The refinement process using ROIs can give more flexibility to users and it can show better performance results compared with boundary proximity. This performance improvement in relation to refinement by boundary proximity is because the refinement by ROI tends to generate less refinement SPH elements than using boundary proximity.
In this method, the same principles of refinement applies here, see SPH Adaptive Sizing Method Overview and Refinement with boundary proximity, the difference concerns with the region of refinement. In Ansys FreeFlow there are two types of ROI, cylinder and cube. For cylinders there's a possibility to specify a hole ratio, then the refinement zone will be all the volume outside the hole ratio. If no hole ratio is specify for ROI, so all elements that are in the cylinder internal volume will be refined. The Figure 2.5: The different refinement regions for ROI cylinder with hole ratio, ROI cylinder without hole ratio and ROI cube. shows the three possibilities of using cylinder ROI and cube ROI with SPH Adaptive Sizing on Ansys FreeFlow.
Figure 2.5: The different refinement regions for ROI cylinder with hole ratio, ROI cylinder without hole ratio and ROI cube.
Once the refinement region is a definition concerning the geometry of ROI, it is not necessary to define a Refinement Distance Factor parameter, only the Refinement Level parameter for each ROI. An example of refinement using ROI in FreeFlow is shown in Figure 2.6: Refinement using a cylinder ROI on FreeFlow.
