This paper put forward a new-type vortex generator enhancing heat exchange of solar air-drier and air-heater on the gas side,and investigated the mechanism of heat transfer enhancement and drag reduction by the influe...This paper put forward a new-type vortex generator enhancing heat exchange of solar air-drier and air-heater on the gas side,and investigated the mechanism of heat transfer enhancement and drag reduction by the influence of vortex generators on the coherent structure of turbulent boundary layer.The flow and heat transfer characteristics of rectangle channel with bevel-cut half-elliptical column vortex generators were obtained using large eddy simulation(LES)and the hydromechanics software FLUENT6.3.The instantaneous properties of velocity,temperature and pressure in channel were gained.The coherent structure of turbulent boundary layer flow was showed,and the characteristic of vortex induced by inclined-cut semi-ellipse vortex generator and its influence on turbulent coherent structure were analyzed.And the effect mechanism of turbulent coherent structure on flow field,pressure field and temperature field was discussed.Based on the results,the heat transfer coefficient and drag reduction of the new vortex generator with different pitch angles were compared.Sometimes,the coherent effects of the increased wall heat transfer and the decreased skin friction do not satisfy the Reynolds analogy.The turbulent coherent structure can be controlled through the geometry of the vortex generator,so the heat transfer and drag reduction can also be controlled.Then we can seek suitable form of vortex generator and structure parameters,in order to achieve the enhanced heat transfer and flow of drag reduction in the solar air-heater and solar air-drier.展开更多
A finite volume,multiphase solver in the framework of OpenFOAM was used to calculate the flow field of the cavitating flow over the Clark-Y hydrofoil. This solver used Transport Based Equation Model(TEM) to solve the ...A finite volume,multiphase solver in the framework of OpenFOAM was used to calculate the flow field of the cavitating flow over the Clark-Y hydrofoil. This solver used Transport Based Equation Model(TEM) to solve the liquid volume fraction,and utilized volume of fluid(VOF) technique to predict the interface between liquid and vapor phases. The simulation was designed to study the cavitation shedding and different fluid characteristics in the cloud cavitation regime when adopting two different Large Eddy Simulation(LES) models,namely,one equation eddy viscosity(one EqEddy) model and Smagorinsky model. It is shown that these two models can be used to study the cavitation shedding dynamics and predict the velocity profiles.展开更多
文章使用超大涡模拟(very large eddy simulation,VLES)方法耦合离散相模型对液体射流在横向气流中雾化过程进行模拟,并对比多套网格尺度下不同湍流模型的预测结果。结果表明,VLES方法能够较为准确地预测横向射流的基本形态及参数。相...文章使用超大涡模拟(very large eddy simulation,VLES)方法耦合离散相模型对液体射流在横向气流中雾化过程进行模拟,并对比多套网格尺度下不同湍流模型的预测结果。结果表明,VLES方法能够较为准确地预测横向射流的基本形态及参数。相对其他湍流模型在不同网格尺度下模拟结果波动明显,VLES方法对网格尺寸敏感度较低,并在模拟流场流动细节方面能够捕捉到更多液柱破碎的表面结构,较雷诺平均(Reynolds-averaged Navier-Stokes,RANS)模拟方法有显著优势,且计算量比大涡模拟(large eddy simulation,LES)方法大大降低,在工程实际运用中是一种颇具潜力的数值研究方法。展开更多
