Numerical Simulations of Regular Waves in a Hydrodynamic Laboratory Basin

2012 ◽  
Author(s):  
Monica Campos Silva ◽  
Marcelo de Araújo Vitola ◽  
Waldir Terra Pinto ◽  
Carlos Antônio Levi
Keyword(s):  
Numerical Model ◽  
Practical Importance ◽  
Numerical Algorithms ◽  
Physical Modelling ◽  
Wave Theory ◽  
Offshore Structures ◽  
Stokes Wave ◽  
Regular Waves ◽  
Ansys Cfx ◽  
Commercial Code

Hydrodynamic behavior of offshore floating structures is of fundamental practical importance to engineers and designers. Physical modelling of offshore structures in hydrodynamic laboratory is a common practice in this field. Due to the increasing in the computer power and the development of the numerical algorithms, the use of the numerical wave tanks (NWT) have become a complementary tool to the model tests. The knowledge of the drawbacks of numerical model is an important issue for engineers and researchers, especially in the models whose governing equations do not have exact solution. This work presents the application of numerical model to simulate the generation and propagation of regular waves in the LabOcean Basin (LabOceano/ COPPE/UFRJ) using the commercial code Ansys-CFX. A cross-section of the offshore basin have been used. Waves have been generated by flap type wavemaker. Period wave in the range from 1.75 to 3.00 seconds have been simulated. For all tests, the analytical wave steepness is smaller than 0.017. Numerical results have been compared with Stokes wave theory and experimental data obtained in the offshore basin. Both the behavior of the free surface and the reflection coefficient have been evaluated. Good agreement was found for the wave profile, mean wave height and mean wave period. Divergences between numerical and experimental results were found evaluating the reflection parameters.

Numerical model of the hydrowave laboratory for studying the interaction of sea waves with hydrotechnical structures

2019 ◽  
pp. 86-105
Author(s):  
Игорь Сергеевич Нуднер ◽  
Константин Константинович Семенов ◽  
Владимир Валентинович Лебедев ◽  
Гаяз Салимович Хакимзянов ◽  
Юрий Николаевич Захаров
Keyword(s):  
Numerical Model ◽  
Numerical Algorithms ◽  
Physical Modelling ◽  
Hydraulic Engineering ◽  
Laboratory Research ◽  
Design Solution ◽  
Hydraulic Structures ◽  
Sea Waves ◽  
Effective Use ◽  
The Cost

Рассмотрены вопросы, связанные с построением и областью применения численной модели гидроволновой лаборатории как инструмента, позволяющего в некоторых ситуациях отказаться от физического моделирования и заменить его численным, удешевить и ускорить ряд этапов проектных работ в гидротехническом строительстве. Представлены математические модели и численные алгоритмы, которые могут войти в состав численной лаборатории и использоваться для численного моделирования процессов генерации поверхностных волн, их распространения и взаимодействия с прибрежными и морскими сооружениями. Перечислены требования к программному обеспечению численной модели гидроволновой лаборатории, выполнение которых позволит эффективнее использовать этот инструмент инженерами-гидротехниками при проектировании гидротехнических сооружений. In the design of hydraulic structures and facilities of the coastal infrastructure, one of the main methods of confirming the claimed characteristics of the constructed facilities is the implementation of physical modelling in special hydrowave laboratories. However, the use of physical modelling as a tool for determining the most rational characteristics and parameters of hydraulic structures is very limited due to the high cost and, as a rule, the high complexity of the relevant studies. For this reason, it is virtually impossible to resort to this type of study in situations where a significant number of different project options need to be sorted out. The way out of the situation is the use of numerical modelling methods that allow you to choose the most suitable option. In fact, there is a need for a numerical model of the hydrowave laboratory, which allows abandoning the physical modelling in appropriate situations and replacing it with a numerical one. In this case, it will be possible to achieve important advantages: to reduce the cost and speed up the process of choosing the rational parameters of the design solution in hydraulic engineering, to give sufficient justification for the decision before its final verification by physical modelling. Thus, the combination of numerical studies of the proposed design solutions and physical modelling of the final result in order to confirm compliance with the requirements meets the needs of design studies in hydraulic engineering. In this paper, we consider the issues related to the construction and the domain of the numerical model of the hydrowave laboratory, as a tool that allows in some situations to abandon the physical modelling and replace it with a numerical one. Mathematical models and numerical algorithms that can be included in the numerical laboratory and used for numerical simulation of the processes of generation of surface waves, their propagation and interaction with coastal and marine structures are presented. The requirements are given for the software of the numerical model of the hydrowave laboratory, the implementation of which will ensure the effective use of this tool by hydraulic engineers in the design of hydraulic structures. Examples of successful use of mathematical technology to improve the efficiency of laboratory research are given.

