Small amplitude modelling of acoustic damping cavities

We will first recall the classical results for the laminar dissipation of acoustic energy in the boundary layer of a forced resonator. We then show how this result can be used in conjunction with a Helmholtz solver to calculate the laminar damping of a cavity of arbitrary geometry. The approach is validated by application to a trivial geometry for which the result is known analytically (HF1 step 1). We then present the results for the remaining test cases (HF1 steps 2, 3 and 4). The computational effort is lightweight, ranging from a few seconds of cpu time for step one to a few minutes for the 3-D case, step 4. These test cases are nonreacting, but the approach can be extended to accommodate strong temperature variations, provided the temperature and density fields are known. Finally we discuss the limitations of this approach and possible reasons for differences between these calculations, full DNS calculations, and experimental measurements on real chambers.