针对变矩器常用的基于等倾角射影定理的叶片厚度设计方法(简称为等倾角射影法)带来的叶片三维形态连续性差,以及变矩器效率和能容低下问题,提出符合美国国家航空咨询委员会(National Advisory Committee for Aeronautics,NACA)翼型特征...针对变矩器常用的基于等倾角射影定理的叶片厚度设计方法(简称为等倾角射影法)带来的叶片三维形态连续性差,以及变矩器效率和能容低下问题,提出符合美国国家航空咨询委员会(National Advisory Committee for Aeronautics,NACA)翼型特征的液力变矩器叶片厚度设计方法。通过定义NACA翼型函数的分段约束,使其符合液力变矩器的流固耦合要求,实现变矩器翼型函数系数的确定。根据翼型函数及直纹曲面规则分别得出叶片厚度值与法向加厚方向,从而得出液力变矩器叶片厚度矢量,实现叶片厚度的设计(简称法向加厚法)。以某型号双涡轮液力变矩器为参照对象,分别利用本方法与等倾角射影法建立模型,对比CFD仿真结果与台架试验结果可知,利用该方法有效地减少了叶片设计参数,设计出的水滴状叶片能够提高变矩器的效率,实现叶片的自动化设计。展开更多
Particle image velocimetry （PIV） experimental results of wake flow structure of a NACA0012 airfoil with small attack angle mounted above water surface are introduced.The experiment was carried out in a small-scale w...Particle image velocimetry （PIV） experimental results of wake flow structure of a NACA0012 airfoil with small attack angle mounted above water surface are introduced.The experiment was carried out in a small-scale wind-wave tunnel.The diameter of wind-wave tunnel test section is 1.7 m （long） × 0.4 m （width） × 0.4 m （height）.The flow fields around the airfoil were measured under four diffierent conditions by varying the distance between the airfoil and the water surface.The attack angle of the airfoil was kept 10- during the experiment.For each experimental condition,the time series of particle images was captured to calculate continuous evolution of the velocity fields.The velocity fields were ensemble averaged to get the statistic parameters such as mean velocity and vorticity.Typical instantaneous velocity fields for each case are introduced to show the basic flow structure of wind surface flow separation.The aerodynamic loads acting on the airfoil are analyzed qualitatively according to the mean vorticity distribution in the flow field based on the theory of vorticity aerodynamics.The results indicate that the flow structures and drag/lift force of the airfoil alter remarkably with the changing distance between the airfoil and water surface.展开更多
Spark discharge plasma synthetic jets(SPJs) have been used for the active flow control study on an NACA 0021 straight-wing model in a wind tunnel. The model forces and moments were measured using a six-component sting...Spark discharge plasma synthetic jets(SPJs) have been used for the active flow control study on an NACA 0021 straight-wing model in a wind tunnel. The model forces and moments were measured using a six-component sting balance at a 20 m/s wind speed. The aim was to explore the SPJ's effect on airfoil aerodynamic by examining SPJ generators' position along the chordwise and the jet flow direction about the chord. Near the wing leading edge, two SPJ generators raised the stall angle by 2° and increased the maximum lift coefficient by 9%. The drag coefficient was decreased by 33.1%, and the lift-drag ratio was increased by 104.2% at an angle of attack above 16°. The rolling-moment coefficient was modified by 0.002, and the yawing-moment coefficient was changed by 0.0007 at angles of attack in the range of 0°–16°. The results showed that SPJs can control wing aerodynamic forces at a high angle of attack and moments at a low angle of attack.展开更多
在对前处理软件Gamibt构建二维绕流网格时,对美国国家航空咨询委员会(national advisory committee for aeronautics,简称NACA)翼型库得到的翼型数据进行了一定的修改,解决了某些点的取舍等问题,并在Gamibt当中成功建立C型网格,完成了...在对前处理软件Gamibt构建二维绕流网格时,对美国国家航空咨询委员会(national advisory committee for aeronautics,简称NACA)翼型库得到的翼型数据进行了一定的修改,解决了某些点的取舍等问题,并在Gamibt当中成功建立C型网格,完成了网格质量检查。展开更多
In this paper, the effects of icing on an NACA 23012 airfoil have been studied. Exper- iments were applied on the clean airfoil, runback ice, horn ice, and spanwise ridge ice at a Reynolds number of 0.6 x 10^6 over an...In this paper, the effects of icing on an NACA 23012 airfoil have been studied. Exper- iments were applied on the clean airfoil, runback ice, horn ice, and spanwise ridge ice at a Reynolds number of 0.6 x 10^6 over angles of attack from -8° to 20% and then results are compared. Gener- ally, it is found that ice accretion on the airfoil can contribute to formation of a flow separation bubble on the upper surface downstream from the leading edge. In addition, it is made clear that spanwise ridge ice provides the greatest negative effect on the aerodynamic performance of the airfoil. In this case, the stall angle drops about 10^6 and the maximum lift coefficient reduces about 50% which is hazardous for an airplane. While horn ice leads to a stall angle drop of about 4°and a maximum lift coefficient reduction to 21%, runback ice has the least effect on the flow pattern around the airfoil and the aerodynamic coefficients so as the stall angle decreases 2% and the maximum lift reduces about 8%.展开更多
The near-wake flow of a NACA0012 airfoils mounted above a water surface were experimentally studied in a wind/wave tunnel. The main objective of this study is to investigate the influence of the free surface on the st...The near-wake flow of a NACA0012 airfoils mounted above a water surface were experimentally studied in a wind/wave tunnel. The main objective of this study is to investigate the influence of the free surface on the structure of the airfoil trailing wake. The flow structure was measured with different ride heights between the airfoil and free surface using a Particle Image Velocimetry （PIV） system. The Reynolds number based on the chord length of the airfoil was about 3.5×10^3. For each experimental condition, large amount of instantaneous velocity fields were captured and ensemble-averaged to get the spatial distributions of mean velocity and mean vorticity, as well as turbulence statistics. The results show that the flow structures of the airfoil wake varies remarkably with the change in the ride height.展开更多