Conditional Short-Crested Waves in Shallow Water and With Superimposed Current

2002 ◽  
Author(s):  
Jo̸rgen Juncher Jensen
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Wave Spectrum ◽  
Wave Theory ◽  
Ocean Waves ◽  
Offshore Structures ◽  
Stokes Wave ◽  
Wave Crest ◽  
Non Linear ◽  
Drilling Rigs

For bottom-supported offshore structures like oil drilling rigs and oil production platforms, a deterministic design wave approach is often applied using a regular non-linear Stokes’ wave. Thereby, the procedure accounts for non-linear effects in the wave loading but the randomness of the ocean waves is poorly represented, as the shape of the wave spectrum does not enter the wave kinematics. To overcome this problem and still keep the simplicity of a deterministic approach, Tromans, Anaturk and Hagemeijer (1991) suggested the use of a deterministic wave, defined as the expected linear Airy wave, given the value of the wave crest at a specific point in time or space. In the present paper a derivation of the expected linear short-crested wave riding on a uniform current is given. The analysis is based on the conventional shallow water Airy wave theory and the direction of the main wind direction can make any direction with the current. A consistent derivation of the wave spectrum taking into account current and finite water depth is used. The numerical results show a significant effect of the water depth, the directional spreading and the current on the conditional mean wave profile. Extensions to higher order waves are finally discussed.

scholarly journals Development of a wave-current numerical model using Stokes 2nd Order Theory

2019 ◽  
Vol 2 (1 (Nov)) ◽  
pp. 1-14
Author(s):  
Catherine Lloyd ◽  
Tim O'Doherty ◽  
Allan Mason-Jones
Keyword(s):  
Numerical Model ◽  
Experimental Testing ◽  
Order Theory ◽  
Multiphase Model ◽  
Flow Conditions ◽  
Regular Waves ◽  
Ansys Cfx ◽  
Testing Facility ◽  
Uniform Current ◽  
Current Characteristics

The optimisation of a Numerical Wave Tank is proposed to accurately model the sub surface conditions generated by regular waves superimposed on a uniform current velocity. ANSYS CFX 18.0 was used to develop a homogenous multiphase model with volume fractions to define the different phase regions. By applying CFX Expression Language at the inlet of the model, Stokes 2nd Order Theory was used to define the upstream wave and current characteristics. Horizontal and vertical velocity components, as well as surface elevation of the numerical model were compared against theoretical and experimental wave data for 3 different wave characteristics in 2 different water depths. The comparison highlighted the numerical homogeneity between the theoretical and experimental data. Therefore, this study has shown that the modelling procedure used can accurately replicate experimental testing facility flow conditions, providing a potential substitute to experimental flume or tank testing.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

scholarly journals Eddy Phase Speeds in a Two-Layer Model of Quasigeostrophic Baroclinic Turbulence with Applications to Ocean Observations

2016 ◽  
Vol 46 (6) ◽  
pp. 1963-1985 ◽  
Author(s):  
Lei Wang ◽  
Malte Jansen ◽  
Ryan Abernathey
Keyword(s):  
Practical Importance ◽  
Phase Speed ◽  
Wave Theory ◽  
Inverse Cascade ◽  
Barotropic Mode ◽  
Eddy Fluxes ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Ocean Observations ◽  
Shed Light

AbstractThe phase speed spectrum of ocean mesoscale eddies is fundamental to understanding turbulent baroclinic flows. Since eddy phase propagation has been shown to modulate eddy fluxes, an understanding of eddy phase speeds is also of practical importance for the development of improved eddy parameterizations for coarse resolution ocean models. However, it is not totally clear whether and how linear Rossby wave theory can be used to explain the phase speed spectra in various weakly turbulent flow regimes. Using linear analysis, theoretical constraints are identified that control the eddy phase speed in a two-layer quasigeostrophic (QG) model. These constraints are then verified in a series of nonlinear two-layer QG simulations, spanning a range of parameters with potential relevance to the ocean. In the two-layer QG model, the strength of the inverse cascade exerts an important control on the eddy phase speed. If the inverse cascade is weak, the phase speed spectrum is reasonably well approximated by the phase speed of the linearly most unstable mode. A significant inverse cascade instead leads to barotropization, which in turn leads to mean phase speeds closer to those of barotropic-mode Rossby waves. The two-layer QG results are qualitatively consistent with the observed eddy phase speed spectra in the Antarctic Circumpolar Current and may also shed light on the interpretation of phase speed spectra observed in other regions.

