前掠自然层流超临界机翼在大型民机层流减阻方面比传统后掠机翼更具优势，是21世纪航空科学技术领域一项具有革新性的技术。然而，由于以下两个关键科学问题尚未解决，制约了这一新技术的进一步研究和发展：（1） 跨声速条件下，前掠机翼抑制边界层横流不稳定性（CFI）的机理和设计准则尚不清楚；（2）缺乏能有效融入压力分布设计准则的优化设计理论和方法。与采用“有效掠角”不同，本项目首次提出采用边界层“横流压力梯度”来获得对CFI抑制机理的新认识，并给出抑制CFI的压力分布设计准则；在此基础上，将局部目标压力分布引入减阻优化设计的目标函数中，从而发展一种能够抑制CFI和TSI（流向不稳定性）扰动波增长，并合理控制激波强度的混合反设计/优化设计新方法。本项目研究的突破，不仅可为进一步研究风洞实验验证、气动弹性剪裁等问题打下基础，也可为大型民机新概念气动布局设计提供必要的理论和方法支撑。

Forward-swept natural-laminar-flow (NLF) supercritical wing is an innovative technology in the field of aeronautics towards 21st century and has great potential in drag reduction of large civil transport aircrafts compared with conventional back-swept wing. However, there are two key problems that haven’t been solved: 1) it is not sufficiently clear why a forward-swept NLF wing is more beneficial to suppress cross-flow instability (CFI) than the conventional back-swept wing; 2) currently there is no usable theory and method for the design optimization of forward-swept NLF wing to best compromise the area of NLF and the strength of shock wave. These two problems restrict the further research and development of this new technology. This project proposes to use the concept of "cross-flow pressure gradient" of a 3D boundary layer to understand to the flow mechanism of a forward-swept NLF wing for suppression of CFI. This differs from the conventional way of using the concept of "effective sweep angle", as proposed by German Aerospace Center (DLR). On this basis, a hybrid inverse/optimization method is to be proposed to design the forward-swept NLF wing that can suppress Tollmien-Schlichting instability (TSI) and CFI to ensure maintaining intensive NLF on the main wing, towards significant drag reduction of a large transport aircraft. Through solving the key problems associated with the research and development of novel forward-swept NLF wing technology, the outcome of this project is supposed to place a sound base for the further study of other key scientific and technical problems, such as the design and wind-tunnel experimental test of forward-swept NLF wings, the aeroelastic tailoring and design optimization, etc. The observed flow mechanism as well as developed numerical analysis and optimization methods in this project will provide theoretical and technical support for the future evaluation of forward-swept NLF wings when employed on a large transport aircraft.