Experimental investigation of transonic and supersonic flow over a sphere for Reynolds numbers of 10^3-10^5 by free-flight tests with schlieren visualization
Experimental investigation of transonic and supersonic flow over a sphere for Reynolds numbers of 10^3-10^5 by free-flight tests with schlieren visualization
复制标题
通过使用纹影可视化的自由飞行测试对雷诺数为 10^3-10^5 的球体上的跨音速和超音速流动进行实验研究
DOI：
10.1007/s00193-019-00924-0
复制
发表时间：
2020
期刊：
影响因子：
2.2
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Nagata;T.;Noguchi;A.;Nonomura;T.;Ohtani;K.;and Asai;K.
在本研究中，使用弹道靶场对雷诺数在 3.9 × 103 和 3.8 × 105 之间的球体以及马赫数在 0.9 到 1.6 之间的自由飞行试验进行了测试，并使用纹影技术研究了孤立球体上的可压缩低雷诺数流动。流动可视化是在低压条件下使用小球体（最小直径为 1.5 毫米）进行的，以产生可压缩的低雷诺数流动。此外，还获得了球体附近流动的时间平均图像，并与之前雷诺数在 50 至 1000 之间的数值结果进行了比较。实验结果阐明了跨音速和超音速流动下雷诺数为 103-105 时的激波结构、再循环区域和尾流结构。结果表明：(1)尾流振荡幅度随着自由飞行马赫数的增加而衰减； (2)即使在恶劣条件下纹影图像不清楚的情况下，使用奇异值分解也可以提取尾流结构的模式，并识别出尾流结构中的不同模式； (3)雷诺数对分离点影响不大，但再循环区的长度随着雷诺数的减小而增加； (4)再循环区末端的尾流直径随着马赫数的增加而减小。
In this study, free-flight tests of a sphere for Reynolds numbers between 3.9 × 103and 3.8 × 105and free-flight Mach numbers between 0.9 and 1.6 were conducted using a ballistic range, and compressible low-Reynolds-number flows over an isolated sphere were investigated with the schlieren technique. The flow visualization was carried out under low-pressure conditions with a small sphere (minimum diameter of 1.5 mm) to produce compressible low-Reynolds-number flow. Also, time-averaged images of the flow near the sphere were obtained and compared to previous numerical results for Reynolds numbers between 50 and 1000. The experimental results clarified the structure of shock waves, recirculation region, and wake structures at the Reynolds number of 103–105under transonic and supersonic flows. As a result, the following characteristics were clarified: (1) the amplitude of the wake oscillation was attenuated as the free-flight Mach number increased; (2) use of singular value decomposition permitted extraction of the mode of the wake structure even when schlieren images were unclear due to severe condition, and different modes in the wake structure were identified; (3) the Reynolds number had little effect on the separation point, but the length of the recirculation region increased as the Reynolds number decreased; and (4) the wake diameter at the end of the recirculation region decreased as the Mach number increased.