Defining Physics and Conditions

The physics and conditions are specified as follows.

Click Select Modules in the Model Panel. The Physical Model Selection dialog box opens.
Spool Valve is automatically added to the Model Panel by the Valve Template Mesher.
Select Cavitation and Translation (1 DOF) under Available Modules list and click Add.
Click Close to close the Physical Model Selection dialog box.

Figure 6.541 - Adding modules

Select Spool Valve in the Model Panel.
Select Translation (1 DOF) for Dynamics in the Model Tab of Properties Panel, to link the motion of the Spool Valve to the Translation (1 DOF) module.
Set Minimum Gap Size as 0.0001 and Maximum Displacement as 0.01.
Select No for the Closure Model drop-down list .

Figure 6.542 - Spool valve operating parameters

´	Note: Closure Model determines whether the flow is fully blocked at the Minimum Gap Size. The Minimum Gap Size specified in the Valve Template Mesheris larger than that for the actual model, so that the domain has a reasonable cell count.

Select Translation (1 DOF) in the Model Panel.
Select Advanced Mode for the Setup Options drop-down list in the Model Tab of Properties Panel.
Enter the parameters for Time Definition as follows.
- Number of Cycles: 5
- Number of Time Steps per Cycle: 400
- Motion Frequency (Hz): 50 1/s
Select Force Balance in the Motion Type drop-down list.
Enter the parameters for Motion Type as follows.
- Body Mass: 0.01 kg
- Spring Constant: 6200 N/m
- Spring Preload Force: 15 N
Enter Movement Direction as -1,0,0

Note: The Number of Time Steps per Cycle is an important parameter and must be large enough to achieve a smooth solution.

Figure 6.543 - Translation (1 DOF) operating parameters

The boundary conditions for the valve are specified as follows:

Select the entities under Boundaries from the Geometric Entities Panel, as shown in Table 6.28.
In the Model Tab of Properties Panel, verify the boundary type for the Spool Valve drop-down list as shown in Table 6.28. The boundary conditions for the valve1 volume generated using the Valve Template Mesher are automatically set by the template. For valve2 boundaries, specify the respective circumferential boundary type as shown in Table 6.28.

Boundaries	Circumferential Boundary Type
valve1_valve, valve2_valve, valve2_mgi_valve1	Valve
valve2_cylinder, valve1_cylinder_i, valve1_cylinder_o	Cylinder
valve2_ends, valve1_ends1, valve1_ends2	Valve End

Table 6.28 - Boundary type

Select port_inlet from the Boundaries list in the Geometric Entities Panel.
Select Inlet from the Spool Valve drop-down list in the Model Tab of Properties Panel.
Click Edit Expressions icon in Inlet Pressure to open the Expression Editor dialog box .
Enter the following for Global Expressions (see, Figure 6.544).
p0 = 6e5
dp = 2e5
freq = 50
high_p = dp*sin(2*pi*freq*time)+p0
Click OK and enter high_p for the Inlet Pressure.

Figure 6.544 - Inlet conditions

Select port_outlet from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Outlet from the Spool Valve drop-down list in the Model Tab of Properties Panel.
Enter Outlet Pressure as 101325 Pa.

Figure 6.545 - Outlet conditions

Select Volumes in the Geometric Entities Panel.
Select Model Tab in the Properties Panel.
Enter the parameters for Property list as follows.
- Material: Oil
- Dynamic Viscosity: 0.007 Pa-s
- Density: 800 kg/m³
- Liquid Bulk Modulus(B0): 1.5e+09 Pa
- Liquid Reference Pressure: 101325 Pa
- Saturation Pressure: 400 Pa
Enter the parameters for Operating Conditions as follows:
- Gas Mass Fraction: 9e-05
- Operating Temperature: 300 K
- Starting Pressure: 101325 Pa

Figure 6.546 - Fluid properties