Coupled BEM acoustic

This code provides an implementation to address the acoustic scattering problem of two penetrable scatterers under a BEM philosophy, using planar triangular meshes. Tested under Julia 1.1. Details from the theoretical formulation are in the work: Boundary element method to analyze acoustic scattering from a coupled swimbladder-fish body configuration.

A preprint version of this work exists at the arXiv

Required packages

The Julia packages SpecialFunctions, DelimitedFiles, Distributed and LinearAlgebra are required, so make sure you have them installed in your Julia environment.

Using the code

The code is organized in one main file

jul_main.jl

which must be loaded previously to any script-run. This file loads all the necessary files (which reside in the src directory). In this file the user can configure its parallel environment (i.e. how many processors he has in the machine running Julia). The line n_cores defines how many cores are added to the main processor. For example, in a machine with 4 cores n_cores=3 is the allowable maximum value that makes sense. I recommend using as many cores as you can.

Once loaded the main file, by typing

include("jul_main.jl")

you are ready to execute the two-spheres example provided (backscattering from two penetrable spheres) that corresponds to Fig. 3 (see details in the arXiv or the JSV paper). This is accomplished by typing

include("Script_Shells_bem_K.jl")

During the script execution some informative text will be displayed at the screen. Lines as

Calculating the frequency : 15206.520916753354 ::: 9 of 10

allow to see the current stage of the calculation and how much work remains to be done (i.e. frequencies to be calculated).

When done (with 3 [email protected] GHz cores took me one hour to calculate ten points) the resulting TS versus frequency is saved in the out directory. This result can be seen in the following figure, compared against the benchmark solution.

The parameters from the execution can be altered in the script file. The meshes directory contains the STL format meshes corresponding to the scatterers.

General considerations

• This code is not friendly end-user software.
• This code is a research code aimed to implement acoustic scattering.
• I am not a programmer, I'm a physicist that solves stimulating physical problems aided with the computer. There is a gap in between.
• Concerning scattering, a mesh is an appropriate representation of the scattering object only in a range of frequencies. Make sure that a proper relation between the acoustic wavelength and the triangle's longitude in the mesh is fulfilled (some details in the paper).

Memory considerations

• This BEM formulation ensambles a matrix of size 2(N+L) x 2(N+L), where N and L are the sizes (numbers of triangles) of the meshes. Bearing in mind this constraint because by default each element is a 128 bits complex (64 bits for each, real and imaginary parts). Avoid a matrix size which surpasses your physical memory.

Citing the code?

If you have used the code and find useful for you research work, please cite the article

Boundary element method to analyze acoustic scattering from a coupled swimbladder-fish body configuration.

A bibtext entry follows:

@article{gonzalez2020boundary,
  title={Boundary element method to analyze acoustic scattering from a coupled swimbladder-fish body configuration},
  author={Gonzalez, Juan D and Lavia, Edmundo F and Blanc, Silvia and Maas, Martin and Madirolas, Adri{\'a}n},
  journal={Journal of Sound and Vibration},
  pages={115609},
  year={2020},
  publisher={Elsevier}
}

Final words

Thank you for tryng the code. Other example scripts will be uploaded soon! Any suggestions and comments will be welcome at [email protected].