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基于压差法测量高超声速平板局部壁面剪切应力

MEASUREMENT OF LOCAL WALL SHEAR STRESS ON A HYPERSONIC PLATE BASED ON THE PRESSURE DIFFERENTIAL METHOD

  • 摘要: 由于极端的飞行气动环境, 高超声速飞行器在真实飞行条件下的局部壁面剪切应力获取十分困难. 为了解决该问题, 基于压差法针对高超声速平板模型设计了一种新型的局部壁面剪切应力测量传感器. 该传感器由两个相邻并且具有不同直径或倾角的静压孔构成, 通过壁面剪切应力的作用使静压孔内部产生旋涡结构, 进而将流体的动量变化转化为静压孔内的压差变化. 该测试技术由于对被测边界层的干扰很小以及可靠性强的特点, 比较适合用于高超声速边界层局部壁面剪切应力测量. 由于高超声速气体的可压缩性强且测量手段没有低速下的种类多和成熟, 使该问题的理论研究变得较为复杂. 因此主要通过实验结合数值计算等手段对该测试技术进行参数化研究, 并分析了静压孔直径、倾角以及来流方位角对测试结果的影响. 结果显示, 相对于静压孔直径的变化, 改变静压孔倾角对传感器输出的压差影响更大. 分析发现, 在0°方位角时由垂直静压孔与倾斜静压孔组成的静压孔孔对的灵敏度最高, 同时传感器输出的压差与局部壁面剪切应力的线性度也较好. 此外, 还涉及传感器静压孔孔对的布局设计对传感器性能的影响.

     

    Abstract: Due to the extremely harsh aerodynamic conditions in hypersonic flight, obtaining local wall shear stress under actual flight conditions is highly challenging. To address this issue, a novel sensor for measuring local wall shear stress was designed based on the differential pressure method for a hypersonic flat plate model. The sensor consists of two adjacent static pressure holes with different diameters or inclination angles. Through the action of wall shear stress, vortex structures are generated inside the holes, thereby converting fluid momentum changes into pressure differences within the static pressure holes. This measurement technique is well-suited for determining local wall shear stress in hypersonic boundary layers due to its minimal flow disturbance and high reliability. Due to the complexity of hypersonic flow fields, thin boundary layers, and numerous variable parameters, along with fewer mature measurement techniques compared to low-speed conditions, studying the physical mechanism of this measurement method is highly challenging. The intricate flow near static pressure orifices and the mutual interference between the two holes further complicate the analysis. Therefore, a parametric study was conducted primarily through experiments combined with numerical simulations. The effects of static pressure hole diameter, inclination angle, and flow azimuth angle on the measurement results were systematically analyzed. The results indicate that varying the inclination angle of the static pressure holes has a greater impact on the sensor’s differential pressure output compared to changes in hole diameter. Analysis reveals that a hole pair composed of a vertical and an inclined static pressure hole at 0° azimuth angle achieves the highest sensitivity, along with good linearity between the output differential pressure and the local wall shear stress. Furthermore, the influence of the sensor’s static hole pair layout design on its performance is also addressed.

     

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