

1. Upload the stl file onto converge studio, remove the thicknes by using the delete option under repair.

2. Close the open edges by creating inlet and outlet surfaces to close the geometry.

3. Asssign boundary flagging for each boundary appropriately.

4. Assign throtlle boundary flagging by hiding the outer wall partially and then assign boundary to throttle by choosing surface select.

- Case setup:

1. Application type: time based

2. Materials:

a. Gas simulation: air 

b. Global transport properties: Deafult

c. Species: O2 and N2

3. Simulation parameters:

a. Run parameters:

   steady state solver, full hydrodynamic, compressible

b. Simulation time parameters: 

- End time- 15000 cycles

- Time step- 1e-6

   - min time step- 1e-6

   - max time step- 1 

   - Convection CFL number- 0.5

c. Solver Parameters-

- Solver type- density based solver

4. Boundary Conditions-

a. Inlet- Inflow

- Total pressure- 30bar

- Initial temp- 300K

- Species boundary condition- add air

b. Outlet- Outflow

- Pressure- 1.1 bar

- Backflow - temp= 300k

                - add air

c. Spindle - Walls

Law of the wall- The contact region between wall surface and fluid region tends to create high friction and create a 0 velocity of fluid flow, and due to viscosity of fluid, the fluid layers tend to undergo shear stress and have high pressure and overlap on eachother which eventually forms a fully developed region where velocity is max and constant and having low pressure.

d. Casing: Wall- Law of the wall

5. Initial Conditions and Events:-

- Regions and Initialization:

Pressure- 101325 Pa

Temperature: 300K

Add- air 

6. Physical Models:-

- RNG k-epsilon

7. Grid Control:-

a. Base Grid:  

   dx = 1e-4m, dy = 1e-4m, dz = 1e-4m

b. AMR:

- Presure based.

SGS- 3

8. Post-Processing:-

- Post Variable Selection:

Select the parameters needed to be post processed.

- Output files:

We need to set a time interval for the files to be saved during each set of iterations. It is best suited to have a min of 100 saved files for every simulation. Therefore we need to calculate the time interval for writing the output files based on our end time given in run parameters.

Restart files help in restoring the files if there is a sudden power cut/ crash which is not helpful or might end up loosing the entire data, therefore the restart files helps in resuming the simulation form the point we lost contact. Restart files time interval can be same as the writing files interval which is safe and healthy.

In this case- since the end time is 1.6, we can have a time interval of 0.016 and the total files created will be 100.

• Results:

 - Case 1: Running for the 3 cases having different spindle positions with and without AMR.

1. Velocity:

a. Without AMR:

b. With AMR:

2. Mass flow rate:

a. Without AMR:

b. With AMR:

3. Pressure:

a. Without AMR:

b. With AMR:

4. Pressure force:

a. Without AMR:

b. With AMR:

- Inference with and without AMR: When we compare the result of the mass flow rate, velocity, pressure force and total pressure with and without AMR, though we have the same value this is because of the SGS value which we used in AMR but with AMR we getting an actual physics flow because as we know the more refined the mesh the more accurate results we get.

- Case 2: Transient simulation performing FSI model without AMR.

- Geometry: Same setup as the previous case.

- Case setup:

1. Application type: time based

2. Materials:

a. Gas simulation: air 

b. Global transport properties: Deafult

c. Species: O2 and N2

3. Simulation parameters:

a. Run parameters:

   Transient solver, full hydrodynamic, compressible

b. Simulation time parameters: 

- End time- 1.6 sec

- Time step- 1e-6

   - min time step- 1e-6

   - max time step- 1 

   - Convection CFL number- 0.5

c. Solver Parameters-

- Solver type- density based solver

d. Body forces: z-direction:-9.81m/s^2

4. Boundary Conditions-

a. Inlet- Inflow

- Total pressure- Varrying pressure (UDF)

- Intake Pressure profile:

- Initial temp- 300K

- Species boundary condition- add air

b. Outlet- Outflow

- Pressure- 1.1 bar

- Backflow - temp= 300k

                - add air

c. Spindle - Wall- FSI object

d. Casing: Wall- Law of the wall 

5. Initial Conditions and Events:-

- Regions and Initialization:

Pressure- 101325 Pa

Temperature: 300K

Add- air 

6. Physical Models:-

- RNG k-epsilon

- FSI Model:

Boundaries: Valve Spindle

Parameters: 

a. Start time: -9e-5

b. Mass flag= 3.15kg

c. Forces:

- constant force: -7126N in z-axis

- DOF: 1 DOF Translation.

        - Min Displacement: default

        - Max Displacement: 0.1m 

7. Grid Control:-

a. Base Grid:  

   dx = 1e-4m, dy = 1e-4m, dz = 1e-4m

b. AMR:

- Presure based.

SGS- 3

8. Post-Processing:-

- Post Variable Selection:

Select the parameters needed to be post processed.

- Output files:

We need to set a time interval for the files to be saved during each set of iterations. It is best suited to have a min of 100 saved files for every simulation. Therefore we need to calculate the time interval for writing the output files based on our end time given in run parameters.

Restart files help in restoring the files if there is a sudden power cut/ crash which is not helpful or might end up loosing the entire data, therefore the restart files helps in resuming the simulation form the point we lost contact. Restart files time interval can be same as the writing files interval which is safe and healthy.

In this case- since the end time is 1.6, we can have a time interval of 0.015 and the total files created will be 100.

• Results:

- Position plot:

- Force acting on spindle valve:

- Velocity contour:

• Conclusions:

- Steady state and transient state simulation was performed successfully.

- It can be observed from the graph that the spindle moves in a to and fro motion due to the fluid pressure and the downward force acting due to weight and gravity.

- After the inlet pressure variable comnes down to 0, there is a minimum flow which is entering the valve, this is due to geometrical error and can be done using events. which is not under this scope.