Building the Mesh

This section describes the step-by-step procedure for preparing the mesh for the helical gear pump. The Rotor Template Mesher is used for creating the gear mesh and the General Mesher is used for the inlets and the outlets.

Inlet1 and Inlet2

Select General Mesher in the Mesh Panel.
Enter inlet for Mesh Name in the Properties Panel.
Select all CAD Surfaces inlet1 and inlet2 in the Geometric Entities Panel and click Add Surfaces icon for CAD Surfaces in the Properties Panel.
Enter Maximum Cell Size as 0.01, Minimum Cell Size as 0.0007 and Cell Size on Surfaces as 0.005.
Click Create Mesh. A new mesh inlet is created under Built Meshes in the Geometric Entities Panel.
The meshed volumes inlet1 and inlet2 are generated under Volumes.

Figure 6.916 - Inlet1 and Inlet2 mesh settings

Outlet1 and Outlet2

Select General Mesher in the Mesh Panel.
Enter outlet for Mesh Name in the Properties Panel.
Select all CAD Surfaces outlet1 and outlet2 in the Geometric Entities Panel and click Add Surfaces icon for CAD Surfaces in the Properties Panel.
Enter Maximum Cell Size as 0.01, Minimum Cell Size as 0.0007 and Cell Size on Surfaces as 0.005.
Click Create Mesh. A new mesh outlet is created under Built Meshes in the Geometric Entities Panel.
The meshed volumes outlet1 and outlet2 are generated under Volumes.

Figure 6.917 - Outlet1 and Outlet2 mesh settings

Gear

Select Rotor Template Mesher in the Mesh Panel.
Select General Gear for Rotor Type drop-down list in the Properties Panel.
Enter 0, 0, 1 for Rotate Axis Direction.

Gear1 Parameters

Select External Gear under Add a Gear drop-down list.
Enter 0, 0, 0 m for Gear Center in Gear 1 list.
Select CAD Surfaces gear1 in the Geometric Entities Panel, click Add Surfaces icon for Gear Surfaces in the Properties Panel.
Select By CAD Input under Outer Surface Type.
Similarly, select CAD Surfaces outlet2_mgi_gear1 in the Geometric Entities Panel and click Add Surfaces for Gear Outer Surface.
Enter 17 for Num. of Teeth.
Select Yes for Helical Gear drop down list.
Enter 20 deg for Total Rotation angle.

Gear2 Parameters

Select External Gear under Add a Gear drop-down list.
Enter 0.022449, -0.039, 0 m for Gear Center in Gear 2 list.
Select CAD Surfaces gear2 in the Geometric Entities Panel, click Add Surfaces icon for Gear Surfaces in the Properties Panel.
Select By CAD Input under Outer Surface Type.
Similarly, select CAD Surfaces inlet1_mgi_gear2 in the Geometric Entities Panel and click Add Surfaces for Gear Outer Surface.
Enter 17 for Num. of Teeth.
Select Yes for Helical Gear drop down list.
Enter -20 deg for Total Rotation angle.

Gear3 Parameters

Select External Gear under Add a Gear drop-down list.
Enter 0.053043, -0.072, 0 m for Gear Center in Gear 3 list.
Select CAD Surfaces gear3 in the Geometric Entities Panel, click Add Surfaces icon for Gear Surfaces in the Properties Panel.
Select By CAD Input under Outer Surface Type.
Similarly, select CAD Surfaces inlet1_mgi_gear3 in the Geometric Entities Panel and click Add Surfaces for Gear Outer Surface.
Enter 17 for Num. of Teeth.
Select Yes for Helical Gear drop down list.
Enter 20 deg for Total Rotation angle.
Click Build General Gear Mesh. The new mesh general gear is created underBuilt Meshes in the Geometric Entities Panel.
The names of meshed volumes obtained are generalgear_gear_1, generalgear_gear_2 and generalgear_gear_3 are generated under Volumes.

Figure 6.918 - Gear1 mesh settings

Figure 6.919 - Gear2 mesh settings

Figure 6.920 - Gear3 mesh settings

Note: In the Rotor Template Mesher, the Outer Surface Type has three options to model the rotor chamber. First option is By CAD Input, this requires CAD Surfaces as a input, second option is By Radius, this requires input of radius, and third option is By Tip Gap, this requires Tip Gap Size in m.

The mesh created for the fluid domain is shown below.

Figure 6.921 - Inlet and Outlet mesh

Figure 6.922 - Gear mesh

Note: The mesh can be edited/replaced by selecting required volume under Built Meshes and modify the mesh parameters in the Properties Panel. Click Create Mesh to reflect the changes.

Default MGI Creation in Template Mesher

The Rotor Template Mesher creates interfaces between the gears automatically.
Two Mismatched Grid Interfaces (MGIs), MGI01 and MGI02 are created interfacing the generalgear_gear1, generalgear_gear2 and generalgear_gear3 under Volumes.
These MGIs are created using some default projection tolerance. Do not change any of these settings especially for default MGIs.

Create interfaces

In this section, the Mismatched Grid Interfaces (MGIs) are generated between boundaries.

The steps to create the MGIs are shown below:

Geometric Entities Panel > Volumes > Boundaries, select Boundaries as shown in Table 6.45.
Click Connect Selected Boundaries via MGI icon to create the MGI entities as shown in Figure 6.923.

A group display of entities can be viewed using the Group Entities by Volumes/Types icon in Geometric Entities Panel toolbar.

Connecting interfaces	Boundaries	Entity
generalgear_gear1, inlet2 and outlet2	generalgear_gear_1_outside, inlet2_mgi_gear1 and outlet2_mgi_gear1	MGI03
generalgear_gear1, generalgear_gear2, generalgear_gear3, inlet1, inlet2 and outlet2	generalgear_gear_1_mgi_bot, generalgear_gear_2_mgi_bot, generalgear_gear_3_mgi_bot, inlet1_mgi_gear23, inlet2_mgi_gear12 and outlet2_mgi_gear12	MGI04
generalgear_gear1, generalgear_gear2, outlet1 and outlet2	generalgear_gear_1_mgi_top, generalgear_gear_2_mgi_top, outlet1_mgi_gear1 and outlet2_mgi_outlet1	MGI05
generalgear_gear2, generalgear_gear3 and outlet1	generalgear_gear_2_mgi_top, generalgear_gear_3_mgi_top and outlet1_mgi_gear3	MGI06
generalgear_gear2, inlet1 and outlet2	generalgear_gear_2_outside, inlet1_mgi_gear2 and outlet2_mgi_gear2	MGI07
generalgear_gear3 and inlet1	generalgear_gear_3_outside and inlet1_mgi_gear3	MGI08

Table 6.45 - Creating interfaces

The new entities are created under MGI in Volumes (refer, Figure 6.924).

Figure 6.923 - Connecting gear1, inlet2 and outlet2

Figure 6.924 - Created interfaces

Note: If MGIs are created by connecting the wrong boundaries, delete the created MGIs by clicking on Delete Selected Geometric Entity icon and then recreate the MGIs.