Acoustic-induced velocity in a multi-orifice acoustic liner grazed by a turbulent boundary layer

View Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2169.vid

High-fidelity lattice-Boltzmann very-large-eddy simulations have been carried out to investigate the behaviour of a single-cavity multi-orifice acoustic liner grazed by a turbulent boundary layer at free-stream Mach number equal to 0.3 and an acoustic wave. Numerical results have been used to compute the acoustic-induced velocity within the liner orifice with a triple decomposition approach. It is shown that the acoustic-induced velocity presents a symmetric behaviour between the inflow and outflow cycles and that its amplitude is the same as for the case without turbulent grazing flow. The major differences when comparing the case with and without turbulent grazing flow is the spatial distribution within the orifice attributed to the presence of a quasi-steady vortex formed within the orifice visible from the time-averaged flow field. It is concluded that the increase of resistance in presence of a turbulent grazing flow is linked to a reduction of the effective orifice area as confirmed by the comparison between the mass-flow rates for the cases with and without grazing flow.