弧形闸门是水利工程中重要的挡水、泄水建筑物,虽然弧形闸门被设计成具有足够的刚度来承受设计水压,但泄水过程中水压的脉动可能会使闸门产生较大的振动,进而造成闸门的破坏。结合湍流模型和流体体积方法(volume of fluid,VOF)建立弧形...弧形闸门是水利工程中重要的挡水、泄水建筑物,虽然弧形闸门被设计成具有足够的刚度来承受设计水压,但泄水过程中水压的脉动可能会使闸门产生较大的振动,进而造成闸门的破坏。结合湍流模型和流体体积方法(volume of fluid,VOF)建立弧形闸门泄流三维湍流流场数值模型,数值求解采用稳态计算和瞬态计算两个连续的运算步骤进行,以便更好地确定入口处的流速。分别采用k-ε湍流模型和k-ω湍流模型对闸门周围流场和作用在弧形面板上的流体压力进行计算,结果表明:k-ε湍流模型与壁函数相结合的方法不能捕捉到稳定泄流阶段闸门面板上的压力脉动行为,而k-ω湍流模型结合壁面积分不仅能够得到闸门周围的流场变化,而且能准确计算闸门面板上的脉动压力。基于k-ω湍流模型计算结果,分析下游水位变化对闸门周围流场和脉动压力的影响,闸门面板上压力的脉动主要是由于闸门前的漩涡引起的,压力脉动的优势频率取决于闸孔出流形式,与上下游水位差无关,自由出流时的压力脉动优势频率比淹没出流时的大。展开更多
A tight formation of unmanned aerial vehicles(UAVs) has many advantages, such as fuel saving and deceiving enemy radar during battlefield entry. As a result, research on UAVs in close formation has received much atten...A tight formation of unmanned aerial vehicles(UAVs) has many advantages, such as fuel saving and deceiving enemy radar during battlefield entry. As a result, research on UAVs in close formation has received much attention, and the controller design for formation holding has become a popular research topic in the control field. However, there are many unknown disturbances in tight formation, and the tail aircraft is disturbed by the wake. This paper establishes a mathematical model of wake vortices for tail aircraft that considers uncertainty and strong interference. Two UAVs are simulated by Computational Fluid Dynamics software, followed by the design of a semiphysical simulation model predictive control(MPC) scheme that suppresses uncertainty and interference sufficiently to enable the tail aircraft to accurately track the lead aircraft and maintain a stable, tight formation. The tight formation controller is verified by numerical simulation and semiphysical simulation. The results show that the designed controller has an excellent control effect in the case of disturbance caused by the wake vortex.展开更多
钢管塔力学性能卓越,在电网中应用广泛。其中钢管塔主要钢管构件长细比较大,低风速下易涡激振动,进而引起结构疲劳损伤,引起连接处损坏,严重影响结构的安全性与耐久性。针对目前钢管塔杆件涡振理论研究不充分现状,基于Van Der Pol式尾...钢管塔力学性能卓越,在电网中应用广泛。其中钢管塔主要钢管构件长细比较大,低风速下易涡激振动,进而引起结构疲劳损伤,引起连接处损坏,严重影响结构的安全性与耐久性。针对目前钢管塔杆件涡振理论研究不充分现状,基于Van Der Pol式尾流振子模型进行结构计算,采用中心差分法解模型耦合方程,编制圆钢管涡激振动计算程序并设计风洞试验验证其准确性,旨在研究圆钢管的涡激振动特性,为钢管塔涡振预测及控制提供理论依据。试验与数值计算结果的比较表明,该文建立的尾流振子模型能够较好地拟合钢管的位移,由于理论模型采用理想铰接约束,试验测得的涡振锁定区较短,且锁定频率低于理论值。展开更多
文摘弧形闸门是水利工程中重要的挡水、泄水建筑物,虽然弧形闸门被设计成具有足够的刚度来承受设计水压,但泄水过程中水压的脉动可能会使闸门产生较大的振动,进而造成闸门的破坏。结合湍流模型和流体体积方法(volume of fluid,VOF)建立弧形闸门泄流三维湍流流场数值模型,数值求解采用稳态计算和瞬态计算两个连续的运算步骤进行,以便更好地确定入口处的流速。分别采用k-ε湍流模型和k-ω湍流模型对闸门周围流场和作用在弧形面板上的流体压力进行计算,结果表明:k-ε湍流模型与壁函数相结合的方法不能捕捉到稳定泄流阶段闸门面板上的压力脉动行为,而k-ω湍流模型结合壁面积分不仅能够得到闸门周围的流场变化,而且能准确计算闸门面板上的脉动压力。基于k-ω湍流模型计算结果,分析下游水位变化对闸门周围流场和脉动压力的影响,闸门面板上压力的脉动主要是由于闸门前的漩涡引起的,压力脉动的优势频率取决于闸孔出流形式,与上下游水位差无关,自由出流时的压力脉动优势频率比淹没出流时的大。
基金funded by the National Natural Science Foundation of China (Grant Nos. 62173277 and 61573286)the Natural Science Foundation of Shaanxi Province (Grant No. 2022JM-011)+1 种基金the Aeronautical Science Foundation of China (Grant No. 201905053004)the Shaanxi Province Key Laboratory of Flight Control and Simulation Technology。
文摘A tight formation of unmanned aerial vehicles(UAVs) has many advantages, such as fuel saving and deceiving enemy radar during battlefield entry. As a result, research on UAVs in close formation has received much attention, and the controller design for formation holding has become a popular research topic in the control field. However, there are many unknown disturbances in tight formation, and the tail aircraft is disturbed by the wake. This paper establishes a mathematical model of wake vortices for tail aircraft that considers uncertainty and strong interference. Two UAVs are simulated by Computational Fluid Dynamics software, followed by the design of a semiphysical simulation model predictive control(MPC) scheme that suppresses uncertainty and interference sufficiently to enable the tail aircraft to accurately track the lead aircraft and maintain a stable, tight formation. The tight formation controller is verified by numerical simulation and semiphysical simulation. The results show that the designed controller has an excellent control effect in the case of disturbance caused by the wake vortex.
文摘钢管塔力学性能卓越,在电网中应用广泛。其中钢管塔主要钢管构件长细比较大,低风速下易涡激振动,进而引起结构疲劳损伤,引起连接处损坏,严重影响结构的安全性与耐久性。针对目前钢管塔杆件涡振理论研究不充分现状,基于Van Der Pol式尾流振子模型进行结构计算,采用中心差分法解模型耦合方程,编制圆钢管涡激振动计算程序并设计风洞试验验证其准确性,旨在研究圆钢管的涡激振动特性,为钢管塔涡振预测及控制提供理论依据。试验与数值计算结果的比较表明,该文建立的尾流振子模型能够较好地拟合钢管的位移,由于理论模型采用理想铰接约束,试验测得的涡振锁定区较短,且锁定频率低于理论值。
