In order to describe an investigation of the flow around high-speed train on a bridge under cross winds using detached-eddy simulation(DES), a 1/8th scale model of a three-car high-speed train and a typical bridge mod...In order to describe an investigation of the flow around high-speed train on a bridge under cross winds using detached-eddy simulation(DES), a 1/8th scale model of a three-car high-speed train and a typical bridge model are employed, Numerical wind tunnel technology based on computational fluid dynamics(CFD) is used, and the CFD models are set as stationary models. The Reynolds number of the flow, based on the inflow velocity and the height of the vehicle, is 1.9×10~6. The computations are conducted under three cases, train on the windward track on the bridge(WWC), train on the leeward track on the bridge(LWC) and train on the flat ground(FGC). Commercial software FLUENT is used and the mesh sensitivity research is carried out by three different grids: coarse, medium and fine. Results show that compared with FGC case, the side force coefficients of the head cars for the WWC and LWC cases increases by 14% and 29%, respectively; the coefficients of middle cars for the WWC and LWC increase by 32% and 10%, respectively; and that of the tail car increases by 45% for the WWC whereas decreases by 2% for the LWC case. The most notable thing is that the side force and the rolling moment of the head car are greater for the LWC, while the side force and the rolling moment of the middle car and the tail car are greater for the WWC. Comparing the velocity profiles at different locations, the flow is significantly influenced by the bridge-train system when the air is close to it. For the three cases(WWC, LWC and FGC), the pressure on the windward side of train is mostly positive while that of the leeward side is negative. The discrepancy of train's aerodynamic force is due to the different surface area of positive pressure and negative pressure zone. Many vortices are born on the leeward edge of the roofs. Theses vortices develop downstream, detach and dissipate into the wake region. The eddies develop irregularly, leading to a noticeably turbulent flow at leeward side of train.展开更多
RAN S(R eyno lds-averaged N av ier-Stokes)加湍流模型是当前计算飞机粘性流场的最常用方法,数值实践说明要计算大分离流动,需要更高级的方法例如LES(Large Eddy S im u lation)或DN S(D irect N S S im u lation)。然而实际雷诺数下,...RAN S(R eyno lds-averaged N av ier-Stokes)加湍流模型是当前计算飞机粘性流场的最常用方法,数值实践说明要计算大分离流动,需要更高级的方法例如LES(Large Eddy S im u lation)或DN S(D irect N S S im u lation)。然而实际雷诺数下,LES和DN S对网格的要求太高,以至目前还难以应用。DES(D etached-Eddy S im u lation)方法结合了RAN S和LES的优点,通过对Spalart-A llm aras湍流模型中长度尺度的修正,在近壁面它体现为RAN S模型的特点,而在远离物面处又保持LES的亚格子模型的特性。论文对比了采用RAN S和DES方法数值模拟翼型失速特性的能力,并与实验结果进行了对比。结果表明,对大分离流动的数值模拟,DES方法体现出更强的能力。展开更多
采用基于M enter k-ωSST两方程湍流模型的脱体涡模拟(D etached Eddy S im u lation,DES)方法,求解N av ier-Stokes方程,数值模拟了超音速下圆柱底部的大分离流动。脱体涡模拟在近物面区采用雷诺平均方法,在其它区域采用Sm agorinsk i...采用基于M enter k-ωSST两方程湍流模型的脱体涡模拟(D etached Eddy S im u lation,DES)方法,求解N av ier-Stokes方程,数值模拟了超音速下圆柱底部的大分离流动。脱体涡模拟在近物面区采用雷诺平均方法,在其它区域采用Sm agorinsk i大涡模拟方法,兼具前者计算量小的优点和后者能模拟大分离湍流流动的优势。与雷诺平均方法的计算结果进行对比发现,DES方法可以更好地模拟分离涡的发展,得到的底部径向压力分布的时间平均值与实验值吻合。展开更多
定日镜作为典型的风敏感结构,设计中必须考虑其动力特性和风致响应。选用大涡模拟(large eddy simulation,LES)和分离涡模拟(detached eddy simulation,DES),结合一种新的湍流脉动流场产生方法(discretizing and synthesizing random fl...定日镜作为典型的风敏感结构,设计中必须考虑其动力特性和风致响应。选用大涡模拟(large eddy simulation,LES)和分离涡模拟(detached eddy simulation,DES),结合一种新的湍流脉动流场产生方法(discretizing and synthesizing random flow generation,DSRFG)模拟风场的湍流边界条件,计算得到了0°风向角下0°、30°、60°镜面仰角下定日镜的流场分布和风荷载时程数据。建立了定日镜整体结构的有限元模型,进行了定日镜整体结构在不同镜面仰角下的风致响应分析。结果表明,通过与风洞试验结果对比,LES和DES能较好地预测出顺风向等效风荷载,但LES的结果更接近试验值;随着仰角增大,定日镜下部的共振峰值能量逐渐减小,上部的共振峰值能量逐渐增大;定日镜下部的最不利工况为仰角0°时,风振系数为3.1,中上部的最不利工况发生在仰角为60°时,风振系数分别为2.0、3.4;LES和DES能较好地模拟出流场中的紊流与涡旋,且随着仰角增大,尾流区变得狭长。结合风洞试验,为定日镜以及相似结构的数值模拟以及抗风设计提供了参考。展开更多
