Numerical simulation of flow characteristics behind the aerodynamic performances on an airfoil with leading edge protuberances
Numerical simulation of flow characteristics behind the aerodynamic performances on an airfoil with leading edge protuberances
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DOI：
10.1080/19942060.2016.1277165
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发表时间：
2017-01
影响因子：
6.1
通讯作者：
Mingbo Zhao;Mingming Zhang;Jianzhong Xu
中科院分区：
文献类型：
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作者：
Mingbo Zhao;Mingming Zhang;Jianzhong Xu
本文用数值方法研究了前缘突起对翼型失速和过失速性能的影响。采用改进的延迟分离涡模拟方法（IDDES）。结果表明，在失速前区域，槽道处的流动分离是导致气动升力下降的主要原因，涡发散处的流态占主导地位，从而阐明了失速区“双周期”现象的影响。研究还发现，流动模式的变化导致了温和的失速过程。此外，为了研究非定常涡脱落的统计特性，还从另一个角度分析了相应的频谱特性，发现涡收敛处的涡脱落频率较高。最后，在过失速区的结核翼型的性能改善可以归因于由前缘突起产生的强大的流向涡。运用涡动力学的方法，描述了流向涡的产生和演化过程。结果表明：翼型表面展向压力梯度诱导了一次涡和二次涡;同时，涡的拉伸对一次涡的演化起着关键作用，一次涡的拉伸首先增强了对应于流向速度加速的涡的强度。
ABSTRACT This article presents a numerical investigation of the effects of leading-edge protuberances on airfoil stall and post-stall performance. An improved delayed detached eddy simulation (IDDES) method was adopted. As a result, to clarify the effects of ‘bi-periodic’ phenomenon around stall region, it was found that the flow separation at troughs was the main inducement of aerodynamic lift degradation within pre-stall regime and the flow pattern where vortices diverged was predominant. It was also found that the variations in flow patterns led to the gentle stall process. Furthermore, to study the statistical characteristics of unsteady vortex shedding, corresponding spectrum characteristics were also analyzed from another perspective, suggesting that the vortex shedding frequency was higher where vortices converged. Eventually, the improved performances of tubercled airfoil within post-stall regime could be attributed to the strong streamwise vortices generated by the leading-edge protuberances. Deploying the methods of vortex dynamics, the generation and evolution of the streamwise vortices were depicted. It turned out that the primary and secondary vortices were induced by spanwise pressure gradient at airfoil surface; meanwhile, vortex stretching played a key role in primary vortex evolution, which initially enhanced the strength of vortices corresponding to the acceleration of streamwise velocity.