Parallel universal approach to mesh motion and application to rotors in forward flight

Numerical simulation of unsteady flows including moving boundaries, whether rigid, prescribed, or deforming, requires the mesh to move/deform also. Many approaches to mesh motion have been considered, but the approach adopted often depends on both the meshing approach used and the proposed application. A universal approach to grid motion is presented here. The method developed has several important properties, the most significant of which is that the scheme requires no grid point connectivity information, i.e. each point can be moved totally independently to its neighbours. This has two major implications: first, it means the scheme is universal, i.e. applicable to any grid type, unstructured, hybrid or structured single- and multiblock. Second, and equally as important, is that the scheme is perfectly parallel, as no communication is required between points/blocks. Each block can be updated independently to its neighbours so there is no connectivity data required, and this also means the flow-solver does not have to carry the grid motion parameterization data in memory. The scheme accounts for moving surface rotations as well as displacements, and this ensures grid quality is preserved by maintaining orthogonality. The method is applied to a four-bladed lifting rotor in forward flight. This is a particularly challenging unsteady problem as there are multiple bodies in relative motion, each one with its own axis system, as each blade has a cyclic pitch variation. Grid quality is proven to be preserved even when a large deformation case is considered and, significantly, the scheme adds only around 1% to the cost of a flow solution real time step. Copyright q 2006 John Wiley & Sons, Ltd