Plunging Wave Impact on a Wall

2008 ◽  
Author(s):  
Jian-Jun Shu
Keyword(s):  
Free Surface ◽  
Vertical Wall ◽  
Rigid Wall ◽  
Small Time ◽  
Breaking Wave ◽  
Wave Impact ◽  
Third Order ◽  
Offshore Engineering ◽  
Surface Profiles ◽  
Engineering Industries

The intention of this paper is to study impact force of an oblique-angled slamming wave acting on a rigid wall. In the present study the analytical approach is pursued based on a technique proposed by the author. A nonlinear theory in the context of potential flow is presented for determining accurately the free-surface profiles immediately after an oblique breaking wave impingement on the rigid vertical wall that suddenly starts from rest. The small-time expansion is taken as far as necessary to include the accelerating effect. The analytical solutions for the free-surface elevation are derived up to the third order. The results derived in this paper are of particular interest to the marine and offshore engineering industries, which will find the information useful for the design of ships, coastal and offshore.

scholarly journals An Analytical Approach for the Two-Dimensional Plunging Breaking Wave Impact on a Vertical Wall with Air Entrapment

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 58
Author(s):  
Theodosis D. Tsaousis ◽  
Ioannis K. Chatjigeorgiou
Keyword(s):  
Free Surface ◽  
Velocity Potential ◽  
Mixed Boundary ◽  
Dimensional Space ◽  
Vertical Wall ◽  
Breaking Wave ◽  
Linear Potential ◽  
Two Dimensional ◽  
Wave Impact ◽  
Air Pocket

This study investigates an idealized formulation of the two-dimensional impact of a breaking wave on a vertical impermeable wall. An overturning-like wave is assumed, which is close to the concept of a plunging breaker. It is assumed that during the collision an air pocket is entrapped between the wave and the wall. The air pocket width is assumed to be negligible and the compression effects are omitted. The problem is considered in the two-dimensional space (2D) using linear potential theory along with the small-time approximation. We use a perturbation method to cope with the linearized free-surface kinematic and dynamic boundary conditions. We impose the complete mixed boundary value problem (bvp) and we solve for the leading order of the velocity potential. The problem derived involves dual trigonometrical series and is treated analytically. The main assumption made is that, within the air pocket, the pressure is zero. Results are presented for the velocity potential on the wall, the velocity, and the free-surface elevation.

On the Validity and Sensitivity of CFD Simulations for a Deterministic Breaking Wave Impact on a Semi Submersible

2018 ◽  
Author(s):  
Henry Bandringa ◽  
Joop A. Helder
Keyword(s):  
Free Surface ◽  
Absorbing Boundary Conditions ◽  
Implicit Time ◽  
Breaking Wave ◽  
Computational Domain ◽  
Wave Impact ◽  
Time Step ◽  
Cfd Simulations ◽  
Detailed Model ◽  
Run Up

To assess the integrity and safety of structures offshore, prediction of run-up, green water, and impact loads needs to be made during the structure’s design. For predicting these highly non-linear phenomena, most of the offshore industry relies on detailed model testing. In the last couple of years however, CFD simulations have shown more and more promising results in predicting these events, see for instance [1]–[4]. To obtain confidence in the accuracy of CFD simulations in the challenging field of extreme wave impacts, a proper validation of such CFD tools is essential. In this paper two CFD tools are considered for the simulation of a deterministic breaking wave impact on a fixed semi submersible, resulting in flow phenomena like wave run-up, horizontal wave impact and deck impacts. Hereby, one of the CFD tools applies an unstructured gridding approach and implicit free-surface reconstruction, and uses an implicit time integration with a fixed time step. The other CFD tool explicitly reconstructs the free surface on a structured grid and integrates the free surface explicitly in time, using a variable time step. The presented simulations use a compact computational domain with wave absorbing boundary conditions and local grid refinement to reduce CPU time. Besides a typical verification and validation of the results, for one of the CFD tools a sensitivity study is performed in which the influence of small variations in the incoming breaking wave on the overall results is assessed. Such an analysis should provide the industry more insight in the to-be-expected sensitivity (and hence uncertainty) of CFD simulations for these type of applications. Experiments carried out by MARIN are used to validate all the presented simulation results.

scholarly journals Numerical Modeling and Simulation of Wave Impact of a Circular Cylinder during the Submergence Process

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaozhou Hu ◽  
Yiyao Jiang ◽  
Daojun Cai
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Wave Load ◽  
Wave Impact ◽  
Rans Equations ◽  
Wave Slamming ◽  
Surface Profiles ◽  
Numerical Wave

Wave slamming loads on a circular cylinder during water entry and the subsequence submergence process are predicted based on a numerical wave load model. The wave impact problems are analyzed by solving Reynolds-Averaged Navier-Stokes (RANS) equations and VOF equations. A finite volume approach (FV) is employed to implement the discretization of the RANS equations. A two-dimensional numerical wave tank is established to simulate regular ocean waves. The wave slamming problems are investigated by deploying a circular cylinder into waves with a constant vertical velocity. The present numerical method is validated using other numerical or theoretical results in accordance with varying free surface profiles when a circular cylinder sinks in calm water. A numerical example is given to show the submergence process of the circular cylinder in waves, and both free surface profiles and the pressure distributions on the cylinder of different time instants are obtained. Time histories of hydrodynamic load on the cylinder during the submergence process for different wave impact angles, wave heights, and wave periods are obtained, and results are analyzed in detail.

scholarly journals On wave motion in a two-layered liquid of infinite depth in the presence of surface and interfacial tension

