Wave Run-Up Simulations With a Moving Large Volume Semi-Submersible Platform

2011 ◽  
Author(s):  
Rafael de Andrade Watai ◽  
Fabio Tadao Matsumoto ◽  
Joa˜o Vicente Sparano ◽  
Alexandre Nicolaos Simos ◽  
Marcos Donato A. S. Ferreira
Keyword(s):  
Free Surface ◽  
Large Volume ◽  
Stokes Equations ◽  
Scale Model ◽  
Uniform Grid ◽  
Small Scale ◽  
Regular Waves ◽  
Wave Basin ◽  
Free Surface Displacement ◽  
Run Up

Since July 2008, the Numerical Offshore Tank (TPN) of the University of Sa˜o Paulo and Petrobras have been working on a research project intended to improve knowledge and modeling of advanced hydrodynamics topics, such as the wave run-up phenomenon. Among other activities, wave basin tests were performed with small-scale model of a large volume semi-submersible designed to operate in Campos Basin. These tests evidenced significant run-up effects on its squared-section columns for the steepest waves in several design conditions. In order to evaluate the difficulties involved in modeling the wave run-up phenomenon, simplified tests were also carried out with the model fixed and moored in regular waves with varying steepness. Previous studies using a 2nd order BEM model and a VOF CFD code to predict free-surface elevations below the deck under regular waves were presented in Matsumoto et al. (2010). The studies illustrated considerable differences between the wave elevation results in fixed and moored model setup; however, by that time, the analysis of the moored model by a VOF CFD code was not yet complete. This paper, therefore, presents wave run-up estimations with a moving large volume semi-submersible platform performed with the CFD code ComFLOW, which solves the Navier-Stokes equations employing a local height function to the free surface displacement. The phenomenon is investigated by simulating the flow around the semi-submersible model under the influence of high steepness regular waves on a non-uniform grid. Platform motions, derived from a first order BEM code, are imposed and synchronized with the incoming wave. Aiming at avoiding numerical wave reflections, a damping zone is also applied and positioned downstream the platform model. Predicted results are compared to experimental data, measured by seven vertical wave probes located in different positions below the model deck. Although considerably time-consuming, it will be shown that simulations present very good agreement with the experimental results.

scholarly journals Run-up on vertical piles due to regular waves: Small-scale model tests and prediction formulae

2016 ◽  
Vol 118 ◽  
pp. 1-11 ◽  
Author(s):  
Lisham Bonakdar ◽  
Hocine Oumeraci ◽  
Amir Etemad-Shahidi
Keyword(s):  
Model Tests ◽  
Scale Model ◽  
Small Scale ◽  
Regular Waves ◽  
Run Up ◽  
Small Scale Model

Experimental Evaluation of the Dynamic Air Gap of a Large-Volume Semi-Submersible Platform

2006 ◽  
Author(s):  
Alexandre N. Simos ◽  
Andre´ L. C. Fujarra ◽  
Joa˜o V. Sparano ◽  
Carlos H. Umeda ◽  
Ronaldo R. Rossi
Keyword(s):  
Large Volume ◽  
Air Gap ◽  
Analytical Models ◽  
Scale Model ◽  
Small Scale ◽  
Design Storm ◽  
Numerical Predictions ◽  
Negative Effect ◽  
Run Up ◽  
Steep Waves

Definition of air gap is an extremely important issue in the design of floating offshore systems such as semi-submersible or TLP platforms. For these systems, any unnecessary increase in the static value of air gap generally demands the payload to be decreased or leads to a larger buoyant hull, which, in any case, has a negative effect on the project economics. Designers face a difficult challenge since there is no well-established methodology for predicting the air gap demand in the early stages of the design. This is a consequence of the inherent complexity involved in the problem of predicting the free-surface elevation around large structures in steep-waves, such as the largest wave expected during a design storm-sea spectrum. Non-linear diffraction models are usually called for a more consistent evaluation of the wave field under the deck and the wave run-up upon the columns, but even second-order analysis is not free of uncertainties. Therefore, air gap evaluation still relies heavily on experimental analysis. This paper presents some towing-tank results performed for the evaluation of the dynamic air gap of a large-volume semi-submersible platform. Regular wave tests were performed for the small-scale model in both restrained and moored configurations and results were confronted with numerical predictions. Air gap response at different locations of the hull was evaluated under three different sea states and results were compared to some semi-analytical models proposed in literature for preliminary air gap estimation. The role of dynamic coupling provided by a taut-leg mooring system on the air gap results is also discussed based on the experimental results.

