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参考文献 1
YEO H, JOHNSONW. Aeromechanics analysis of a compound helicopter[C]//Annual Forum Proceedings⁃AHS International.[S.l.]:AHS, 2006.
参考文献 2
STEIJLR, BARAKOSG, BADCOCKK. A framework for CFD analysis of helicopter rotors in hover and forward flight[J]. International Journal for Numerical Methods in Fluids, 2006, 51(8): 819⁃847.
参考文献 3
LINDA H, LEFEBVREJ N, JONESA R. Experimental investigation of reverse flow over sharp and blunt trailing edge airfoils[C]//31st AIAA Applied Aerodynamics Conference. San Diego, CA: AIAA, 2013.
参考文献 4
LINDA H, LEFEBVREJ N, JONESA R. Time⁃averaged aerodynamics of sharp and blunt trailing⁃edge static airfoils in reverse flow[J]. American Institute of Aeronautics and Astronautics Journal, 2015, 52(12):1⁃18.
参考文献 5
LINDA H, JONESA R. Vortex shedding from airfoils in reverse flow[J]. American Institute of Aero⁃nautics and Astronautics Journal, 2015, 53(9):1⁃13.
参考文献 6
LINDA H, SMITHL R, MILLUZZOJ, et al. Reynolds number effects on airfoils in reverse flow[C]//53rd AIAA Aerospace Sciences Meeting. Kissimmee, Florida: AIAA, 2013.
参考文献 7
LINDA H, SMITHL R, MILLUZZOJ I, et al. Reynolds number effects on rotor blade sections in reverse flow[J]. Journal of Aircraft, 2016, 53(5): 1248⁃1260.
参考文献 8
RAGHAVV, MAYOM, LOZANOR, et al. Evidence of vortex⁃induced lift on a yawed wing in reverse flow[J]. Proceedings of the Institution of Me⁃chanical Engineers, Part G: Journal of Aerospace Engineering, 2014, 228(11): 2130⁃2137.
参考文献 9
MAYOM, RAGHAVV, KOMERATHN. Vortex flow hypothesis for a yawed rotor blade in reverse flow[J]. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineer⁃ing, 2015, 229(3): 543⁃553.
参考文献 10
RAGHAVV, KOMERATHN. An exploration of radial flow on a rotating blade in retreating blade stall[J]. Journal of the American Helicopter Society, 2013, 58(2): 1⁃10.
参考文献 11
RAGHAVV, KOMERATHN. The intricacies of measuring radial velocity field on a rotating disk with edgewise flow[C]//50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. Nashville, Tennessee: AIAA, 2012: 424.
参考文献 12
YEO H. Investigation of UH⁃60A rotor performance and loads at high advance ratios[J]. Journal of Airc⁃raft, 2013, 50(2): 576⁃589.
参考文献 13
POTSDAMM, DATTAA, JAYARAMANB. Computational investigation and fundamental understanding of a slowed UH⁃60A rotor at high advance ratios[J]. Journal of the American Helicopter Society, 2016, 4(4): 1⁃14.
参考文献 14
袁明川,杨永飞,林永峰. 高速直升机旋翼反流区桨叶剖面翼型气动特性CFD分析[J]. 直升机技术,2015(1): 1⁃5.
YUANMingchuan, YANGYongfei, LINYongfeng. CFD analysis on aerodynamic characteristics of blade profiles in reverse flow region of high speed helicopter rotor[J]. Helicopter Technique, 2015(1): 1⁃5.
参考文献 15
CARADONNAF X, TUNGC. Experimental and analytical studies of a model helicopter rotor in hover[R]. NASA⁃TM⁃81232, 1981.
目录 contents

    摘要

    采用雷诺平均(Reynolds⁃averaged Navier⁃Stokes,RANS)方程针对直升机前飞不同前进比状态下四叶片刚性旋翼开展数值模拟研究,对比前进比0.1和0.6时的旋翼气动特性差异。计算结果表明,前飞时桨盘后行侧根部附近出现反流流动区域,翼型截面压强系数呈现非常规分布,该区域桨叶几乎不提供升力,且反流区面积随前进比的增大而增加。以静态前掠反流翼段为研究对象,采用脱体涡(Detached eddy simulation,DES)方法研究其非定常空气动力学特性,发现反流翼段表面出现特殊复杂的附着涡结构,在展向流动的影响下,翼段根部与尖部的涡结构发生耦合作用;反流翼段的升力系数随桨距角的增加而增大,且在失速迎角后并未下降。

