基于双eN方法的短舱层流转捩影响因素

发展自然层流短舱对提升现代民机的经济性和环保性具有重要意义,而对影响短舱层流转捩的因素进行研究有助于更好地开展短舱的层流设计。本文基于线性稳定性分析方法,将双e^N方法同RANS方程求解器耦合,建立了一套可同时计算T-S（Tollmien-Schlichting）波和横流（CF）驻波诱导转捩的流动转捩预测方法,通过标准椭球算例验证了该方法的正确性,进而研究了来流马赫数、雷诺数、湍流度以及迎角对短舱转捩的影响。结果表明：马赫数和迎角会带来压力梯度的明显改变从而引起转捩位置发生变化;而在此构型的高雷诺数工况下,雷诺数和湍流度对转捩位置影响相对较小,转捩位置移动的区域不超过短舱长度的5%。因此在设计阶段,在高雷诺数条件下保持层流设计要尽量避免较大的逆压梯度,保持顺压梯度。

Laminar transition influencing factors of nacelle based on double eN method

The development of natural laminar flow nacelle is of great significance to enhance the economy and environmental friendliness of modern civil transport aircrafts. The study on the laminar-to-turbulent transition influencing factors of the nacelle can better guide the design of laminar flow nacelle. Based on the linear stability analysis method, the double e^N-method coupled with the RANS equation solver is used to establish an instability prediction method that can simultaneously calculate the N-factors of the induced transition of T-S (Tollmien-Schlichting) wave and cross flow. The method is verified through the spheroid with detailed experimental data. Then the influence factors including flow Mach number, Reynolds number, turbulence, and angle of attack on the transition of the nacelle are examined. The results show that the obvious change of pressure gradient caused by Mach number and angle of attack or sideslip angle will lead to the change of transition position, whereas the Reynolds number and the turbulence intensity have relatively little influence on transition position under high Reynolds number condition, because the range of transition position movement is no more than 5% of the nacelle length. Therefore, in the design stage, it is better to maintain the positive pressure gradient on the upstream of the nacelle as large as possible.