broadband-noise

Tutorial:Broadband Noise Modeling

Purpose

The purpose of this tutorial is to provide guidelines and recommendations for the basic setup and solution procedure for solving an acousticsfield generated from a sedan car using the broadband noise model.The problem is initially solved for steady state,and then the broadband acoustic model is included in the calculation to perform postprocessing.

Prerequisites

This tutorial assumes that you are familiar with the user interface,basic setup and solution procedures in FLUENT.This tutorial does not cover mechanics of using the broadband noise model,but focuses on setting up the problem for a sedan car and performing postprocessing.

It also assumes that you have a basic understanding of aeroacoustic physics.

If you have not used FLUENT before,it would be helpful tofirst review FLUENT6.2User’s Guide and FLUENT6.2Tutorial Guide.

Problem Description

The problem involves a sedan car model as shown in Figure1.The car is traveling at70 miles per hour.You will study only the acousticsfield generated by the motion of the car to highlight the noise source on the sedan body,therefore the mirrors and the wheels of the car are ignored.

Figure1:The Sedan Car

Broadband Noise Modeling

Preparation

1.Copy the meshfile,sedan-acoustics.msh from the inputfile into your working di-

rectory.

2.Start the3D version of FLUENT.

Setup and Solution

Step1:Grid

1.Read the meshfile,sedan-acoustics.msh.

File−→Read−→Case...

2.Check the grid.

Grid−→Check...

3.Keep default scale for the grid.

Grid−→Scale...

4.Display the grid.

Display−→Grid...

Figure2:Grid Display

Broadband Noise Modeling Step2:Models

1.Keep the default solver settings.

Define−→Models−→Solver...

2.Enable the standard k-epsilon turbulence model.

Define−→Models−→Viscous...

Step3:Materials

Define−→Materials...

1.Keep the default selection of air in the Materials panel.

Step4:Operating Conditions

Define−→Operating Conditions...

1.Keep the default operating conditions.

Step5:Boundary Conditions

Define−→Boundary Conditions...

1.Set the boundary conditions for velocity inlet(inlet).

(a)Under Zone,select inlet.

The Type will be reported as velocity-inlet.

(b)Click Set...to open the Velocity Inlet panel.

Broadband Noise Modeling

i.Specify a value of31for Velocity Magnitude.

ii.Select Intensity and Length Scale in the Turbulence Specification Method drop-down list.

iii.Specify a value of2and0.35for Turbulence Intensity and Turbulence Length Scale respectively.

2.Set the boundary conditions for pressure outlet(outlet)as shown in the panel.

3.Keep the default boundary conditions for other walls.