On the generation of turbulent inflow for hybrid RANS/LES jet flow simulations

Abstract

The present work is devoted to the assessment of a low-noise turbulence generation methodology used to produce boundary layer with three-dimensional resolved turbulence at the exit of a jet nozzle to reproduce experimental conditions. The method relies on the use of roughness elements introduced in the computational domain with Immersed Boundary Conditions and ZDES mode 3 (Wall Modelled LES branch of ZDES). The simulation of a round jet at M=0.9 and Reynold number 10 6 with turbulence generation is compared to a simulation with no resolved turbulence in the nozzle boundary layer using ZDES mode 2. The behaviour of the boundary layer downstream of the roughness elements inside the nozzle is scrutinized using two grids. The turbulence generation method combined with ZDES mode 3 produces satisfying levels of resolved turbulence at the nozzle exit. The early stages of the shear layer development are modified by the ZDES mode 3 simulations providing an initially turbulent boundary layer. On the other hand, the ZDES mode 2 simulations, with a turbulent mean exit velocity profile but no resolved turbulence, display a short area of strong shear layer instabilities leading to the quick development of threedimensional turbulence in the mixing layer. The present results give insights on the level of turbulent modelling of the nozzle boundary layer needed depending on the purposes of the jet flow simulations considered.

hp -adaptive hybrid RANS/LES simulations for unstructured meshes with the discontinuous Galerkin method

“…Surprisingly, we can observe how the adaptive simulation hpG2 seems to provide closer results to the experiment, while the more refined hpG3 mesh overestimates the length of the potential core. Even though this results could seem unexpected, this behaviour has been already pointed out by Shur et al in [65] (in orange lines), and can be found in results from Brès et al [62] (in green lines) and Gand et al [63] (in magenta lines) as well. The trend is clear, even though for Shur and Gand this is more marked than for Brès.…”

“…The nozzle test case analysed in this work corresponds to the configuration described in [62], for which experiments have been performed at the Bruit & Vent jet-noise facility of the Institut PPRIME, Poitiers, France, with reference data available. Numerical results are available as well in the literature: this configuration has been simulated with LES by Brès et al [62] to analyse features as near-wall adaptive mesh refinement, synthetic turbulence and wall modelling inside the nozzle in LES, with hybrid RANS/LES by Gand et al in [63] to assess the generation of a turbulent inflow and with RANS by Neifeld et al [64] for jet noise prediction purposes with eddy relaxation source model.…”

“…The mean streamwise velocity profiles on the jet axis 𝑟/𝐷 = 0 and on the lipline 𝑟/𝐷 = 0.5, are compared to experimental and numerical results obtained by Brès et al [62] in green lines, Gand et al [63] in magenta lines, Shur et al [65] in orange lines, and Lorteau et al [40] in cyan lines, whose parameters and numerical set-up can be found in table 2. Dotted lines represent the coarse grid for each reference, while dashed lines represent fine grids.…”

Unstructured h- and hp-adaptive strategies for discontinuous Galerkin methods based on a posteriori error estimation for compressible flows

“…This configuration has been simulated using LES by Brès et al [82] to analyse features as near-wall adaptive mesh refinement, synthetic turbulence and wall modelling inside the nozzle. Hybrid RANS/LES simulations have been performed by Gand et al in [83] to assess the generation of a turbulent inflow, and RANS simulations by Neifeld et al [84] for jet noise prediction purposes with an eddy relaxation source model.…”

Tetrahedral remeshing in the context of large-scale numerical simulation and high performance computing

“…We appraise the above adaptive remeshing strategy in the physical context described in [22], for which experimental and numerical data are available in the literature, see also [57] and [79] for further investigations aimed at predicting turbulence generation and jet noise.…”