文档介绍：CHAPTER 9 OBLIQUE SHOCK AND EXPANSION WAVES
斜激波和膨胀波
引言
第八章我们讨论了正激波, 本章我们讨论斜激波, 及超音速流场中的另一个重要特征——膨胀波。
Wave angle: 激波角, 激波与激波上游来流的夹角。
A normal shock wave is simply a special case of the general family of oblique shocks, namely, the case where the wave angle is 900.
β
Across the oblique shock wave, the Mach number discontinuously decreases, and the pressure, density, and temperature discontinuously increase.
θ: Deflection angle (偏转角)
Across the expansion wave, the Mach number continuously increases, and the pressure, density, and temperature continuously decrease.
Hence, an expansion wave is the direct antithesis of a shock wave.
因此,膨胀波是激波的一个正相反的对应物。
Oblique shock and expansion waves are prevalent in two- and three-dimensional supersonic flow. These waves are inherently two-dimensional in nature, in contrast to the one-dimensional normal shock waves discussed in . That is, in Fig. and b, the flow-field properties are a function x and y. The purpose of the present chapter is to determine and study the properties of these oblique waves.
斜激波和膨胀波在二维、三维超音速流动中是很普遍的。这些波在本质上是二维的,与第八章讨论的一维正激波相反。即,,流场特性是x 、 y的函数。本章的目的就是确定和研究这些斜波(斜激波和膨胀波)的性质。
• What is the physical mechanism that creates waves in a supersonic flow? 超音速流中产生波的物理机理是什么?
If the upstream flow is subsonic , as shown in , the disturbances have no problem working their way upstream, thus giving the ing flow plenty of time to move out of the way of the body.
,如果上游是亚音速的, 扰动可以毫不困难地传播到远前方上游,因此,给了来流足够的时间以绕过物体。
The information is propagated upstream at approximately the local speed of sound.
物体存在的信息以近似等于当地音速的速度传播到上游去。
On the other hand, if the upstream flow is supersonic, as shown in , the disturbances cannot work their way upstream; rather, at some finite distances from the body, the disturbance waves pile up and coalesce, forming a standing wave in front of the body.
在另一方面,,如果上游是超音速的,扰动不能一直向上游传播,而是在离开物体某一距离处聚集并接合,形成一静止波。
Hence, the physical generation of