    Abstract

    The aerodynamic characteristics of a rigid four⁃bladed rotor in forward flight at advance ratio of 0.1 and 0.6 are simulated numerically with Reynolds⁃averaged Navier⁃Stokes (RANS) methods and compared with each other. The computed results indicate that reverse flow occurs near the root area of the retreating side of the rotor, giving rise to the unconventional distributions of pressure coefficient. And the proportion of the reverse flow region, where hardly any lift is contributed, is directly related to the advance ratio and increases with the raise of the advance ratio. Detached eddy simulation (DES) method is used to calculate the unsteady aerodynamic characteristics of a yawed flat blade in reverse flow. It is found that complex attached vortex structure occurs on the surface of the blade and the vortex near the root interacts with that near the tip area under the effect of the radial flow. The lift coefficient is directly proportional to the pitch angle and does not drop after the stall angle of attack.

    直升机高速前飞时,旋翼周围的流场呈现高度复杂化,桨盘后行侧桨叶根部气流从翼型后缘流向前缘,形成反流区,同时动态失速导致桨叶表面气流径向速度分量显著,流动呈现复杂的三维特[1,2]。桨叶旋转导致桨叶翼型剖面的入流条件不断周期性变化,增加了叶片的疲劳载荷,对旋翼设计带来很大的挑战。因此,揭示旋翼桨盘后行侧复杂的流动机理对精准预测旋翼气动载荷及其优化设计至关重要。

    近年来,不断有国内外学者对翼型、翼段及桨叶的反流气动特性进行一系列的风洞试验及数值模拟研究。

    文献[3,4,5,6,7]对尖、钝尾缘的翼型反流气动特性进行风洞试验研究,测量结果表明,反流时翼型的气动性能差于其常规流动,主要表现在翼型的前缘处和后缘处都更容易发生流动分离,翼型的失速迎角降低,且俯仰力矩在攻角0°附近急剧变化,尖尾缘翼型反流时某些攻角下的气动阻力甚至是常规流动状态下的两倍。

    文献[8,9,10,11]对展弦比3.49的前掠翼段的反流气动性能开展试验研究发现,反流时翼段的总升力曲线斜率高于常规流动,截面翼型的压力中心向后缘移动至3/4弦长附近,且在翼段表面尾缘附近出现径向附着涡,他们提出猜想,该表面附着涡为反流区内桨叶提供了额外的升力,导致了高升力线斜率,并在文献[9]中对其猜想进行了验证。

    许多学者对直升机大前进比前飞时的气动性能进行了风洞试验和数值模拟研究。Yeo[12]对UH⁃60A旋翼进行研究表明:随着前进比增加,后行侧反流区范围增大,且翼型截面法向力降低; Potsdam等[13]对UH⁃60A旋翼进行研究发现,尽管反流区内的脉动正俯仰力矩较大,但该区域甚至后行桨盘的大部分区域几乎不提供拉力,且反流区内桨叶更容易出现动态失速现象,为高前进比的旋翼复杂流动提供基础性研究;袁明川等[14]分析旋翼反流区桨叶不同剖面的翼型气动特性发现,在前缘与后缘处更容易发生流动分离,且提出可采取后缘钝化措施改善反流时的气动特性。

    本文考虑0.1和0.6两种前进比,使用计算流体力学(Computational fluid dynamics, CFD)方法对刚性旋翼的非定常气动特性进行数值模拟,分析后行侧反流对翼型截面压力分布及桨叶表面流动状态的影响;为进一步探讨反流与展向流动的相互作用机理,针对反流工况下前掠效应对翼段气动特性的影响开展数值模拟研究,探究不同桨距角下翼段的气动力特性及表面的特殊流动结构。

  • 1 数值方法及计算模型

    本文通过求解RANS方程,获取旋翼气动特性及周围流场信息,其控制方程表达式为

    ui¯xi=0
    (1)
    ρui¯t+ρuj¯ui¯xj=-p¯xi+xj(τij¯-ρu'iu'j¯)
    (2)

