Large Eddy Simulation of a Lobed Mixer Nozzle using a Multi-Block Method

Abstract Large Eddy Simulation (LES) using a multi-block method with a parallel computational algorithm was applied to predict the mixing characteristics of a lobed mixer nozzle flow. In the LES, the Favre filtered compressible Navier-Stokes equations were used for the governing equations and the Smagorinsky subgrid scale turbulence model with Smagorinsky constant 0.15 was introduced in order to determine the SGS turbulence viscosity. First, the LES of a computational model with 7.5 million grid points for a 18-lobe convoluted mixer nozzle was conducted. In the LES calculation, only one-lobe domain of the mixer nozzle was simulated using circumferential periodic boundary conditions at circumferential boundary ends of the computational domain. The computational domain was divided into 9 sub-domains. The LES results were evaluated by comparing with measured data acquired by using particle image velocimetry (PIV) technique, and the good agreement between the LES results and the experimental data was obtained. Next, the LES application was extended to a three-lobe domain of the mixer nozzle. The computational domain was divided into 19 sub-domains and the total number of the computational mesh was about 15.6 millions. The LES calculation was performed by increasing sub-domains without so many modifications of the computational program. From these results, it was demonstrated that the LES using the multi-block method with the parallel computational algorithm had the capability to predict the flowfield of a large computational domain with a huge number of grid points.