声学模型flueng acoustics分析教程.pptx

Fluent Acoustics Modeling ;Outline;Sound is a disturbance of the atmosphere that human beings can hear. The oscillating variations in sound pressure (called the WAVEFORM of the sound) PROPAGATE in the form of a SOUND WAVE.;Acoustics Fundamentals:Classification;Acoustics Fundamentals: Sound Pressure Level;Acoustics Fundamentals: Threshold of hearing;Acoustics Fundamentals: Noise Examples;Aero/hydro-acoustics;Industry Applications;Aeroacoustics – What do we expect?; m = m(t);Sound is a sequence of waves of pressure which propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation). During their propagation, waves can be reflected, refracted, or attenuated by the medium. All media have three properties which affect the behaviour of sound propagation: A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium: The motion of the medium itself, e.g., wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported. The viscosity of the medium. This determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.;Acoustic propagation;Acoustic propagation;Aeroacoustics: Challenges;CFD Approaches to Aeroacoustics;Direct Calculation (CAA);FLUENT 6.2 Coupling with LMS SYSNOISE;Based on a two step approach Simulate transient flow field accurately near sources using CFD Propagate noise from sources to receiver by solving wave equation analytically ‘Analogy’ refers to the notion that the complex fluid process is represented by equivalent acoustic sources Sources are assumed in a uniform fluid at rest Acoustic field at observer is described by wave equation;Acoustic Analogy Modeling;Acoustic Analogy Modeling – FW-H;RANS Based Noise Source Modeling;CFD Approaches to Aeroacoustics;Outlin