《安德森空气动力学》PPT课件

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1、CHAPTER9OBLIQUESHOCKANDEXPANSIONWAVES斜激波和膨胀波凹角上的斜激波：流动偏转角θ(turningangle,deflectionangle)：固体壁面的偏转角激波角β(shockangle)：波前流动方向与激波夹角当超声速流动的流动方向被迫突然变化时，就会产生斜激波。尖楔上的斜激波：流动偏转角θ：固体壁面的偏转角激波角β：波前流动方向与激波夹角尖楔半顶角δ(wedgehalf-angle)：对尖楔，δ=θ=Acrosstheobliqueshockwave,theMachnumb

2、erdiscontinuouslydecreases,andthepressure,density,andtemperaturediscontinuouslyincrease.Acrosstheexpansionwave,theMachnumbercontinuouslyincreases,andthepressure,density,andtemperaturecontinuouslydecrease.•thephysicalmechanismthatcreateswavesinasupersonicflow超音

3、速流中产生波的物理机理Iftheupstreamflowissubsonic,thedisturbanceshavenoproblemworkingtheirwayupstream,thusgivingtheincomingflowplentyoftimetomoveoutofthewayofthebody.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。Theinformationispropagatedupstreamatapproximatelythelocalsp

4、eedofsound.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。（弱扰动）iftheupstreamflowissupersonic,thedisturbancescannotworktheirwayupstream;rather,atsomefinitedistancesfromthebody,thedisturbancewavespileupandcoalesce,formingastandingwaveinfrontofthebody.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

5、离处聚集并接合，形成一静止波。情形一：静止物体产生扰动的传播超音速流中产生波（激波和膨胀波）的物理机理duetothepropagationofinformationviamolecularcollisionsandduetothefactthatsuchpropagationcannotworkitswayintocertainregionsofthesupersonicflow.通过分子碰撞引起的信息传播和这种传播不能到达超音速流中某些区域。Thedisturbancecanpropagatetothewhol

6、espace.Thedisturbancecannotpropagate（扩散）tothespacebeforethesource.Thedisturbancecanonlypropagatetospecialdomain.情形二：运动的物体产生的声波波振面以1.4倍当地马赫数运动的声源，突破声障，形成马赫波马赫波和马赫角(9.1)马赫波马赫角补充：超音速流动的影响域和依赖域是一对顶锥（doublecone）μμ影响域Influencedomain影响域InfluencedomainμμM>1影响域Influenc

7、edomain依赖域dependencedomainIfthedisturbancesarestrongerthanasimplesoundwave,thenthewavefrontbecomesstrongerthanaMachwave,creatinganobliqueshockwaveatanangletothefreestream,whereβ>μ.ThiscomparisonisshowninFig.9.4.However,thephysicalmechanismcreatinganobliqueshoc

8、kisessentiallythesameasthatdescribedabovefortheMachwave.如果扰动比声波强（强扰动波）,其引起的波振面就会比马赫波强,产生一个与来流夹角为β的斜激波,且β>μ。这一比较在图9.5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。EXAMPLE9.1Asupersonicairplanei