在低速来流条件下针对前缘位置嵌有合成射流/合成双射流激励器的机翼的水滴撞击特性开展了数值模拟研究基于Fluent软件采用Euler气液两相模型和欧拉壁面液膜(Eulerian wall film EWF)模型得到的计算结果表明在合成射流或合成双射流的主...在低速来流条件下针对前缘位置嵌有合成射流/合成双射流激励器的机翼的水滴撞击特性开展了数值模拟研究基于Fluent软件采用Euler气液两相模型和欧拉壁面液膜(Eulerian wall film EWF)模型得到的计算结果表明在合成射流或合成双射流的主动控制下阻挡了机翼前缘等积冰重点防护区域内的水滴撞击从而大幅降低了该区域的结冰强度.其机理是在高频合成射流的作用下机翼前缘上游附近形成了一对稳定的闭合回流区形成了水滴的真空区域.由于回流区内部水滴速度和质量分数较低改变了机翼前缘水滴运动轨迹和水滴收集率分布能够减少机翼前缘结冰程度并改变冰形起到了虚拟气动外形的作用.展开更多
A promising strategy of synthetic jet arrays （SJA） control for NACA0021 airfoil in preventing flow separation and delaying stall is investigated. Through aerodynamic forces, flowfield and velocity profiles measureme...A promising strategy of synthetic jet arrays （SJA） control for NACA0021 airfoil in preventing flow separation and delaying stall is investigated. Through aerodynamic forces, flowfield and velocity profiles measurements, it indicates that the synthetic jet （S J） could enlarge the mixing of the shear layer and then enhance the stability of boundary layer, resulting in scope reduction of the flow separation zone. Furthermore, the control effects of dual jet arrays positioned at 15%c （Actuator 1） and 40%c （Actuator 2） respectively are systematically investigated with different jet parameters, such as two typical relative phase angles and various incline angles of the jet. The jet closer to the leading edge of airfoil is more advantageous in delaying the stall of airfoil, and overall, the flow control performances of jet arrays are better than those of single actuator. At the angle of attack （AoA） just approaching and larger than the stall AoA, jet array with 180° phase difference could increase the lift coefficient more significantly and prevent flow separation. When momentum coefficient of the jet arrays is small, a larger jet angle of Actuator 2 is more effective in improving the maximum lift coefficient of airfoil. With a larger momentum coefficient of jet array, a smaller jet angle of Actuator 2 is more effective.展开更多
In order to improve the control ability of synthetic jets in compressible boundary layer,a novel control method based on dual synthetic cold/hot jets coupled control of velocity profile and temperature profile was pro...In order to improve the control ability of synthetic jets in compressible boundary layer,a novel control method based on dual synthetic cold/hot jets coupled control of velocity profile and temperature profile was proposed.As fundamental investigations on the effects of synthetic jet temperature on the jet behavior and flow field characteristics were essentially necessary,preliminary numerical simulations were conducted to study the influence of temperature(200 K and 400 K)on the flow field characteristics of synthetic jets using Large Eddy Simulations(LES)model.Time-averaged flow fields showed that different temperatures led to variable behavior of two strands of jets.For dual synthetic cold jets,a potential-core arose apparently with its height ranging from 0.01 to 0.03 m,while for dual synthetic hot jets,two strands of jets emerged downstream.The modal decomposition of instantaneous flow fields had been done using both Proper Orthogonal Decomposition(POD)and Dynamic Mode Decomposition(DMD).Various modes showed different characteristics of the flow fields.As the POD method focuses on the energy of flow while the DMD method focuses on the frequency,the first two modes had many similarities,but the third and fourth modes demonstrated completely different vortex structures.The current researches play a role of preliminary investigations for further and comprehensive exploration of novel flow control measures in global velocity field.展开更多
文摘在低速来流条件下针对前缘位置嵌有合成射流/合成双射流激励器的机翼的水滴撞击特性开展了数值模拟研究基于Fluent软件采用Euler气液两相模型和欧拉壁面液膜(Eulerian wall film EWF)模型得到的计算结果表明在合成射流或合成双射流的主动控制下阻挡了机翼前缘等积冰重点防护区域内的水滴撞击从而大幅降低了该区域的结冰强度.其机理是在高频合成射流的作用下机翼前缘上游附近形成了一对稳定的闭合回流区形成了水滴的真空区域.由于回流区内部水滴速度和质量分数较低改变了机翼前缘水滴运动轨迹和水滴收集率分布能够减少机翼前缘结冰程度并改变冰形起到了虚拟气动外形的作用.
基金support of the National Natural Science Foundation of China(No.11272150)
文摘A promising strategy of synthetic jet arrays （SJA） control for NACA0021 airfoil in preventing flow separation and delaying stall is investigated. Through aerodynamic forces, flowfield and velocity profiles measurements, it indicates that the synthetic jet （S J） could enlarge the mixing of the shear layer and then enhance the stability of boundary layer, resulting in scope reduction of the flow separation zone. Furthermore, the control effects of dual jet arrays positioned at 15%c （Actuator 1） and 40%c （Actuator 2） respectively are systematically investigated with different jet parameters, such as two typical relative phase angles and various incline angles of the jet. The jet closer to the leading edge of airfoil is more advantageous in delaying the stall of airfoil, and overall, the flow control performances of jet arrays are better than those of single actuator. At the angle of attack （AoA） just approaching and larger than the stall AoA, jet array with 180° phase difference could increase the lift coefficient more significantly and prevent flow separation. When momentum coefficient of the jet arrays is small, a larger jet angle of Actuator 2 is more effective in improving the maximum lift coefficient of airfoil. With a larger momentum coefficient of jet array, a smaller jet angle of Actuator 2 is more effective.
基金supported by the National Natural Science Foundation of China(Nos.11602299,11502295,11572349,11872374 and 51809271).
文摘In order to improve the control ability of synthetic jets in compressible boundary layer,a novel control method based on dual synthetic cold/hot jets coupled control of velocity profile and temperature profile was proposed.As fundamental investigations on the effects of synthetic jet temperature on the jet behavior and flow field characteristics were essentially necessary,preliminary numerical simulations were conducted to study the influence of temperature(200 K and 400 K)on the flow field characteristics of synthetic jets using Large Eddy Simulations(LES)model.Time-averaged flow fields showed that different temperatures led to variable behavior of two strands of jets.For dual synthetic cold jets,a potential-core arose apparently with its height ranging from 0.01 to 0.03 m,while for dual synthetic hot jets,two strands of jets emerged downstream.The modal decomposition of instantaneous flow fields had been done using both Proper Orthogonal Decomposition(POD)and Dynamic Mode Decomposition(DMD).Various modes showed different characteristics of the flow fields.As the POD method focuses on the energy of flow while the DMD method focuses on the frequency,the first two modes had many similarities,but the third and fourth modes demonstrated completely different vortex structures.The current researches play a role of preliminary investigations for further and comprehensive exploration of novel flow control measures in global velocity field.