Wave Energy Hyperbaric Device for Electricity Production

2007 ◽  
Author(s):  
Segen F. Estefen ◽  
Paulo Roberto da Costa ◽  
Eliab Ricarte ◽  
Marcelo M. Pinheiro
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Experimental Results ◽  
Electricity Production ◽  
Scale Model ◽  
Small Scale ◽  
Regular Waves ◽  
Hyperbaric Chamber ◽  
Small Scale Model

Wave energy is a renewable and non-polluting source and its use is being studied in different countries. The paper presents an overview on the harnessing of energy from waves and the activities associated with setting up a plant for extracting energy from waves in Port of Pecem, on the coast of Ceara State, Brazil. The technology employed is based on storing water under pressure in a hyperbaric chamber, from which a controlled jet of water drives a standard turbine. The wave resource at the proposed location is presented in terms of statistics data obtained from previous monitoring. The device components are described and small scale model tested under regular waves representatives of the installation region. Based on the experimental results values of prescribed pressures are identified in order to optimize the power generation.

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.

Heat Transfer Generated by the Interaction of Single and Multiple Tandem Jets in Crossflow

2010 ◽  
Author(s):  
Amina Radhouane ◽  
Nejla Mahjoub ◽  
Hatem Mhiri ◽  
George Lepalec ◽  
Philippe Bournot
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Uniform Grid ◽  
Cooling Power ◽  
Small Scale ◽  
Fluid Composition ◽  
Navier Stokes Equations ◽  
The Impact

“Twin jets in Crossflow” is a common configuration that finds application in several large and/or small scale industrial fields. The interest in such a configuration is further enhanced by its dependence in several parameters, that may be geometric, dynamic, thermal, or relative to the handled fluid composition. We propose to focus in the present work on the effect of the number of the emitted jets on the generated heat transfer, in presence of an unchanged uniform crossflow. To reach this goal, single, double and triple jet configurations were simulated, based upon the resolution of the Navier Stokes equations by means of the RSM (Reynolds Stress Model) second order turbulent closure model, together with a non uniform grid system particularly tightened near the emitting nozzles. After validation, we tried to find out the impact of the number of the handled jets on their cooling “power” by tracking the temperature distribution of the resulting flowfield. Since in practically all applications we are in need of higher efficiencies and then of higher operating temperatures, we are constantly concerned about not going beyond the shielding material melting temperature. If the use of cooling jets proves to be efficient, this may bring a significant progress in the technological field.

Wave overtopping and splash-up at seawalls with bullnose

2020 ◽  
Vol 20 (3) ◽  
pp. 333-342
Author(s):  
Le Hai Trung ◽  
Dang Thi Linh ◽  
Tang Xuan Tho ◽  
Nguyen Truong Duy ◽  
Tran Thanh Tung
Keyword(s):  
Storm Surges ◽  
Model Tests ◽  
Scale Model ◽  
Small Scale ◽  
Wave Overtopping ◽  
Run Up ◽  
Coast Of Vietnam ◽  
Small Scale Model ◽  
Wall Interactions

Seawalls have been erected to protect hundreds of towns and tourism areas stretching along the coast of Vietnam. During storm surges or high tides, wave overtopping and splash-up would often threaten the safety of infrastructures, traffic and residents on the narrow land behind. Therefore, this study investigates these wave-wall interactions via hydraulic small scale model tests at Thuyloi University. Remarkably, the structure models were shaped to have different seaward faces and bullnoses. The wave overtopping discharge and splash run-up height at seawalls with bullnose are significantly smaller than those without bullnose. Furthermore, the magnitude of these decreasing effects is quantitatively estimated.

scholarly journals Water wave diffraction by a cylinder array. Part 1. Regular waves

2001 ◽  
Vol 442 ◽  
pp. 1-32 ◽  
Author(s):  
C. O. G. OHL ◽  
R. EATOCK TAYLOR ◽  
P. H. TAYLOR ◽  
A. G. L. BORTHWICK
Keyword(s):  
Free Surface ◽  
Diffraction Theory ◽  
Second Order ◽  
Surface Elevation ◽  
Circular Cylinders ◽  
Regular Waves ◽  
Wave Basin ◽  
Measured Time ◽  
Field Radiation ◽  
Offshore Wave

Diffraction of regular waves by arrays of vertical bottom-mounted circular cylinders is investigated using theoretical, computational, and experimental methods. Experiments in an offshore wave basin are designed to measure free surface elevation η at multiple locations in the vicinity of a multi-column structure subjected to regular waves of frequency 0.449 < ka < 0.524 and steepness 0.122 < kA < 0.261, where k is the wavenumber, a the cylinder radius and A the wave amplitude. Results from regular wave data analysis for first-order amplitudes are compared with those from analytical linear diffraction theory, which is shown to be accurate for predicting incident waves of low steepness. Second- and third-order terms are also estimated from the measured time series, and the effects near a second-order near-trapping frequency are compared to semi-analytical second-order diffraction theory. Linear diffraction theory is shown to be very accurate at predicting the global surface elevation features, even for waves of high steepness. However, violent events and significant nonlinear interactions, including breaking induced by wave scattering, have been observed. Furthermore, second-order near-trapping was observed to affect the magnitude of local free surface oscillations as well as scattered far-field radiation.

