Case Study by DaimlerChrysler

Internal Flow through a Water Pump

The purpose of a recent study performed by DaimlerChrysler was to compare the performance of Harpoon-based CFD against previous solutions using tetrahedral meshes.

The effect of mesh skew on accuracy and convergence was observed. 14 operating cases were simulated: 1000-7500rpm at 500rpm increments. Inlet velocities were derived based on the test mass flow measurements. Pressure rise & flow split between volutes were solved. Excellent agreement was obtained using a Harpoon mesh, containing approximately 3M cells, at a fraction of the simulation effort required for a full tet mesh. The following was concluded from this effort:

• The hexa-dominant mesh improves the convergence quality & rate of the model, even with reduced mesh resolution
• Mass conservation residuals dropped by up 90%
• Kinetic Energy residuals dropped by up to 20%
• Convergence time was reduced by more than 30% for the initial condition case, up to 80% for the consecutive cases

Details of the model are shown in figure 1. A close-up of mesh details is shown in figure 2. Figures 3 and 4 compare results for Harpoon meshes (blue) against tet mesh results (magenta). (all data courtesy DaimlerChrysler)