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
Existing studies about wind pressure on agricultural greenhouse buildings concentrate on the mean wind pressure while ignoring the systematic research on fluctuating wind pressure characteristics and the influence of ...Existing studies about wind pressure on agricultural greenhouse buildings concentrate on the mean wind pressure while ignoring the systematic research on fluctuating wind pressure characteristics and the influence of roof shape on the wind pressure characteristics,which are closely associated with the wind-induced damage mecha-nism.In this study,two typical agricultural greenhouse buildings on tropical islands are selected as prototypes to conduct pressure measurement experiments in the wind tunnel.Based on the wind pressure time series for the two greenhouses,the mean and fluctuating wind pressure distribution pattern and the localized high-pressure generation mechanism are analyzed.Then,the shape coefficient of the two green-houses is compared in depth to the standards from four countries.Besides,wind pressure non-Gaussian determination criteria for agricultural greenhouse buildings considering the roof shape and wind directions are proposed.Lastly,the differences in wind pressure spectra on the roofs and walls of the two greenhouses are sum-marized.The results indicate the roof shape has a significant influence on the wind pressure characteristics.Compared with the pitched roof,the vaulted roof will increase the suction effect on the windward front zone and the middle area,mitigate the suc-tion impact on the leeward roof,and weaken the wind pressure non-Gaussian charac-teristics.The experimental shape coefficient of the pitched-roof greenhouse is basically consistent with the standard from the U.S.,while that of the vaulted-roof greenhouse has some deviation from the existing standards.The results provide a theoretical basis for the wind-resistant design of agricultural greenhouse buildings on tropical islands.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This research was supported by the National Natural Science Foundation of China(52068019)the Hainan Provincial Natural Science Foundation of China(522RC605,520QN231 and 521RC502).
文摘Existing studies about wind pressure on agricultural greenhouse buildings concentrate on the mean wind pressure while ignoring the systematic research on fluctuating wind pressure characteristics and the influence of roof shape on the wind pressure characteristics,which are closely associated with the wind-induced damage mecha-nism.In this study,two typical agricultural greenhouse buildings on tropical islands are selected as prototypes to conduct pressure measurement experiments in the wind tunnel.Based on the wind pressure time series for the two greenhouses,the mean and fluctuating wind pressure distribution pattern and the localized high-pressure generation mechanism are analyzed.Then,the shape coefficient of the two green-houses is compared in depth to the standards from four countries.Besides,wind pressure non-Gaussian determination criteria for agricultural greenhouse buildings considering the roof shape and wind directions are proposed.Lastly,the differences in wind pressure spectra on the roofs and walls of the two greenhouses are sum-marized.The results indicate the roof shape has a significant influence on the wind pressure characteristics.Compared with the pitched roof,the vaulted roof will increase the suction effect on the windward front zone and the middle area,mitigate the suc-tion impact on the leeward roof,and weaken the wind pressure non-Gaussian charac-teristics.The experimental shape coefficient of the pitched-roof greenhouse is basically consistent with the standard from the U.S.,while that of the vaulted-roof greenhouse has some deviation from the existing standards.The results provide a theoretical basis for the wind-resistant design of agricultural greenhouse buildings on tropical islands.
