When the shock wave propagating in the straight circular tube reaches at the open end, the impulsive wave is generated by the emission of a shock wave from an open end, and unsteady pulse jet is formed near the open e...When the shock wave propagating in the straight circular tube reaches at the open end, the impulsive wave is generated by the emission of a shock wave from an open end, and unsteady pulse jet is formed near the open end behind the impulsive wave under the specific condition. The pulse jet transits to spherical shock wave with the increase in the strength of shock wave. The strength is dependent on the Mach number of shock wave, which attenuates by propagation distance from the open end. In this study, the mechanism of generating the unsteady pulse jet, the characteristics of the pressure distribution in the flow field and the emission of shock wave from straight circular tube which has the infinite flange at open end are analyzed numerically by the TVD method. Strength of spherical shock wave, relation of shock wave Mach number,distance decay of spherical shock wave and directional characteristics are clarified.展开更多
In many engineering practices, frequently an impulsive wave is a consequence of discharge of a shockwave from the exit of a tube, leading to an annoying noise like a sonic boom. The impulsive noisehas often been a maj...In many engineering practices, frequently an impulsive wave is a consequence of discharge of a shockwave from the exit of a tube, leading to an annoying noise like a sonic boom. The impulsive noisehas often been a major factor to limit the performance of flow devices as well as to affect hazardousinfluences on human being. The current paper describes a new control method for the reduction ofimpulsive wave. An experiment using a simple shock tube was carried out to examine the effect of acavity/helical vane system on the impulsive wave strength. The resulting impulsive wave was influencedby the detailed configuration of the belieal vane inside the cavity which is located at the vicinity ofthe exit of a tube. The effect of the belieal vane was compared with no belieal vane tests to ensurevalidation of this kind of control strategy. The results showed that the strength of the impulsive wavecould be significantly reduced by the current passive control using the cavity/helical vane system.展开更多
When a Pressure wave propagates along a constant area straight tube and reaches at the open end, an impulsive wave is emitted outward from the tube exit toward the surrounding area and causes an impulsive noise like a...When a Pressure wave propagates along a constant area straight tube and reaches at the open end, an impulsive wave is emitted outward from the tube exit toward the surrounding area and causes an impulsive noise like a sonic boom. In order to clarify the magnitude of an impulsive wave obtained by the discharge of a weak shock wave born an open end of a tube in relation to the noise problem and the industrial devices, the experimental and numerical investigations have been carried out for various strength of a shock wave. A simple open end shock tube with the flange at the tube exit.was used and the numerical calculation using the TVD scheme was performed. The effective equations which concerns with the magnitude of an impulsive wave generated by the emission of a shock wave have been obtained from the procedure of the open end correction based on the aeroacoustic theory and the numerical results. The influence of open end correction length and the diameter of a flange on the magnitude of an impulsive wave has been discussed.展开更多
Based on continuum mechanics and rock dynamics,analyzed the micro-struc- ture damage of rock and the impulsive effect under high pressure water jet and developed the dynamic model.Further,on the assumption of that roc...Based on continuum mechanics and rock dynamics,analyzed the micro-struc- ture damage of rock and the impulsive effect under high pressure water jet and developed the dynamic model.Further,on the assumption of that rock was homogeneous and iso- tropic,a computational model was established based on nonlinear finite element and Arbi- trary Lagrangian-Eulerian(ALE) method.The dynamic effect impacted on rock under high pressure water jet was simulated by the dynamic contact method.The propagation of stress wave in rock was numerically simulated at different impacting velocity.The results show that the propagation velocity of stress wave is proportional to the impacting velocity of high pressure water jet.The faster the impacting velocity is,the quicker the comedown of stress wave.展开更多
The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea...The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea level （ASL）, and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide （a sliding mass volume of 20.7 × 106 m^3） in Zigui County and the Outang dip-slope landslide （a sliding mass volume of about 90 × 106 m^3） in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety （FOS） calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and wa展开更多
文摘When the shock wave propagating in the straight circular tube reaches at the open end, the impulsive wave is generated by the emission of a shock wave from an open end, and unsteady pulse jet is formed near the open end behind the impulsive wave under the specific condition. The pulse jet transits to spherical shock wave with the increase in the strength of shock wave. The strength is dependent on the Mach number of shock wave, which attenuates by propagation distance from the open end. In this study, the mechanism of generating the unsteady pulse jet, the characteristics of the pressure distribution in the flow field and the emission of shock wave from straight circular tube which has the infinite flange at open end are analyzed numerically by the TVD method. Strength of spherical shock wave, relation of shock wave Mach number,distance decay of spherical shock wave and directional characteristics are clarified.
文摘In many engineering practices, frequently an impulsive wave is a consequence of discharge of a shockwave from the exit of a tube, leading to an annoying noise like a sonic boom. The impulsive noisehas often been a major factor to limit the performance of flow devices as well as to affect hazardousinfluences on human being. The current paper describes a new control method for the reduction ofimpulsive wave. An experiment using a simple shock tube was carried out to examine the effect of acavity/helical vane system on the impulsive wave strength. The resulting impulsive wave was influencedby the detailed configuration of the belieal vane inside the cavity which is located at the vicinity ofthe exit of a tube. The effect of the belieal vane was compared with no belieal vane tests to ensurevalidation of this kind of control strategy. The results showed that the strength of the impulsive wavecould be significantly reduced by the current passive control using the cavity/helical vane system.
文摘When a Pressure wave propagates along a constant area straight tube and reaches at the open end, an impulsive wave is emitted outward from the tube exit toward the surrounding area and causes an impulsive noise like a sonic boom. In order to clarify the magnitude of an impulsive wave obtained by the discharge of a weak shock wave born an open end of a tube in relation to the noise problem and the industrial devices, the experimental and numerical investigations have been carried out for various strength of a shock wave. A simple open end shock tube with the flange at the tube exit.was used and the numerical calculation using the TVD scheme was performed. The effective equations which concerns with the magnitude of an impulsive wave generated by the emission of a shock wave have been obtained from the procedure of the open end correction based on the aeroacoustic theory and the numerical results. The influence of open end correction length and the diameter of a flange on the magnitude of an impulsive wave has been discussed.
基金the National Natural Science Foundation of China(5062140)
文摘Based on continuum mechanics and rock dynamics,analyzed the micro-struc- ture damage of rock and the impulsive effect under high pressure water jet and developed the dynamic model.Further,on the assumption of that rock was homogeneous and iso- tropic,a computational model was established based on nonlinear finite element and Arbi- trary Lagrangian-Eulerian(ALE) method.The dynamic effect impacted on rock under high pressure water jet was simulated by the dynamic contact method.The propagation of stress wave in rock was numerically simulated at different impacting velocity.The results show that the propagation velocity of stress wave is proportional to the impacting velocity of high pressure water jet.The faster the impacting velocity is,the quicker the comedown of stress wave.
基金The"Twelfth Five-Year Plan"of the National Science and Technology Support Project(Grant No.2012BAK10B01)the National Natural Science Foundation of China(Grant Nos.41372321 and 41502305)China Geological Survey Projects(Grant No.121201009000150018)
文摘The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea level （ASL）, and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide （a sliding mass volume of 20.7 × 106 m^3） in Zigui County and the Outang dip-slope landslide （a sliding mass volume of about 90 × 106 m^3） in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety （FOS） calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and wa
