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

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.