Turbulent jet characteristics for axisymmetric and serrated nozzles

Abstract

Turbulent jet large eddy simulations (LES) are performed at Mach 0.9 and Reynolds number around 10 6 . Implicit large-eddy simulation (ILES) is employed, namely omitting explicit subgrid scale models. The Reynolds-averaged Navier-Stokes (RANS) solution is blended into the near wall region. This makes an overall hybrid LES-RANS approach. A Hamilton-Jacobi equation is applied to remove the disparate turbulence length scales implied by hybridization. Computations are contrasted for a baseline axisymmetric (round) nozzle and a serrated (or chevron) nozzle with high bending and penetration. Jet characteristics for both nozzles are studied in detail with well documented experimental data compared. The chevron effects are demonstrated by comparing both solutions using the same mesh resolution and flow conditions. Higher order velocity moments with potential for aeroacoustic modeling and noise prediction, such as the two-point velocity spatial correlations, are also explored. Numerical simulations presented in this study utilize an in-house flow solver with improved parallel scalability and efficiency by means of data packeting and a scheduling algorithm similar to the Round Robin scheduling.

Influence of grid resolution on the spectral characteristics of noise radiated from turbulent jets: Sound pressure fields and their decomposition

“…shown that serration modification to the round nozzle can bring as much as 6 dB reduction in peak noise during take-o↵ with less than 0.5% thrust loss during cruise. Large-eddy simulations [29][30][31][32][33] have revealed the fundamentally di↵erent mechanisms of shear layer growth, with increased mixing caused by the nozzle geometry. Chevrons were also found to reduce the jet and wing/flap interactions [34].…”

Study of an effusion-cooled plate with high level of upstream fluctuation

“…The current study employs an in-house hybrid LES solver for unstructured grid, FLUXp (Flux Limited Unstructured eXtrapolation in parallel) [27][28][29][30][31][32]. In this solver, the Favre-averaged compressible Navier-Stokes equations for ideal gas are solved in conservation form.…”

Research on Thermal-Field and Sound-Field Coupling Properties of Different Grid Forms

“…The airflow sprays out through grids at a relative high speed and makes noise, which is referred to as jet noise [16,17]. Even though the process of generating jet noise is complex, its mechanism and source characteristics can still be analyzed with axisymmetric free jet [18]. Figure 4 shows the structure of axisymmetric free jet with the grid hole diameter to be .…”