本文利用新一代中尺度数值天气模式Weather Research and Forecasting Model(v3.1.1,WRFV3)、日本气象厅20 km分析资料及自动站观测数据等模拟了2008年8月25日上海一次特大暴雨过程,并研究了城市化对这次暴雨过程的影响.研究结果表明:WR...本文利用新一代中尺度数值天气模式Weather Research and Forecasting Model(v3.1.1,WRFV3)、日本气象厅20 km分析资料及自动站观测数据等模拟了2008年8月25日上海一次特大暴雨过程,并研究了城市化对这次暴雨过程的影响.研究结果表明:WRFV3模式能够较好地模拟出上海0825暴雨的主要分布特征,强降水中心以及暴雨随时间变化趋势;上海城市化使得这次暴雨过程在城市中心区域和迎风区降雨增强,城市背风区降雨减少;而城市化引起的陆面粗糙度等变化的动力作用对城市地区低层风场产生阻挡,使得城市迎风区垂直上升运动增强、水汽增多,是造成城市迎风区降雨增强的主要原因.展开更多
Theoretical analysis and wind tunnel tests were carried out to study wind-induced intemal pressure response for the structure with single windward opening and background leakage. Its goveming differential equation was...Theoretical analysis and wind tunnel tests were carried out to study wind-induced intemal pressure response for the structure with single windward opening and background leakage. Its goveming differential equation was derived by the Bemoulli equation in an unsteady-isentropic form. Numerical examples were provided to study the additive damping caused by background leakage in laminar and turbulent flow, and the influence of background leakage on fluctuating internal pressure response was quantized. A series of models for low-rise building with various opening ratios and background leakage were designed and wind tunnel tests were conducted. It is shown that the fluctuating intemal pressure reduces when the background leakage are considered and that the effect of background leakage can be predicted accurately by the governing differential equation deduced in this paper.展开更多
A frequency domain method for estimating wind-induced fluctuating internal pressure of structure with single windward opening is presented in this paper and wind tunnel tests were carried out to verify the theory. The...A frequency domain method for estimating wind-induced fluctuating internal pressure of structure with single windward opening is presented in this paper and wind tunnel tests were carried out to verify the theory. The nonlinear differential equation of internal pressure dynamics and iteration algorithm were applied to calculate fluctuating internal pressure and time domain analysis was used to verify the accuracy of the proposed method. A simplified estimation method is also provided and its scope of application is clarified. The mechanism of internal pressure fluctuation is obtained by using the proposed method in the frequency domain and a new equivalent opening ratio is defined to evaluate internal pressure fluctuation. A series of low-rise building models with various openings and internal volumes were designed for wind tunnel tests with results agreeing well with analytical results. It is shown that the proposed frequency domain method based on Gaussian distribution of internal pressure fluctuations can be applied to predict the RMS internal pressure coefficient with adequate accuracy for any opening dimensions, while the simplified method can only be used for structure with single dominant opening. Helmholtz resonance is likely to occur when the equivalent opening ratio is adequately high, and controlling individual opening dimension is an effective strategy for avoiding Helmholtz resonance in engineering.展开更多
The windward bend lattice frame structure(WB structure)is characterized by a high heat transfer coefficient and low friction factor.The WB structure can be applied for ther-mal protection system,protecting outer walls...The windward bend lattice frame structure(WB structure)is characterized by a high heat transfer coefficient and low friction factor.The WB structure can be applied for ther-mal protection system,protecting outer walls of afterburner and nozzles from being damaged by the heating load of hot gas,for air cooling system of the power battery module,dissipating the heat generated during its charging and discharging.In this paper,the heat transfer charac-teristics of the windward bend lattice frame structure have been comprehensively studied.A systematic 3D numerical simulation has been conducted to investigate the effects of the struc-tural parameters of the WB structure,including the pitches in both flow direction and transverse direction,the diameter and the inclination angle of windward bend ligament,on its flow resis-tance and heat transfer enhancement,which has been evaluated by comparing its Nusselt num-ber under an equal pumping power.Furthermore,the contribution of an important parameter,i.e.,the ratio of the interstitial heat transfer rate to the end-wall heat transfer rate(RQ),to the overall heat transfer rate has been fully discussed.As a result,the case of 6 units in the longi-tudinal direction and 2.5 units in the transverse direction,i.e.(nx Z 6,nz Z 2.5)exhibits the best performance in the light of the value of the Nusselt number. Moreover, the structure with aratio of RQ ranges in 4.5e5.0 achieves a better heat transfer performance. Finally, two colorcontour graphs showing an optimal range of Nusselt number coordinated by unit numbers(nx, nz) for pumping powers of 2500 and 3000 have been presented. The graphs correctly reflectthe variation of Nusselt numbers of structures with different nx and nz, and the conclusionsremain consistent with the discussion in sections 4.2 and 4.3, instructing the reasonable selec-tion of structural parameters of a thermal protection system embedded with WB structure.展开更多
The analysis of wind load characteristics of gas-ribbed film structure plays an important role in the performance of the long-span membrane structure.This paper mainly researches on the long-span rib membrane structur...The analysis of wind load characteristics of gas-ribbed film structure plays an important role in the performance of the long-span membrane structure.This paper mainly researches on the long-span rib membrane structure.Surface wind pressure of the membrane structure is calculated by fluent,the distribution of force and surface pressure of the membrane structure under different angles and wind speeds is obtained.The worst working condition of the wind approach angle is 60°.Maximum force angle is positively correlated with windward angle and the length of structure.展开更多
文摘本文利用新一代中尺度数值天气模式Weather Research and Forecasting Model(v3.1.1,WRFV3)、日本气象厅20 km分析资料及自动站观测数据等模拟了2008年8月25日上海一次特大暴雨过程,并研究了城市化对这次暴雨过程的影响.研究结果表明:WRFV3模式能够较好地模拟出上海0825暴雨的主要分布特征,强降水中心以及暴雨随时间变化趋势;上海城市化使得这次暴雨过程在城市中心区域和迎风区降雨增强,城市背风区降雨减少;而城市化引起的陆面粗糙度等变化的动力作用对城市地区低层风场产生阻挡,使得城市迎风区垂直上升运动增强、水汽增多,是造成城市迎风区降雨增强的主要原因.
