scholarly journals Interaction of Water Waves and a Submerged Parabolic Obstacle in the Presence of a Following Uniform/Shear Current Using RANS Model

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Yen-Lung Chen ◽  
Jing-Bo Hung ◽  
Shih-Lun Hsu ◽  
Shih-Chun Hsiao ◽  
Yuan-Chieh Wu
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Analytical Solutions ◽  
Water Waves ◽  
Surface Deformation ◽  
Navier Stokes ◽  
Regular Waves ◽  
Uniform Shear ◽  
Shear Current

This paper simulates regular waves propagating over a submerged parabolic obstacle in the presence of a uniform/shear current using a two-dimensional numerical model, named COBRAS (Cornell Breaking and Structure). The numerical model solves the Reynolds-Averaged Navier-Stokes (RANS) equations and the free surface deformation is tracked using the volume of fluid method (VOF). The capability of the numerical model to simulate regular waves with a uniform or shear current over a constant water depth is first validated with available analytical solutions and experimental data. Comparisons among the experimental data, analytical solutions, and present numerical results show good agreements. Then, regular waves propagating over a submerged parabolic obstacle with a following current are investigated. Detailed discussions including those on the velocity and vorticity fields and the relation between free surface and vorticity are given.

Simulation of the Gap Resonance Between Two Rectangular Barges in Regular Waves by a Free Surface Viscous Flow Solver

2013 ◽  
Author(s):  
B. Elie ◽  
G. Reliquet ◽  
P.-E. Guillerm ◽  
O. Thilleul ◽  
P. Ferrant ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Viscous Flow ◽  
Stokes Equations ◽  
Resonance Phenomenon ◽  
Navier Stokes ◽  
Regular Waves ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Gap Resonance

This paper compares numerical and experimental results in the study of the resonance phenomenon which appears between two side-by-side fixed barges for different sea-states. Simulations were performed using SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach and results are compared with experimental data on two fixed barges with different headings and bilges. Numerical results, obtained using the SWENSE approach, are able to predict both the frequency and the magnitude of the RAO functions.

Numerical Simulation of Free Surface Flows by Using Weakly Compressible Corrected MPS Method

2013 ◽  
Vol 842 ◽  
pp. 449-454
Author(s):  
Hao Wang ◽  
Qin Jiang ◽  
Chang Kuan Zhang
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Surface Deformation ◽  
Free Particle ◽  
Free Surface Flows ◽  
Dam Break ◽  
Mps Method ◽  
Mesh Free ◽  
Weakly Compressible

Mesh-free particle (Lagrangian) methods such as Moving Particle Semi-Implicit (MPS) are the latest generation of methods in the field of computational fluid dynamics where large interfacial deformations and fragmentations exist. Due to their mesh-free nature, these methods are capable of simulating any kind of boundary/interface deformation and fragmentations. In this study the weakly compressible corrected MPS (WCC-MPS) method is used to simulate dam break over a dry bed, which is a highly erosive and transient flow problem. The developed numerical model is first validated using a dry bed dam break problem by comparing with experimental data. Comparisons between the model results and experimental data showed that the developed numerical model with WCC-MPS method can well represent the dam break problems with very large free surface deformation and fragmentations.

Effective Power and Speed Loss of Underwater Vehicles in Close Proximity to Regular Waves

2017 ◽  
Author(s):  
Stefan Daum ◽  
Martin Greve ◽  
Renato Skejic
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Water Waves ◽  
Underwater Vehicles ◽  
Total Resistance ◽  
Wave Load ◽  
Regular Waves ◽  
Effective Power ◽  
Close Proximity ◽  
Deep Water Waves

The present study is focused on performance issues of underwater vehicles near the free surface and gives insight into the analysis of a speed loss in regular deep water waves. Predictions of the speed loss are based on the evaluation of the total resistance and effective power in calm water and preselected regular wave fields w.r.t. the non-dimensional wave to body length ratio. It has been assumed that the water is sufficiently deep and that the vehicle is operating in a range of small to moderate Froude numbers by moving forward on a straight-line course with a defined encounter angle of incident regular waves. A modified version of the Doctors & Days [1] method as presented in Skejic and Jullumstrø [2] is used for the determination of the total resistance and consequently the effective power. In particular, the wave-making resistance is estimated by using different approaches covering simplified methods, i.e. Michell’s thin ship theory with the inclusion of viscosity effects Tuck [3] and Lazauskas [4] as well as boundary element methods, i.e. 3D Rankine source calculations according to Hess and Smith [5]. These methods are based on the linear potential fluid flow and are compared to fully viscous finite volume methods for selected geometries. The wave resistance models are verified and validated by published data of a prolate spheroid and one appropriate axisymmetric submarine model. Added resistance in regular deep water waves is obtained through evaluation of the surge mean second-order wave load. For this purpose, two different theoretical models based on potential flow theory are used: Loukakis and Sclavounos [6] and Salvesen et. al. [7]. The considered theories cover the whole range of important wavelengths for an underwater vehicle advancing in close proximity to the free surface. Comparisons between the outlined wave load theories and available theoretical and experimental data were carried out for a submerged submarine and a horizontal cylinder. Finally, the effective power and speed loss are discussed from a submarine operational point of view where the mentioned parameters directly influence mission requirements in a seaway. All presented results are carried out from the perspective of accuracy and efficiency within common engineering practice. By concluding current investigations in regular waves an outlook will be drawn to the application of advancing underwater vehicles in more realistic sea conditions.

