Abstract The flow around three simplified models of side-view mirrors for automobiles is experimentally investigated by means of Robotic particle tracking velocimetry (PTV). The measurements are performed coupling a coaxial volumetric velocimeter with time-resolved three-dimensional (4D) Lagrangian Particle Tracking (LPT) data analyzed with the Shake-The-Box (STB) algorithm. Helium-filled soap bubbles were used as tracers in the wind tunnel experiment to achieve the measurement volume needed for characterizing the flow structures around and behind the models of automobile side-view mirrors. The aspect ratio of all the models is kept constant to H/W = 2. The effect of a slant angle at the front and the reduction of cross section at the model root are specifically investigated respectively using model 2 and model 3. In model 1 which represents generic geometry having semi-cylinder-spherical shape, the extension of the recirculation zone shrank in the z direction due to the free-end effect. When the flow is developing downstream, a vortex pair inclines towards the ground plane due to the downwash effect. This streamwise vortex shows a dipole distribution. In model 2 the trailing vortex does not fall toward downstream because a base vortex with opposite sign formed under the trailing vortex. This prevents the downwash flow from reaching the ground plane. In model 3, a streamwise vortex is generated from a strong upwash flow, which generates a short trailing vortex up to x/H = 1. This occurs because the vortex that was formed from the top and side end is suppressed and destroyed. The leg of the reverse U-shape structure of model 1 is almost perpendicular to the ground plane. However, in models 2 and 3, vortex shedding near the bottom is delayed, and an arch vortex is slightly slanted toward the model body.

中文翻译：

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汽车侧视镜模型周围流动的机器人 PTV 研究

摘要 利用机器人粒子跟踪测速仪（PTV）对三种简化的汽车侧视镜模型周围的流动进行了实验研究。测量是将同轴体积测速仪与时间分辨三维 (4D) 拉格朗日粒子跟踪 (LPT) 数据结合使用 Shake-The-Box (STB) 算法进行分析来进行的。在风洞实验中，充氦肥皂泡被用作示踪剂，以实现表征汽车侧视镜模型周围和后面的流动结构所需的测量体积。所有模型的纵横比保持恒定为H/W = 2。 分别使用模型2和模型3具体研究了模型前部倾斜角和模型根部横截面减小的影响。在代表具有半球形状的通用几何形状的模型 1 中，由于自由端效应，再循环区的延伸在 z 方向上收缩。当流动向下游发展时，由于下洗效应，涡对向地平面倾斜。这个流向涡流显示出偶极分布。在模型 2 中，尾涡不会向下游下降，因为尾涡下方形成了一个符号相反的基涡。这可以防止下洗流到达地平面。在模型 3 中，一个流向涡流是由强大的上洗流产生的，它会产生一个短的尾涡，直到 x/H = 1。这是因为从顶部和侧端形成的涡流被抑制和破坏了。模型 1 的倒 U 形结构的腿几乎垂直于地平面。然而，在模型 2 和模型 3 中，靠近底部的涡旋脱落被延迟，并且拱形涡旋稍微向模型主体倾斜。