!!!FLUENT在气动噪声问题上的处理方法

已经发布了气动噪声模块

SPL (dB):0 20 30 40 50 60 70 80 90 100 110 120

Source Acoustic

Source Intensity, I

Farfield

Surface

Sound Power = ∫IdA

Acoustic

Pressure, p(t)

Pa

p p

rms µ20,log

2=

Frequency range (20 Hz ~ 20,000 Hz)

Temporal resolution for acoustics is often orders of

To radiate the acoustic pressure to the farfield

analogy)

Solve the flow using NS equation to capture sound

Advantages of the two step procedure Separate length scales. NS equation deals ONLY with short

Sound is induced by fluid flow with its fluctuating

Include solid surfaces and density fluctuation

V i=0)

Lighthill-Curle’s solution for acoustic pressure

used this formulation for a rotating

The Sears function provides a description of the unsteady aerodynamic response of a body due to

Correlate the flow parameters to noise levels.

showed relations for acoustic power:

CFD Acoustic Modeling Options

Output Phenomena

Generate LES Solution

Airflow over a flat-plate with

30 mm

n Plate Plate

Perform transient LES turbulent 2D analysis in

Acoustic Pressure and

Acoustic pressure variation with time

For the present flow, SPL = 108 (dB)

)

/()(2m W f p Φ)

()(dB f p ΦPeak at f = 3434 Hz

Power Spectral Density

Surface Dipole Strength

measures local contribution

)

Local contribution to acoustic pressure can be

Transient simulations can be used with Lighthill-

L = 1m, D = 0.267m (L/D = 3.75)

Cavity Flow Methodology

Acoustic calculation

Acoustic Pressure Traces

Cavity Acoustic Pressure

Summary

Unsteady flow predicted with FLUENT is used as the source term

Muffler Frequency Response

A. J. Torregrosa, & A. Gil, Dept. of Thermal

Engines, Polytechnic University of Valencia

Muffler Acoustics Methodology

2D Axisymmetric, 10,000 cells

3D w/ 1 Plane of Symmetry, 60,000 cells

incident wave

3D Muffler Pressure Isosurfaces

Pressure IsoSurfaces at several frequencies f=95.15 Hz f=266.42 Hz f=342.54 Hz

f=685.08 Hz

f=1046.65 Hz

Transmission Loss Calculations

TL de TT2110016

TL de TT2110016

Response Conclusions

Calculation Method has been defined to

Wind Noise = Pressure fluctuations caused by

Primary sources of Wind Noise are

•Leakage wave propagation simulated with FLUENT

Examples: Door gap cavities, wiper well, cavities in