Evolution of high-speed cavity flow based on PIV technology
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摘要: 空腔结构在高速来流条件下会产生复杂流动和高强度噪声,严重影响飞行器的气动特性和结构安全。通过PIV技术和动态压力测量相结合的方法,对长深比为3~10的空腔在来流马赫数0.4~0.8状态下流动噪声特性开展试验研究,着重分析了空腔长深比和来流马赫数对腔内流场结构的影响,揭示了空腔噪声强度与腔内流动的关联性。结果表明:随着长深比的增加,腔内剪切层厚度迅速增长并向腔内扩张,与空腔的撞击位置由后壁下移至底面,导致腔内流体由开式流动向闭式流动转变;来流马赫数的增大会抑制剪切层向腔内的发展,诱导主回流旋涡后移,使得流体趋于开式流动;腔内后壁总声压级的幅值与流体撞击后壁时的流向速度正相关。Abstract: In cavity structure, complex flows and high-intensity noises appear under the high-speed condition, seriously affecting the aerodynamic characteristics and structural safety of the aircraft. Through the methods of the PIV technology and dynamic pressure measurement, the cavity with a length-depth ratio of 3 to 10 is experimentally investigated in the range of Mach number 0.4 to 0.8. The influences of the length-depth ratio and Mach number on the flow field structure in the cavity are emphatically analyzed, and the correlations between the noise intensity and the flow velocity are revealed. The results show that: as the length-depth ratio increases, the thickness of the shear layer in the cavity increases rapidly and expands into the cavity, leading the impact position on the cavity to move down from the back wall to the bottom, and causing the flow type in the cavity to change from open to closed. The increase of the Mach number inhibits the shear layer from expanding into the cavity and induces the main recirculation vortex to move back and the flow type to be open. The amplitude of the overall sound pressure level is positively correlated with the flow velocity in the back of the cavity.
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Key words:
- cavity /
- PIV measurement /
- flow field structure /
- flow velocity /
- noise
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表 1 Rossiter公式估算值与试验值比较
Table 1. Camparision between estimated results of Rossiter formula and measurements
试验条件 峰值模态 St1 St2 St3 L/D=3,Ma=0.4 Rossiter 0.385 0.851 1.316 试验 – 0.883 – L/D=6,Ma=0.6 Rossiter 0.266 0.694 1.223 试验 – 0.728 1.204 L/D=6,Ma=0.8 Rossiter 0.247 0.646 1.045 试验 0.276 0.661 1.081 -
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