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The self-adaptive turbulence eddy simulation (SATES) is employed to investigate the lean premixed methane/air turbulent flame in a single-nozzle model gas turbine combustor, in which the high axial momentum jet issuing from an off-center nozzle facilitates the development of a large-scale, dominant lateral recirculation zone that stabilizes the flame. For turbulence modeling, the SATES method can dynamically adjust the proportion of resolving and modeling of turbulent scales according to the local grid scale and turbulence length scales, thus depressing the gird-sensitivity in large eddy simulation (LES) calculation. For combustion modeling, the thickened flame model with a reduced chemistry mechanism is integrated into the SATES turbulence modeling framework to capture the unsteady flame dynamics. The accuracy of SATES results is assessed against experimental data, as well as the ones from LES and the detached eddy simulation (DES) of this burner with the same combustion model and grids. The predicted length of large-scale recirculation of the flow field by SATES is significantly better than that by LES and DES with low mesh resolution. Detailed comparisons show that the SATES adaptively improves the modeling degree of near-wall turbulence to improve the prediction accuracy with the low grid resolution. Similar to LES, the SATES method does not cause serious delay of shear layer instability and weakening of flame wrinkle observed in DES. The study demonstrates the suitability and accuracy of the hybrid turbulence modeling methods of SATES for complex turbulent flame simulations coupled with suitable combustion model. [ABSTRACT FROM AUTHOR]

The flow over a flat plate at a Reynolds number of 750 is numerically investigated via fine large-eddy simulation (LES), first at normal ($90\textdegree $) and then at oblique ($45\textdegree $) incidence flow direction with a uniform steady inlet. The results are in complete agreement with the direct numerical simulation (DNS) and experimental data, thereby serving as a validation for the present simulations. For the normal ($90\textdegree $) uniform inflow case, coherent vortices are alternately shed from both leading edges of the plate, whereas for the oblique ($45\textdegree $) uniform inflow case the vortices shed from the two sides of the plate interact strongly resulting in a quasi-periodic force response. The normal flat plate is then analysed with an incident gust signal with varying amplitude and time period. For these incident coherent gust cases, a reference test case with variable coherent inlet is first studied and the results are compared to a steady inlet simulation, with a detailed analysis of the flow behaviour and the wake response under the incident gust. Finally, the flat plate response to 16 different gust profiles is studied. A transient drag reconstruction for these incident coherent gust cases is then presented based on a frequency-dependent transfer function and phase spectrum analysis. [ABSTRACT FROM PUBLISHER]

In the present study, a detailed assessment investigation of Very-Large Eddy Simulation (VLES) method is performed using the open-source toolbox OpenFOAM for the simulation of turbulent separated flow. The VLES method is a unified simulation approach enabling a seamless evolution from Reynolds-Averaged Navier-Stokes (RANS) to quasi Direct Numerical Simulation (quasi-DNS) depending on the numerical resolution. Two VLES models, i.e. VLES-k-ε and VLES-k-ω , are implemented in OpenFOAM and applied in the present study. In order to assess the performance of VLES models based on the framework of OpenFOAM, four classic separated flow are selected and investigated in details, including the flow past a triangular bluff body at Re ​= ​45,000, the flow past a backward facing step at Re ​= ​40,000, the periodic hill flow at Re ​= ​10,595, and the flow past a circular cylinder at Re ​= ​41,300. The comparisons between VLES simulation results and experiments give an indication on the adequacy and accuracy of the VLES modelling method based on the OpenFOAM toolbox. The VLES-k-ω model performs slightly better than the VLES-k-ε model on a relatively low mesh resolution, especially in predicting the turbulent separation flow induced by the pressure gradient on a smooth surface. The results also demonstrate the reliability and accuracy of the VLES modelling based on OpenFOAM platform for complex separated flow simulations. • Recently developed VLES turbulence models are implemented into OpenFOAM. • VLES calculations are performed for four cases of turbulent separated flow. • The VLES is found to be only slightly sensitive to computational mesh. • The OpenFOAM can provide a good platform for VLES calculation of complex turbulent flow. [ABSTRACT FROM AUTHOR]

Film cooling is an important cooling method to protect the hot components in aero-engines and it is a classical research topic for decades. However, accurate simulation of the film cooling is still challenging. The present study aims to study film cooling with a newly developed Very-Large Eddy Simulation (VLES) method. State-of-the-art turbulence modelling methods are also included for comprehensive comparisons of film cooling simulations, i.e., VLES and DES (Detached Eddy Simulation) of hybrid RANS-LES method and the classical LES (Large Eddy Simulation) method are applied. Numerical simulations are performed for a single row film cooling benchmark test case (Sinha et al., 1991), in which the turbulence intensity of the freestream flow is about 0.2%, at two density ratios and two blowing ratios, corresponding to four momentum flux ratios. The results predicted by different turbulence methods are compared in detail, including the film cooling effectiveness, the velocity flow fields, as well as the relevant turbulent flow structures. The predicted results are also compared with available experimental data. It is found that for the three cases with low momentum flux ratios (smaller than 0.3), the three turbulence methods produce quite different results, while for the case with higher momentum flux ratio of 0.5, the differences between the results of three turbulence methods become less significant. Overall, the present VLES method performs best among the three selected methods, and its predictions agree well with the experimental data. While for the DES method, it severely delays the Kelvin-Helmholtz instability of the turbulence mixing process in film cooling and thus fails to accurately predict the cooling effectiveness at low momentum flux ratio. The study demonstrates the potentials of the newly developed VLES method for accurate prediction of complex film cooling problems. • Present VLES method has good accuracy for complex film cooling heat transfer simulation. • Present VLES method performs better than DES to capture unsteady mixing process. • Unsteady 3D vortex structures play an important role for film cooling heat transfer. • Accurate simulation of film cooling is challenging for turbulence modelling. [ABSTRACT FROM AUTHOR]