An idealized numerical wave flume has been established by finite element method on the bases of Navier Stokes equations through prescribing the appropriate boundary conditions for the open boundary,incident boundary,...An idealized numerical wave flume has been established by finite element method on the bases of Navier Stokes equations through prescribing the appropriate boundary conditions for the open boundary,incident boundary,free surface and solid boundary in this paper.The characteristics of waves propagating over a step have been investigated by this numerical model.The breaker wave height is determined depending on the kinetic criterion.The numerical model is verified by laboratory experiments,and the empirical formula for the damping of wave height due to breaking is also given by experiments.展开更多
The mechanism and the design parameters of blasting with air-decking are studied. The theory of detonation waves is used to investigate the processes of the one-dimensional plane detonation wave within a borehole. The...The mechanism and the design parameters of blasting with air-decking are studied. The theory of detonation waves is used to investigate the processes of the one-dimensional plane detonation wave within a borehole. The interac- tion of the rarefaction wave with an interface and reflection on a rigid wall is also analyzed. The same courses of the shock wave are also investigated. This decides the distribution of the pressure of the explosion products changing with time along the borehole. Based on the above theoretical analysis, two conditions should be met for a reasonable range of values of the air-decking ratio in blasting rock. First, the rarefaction wave from the contact interface between detonation products and air reaches the bottom earlier than that of the reflected shock wave from the end of the stemming. Second, the reflected shock wave reaches the contact interface between the detonation products and air earlier than that of the reflected rarefaction wave from the bottom of the borehole. Finally, the reasonable value of the air-decking ratio must be decided theoretically in air-decking blasting. For different explosives, the reasonable range of air-decking ratio varies from 0.15 to 0.4. This result is well consistent with what was obtained by previous researchers.展开更多
We propose a scheme to simultaneously widen and heighten the high-order harmonic plateau on a large scale. More specifically, by adopting a united two-atom system with a suitable inter-nuclear separation instead of a ...We propose a scheme to simultaneously widen and heighten the high-order harmonic plateau on a large scale. More specifically, by adopting a united two-atom system with a suitable inter-nuclear separation instead of a single-atom, the harmonic plateau is widened from Ip ＋ 3.2Up to Ip ＋8.5Up; further, by adopting the combined pulse, the extended plateau （harmonics near Ip＋ 5.6Up） is selectively heightened in excess of 4 orders of magnitude compared with the case of the low-frequency pulse alone. By means of the wavelet transform for the induced dipole of these harmonics, a single x-ray pulse as short as 210 asec is achieved.展开更多
To understand the processes and energy dissipation performance caused by turbulence during the wave run-up over a stepped revetment,hydraulic model tests with steady flow conditions are conducted and correlated with u...To understand the processes and energy dissipation performance caused by turbulence during the wave run-up over a stepped revetment,hydraulic model tests with steady flow conditions are conducted and correlated with unsteady flow conditions of the wave run-up within a short time frame.Under irregular waves,the run-up reduction over a stepped revetment is dependent on the Iribarren number and decreases for decreasing Iribarren numbers.Velocity gradients are found to be similar in a steady and unsteady flow regime near the pseudo-bottom.展开更多
文摘An idealized numerical wave flume has been established by finite element method on the bases of Navier Stokes equations through prescribing the appropriate boundary conditions for the open boundary,incident boundary,free surface and solid boundary in this paper.The characteristics of waves propagating over a step have been investigated by this numerical model.The breaker wave height is determined depending on the kinetic criterion.The numerical model is verified by laboratory experiments,and the empirical formula for the damping of wave height due to breaking is also given by experiments.
文摘The mechanism and the design parameters of blasting with air-decking are studied. The theory of detonation waves is used to investigate the processes of the one-dimensional plane detonation wave within a borehole. The interac- tion of the rarefaction wave with an interface and reflection on a rigid wall is also analyzed. The same courses of the shock wave are also investigated. This decides the distribution of the pressure of the explosion products changing with time along the borehole. Based on the above theoretical analysis, two conditions should be met for a reasonable range of values of the air-decking ratio in blasting rock. First, the rarefaction wave from the contact interface between detonation products and air reaches the bottom earlier than that of the reflected shock wave from the end of the stemming. Second, the reflected shock wave reaches the contact interface between the detonation products and air earlier than that of the reflected rarefaction wave from the bottom of the borehole. Finally, the reasonable value of the air-decking ratio must be decided theoretically in air-decking blasting. For different explosives, the reasonable range of air-decking ratio varies from 0.15 to 0.4. This result is well consistent with what was obtained by previous researchers.
基金Supported by the National Natural Science Foundation of China under Grant No. 10474028
文摘We propose a scheme to simultaneously widen and heighten the high-order harmonic plateau on a large scale. More specifically, by adopting a united two-atom system with a suitable inter-nuclear separation instead of a single-atom, the harmonic plateau is widened from Ip ＋ 3.2Up to Ip ＋8.5Up; further, by adopting the combined pulse, the extended plateau （harmonics near Ip＋ 5.6Up） is selectively heightened in excess of 4 orders of magnitude compared with the case of the low-frequency pulse alone. By means of the wavelet transform for the induced dipole of these harmonics, a single x-ray pulse as short as 210 asec is achieved.
基金part of the joint research project ‘wave STEPS’ funded by the German Federal Ministry of Education and Research(BMBF) through the German Coastal Engineering Research council(KFKI,03KIS108 and 03KIS119)
文摘To understand the processes and energy dissipation performance caused by turbulence during the wave run-up over a stepped revetment,hydraulic model tests with steady flow conditions are conducted and correlated with unsteady flow conditions of the wave run-up within a short time frame.Under irregular waves,the run-up reduction over a stepped revetment is dependent on the Iribarren number and decreases for decreasing Iribarren numbers.Velocity gradients are found to be similar in a steady and unsteady flow regime near the pseudo-bottom.
