仿沙垄气动减阻分形微纳结构及其制造技术

There are urgent requirements of aerodynamic drag reduction for large aircraft project. Traditional aircraft drag reduction technology based on aerodynamic design has been in the bottleneck. Changing the micro-structure of plane surface is an important way to breakthrough the bottleneck. We found that the feathers-like longitudinal dunes of the Kumtag desert have better performance and robustness of aerodynamic drag reduction. The research of fractal micro/nano structures imitating longitudinal dunes for aerodynamic drag reduction faces enormous challenges, due to the lack of simulation calculation and accurate modeling method, the difficulties of flexible fractal micro/nano structures manufacturing, the lack of high sensitive wind tunnel experimental testing method for viscous resistance and unclear aerodynamic drag reduction mechanism. In this project, a model of fractal micro/nano structures is proposed. The manufacturing method of micro/nano structures based on soluble intermediate layer will be researched. A shear force air flotation test platform installed in wind tunnel will be designed to measure aerodynamic shear force. The turbulent drag reduction mechanism will be illuminated, combining with the theoretical and experimental analysis. The key scientific problems include the mechanism of vortex break, the effect of geometric parameters on aerodynamic drag reduction performance and the rheological behavior of flexible material in the process of filling. The project will establish a theoretical system of fractal micro/nano structures imitating longitudinal dunes for aerodynamic drag reduction, which can provide the theoretical and technological foundation for the drag reduction of large aircraft.

气动减阻是大飞机工程的迫切需求。基于气动布局设计的传统飞机减阻技术已处于瓶颈阶段。改变飞机表面微观结构是突破瓶颈的重要方法。我们发现库姆塔格沙漠的沙垄分形结构具有较好气动减阻性能和风向鲁棒性，受此启发，我们提出仿沙垄气动减阻分形微纳结构。然而，由于缺乏仿真计算与精确建模方法，跨尺度柔性分形微纳结构制造困难，缺少高灵敏度黏性阻力风洞实验测试方法，气动减阻机理尚不明确，仿沙垄气动减阻分形微纳结构研究面临巨大挑战。本项目以沙垄为全新模仿对象，建立仿沙垄分形微纳结构模型，提出基于可溶中间转移层的分形微纳结构制造方法，提出气浮式高灵敏度黏性阻力风洞实验测试方法，阐明气动减阻机理。分形微纳结构的涡破碎机理、几何参数对气动减阻性能的影响规律及其充盈过程中柔性材料的流变机制是待研究的关键科学问题。本项目将形成仿沙垄分形气动减阻微纳结构设计、制造、测试和机理的理论体系，为大飞机气动减阻提供理论和技术基础。

气动减阻是我国大飞机工程的迫切需求。基于气动布局设计的传统飞机减阻技术已处于瓶颈阶段。通过改变飞机表面微观结构进而改变边界层流动状态是突破气动瓶颈的重要方法。本项目发现库姆塔格沙垄优异的气动减阻性能和风向鲁棒性，提出了仿沙垄多层分形减阻微纳结构，其最大减阻率较之半个世纪以来国际报道的最好水平提高了52%，提出了仿沙垄舌形减阻结构，在近四十年来的国际公开报道中，首次获得可持续到60°风向摄动偏角的微纳减阻结构；提出了基于多层混合掩模的三重光刻方法，掌握了柔性仿沙垄舌形减阻结构制造技术，实现了仿沙垄气动减阻结构的可控制备；构建了高灵敏度黏性阻力风洞实验测试系统，为微纳结构流动测量提供手段，填补了国内微纳减阻风洞测试空白，提出了气浮式高分辨力壁面微气动摩擦阻力测量方法，总剪切力分辨率可达2.5×10-6N，为目前公开报道国际风洞剪切力测量领域最高水平；深入研究了仿沙垄分形微纳结构边界层流动特性，从涡动力学的角度阐释了仿沙垄分形微结构减阻机理，提出了在气流方向变化时不同微结构气动行为的评判准则，揭示了风向参数摄动下不同微结构的气动减阻规律。本项目形成了仿沙垄分形气动减阻微纳结构设计、制造、测试和机理的理论体系，有望为新一代大飞机气动减阻提供理论和技术基础。项目相关成果共获得2019年国家技术发明奖二等奖，2021年陕西省技术发明奖一等奖，在Langmuir、ACS Applied Materials & Interface等国际著名期刊发表SCI论文15篇，已授权国家技术发明专利8项。综上，本项目按照计划执行，完成了项目任务书的论文，专利，人才培养等指标。