Investigation of separation mechanism for airfoil leading edge flow at low Reynolds number
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摘要: 采用高精度有限差分格式,对来流雷诺数为1.0×104,攻角为3°的二维翼型流动进行了直接数值模拟,研究了低雷诺数下翼型前缘流动的分离机制,描述了分离涡系的相互作用规律.计算结果表明:前缘椭圆弧靠近叶身位置存在吸力峰,流动在吸力峰内强逆压梯度的作用下发生分离;翼型上表面形成了包含驻留涡、脱落涡和二次涡的涡系结构,其尺度随时间不断变化,具有强烈的非定常性;表面压力分布曲线可以较好的描述翼型边界层流动.Abstract: A direct numerical simulation (DNS) around a 2-D airfoil was carried out through high order finite difference scheme, the Reynolds number based on chord is 1.0×104, the angle of attack is 3°. Via analyzing the quasi-periodic numerical solutions, the separation mechanism of leading edge flow at low Reynolds number is investigated, and the rules of vortices interaction are summarized. Numerical results indicate that there exists suction spike on airfoil near elliptical leading edge, separation occurs on the effect of strongly adverse pressure gradient of suction spike. Vortices structure including primary vortex, shed vortex and secondary vortex forms on the airfoil surface, its scale varies with time and it is absolutely unsteady. Surface pressure distribution can be used to describe the airfoil boundary layer flow well.
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Key words:
- non-steady flow /
- airfoils /
- low Reynolds number /
- separation /
- direct numerical simulation
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