CFD Modeling of Fully Nonlinear Water Wave Tank

2009 ◽  
Author(s):  
Guangyu Wu ◽  
Owen H. Oakley
Keyword(s):  
Free Surface ◽  
Potential Flow ◽  
Wave Breaking ◽  
Water Wave ◽  
Surface Displacement ◽  
Wave Steepness ◽  
Wave Tank ◽  
Fully Nonlinear ◽  
Free Surface Displacement ◽  
Time Histories

In this study, we use CFD simulations to model a fully nonlinear water wave tank. Firstly, for validation purpose, regular waves with different wave steepness are simulated and the results are compared with the second-order potential flow solution for the free surface displacement time history at fixed locations, the instantaneous free surface spatial profiles, and the velocity and pressure fields under the free surface. It is shown that for small wave steepness, the CFD solutions agree very well with the second-order potential flow solutions while for large wave steepness, apparent differences between these two solutions are observed. The validation and fully nonlinear feature of the CFD solutions are therefore demonstrated. Secondly, plunging breaking waves are simulated using the CFD wave tank by focusing a large number of linear wave components at a prescribed time and location. The time histories and normalized variance of free surface displacement at various locations along the tank are obtained from the CFD simulation and compared to the lab experiments. In particular, the CFD results predict reasonably well the wave breaking location and the loss of energy flux due to wave breaking. Finally, a vertical circular cylinder is placed in the CFD wave tank to simulate the breaking wave impact on a fixed structure. The pressure time histories at various points on the cylinder surface are obtained for several cylinder locations with respect to the prescribed wave breaking point. The CFD results are compared with previous experiments and discussed.

Oscillatory Free Surface Displacement of Finite Amplitude in a Small Orifice

2004 ◽  
Vol 126 (5) ◽  
pp. 818-826
Author(s):  
Brian J. Daniels ◽  
James A. Liburdy
Keyword(s):  
Free Surface ◽  
Potential Flow ◽  
Surface Displacement ◽  
Experimental Results ◽  
Significant Shift ◽  
Curvature Effect ◽  
Modal Frequency ◽  
Large Curvature ◽  
Curvature Effects ◽  
Free Surface Displacement

The oscillatory free-surface displacement in an orifice periodically driven at the inlet is studied. The predictions based on a potential flow analysis are investigated in light of viscous and large curvature effects. Viscous effects near the wall are estimated, as are surface viscous energy loss rates. The curvature effect on the modal frequency is shown to become large at the higher modal surface shapes. Experimental results are obtained using water for two orifice diameters, 794 and 1180 μm. Results of surface shapes and modal frequencies are compared to the predictions. Although modal shapes seem to be well predicted by the theory, the experimental results show a significant shift of the associated modal frequencies. A higher-order approximation of the surface curvature is presented, which shows that the modal frequency should, in fact, be reduced from potential flow predictions as is consistent with the large curvature effect. To account for the effect of finite surface displacements an empirical correlation for the modal frequencies is presented.

Development of 3-Dimensional Fully Nonlinear Potential Flow Planar Wave Tank in Framework of OpenFOAM

2019 ◽  
Author(s):  
Zaibin Lin ◽  
Ling Qian ◽  
Wei Bai ◽  
Zhihua Ma ◽  
Hao Chen ◽  
...  
Keyword(s):  
Free Surface ◽  
Potential Flow ◽  
Wave Structure ◽  
Wave Model ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Fully Nonlinear ◽  
3 Dimensional ◽  
Nonlinear Potential ◽  
Numerical Wave

Abstract A 3-Dimensional numerical wave tank based on the fully nonlinear potential flow theory has been developed in OpenFOAM, where the Laplace equation of velocity potential is discretized by Finite Volume Method. The water surface is tracked by the semi-Eulerian-Lagrangian method, where water particles on the free surface are allowed to move vertically only. The incident wave is generated by specifying velocity profiles at inlet boundary with a ramp function at the beginning of simulation to prevent initial transient disturbance. Additionally, an artificial damping zone is located at the end of wave tank to sufficiently absorb the outgoing waves before reaching downstream boundary. A five-point smoothing technique is applied at the free surface to eliminate the saw-tooth instability. The proposed wave model is validated against theoretical results and experimental data. The developed solver could be coupled with multiphase Navier-Stokes solvers in OpenFOAM in the future to establish an integrated versatile numerical wave tank for studying efficiently wave structure interaction problems.

