Direct aeroacoustic simulation of acoustic radiation in recorders with different windway geometries

Abstract

To clarify the effects of the windway geometry on the aeroacoustic feedback in the jet fluctuations in recorders, direct aeroacoustic simulations were performed along with experiments. The simulations were based on the compressible Navier-Stokes equations to predict the fluid-acoustic interactions. The volume penalization method was used to reproduce the flow and acoustic fields around the complex shape of the recorders. Two recorders with straight and arch-shaped windway were explored. The occurrence of mode change was observed at the higher velocity for an arch-shaped windway model compared with the straight windway model. The modified formulation of the negative displacement model (N.H. Fletcher et al., 1976, J. Acoust.) was proposed based on the predicted jet fluctuations, where the jet fluctuations were divided into hydrodynamic and acoustic components. The ratio of the hydrodynamic component to the acoustic component near the windway exit was lower in the archshaped windway model than that in the straight windway model, whereas the amplification factor of the jet fluctuations was larger in the arch-shaped windway model.The relevance of these results and the mode change along the jet velocity is to be discussed.To clarify the effects of the windway geometry on the aeroacoustic feedback in the jet fluctuations in recorders, direct aeroacoustic simulations were performed along with experiments. The simulations were based on the compressible Navier-Stokes equations to predict the fluid-acoustic interactions. The volume penalization method was used to reproduce the flow and acoustic fields around the complex shape of the recorders. Two recorders with straight and arch-shaped windway were explored. The occurrence of mode change was observed at the higher velocity for an arch-shaped windway model compared with the straight windway model. The modified formulation of the negative displacement model (N.H. Fletcher et al., 1976, J. Acoust.) was proposed based on the predicted jet fluctuations, where the jet fluctuations were divided into hydrodynamic and acoustic components. The ratio of the hydrodynamic component to the acoustic component near the windway exit was lower in the archshaped windway model than that in the st...