scholarly journals Resonant Periods of Seiches in Semi-Closed Basins with Complex Bottom Topography

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 181
Author(s):  
Ikha Magdalena ◽  
Nadhira Karima ◽  
Hany Qoshirotur Rif’atin
Keyword(s):  
Separation Of Variables ◽  
Bottom Topography ◽  
Small Error ◽  
Staggered Grid ◽  
Resonant Wave ◽  
Wave Elevation ◽  
External Forces ◽  
Volume Method ◽  
Resonant Period ◽  
Wave Induced

Seiches and resonances are two closely related phenomena that can cause damage to coastal areas. Seiches that occur in a basin at a distinct period named the resonant period may generate resonance when a wave induced by external forces enters the basin and has the same period as the seiches. Studying this period has become essential if we want to understand the resonance better. Thus, in this paper, we derive the resonant period in various shapes of semi-closed basin using the shallow water equations. The equations are then solved analytically using the separation of variables method and numerically using the finite volume method on staggered grid to discover the resonant period for each basin. To validate the numerical scheme, we compare its results against the analytical resonant periods, resulting in a very small error for each basin, suggesting that the numerical model is quite reliable in the estimation of the analytical resonant period. Further, resonant wave profiles are also observed. It is revealed that, in the coupled rectangular basin, the maximum wave elevation is disproportionate to the ratio of the length of the basin, while, in the trapezoidal basin, the ratio of the depth of the basin has no significant impact on the maximum wave elevation.

scholarly journals Wave Transmission by Rectangular Submerged Breakwaters

Computation ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 56
Author(s):  
Ikha Magdalena ◽  
Muh Fadhel Atras ◽  
Leo Sembiring ◽  
M. A. Nugroho ◽  
Roi Solomon B. Labay ◽  
...  
Keyword(s):  
Analytical Solution ◽  
Transmission Coefficient ◽  
Numerical Scheme ◽  
Separation Of Variables ◽  
Staggered Grid ◽  
Incoming Wave ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Before And After ◽  
Volume Method

In this paper, we investigate the wave damping mechanism caused by the presence of submerged bars using the Shallow Water Equations (SWEs). We first solve these equations for the single bar case using separation of variables to obtain the analytical solution for the wave elevation over a rectangular bar wave reflector with specific heights and lengths. From the analytical solution, we derive the wave reflection and transmission coefficients and determine the optimal height and length of the bar that would give the smallest transmission coefficient. We also measure the effectiveness of the bar by comparing the amplitude of the incoming wave before and after the wave passes the submerged bar, and extend the result to the case of n-submerged bars. We then construct a numerical scheme for the SWEs based on the finite volume method on a staggered grid to simulate the propagation of a monochromatic wave as it passes over a single submerged rectangular bar. For validation, we compare the transmission coefficient values obtained from the analytical solution, numerical scheme, and experimental data. The result of this paper may be useful in wave reflector engineering and design, particularly that of rectangle-shaped wave reflectors, as it can serve as a basis for designing bar wave reflectors that reduce wave amplitudes optimally.

scholarly journals Modeling and Fuzzy PDC Control and Its Application to an Oscillatory TLP Structure

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Cheng-Wu Chen
Keyword(s):  
Fuzzy Logic ◽  
Flow Field ◽  
Fuzzy Logic Controller ◽  
Separation Of Variables ◽  
Design Procedure ◽  
System Structure ◽  
Mathematical Framework ◽  
Control Force ◽  
Induced Flow ◽  
Wave Induced

An analytical solution is derived to describe the wave-induced flow field and surge motion of a deformable platform structure controlled with fuzzy controllers in an oceanic environment. In the controller design procedure, a parallel distributed compensation (PDC) scheme is utilized to construct a global fuzzy logic controller by blending all local state feedback controllers. The Lyapunov method is used to carry out stability analysis of a real system structure. The corresponding boundary value problems are then incorporated into scattering and radiation problems. These are analytically solved, based on the separation of variables, to obtain a series of solutions showing the harmonic incident wave motion and surge motion. The dependence of the wave-induced flow field and its resonant frequency on wave characteristics and structural properties including platform width, thickness and mass can thus be drawn with a parametric approach. The wave-induced displacement of the surge motion is determined from these mathematical models. The vibration of the floating structure and mechanical motion caused by the wave force are also discussed analytically based on fuzzy logic theory and the mathematical framework to find the decay in amplitude of the surge motion in the tension leg platform (TLP) system. The expected effects of the damping in amplitude of the surge motion due to the control force on the structural response are obvious.