scholarly journals Modelling of depth-induced wave breaking in a fully nonlinear free-surface potential flow model

2019 ◽  
Vol 154 ◽  
pp. 103579 ◽  
Author(s):  
Christos E. Papoutsellis ◽  
Marissa L. Yates ◽  
Bruno Simon ◽  
Michel Benoit
Keyword(s):  
Free Surface ◽  
Surface Potential ◽  
Potential Flow ◽  
Wave Breaking ◽  
Flow Model ◽  
Fully Nonlinear ◽  
Nonlinear Free Surface ◽  
Potential Flow Model

scholarly journals Investigation of Focusing Wave Properties in a Numerical Wave Tank with a Fully Nonlinear Potential Flow Model

2019 ◽  
Vol 7 (10) ◽  
pp. 375 ◽  
Author(s):  
Weizhi Wang ◽  
Arun Kamath ◽  
Csaba Pakozdi ◽  
Hans Bihs
Keyword(s):  
Wave Height ◽  
Potential Flow ◽  
Wave Steepness ◽  
Numerical Wave Tank ◽  
Wave Groups ◽  
Wave Tank ◽  
Fully Nonlinear ◽  
Nonlinear Potential ◽  
Numerical Wave ◽  
Focused Wave

Nonlinear wave interactions and superpositions among the different wave components and wave groups in a random sea sometimes produce rogue waves with extremely large wave heights that appear unexpectedly. A good understanding of the generation and evolution of such extreme wave events is of great importance for the analysis of wave forces on marine structures. A fully nonlinear potential flow (FNPF) model is proposed in the presented paper to investigate the different factors that influence the wave focusing location, focusing time and focusing wave height in a numerical wave tank. Those factors include wave steepness, spectrum bandwidth, wave generation method, focused wave spectrum, and wave spreading functions. The proposed model solves the Laplace equation together with the boundary conditions on a σ -coordinate grid using high-order discretisation schemes on a fully parallel computational framework. The model is validated against the focused wave experiments and thereafter used to obtain insights into the effects of the different factors. It is found that the wave steepness contributes to changing the location and time of focus significantly. Spectrum bandwidth and directional spreading affect the focusing wave height and profile, for example, a wider bandwidth and a wider directional spread lead to a lower focusing wave height. A Neumann boundary condition represents the nonlinearity of the wave groups better than a relaxation method for wave generation.

Nonlinear Helmholtz oscillations in harbours and coupled basins

1981 ◽  
Vol 104 ◽  
pp. 407-418 ◽  
Author(s):  
John W. Miles
Keyword(s):  
Free Surface ◽  
Additional Assumption ◽  
Phase Plane ◽  
Surface Displacement ◽  
Elliptic Functions ◽  
Forced Oscillations ◽  
Amplitude Parameter ◽  
Spatial Uniformity ◽  
Open Sea ◽  
Free Surface Displacement

Free and forced oscillations in a basin that is connected through a narrow canal to either the open sea or a second basin are considered on the assumption that the spatial variation of the free-surface displacement is negligible. The free-surface displacement in the canal is allowed to be finite, subject only to the restriction (in addition to that implicit in the approximation of spatial uniformity) that the canal does not run dry. The resulting model yields a Hamiltonian pair of phase-plane equations for the free oscillations, which are integrated in terms of elliptic functions on the additional assumption that the kinetic energy of the motion in the basin(s) is negligible compared with that in the canal or otherwise through an expansion in an amplitude parameter. The corresponding model for forced oscillations that are limited by radiation damping yields a generalization of Duffing's equation for an oscillator with a soft spring, the solution of which is obtained as an expansion in the amplitude of the fundamental term in a Fourier expansion. Equivalent circuits are developed for the various models.

