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首页> 外文期刊>Zeitschrift fur Angewandte Mathematik und Mechanik >A Comparison of Transitional Boundary Layers in Streams with Different Flow Structures
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A Comparison of Transitional Boundary Layers in Streams with Different Flow Structures

机译：不同流动结构的河流过渡边界层比较

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摘要

The boundary layer transition is a significant problem of fluid mechanics which is not fully understood yet. Also the current industrial design models are not enough reliable to predict transition for all flow conditions especially in the case of a free-stream with disturbances of various kinds, whose are proper to the internal aerodynamic flow. More data are available on the response of transition to turbulent fluctuations than to harmonic oscillations. Especially a very pure knowledge is on the effect of mixed disturbances in the free-stream. This state of art encouraged to arrange experiments with the aim to compare the boundary layer transition in a facility with an unchangeable configuration of walls surrounding the flow field an with indepedently acting generators of free-stream velocity disturbances of different kind (random, harmonic, mixed) and various intensities. The measurements have been performed in the small wind-tunnel vacuum to'rage drive; test section 0.1 x 0.1m~2 and 0.2m length. An adjustable sonic throat controls the mass-flow through the test section. Periodic pulsations are caused by means of a rotating flap, which is inserted into the critical section. Square mesh plane grids inserted across the stream in the entrance section (x = 0) of the test section are producing turbulence fluctuations. The investigated boundary layer develops itself on a smooth steel plate-wall. Suction of boundary layers arising on the remaining walls ensures the 2D-flow character. The CTA-thermoanemometry technique with HW-probes and wall-HF-probes in conception with a four channel (SAMPLE & HOLD) digital amplitude analyser have been performed for measurement of time-, statistical- and phase-averaged statistical characteristics of the momentary velocity U and of the wall-skin-friction τ_w. More details are presented in [1].
机译：边界层过渡是流体力学的一个重要问题，目前尚未完全了解。而且，当前的工业设计模型还不足以可靠地预测所有流动条件的过渡，特别是在自由流动的情况下，各种扰动对于内部空气动力学流动是适当的。关于过渡对湍流波动的响应比对谐波振荡的响应，可获得更多数据。特别是关于自由流中混合干扰的影响的知识非常纯正。这种先进的技术鼓励安排实验，以比较流场周围壁的结构不变的设施中的边界层过渡情况，以及独立发挥作用的不同类型（随机，谐波，混合的自由流速度扰动）的发生）和各种强度。测量是在小型风洞真空中进行的。测试截面为0.1 x 0.1m〜2，长度为0.2m。可调节的声波喉管控制通过测试部分的质量流量。周期性的脉动是通过插入关键部位的旋转活门引起的。在测试部分的入口部分（x = 0）中，横穿流插入的方形网格平面网格正在产生湍流波动。研究的边界层在光滑的钢板壁上发展。剩余壁上产生的边界层吸力可确保2D流动特性。已使用带有四通道（SAMPLE＆HOLD）数字幅度分析仪的HW探头和壁式HF探头的CTA热电流法技术来测量瞬时速度的时间，统计和相位平均统计特征U和壁摩擦系数τ_w。在[1]中提供了更多细节。

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