For flow simulations, proper boundary conditions are essential for realizing a well-posed, physically meaningful and numerically stable problem formulation. This is particularly difficult for compressible flow, where in general boundary conditions have to be imposed both for mean flow and acoustic quantities. For the acoustic variables, boundary conditions can be formulated in terms of the acoustic impedance or alternatively the reflection coefficient, which are general a complex-valued, frequency dependent quantity. The present work presents a novel, efficient and flexible approach to impose time-domain impedance boundary conditions (TDIBC) for computational fluid dynamics (CFD): The acoustic boundary conditions are represented as a discrete filter model with appropriately optimized filter coefficients. Using the z-transformation the filter model is transferred to a time-domain formulation and applied to the CFD environment in form of advanced filter realizations. Validation studies using various acoustic boundary conditions have been carried out with the new formulation. The results demonstrate that the method works in an accurate and robust manner.

This content is only available via PDF.
You do not currently have access to this content.