Comparisons of Two Different Mixed Eulerian-Lagrangian Schemes Based on a Study of Flare-Slamming Hydrodynamics

1996 ◽  
Vol 118 (3) ◽  
pp. 174-183
Author(s):  
M. L. Wang ◽  
A. W. Troesch ◽  
B. Maskew
Keyword(s):  
Free Surface ◽  
Comparative Study ◽  
Numerical Simulations ◽  
Fourier Coefficients ◽  
Fully Nonlinear ◽  
Time Stepping ◽  
Time Histories ◽  
Nonlinear Free Surface ◽  
Simulated Time ◽  
Flare Slamming

A comparative study of two different mixed Eulerian-Lagrangian methods is presented. Representative numerical simulations of oscillatory flare-slamming flows are given. Computations based on these two different numerical schemes, i.e., a desingularized method using Rankine ring sources and a source-doublet panel method (e.g., USAERO/FSP©), are compared with experiments. Fourier coefficients of the simulated time histories and experimentally measured forces are given for detailed error comparisons. The numerical simulations demonstrate the ranges of applicability of these two methods. Both are shown to be efficient and robust time-stepping schemes for the fully nonlinear free-surface problem studied here.

scholarly journals Three dimensional numerical simulations for non-breaking solitary wave interacting with a group of slender vertical cylinders

2009 ◽  
Vol 1 (1) ◽  
Author(s):  
Weihua Mo ◽  
Philip L.-F. Liu
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Dynamic Pressure ◽  
Laboratory Data ◽  
Three Dimensional ◽  
Time History ◽  
Surface Displacement ◽  
Numerical Results ◽  
Finite Volume Scheme ◽  
Free Surface Displacement

AbstractIn this paper we validate a numerical model for-structure interaction by comparing numerical results with laboratory data. The numerical model is based on the Navier-Stokes(N-S) equations for an incompressible fluid. The N-S equations are solved by two-step projection finite volume scheme and the free surface displacements are tracked by the slender vertical piles. Numerical results are compared with the laboratory data and very good agreement is observed for the time history of free surface displacement, fluid particle velocity and force. The agreement for dynamic pressure on the cylinder is less satisfactory, which is primarily caused by instrument errors.

Equilibrium and oscillations of liquid fuel free surface in coaxial-cylindrical vessels under microgravity conditions

2021 ◽  
Author(s):  
Y. Zhaokai ◽  
A.N. Temnov
Keyword(s):  
Contact Angle ◽  
Free Surface ◽  
Liquid Fuel ◽  
Outer Space ◽  
Surface Displacement ◽  
Ideal Liquid ◽  
Intermolecular Forces ◽  
Hydrodynamic Characteristics ◽  
Free Surface Displacement ◽  
Microgravity Conditions

In the absence of significant mass forces, the behavior of liquid fuel under microgravity conditions is determined by surface tension forces, which are intermolecular forces at the interface of two phases. The paper posed and solved the problem of equilibrium and small oscillations of an ideal liquid under microgravity conditions, and also quantified the influence of various parameters: the contact angle α0, the Bond number, the ratio of the radii of the inner and outer walls of the vessel and the depth of the liquid. For the coaxial-cylindrical vessels, there were obtained expressions in the form of a Bessel series for the potential of the fluid velocities and the free surface displacement field. The study relies on the analytical and experimental data available in the literature and proves the reliability of the developed numerical algorithm. Findings of research show that for and r, with the physical state of the wetted surface being unchanged, the shape of the free surface tends to be flat and the contact angle has little effect on the intrinsic vibration frequency of the free surface of the liquid. The results obtained can be used to solve problems of determining the hydrodynamic characteristics of the movement of liquid fuel in outer space.

Research on the Bubble Motion near Free Surface in Underwater Explosion

2011 ◽  
Vol 52-54 ◽  
pp. 1086-1091
Author(s):  
Jian Li ◽  
Ji Li Rong ◽  
Da Lin Xiang
Keyword(s):  
Free Surface ◽  
Potential Flow ◽  
Energy Equation ◽  
Equations Of Motion ◽  
Underwater Explosion ◽  
Engineering Calculation ◽  
Bubble Motion ◽  
Hamilton Principle ◽  
Time Histories ◽  
Theory Research

A model for a moderately deep underwater explosion bubble was developed in inviscid and irrotational fluid. Considering the effects of gravity, buoyancy, drag to the motion of bubble, the equations of motion (EOM) for bubble in inviscid and irrotational fluid near a free surface were established by introducing the potential-flow theory, energy equation and Hamilton principle. The displacement of the center of bubble, the radius-time histories and impulse periods of bubble were acquired by solving the EOM. The calculated results were compared with the experimental and numerical results. The compared results show that the former is consistent with the latter. The research has value to correlative theory research and engineering calculation.

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