Measuremens of Wall Shear-Stress in Skewed Turbulent Boundary Layer on a Ratating Cylinder

本研究的目的是测量轴流中高速旋转的细长圆柱体上具有倾斜速度剖面的湍流边界层中的壁面剪应力。测量壁面剪应力的方法有激光多普勒测速法、微型热线探头、壁流示踪法、热示踪法、动量积分方程法等。在微型热线探头的测量中，采用了直径为3μm的钨丝I型和V型探头，I型探头采用旋转热线法。实验几乎在长度为1200 mm的圆柱体上的湍流边界层范围内进行，在圆柱体周向速度与主流速度之比为1的情况下，无旋转和有旋转。将缓冲拟合法应用于由这些微型探头获得的近壁速度数据，估计了壁面剪应力。替换墙sh…将更多的耳应力以沿x方向积分的形式输入动量积分方程时，对该方程的平衡性进行了检验，发现它的平衡性是适度保持的，估计的壁面剪应力是相当可靠的。研究了直接从动量积分方程求取壁面剪应力的方法，并在不确定度分析的基础上，展望了如果在一个截面上重复测量10次以上，就可以估计出准确的壁面剪应力。利用激光多普勒测速仪测量壁面附近的速度分布，大致有两种方法。一种方法是在旋转系统中进行测量，为此，必须将光学系统合并到旋转体中。我们现在准备做一个旋转物体的临时模型的实验。另一种是在固定框架内进行测量，并试制了测量光学系统。总之，对LDV方法的研究还在继续。我们在这项研究中的判断是，使用壁面流动或热示踪的方法没有优势，除非这些方法获得的壁面剪应力值的精度远远优于其他方法，部分原因是这些方法的设备或传感器很难安装在高速旋转的壁上。较少

This research aims to measure the wall shear stress in the turbulent boundary layer with skewed velocity profile on a thin cylinder rotating at high speed in an axial stream. The methods to measure the wall shear stress are those to utilize Laser Doppler Velocimetry, miniature hot-wire probe, wall flow tracer, heat tracer, momentum integral equation, and so forth.In the measurement using the miniature hot-wire probe, I- and V-type probes with tungsten wire of 3 μm in diameter were used, and the rotated hot-wire method was employed for I-type probe. Experiments were made nearly in the whole range of the turbulent boundary layer on the cylinder of 1200 mm in length with no rotation and with rotation at the speed ratio, the ratio of the peripheral velocity of the cylinder to the main flow velocity, equal to one. The wall shear stresses were estimated from applying the buffer-fitting method to the data of the near-wall velocity obtained from these miniature probes. Substituting the wall sh … More ear stresses obtained into the momentum integral equation in the form integrated with respect to the x-direction, the balance of this equation was examined, and it was found that its balance was moderately kept ; the estimated wall shear stresses were fairly reliable. The method to obtain the wall shear stress directly from the momentum integral equation was investigated, and, on the basis of an uncertainty analysis, we had a prospect that if the measurement at one section were repeated more than about ten times an accurate value of the wall shear stress would be estimated.The methods using Laser Doppler Velocimetry are to measure the velocity profile in the vicinity of the wall, and there are roughly two methods. One method is to measure in the rotating system, and to do so it is necessary to incorporate the optical system into the rotating body. We are now ready to make experiment for an ad hoc model of a rotating body. The other is to measure in the stationary frame, and the measuring optical system is manufactured by trial. In a word, the study of the methods using LDV are continued.It is our judgment in this research that there is no advantage in the methods using wall flow or heat tracers unless the accuracy of the wall shear-stress value obtained by these methods is far superior to the one obtained by the other methods, partly because of the difficulty of setting the devices or sensors for these methods on the rotating wall at high speed. Less