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32.3.14 Define/Models/Acoustics...

The Define/Models/Acoustics... menu item opens the Acoustic Models panel.



Acoustics Model Panel


The Acoustics Models panel allows you to set parameters related to the acoustics model. See Section  21.3 for details about the items below.

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Controls

Model   contains the option for turning on the acoustics model.

Off   disables the acoustics model.

Ffowcs-Williams & Hawkings   enables the Ffowcs Williams and Hawkings (FW-H) acoustics model. See Section  21.3.4 for details.

Broadband Noise Sources   enables the broadband noise acoustics model. See Section  21.4 for details.

Model Constants   contains parameters related to the acoustics model.

Far-Field Density   sets the value of the far-field fluid density ( $\rho_0$ in Equation  21.2-1).

Far-Field Sound Speed   sets the speed of the sound at the far-field ( $a_0$ in Equations  21.2-5 and 21.2-6).

Reference Acoustic Pressure   is used to calculate the sound pressure level in dB.

Reference Acoustic Power   is used to non-dimensionalize the acoustic power, giving the sound pressure level in dB (see Section  28.10). This parameter is equal to $4 \times 10^{-10}$ W for airborne sound and $10^{-12}$ W for underwater sound.

Reference Acoustic Intensity   is defined as $p_{\rm ref}^2/(\rho_0 a_0)$, although this quantity is not currently used by FLUENT.

Source Correlation Length   is required when sound is to be computed using a 2D flow result. The FW-H integrals will be evaluated over this length in the depthwise direction using the identical source data.

Number of Realizations   is the number of times the noise source terms will be computed through the generation of stochastic turbulent velocity field.

Number of Fourier Modes   is the number of terms in the Fourier summation from which the turbulent velocity field and its derivatives are computed.

Options   contains the parameters related to Ffowcs-Williams & Hawkings model.
Export Acoustic Source Data   enables/disables the saving of source data files.

Compute Acoustics Signals Simultaneously   enables "on-the-fly'' calculation of sound. When this option is chosen, the FLUENT console window will print a message at the end of each time step indicating that the sound pressure signals have been computed (e.g., Extracting sound signals at x receiver locations ..., where x is the number of receivers you specified). Enabling this option instructs FLUENT to compute sound pressure signals at the end of each time step, which will slightly increase the computation time.

Apply   saves the acoustics model settings.

Define Sources...   opens the Acoustic Sources panel, which allows you to specify the acoustics sources.

Define Receivers...   opens the Acoustic Receivers panel, which allows you to specify the location of the receivers.



Acoustic Sources Panel


The Acoustic Sources panel allows you to specify the acoustics sources. See Section  21.3 for details about the items below.

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Controls

Source Zones   contains a list of zones from which you can select one or more emission (source) surfaces.

Type   contains a list of all possible types of zones from which you can select one or more types of the available zones. If you select an available type of zone, the relevant zones will then be selected in the Source Zones list. If you specify any valid interior zones as source surfaces, the Interior Cell Zone Selection panel will appear.

Source Data Root Filename   is used to give the names of the source data files (e.g., acoustic_example_xxxx.asd, where xxxx is the global time-step index of the transient solution) and an index file (e.g., acoustic_example.index) that will store the information associated with the source data.

Write Frequency   allows you to control how often the source data will be written. This will enable you to save disk space if the time-step size used in the transient flow simulation is smaller than necessary to resolve the sound frequency you are attempting to predict.

No. of Time Steps per File   allows you to write the source data to multiple files, each containing the source data for a number of time steps specified by you.

Receivers...   opens the Acoustic Receivers Specification panel, which allows you to specify the location of the receivers.



Interior Cell Zone Selection Panel


The Interior Cell Zone Selection panel allows you to specify the acoustics sources. See Section  21.3.2 for details about the items below.

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Controls

Source Surface   displays the selected interior surface.

Interior Cell Zone   contains a list of two interior cell zones, from which you will select the zone that is occupied by the quadrupole sources.



Acoustic Receivers Panel


The Acoustic Receivers panel allows you to specify the location of the acoustic receivers. See Section  21.3 for details about the items below.

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Controls

No. of Receivers   allows you to specify the total number of receivers for which you want to compute sound.

Name   shows the name of the receiver. If you edit the field, the new name will take effect after you click the OK button.

X-Coord., Y-Coord., Z-Coord.   specifies the coordinates for each receiver. Note that because FLUENT's acoustics model is ideally suited for far-field noise prediction, the receiver locations you define should be at a reasonable distance from the sources of sound (i.e., the selected acoustic surface), and can fall outside of the computational domain if needed.

Signal File Name   specifies the name of the file used to store sound pressure signals for the corresponding receivers. By default, the files will be named receiver-1.dat, receiver-2.dat, etc.


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