Handling of spatially truncated source fields based on pressure time derivatives in hybrid computational aeroacoustics

Abstract

In hybrid computational aeroacoustics, the acoustic computation domain is oftentimes larger than the domain of the flow simulation. Consequently, discontinuities of the source field occur on the acoustic mesh, which can diminish the quality of the results. A common way to handle truncated source fields is spatial windowing. The present work focuses on aeroacoustic approaches that use time derivatives of the incompressible base flow pressure as acoustic source terms and their distinctive character with respect to source domain truncation. Especially for those approaches, a novel alternative to spatial windowing is proposed, which uses a simplified pressure field continuation beyond the source domain. Numerical results display that spatial windowing and simplified pressure field continuation can both treat truncated source fields effectively. The windowing approach is computationally cheaper but exhibits issues for small flow computation domains. The simplified pressure field continuation can overcome these and other issues yielding very good results while adding little computational cost.

Aeroacoustic source term computation based on radial basis functions

“…To cope with this task, different interpolation strategies can be applied, starting from low complexity nearest neighbor interpolation to complex source‐term computation models with volume intersections between flow and acoustic grid. The simple nearest neighbor interpolation fails to compute the acoustic sources accurately (eg, References ). In Reference , the aeroacoustic source term is computed by summing the contributions of all flow cells belonging to finite elements that surround an acoustic finite element node.…”

“…As a solution to this problem, we derived a cut cell approach and successfully applied it to the aeroacoustic computation of an axial fan . Similar investigations have been performed in Reference , where for both the flow and the acoustic field a finite volume scheme has been used. However, most of these methods fail if the computational fluid dynamics (CFD) simulation only provides primary variables, such as the pressure p or the velocity u , since the aeroacoustic sources are often nontrivial combinations of these primary variables (see Figure ).…”