The accurate simulation of turbulence and the implementation of corresponding turbulence models are both critical to the understanding of the complex physics behind turbulent flows in a variety of science and engineer...The accurate simulation of turbulence and the implementation of corresponding turbulence models are both critical to the understanding of the complex physics behind turbulent flows in a variety of science and engineering applications.Despite the tremendous increase in the computing power of central processing units(CPUs),direct numerical simulation of highly turbulent flows is still not feasible due to the need for resolving the smallest length scale,and today’s CPUs cannot keep pace with demand.The recent development of graphics processing units(GPU)has led to the general improvement in the performance of various algorithms.This study investigates the applicability of GPU technology in the context of fast-Fourier transform(FFT)-based pseudo-spectral methods for DNS of turbulent flows for the Taylor–Green vortex problem.They are implemented on a single GPU and a speedup of unto 31x is obtained in comparison to a single CPU.展开更多
An upwind finite-difference procedure was employed to predict the development of turbulence in shear flow with a two-equation turbulence k-Ε model. An experimental device was used to demonstrate turbulent phenomena. ...An upwind finite-difference procedure was employed to predict the development of turbulence in shear flow with a two-equation turbulence k-Ε model. An experimental device was used to demonstrate turbulent phenomena. The predicted velocity contours of shear flow were presented and compared with experimental measurement. The predictive and experimental results show that when velocity ratio between upper flow and lower flow is greater than 9, large scale vortex pair appears and fully developed turbulence occurs.展开更多
旋流沉砂池内高浓度砂石废水的大涡模拟研究,不仅可以揭示旋流沉砂池内复杂流态的瞬时演变,而且能够实现水电工程砂石系统生产废水的达标处理,具有重要的理论与环保意义。该文采用分子动理学方法,从颗粒间相互作用的微观特性角度出发,...旋流沉砂池内高浓度砂石废水的大涡模拟研究,不仅可以揭示旋流沉砂池内复杂流态的瞬时演变,而且能够实现水电工程砂石系统生产废水的达标处理,具有重要的理论与环保意义。该文采用分子动理学方法,从颗粒间相互作用的微观特性角度出发,得到了合理描述高浓度下颗粒间碰撞项的耦合VOF(Volume of Fluid)法的LES-Lagrangian高浓度气-液-固多相流大涡数学模型,亚格子应力采用Smagorinsky亚格子模型封闭,并运用滑移网格技术实现旋流沉砂池内桨叶转动区域的模拟。对西南某水电工程砂石废水处理小试试验的二级旋流沉砂池内湍流场瞬时变化进行了精细模拟;实现了对旋流沉砂池的自由液面以及砂石颗粒运动轨迹的追踪;并讨论了搅拌桨转速对旋流沉砂池内水相、颗粒相的影响,得出旋流沉砂池的最佳桨叶转速为30r/min。同时,将大涡模拟与雷诺时均紊流模型进行了比较,表明大涡模拟可以揭示更为精细的湍流涡结构演变。展开更多
文摘The accurate simulation of turbulence and the implementation of corresponding turbulence models are both critical to the understanding of the complex physics behind turbulent flows in a variety of science and engineering applications.Despite the tremendous increase in the computing power of central processing units(CPUs),direct numerical simulation of highly turbulent flows is still not feasible due to the need for resolving the smallest length scale,and today’s CPUs cannot keep pace with demand.The recent development of graphics processing units(GPU)has led to the general improvement in the performance of various algorithms.This study investigates the applicability of GPU technology in the context of fast-Fourier transform(FFT)-based pseudo-spectral methods for DNS of turbulent flows for the Taylor–Green vortex problem.They are implemented on a single GPU and a speedup of unto 31x is obtained in comparison to a single CPU.
文摘An upwind finite-difference procedure was employed to predict the development of turbulence in shear flow with a two-equation turbulence k-Ε model. An experimental device was used to demonstrate turbulent phenomena. The predicted velocity contours of shear flow were presented and compared with experimental measurement. The predictive and experimental results show that when velocity ratio between upper flow and lower flow is greater than 9, large scale vortex pair appears and fully developed turbulence occurs.
文摘旋流沉砂池内高浓度砂石废水的大涡模拟研究,不仅可以揭示旋流沉砂池内复杂流态的瞬时演变,而且能够实现水电工程砂石系统生产废水的达标处理,具有重要的理论与环保意义。该文采用分子动理学方法,从颗粒间相互作用的微观特性角度出发,得到了合理描述高浓度下颗粒间碰撞项的耦合VOF(Volume of Fluid)法的LES-Lagrangian高浓度气-液-固多相流大涡数学模型,亚格子应力采用Smagorinsky亚格子模型封闭,并运用滑移网格技术实现旋流沉砂池内桨叶转动区域的模拟。对西南某水电工程砂石废水处理小试试验的二级旋流沉砂池内湍流场瞬时变化进行了精细模拟;实现了对旋流沉砂池的自由液面以及砂石颗粒运动轨迹的追踪;并讨论了搅拌桨转速对旋流沉砂池内水相、颗粒相的影响,得出旋流沉砂池的最佳桨叶转速为30r/min。同时,将大涡模拟与雷诺时均紊流模型进行了比较,表明大涡模拟可以揭示更为精细的湍流涡结构演变。