1994 ◽  
Vol 35 (3) ◽  
pp. 302-322 ◽  
Author(s):  
P. F. Rhodes-Robinson
Keyword(s):  
Free Surface ◽  
Interfacial Tension ◽  
Vertical Wall ◽  
Small Time ◽  
Underlying Assumption ◽  
Wave Source ◽  
Infinite Depth ◽  
Surface And Interface ◽  
All Solutions ◽  
Progressive Waves

AbstractIn this paper various two-dimensional motions are determined for waves in a stratified region of infinite total depth with a free surface containing two superposed liquids, allowing for the effects of surface and interfacial tension. The fundamental set of wave-source potentials for the two layers is used to construct the set of slope potentials that produce discontinuous free-surface and interface slopes. The latter potentials are then utilized to obtain the potentials for waves due to both heaving vertical plates and incident progressive waves against a vertical wall. The underlying assumption of small time-harmonic motion pertains, described by a pair of velocity potentials for the two layers satisfying coupled linearized boundary-value problems, and all solutions are obtained in terms of their matching basic solutions. The technique for applying Green's theorem in the two layers is developed for use with the wave-source potentials, which themselves are found to obey a generalised reciprocity principle. Familiar results for a single liquid of infinite depth are hereby extended, but the new feature emerges of there being two types of progressive waves in all solutions. For ease of presentation the solutions are obtained for a particular relationship between surface and interfacial tension.

scholarly journals Hydroelasticity effects on water-structure impacts

2020 ◽  
Vol 61 (9) ◽  
Author(s):  
T. Mai ◽  
C. Mai ◽  
A. Raby ◽  
D. M. Greaves
Keyword(s):  
Vertical Wall ◽  
Water Structure ◽  
Rigid Wall ◽  
Total Force ◽  
Impact Loads ◽  
Wave Impact ◽  
Impact Forces ◽  
Elastic Wall ◽  
Vertical Walls ◽  
The Impact

Abstract Local and global loadings, which may cause the local damage and/or global failure and collapse of offshore structures and ships, are experimentally investigated in this study. The research question is how the elasticity of the structural section affects loading during severe environmental conditions. Two different experiments were undertaken in this study to try to answer this question: (i) vertical slamming impacts of a square flat plate, which represents a plate section of the bottom or bow of a ship structure, onto water surface with zero degree deadrise angle; (ii) wave impacts on a truncated vertical wall in water, where the wall represents a plate section of a hull. The plate and wall are constructed such that they can be either rigid or elastic by virtue of a specially designed spring system. The experiments were carried out in the University of Plymouth’s COAST Laboratory. For the cases considered here, elasticity of the impact plate and/or wall has an effect on the slamming and wave impact loads. Here the slamming impact loads (both pressure and force) were considerably reduced for the elastic plate compared to the rigid one, though only at high impact velocities. The total impact force on the elastic wall was found to reduce for the high aeration, flip-through and slightly breaking wave impacts. However, the impact pressure decreased on the elastic wall only under flip-through wave impact. Due to the elasticity of the plates, the impulse of the first positive phase of pressure and force decreases significantly for the vertical slamming impact tests. This significant effect of hydroelasticity is also found for the total force impulse on the vertical wall under wave impacts. Graphic abstract Hydroelasticity effects on water-structure impacts: a impact pressures on dropped plates; b impact forces on dropped plates; c, d, e, f wave impact pressures on the vertical walls; g wave impact forces on the vertical walls; h wave force impulses on the vertical walls: elastic wall 1 vs. rigid wall (filled markers); elastic wall 2 vs. rigid wall (empty markers)

scholarly journals Breaking Wave Impact Pressure on a Vertical Wall

2010 ◽  
Vol 1 (3-4) ◽  
pp. 155-166 ◽  
Author(s):  
C. Rajasekaran ◽  
S.A. Sannasiraj ◽  
V. Sundar
Keyword(s):  
Vertical Wall ◽  
Impact Pressure ◽  
Breaking Wave ◽  
Wave Impact

Numerical Modeling of Breaking Wave Kinematics and Wave Impact Pressures on a Vertical Slender Cylinder

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Free Surface ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Total Force ◽  
Wave Loads ◽  
Wave Impact ◽  
Large Wave ◽  
Surface Deformations

Wave loads from breaking waves on offshore wind turbine (OWT) substructures in shallow waters still remain uncertain. The interaction of breaking waves with structures is characterized by complex free surface deformations, instantaneous impact of the water mass against the structure, and consequently large wave forces on the structures. The main objective of the paper is to investigate wave impact pressures and kinematics during the interaction of breaking waves with a vertical cylinder using the open-source computational fluid dynamics (CFD) model REEF3D. The model is based on the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the level set method and k–ω turbulence model. Three wave impact conditions are considered in this study. The numerically simulated free surface deformations around the cylinder during the breaking wave interaction are also presented for different wave impact conditions. For three wave impact conditions, the wave impact pressure and the horizontal and vertical components of the particle velocity are computed in front of the cylinder and analyzed. The pressure and velocity profile at their maximum values are also examined and discussed. In addition, the total force is calculated for three breaking conditions and they are correlated with the pressure and kinematics during the interaction.

Free-surface flow generated by a small submerged circular cylinder starting from rest

1995 ◽  
Vol 286 ◽  
pp. 103-116 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Hydrodynamic Force ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Third Order ◽  
Force Prediction ◽  
Small Cylinder ◽  
Submergence Depth

The impulsively starting motion of a small circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The cylinder is considered small if the ratio between its radius and initial submergence depth is much smaller than one. The surface elevation is calculated up to third order. The hydrodynamic force on the small cylinder is also discussed. Certain inconsistencies in our small-cylinder approximation (assuming locally uniform flow around the cylinder) are found in the force prediction. The present work is an accompanying paper to Tyvand & Miloh (1995), where the same problem is studied for arbitrary radius versus submergence depth.

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