# Force-controlled absorption in a fully-nonlinear numerical wave tank

## Abstract

An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank. In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain. The paper presents an extensivemore »

- Authors:

- Publication Date:

- OSTI Identifier:
- 22314894

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Computational Physics; Journal Volume: 272; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; BOUNDARY ELEMENT METHOD; CAUSALITY; COMPARATIVE EVALUATIONS; CONTROL; FEEDBACK; NONLINEAR PROBLEMS; NUMERICAL ANALYSIS; NUMERICAL SOLUTION; RANDOMNESS; TWO-DIMENSIONAL CALCULATIONS; VALIDATION; WATER WAVES; WAVE POWER

### Citation Formats

```
Spinneken, Johannes, E-mail: j.spinneken@imperial.ac.uk, Christou, Marios, and Swan, Chris.
```*Force-controlled absorption in a fully-nonlinear numerical wave tank*. United States: N. p., 2014.
Web. doi:10.1016/J.JCP.2014.04.018.

```
Spinneken, Johannes, E-mail: j.spinneken@imperial.ac.uk, Christou, Marios, & Swan, Chris.
```*Force-controlled absorption in a fully-nonlinear numerical wave tank*. United States. doi:10.1016/J.JCP.2014.04.018.

```
Spinneken, Johannes, E-mail: j.spinneken@imperial.ac.uk, Christou, Marios, and Swan, Chris. Mon .
"Force-controlled absorption in a fully-nonlinear numerical wave tank". United States.
doi:10.1016/J.JCP.2014.04.018.
```

```
@article{osti_22314894,
```

title = {Force-controlled absorption in a fully-nonlinear numerical wave tank},

author = {Spinneken, Johannes, E-mail: j.spinneken@imperial.ac.uk and Christou, Marios and Swan, Chris},

abstractNote = {An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank. In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain. The paper presents an extensive numerical validation which demonstrates the success of the method for a wide range of wave conditions including regular, focused and random waves. The numerical investigation also highlights some of the limitations of the method, particularly in simultaneously generating and absorbing large amplitude or highly-nonlinear waves. The findings of the present numerical study are directly applicable to related fields where optimum absorption is sought; these include physical wavemaking, wave power absorption and a wide range of numerical wave tank schemes.},

doi = {10.1016/J.JCP.2014.04.018},

journal = {Journal of Computational Physics},

number = ,

volume = 272,

place = {United States},

year = {Mon Sep 01 00:00:00 EDT 2014},

month = {Mon Sep 01 00:00:00 EDT 2014}

}