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
Possible to qualitatively characterize source strength average flow pressure fluctuation magnitude in
Flow pressure fluctuations on a solid surface in the flow cause acoustic pressure fluctuations to be radiated out
Turn on UDF after transient simulation。