Transdisciplinary Research for Silent Supersonic Aircraft by Integrating Computation and Experiment

阻碍商用运输机超音速飞行的根本问题之一是产生强烈的音爆。超音速飞行的飞机产生的冲击波的强度是飞机重量和所占体积的直接函数；很难充分减少由更重和更大的传统超音速运输(SST)配置产生的冲击波，以达到地面可接受的音爆水平。我们的团队首先重新分析了经典的Busemann双翼飞机配置，以了解其使用现代计算流体动力学(CFD)工具的基本波对消概念。然后，我们设计了一种二维超音速双翼飞机，它不仅在设计条件下表现出所需的气动特性，而且性能优于零厚度平板翼型。(零厚度平板翼型被认为是在超音速下最有效的单翼型。)此外，我们还研究了双翼飞机在设计马赫数和非设计状态下的性能。在计算研究的同时，我们还进行了一系列的实验。这里进行的第一个实验是用气枪进行的音爆实验。成功捕获了N波。第二个实验是利用本研究新建的进气风洞装置进行的二维风洞试验。此外，还利用现有的风洞进行了常规风洞试验。这些实验揭示了重要的非设计流动特征，有待于用CFD进一步研究。主要研究成果是对超音速双平面理论的发展。双翼结构可以消除超音速物体产生的冲击波。它可以是未来超音速运输的一种非常规和创新的概念。

One of the fundamental problems preventing commercial transport aircraft from supersonic flight is the generation of strong sonic booms. The strength of the shock waves generated by an aircraft flying at supersonic speed is a direct function of both the aircraft's weight and its occupying volume; it has been very difficult to sufficiently reduce the shock waves generated by the heavier and larger conventional supersonic transport (SST) configuration to meet acceptable at-ground sonic-boom levels.Our team first re-analyzed the classic Busemann biplane configurations to understand its basic wave cancellation concept using modern Computational Fluid Dynamics (CFD) tools. We then designed a two-dimensional (2-D) supersonic biplane that not only shows the desired aerodynamic characteristics at its design condition, but also outperforms a zero-thickness flat-plate airfoil. (Zero-thickness plat-plate airfoils are known as the most efficient monoplane airfoil at supersonic speeds.) Also we studied biplane performance not only at their design Mach numbers but also at off-design conditions. We extended the analysis to 3-D wing configurations as well.In parallel to the computational studies, we carried out series of experiments. The first experiment conducted here was the sonic boom experiment using gas gun. The N-wave was captured successfully. The second experiment was the 2 D wind tunnel test using Indraft Wind Tunnel Facility newly constructed in this research. In addition, conventional wind tunnel tests were conducted using existing wind tunnels. These experiments revealed important off-design flow features to be further studies by using CFD.The main research result is the development of the supersonic biplane theory. Biplane configuration allows canceling shock waves created by supersonic objects. It can be unconventional and innovative concept for future supersonic transport.