A new-born design and construction of a mini gerotor metering pump with trochoidal-teeth is presented. The technical innovation in this new-born design is to study the fluid dynamic effects of interteeth and lateral clearances by using OpenFOAM toolbox, an open source CFD software. This work is based on two critical aspects, the deforming of the mesh following the solid gears rotation, a complex interaction between mesh and gear profile surface that has to maintain a moderate quality of the mesh, and the simulation by means of a new boundary condition of the interteeth contact, reproducing actual contact points between the rotors. The posibility of contact point simulation by means of a proper mesh motion model is also suggested.