湍流边界层的湍流参数测量和研究

利用ＤＡＮＴＥＣ三维激光多普勒测速仪对水槽壁面边界层的湍流参数进行了测量和分析，并与经典实验曲线做了比较，同时就摩擦速度的计算与涡粘系数的分布曲线展开了讨论。     

湍流附面层壁面摩擦应力的测量方法

 本文讨论了不可压和可压湍流附面层壁面摩擦应力的测量方法,对Presto管、Stanton管、底层隔板、表面热膜和计算Preston管法进行了校准和测量比较。     

壁面温度控制对平板边界层影响的数值研究

通过对零压力梯度的平板边界层流动施加温度控制,展开壁面温度控制对平板层流边界层和湍流边界层影响的研究,探索温度控制对平板转捩雷诺数和壁面摩擦阻力的影响规律。采用带有转捩模式的三方程湍流模型对平板边界层流动进行数值模拟,重点考察了壁面摩阻系数、平板转捩雷诺数、湍流边界层流动随壁面温度变化的规律。计算结果表明在壁面温度从288 K 增大到432 K 时,边界层转捩雷诺数增大约36%,表面摩擦阻力减少约9.6%。研究分析表明：加热控制使层流区域温度边界层内粘性作用增强,雷诺切应力和湍动能减小,流动更加稳定;而湍流区域边界层内粘性底层中速度梯度和粘性切应力减小,导致壁面处摩擦切应力减小。因此壁面加热控制可以延迟边界层转捩,减小湍流区摩阻系数,并减小平板摩擦阻力。     

对安放直机翼的平板测定三维湍流边界层的低、亚音速特性

 本文介绍了在低速和亚音速来流情况下,对一安放着直机翼的平板,在其附体流部分所作的三维湍流边界层特性的测量;讨论了压强梯度和流线曲率对壁面律、尾流律以及湍流应力和混合长分布的影响。 测量结果表明:适用于二维湍流边军层的Coles速度型和混合长分布规律都应考虑当地的压强梯度和流线曲率的影响才能用于三维流情况。本实验测得的三维湍流边界层的亚音速特性在性质上与低速特性无显著区别。     

SSG模型在压缩拐角激波/湍流边界层干扰模拟中的应用

采用非线性方案模化雷诺应力再分配项的二阶矩雷诺应力输运模型——SSG模型和两方程线性涡粘模型SST模型,对24°高雷诺数二维压缩拐角激波/湍流边界层相互干扰流动进行数值模拟。通过在壁面压力分布、壁面摩擦阻力系数分布、截面速度分布及分离区大小等方面与实验数据比较,综合评估了上述两种模型模拟该问题的能力。结果表明:两种湍流模型在上述各方面都取得了与实验较为一致的结果,但相比较而言,除SST模型在流动再附后对壁面摩擦阻力系数分布的模拟更接近实验值外,SSG模型结果在上述其他方面均更接近实验值。本文工作为压缩拐角激波/湍流边界层干扰这类流动数值模拟的湍流模型选择提供了参考。     

沟槽壁湍流多尺度相干结构实验研究

应用热线测速技术,对沟槽壁面平板湍流边界层的减阻机理进行了实验研究.测量了风洞中并排放置的沟槽壁面平板及光滑壁面平板湍流边界层在不同雷诺数下不同法向位置的瞬时流向、法向速度分量的时间序列信号.运用流向速度分量信号的多尺度子波系数辨识壁湍流多尺度相干结构,用条件采样和相位平均技术提取了壁湍流多尺度相干结构喷射和扫掠时流向速度分量、法向速度分量和雷诺应力分量的相位平均波形.分析了沟槽壁面平板及光滑壁面平板湍流边界层中多尺度相干结构的持续时间、条件相位平均波形等特征.对沟槽壁面平板及光滑壁面平板湍流边界层多尺度相干结构的多种统计平均特征进行了比较,从壁湍流多尺度相干结构控制的角度研究了沟槽壁面平板湍流边界层的减阻机理.      

方管内超声速湍流流动及旋涡的测定技术研究

本文在Ｍ∞＝１．５８及湍流边界层厚度δ／Ｄ＝０．１条件下，用实验方法研究了管长Ｌ／Ｄ＝６方管内的三维超声波湍流场及其沿程的发展和反压的影响，讨论了壁面边界层沿流向和展向的主要变化特征；指出管内横截面的三维静压场特点，文中最后探讨了超声速湍流流动的方管内旋涡的测量技术。     

在直机翼与平板连接处测定分离区内外的低、亚音速湍流边界层特性

本文介绍了在低速和亚音速来流情况下,对一竖立着机翼的平板,在其连接处的分离区内外所作的三维湍流边界层测量。低速实验测出沿二条不同站位线共十个测量站位上的三个平均速度分量分布和六个湍流应力分量分布。亚音速情况下,对分离区内外的二个站位作了同样测量。测量结果表明,气流的分离导致产生一个马蹄形旋涡,它是影响分离区内外三维湍流边界层特性的重要因素。文中还讨论了实验数据的处理方法,分析了有压力梯度和流线曲率影响的实验结果。     

