Investigation of alternative drag-reduction strategies in turbulent boundary layers by using wall forcing

这项研究的目的是在一个涉及几种相互支持的计算方法和范例的交互程序中，研究利用横流壁面强迫在飞行雷诺数下实现持续和经济上有价值的摩擦阻力减少的可行性。虽然该方案的重点是基本的湍流物理及其与壁面阻力相互作用的预测，但总的来说，该方案与一项重要的民用航空目标密切相关，即到2020年每乘客公里的排放量减少50%。该计划将把涉及直接数值模拟和高分辨率大涡模拟的研究与两种基于线性化条纹模型的方法结合起来，一种是由帝国理工学院开发的，另一种是由洛克比(沃里克)开发的。总的策略是使用全分辨率格式来深入了解与摩擦阻力相关的近壁湍流机制，产生与校准相关的输入到线性化条纹模型中，并研究该模型对于用全分辨率方法检验的一系列驱动参数的有效性。拟议的研究是基础性的，很好地补充了EPSRC的现役飞机计划，该计划以实际为导向。最终目的是在线性化条纹模型的基础上推导出一种预测程序，该程序允许量化不同配置的横流壁面压力对飞行雷诺数时阻力的影响。该计划得到了欧洲宇航防务集团的财政支持。

The aim of this research is to investigate, in an interactive programme involving several mutually supportive computational approaches and paradigms, the feasibility of achieving sustained and economically worthwhile frictional-drag reduction at flight Reynolds numbers using cross-flow wall forcing. While the emphasis of the programme is on the fundamental turbulence physics and the prediction of its interaction with wall drag, in general, the programme is closely associated with an important civil aviation goal, namely the reduction in emissions per passenger km by 50% by 2020. The programme will combine studies involving direct numerical simulations and highly-resolved large eddy simulations with two approaches based on linearised streak modelling, one developed by Chernyshenko (Imperial College) and the other by Lockerby (Warwick). The general strategy is to use the full-resolution schemes to gain insight into the near-wall turbulence mechanisms associated with frictional drag, to generate calibration-related input into the linearised streak modelling and to investigate the validity of this modelling for a range of actuation parameters examined with the full-resolution approaches. The proposed research is fundamental in nature and complements well EPSRC's Active Aircraft programme, which is practically-oriented. The ultimate objective is to derive a prediction procedure, based on linearised streak modelling that allows the effect of different configurations of cross-flow wall forcing on drag at flight Reynolds numbers to be quantified. The programme is financially supported by EADS.