在一个蓄电池单位上的流动的 LES 模拟一在水下压缩空气精力存储设备被进行。蓄电池单位由三接触组成在水下汽球安排在一种花的配置。流动的结构经由 Q 标准的三维的 iso 表面被检验。旋涡的核心被观察在上下风汽球出现。这些旋涡的核...在一个蓄电池单位上的流动的 LES 模拟一在水下压缩空气精力存储设备被进行。蓄电池单位由三接触组成在水下汽球安排在一种花的配置。流动的结构经由 Q 标准的三维的 iso 表面被检验。旋涡的核心被观察在上下风汽球出现。这些旋涡的核心产生的打漩的试管流动通过三根维的路径线被描绘。流动动力学经由对流动方向垂直的二个维的涡度轮廓的时间系列快照被设想；揭示上述的流打漩试管的狂暴的放荡运动流动。装载的水动力学的时间历史以电梯被介绍并且拖系数。在花的配置拖每个单个汽球的系数比一个单个汽球的小。总数拖三个动人的汽球的花的单位的系数，这被发现，即汽球的 drag 系数的求和，而它提供存储能力三次，不比一个单个汽球的太多大。除了它在设计适当基础和支持的实际意义，装载的即时水动力学被用来决定流的旋涡试管的狂暴的打漩热闹运动的频率；Strouhal 数字被发现比在一样的雷纳兹数字的一个单个范围的大。展开更多
The drag reduction effect of super-hydrophobic surface induced by the entrapped gas is unstable due to the gradual disappearance of the trapped gas.In this paper,a hydrophobic transverse grooved surface was designed t...The drag reduction effect of super-hydrophobic surface induced by the entrapped gas is unstable due to the gradual disappearance of the trapped gas.In this paper,a hydrophobic transverse grooved surface was designed to sustain gas in valleys.A detail numerical simulation was presented to investigate the flow field near the proposed surface.When water flowed over this surface,the entrapped gas was blocked by the ridges and the solid-liquid interface was replaced by the liquid-gas interface due to the entrapped gas,furthermore the micro-vortex formed in the groove.Because there was an effective slippage between water and solid induced by the entrapped gas,the velocity gradient of boundary layer decreased,which contributed to a remarkable drag reduction effect.Additionally,considering the extra undesired pressure drag reduction which negatively impacted the drag reduction effect of this method,the total drag coefficient including the viscous drag coefficient and the pressure coefficient was analyzed.An effective drag reduction rate of about 15%was achieved and the effect of this method was confirmed by experiments conducted in a high-speed water tunnel when grooves were optimized.展开更多
The present study numerically investigates the characteristics of three-dimensional turbulent flow and heat transfer in the channel with one corrugated wall heated with constant temperature by means of large eddy simu...The present study numerically investigates the characteristics of three-dimensional turbulent flow and heat transfer in the channel with one corrugated wall heated with constant temperature by means of large eddy simulation.The corrugated wall is sinusoidal in the streamwise and spanwise directions.The Reynolds number in terms of bulk velocity and channel half-height is fixed at 2800 and the wave amplitude to wavelength ratio is varied in the rangeα/λ=0.01,0.02,0.04 in the streamwise direction andα/λ=0.01,0.02,0.04 in the spanwise direction.The results show that flow separation bubbles appear and near-wall streamwise vortices are generated with larger population in the upslope region of the bottom wall as wave amplitude increases.Compared with flat wall,the corrugated geometry increases the pressure coefficient and decreases the friction coefficient on the corrugated wall,and consequently increases the total drag coefficient owing to the increase of pressure coefficient,as expected,the heat transfer is higher.The waves in the spanwise direction converge the vortices into the trough along the streamwise direction and push them away from the bottom wall.Finally,thermal performance factor is defined and the effects of wave amplitude on the thermal performance are scrutinized.展开更多
文摘在一个蓄电池单位上的流动的 LES 模拟一在水下压缩空气精力存储设备被进行。蓄电池单位由三接触组成在水下汽球安排在一种花的配置。流动的结构经由 Q 标准的三维的 iso 表面被检验。旋涡的核心被观察在上下风汽球出现。这些旋涡的核心产生的打漩的试管流动通过三根维的路径线被描绘。流动动力学经由对流动方向垂直的二个维的涡度轮廓的时间系列快照被设想；揭示上述的流打漩试管的狂暴的放荡运动流动。装载的水动力学的时间历史以电梯被介绍并且拖系数。在花的配置拖每个单个汽球的系数比一个单个汽球的小。总数拖三个动人的汽球的花的单位的系数，这被发现，即汽球的 drag 系数的求和，而它提供存储能力三次，不比一个单个汽球的太多大。除了它在设计适当基础和支持的实际意义，装载的即时水动力学被用来决定流的旋涡试管的狂暴的打漩热闹运动的频率；Strouhal 数字被发现比在一样的雷纳兹数字的一个单个范围的大。
基金supported by the National Natural Science Foundation of China(Grant Nos.51075228 and 51021064)
文摘The drag reduction effect of super-hydrophobic surface induced by the entrapped gas is unstable due to the gradual disappearance of the trapped gas.In this paper,a hydrophobic transverse grooved surface was designed to sustain gas in valleys.A detail numerical simulation was presented to investigate the flow field near the proposed surface.When water flowed over this surface,the entrapped gas was blocked by the ridges and the solid-liquid interface was replaced by the liquid-gas interface due to the entrapped gas,furthermore the micro-vortex formed in the groove.Because there was an effective slippage between water and solid induced by the entrapped gas,the velocity gradient of boundary layer decreased,which contributed to a remarkable drag reduction effect.Additionally,considering the extra undesired pressure drag reduction which negatively impacted the drag reduction effect of this method,the total drag coefficient including the viscous drag coefficient and the pressure coefficient was analyzed.An effective drag reduction rate of about 15%was achieved and the effect of this method was confirmed by experiments conducted in a high-speed water tunnel when grooves were optimized.
基金supported by the National Natural Science Foundation of China(Grant No.50476063)
文摘The present study numerically investigates the characteristics of three-dimensional turbulent flow and heat transfer in the channel with one corrugated wall heated with constant temperature by means of large eddy simulation.The corrugated wall is sinusoidal in the streamwise and spanwise directions.The Reynolds number in terms of bulk velocity and channel half-height is fixed at 2800 and the wave amplitude to wavelength ratio is varied in the rangeα/λ=0.01,0.02,0.04 in the streamwise direction andα/λ=0.01,0.02,0.04 in the spanwise direction.The results show that flow separation bubbles appear and near-wall streamwise vortices are generated with larger population in the upslope region of the bottom wall as wave amplitude increases.Compared with flat wall,the corrugated geometry increases the pressure coefficient and decreases the friction coefficient on the corrugated wall,and consequently increases the total drag coefficient owing to the increase of pressure coefficient,as expected,the heat transfer is higher.The waves in the spanwise direction converge the vortices into the trough along the streamwise direction and push them away from the bottom wall.Finally,thermal performance factor is defined and the effects of wave amplitude on the thermal performance are scrutinized.