超疏水壁面湍流边界层减阻机理的TRPIV实验

利用高时间分辨率粒子图像测速（TRPIV）技术,开展超疏水壁面材料湍流边界层减阻机理的实验研究.在循环水槽中,对超疏水壁面和亲水壁面湍流边界层瞬时速度矢量场的时间序列进行了实验测量.得到了同一来流速度（0.17m/s）下超疏水壁面和亲水壁面湍流边界层的平均速度、湍流度及雷诺切应力沿法向的分布规律.提出了空间多尺度局部平均涡量的概念,并以此为特征量检测壁湍流发卡涡展向涡头的中心位置.用条件采样及空间相位平均技术提取了不同法向位置发卡涡展向涡头周围流向脉动速度和流线的空间拓扑,对发卡涡展向涡头的俯仰角进行了对比,并从鞍点-焦点动力系统的角度分析了发卡涡展向涡头附近的流线拓扑特征.研究表明：雷诺数约为13500时,相比亲水壁面,超疏水壁面实现了10.1%的减阻.超疏水壁面平均速度明显增大,雷诺切应力减小,流向湍流度减弱,发卡涡展向涡头俯仰角较小,近壁区相干结构的发展受到抑制.     

利用PIV技术对非光滑表面湍流边界层的实验研究

利用在线式 Ｐ Ｉ Ｖ 系统在低速风洞中对两种非光滑表面：阵列涡发生器表面和波纹壁面的湍流边界层进行了实验测量。观察到了壁面几何形状的改变对非光滑表面湍流边界层拟序结构的产生和发展的影响：阵列涡发生器表面（１０ｍ ／ｓ）湍流边界层内有明显的双剪切带状结构,外剪切带状结构接近边界层的外边界,小尺度的涡在内剪切带状结构的附近产生;波纹壁面（２０ｍ ／ｓ）湍流边界层内涡的尺度比较小。并在相同的壁面几何形状条件下,在不同的流动工况下,研究了非光滑表面对湍流边界层拟序结构的影响。实验结果表明,壁面几何形状的改变对外层的大尺度横向涡的产生和发展有明显的影响;而这种影响效果在不同的流动工况下相差很大。     

飞行中附面层转捩的流动显示与测量技术

阐述了在飞行试验中测量附面层转捩的重要性;介绍了四种在飞行试验中显示和测量机翼附面层转捩的方法;给出了Ｆ－１４Ａ飞机用热膜,附面层耙,液晶和表面总压管等方法测量附面层转捩的结果,并对以上四种测量结果者了对比分析,指出了各自的优缺点,说明热膜法能精确地确定飞行状态下机翼附面层转捩位置;附面层也能比较精确地进行测量,且能提供与表面摩擦仍关的参数,液晶法能人出附面层转捩的整体图形,表面总压管不能确切地指     

应用表面热膜测定NACA0012翼型边界层转捩区位置的实验研究

 本文所述的实验研究,是将自行研制的M-I型表面热膜用于测定NACA0012翼型上表面的转捩区的实验。当翼型迎角α改变时转捩区位置随之改变,见图3。实验证明这种技术是令人满意的。     

基于荧光油膜的全局表面摩阻测量技术研究

针对表面摩阻传统测量方法的单点性和间接性,探索了荧光油膜进行全局表面摩阻分布的直接测量方法.建立了表征荧光油膜厚度与表面摩阻之间关系的油膜控制方程,引入附加约束和积分最小化方法,采用变分迭代方法求解表面摩阻分布.研制了可用紫外光激发的荧光油膜,采用紫外光源和高分辨率CCD相机,建立荧光油膜表面摩阻测量硬件系统.针对特定的三角翼模型进行了表面摩阻分布测量实验,获得了高分辨率的表面摩阻分布和相对幅值分布,并与文献理论进行比较分析.实验结果与理论分析完全一致,表明了基于荧光油膜的全局表面摩阻测量技术的有效性.     

超临界层流机翼边界层及气动特性分析

高空长航时无人机设计巡航状态的雷诺数较小,黏性边界层对气动特性的影响较大。详细分析了雷诺数对机翼边界层和气动力的影响,用数值方法对超临界层流机翼三维层流-转捩-湍流混合边界层特性进行了研究,分析比较了高空小雷诺数和中空大雷诺数情况下机翼三维边界层的特性,尤其是边界层转捩点位置、表面摩阻和气动特性的雷诺数效应。研究表明雷诺数对于高空无人机机翼边界层厚度、摩擦阻力和升阻比影响较大;对层流机翼的转捩点位置和升力系数影响较小;自然层流机翼技术可以应用于高空无人机设计。     

吹吸扰动对壁湍流边界层摩擦阻力的影响

对风洞中平板湍流边界层施加局部周期性吹吸扰动,并用IFA-300热线风速仪测量了其近壁区域不同法向位置瞬时速度的时间序列信号.利用湍流边界层对数律平均速度剖面,计算湍流的壁面摩擦阻力.对平板湍流脉动速度信号用子波分析进行多尺度分解,通过条件采样以及相位平均的方法获得不同尺度下的相干结构波形和能量分布,来研究吹吸扰动对平板湍流边界层的摩擦阻力的影响.结果表明,扰动使得窄缝附近流动阻力增加,而下游区域流动阻力减小.      

