超声速双层翼翼型的阻力特性研究

The study on the drag characteristic of supersonic biplane

以布兹曼双层翼为基础,采用基于压力梯度自适应的非结构网格求解欧拉方程的计算流体力学(CFD)方法,计算分析了双层翼翼型的厚度和翼面间距对阻力特性的影响。在马赫数为1.7的情况下,由于激波的反射和干涉,超声速双层翼翼型的阻力系数仅为0.00189,为相同厚度菱形翼型的1/15。本文通过进一步的研究发现:减少翼型厚度对于双层翼翼型设计马赫数的阻力系数有一定的影响,且与超声速状态相比,厚度对于亚声速状态的阻力影响更大,厚度减少20%,亚声速状态的阻力系数减少可达60%以上;翼面间距对阻力特性的影响相对复杂,设计马赫数之前的阻力系数与翼面间距成反比,而设计马赫数之后的阻力系数与翼面间距成正比。在此基础上,基于激波的反射及干涉效应,提出了一种双设计状态的双层翼翼型,在最佳设计点之前,双层翼之间的激波/膨胀波会有两次反射,使翼型前后的压力基本相同,阻力系数出现一次下降。随着马赫数的增加马赫角减少,激波经过一次反射就能使翼型前后的压力基本相同,使翼型达到最佳设计状态。计算结果表明,双设计状态双层翼能够使双层翼翼型在两个设计点都具有较低的阻力系数。

In this paper Computational Fluid Dynamics(CFD) method is used to calculate and analyze how the thickness and plates range affect drag characteristic of biplane based on busemann biplane. The results show that the drag coefficient of biplane at designed condition is 0.00189 owing to wave-cancellation effect which is only about 1/15 of diamond airfoil's drag coefficient. Compared with supersonic condition, thickness of airfoil has a greater influence on drag characteristic of biplane at subsonic condition. As thickness of airfoil reduces 20%, its drag coefficient will decrease more than 60% at subsonic condition. Plates range has a more complex influence on drag characteristic of biplane. Before the designed Mach number, drag coefficient of airfoil is inversely proportional to the plates range. On the contrary, drag coefficient of airfoil is proportional to the distance between plates after the designed Mach number. Generally speaking, both thickness and spacing will affect the designed Mach number of biplane. Based on the reflection and interference of shock, a biplane with double designed conditions is proposed. The computational results show that this type of biplane has a relative low drag coefficient at two points: Ma∞=1.52 and Ma∞=2.1.