Aerodynamics of biplane and tandem wings at low Reynolds numbers
Aerodynamics of biplane and tandem wings at low Reynolds numbers
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低雷诺数下双翼机翼和串联机翼的空气动力学
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
I. Gursul
中科院分区：
文献类型：
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作者：
Robin E. Jones;D. Cleaver;I. Gursul
进行实验以研究 100,000 低雷诺数下两翼配置的空气动力特性。机翼模型是半展弦比为二的矩形平板。机翼之间的交错从 ΔX/c = 0 到 1.5 变化；对于双翼飞机和串联配置，间隙分别从 ΔY/c = 0 到 2 和 ΔY/c = -1.5 到 1.5 变化，脱角固定为 0°。升力、阻力、气动效率和功率效率比表明，对于小入射角，与单翼相比，性能下降。然而，对于单翼失速后攻角，对于许多具有非零间隙（即 ΔY/c ≥ 0）的配置，升力性能会提高，失速会显着延迟。对于固定攻角，机翼之间存在最佳间隙，使总升力达到最大。粒子图像测速测量表明，性能改进在很大程度上依赖于翼间流动的强度以及前翼前缘和后缘分离的剪切层与后翼的相互作用。发现对于某些两翼配置来说，不稳定力会增强。后翼失速和非失速状态之间的切换以及合并和不同尾流之间的切换被证明具有高流动不稳定性和大升力波动。
Experiments were performed to investigate the aerodynamic characteristics of two-wing configurations at a low Reynolds number of 100,000. The wing models were rectangular flat plates with a semi-aspect ratio of two. The stagger between the wings was varied from ∆X/c = 0 to 1.5; the gap was varied from ∆Y/c = 0 to 2 and ∆Y/c = −1.5 to 1.5 for biplane and tandem configurations, respectively, with the decalage angle fixed at 0°. Lift, drag, aerodynamic efficiency and power efficiency ratios show that for small incidence angles, performance compared with the single wing is degraded. However, for single-wing post-stall angles of attack, lift performance improves and stall is delayed significantly for many configurations with nonzero gap, i.e., ∆Y/c ≥ 0. For a fixed angle of attack, there are optimal gaps between the wings for which total lift becomes maximum. Particle image velocimetry measurements show that performance improvement relies heavily on the strength of the inter-wing flow and the interaction of the separated shear layers from the leading edge and trailing edge of the leading wing with the trailing wing. Unsteady forces are found to intensify for certain two-wing configurations. A switching between the stalled and unstalled states for the trailing wing as well as a switching between the merged and distinct wakes is shown to have high flow unsteadiness and large lift fluctuations.