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This paper investigates the characteristics of turbine wake which is the major factor determining the turbulence in wind farm and overall wind farm performance. Using the lattice Boltzmann method (LBM) and the large eddy simulation (LES) approach, dynamic simulations of detailed fluid flow and wake trajectory induced by the MEXICO wind turbine were carried out. Moreover, with the help of adaptive mesh refinement (AMR) method, the lattice units were allowed to be automatically refined to allocate more grid points on the solid walls and in the wake region. The simulation results were firstly compared with the experimental data for validation of the numerical model, as well as for investigation of the impact of sub‐grid scale (SGS) turbulence models. Within the present modeling framework, the characteristics of transient wake propagation, detailed flow field, and rotor‐tower interaction were investigated, and the effect of tip‐speed ratio was also analyzed. The present work indicates that, with a suitable SGS turbulence model, the LBM‐LES method is an effective way for dynamic simulations of wake structures induced by a wind turbine with a rotating rotor. [ABSTRACT FROM AUTHOR]

Abrasive flow machining technology is a new type of precision machining technology. Due to its unique rheological properties, it can process any complex structure and size parts to meet the requirements that conventional machining cannot meet. Combined with the turbulent flow characteristics of the abrasive flow, the large eddy simulation numerical method is used to simulate the machining process of the abrasive flow. The influence of different sub-grid scale models on the simulation results is discussed. Taking curved tube as the research object, the static pressure, dynamic pressure and velocity of different sub-grid models are analyzed to find the best sub-grid scale model. Large eddy simulation method is used to simulate the complex flow channel parts, and the best sub-grid scale model suitable for complex flow channels is determined, which reveals the grinding and polishing rule of abrasive flow and provides academic support for future research. Therefore, it has frontier and important research value. [ABSTRACT FROM AUTHOR]

Abstract: Large-eddy simulations (LES) of two plane impinging jets have been conducted. Predictions were first conducted for a natural impinging jet and found to be in good agreement with the experimental data of Yoshida et al. The validated code was then used to study the vortical structures of a forced impinging jet which had been experimentally investigated by Sakakibara et al. The numerical results show that the predictions have clearly captured the spanwise rollers, successive ribs, cross ribs and wall ribs observed by Sakakibara et al. They also show the predicted average convection velocity to be in good agreement with the measured value. Overall, the present study demonstrates the potential of LES simulations as a reliable tool to optimize the performance of engineering systems involving the use of forced impinging jets by regulating cross ribs through the inlet perturbations. [Copyright &y& Elsevier]

• A modified SGS model was proposed to account for the effect of bubble response to turbulent eddies • The modified SGS LES can effectively capture the transient bubbly flow in the bubble column • Both Kolmogorov -5/3 scaling law and -3 scaling law were recovered in LES turbulent kinetic energy spectrum • Strong spatial correlation between the cross-sectional averaged gas hold-up and local vorticity of turbulent eddies The Eulerian–Eulerian Large-eddy simulations (LES) of gas–liquid two-phase flow in a cylindrical bubble column reactor have been conducted. When considering the turbulent eddy viscosity in LES, apart from the well-accepted contributions from shear turbulence and bubble induced turbulence (BIT), the effect of the interaction between entrained bubbles and eddies with a similar turbulence length scale to the sub-grid scale (SGS) cannot be neglected. With the consideration of the bubble response to the eddies on the induced sub-grid stresses, a modified SGS model, which incorporates the Stokes number, St, was proposed. The results of LES clearly indicate that the use of the modified SGS model can effectively capture the transient bubbly flow in the cylindrical bubble column. The power turbulent kinetic energy spectrum obtained in LES indicates that a slope similar to Komogorov -5/3 scaling law and the -3 scaling law can still be identified for a critical frequency f =10.70 Hz. Image, graphical abstract [ABSTRACT FROM AUTHOR]