基于气流场扰动机理挖掘的仿生非光滑车表气动减阻效能研究

Reducing aerodynamic drag is of great importance for vehicle to possess better dynamic performance and lower fuel consumption. A new method to reduce the aerodynamic drag by applying specific non-smooth films at different parts of the vehicle body is proposed which can be used at several stages including vehicle body in design, design finalized or even after manufactured. The research is based upon the mining of disturbance mechanism in flow field and the contents include: 1) To establish the theory for flow field analysis that can accurately describe the characteristics of turbulent flow around vehicle body covered with non-smooth films. 2) To reveal different disturbance behavior with the influences of different type, dimension and distribution of non-smooth structure on a given near-wall flow field as well as it's forming conditions. 3) To study the basic rules about the influences between the vehicle aerodynamic performance and the disturbance caused by non-smooth films. 4) To set up the optimal design criteria of non-smooth films covered on vehicle body focusing on reducing the aerodynamic drag coefficient after analyzing the drag reduction efficiency of non-smooth films; 5) To carry out the experiment method research on accurately measure the near-wall flow condition and the flow field around vehicle body with wind tunnel test. The above research results may provide a design guide to construct drag reduction non-smooth films on vehicle body and also provide a theoretical basis for turbulence control in multi-disciplinary research fields with various objectives.

降低汽车的空气阻力是改善其动力性能、减小油耗的重要手段。本项目探索一种降低汽车空气阻力的车身设计新理论，即在车身设计过程中、设计方案定型甚至制造完成后，在车身表面不同部位加设具有减阻效果的特定非光滑结构表面覆膜，达到改善汽车空气动力性能和节能降耗的目的。本项目从挖掘非光滑结构对气流场的扰动机理出发，研究非光滑表面覆膜车身外流场的特性并建立流场分析理论模型；揭示非光滑结构形状、参数、布局对特定近壁面气流场所产生的不同扰动作用及形成条件；探索非光滑表面覆膜的扰动对汽车空气动力学性能影响的基本规律；分析车身非光滑覆膜的减阻效能并建立以降低汽车空气阻力系数为目标的非光滑覆膜构造理论；同时开展对近壁面流动状态、车身外流场进行精确测量的风洞实验方法研究。上述研究成果用以指导车身减阻非光滑覆膜的设计和优化，也为多领域多目标的湍流控制提供理论依据。

汽车气动阻力系数每降低10％，可以节省燃油7％，当汽车速度为80 km/h时，消耗燃油所产生的功率60%用来克服气动阻力。作为能源消耗的重要因素，改善汽车气动性能是减少能耗、节约能源、改善动力性能的有效途径。项目提出一种降低汽车气动阻力的新方法，依据自然界中的非光滑形态，将优化后的非光滑结构布置在汽车表面，以达到减阻降耗的效果。在数值仿真的基础上，建立环形低速风洞实验平台，进行了变异卵圆形、仿新月形沙丘形非光滑结构的PIV实验；在低雷诺数风洞对MIRA标准汽车模型进行了气动性能测试，同时设计了汽车风洞地面效应模拟系统；研究了非光滑结构对流场的扰动机理，扰动行为对流体阻力特性、汽车空气动力性能的影响；开展了非光滑表面高速列车气动性能研究、非光滑表面水下航行器减阻研究、仿生耦合表面气动性能研究、非光滑表面耐磨性研究等相关研究。项目取得一些重要结论：来流速度为24 m/s时，变异卵圆形非光滑单元体减阻率可达10%，来流速度为30 m/s时，新月形沙丘非光滑单元体摩擦减阻率达33.63%。相较于光滑表面汽车，表面非光滑的汽车的减阻率可达5.45%，非光滑车表有利于汽车尾部流场的改善，可以减小汽车压差阻力。凹坑型表面的高速列车减阻率可达8.16%，覆盖组合式非光滑表面的水下航行器减阻率可达5.2%。项目提出了固定地板——底部抬升相结合的汽车风洞实验地面效应模拟方法，提出了在固定平板前端开具气流引导槽的方法以减小平板上方的气流边界层厚度。项目研发了非光滑表面耐磨性能摩擦磨损试验机，发现非光滑表面结构平整作用、储屑作用、变形作用。项目重点围绕非光滑表面结构对汽车外流场产生的减阻效能开展研究工作，提出了一种绿色、有效的汽车减阻降耗方法，探究了非光滑结构对流体动力学性能影响的机理，为进一步开展相关流场分析和实验研究奠定了基础。