To investigate the energy partition in laser-induced cavitation bubbles near the rigid wall with a gas-containing hole,we utilized a nanosecond resolution photography system based on a Q-switched Nd:YAG laser and conv...To investigate the energy partition in laser-induced cavitation bubbles near the rigid wall with a gas-containing hole,we utilized a nanosecond resolution photography system based on a Q-switched Nd:YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse near the rigid wall with a gas-containing hole.We analyzed the generation of collapse microjets and the emission of collapse shock waves.We found that the cavitation bubble near the rigid wall with a gas-containing hole collapsed at different times and space,and produced various types of shock waves.Based on the far field pressure information of the shock waves measured by hydrophone,the energy of the shock waves generated by the bubble collapse near the rigid wall with a gas-containing hole is calculated for the first time.The results show that the ratio of collapse shock wave energy to bubble energy is approximately between 0.7 and 0.8.展开更多
The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affec...The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affect the direction of the microjet.The motive of this study is to find out the influence of the dynamic behavior of a laser-induced bubble near the rigid wall with a gas-containing hole.Evolutions of the bubble at different distances from the gas-containing hole in the horizontal and vertical directions were recorded by a high-speed camera(2.3×10^(5) fps).When the bubble collapse near the boundary,the bubble will produce two situations:away from or toward the boundary.It focuses on the direction of the bubble,the oscillation period of a bubble,and reflection angle,and quantitative analysis of the results.It was found that the boundary not only changes the morphologic of the bubble and the overall direction of movement but also affects the oscillation period.In addition,it can control the deflection of the bubble.展开更多
Research on coal fragmentation can play an important role in understanding coal and gas outbursts.The study discussed in this paper explored the fragmentation of gas-containing coal particles using the drop-weight imp...Research on coal fragmentation can play an important role in understanding coal and gas outbursts.The study discussed in this paper explored the fragmentation of gas-containing coal particles using the drop-weight impact method.The effects of equilibrium gas pressures and type of adsorbate gas on particle size distributions and fragmentation energy were investigated in detail.We found that the Fractal particle size distribution model can most effectively describe the crushed coal particle sizes.The equilibrium pressure and type of gas can influence the Fractal distribution parameter.The crushing energy is composed of energy to create new surfaces and other forms of energy that are dissipated but the equilibrium gas pressure and type of adsorption gas can affect energy consumption and crushing efficiency.This research will be of guiding significance to the intensity evaluation and mechanism understanding of coal and gas outbursts.展开更多
A creep experiment of preformed molding coal under different confining pressures were carried out using self-developed 3-triaxial creep loading device for gas-containing coal, which loaded by Shimadzu AGI-250 kN elect...A creep experiment of preformed molding coal under different confining pressures were carried out using self-developed 3-triaxial creep loading device for gas-containing coal, which loaded by Shimadzu AGI-250 kN electrical servo-controlled stiffness testing machine. Based on the experimental results, the variation trend of axial deformation under different stress states was studied, and creep failure characteristics of gas-containing coal under different confining pressures were analyzed. The experimental results were identified with seven-component nonlinear viscoelasto-plastic creep model （Hohai model）, and the creep material parameters were obtained. The experimental result complies well with the theoretical value of this model. It indicates that creep constitutive relation of gas-containing coal can be expressed by nonlinear viscoelasto-plastic creep model correctly.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52179092,52222904).
文摘To investigate the energy partition in laser-induced cavitation bubbles near the rigid wall with a gas-containing hole,we utilized a nanosecond resolution photography system based on a Q-switched Nd:YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse near the rigid wall with a gas-containing hole.We analyzed the generation of collapse microjets and the emission of collapse shock waves.We found that the cavitation bubble near the rigid wall with a gas-containing hole collapsed at different times and space,and produced various types of shock waves.Based on the far field pressure information of the shock waves measured by hydrophone,the energy of the shock waves generated by the bubble collapse near the rigid wall with a gas-containing hole is calculated for the first time.The results show that the ratio of collapse shock wave energy to bubble energy is approximately between 0.7 and 0.8.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91852101,91952301,52179092 and 52179081).
文摘The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affect the direction of the microjet.The motive of this study is to find out the influence of the dynamic behavior of a laser-induced bubble near the rigid wall with a gas-containing hole.Evolutions of the bubble at different distances from the gas-containing hole in the horizontal and vertical directions were recorded by a high-speed camera(2.3×10^(5) fps).When the bubble collapse near the boundary,the bubble will produce two situations:away from or toward the boundary.It focuses on the direction of the bubble,the oscillation period of a bubble,and reflection angle,and quantitative analysis of the results.It was found that the boundary not only changes the morphologic of the bubble and the overall direction of movement but also affects the oscillation period.In addition,it can control the deflection of the bubble.
基金support from the Science and Technology Foundation of Guizhou Province(No.[2017]2815)the Fundamental Research Funds for the Central Universities(No.2020YJSAQ05)the National Natural Science Foundation of China(Nos.51274206,51404277)。
文摘Research on coal fragmentation can play an important role in understanding coal and gas outbursts.The study discussed in this paper explored the fragmentation of gas-containing coal particles using the drop-weight impact method.The effects of equilibrium gas pressures and type of adsorbate gas on particle size distributions and fragmentation energy were investigated in detail.We found that the Fractal particle size distribution model can most effectively describe the crushed coal particle sizes.The equilibrium pressure and type of gas can influence the Fractal distribution parameter.The crushing energy is composed of energy to create new surfaces and other forms of energy that are dissipated but the equilibrium gas pressure and type of adsorption gas can affect energy consumption and crushing efficiency.This research will be of guiding significance to the intensity evaluation and mechanism understanding of coal and gas outbursts.
基金National Basic Research Program of China （973 program）（2005CB221502） National Natural Science Foundation of China（50534080） National Natural Science Foundation of China（50604021 ）
文摘A creep experiment of preformed molding coal under different confining pressures were carried out using self-developed 3-triaxial creep loading device for gas-containing coal, which loaded by Shimadzu AGI-250 kN electrical servo-controlled stiffness testing machine. Based on the experimental results, the variation trend of axial deformation under different stress states was studied, and creep failure characteristics of gas-containing coal under different confining pressures were analyzed. The experimental results were identified with seven-component nonlinear viscoelasto-plastic creep model （Hohai model）, and the creep material parameters were obtained. The experimental result complies well with the theoretical value of this model. It indicates that creep constitutive relation of gas-containing coal can be expressed by nonlinear viscoelasto-plastic creep model correctly.
