An acoustic model of a Helmholtz resonator under a grazing turbulent boundary layer

Abstract

Acoustic models of resonant duct systems with turbulent flow depend on fitted constants based on expensive experimental test series.We introduce a new model of a resonant cavity, flush-mounted in a duct or flat plate, under grazing turbulent flow. Based on previous work by Goody, Howe and, Golliard, we present a more universal model where the constants are replaced by physically significant parameters. This enables the user to understand and to trace back how a modification of design parameters (geometry, fluid condition) will affect acoustic properties.The derivation of the model is supported by a detailed three dimensional Direct Numerical Simulation as well as an experimental test series. We show that the model is valid for low Mach number flows (M = 0.01-0.14) and for low frequencies (below higher transverse cavity modes). Hence, within this range, no expensive simulation or experiment is needed any longer to predict the sound spectrum. In principle the model is applicable to arbitrary geometries: Just the provided definitions need to be applied to update the significant parameters. Utilizing the lumped element method, the model consists of exchangeable elements and guarantees a flexible use. Even though the model is linear, resonance conditions between acoustic cavity modes and fluid dynamic unstable modes are correctly predicted.

Resonansi Helmholtz: Pegas dalam Botol

“…Selain itu, pusaran tertentu dalam turbulensi dapat distabilkan oleh osilasi resonator dan kemudian memancarkan suara siulan ke dalam aliran saluran (Meyre,1958) Dengan menggunakan botol yang merupakan resonator dengan rongga terbuka. Yang mana ini memiliki keuntungan yang lebih dikarenakan karakteristik aliran resonator rongga terbuka lebih stabil dibandingkan resonator rongga tertutup (Stein & Sesterhenn, 2019). Sehingga dengan demikian kita dapat menentukan kecepatan aliran optimal untuk menghasilkan sinyal yang baik dengan memperhatikan energi yang diperlukan dan meminimalisir ketidakstabilan pada kecepatan aliran (Njane et al, 2018).…”

Direct Numerical Simulation of an Oblique Jet in a Particle-Laden Crossflow

“…Time integration is performed through a low-storage 4th order Runge-Kutta scheme while, as concerns the space discretization, a 6th order Summation By Parts finite difference scheme is adopted. The parallelization (MPI) is achieved by a hybrid approach using a multi-block code with a ghost layer synchronization as well as block internal decomposition into CPUs as explained in [14]. The dispersed phase is simulated by adopting a Lagrangian two-way coupling point-particle approach.…”