Scenario 1:

Imagine we have a solid volume next to a fluid volume – with a single set of nodes common to (shared by) the two volumes.  For AcuSolve, the complete model would have a surface defined attached to the fluid, and another surface defined attached to the solid – again, sharing the same nodes.  The export from HyperMesh now contains the definitions of those two surfaces, so all is good. (I’m not sure if this is accomplished by simply having the volume elements in two different components – or if one component has to be defined as Solid and the other as Fluid.  Marc – Please clarify…)

Scenario 2:

Imagine we have a surface (baffle) within the fluid volume to be treated as a wall, with fluid on each side (let’s say a right side and a left side).  For AcuSolve, the complete model would have a surface defined attached to the fluid on the left, and another surface defined attached to the fluid on the right – again, sharing the same nodes.  If the model is run with this, there will be BC-Warnings related to having a boundary condition on internal surfaces.  So we must use the ‘Split Internal Surfaces’ function to generate two sets of nodes – one attached to the fluid volume on the left, and one attached to the fluid volume on the right.  This means we must also have two distinct surface definitions so we can assign boundary conditions – one surface defined attached to the fluid on the left, and another surface defined attached to the fluid on the right.  (The surface definitions will now be comprised of distinct nodes – except maybe at edges of those internal surfaces where they may be shared.) The ‘Split Internal Surfaces’ operation does not generate new surface definitions.  In other words, if the original mesh only had the surface defined attached to the volume on the left – and no surface defined attached to the volume on the right, after the ‘Split Internal Surfaces’

operation, the volume on the right will not have a defined bounding surface – and we will get BC-Warnings indicating there are Fluid nodes without any BCs.  These MUST be corrected in order for the setup and solution to be correct.  The method would be to use the ‘Find Missing Surfaces’ operation in AcuConsole.  I generally do this Volume by Volume and then study any new surfaces that get created.  Then re-group (as

desired) and apply appropriate BCs to the new surfaces and proceed.