A level set method of non-uniform grids is used to simulate the whole evolution of a cavitation bubble, including its growth, collapse and rebound near a rigid wall. Single-phase Navier-Stokes equation in the liquid r...A level set method of non-uniform grids is used to simulate the whole evolution of a cavitation bubble, including its growth, collapse and rebound near a rigid wall. Single-phase Navier-Stokes equation in the liquid region is solved by MAC projection algorithm combined with second-order ENO scheme for the advection terms. The moving inter-face is captured by the level set function, and the interface velocity is resolved by ＂one-side＂ velocity extension from the liquid region to the bubble region, complementing the second-order weighted least squares method across the interface and projection inside bubble. The use of non-uniform grid overcomes the difficulty caused by the large computational domain and very small bubble size. The computation is very stable without suffering from large flow-field gradients, and the results are in good agreements with other studies. The bubble interface kinematics, dynamics and its effect on the wall are highlighted, which shows that the code can effectively capture the ＂shock wave＂-like pressure and velocity at jet impact, toroidal bubble, and complicated pressure structure with peak, plateau and valley in the later stage of bubble oscillating.展开更多
粒子浆液射流破岩过程涉及大变形、高应变及强载荷,表现为钢粒-浆液-岩石之间非线性动态耦合问题。针对岩石损伤瞬时多变性及观测困难等问题,开展了粒子与浆液射流冲击下岩石的动态损伤机理及破坏效应研究。首先,基于光滑粒子动力学-有...粒子浆液射流破岩过程涉及大变形、高应变及强载荷,表现为钢粒-浆液-岩石之间非线性动态耦合问题。针对岩石损伤瞬时多变性及观测困难等问题,开展了粒子与浆液射流冲击下岩石的动态损伤机理及破坏效应研究。首先,基于光滑粒子动力学-有限元模拟(smoothed particle hydrodynamics-finite element method,SPH-FEM)耦合算法描述了粒子-浆液冲击破岩的建模方法;然后,结合JH-Ⅱ(Johnson-Holmquist-Ⅱ)模型与Rankine拉伸断裂软化模型建立了岩石损伤本构模型,对粒子浆液射流冲击破岩过程及损伤机理进行了动态模拟。研究结果表明:岩石的损伤破坏主要以纵向扩展为主,具有瞬时性与阶跃性特征,呈现出“从累积损伤到不断破坏”的循环过程;岩石破坏机理以剪切破碎和拉伸裂纹为主。同时,通过试验和数值模拟对比验证了破岩样本的形态,并分析了冲击速度、角度与粒子尺寸对破岩效应的影响规律。研究结果对于粒子浆液冲击钻井破岩理论的发展具有重要意义。展开更多
基金the National Natural Science Foundation of China(10272032 and 10672043).
文摘A level set method of non-uniform grids is used to simulate the whole evolution of a cavitation bubble, including its growth, collapse and rebound near a rigid wall. Single-phase Navier-Stokes equation in the liquid region is solved by MAC projection algorithm combined with second-order ENO scheme for the advection terms. The moving inter-face is captured by the level set function, and the interface velocity is resolved by ＂one-side＂ velocity extension from the liquid region to the bubble region, complementing the second-order weighted least squares method across the interface and projection inside bubble. The use of non-uniform grid overcomes the difficulty caused by the large computational domain and very small bubble size. The computation is very stable without suffering from large flow-field gradients, and the results are in good agreements with other studies. The bubble interface kinematics, dynamics and its effect on the wall are highlighted, which shows that the code can effectively capture the ＂shock wave＂-like pressure and velocity at jet impact, toroidal bubble, and complicated pressure structure with peak, plateau and valley in the later stage of bubble oscillating.
文摘粒子浆液射流破岩过程涉及大变形、高应变及强载荷,表现为钢粒-浆液-岩石之间非线性动态耦合问题。针对岩石损伤瞬时多变性及观测困难等问题,开展了粒子与浆液射流冲击下岩石的动态损伤机理及破坏效应研究。首先,基于光滑粒子动力学-有限元模拟(smoothed particle hydrodynamics-finite element method,SPH-FEM)耦合算法描述了粒子-浆液冲击破岩的建模方法;然后,结合JH-Ⅱ(Johnson-Holmquist-Ⅱ)模型与Rankine拉伸断裂软化模型建立了岩石损伤本构模型,对粒子浆液射流冲击破岩过程及损伤机理进行了动态模拟。研究结果表明:岩石的损伤破坏主要以纵向扩展为主,具有瞬时性与阶跃性特征,呈现出“从累积损伤到不断破坏”的循环过程;岩石破坏机理以剪切破碎和拉伸裂纹为主。同时,通过试验和数值模拟对比验证了破岩样本的形态,并分析了冲击速度、角度与粒子尺寸对破岩效应的影响规律。研究结果对于粒子浆液冲击钻井破岩理论的发展具有重要意义。
