Flow and noise solutions of the two Large Eddy Simulation (LES) approaches are evaluated for the jet flow conditions corresponding to a benchmark co-axial jet case from the EU CoJeN (Computation of Coaxial Jet Noise) experiment. The jet is heated and issues for a short-cowl axi-symmetric nozzle with a central body at a transonic speed. The first LES method is based on the Compact Accurately Boundary-Adjusting high-REsolution Technique (CABARET) scheme, for which implementation features include asynchronous time stepping at an optimal Courant-Friedrichs-Lewy (CFL) number, a wall model, and a synthetic turbulence inflow boundary condition. The CABARET LES is implemented on Graphics Processing Units (GPUs). The second LES approach is based on the hybrid 2 Reynolds Averaged Navier-Stokes (RANS)/ Implicit LES method that uses a mixture of high-order Roe and WENO scheme and a wall distance model of the Improved Delayed Detached Eddy Simulation (IDDES) type. The RANS/ILES method is run on an MPI cluster. Two grid generation approaches are considered: the unstructured grid using OpenFOAM utility "snappyHexMesh" (sHM) and the conventional structured multiblock body-fitted curvilinear grid. The LES flow solutions are compared with the experiment and also with solutions obtained from the standard axi-symmetric RANS method using the k- turbulence model. For noise predictions, The LES solutions are coupled with the penetrable surface formation of the Ffowcs Williams-Hawkings method. The results of noise predictions are compared with the experiment and the effect of different LES grids and acoustic integration surfaces is discussed.

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Статья посвящена применению RANS/ILES-метода высокого разрешения для изучения влияния неоднородности поля температуры набегающего потока на дроссельные характеристики сверхзвукового воздухозаборника смешенного сжатия, интенсивность и спектральные характеристики пульсаций давления в канале воздухозаборника. Исследовано пять вариантов параметров набегающего потока, три из которых имели неоднородное поле температуры. Получены распределения уровня звукового давления в канале воздухозаборника и спектры пульсаций в точках на стенках.

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Hybrid Reynolds-Averaged Navier-Stokes/Implicit Large Eddy Simulation (RANS/ILES) highresolution method was applied to investigate synthetic jets influence on potential core length and noise level in supersonic underexpanded jet from converging-diverging nozzle. In this work, temperature and pressure of ambient air were as follows: P ¼ 100 kPa, T ¼ 300 K. Nozzle pressure ratio was NPR ¼ 4 and total temperature at the nozzle inlet was T Ã in ¼ 300 K. Investigation of the accuracy of simulation was carried out before the investigation of synthetic jet influence. Synthetic jets were simulated using approximate boundary condition. Synthetic jets were injected from eight rectangular slits inside nozzle with step of 45 in azimuthal direction. The long sides of the slits were oriented along the longitudinal axis of the nozzle. The amplitude and frequency range of synthetic jets were as follows: q ¼ 50.200 m/s, f ¼ 60.300 Hz. Simulation results showed that the application of synthetic jets noticeably reduces the potential core length. Reducing the potential core length by 24% was achieved on one of the considered operating modes. An explanation for the mechanism of the action of synthetic jets on mixing layer of main jet flow was proposed. Synthetic jets influence on overall sound pressure and narrowband noise was revealed in near and far field. Operating modes, which decrease screech level on several observation angles, were found.