The microscopic fluid dynamics of a wire screen bound to a slit resonator excited by incident sound waves of different intensity are investigated numerically. The microscopic flow features help in understanding the acoustic behavior. A normal impedance-tube model is used in this investigation, and the wire mesh is modeled as an array of eight identical tiny circular cylinders arranged in parallel. Tonal waves of different sound pressure levels and frequencies are introduced from the termination of the tube through a non-reflecting boundary condition. Direct numerical simulations are carried out to solve for the flow and acoustic fields simultaneously, and the velocity and vorticity fields around the resonator are resolved. Upon closer inspection, the tiny cylinders suppress the vortex shedding from the slit excited by high-intensity incident sound waves, thereby retarding the nonlinear acoustic behavior of the slit. Furthermore, the wire mesh contributes greatly to the absorption of acoustic energy through scrubbing loss and flow separation. The acoustic impedance and absorption coefficient are derived using a two-microphone method. The numerical results show that the wire mesh increases the resistance of the resonator significantly while hardly affecting its reactance.

High-fidelity computational aeroacoustics simulations encounter significant challenges in industrial applications, especially in high Reynolds number flow regimes. These difficulties arise primarily from stringent requirements imposed by the Courant–Friedrichs–Lewy condition and the near-wall grid spacing, leading to prohibitively high computational costs. To address this limitation, this study presents a novel slip boundary condition for wall-modeled large eddy simulation that employs high-order finite-difference methods based on the dispersion-relation-preserving scheme. The slip boundary condition prescribes the tangential velocity at solid walls while enforcing zero normal penetration. The slip velocity is derived from a linearized near-wall velocity profile approximation at the sample point, significantly reducing grid resolution requirements. The slip boundary condition is first validated in turbulent channel flows at Reτ=2000 with optimized grid spacings (δ/Δx=20, δ/Δz=30, δ/Δy=20–30, δ: boundary-layer thickness), yielding mean velocity profiles and Reynolds stresses that closely match direct numerical simulation (DNS) benchmarks. Additionally, errors in the low-to-mid frequency components of the power spectral density remain within 3–6 dB. The optimized grid spacings are further validated over a range of friction Reynolds numbers (Reτ=576–5100). Besides, a synthetic turbulence inflow method is developed by superimposing divergence-free, spatially correlated steady jet structures onto the mean flow, integrated with the radiation nonreflective boundary conditions. The time-invariant source terms maintain computational efficiency while effectively suppressing spurious numerical oscillations. The synthesized velocity profiles and Reynolds stresses show excellent agreement with DNS data. While the spectra exhibit overprediction in amplitude, the characteristic shape maintain consistency with Goody's empirical model.

Recently, the aerodynamic performance of acoustic liners has become a research focus. It is necessary to study the influencing factors of the acoustic liner drag to further reduce engine fuel consumption and emission. In this paper, a drag balance is designed to directly measure the liner drag in a grazing flow tube. The test samples include conventional acoustic liners, multi-slot acoustic liners, and a smooth wall set as a reference for comparison. All the test samples are under the fully developed grazing flow with variable bulk Mach number (M) from 0.1 to 0.6. The effects of the configuration characteristics of the acoustic liner on the flow drag are studied. Experimental results show that the design parameters of the acoustic liner have considerable influence on the flow drag, including the perforation size, plate thickness, porosity, perforation layout, and fabric mesh. Besides, a conventional liner is tested to evaluate the effects of acoustic tonal excitation with the sound pressure level up to 150 dB between 500 Hz and 1700 Hz. The extra drag induced by the incoming sound waves can increase by 137% at M = 0.1. But the increasing flow speed will suppress this extra drag penalty in this study.