    式中:ρp分别代表密度和压力;ui¯为速度分量;τij¯为层流黏性应力;u'iu'j¯即雷诺应力张量,代表湍流脉动所引起的动量转移。

    当风从翼型尾缘吹向前缘时,翼段周围流场呈现高度非定常特性,选择合适的湍流模型对载荷预测至关重要。本文引入DES比例因子FDES进行湍动能耗散项模拟

    FDES=maxLtCdesΔmax,1
    (3)

    式中:Cdes为DES中校准常数,一般取值为0.61;Δmax为最大网格尺度;Lt代表湍流长度尺度。

    引入SST⁃k Omega湍流模型封闭RANS方程,采用有限体积方法对方程进行求解,中心格式进行空间离散,二阶隐式格式进行时间项离散,二阶迎风格式进行对流项进行离散,速度与压力解耦通过Couple算法实现。

    使用上述RANS方法对美国航空力学实验室(Aeromachanics Laboratory)的Caradonna⁃Tung (C⁃T) 直升机旋翼模[15]进行算例测试,直升机处于悬停状态,桨距角为5°,桨尖马赫数为0.79,旋翼转速为2 268 r/min。图1为不同径向位置翼型截面的压强系数分布曲线,计算值与试验值吻合较好,验证了计算方法的精度。

    图1
                            C⁃T旋翼不同截面压强系数分布计算值与试验值对比

    图1 C⁃T旋翼不同截面压强系数分布计算值与试验值对比

    Fig.1 Comparisons between calculated and experimental values of pressure coefficient at different sections of C⁃T rotor

    本文第一部分计算模型为一刚性旋翼桨叶模型,旋翼直径为4.2 m,桨距角为10°,前进比为0.1和0.6,对应的旋翼旋转速度分别为778 r/min和160 r/min,来流风速分别为16.294 m/s和20.106 m/s。

    旋翼计算域大小为桨盘直径的25倍,分为旋转区域和静止区域,两区域之间的信息传递通过滑移网格技术实现。计算网格采用多块结构网格,总网格量为2 790万左右,桨叶表面采用贴体网格,边界层第一层网格高度保证y+1,桨叶附近网格拓扑结构如图2所示。

    图2
                            桨叶附近网格拓扑结构

    图2 桨叶附近网格拓扑结构

    Fig.2 Mesh topology around model rotor

    文献[8,9]对NACA0013反流翼段进行风洞试验测量及流动显示,本文第二部分依据试验条件进行数值模拟设置。计算模型为展弦比3.49的翼段,截面翼型为NACA0013,弦长为0.178 m。计算区域约为10倍展长的方形区域。为保证计算精度,捕捉流场细节,计算网格依旧采用多块结构网格,总网格量约为1 470万,边界层第一层网格高度保证y+1,物面及边界层网格如图3所示。

    图3
                            物面及边界层网格

    图3 物面及边界层网格

    Fig.3 Grid of wall and boundary layer

    计算区域均为静止区域,远场边界设置为速度入口与压力出口,翼段物面满足无滑移边界条件,自由来流速度为24.619 m/s,雷诺数为3×105。翼段前掠角为30°,计算桨距角包括0°,5°,8°,10°和15°,桨距角和掠角定义如图4所示。

    图4
                            桨距角及掠角定义

    图4 桨距角及掠角定义

    Fig.4 Definitions of pitch angle and sweep angle

  • 2 结果及讨论

  • 2.1 刚性旋翼反流区影响

    前进比0.1及0.6时桨叶上表面压力分布及极限流线分布如图5所示,在图5(b)中方位角270°附近红色圆圈标注的区域内,可直观地观察到气流从翼型的后缘流向前缘(如图5(c)所示),该反流区域面积占桨盘总面积的比例不超过9%;后行侧桨叶展向中间区域,表面出现明显的从叶根指向叶尖的展向流动分量,且越靠近叶尖,该分量愈发明显;而图5(a)中即前进比0.1时并未观察到上述非定常流场特征。

    图5
                            桨叶上表面压力分布极限流线图

    图5 桨叶上表面压力分布极限流线图

    Fig.5 Pressure and wall shear stress distribution of the upper surface of the rotor

