## A COMPARISON OF TRANSIENT INFINITE ELEMENTS AND TRANSIENT KIRCHHOFF INTEGRAL METHODS FOR FAR FIELD ACOUSTIC ANALYSIS

## Abstract

Finite element analysis of transient acoustic phenomena on unbounded exterior domains is very common in engineering analysis. In these problems there is a common need to compute the acoustic pressure at points outside of the acoustic mesh, since meshing to points of interest is impractical in many scenarios. In aeroacoustic calculations, for example, the acoustic pressure may be required at tens or hundreds of meters from the structure. In these cases, a method is needed for post-processing the acoustic results to compute the response at far-field points. In this paper, we compare two methods for computing far-field acoustic pressures, one derived directly from the infinite element solution, and the other from the transient version of the Kirchhoff integral. Here, we show that the infinite element approach alleviates the large storage requirements that are typical of Kirchhoff integral and related procedures, and also does not suffer from loss of accuracy that is an inherent part of computing numerical derivatives in the Kirchhoff integral. In order to further speed up and streamline the process of computing the acoustic response at points outside of the mesh, we also address the nonlinear iterative procedure needed for locating parametric coordinates within the host infinite elementmore »

- Authors:

- Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Computational Solid Mechanics and Structural Dynamics

- Publication Date:

- Research Org.:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA)

- OSTI Identifier:
- 1426920

- Report Number(s):
- SAND2011-6829J

Journal ID: ISSN 0218-396X; 464659

- Grant/Contract Number:
- AC04-94AL85000

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of Computational Acoustics

- Additional Journal Information:
- Journal Volume: 21; Journal Issue: 02; Journal ID: ISSN 0218-396X

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 42 ENGINEERING; 97 MATHEMATICS AND COMPUTING; Far-field acoustics; infinite elements; Kirchhoff integral; parallel implementation

### Citation Formats

```
WALSH, TIMOTHY F., JONES, ANDREA, BHARDWAJ, MANOJ, DOHRMANN, CLARK, REESE, GARTH, and WILSON, RILEY. A COMPARISON OF TRANSIENT INFINITE ELEMENTS AND TRANSIENT KIRCHHOFF INTEGRAL METHODS FOR FAR FIELD ACOUSTIC ANALYSIS. United States: N. p., 2013.
Web. doi:10.1142/S0218396X13500069.
```

```
WALSH, TIMOTHY F., JONES, ANDREA, BHARDWAJ, MANOJ, DOHRMANN, CLARK, REESE, GARTH, & WILSON, RILEY. A COMPARISON OF TRANSIENT INFINITE ELEMENTS AND TRANSIENT KIRCHHOFF INTEGRAL METHODS FOR FAR FIELD ACOUSTIC ANALYSIS. United States. doi:10.1142/S0218396X13500069.
```

```
WALSH, TIMOTHY F., JONES, ANDREA, BHARDWAJ, MANOJ, DOHRMANN, CLARK, REESE, GARTH, and WILSON, RILEY. Mon .
"A COMPARISON OF TRANSIENT INFINITE ELEMENTS AND TRANSIENT KIRCHHOFF INTEGRAL METHODS FOR FAR FIELD ACOUSTIC ANALYSIS". United States. doi:10.1142/S0218396X13500069. https://www.osti.gov/servlets/purl/1426920.
```

```
@article{osti_1426920,
```

title = {A COMPARISON OF TRANSIENT INFINITE ELEMENTS AND TRANSIENT KIRCHHOFF INTEGRAL METHODS FOR FAR FIELD ACOUSTIC ANALYSIS},

author = {WALSH, TIMOTHY F. and JONES, ANDREA and BHARDWAJ, MANOJ and DOHRMANN, CLARK and REESE, GARTH and WILSON, RILEY},

abstractNote = {Finite element analysis of transient acoustic phenomena on unbounded exterior domains is very common in engineering analysis. In these problems there is a common need to compute the acoustic pressure at points outside of the acoustic mesh, since meshing to points of interest is impractical in many scenarios. In aeroacoustic calculations, for example, the acoustic pressure may be required at tens or hundreds of meters from the structure. In these cases, a method is needed for post-processing the acoustic results to compute the response at far-field points. In this paper, we compare two methods for computing far-field acoustic pressures, one derived directly from the infinite element solution, and the other from the transient version of the Kirchhoff integral. Here, we show that the infinite element approach alleviates the large storage requirements that are typical of Kirchhoff integral and related procedures, and also does not suffer from loss of accuracy that is an inherent part of computing numerical derivatives in the Kirchhoff integral. In order to further speed up and streamline the process of computing the acoustic response at points outside of the mesh, we also address the nonlinear iterative procedure needed for locating parametric coordinates within the host infinite element of far-field points, the parallelization of the overall process, linear solver requirements, and system stability considerations.},

doi = {10.1142/S0218396X13500069},

journal = {Journal of Computational Acoustics},

number = 02,

volume = 21,

place = {United States},

year = {2013},

month = {4}

}