Low-Speed Turbofan Aerodynamic and Acoustic Prediction with an Isothermal Lattice Boltzmann Method

Abstract

The objective of the paper is to assess the capability of the isothermal Lattice Boltzmann Method (LBM) to correctly capture aerodynamic and acoustic features from a low-speed turbofan. The evaluation is done on the Advanced Noise Control Fan (ANCF) model developed by NASA Glenn Research Center. An extensive comparison of the measured and computed aerodynamic results is presented for the first time on this configuration. The trends are well captured but quantitative discrepancies are observed for some variables, leading to lower fan performance values in the simulations. This last point was also observed in the previous related studies but remained unexplained. By validating in parallel the LBM aerodynamic results with a Reynolds-Averaged Navier-Stokes (RANS) simulation provided by the database, a likely uncertainty of the absolute values of some variables in the experimental mean flow data is shown (a result of the intent that experimental data was not acquired with absolute levels as an objective). Direct in-duct and far-field acoustic results are also investigated, taking advantage of the low-dissipative characteristics of the LBM. A good agreement with the measurements in terms of broadband noise is obtained, but the low frequencies tend to be overestimated. For the tonal noise, if the expected acoustic modes are recovered, quantitative differences are observed. Predictions based on an hybrid method where the acoustic sources computed by the LBM are propagated analytically using Goldstein's analogy are also made and compare well with the direct predictions, thus proving the correct propagation of acoustic waves by the solver.

Aeroacoustics research in Europe: The CEAS-ASC report on 2020 & 2021 highlights

“…The objective of this study [95] was to assess the capability of the isothermal lattice Boltzmann method (LBM) to correctly capture aerodynamic and acoustic features from a low-speed turbofan. The evaluation has been done on the Advanced Noise Control Fan model developed by NASA Glenn Research Center [96] and an extensive comparison of the measured and computed aerodynamic results has been presented for the first time on this configuration.…”

Inter-Compressor Annular S-duct Simulations using the Lattice Boltzmann Method

“…Additionally, the LBM offers a competitive computational time due to an easy parallelization because of its simple and local algorithm. Thanks to these advantages LBM-LES approaches have been successfully applied to industrial applications Daroukh et al (2021). However, the standard LBM formulation is restricted to athermal, incompressible flows Kruger et al (2017).…”

Large eddy simulation of a thermal impinging jet using the lattice Boltzmann method

“…The use of Cartesian octree meshes, although not without its disadvantages, can make pre-processing and mesh generation significantly easier to automate, greatly reducing the amount of working time needed by a highly trained specialist. LBM-LES approaches have been sucessfully applied to industrial applications 14,15 .…”