文摘针对变矩器常用的基于等倾角射影定理的叶片厚度设计方法(简称为等倾角射影法)带来的叶片三维形态连续性差,以及变矩器效率和能容低下问题,提出符合美国国家航空咨询委员会(National Advisory Committee for Aeronautics,NACA)翼型特征的液力变矩器叶片厚度设计方法。通过定义NACA翼型函数的分段约束,使其符合液力变矩器的流固耦合要求,实现变矩器翼型函数系数的确定。根据翼型函数及直纹曲面规则分别得出叶片厚度值与法向加厚方向,从而得出液力变矩器叶片厚度矢量,实现叶片厚度的设计(简称法向加厚法)。以某型号双涡轮液力变矩器为参照对象,分别利用本方法与等倾角射影法建立模型,对比CFD仿真结果与台架试验结果可知,利用该方法有效地减少了叶片设计参数,设计出的水滴状叶片能够提高变矩器的效率,实现叶片的自动化设计。
基金Project supported by the National Natural Science Foundation of China (Grant No.10572082)and the Shanghai Leading Academic Discipline Project (Grant No.Y0103)
文摘Particle image velocimetry （PIV） experimental results of wake flow structure of a NACA0012 airfoil with small attack angle mounted above water surface are introduced.The experiment was carried out in a small-scale wind-wave tunnel.The diameter of wind-wave tunnel test section is 1.7 m （long） × 0.4 m （width） × 0.4 m （height）.The flow fields around the airfoil were measured under four diffierent conditions by varying the distance between the airfoil and the water surface.The attack angle of the airfoil was kept 10- during the experiment.For each experimental condition,the time series of particle images was captured to calculate continuous evolution of the velocity fields.The velocity fields were ensemble averaged to get the statistic parameters such as mean velocity and vorticity.Typical instantaneous velocity fields for each case are introduced to show the basic flow structure of wind surface flow separation.The aerodynamic loads acting on the airfoil are analyzed qualitatively according to the mean vorticity distribution in the flow field based on the theory of vorticity aerodynamics.The results indicate that the flow structures and drag/lift force of the airfoil alter remarkably with the changing distance between the airfoil and water surface.
文摘Spark discharge plasma synthetic jets(SPJs) have been used for the active flow control study on an NACA 0021 straight-wing model in a wind tunnel. The model forces and moments were measured using a six-component sting balance at a 20 m/s wind speed. The aim was to explore the SPJ's effect on airfoil aerodynamic by examining SPJ generators' position along the chordwise and the jet flow direction about the chord. Near the wing leading edge, two SPJ generators raised the stall angle by 2° and increased the maximum lift coefficient by 9%. The drag coefficient was decreased by 33.1%, and the lift-drag ratio was increased by 104.2% at an angle of attack above 16°. The rolling-moment coefficient was modified by 0.002, and the yawing-moment coefficient was changed by 0.0007 at angles of attack in the range of 0°–16°. The results showed that SPJs can control wing aerodynamic forces at a high angle of attack and moments at a low angle of attack.
文摘In this paper, the effects of icing on an NACA 23012 airfoil have been studied. Exper- iments were applied on the clean airfoil, runback ice, horn ice, and spanwise ridge ice at a Reynolds number of 0.6 x 10^6 over angles of attack from -8° to 20% and then results are compared. Gener- ally, it is found that ice accretion on the airfoil can contribute to formation of a flow separation bubble on the upper surface downstream from the leading edge. In addition, it is made clear that spanwise ridge ice provides the greatest negative effect on the aerodynamic performance of the airfoil. In this case, the stall angle drops about 10^6 and the maximum lift coefficient reduces about 50% which is hazardous for an airplane. While horn ice leads to a stall angle drop of about 4°and a maximum lift coefficient reduction to 21%, runback ice has the least effect on the flow pattern around the airfoil and the aerodynamic coefficients so as the stall angle decreases 2% and the maximum lift reduces about 8%.
基金the National Natural Science Foundation of China (Grant No.10572082)the Shanghai Leading Academic Discipline Project (Grant No.Y0103).
文摘The near-wake flow of a NACA0012 airfoils mounted above a water surface were experimentally studied in a wind/wave tunnel. The main objective of this study is to investigate the influence of the free surface on the structure of the airfoil trailing wake. The flow structure was measured with different ride heights between the airfoil and free surface using a Particle Image Velocimetry （PIV） system. The Reynolds number based on the chord length of the airfoil was about 3.5×10^3. For each experimental condition, large amount of instantaneous velocity fields were captured and ensemble-averaged to get the spatial distributions of mean velocity and mean vorticity, as well as turbulence statistics. The results show that the flow structures of the airfoil wake varies remarkably with the change in the ride height.
