Here are some basic tips on how to get to a good mesh in CFD inside Flow Simulation:
Start by creating a mesh using the default (automatic) mesh settings. Start with a Level of initial mesh at 3. It is important to enter the appropriate values of the minimum gap size and minimum wall thickness, which will provide you with a suitable mesh. The default values of the minimum gap size and minimum wall thickness are calculated using information about the overall model dimensions, the Computational Domain size, and area of surfaces where conditions (boundary conditions, sources, etc.) and goals are specified. Don’t switch off the Optimize thin walls resolution option, since this allows you to resolve the model’s thin walls without the excessive mesh refinement.
Next, closely analyze the obtained automatic mesh – the total numbers of cells created, especially near wall regions and narrow channels. If the automatic mesh does not appear to resolve these regions adequately and changing the minimum gap size and minimum wall thickness values do not give the desired effect you can proceed with a custom or local mesh. Also, if the number of cells created are extremely high, then take a look at areas where the mesh cells are unnecessarily dense.
Start to create your custom mesh with the narrow channel refinement disabled, while the Small solid features refinement level and the Curvature refinement level are both set to 0. This will produce only zero level cells (basic mesh only).
Next, adjust the basic mesh by incrementally increasing the Small solid features refinement level and the Curvature refinement level. Then, enable the narrow channels refinement. You can also use control planes to optimize the basic mesh if necessary.
Finally, try to use the local mesh settings. You can tweak the number of cells around faces, edges, vertices, and even components. I particularly like controlling the partial and fluid cells close to faces by using local mesh control.
Another common trick I like to employ is to create a dummy body in SOLIDWORKS (as a separate part file) that envelopes the area of interest requiring mesh refinement. You can apply component level local mesh control to this block and tweak all the fluid and partial cells inside this block using the slider bars, and thus refine all the cells inside this volume. Keep in mind though that you have to Disable this dummy component (from Component Control) in order to dissolve the body in the fluid.
Have fun meshing!! Keep in mind that you can always study the mesh in 3D (not recommended due to overload on graphics card), or you can study the mesh in 2D using Cut Plots (recommended approach). A good mesh leads to a good solution!!