    前进比为0.1时,各个方位角下叶根及叶尖翼型截面下翼面与上翼面压差均为正值,如图6,7所示。而前进比0.6时,在旋翼后行侧叶根附近,下翼面与上翼面压差降为负值,如图8所示。同时分别比较图6和图7,8,9可发现,靠近叶尖的翼型截面均未出现上述非常规压强系数分布。进一步观察图10旋翼后行侧不同方位角下翼型压力分布云图,在方位角240°处翼型下翼面后缘部分开始出现低压区,随着方位角增大,该低压区沿着下翼面向前缘发展,直至方位角300°时,当方位角继续增大时,低压区逐渐减小,反流效应逐渐减弱。

    图6
                            不同相位处翼型截面压强系数分布(前进比0.1,r/R=0.3)

    图6 不同相位处翼型截面压强系数分布(前进比0.1,r/R=0.3)

    Fig.6 Pressure coefficient distribution with advance ratio of 0.1 at r/R =0.3

    图7
                            不同相位处翼型截面压强系数分布(前进比0.1,r/R=0.8)

    图7 不同相位处翼型截面压强系数分布(前进比0.1,r/R=0.8)

    Fig.7 Pressure coefficient distribution with advance ratio of 0.1 at r/R=0.8

    图8
                            不同相位处翼型截面压强系数分布(前进比0.6,r/R =0.3)

    图8 不同相位处翼型截面压强系数分布(前进比0.6,r/R =0.3)

    Fig.8 Pressure coefficient distribution with advance ratio of 0.6 at r/R =0.3

    图10
                            不同后行方位角下翼型截面压力分布云图(前进比0.6, r/R =0.3)

    图10 不同后行方位角下翼型截面压力分布云图(前进比0.6, r/R =0.3)

    Fig.10 Pressure contour with advance ratio of 0.6 at r/R =0.3 at different retreating azimuth angles

    观察对比图5,6,7,8,9的计算结果,反流区的大小和前进比大小息息相关,前进比越大,则反流区越大。前后行侧压力分布的差异直接影响旋翼拉力分布,在小前进比时,前后行侧升力大小差别不大,升力由整个桨盘提供;而大前进比时,后行侧反流区内压强分布不规律,桨叶几乎不提供升力,桨盘升力由前行侧桨叶提供,前后行侧载荷分布不均衡。

    图9
                            不同相位处翼型截面压强系数分布(前进比0.6,r/R=0.8)

    图9 不同相位处翼型截面压强系数分布(前进比0.6,r/R=0.8)

    Fig.9 Pressure coefficient distribution with advance ratio of 0.6 at r/R=0.8

    需指出的一点是,图7中方位角180°处的压力分布较其他相位不同,这是因为该相位处翼型截面的速度分量较小,因此动压较小,导致压力系数分布较其他相位更为饱满。

  • 2.2 反流前掠翼段气动特性分析

    11为Raghav等[8,9]对展弦比3.49的前掠静止翼段的反流气动特性开展试验研究的流动显示图,试验前掠角为30°,桨距角为15°,雷诺数为1.7×105。采用DES方法计算得到的不同桨距角下翼段表面压力及极限流线分布如图12所示,计算条件均与风洞试验设置相符。在桨距角为5°时,除尖几何尾缘(即气动前缘)和顶部区域外,翼段表面均为附着流动。以上游处视角观察,表面极限流线偏离了自由来流的方向,且有顺时针旋转的趋势,这预示着当地即将形成附着涡;当桨距角增大至10°时,几何尾缘附近的负压区域沿着弦向向前缘区域发展,表面涡结构尺寸逐渐增大;当桨距角继续增大至15°时,附着流动的区域急剧减小至直角三角形所标注的区域,翼段表面的大部分区域气流方向均与自由来流方向相反,出现流动分离。需要指出的是,根部附近的流动结构与试验流动显示结果有所不同,并未出现随机杂乱无规则的涡破碎现象,这是因为在数值计算过程中并未考虑翼段根部与试验支撑架之间的相互扰动作用,且雷诺数1.7×105和雷诺数3×105下流动拓扑结构可能稍有差异,总体来说,DES方法计算得到的翼段表面流动状态与风洞试验流动显示结果吻合。

    图11
                            试验流动显示图[8,9]

    图11 试验流动显示[8,9]

    Fig.11 Tuft visualization of the upper side of the blade[8,9]

