Large-Scale Numerical Simulation of Unsteady Flow Field in a Half-Ducted Propeller Fan Using Lattice Boltzmann Method

Abstract

Recently, the lattice Boltzmann method (LBM) is being applied in turbomachinery field, regarded as a good candidate for tool of flow simulation as well as aerodynamic sound analysis. For better prediction of broadband noise with high frequecy, which is generally generated in high Reynolds number flows, not only high grid resolution is required to capture very small eddies of the sound source inside the turbulent boundary layer, but also the computation of acoustic field is often needed. In such case, the direct simulation of flow field and acoustic field is straight-forward and effective. However, the computational cost becomes extremely expensive. Moreover, for low Mach number flows the compressible Navier-Stokes simulation not only requires high-order scheme which is unsuitable for parallel computation, but also suffers from stiff problem. LBM is suitable for such simulation thanks to its advantages. In the present study, a large-scale numerical simulation of flow field around a half-ducted propeller fan is conducted with LBM, and its result is validated by comparing with the experimental result.

Lattice Boltzmann simulation of flow and sound fields around an axial flow fan

“…In fact, the potential of LBM in application to aeroacoustic computations for low Mach number flows has been reported [8][9][10]. Moreover, the LBM begins to be actually applied to the simulation of low speed fans [11][12][13][14][15]. However, there still exists a challenge in prediction of broadband noise radiated from an attached flow around a fan.…”

Aeroacoustic simulation of broadband sound generated from a cross-flow fan using immersed boundary-lattice Boltzmann method

“…After the flow simulation, the acoustic field is calculated from unsteady flow data based on Lighthill's acoustic analogy [3]. On the other hand, recently, a direct approach using the lattice Boltzmann method (LBM) has been attracting substantial attention [4,5]. The LBM can simultaneously simulate the flow and acoustic fields under low-Mach-number conditions owing its capability to accurately solve weakly compressible flows.…”