Control of a decelerating boundary layer. Part 1: Optimization of passive vortex generators

The control of boundary layer separation on the suction side of an airfoil at high angle of attack has been renewed by the possibilities of active control. Nevertheless, such an active control needs a deep understanding of the flow to manipulate and of the actuating flow, both being 3D and unsteady. For that purpose, a model experiment has been designed in the frame of a coordinated European project called AEROMEMS, with a simpler (2D) geometry and with a dilatation of the scales in order to be able to characterize the actuation flow. This model is a bump in a boundary layer wind tunnel, which mimics the adverse pressure gradient on the suction side of an airfoil at the verge of separation. The present contribution describes preliminary tests done to optimize standard passive devices before testing active systems. The optimization was done with hot film shear stress probes, the characterization with hot wire anemometry and PIV. The results show quantitatively the improvement brought by the passive devices in terms of skin friction. They also show the mechanism which is at the origin of this improvement. The next step of the project is to replace passive devices by synthetic jets.     

Control of a decelerating boundary layer. Part 2: Optimization of slotted jets vortex generators

In the first part of this contribution [G. Godard, M. Stanislas, Control of a decelerating boundary layer. Part 1: Optimization of passive vortex generators, Aerospace Sci. Technol. 10 (3) (2006) 181–191], an optimization of passive vortex generators was performed in an adverse pressure gradient boundary layer. The model used was a bump in a boundary layer wind tunnel, which mimics the adverse pressure gradient on the suction side of an airfoil at the verge of separation. The present contribution describes the next step of the study: a test campaign was performed in the same facility to optimize slotted jets devices with both continuous and pulsed blowing. The optimization was done using hot film shear stress probes. The results show quantitatively the improvement brought by the slotted jets devices in terms of skin friction increase. They also show that the tested devices are less effective than equivalent passive devices.     

测量旋涡脱落频率的实验研究

本文提出了一种由表面摩擦测量旋涡脱落频率的方法,阐述了其原理,给出了实验研究的结果,可作为涡街式流量计测量旋涡脱落频率的一种途径。     

高超声速飞行器相关的摩擦阻力直接测量技术

摩擦阻力是高超声速飞行器气动力的重要组成部分,也是制约高超声速飞行器发展的重要因素,因而对摩擦阻力的准确测量就显得尤为重要。简要介绍了近年国内外与高超声速相关的摩擦阻力直接测量技术的发展状况,同时对中国航天空气动力技术研究院白行研制的两套摩擦阻力测量装置作了介绍,并指出应变式摩阻天平技术是测量摩擦阻力的有效途径之一。文中给出了这两种结构形式摩阻天平的静校结果及其在高超声速风洞中的试验结果,并对结果进行了讨论。     

Accurate measurements of local skin friction coefficient using hot-wire anemometry

The practicality and accuracy of many existing methods of local skin friction measurement suffer when the boundary layer flow under consideration is non-canonical. Such shortcomings are exacerbated in three-dimensional flows, by the necessity to map local c_f over a wider area in order to characterise fully the contribution to global skin friction. These problems have led the authors to seek novel experimental methods of c_f measurement. The technique proposed herein utilises velocity measurements made using hot-wire anemometry combined with accurate positioning of the sensor element in respect to the test surface. In essence it is proposed that the local skin friction can be evaluated via a single velocity measurement made at a known wall-normal distance within the linear region of the viscous sublayer. This technique relies on accurate probe positioning, and two methods of achieving this are outlined. A study of the hot-wire characteristics in near-wall proximity has revealed a previously unnoticed feature corresponding to probe–wall contact. It is shown that this anomaly can be used as a positional flag to accurately locate the aerodynamic origin of the hot-wire sensor. A second technique using a laser triangulation displacement sensor is also outlined. Both positional techniques are shown to offer positioning to a sufficient level of accuracy for the proposed c_f measurement technique. Single-point local c_f measurement is tested experimentally, demonstrating the improved repeatability and standard error as predicted by initial error analysis. In this way it is shown that a single $\text{90}\text{s}$ velocity sample coupled with accurate wall positioning can define local c_f to a standard error of σ_cf≈1.0%. Analysis of error contributions reveals that longer sampling periods can realise even greater accuracy. The proposed technique is also used to measure local c_f in a three-dimensional boundary layer where micro-vortex generators have introduced large-scale spanwise distortions. This is an example of an application in a non-canonical boundary layer, and initial results show that the method is capable of providing repeatable comparative spanwise-averaged skin friction results to within approximately ±1%. The technique is immediately applicable to researchers using hot-wire anemometry in low Reynolds number flow over electrically non-conductive test surfaces.