General Remesh: Gerotor Pump with Small Gap

A Gerotor pump is a unit with an inner and an outer rotor that have different rotational speeds related to their tooth numbers. The dynamically changing volume between the rotors transports the liquid from inlet to outlet.

The technical challenge in modeling gerotor pumps is handling small gaps between the rotors. Morphing the rotational motions leads to a decrease of mesh quality in the small gaps. To handle this issue in Simcenter STAR-CCM+, you can apply the remeshing model with its proactive mesh quality check. See also: General Remeshing.

Due to the shape of a gerotor pump the geometry repeats itself after rotating a segment between two teeth. In the example used for this tutorial, the geometry repeats after 30° for the slower rotating outer rotor with 12 teeth and 32.73° for the faster rotating inner rotor with 11 teeth. The time period for both repeats is 5 ms.

The relationship between the rotational speeds (Rotation) and the numbers of teeth (N) is expressed as follows:

Figure 1. EQUATION_DISPLAY
R o t a t i o n _ i n n e r × N _ i n n e r = R o t a t i o n _ o u t e r × N _ o u t e r
(5261)

In the Remeshing model, you apply repeating meshes with cyclic matching to reuse the saved meshes at certain positions to avoid too many unnecessary remeshings.

The geometry parts of the tutorial are shown as follows: