Orthogonal Mesh Generation of Screw Compressors for Capturing Tip Leakage Flows

Structured meshes have been the industry standard for CFD simulations of positive displacement rotors for the last few years. There are many players in the market who offer structured meshes. However, current techniques have a few limitations. There is always a challenge in geometry capturing, mesh quality and the physics that needs to be resolved. The lack of a conformal meshing solution which offers robustness in geometry capturing and orthogonal tip gap resolution often poses a hurdle in obtaining accurate CFD predictions. This paper proposes a novel, automated, multi-block structured meshing technique for positive displacement machines. This approach proposes a structured conformal mesh which creates an orthogonal mesh around the tip gaps and accurately captures the rotor and housing as a single domain mesh. The mesh is also created orthogonal to the helical angle of the rotors, ensuring flow-alignment of the meshes up to a clearance of 4 microns, consequently reducing diffusion errors and giving better results of the tip leakage flows. This new technique will enable users to obtain far more accurate CFD results on positive displacement machines.