Application And Research On Aeroacoustic Field About Jet Based On Macro And Micro Methods

Jet aerodynamic noise causes more and more attention. This research aims to studyand analyze the jet aerodynamic sound behavior from macroscopic to microscopic aspects.FEM, FVM, LBM, MDM, and the harmonic oscillator method are adopted respectively,and make some exploration research.For the non-axisymmetric jet aerodynamic sound field of the confined space withcross flow fan, the rotating jet characteristics and room airflow organization are studiedwith the macro traditional aeroacoustic calculation method. The static pressure spectrumsand power spectral density distributions of the corresponding monitoring points areobtained by numerical analyses and experimental measure, which are induced by flow.For the axisymmetric rotating jet flow with guide vanes in pipe, the steady-unsteady-LES program is used to study the jet rotation, the pressure spectrum, soundpressure and sound transmission. It is shown that the rotor blades are the main sourcesurface. The Karman vortexes and tip leakage vortexes, passage vortexes from the leadingedge near the wall are the characteristics vortexes. Vortex-sound sources are located in theleading edges and the trailing edges. The turbulent viscosity and effective viscosity of thelateral flow field are larger than that of the middle, as exacerbated the sound of theturbulence dissipation, so sound pressure radiated focus to the environment of the axis.For the axisymmetric round jet movement, three-dimensional circular nozzle model isobtained with the infinte element method. Three high-Reynolds-number flows and twolow-Reynolds-number flows, with air impedance boundary condition, using Skylinemethod, to describe the acoustic modes corresponding to the flow field, and thecorresponding frequency-domain sound field information. Round jet show that the soundpressure spread with the acoustic impedance characteristic, showing the decoherencemeasurement. The acoustic modes of flow field overlap the nozzle structural modal in thelarge Reynolds number; cross-coupling is not obvious. Sound pressure distributions in thelarge Reynolds number display a weak non-axisymmetric structure, but the sounddistributions with the high Mach number and small Reynolds number in the near-field isspherical characteristic. In the high-frequency part the cone inverse waves from the downstream destroy the wave fronts on both sides of the axis, especially in the upstreamaround the axis.Micro jet pneumatic sound fields are obtained with the mesoscopic method. The LBMcomputing platform is created by C language. The results show that their relative values canbe more than10-9size accuracy and time price, this greatly improve the accuracy of theCFD simulation. D2G9model is more suited to expand the sound field calculations, thesound pressures with small period radius velocity disturb are better matched with theliterature results.Two-dimensional microscale grand canonical systems are simulated with Andresenflexible constraint mechanism by molecular dynamics. Throughout the flow field show thenature of the turbulence, and velocity fluctuations is random features. Lagrange density canbe easily calculated in local density and pressure, and there are2-cycle characteristics withthe time-variation of the density approximately. Stronger interaction with the wall producesa larger sound pressure, and so the random collision to the wall is an effective controlmethod.This paper proposed a composite potential flow model of three potential flows. Withinthe point source, the harmonic oscillator acting sound pressures are larger than the classicsituation, going through an imaginary vacuum belt. Within the dipole source, soundpressure is similar to dual-hat distribution. Under the action of the jet potential flow, soundpressure near the axis of the nozzle bient, there is a strong points, but only in large diametercondition, the whole trend and the values display a good match to the literaturecalculations.This study results and some exploration pave the way for further acoustic microscopicmechanism; provide a further basis for further study and possible application of technicalsupport for the macro aerodynamic sound field research in molecular and quantum levels.