Setting Up Mesh Operations for Gerotor Volume

When remeshing happens, the mesh pipeline ensures that the pump is positioned in a correct position. Besides, due to the small gaps you apply Directed Mesh to reduce the cell count in the axial direction of the pump.

You define two motion Transform operations, one Substract operation and one Directed Mesh operation for the gerotor volume.

First, you define two rotational motions for the inner and outer rotors. Their rotational speeds match the number of teeth—the outer rotor with 12 teeth rotates a bit slower than the inner rotor with 11 teeth.

To define the rotation for the inner rotor, right-click the Tools > Motions node and select New > Rotation.

Rename the Rotation node to Rotation_inner and set its properties as follows:


Node	Property	Setting
Rotation_inner	Rotation Specification	Rotation Rate
Rotation Rate	Rotation Rate	1090.90909 rpm
Rotation Axis	Direction	[0.0,0.0,1.0]
Rotation Axis	Origin	[0.0,0.0,0.0] m

To define the rotation for the outer rotor, right-click the Tools > Motions node and select New > Rotation.

Rename the Rotation node to Rotation_outer and set its properties as follows:


Node	Property	Setting
Rotation_outer	Rotation Specification	Rotation Rate
Rotation Rate	Rotation Rate	1000 rpm
Rotation Axis	Direction	[0.0,0.0,1.0]
Rotation Axis	Origin	[-0.0031,0.0,0.0] m

You define two motion transforms for the inner and outer rotors that follow their respective rotations. Therefore, the rotor geometry is always positioned correctly whenever a remesh takes place.
1. Right-click the Geometry > Operations node and select New > Surface Preparation > Transform.
2. In the Create Transform Operation dialog, select the part Inner and click OK.
3. Rename the Transform node to Transform_inner.
4. Right-click the Transform_inner > Transforms node and select New > Motion.
5. Select the Transform_inner > Transforms > Motion node and set Motion to Rotation_inner.
6. Repeat the steps above to define a Transform_outer operation with the part Outer.
7. Right-click the Transform_outer > Transforms node and select New > Motion.
8. Select the Transform_outer > Transforms > Motion node and set Motion to Rotation_outer.

To generate the wetted volume, you subtract the inner rotor volume from the outer rotor. As later you apply a Boundary Plane constraint for the morpher, you extend the Part Surface in the direction normal to the Boundary Plane. Extending the surface ensures that the surface and the plane intersect correctly.

To extrude the Inner part in both directions:
1. Right-click the Parts > Inner node and select Repair Surface.
2. In the Surface Repair Options, keep default settings and click OK.
3. Double-click to select all the Faces to be extruded in the +y direction as follows:
4. After selecting the faces, in the Global tools, select Transform selected entities and set Transform Mode to Translate.
5. Set Translation Vector to [0.0, 0.0, 0.005] m and click Transform Selection.
6. Repeat the steps with the opposite faces and Translation Vector [0.0, 0.0, -0.005]m.
To generate the wetted volume, you define a Subtract operation between outer and inner rotors:
1. Right-click the Geometry > Operations node and select New > Boolean > Subtract.
2. In the Create Subtract Operation dialog, select the parts Inner, Outer as Input Parts and Outer as Target Parts and click OK.
3. Select the Operations > Subtract node and activate the expert option Perform CAD Boolean.
4. Select the Subtract > Tessellation Options node and, in the Tessellation Options dialog,set Tessellation Density as Very Fine.
  A very fine tessellation helps to obtain a better surface representation of the gear walls.
5. To rename the output part Subtract, select the Parts > Subtract node and rename it to PumpFluid.

To mesh the part PumpFluid, you define a directed mesh operation with prism layers. Using the trimmed cell or polyhedral meshers would generate large cell counts due to the small gaps between rotors. With a directed mesh you can generate stretched cells in the gaps that reduce cell count.

Right-click the Geometry > Operations node and select New > Mesh > Directed Mesh.
In the Create Directed Mesh Option dialog, select the part PumpFluid and click OK.
Select the Directed Mesh > Source Surfaces node and set the part PumpFluid.Outer.top as Source Surfaces.
Select the Directed Mesh > Target Surfaces node and set the part PumpFluid.Outer.bottom as Target Surfaces.
To add a source mesh used in volume generate, right-click the Directed Mesh > Source Meshes node and select Automated Source Mesh.
In the Part Collection For This Source Mesh dialog, select the part PumpFluid and enable the following meshers and click Ok.
- Quadrilaterial Mesher
- Prism Layer Mesher

Select the Auto Mesh > Default Controls node and set the following properties:


Node	Property	Setting
Base Size	Base Size	0.001 m
Minimum Surface Size	Percentage of Base	0.5
Prism Layer Controls	Gap Fill Percentage	35.0 Specifies the maximum allowable prism layer total thickness in percentage of an intersection distance—the normal distance between two boundaries.
	Minimum Thickness Percentage	0.01 Specifies the minimum allowable prism layer total thickness. Below this value the thickness is forced to zero. Due to the small gaps between rotors, this value is set to the minimal possible value 0.01.
	Prism Layer Reduction Percentage	0.0 Controls the point at which the number of layers is reduced. See also: 什么是层减少？ Zero indicates that no layer reduction is allowed.
Prism Layer Total Thickness	Percentage of Base	10.0

Right-click the Mesh Distributions node and select New Volume Distribution.
In the opened diaglog Parts for creating a new mesh distribution select the part PumpFluid and click Ok.
Select the Mesh Distributions > Volume Distribution > Default Controls > Number of Layers node and set the Number of Layers to 10.

Save the simulation with the name geroter_run.sim.