为降低高速列车受电弓气动噪声,采用大涡模拟(Large Eddy Simulation,LES)和FW-H(Ffowcs Williams and Hawkings)声类比方法,在对空气流动及表面声辐射影响较大的原型受电弓圆形上下臂杆及绝缘子立柱进行尖椭圆化改型设计基础上,采用三...为降低高速列车受电弓气动噪声,采用大涡模拟(Large Eddy Simulation,LES)和FW-H(Ffowcs Williams and Hawkings)声类比方法,在对空气流动及表面声辐射影响较大的原型受电弓圆形上下臂杆及绝缘子立柱进行尖椭圆化改型设计基础上,采用三维流体分析软件STAR-CCM+对不同形状杆件受电弓进行流场特征和气动噪声数值模拟,并与原型受电弓进行对比。结果表明:受电弓远场辐射噪声主要集中在弓头、上下臂杆、底架及绝缘子等部位,尖椭圆化设计使受电弓上下臂杆和绝缘子迎流面压力减小,受电弓表面及周围流场的压力波动减弱,这是由于气流撞击受电弓形成的大尺度涡旋沿纵向方向发展破碎形成更小尺度的涡旋结构,进而降低了受电弓气动噪声;尖椭圆形状的改型受电弓较原型受电弓在横向、纵向方向均有气动降噪效果,时速350和400 km条件下改型受电弓纵向方向25 m处可分别降噪5.1和2.4 dB,降幅分别为6.7%和3.0%。研究结果可为设计制造新型低噪声高速列车受电弓提供基本数据支撑。展开更多
基金Supported by National Natural Science Foundation of China(50676027)
文摘This paper put forward a new-type vortex generator enhancing heat exchange of solar air-drier and air-heater on the gas side,and investigated the mechanism of heat transfer enhancement and drag reduction by the influence of vortex generators on the coherent structure of turbulent boundary layer.The flow and heat transfer characteristics of rectangle channel with bevel-cut half-elliptical column vortex generators were obtained using large eddy simulation(LES)and the hydromechanics software FLUENT6.3.The instantaneous properties of velocity,temperature and pressure in channel were gained.The coherent structure of turbulent boundary layer flow was showed,and the characteristic of vortex induced by inclined-cut semi-ellipse vortex generator and its influence on turbulent coherent structure were analyzed.And the effect mechanism of turbulent coherent structure on flow field,pressure field and temperature field was discussed.Based on the results,the heat transfer coefficient and drag reduction of the new vortex generator with different pitch angles were compared.Sometimes,the coherent effects of the increased wall heat transfer and the decreased skin friction do not satisfy the Reynolds analogy.The turbulent coherent structure can be controlled through the geometry of the vortex generator,so the heat transfer and drag reduction can also be controlled.Then we can seek suitable form of vortex generator and structure parameters,in order to achieve the enhanced heat transfer and flow of drag reduction in the solar air-heater and solar air-drier.
基金The research was supported by the National Natural Science Foundation of China(No.51422906).References
文摘A finite volume,multiphase solver in the framework of OpenFOAM was used to calculate the flow field of the cavitating flow over the Clark-Y hydrofoil. This solver used Transport Based Equation Model(TEM) to solve the liquid volume fraction,and utilized volume of fluid(VOF) technique to predict the interface between liquid and vapor phases. The simulation was designed to study the cavitation shedding and different fluid characteristics in the cloud cavitation regime when adopting two different Large Eddy Simulation(LES) models,namely,one equation eddy viscosity(one EqEddy) model and Smagorinsky model. It is shown that these two models can be used to study the cavitation shedding dynamics and predict the velocity profiles.
文摘为降低高速列车受电弓气动噪声,采用大涡模拟(Large Eddy Simulation,LES)和FW-H(Ffowcs Williams and Hawkings)声类比方法,在对空气流动及表面声辐射影响较大的原型受电弓圆形上下臂杆及绝缘子立柱进行尖椭圆化改型设计基础上,采用三维流体分析软件STAR-CCM+对不同形状杆件受电弓进行流场特征和气动噪声数值模拟,并与原型受电弓进行对比。结果表明:受电弓远场辐射噪声主要集中在弓头、上下臂杆、底架及绝缘子等部位,尖椭圆化设计使受电弓上下臂杆和绝缘子迎流面压力减小,受电弓表面及周围流场的压力波动减弱,这是由于气流撞击受电弓形成的大尺度涡旋沿纵向方向发展破碎形成更小尺度的涡旋结构,进而降低了受电弓气动噪声;尖椭圆形状的改型受电弓较原型受电弓在横向、纵向方向均有气动降噪效果,时速350和400 km条件下改型受电弓纵向方向25 m处可分别降噪5.1和2.4 dB,降幅分别为6.7%和3.0%。研究结果可为设计制造新型低噪声高速列车受电弓提供基本数据支撑。
