Using ultraFluidX FW-H

The FW-H tool provided by ultraFluidX 2024.1 requires ultraFluidX results as input data. Specifically, the tool post-processes data that is either sampled in the volume field via a monitoring surface (porous formulation), or from object surfaces using the partial surface output option (solid formulation). The data generated by ultraFluidX is read by the FW-H tool from the respective output folders. (Further information on how to set up an ultraFluidX run including the required surface outputs can be found in the ultraFluidX user guide section on <output>.)

All input parameters for the FW-H tool are controlled via an .xml input file. The path to the far-field microphone/receiver positions, i.e. coordinates stored in .csv format, has to be indicated to the FW-H tool as.

An example case is located in the installation folder fwh/examples/monopole. This folder contains an input deck (fwh_deck.xml), a set of ultraFluidX sample results on a monitoring surface enclosing an acoustic source, and a .csv file indicating the microphone locations that the FW-H tool will use as receiver positions.

Launching the FW-H Tool

The FW-H tool can be launched in the command line by calling the executable (location depending on installation) and providing the name of an input deck:

>> fwh/scripts/fwh input_deck.xml

Launching without further options will run the FW-H tool in a multi-threaded mode with the number of threads matching the number of cores on the hardware.

The user can also indicate a specific number of threads when launching the tool:

>> fwh/scripts/fwh -t [integer number of threads] input_deck.xml

FW-H Outputs

The FW-H tool produces screen output of the OASPL (Overall Sound Pressure Levels, $O A S P L = 20 \log_{10} (\frac{p'_{r m s}}{p_{r e f}})$ ) predicted at each microphone plus two output files per specified parts in a folder indicated by the user in the .xml file. These files contain the pressure time histories predicted at the microphone location as a function of time.

The difference between the two files is the chosen reference time:

The sync file contains the pressure at each microphone using the same reference time, i.e., t = 0s corresponds to the time at which the closest microphone receives a signal from the closest surface element of the input file. All other microphones start recording at this same instant implying their signals contain initial zeros until they receive a signal. Trailing zeros are present if no more signal is received.
The notsync file uses a local reference time for each microphone, such that only the “usable” data is written. One-point frequency domain post-processing (r.m.s., Sound Pressure Levels) should be performed on the notsync file.