The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
Home Program Author Index Search

Free Surface Flow and Wave Impact at Complex Solid Structures


Go-down ichd2016 Tracking Number 154

Presentation:
Session: Computational Fluid Dynamics IV
Room: Room 2
Session start: 10:30 Tue 20 Sep 2016

Robert Mayon   r.mayon@soton.ac.uk
Affifliation: University of Southampton

Zoheir Sabeur   zas@it-innovation.soton.ac.uk
Affifliation: University of Southampton

Tan Mingyi   m.tan@soton.ac.uk
Affifliation: University of Southampton

Kamal Djidjeli   kkd@soton.ac.uk
Affifliation: University of Southampton


Topics: - Hydrodynamics in ocean, coastal and estuary engineering, - Fluid-structural interactions and hydroelasticity, - Computational fluid dynamics, - Ocean and atmosphere dynamics, - Multiphase flow

Abstract:

There is great scientific interest in further understanding the underlying wave impact dynamics on solid and/or permeable structures for coastal defences. The accurate and validated simulation of the dynamics of the flow at microsecond temporal scale prior to, at and after impact is an outstanding and challenging numerical problem in CFD. When more advanced numerical modelling of free surface flow including air entrapment processes is achieved, more insight into the trends of pulse-like forces involved at impact with solid and/or porous material will enable the understanding of the mechanical stability and integrity of defence structures [1]. A comprehensive analysis of wave impact pressure signals at a solid interface was undertaken. The numerical model setup to generate these signals consisted of the classical dam-break test case simulation with the collapsing flow front impacting the interface. Compressible (and incompressible) multiphase simulations were performed using finite volume method to control the advection of the fluid within the domain. The Volume of Fluid method was used to capture the free surface evolution. Multi-modal oscillatory pressure trends were observed during the compressible simulations. The manifestation of these high frequency oscillations coincided with the entrapment of an air bubble as the plunging breaker jet re-entered the free surface of the fluid. These oscillatory signals were subsequently analysed in the frequency domain. Comparison of the frequency spectra results with both analytic methods [2] and experimental data [3] gave good agreement. The observed air bubble formation in the compressible numerical model and associated oscillatory influence on the pressure signal supports previous experimental observations and theories [4] on entrained air bubbles at impact to be the source of such pressure oscillations. References [1] Z.A.Sabeur. 1996. A Parallel Computation of the Navier-Stokes Equations for the Simulation of Free Surface Flows with the Volume of Fluid Method, In ‘Applied parallel computing’. Lecture Notes in Computer Science No 1041, Springer-Verlag, pp. 483-492, Edited by J.Dongara and J.Wasniewski. [2] Minnaert, M. 1933. XVI. On musical air-bubbles and the sounds of running water. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 16, 235-248. [3] Hattori, M., Arami, A. & Yui, T. 1994. Wave Impact Pressure on Vertical Walls under Breaking Waves of Various Types. Coastal Engineering, 22, 79-114. [4] Peregrine, D. H. 2003. Water-wave impact on walls. Ann. Rev. Fluid Mech., 35 (2003), pp. 23–43.