Effects of Stator Configurations on the Flotation Performance of Induced Gas Flotation Machine

2016 ◽  
Author(s):  
Ji-Gu Lee ◽  
Ji-Yun Kang ◽  
Youn-Jea Kim
Keyword(s):  
Flow Characteristics ◽  
Chemical Plants ◽  
Oil Sand ◽  
Two Phase ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Flotation Cell ◽  
Flotation Performance ◽  
Forced Air ◽  
Phase Water

Induced Gas Flotation (IGF) vessel is used for water treatment of plant industries such as oil sand and chemical plants. An understanding of the interaction between the stator and rotor is essential for the design of IGF with consideration of geometric blade configuration is essential for the design of IGF. In this study, the effect of the number of stator blades on flotation performance was numerically investigated using the commercial code, ANSYS CFX ver. 16.1. The two-phase (water and air) flow characteristics in the forced-air mechanically stirred Dorr-Oliver flotation cell were considered. The flotation performance was evaluated on the basis of the correlations among the number of stator blades (8, 12, 16, 20, 24), power number and void fraction. By comparing the result of each case, the newly designed model with 12 stator blades which had the highest flotation performance was derived.

scholarly journals Drag reduction in a class 8 truck - scaled down model

2018 ◽  
Vol 172 ◽  
pp. 01003
Author(s):  
R Vishwa Krishna. ◽  
R Suwathy. ◽  
M Pragadeesh. ◽  
M Venkatesan.
Keyword(s):  
Numerical Model ◽  
Drag Coefficient ◽  
Heavy Duty ◽  
Commercial Vehicles ◽  
Heavy Load ◽  
Ansys Fluent ◽  
Commercial Code ◽  
Class 8 Truck ◽  
Gap Width ◽  
Front Radius

Trucks are heavy load vehicles used mainly for commercial transport operations. There are several classes of heavy duty commercial vehicles classified based on the weight loaded. More than 50% of the engine output power in such trucks is utilized to overcome the drag. Drag force in automobiles is the resistance offered by air on vehicles at higher speeds. Class 8 trucks suffer higher drag when compared to other classes. In the present work, a numerical model is developed using a commercial code ANSYS FLUENT to predict the drag coefficient value. The effects of gap width and cab front radius with a constant fairing is analysed using the numerical model developed. A Class 8 model truck with minimal drag coefficient having constant fairing and optimized gap width between the trailer and cab is proposed.

scholarly journals BREAKWATER ARMOR DISPLACEMENT THRESHOLDS: A POSSIBLE CORRELATION WITH CUMULATIVE WAVE ENERGY

1984 ◽  
Vol 1 (19) ◽  
pp. 186
Author(s):  
Daniel L. Behnke ◽  
Frederic Raichlen
Keyword(s):  
Wave Energy ◽  
Wave Train ◽  
Wave Length ◽  
Simple Wave ◽  
Wave Theory ◽  
Irregular Waves ◽  
Reconstruction Technique ◽  
Regular Wave ◽  
Regular Waves ◽  
Three Dimensional Model

An extensive program of stability experiments in a highly detailed three-dimensional model has recently been completed to define a reconstruction technique for a damaged breakwater (Lillevang, Raichlen, Cox, and Behnke, 1984). Tests were conducted with both regular waves and irregular waves from various directions incident upon the breakwater. In comparison of the results of the regular wave tests to those of the irregular wave tests, a relation appeared to exist between breakwater damage and the accumulated energy to which the structure had been exposed. The energy delivered per wave is defined, as an approximation, as relating to the product of H2 and L, where H is the significant height of a train of irregular waves and L is the wave length at a selected depth, calculated according to small amplitude wave theory using a wave period corresponding to the peak energy of the spectrum. As applied in regular wave testing, H is the uniform wave height and L is that associated with the period of the simple wave train. The damage in the model due to regular waves and that caused by irregular waves has been related through the use of the cumulative wave energy contained in those waves which have an energy greater than a threshold value for the breakwater.

scholarly journals UPWARD FLOW AND HEAT TRANSFER AROUND TWO HEATED CIRCULAR CYLINDERS IN SQUARE DUCT UNDER AIDING THERMAL BUOYANCY

2020 ◽  
Vol 14 (1) ◽  
pp. 113-123
Author(s):  
H. Laidoudi
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Upward Flow ◽  
Square Duct ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Physical Phenomena

This paper presents a numerical investigation of mixed convection heat transfer around a pair of identical circular cylinders placed in side-by-side arrangement inside a square cavity of single inlet and outlet ports. The investigation provided the analysis of gradual effect of aiding thermal buoyancy on upward flow around cylinders and its effect on heat transfer rate. For that purpose, the governing equations involving continuity, momentum and energy are solved using the commercial code ANSYS-CFX. The distance between cylinders is fixed with half-length of cavity. The simulation is assumed to be in laminar, steady, incompressible flow within range of following conditions: Re = 1 to 40, Ri = 0 to 1 at Pr = 0.71. The main obtained results are shown in the form of streamline and isotherm contours in order to interpret the physical phenomena of flow and heat transfer. The average Nusselt number is also computed and presented. It was found that increase in Reynolds number and/or Richardson number increases the heat transfer. Also, aiding thermal buoyancy creates new form of counter-rotating zones between cylinders.

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