Time-domain transmitting boundary condition in fluid-structure interaction studies

One of the major difficulties in the nonlinear analyses of fluid-structure interactions has been the lack of exact expressions for the transmitting boundary in the time domain. Researchers in the past have adopted the Sommerfeld radiation condition (1912) in their calculations using the assumption that the outgoing waves are nearly planes at large distance from the disturbance. This assumption was used by many for many years. However, no assessment has been made regarding its suitability and accuracy. In 1990 the authors have advanced an exact time-domain transmitting boundary condition for fluid-structure interaction problems. In this paper comparisons of results are made by using the Sommerfeld radiation condition and by using the exact solution for the fluid transmitting boundary. It will be shown that there exists significant differences in results by using these two approaches, and that the exact transmitting boundary condition yields considerably more accurate results in cases when exact solutions are known.