基金Project(U1534210)supported by the National Natural Science Foundation of ChinaProject(14JJ1003)supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2015CX003)supported by the Project of Innovation-driven Plan in Central South University,ChinaProject(14JC1003)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2015T002-A)supported by the Technological Research and Development program of China Railways Cooperation
文摘In order to describe an investigation of the flow around high-speed train on a bridge under cross winds using detached-eddy simulation(DES), a 1/8th scale model of a three-car high-speed train and a typical bridge model are employed, Numerical wind tunnel technology based on computational fluid dynamics(CFD) is used, and the CFD models are set as stationary models. The Reynolds number of the flow, based on the inflow velocity and the height of the vehicle, is 1.9×10~6. The computations are conducted under three cases, train on the windward track on the bridge(WWC), train on the leeward track on the bridge(LWC) and train on the flat ground(FGC). Commercial software FLUENT is used and the mesh sensitivity research is carried out by three different grids: coarse, medium and fine. Results show that compared with FGC case, the side force coefficients of the head cars for the WWC and LWC cases increases by 14% and 29%, respectively; the coefficients of middle cars for the WWC and LWC increase by 32% and 10%, respectively; and that of the tail car increases by 45% for the WWC whereas decreases by 2% for the LWC case. The most notable thing is that the side force and the rolling moment of the head car are greater for the LWC, while the side force and the rolling moment of the middle car and the tail car are greater for the WWC. Comparing the velocity profiles at different locations, the flow is significantly influenced by the bridge-train system when the air is close to it. For the three cases(WWC, LWC and FGC), the pressure on the windward side of train is mostly positive while that of the leeward side is negative. The discrepancy of train's aerodynamic force is due to the different surface area of positive pressure and negative pressure zone. Many vortices are born on the leeward edge of the roofs. Theses vortices develop downstream, detach and dissipate into the wake region. The eddies develop irregularly, leading to a noticeably turbulent flow at leeward side of train.
文摘RAN S(R eyno lds-averaged N av ier-Stokes)加湍流模型是当前计算飞机粘性流场的最常用方法,数值实践说明要计算大分离流动,需要更高级的方法例如LES(Large Eddy S im u lation)或DN S(D irect N S S im u lation)。然而实际雷诺数下,LES和DN S对网格的要求太高,以至目前还难以应用。DES(D etached-Eddy S im u lation)方法结合了RAN S和LES的优点,通过对Spalart-A llm aras湍流模型中长度尺度的修正,在近壁面它体现为RAN S模型的特点,而在远离物面处又保持LES的亚格子模型的特性。论文对比了采用RAN S和DES方法数值模拟翼型失速特性的能力,并与实验结果进行了对比。结果表明,对大分离流动的数值模拟,DES方法体现出更强的能力。
文摘采用基于M enter k-ωSST两方程湍流模型的脱体涡模拟(D etached Eddy S im u lation,DES)方法,求解N av ier-Stokes方程,数值模拟了超音速下圆柱底部的大分离流动。脱体涡模拟在近物面区采用雷诺平均方法,在其它区域采用Sm agorinsk i大涡模拟方法,兼具前者计算量小的优点和后者能模拟大分离湍流流动的优势。与雷诺平均方法的计算结果进行对比发现,DES方法可以更好地模拟分离涡的发展,得到的底部径向压力分布的时间平均值与实验值吻合。
文摘定日镜作为典型的风敏感结构,设计中必须考虑其动力特性和风致响应。选用大涡模拟(large eddy simulation,LES)和分离涡模拟(detached eddy simulation,DES),结合一种新的湍流脉动流场产生方法(discretizing and synthesizing random flow generation,DSRFG)模拟风场的湍流边界条件,计算得到了0°风向角下0°、30°、60°镜面仰角下定日镜的流场分布和风荷载时程数据。建立了定日镜整体结构的有限元模型,进行了定日镜整体结构在不同镜面仰角下的风致响应分析。结果表明,通过与风洞试验结果对比,LES和DES能较好地预测出顺风向等效风荷载,但LES的结果更接近试验值;随着仰角增大,定日镜下部的共振峰值能量逐渐减小,上部的共振峰值能量逐渐增大;定日镜下部的最不利工况为仰角0°时,风振系数为3.1,中上部的最不利工况发生在仰角为60°时,风振系数分别为2.0、3.4;LES和DES能较好地模拟出流场中的紊流与涡旋,且随着仰角增大,尾流区变得狭长。结合风洞试验,为定日镜以及相似结构的数值模拟以及抗风设计提供了参考。