    图12
                            前掠反流翼段上表面压力及极限流线分布

    图12 前掠反流翼段上表面压力及极限流线分布

    Fig.12 Pressure and wall shear stress distribution of the upper side of blade in reverse flow

    等值涡量图如图13所示,在桨距角5°时,翼段顶部区域附近开始出现诱导涡,诱导翼段表面产生小面积范围的流动分离,随着桨距角的增大,该涡逐渐向下游发展;而翼段根部区域产生的涡的强度和上述涡有所不同,且在桨距角15°时,根部涡结构伴随着大面积的流动分离,与图12(c)中的表面极限流线分布相符;观察图13(d),顶部后缘位置附近出现新的涡结构,该涡偏离自由来流方向,且在前掠效应的影响下和根部附近的涡产生相互耦合作用。

    图13
                            不同桨距角下前掠反流翼段等值涡量图

    图13 不同桨距角下前掠反流翼段等值涡量图

    Fig.13 Iso⁃surface of vorticity magnitude at different pitch angles

    14为反流翼段的升力系数及阻力系数随桨距角变化的曲线图,其中升力曲线在线性段与试验数据吻合较好,在高桨距角时较试验值偏低;在达到失速攻角前,升力系数随着桨距角的增大而线性增长,且随着桨距角的进一步增大,升力并未出现下降,阻力系数随着桨距角非线性增长。升力并未下降的原因可能是翼段表面附着涡及附着流动区域共同为翼段提供升力,但是该猜想仍需进一步的验证分析。

    图14
                            前掠翼段气动力系数分布曲线

    图14 前掠翼段气动力系数分布曲线

    Fig.14 Coefficient of lift and drag curve plots of the yawed blade in reverse flow

  • 3 结论

    本文使用RANS方程数值模拟直升机前飞状态下刚性旋翼的非定常气动特性,分析反流区流场特征、以及对旋翼气动特性的影响;采用DES方法计算前掠反流静止翼段的气动特性,对翼段流场结构、气动力随桨距角的变化规律等开展一系列研究,主要结论总结如下:

    (1) 高前进比前飞时,旋翼后行侧桨叶根部出现小前进比工况下不显著的反流现象,且在反流与展向流动耦合作用下,翼型截面压力呈现非常规分布,该部分桨叶几乎不提供升力,桨盘前后行侧载荷分布不均衡。

    (2) 反流工况下,前掠翼段的升力系数随桨距角的增大而增大,且在失速攻角后,升力系数未下降,这是由于翼段表面出现附着涡,其与附着流动区域共同为翼段提供升力。

    (3) 翼段表面涡结构尺寸随着桨距角的增大而增大,且在展向流动影响下,顶部区域的涡结构与根部涡结构发生耦合作用。

    本文为旋翼反流区流场特征提供了初步研究,但反流与径向流动的耦合作用仍需进一步深入分析。

  • 参考文献

    • 1

      YEO H, JOHNSON W. Aeromechanics analysis of a compound helicopter[C]//Annual Forum Proceedings⁃AHS International.[S.l.]:AHS, 2006.

    • 2

      STEIJL R, BARAKOS G, BADCOCK K. A framework for CFD analysis of helicopter rotors in hover and forward flight[J]. International Journal for Numerical Methods in Fluids, 2006, 51(8): 819⁃847.

    • 3

      LIND A H, LEFEBVRE J N, JONES A R. Experimental investigation of reverse flow over sharp and blunt trailing edge airfoils[C]//31st AIAA Applied Aerodynamics Conference. San Diego, CA: AIAA, 2013.

    • 4

      LIND A H, LEFEBVRE J N, JONES A R. Time⁃averaged aerodynamics of sharp and blunt trailing⁃edge static airfoils in reverse flow[J]. American Institute of Aeronautics and Astronautics Journal, 2015, 52(12):1⁃18.

    • 5

      LIND A H, JONES A R. Vortex shedding from airfoils in reverse flow[J]. American Institute of Aero⁃nautics and Astronautics Journal, 2015, 53(9):1⁃13.

    • 6

      LIND A H, SMITH L R, MILLUZZO J, et al. Reynolds number effects on airfoils in reverse flow[C]//53rd AIAA Aerospace Sciences Meeting. Kissimmee, Florida: AIAA, 2013.

