The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift f...The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift force and overturning moment with different wind speeds and wall heights were calculated. According to the principle of static moment balance of vehicles, the overturning coefficients of trains with different wind speeds and wall heights were obtained. Based on the influence of wind speed and wall height on the aerodynamic performance and the overturning stability of trains, a method of determination of the load balance ranges for the train operation safety was proposed, which made the overturning coefficient have nearly closed interval. A min(|A1|+|A2|), s.t. |A1|→|A2|(A1 refers to the downwind overturning coefficient and A2 refers to the upwind overturning coefficient)was found. This minimum value helps to lower the wall height as much as possible, and meanwhile, guarantees the operation safety of various types of trains under strong wind. This method has been used for the construction and improvement of the windbreak walls along the Lanzhou–Xinjiang railway(from Lanzhou to Urumqi, China).展开更多
The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for n...The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for non-stationary strong wind fields is first presented. Non-stationary wind forces induced by strong winds on bridge deck and tower are then given a brief introduction. Finally,Non-stationary buffeting response of Pulite Bridge in China,a long span suspension bridge,is computed by using ANSYS software under four working conditions with different combination of time-varying mean wind and time-varying variance. The case study further confirms that it is necessity of considering non-stationary buffeting response for long span suspension bridge under strong wind loading,rather than only stationary buffeting response.展开更多
During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading ...During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order tofigure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of full-scale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO_(2) bubble:4 and 14;cycle number for the occurrence of continuous CO_(2) bubble:5 and 15;alternating thermal load:30-120℃ and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.展开更多
The impact of strong wind and rain loads will adversely affect the reliability of the overhead lines, it’s necessary to study changes in risk of transmission system and establish the reliability model of overhead lin...The impact of strong wind and rain loads will adversely affect the reliability of the overhead lines, it’s necessary to study changes in risk of transmission system and establish the reliability model of overhead lines through the strong wind and rain loads. In this article, the stochastic properties of overhead lines’ strength and loads were used, according to principles of structural reliability, time-dependent failure probability model of overhead lines was established under the impact of strong wind and rain loads. Simulation of the IEEE-79 system demonstrates that failure probability model is effective. This simulation result also shows that the impact of strong wind and rain loads will seriously affect reliability indices of system loads, rain loads cannot be ignored under strong wind and rain loads.展开更多
基金Project(U1334203) supported by the National Natural Science Foundation of China
文摘The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift force and overturning moment with different wind speeds and wall heights were calculated. According to the principle of static moment balance of vehicles, the overturning coefficients of trains with different wind speeds and wall heights were obtained. Based on the influence of wind speed and wall height on the aerodynamic performance and the overturning stability of trains, a method of determination of the load balance ranges for the train operation safety was proposed, which made the overturning coefficient have nearly closed interval. A min(|A1|+|A2|), s.t. |A1|→|A2|(A1 refers to the downwind overturning coefficient and A2 refers to the upwind overturning coefficient)was found. This minimum value helps to lower the wall height as much as possible, and meanwhile, guarantees the operation safety of various types of trains under strong wind. This method has been used for the construction and improvement of the windbreak walls along the Lanzhou–Xinjiang railway(from Lanzhou to Urumqi, China).
基金Sponsored by the National Natural Science Foundation of China(Grant No.51408174)Anhui Provincial Natural Science Foundation(Grant No.1408085QE95)+1 种基金China Postdoctoral Science Foundation(Grant No.2013M540511 and 2015T80652)Key University Science Research Project of Anhui Province(Grant No.KJ2016A294)
文摘The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for non-stationary strong wind fields is first presented. Non-stationary wind forces induced by strong winds on bridge deck and tower are then given a brief introduction. Finally,Non-stationary buffeting response of Pulite Bridge in China,a long span suspension bridge,is computed by using ANSYS software under four working conditions with different combination of time-varying mean wind and time-varying variance. The case study further confirms that it is necessity of considering non-stationary buffeting response for long span suspension bridge under strong wind loading,rather than only stationary buffeting response.
基金Project supported by the National Natural Science Foundation of China“Study on Casing-Cement Sheath-Formation Integrity under Alternating Temperature,Pressure and Their Coupling Effects”(No.:51904261)China Postdoctoral Science Foundation(No.:2019M653478)。
文摘During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order tofigure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of full-scale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO_(2) bubble:4 and 14;cycle number for the occurrence of continuous CO_(2) bubble:5 and 15;alternating thermal load:30-120℃ and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.
文摘The impact of strong wind and rain loads will adversely affect the reliability of the overhead lines, it’s necessary to study changes in risk of transmission system and establish the reliability model of overhead lines through the strong wind and rain loads. In this article, the stochastic properties of overhead lines’ strength and loads were used, according to principles of structural reliability, time-dependent failure probability model of overhead lines was established under the impact of strong wind and rain loads. Simulation of the IEEE-79 system demonstrates that failure probability model is effective. This simulation result also shows that the impact of strong wind and rain loads will seriously affect reliability indices of system loads, rain loads cannot be ignored under strong wind and rain loads.
