Adapting a slit model to determine the aeroacoustic response of tube rows

Cylindrical tubes in cross-flow, like the ones found in heat exchangers, are excellent acoustic dampers and as such have the potential to mitigate thermoacoustic instabilities. Flow separation and vortex shedding downstream of the tube row are key to significantly enhancing sound attenuation. However, constructing an analytical solution for the aeroacoustic response of tube rows in cross-flow is very challenging owing to the complex flow structure, vortex shedding and coupling with acoustics. To overcome this, we propose the adaptation of a slit model for tube row acoustic scattering (aeroacoustic response) predictions at low Strouhal numbers. The slit model was modified such that the loss coefficients across the slit and the tube row matches. The model is then validated against numerical predictions using Linearised Navier Stokes Equations and experimental measurements. The predictions for both magnitude and phase for transmission and reflection coefficients agree well with the simulations and experiments.