Department of Hydrodynamic Systems Project number: 128, 129

Contact person: Dr. György Paál (e-mail: paal@vizgep.bme.hu)

Fluid Flow Flow calculation

Finite-Volume-Method

Time domain

CFX (ANSYS)

CFS++

Acoustics Finite Element Method

Fully Coupled Solution

Time or frequency domain

Coupling Calculation of source terms on fluid mesh

Interpolating source terms onto acoustic mesh

In house code

Hybrid method for aeroacoustic simulations

Department of Hydrodynamic Systems 3

Calculation of the source terms and of the acoustic field

ji

ij

i xx

L

xc

t

2

2

2202

2

d

x

L

x

wd

nwcd

xx

wcd

tw

j

ij

iii I

20

202

2

Lighthill’s wave equation:

Where:

After multiplying with a test function w and some derivation, we arrive at the weak formulation of Lighthill's equation:

ijijjiij cpvvL 20

Department of Hydrodynamic Systems 4

Edge Tone:

plane free jet – wedge interaction

periodic vortex shedding

dipole sound source

model for outside rear-view mirrors or woodwind instruments (project #128)

Cavity Tone:

flow over a cavity

unstable shear layer

interaction with the downstream edge

complex sound source

e.g. flow over gaps on body of a car or sunroof windo(project #128, 129)

Examples for two well-known aeroacoustic configurations

Department of Hydrodynamic Systems 5

Edge tone results

Department of Hydrodynamic Systems 6

Cavity tone