基金Project (No. 50578144) supported by the National Natural ScienceFoundation of China
文摘Theoretical analysis and wind tunnel tests were carried out to study wind-induced intemal pressure response for the structure with single windward opening and background leakage. Its goveming differential equation was derived by the Bemoulli equation in an unsteady-isentropic form. Numerical examples were provided to study the additive damping caused by background leakage in laminar and turbulent flow, and the influence of background leakage on fluctuating internal pressure response was quantized. A series of models for low-rise building with various opening ratios and background leakage were designed and wind tunnel tests were conducted. It is shown that the fluctuating intemal pressure reduces when the background leakage are considered and that the effect of background leakage can be predicted accurately by the governing differential equation deduced in this paper.
基金Project (No. 50378085) supported by the National Natural ScienceFoundation of China
文摘A frequency domain method for estimating wind-induced fluctuating internal pressure of structure with single windward opening is presented in this paper and wind tunnel tests were carried out to verify the theory. The nonlinear differential equation of internal pressure dynamics and iteration algorithm were applied to calculate fluctuating internal pressure and time domain analysis was used to verify the accuracy of the proposed method. A simplified estimation method is also provided and its scope of application is clarified. The mechanism of internal pressure fluctuation is obtained by using the proposed method in the frequency domain and a new equivalent opening ratio is defined to evaluate internal pressure fluctuation. A series of low-rise building models with various openings and internal volumes were designed for wind tunnel tests with results agreeing well with analytical results. It is shown that the proposed frequency domain method based on Gaussian distribution of internal pressure fluctuations can be applied to predict the RMS internal pressure coefficient with adequate accuracy for any opening dimensions, while the simplified method can only be used for structure with single dominant opening. Helmholtz resonance is likely to occur when the equivalent opening ratio is adequately high, and controlling individual opening dimension is an effective strategy for avoiding Helmholtz resonance in engineering.
基金The authors are grateful for financial support from grant of National Science Foundation of China(No.52006179)from the Fundamental Research Funds for the Central Universities(31020190QD706 and 3102020OMS701)from the National Science and Technology Major Project(J2019-III-0019-0063).
文摘The windward bend lattice frame structure(WB structure)is characterized by a high heat transfer coefficient and low friction factor.The WB structure can be applied for ther-mal protection system,protecting outer walls of afterburner and nozzles from being damaged by the heating load of hot gas,for air cooling system of the power battery module,dissipating the heat generated during its charging and discharging.In this paper,the heat transfer charac-teristics of the windward bend lattice frame structure have been comprehensively studied.A systematic 3D numerical simulation has been conducted to investigate the effects of the struc-tural parameters of the WB structure,including the pitches in both flow direction and transverse direction,the diameter and the inclination angle of windward bend ligament,on its flow resis-tance and heat transfer enhancement,which has been evaluated by comparing its Nusselt num-ber under an equal pumping power.Furthermore,the contribution of an important parameter,i.e.,the ratio of the interstitial heat transfer rate to the end-wall heat transfer rate(RQ),to the overall heat transfer rate has been fully discussed.As a result,the case of 6 units in the longi-tudinal direction and 2.5 units in the transverse direction,i.e.(nx Z 6,nz Z 2.5)exhibits the best performance in the light of the value of the Nusselt number. Moreover, the structure with aratio of RQ ranges in 4.5e5.0 achieves a better heat transfer performance. Finally, two colorcontour graphs showing an optimal range of Nusselt number coordinated by unit numbers(nx, nz) for pumping powers of 2500 and 3000 have been presented. The graphs correctly reflectthe variation of Nusselt numbers of structures with different nx and nz, and the conclusionsremain consistent with the discussion in sections 4.2 and 4.3, instructing the reasonable selec-tion of structural parameters of a thermal protection system embedded with WB structure.
文摘The analysis of wind load characteristics of gas-ribbed film structure plays an important role in the performance of the long-span membrane structure.This paper mainly researches on the long-span rib membrane structure.Surface wind pressure of the membrane structure is calculated by fluent,the distribution of force and surface pressure of the membrane structure under different angles and wind speeds is obtained.The worst working condition of the wind approach angle is 60°.Maximum force angle is positively correlated with windward angle and the length of structure.
