The overall density of the generated mesh is based on the Element Size parameter. The larger the Element Size is, the less accurate the results will be. However, the computational cost and memory requirement of the Hydrodynamic Diffraction calculation will scale with the square of the number of diffracting elements. This means that you may need to find a balance between accuracy and computational cost. The 64-bit version of the Aqwa solver is limited to 60,000 nodes and 40,000 elements, of which 30,000 may be diffracting.

Once the mesh has been generated, the Maximum Allowed Frequency field will display the maximum wave frequency that can be included in the Hydrodynamic Diffraction analysis. This is based on the Aqwa solver requirement of no less than 7 elements over the shortest wavelength in the hydrodynamic database.

Previously, it was mandatory to use the Geometry editor to split or slice your geometry over the waterline (at Z = 0 in the XY plane) to ensure that diffracting panel elements do not cross it. Internal Tank surfaces also had to be split or sliced at the internal tank fluid level. Now, you can generate a mesh which includes waterline and internal tank fluid level nodes automatically, by setting Create Automatic Waterline Nodes to Yes. When this option is on, you can adjust the Connection Tolerance between the water surface (or internal tank fluid surface) and the real vessel surfaces in your model, which is sometimes required to get a satisfactory mesh.

If the Create Automatic Waterline Nodes option is set to No, the meshing Engine Selection option is displayed. You can switch between AnsMeshing and PRIME, though in practice, the meshes created by these two engines are often similar. Without automatic waterline node generation, it is still required to split or slice your geometry at the waterline and internal tank fluid levels in the Geometry editor.

When Create Automatic Waterline Nodes is set to No, and the Engine Selection is set to AnsMeshing, the Aqwa Workbench mesh will be equivalent to a Mechanical Mesh with the Physics Preference set to Hydrodynamics and the Batch Connections option set to No. When using the AnsMeshing engine, you can adjust the Defeature Size to control how small details are treated in the mesh. For example, if a geometry detail is smaller than the Defeature Size, a single element may span over it. You can also choose to apply Advanced Options for sizing and defeaturing – for more information, see Sizing Group in the Meshing User's Guide.

When Create Automatic Waterline Nodes is set to No, and the Engine Selection is set to PRIME, the Aqwa Workbench mesh will be equivalent to a Mechanical Mesh with the Physics Preference set to Hydrodynamics and the Batch Connections option set to Yes. However, for an Aqwa analysis, you must still group rigidly-connected Bodies into a single Part with shared topology in the Geometry editor.

When Create Automatic Waterline Nodes is set to Yes, the PRIME meshing engine is always used. The Aqwa Workbench mesh will be equivalent to a Mechanical Mesh under these conditions:

In the configuration above, the fluid Surface Height (in Global Axes) for an Internal Tank can be defined directly and marked as an input parameter for a Design Point study.