scholarly journals Development of An Integrated Numerical Model for Simulating Wave Interaction with Permeable Submerged Breakwaters Using Extended Navier–Stokes Equations

2020 ◽  
Vol 8 (2) ◽  
pp. 87 ◽  
Author(s):  
Paran Pourteimouri ◽  
Kourosh Hejazi
Keyword(s):  
Porous Medium ◽  
Wave Propagation ◽  
Numerical Model ◽  
Analytical Solutions ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Stokes Wave ◽  
Navier Stokes Equations ◽  
Numerical Predictions ◽  
The Impact

An integrated two-dimensional vertical (2DV) model was developed to investigate wave interactions with permeable submerged breakwaters. The integrated model is capable of predicting the flow field in both surface water and porous media on the basis of the extended volume-averaged Reynolds-averaged Navier–Stokes equations (VARANS). The impact of porous medium was considered by the inclusion of the additional terms of drag and inertia forces into conventional Navier–Stokes equations. Finite volume method (FVM) in an arbitrary Lagrangian–Eulerian (ALE) formulation was adopted for discretization of the governing equations. Projection method was utilized to solve the unsteady incompressible extended Navier–Stokes equations. The time-dependent volume and surface porosities were calculated at each time step using the fraction of a grid open to water and the total porosity of porous medium. The numerical model was first verified against analytical solutions of small amplitude progressive Stokes wave and solitary wave propagation in the absence of a bottom-mounted barrier. Comparisons showed pleasing agreements between the numerical predictions and analytical solutions. The model was then further validated by comparing the numerical model results with the experimental measurements of wave propagation over a permeable submerged breakwater reported in the literature. Good agreements were obtained for the free surface elevations at various spatial and temporal scales, velocity fields around and inside the obstacle, as well as the velocity profiles.

Numerical Modelling of Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Square Arrangements

2016 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arnsten
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Wave Interaction ◽  
Wave Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters and an accurate numerical modelling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source (Computational Fluid Dynamics) CFD model REEF3D is used to simulate the breaking wave interaction with the multiple cylinders. The numerical model is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations, the level set method for the free surface and the k–ω model for turbulence. The model uses a 5th-order conservative finite difference WENO scheme for the convective discretization and a 3rd-order Runge-Kutta scheme for time discretization. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is seen between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. The breaking wave forces on each cylinder in the group are computed for the two cases and the results are compared with the breaking wave force on a single isolated cylinder. Further, the study investigates the water surface elevations and the free surface flow features around the cylinders. In general, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. The results of the present study show that the interference effects from the neighbouring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

scholarly journals NUMERICAL AND EXPERIMENTAL STUDY OF DAM-BREAK FLOOD PROPAGATION AND ITS IMPLICATION TO SEDIMENT EROSION

2012 ◽  
Vol 1 (33) ◽  
pp. 7
Author(s):  
Hung-Chu Hsu ◽  
A. Torres-Freyermuth ◽  
Tian-Jian Hsu ◽  
Hwung-Hweng Hwung
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Numerical Model ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Transport Processes ◽  
Dam Break ◽  
Navier Stokes ◽  
Suspended Sediment Transport ◽  
Initial Stage

Regarding the hydrodynamics, within the past two decades it has become popular in numerical modeling of free-surface flow to adopt a Reynolds-averaged Navier-Stokes approach, where the volume of fluid (VOF) method is utilized to track the evolution of free-surface. However, this robust numerical model has not been widely applied to the study of sediment transport processes. In this study, we shall extend the numerical model to simulate suspended sediment transport and study the erosion pattern during the initial stage of the dam break flow. We also conducted a series of experiments in a horizontal channel of rectangular section and recorded the snap shots of surface profiles of a dam- break wave during the initial stage of dam-break. Measured data is utilized here to study the hydrodynamics and to validate the numerical model.

Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Two Square Arrangements

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Wave Interaction ◽  
Wave Force ◽  
Maximum Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters, and an accurate numerical modeling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source computational fluid dynamics (CFD) model REEF3D is used to simulate the breaking wave interaction with multiple cylinders. The numerical model is based on the incompressible Reynolds-averaged Navier–Stokes (RANS) equations, the level set method for the free surface, and the k–ω model for turbulence. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is obtained between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. For both configurations, three different tank widths and four different spacings between the cylinders are investigated. The breaking wave forces on each cylinder in the group are computed for each case for the two configurations, and the results are compared with the breaking wave force on a single isolated cylinder. Furthermore, the study investigates the water surface elevations and the free surface flow features around the cylinders. For the closely spaced cylinders in a relatively narrower tank, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. But for the widely spaced cylinder in a relatively wider tank, the forces are higher and lower for the upstream cylinders and downstream cylinders, respectively, than the maximum force on a single isolated cylinder. The results of the present study show that the interference effects from the neighboring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

scholarly journals SURFACE TEMPERATURE RECONSTRUCTION BASED ON THE THERMOCAPILLARY EFFECT

