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首页> 外文期刊>Journal of aerospace engineering >Flow Characteristics over Double Delta Wings at Low Reynolds Numbers
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Flow Characteristics over Double Delta Wings at Low Reynolds Numbers

机译：低雷诺数双δ翼的流动特性

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Within the scope of this study, a quantitative investigation was carried out employing the particle image velocimetry (PIV) technique to determine vortical flow characteristics of 70 degrees/40 degrees, 70 degrees/50 degrees, and 70 degrees/55 degrees double delta wings (DDWs). Experiments were performed in four chordwise sections (x/c=0.5, 0.6, 0.8, and 1) at two Reynolds numbers (R=1x104 and 2.5x104) and different angles of attack (alpha=5 degrees, 10 degrees, 15 degrees, and 25 degrees). It was observed that the secondary vortex is dominant on flow characteristics of double delta wings at low Reynolds numbers. The strengths of vortices increase with increases of both the wing sweep angle and Reynolds number. Furthermore, the location of wing vortex breakdown moves farther downstream as the wing sweep angle increased. Depending on the angle of attack, Reynolds number, and the wing sweep angle, either dual (strake and wing) or triple (strake, wing, and secondary) leading-edge vortices were observed. At a Reynolds number value R=1x104 and angles of attack in the range of alpha = 15 degrees, the interactions of the vortices influence the flow structure significantly. Dominant frequencies of the vortices are detected near the shear layer formed between the strake vortex and secondary vortex, generally. Moreover, the spectral analyses indicated that bursting of the vortices causes complicated flow patterns over double delta wings, including small-scale vortices. It was found that the transverse Reynolds normal stress concentrates at chordwise sections where secondary vortices are dominant, whereas the locations of peak magnitude of vertical Reynolds normal stress coincide with the strake vortex cores.
机译：在本研究的范围内，进行了采用粒子图像速度（PIV）技术的定量研究，以确定70度/ 40度，70度/ 50度和70度/ 55度双倍三角翼的涡流特性（ DDWS）。在两个曲折的曲折号（r = 1x104和2.5x104）中在四个弦曲线部分（x / c = 0.5,0.6,0.8和1）中进行实验，以及不同的攻击角度（alpha = 5度，10度，15度，和25度）。观察到次级涡旋是在低雷诺数下双δ翼的流动特性的主导。涡流的强度随着机翼扫描角度和雷诺数的增加而增加。此外，随着机翼扫描角度的增加，机翼涡流击穿的位置进一步下游移动。根据攻击角度，雷诺数和机翼扫描角度，观察到双（施力和机翼）或三重（沟槽，翼和次级）前缘涡流。在雷诺数值r = 1x104和α<= 15度范围内的攻击角度，涡流的相互作用显着影响流动结构。通常在施力涡流和次级涡流之间形成的剪切层附近检测涡流的主导频率。此外，光谱分析表明，涡流的爆破导致双δ翼的复杂的流动模式，包括小规模涡流。发现横向雷诺正常应力集中在焦点部分的焦点部分，而垂直雷诺的峰值幅度的位置正常应力与施流涡旋芯一致。

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