Noise pollution

New tools for numerical simulations

First aerodynamic-aero-acoustic chaining created with an exchange surface crossed by a turbulent flow (“LES” CFD - “Euler” CAA).

A gauche le calcul pur CFD
On the left the pure “LES” CFD – structured mesh computation
on the right the acoustic radiation in non-structured “Euler” CAA

Acoustic propagation calculations, by solving Euler* equations, have been successfully chained with an LES* simulation of a hot jet at Mach 0.7.

This first aerodynamic-aero-acoustic chaining, created with an exchange surface crossed by a turbulent flow, opens the way to future complete aero-acoustic computations for configurations that are today impossible using non-coupled CFD* (Computational Fluid Dynamics) and CAA*

*: see below

CFD - Computational Fluid Dynamics
CFD consists in the study of the movements of a fluid, or their effects, by the numerical solving of the equations that govern the behavior of the fluid (the complete equations are Navier-Stokes equations). CFD is used to obtain all the instantaneous information (speed, pressure, concentration, etc.) for each point of a computational domain.

CAA - Computational Aero-Acoustics.
Aero-acoustics is the study of acoustic phenomena associated with aerodynamic flows. CAA consists in the study, using numerical methods, of the noise radiation of an aero-acoustic source, or sound wave propagation in a flow.

Euler Equations
Invented by Euler in 1755, these equations apply in the case of a perfect fluid, that is to say a non-viscous fluid with no thermal conductivity. The fluid may be incompressible or compressible. These equations, solved in an appropriate manner, can correctly simulate the propagation of acoustic waves for industrial configurations.

LES - Large Eddy Simulation
This is a numerical technique for predicting and analyzing turbulent flows. The spatial scales of a flow that are larger than an arbitrarily fixed limit are determined by computation, while the others are taken into account by means of a statistical model called a sub-mesh model. LES is used for the calculation of large scales of turbulence while it simply models the smallest (which are the most costly to calculate). LES is a compromise offering a high degree of precision with complex “industrial” geometries for acceptable computation costs (on a supercomputer).

Back to the list