2010 ◽  
Vol 52 (2) ◽  
pp. 146-159 ◽  
Author(s):  
M. SELLIER ◽  
S. PANDA
Keyword(s):  
Experimental Data ◽  
Inverse Problem ◽  
Free Surface ◽  
Temperature Gradient ◽  
Film Thickness ◽  
Surface Deformation ◽  
Thin Liquid Film ◽  
Closed Form Solution ◽  
Temperature Reconstruction ◽  
Thickness Variation

AbstractA thin liquid film subject to a temperature gradient is known to deform under the action of thermocapillary stresses which induce convective cells. The free surface deformation can be thought of as the signature of the imposed temperature gradient, and this study investigates the inverse problem of trying to reconstruct the temperature field from known free surface variations. The present work builds on the analysis of Tan et al. [“Steady thermocapillary flows of thin liquid layers I. Theory”, Phys. Fluids A2 (1990) 313–321, doi:10.1063/1.857781] which provides a long-wave evolution equation for the fluid film thickness variation on nonuniformly heated substrates and proposes a solution strategy for the planar flow version of this inverse problem. The present analysis reveals a particular case for which there exists an explicit, closed-form solution expressing the local substrate temperature in terms of the local film thickness and its spatial derivatives. With some simplifications, this analysis also shows that this solution applies to three-dimensional flows. The temperature reconstruction strategies are successfully tested against “artificial” experimental data (obtained by solving the direct problem for known temperature profiles) and actual experimental data.

Numerical Investigation of Wave Kinematics Inside Berm Breakwaters With Varying Berm Geometry Using REEF3D

2017 ◽  
Author(s):  
Athul Sasikumar ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Onno Musch ◽  
Øivind A. Arntsen
Keyword(s):  
Numerical Model ◽  
Water Waves ◽  
Numerical Models ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Production Chain ◽  
Wave Kinematics ◽  
Offshore Production ◽  
Physical Model Tests ◽  
Hydrodynamic Processes

Harbours are important infrastructures for an offshore production chain. These harbours are protected from the actions of sea by breakwaters to ensure safe loading, unloading of vessels and also to protect the infrastructure. One of the important hydrodynamic processes in these regions is the interaction of water waves with permeable breakwaters such as rubble mound breakwaters or berm breakwaters. It is important to study the wave-breakwater interactions in order to have an optimal design of these structures. In current literature, research regarding the design of these structures is majorly based on physical model tests. Empirical formulations are derived based on these test, which can have a relatively narrow range of applicability. In this study a new tool, a three-dimensional numerical model is introduced. Physical and numerical models have limitations that can restrict their independent use. A combined use of both can lead to different forms of improvements: being able to model problems that cannot be modelled by either physical or numerical modelling alone; increasing quality at the same cost or obtaining the same quality at reduced cost. In this study, the open-source CFD model REEF3D is used to study the design of berm breakwaters. The model uses the Volume averaged Reynolds Averaged Navier-Stokes (VRANS) equations to solve the porous flows. At first the VRANS approach in REEF3D is validated for flow through porous media. A dam break case is simulated for two different porous materials. Comparisons are made for the free surface both inside and outside the porous medium. The numerical model REEF3D is applied to show how to extend the database obtained with purely numerical results, simulating different structural alternatives for the berm in a berm breakwater. Different simulations are conducted with varying berm geometry. The influence of the berm geometry on the pore pressure and velocities are studied. The resulting optimal berm geometry is compared to the geometry according to empirical formulations.

scholarly journals Numerical Modeling of Coupled Surge-Heave Sloshing in a Rectangular Tank with Baffles

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Lv Ren ◽  
Yinjie Zou ◽  
Jinbo Tang ◽  
Xin Jin ◽  
Dengsong Li ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Free Surface ◽  
Numerical Model ◽  
Frequency Response ◽  
Navier Stokes ◽  
Rectangular Tank ◽  
Vertical Baffle ◽  
Tank Bottom ◽  
Violent Sloshing ◽  
Effective Water

Liquid sloshing under coupled surge and heave excitations in a rectangular tank has been numerically investigated by applying a Navier–Stokes solver. Fieriest coupled sloshing was further considered, and the internal baffle was expected to suppress the violent sloshing wave. After getting fully validated against available results from the literatures, the numerical model was applied to research coupled sloshing, and both vertical baffle and horizontal baffle have been considered. Due to the strong vortexes created by the sharper corners of the baffles and the reduction of the effective water bulk climbing through the tank walls, the sloshing was dramatically reduced. The increase of the baffle distance away from the tank bottom led to a decrease in the sloshing wave. It was noted that the baffle near the free surface caused the maximal dissipation. The frequency response of the sloshing wave was accordingly illustrated.

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