    • 7

      LIND A H, SMITH L R, MILLUZZO J I, et al. Reynolds number effects on rotor blade sections in reverse flow[J]. Journal of Aircraft, 2016, 53(5): 1248⁃1260.

    • 8

      RAGHAV V, MAYO M, LOZANO R, et al. Evidence of vortex⁃induced lift on a yawed wing in reverse flow[J]. Proceedings of the Institution of Me⁃chanical Engineers, Part G: Journal of Aerospace Engineering, 2014, 228(11): 2130⁃2137.

    • 9

      MAYO M, RAGHAV V, KOMERATH N. Vortex flow hypothesis for a yawed rotor blade in reverse flow[J]. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineer⁃ing, 2015, 229(3): 543⁃553.

    • 10

      RAGHAV V, KOMERATH N. An exploration of radial flow on a rotating blade in retreating blade stall[J]. Journal of the American Helicopter Society, 2013, 58(2): 1⁃10.

    • 11

      RAGHAV V, KOMERATH N. The intricacies of measuring radial velocity field on a rotating disk with edgewise flow[C]//50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. Nashville, Tennessee: AIAA, 2012: 424.

    • 12

      YEO H. Investigation of UH⁃60A rotor performance and loads at high advance ratios[J]. Journal of Airc⁃raft, 2013, 50(2): 576⁃589.

    • 13

      POTSDAM M, DATTA A, JAYARAMAN B. Computational investigation and fundamental understanding of a slowed UH⁃60A rotor at high advance ratios[J]. Journal of the American Helicopter Society, 2016, 4(4): 1⁃14.

    • 14

      袁明川,杨永飞,林永峰. 高速直升机旋翼反流区桨叶剖面翼型气动特性CFD分析[J]. 直升机技术,2015(1): 1⁃5.

      YUAN Mingchuan, YANG Yongfei, LIN Yongfeng. CFD analysis on aerodynamic characteristics of blade profiles in reverse flow region of high speed helicopter rotor[J]. Helicopter Technique, 2015(1): 1⁃5.

    • 15

      CARADONNA F X, TUNG C. Experimental and analytical studies of a model helicopter rotor in hover[R]. NASA⁃TM⁃81232, 1981.

陈恺

机 构:南京航空航天大学航空学院,南京,210016

Affiliation:College of Aerospace Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing,210016, China

张震宇

机 构:南京航空航天大学航空学院,南京,210016

Affiliation:College of Aerospace Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing,210016, China

角 色:通讯作者

Role:Corresponding author

邮 箱:zyzhang@nuaa.edu.cn

作者简介:张震宇,男,讲师,E⁃mail:zyzhang@nuaa.edu.cn。

王同光

机 构:南京航空航天大学航空学院,南京,210016

Affiliation:College of Aerospace Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing,210016, China

孙静

角 色:中文编辑

Role:Editor

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图1 C⁃T旋翼不同截面压强系数分布计算值与试验值对比

Fig.1 Comparisons between calculated and experimental values of pressure coefficient at different sections of C⁃T rotor

图2 桨叶附近网格拓扑结构

Fig.2 Mesh topology around model rotor

图3 物面及边界层网格

Fig.3 Grid of wall and boundary layer

图4 桨距角及掠角定义

Fig.4 Definitions of pitch angle and sweep angle

图5 桨叶上表面压力分布极限流线图

Fig.5 Pressure and wall shear stress distribution of the upper surface of the rotor

图6 不同相位处翼型截面压强系数分布(前进比0.1,r/R=0.3)

Fig.6 Pressure coefficient distribution with advance ratio of 0.1 at r/R =0.3

图7 不同相位处翼型截面压强系数分布(前进比0.1,r/R=0.8)

Fig.7 Pressure coefficient distribution with advance ratio of 0.1 at r/R=0.8

图8 不同相位处翼型截面压强系数分布(前进比0.6,r/R =0.3)

Fig.8 Pressure coefficient distribution with advance ratio of 0.6 at r/R =0.3

图10 不同后行方位角下翼型截面压力分布云图(前进比0.6, r/R =0.3)

Fig.10 Pressure contour with advance ratio of 0.6 at r/R =0.3 at different retreating azimuth angles

图9 不同相位处翼型截面压强系数分布(前进比0.6,r/R=0.8)

