COMPUTATIONAL AEROACOUSTICS 计算气动声学 讲义.pdf

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1、“mankbadi”

2001/11/9page259

COURSE5COMPUTATIONALAEROACOUSTICSR.MANKBADIEmbry-RiddleAeronauticalUniversity,DaytonaBeach,FL,U.S.A.,andICOMP,NASAGlennResearchCenter,Cleveland,OH,U.S.A.



“mankbadi”

2001/11/9page260

Contents1Fundamentalsofsoundtransmission26

2、11.1One-dimensionalwaveanalysis....................2621.2Three-dimensionalsoundwaves....................2641.3Soundspectra..............................2651.4Logarithmicscalesforratingnoise..................2662Aircraftnoisesources2712.1Noiseregulations......

3、......................2712.2Contributionfromvariouscomponents................2712.3Enginenoise...............................2713Methodologyforjetnoise2783.1Jetnoisephysics............................2783.2CAAforjetnoise............................2793.3Wave-

4、likesoundsource.........................2813.4Lighthill’stheory............................2853.5Kirckhoff’ssolution...........................2884Algorithmsandboundarytreatment2904.1AlgorithmsforCAA..........................2904.2BoundarytreatmentforCAA......

5、...............2935Large-eddysimulationsandlinearizedEuler2985.1Large-eddysimulation.........................2985.2LinearizedEulerequations.......................308



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COMPUTATIONALAEROACOUSTICSR.Mankbadi1Fundamentalsofsoundtran

6、smissionSoundpropagatesasawavethatevolvesasittravelsawayfromthesource.Farfromthesource,itscurvaturediminishesanditresemblesaone-dimen-sionalplanewavepropagatingradicallyoutwardwithconstantspeed,c(Fig.1).Fig.1.Soundwavespropagatingawayfromasource.Considerafluid

7、atrestwithuniformpressurep0anddensityρ0.Whenthisisperturbedbyasoundwavepandρatpositionxandtimet,theychangetop+p
(x,t)andρ+ρ
(x,t).Theratios(p
/p)and(ρ
/ρ)are00usually
1.Ifthisisthecase,theproductsoftheperturbationsinvolvedinacousticwavescanbeneglected.Consequ

8、ently,theacousticfieldresponsecanusuallybelinearized.Asoundwavetransportsenergywithitthatenergizesoureardrumstovibrate.Tonesoffrequenciesrangingbetween20–20000Hz(cyclespersecond)areaudible