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Aircraft Dynamics First note that it is possible to develop a very good approximation of a key motion of an aircraft(called the Phugoid mode) using a very simple balance between the kinetic and potential energies Consider an aircraft in steady, level fight with speed Uo and height ho The motion is perturbed slightly so that

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EROSPACE DYNAMiCS EXAMPLE: GWE ACCELERATIoN of THE TIP 0F认ERU0毛R人TM5Hc人AF LDk小 G For A650LUT # CCELER升T10 N UTH RES/∈ct T0wE工NERT1 AL FRAME (∈ TH IN THiS CASE) 0EFNE兵8uNcH0 f PoINTS

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\The compressibilty correction rule for thin wing The effect of compressibility in 3-D flows is somewhat less dramatic than with 2-D flows, but many of the same effects become important. Many of the same techniques for predicting linear compressibility effects work in 3-D too. For example

在3.2.2节中介绍低速风洞时,我们首次介绍了风洞 扩压器(扩压段)的作用。在那里,扩压器是试验段下 游的一段扩张管道,作用是将试验段的气体的高速度降 低至扩压器出口的很低速度。一般来说,我们可以将扩 压器定义如下:扩压器是将入流速度在其出口处降低的 任意管道(in general, we can define diffuser as any duct designed to slow an incoming gas flow to lower velocity at the exit of the diffuser)

All real substances are compressible to some greater or lesser extend. When you squeeze or press on them, their density will change. This is particularly true of gases. (所有的真实物质都是可压缩的,当我们压挤 它们时,它们的密度会发生变化对于气体尤 其是这样)

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

如果扰动比一个简单声波强,其引起的波前就会比马赫波强产生一 个与来流夹角为β的斜激波,且β>μ。这一比较在图9.4中给出。然而, 斜激波产生的物理机理与上面描述的马赫波的产生完全相同