Fig.9 Pressure coefficient distribution with advance ratio of 0.6 at r/R=0.8

图11 试验流动显示[8,9]

Fig.11 Tuft visualization of the upper side of the blade[8,9]

图12 前掠反流翼段上表面压力及极限流线分布

Fig.12 Pressure and wall shear stress distribution of the upper side of blade in reverse flow

图13 不同桨距角下前掠反流翼段等值涡量图

Fig.13 Iso⁃surface of vorticity magnitude at different pitch angles

图14 前掠翼段气动力系数分布曲线

Fig.14 Coefficient of lift and drag curve plots of the yawed blade in reverse flow

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  • 参考文献

    • 1

      YEO H, JOHNSON W. Aeromechanics analysis of a compound helicopter[C]//Annual Forum Proceedings⁃AHS International.[S.l.]:AHS, 2006.

    • 2

      STEIJL R, BARAKOS G, BADCOCK K. A framework for CFD analysis of helicopter rotors in hover and forward flight[J]. International Journal for Numerical Methods in Fluids, 2006, 51(8): 819⁃847.

    • 3

      LIND A H, LEFEBVRE J N, JONES A R. Experimental investigation of reverse flow over sharp and blunt trailing edge airfoils[C]//31st AIAA Applied Aerodynamics Conference. San Diego, CA: AIAA, 2013.

    • 4

      LIND A H, LEFEBVRE J N, JONES A R. Time⁃averaged aerodynamics of sharp and blunt trailing⁃edge static airfoils in reverse flow[J]. American Institute of Aeronautics and Astronautics Journal, 2015, 52(12):1⁃18.

    • 5

      LIND A H, JONES A R. Vortex shedding from airfoils in reverse flow[J]. American Institute of Aero⁃nautics and Astronautics Journal, 2015, 53(9):1⁃13.

    • 6

      LIND A H, SMITH L R, MILLUZZO J, et al. Reynolds number effects on airfoils in reverse flow[C]//53rd AIAA Aerospace Sciences Meeting. Kissimmee, Florida: AIAA, 2013.

    • 7

      LIND A H, SMITH L R, MILLUZZO J I, et al. Reynolds number effects on rotor blade sections in reverse flow[J]. Journal of Aircraft, 2016, 53(5): 1248⁃1260.

    • 8

      RAGHAV V, MAYO M, LOZANO R, et al. Evidence of vortex⁃induced lift on a yawed wing in reverse flow[J]. Proceedings of the Institution of Me⁃chanical Engineers, Part G: Journal of Aerospace Engineering, 2014, 228(11): 2130⁃2137.

    • 9

      MAYO M, RAGHAV V, KOMERATH N. Vortex flow hypothesis for a yawed rotor blade in reverse flow[J]. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineer⁃ing, 2015, 229(3): 543⁃553.

    • 10

      RAGHAV V, KOMERATH N. An exploration of radial flow on a rotating blade in retreating blade stall[J]. Journal of the American Helicopter Society, 2013, 58(2): 1⁃10.

    • 11

      RAGHAV V, KOMERATH N. The intricacies of measuring radial velocity field on a rotating disk with edgewise flow[C]//50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. Nashville, Tennessee: AIAA, 2012: 424.

    • 12

      YEO H. Investigation of UH⁃60A rotor performance and loads at high advance ratios[J]. Journal of Airc⁃raft, 2013, 50(2): 576⁃589.

    • 13

      POTSDAM M, DATTA A, JAYARAMAN B. Computational investigation and fundamental understanding of a slowed UH⁃60A rotor at high advance ratios[J]. Journal of the American Helicopter Society, 2016, 4(4): 1⁃14.

    • 14

      袁明川,杨永飞,林永峰. 高速直升机旋翼反流区桨叶剖面翼型气动特性CFD分析[J]. 直升机技术,2015(1): 1⁃5.

      YUAN Mingchuan, YANG Yongfei, LIN Yongfeng. CFD analysis on aerodynamic characteristics of blade profiles in reverse flow region of high speed helicopter rotor[J]. Helicopter Technique, 2015(1): 1⁃5.

    • 15

      CARADONNA F X, TUNG C. Experimental and analytical studies of a model helicopter rotor in hover[R]. NASA⁃TM⁃81232, 1981.

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