Noise prediction of a subsonic turbulent round jet using the lattice-Boltzmann method

Abstract

The lattice-Boltzmann method ͑LBM͒ was used to study the far-field noise generated from a Mach, M j = 0.4, unheated turbulent axisymmetric jet. A commercial code based on the LBM kernel was used to simulate the turbulent flow exhausting from a pipe which is 10 jet radii in length. Near-field flow results such as jet centerline velocity decay rates and turbulence intensities were in agreement with experimental results and results from comparable LES studies. The predicted far field sound pressure levels were within 2 dB from published experimental results. Weak unphysical tones were present at high frequency in the computed radiated sound pressure spectra. These tones are believed to be due to spurious sound wave reflections at boundaries between regions of varying voxel resolution. These "VR tones" did not appear to bias the underlying broadband noise spectrum, and they did not affect the overall levels significantly. The LBM appears to be a viable approach, comparable in accuracy to large eddy simulations, for the problem considered. The main advantages of this approach over Navier-Stokes based finite difference schemes may be a reduced computational cost, ease of including the nozzle in the computational domain, and ease of investigating nozzles with complex shapes.

Hermite regularization of the lattice Boltzmann method for open source computational aeroacoustics

“…Cavalieri et al, 71 Bogey et al, 72 Nichols and Lele 73 ). In the following, we will mainly refer to the case study proposed by Lew et al 18 who compared a commercial software based on LBM (PowerFLOW) jet noise predictions with the ones of a Navier stokes solver 74 (referred as NS-LES in what follows) and experimental data. 75,76 Here, this comparison is proposed again adding simulation results from the present LBM model.…”

“…The inclusion of the pipe geometry in the computational domain, performed with a simple bounce back boundary condition, 78 induces the spontaneous laminar-turbulent transition of the jet without the need of artificial forcing techniques, that are well known sources of spurious acoustic noise. 79,18,80 Although the pipe geometry is placed inside the finest refinement level (δx = 8 × 10 −4 m, dt = 1.4 × 10 −6 s), the boundary layer remains under In order to optimize the computational cost, the domain on the sides of the pipe is not considered in the calculation.…”

“…Interesting result have been obtained also for subsonic jet noise computations. 17,18,19 Lew et al 18,19 successfully simulate the noise generated for low and high subsonic jet including the nozzle geometry in the computational domain. The LBM turns out to be computationally more efficient with respect to the traditional NS-LES for low Mach number flow.…”

“…the propagation of acoustic and vortex pulses). Let us note, that Lew et al 18,19 in his jet simulations avoid the use of NRBC by damping the outgoing disturbances with a very coarse grid near the boundaries. Requiring a big computational domain with respect to the smaller physical domain of interest, this strategy can be computationally demanding.…”

Unsteady numerical simulation of a round jet with impinging microjets for noise suppression

“…This procedure has been argued to be analogous to an LES. [17][18][19] The nozzle geometry considered is the circular jet SMC000 described in previous studies by Bridges and Brown. 20 The nozzle has a conical slope of 5 and the exit diameter is D j ¼ 0.0508 m. The addition of a nozzle in the computational domain was intended to eliminate the need for an artificial forcing mechanism to trip the flow.…”