Domain-decomposition method for time-harmonic aeroacoustic problems

A domain-decomposition (DD) method is developed for parallel computation of time-harmonic aerodynamic-aeroacoustic problems. The computational domain is decomposed into subdomains, and the aerodynamic-aeroacoustic boundary-va lue problem is solved independently for each subdomain. Impedance-type tran smission conditions are imposed on the artificially introduced subdomain bo undaries to ensure the uniqueness of the solution. A Dirichlet-to-Neumann m ap is used as a nonreflecting radiation condition along the outer computati onal boundary Subdomain problems are then solved using the finite element m ethod, and an iterative scheme updates the transmission conditions to recov er the global solution. The present algorithm is implemented for two model problems. First, the sound radiated from a surface simulating a two-dimensi onal monopole is calculated using an unstructured mesh. Second, the dow abo ut a thin airfoil in a transverse gust is computed using a structured mesh. The accuracy of the numerical scheme is validated by comparison with exist ing solutions for both the near-field unsteady pressure and the far-field r adiated sound. The convergence and the computational time and memory requir ements of the present method are studied. It is shown that by combining the subdomain direct solvers with global iterations this DD method significant ly reduces both the computational time and memory requirements.