Experimental and Numerical Studies of the Wave Energy Hyberbaric Device for Electricity Production

2008 ◽  
Author(s):  
Segen F. Estefen ◽  
Paulo de T. T. Esperanc¸a ◽  
Eliab Ricarte ◽  
Paulo R. da Costa ◽  
Marcelo M. Pinheiro ◽  
...  
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Electricity Production ◽  
Small Scale ◽  
Brazilian Coast ◽  
Regular Waves ◽  
Numerical Studies ◽  
Wave Basin ◽  
Parametric Studies ◽  
Best Parameters

Small scale experiments and numerical simulations have been performed to evaluate a new concept of converter to produce electricity from wave energy. The models, tested in scale 1:10, have been submitted to different regular waves, with height and period representatives of the Brazilian coast, to evaluate the power generation and efficiency. The tests were carried out in a wave basin able to simulate in scale the wave conditions. Software especially written for the simulation of the converter behavior under regular waves has been initially correlated with the experimental results and, later on, it will be employed in parametric studies to estimate the best parameters of the system, in particular the prescribed pressure to be set for the best performance in terms of electricity production.

Computational Fluid Dynamics Simulations of Regular and Irregular Waves Past a Horizontal Semi-Submerged Cylinder

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai ◽  
Sopheak Seng
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Wave Height ◽  
Stokes Equations ◽  
Wave Force ◽  
Numerical Results ◽  
Irregular Waves ◽  
Wave Forces ◽  
Regular Waves ◽  
Peak Period

Two-dimensional (2D) numerical simulations have been performed to investigate both regular and irregular waves past a fixed horizontally semisubmerged circular cylinder. The 2D simulations are carried out by solving Navier–Stokes equations discretized by finite volume method. Volume of fluid (VOF) method is employed to capture the free surface in the numerical wave tank (NWT). Validation studies have been performed by comparing the numerical results of free surface waves past the cylinder with the published experimental and numerical data. The present numerical results are in good agreement with both the experimental and the other numerical results in terms of hydrodynamic forces and free surface elevation. Subsequently, the effects of the wave height and the wavelength on wave–structure interaction are investigated by conducting numerical simulations on the regular and the irregular waves past a semisubmerged cylinder at different wave heights and the wavelengths. The averaged and maximum vertical wave forces on the cylinder increase with the increasing wave height. The numerical results for the irregular waves are compared with those induced by the regular waves in terms of the maximum and averaged vertical wave forces. When the significant wave height and the spectral peak period of the irregular waves are equal to the wave height and the wave period of the regular waves, the maximum vertical wave force induced by the irregular waves is larger than that induced by the regular waves, meanwhile, the average vertical wave forces have the contrary relationship.

Experimental Tests of a 1:16th-Scale Model of the Spar-Buoy OWC in a Large Scale Wave Flume in Regular Waves

2018 ◽  
Author(s):  
R. P. F. Gomes ◽  
J. C. C. Henriques ◽  
L. M. C. Gato ◽  
A. F. O. Falcão
Keyword(s):  
Large Scale ◽  
Experimental Tests ◽  
Domain Model ◽  
Scale Model ◽  
Chamber Pressure ◽  
Viscous Drag ◽  
Regular Waves ◽  
Mooring Lines ◽  
Wave Flume ◽  
Free Surface Displacement

This paper presents the experimental tests of a 16th-scale model of the Spar-buoy oscillating water column (OWC) carried out at a large scale wave flume. The model is slack-moored to the flume floor by two mooring lines. The turbine effect is replicated using calibrated orifice plates. The device six degree-of-freedom motion, inner free surface displacement and air chamber pressure are measured. The influence of wave height, turbine damping and mass distribution on the system dynamics is analysed for regular waves. An in-house developed numerical time-domain model is used to simulate the motion and power absorption under the same wave conditions as the physical model tests. The formulation considers linear hydrodynamic forces, viscous drag effects and drift forces. The floater is assumed to oscillate in six degrees of freedom and the OWC can move vertically in the tube. The mooring system is simulated using a quasi-static model. The comparison between experiments and numerical simulations shows a good agreement for wave periods outside the zone where parametric resonance in roll and pitch occurs.

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