The influence of numerical parameters in the finite-volume method on the Wigley hull resistance

2018 ◽  
Vol 233 (4) ◽  
pp. 1123-1132
Author(s):  
Martina Andrun ◽  
Branko Blagojević ◽  
Josip Bašić
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Resistance Force ◽  
Wave Elevation ◽  
Discretization Schemes ◽  
Wigley Hull ◽  
Discretization Errors ◽  
Volume Method

The equations discretization errors are often overlooked compared to the spatial discretization errors. This article presents the results of the influence of various equations discretization schemes in computational fluid dynamics on the prediction of the ship resistance and wave elevation on the hull. For the analysis, steady flow around a model of the Wigley hull is numerically predicted by employing a finite-volume method solver based on Reynolds-averaged Navier–Stokes equations and the volume-of-fluid method. Six momentum discretization schemes, three multi-fluid discretization schemes and three gradient schemes, are used in the analysis. The results show that the choice of discretization schemes has a significant influence on the results of wave elevation and resistance force in the case of the flow around the Wigley hull. In conclusion, second-order discretization schemes should be used for the resistance evaluation, in order to properly capture the non-linear effects.

Prediction of flow patterns in scoured beds caused by submerged horizontal jets

2006 ◽  
Vol 33 (1) ◽  
pp. 41-48 ◽  
Author(s):  
M Gunal ◽  
A Guven
Keyword(s):  
Boundary Layer ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Experimental Studies ◽  
Simple Algorithm ◽  
Rectangular Domain ◽  
Two Dimensions ◽  
Staggered Grid ◽  
Mean Flow ◽  
Volume Method

The basic goal of this study is to present a numerical simulation model for turbulent water flow issued on frozen scoured beds. The model uses a finite volume method to solve the equations of motion and transport equations for two dimensions on a transformed rectangular domain using boundary-fitted coordinates. The internal characteristics of the mean flow of submerged horizontal jets including surface profiles on frozen scoured beds are computed by a two-dimensional k–ε turbulence model. Computations are carried out at different frozen-scoured bed profiles. A staggered grid system is adapted for variable arrangements to avoid the well-known checkerboard oscillations in pressure and velocity. The SIMPLE algorithm is adapted for the computation. No experimental studies were performed during this investigation. The diffusion characteristics of the submerged jet, growth of boundary layer thickness, velocity distribution within the boundary layer, and shear stress at the scour are investigated and compared with the results of others. Key words: boundary-fitted coordinates, local scour, k–ε model, finite volume method, horizontal jets, submerged jets.

scholarly journals Survey on Experimental and Numerical Approaches to Model Underwater Explosions

2019 ◽  
Vol 7 (1) ◽  
pp. 15 ◽  
Author(s):  
Felipe Vannucchi de Camargo
Keyword(s):  
Mechanical Design ◽  
Weight Ratio ◽  
Experimental Tests ◽  
Smooth Particle Hydrodynamics ◽  
Lateral Torsional Buckling ◽  
Underwater Explosions ◽  
Particle Hydrodynamics ◽  
External Forces ◽  
Volume Method ◽  
Element Method

The ability of predicting material failure is essential for adequate structural dimensioning in every mechanical design. For ships, and particularly for military vessels, the challenge of optimizing the toughness-to-weight ratio at the highest possible value is essential to provide agile structures that can safely withstand external forces. Exploring the case of underwater explosions, the present paper summarizes some of the fundamental mathematical relations for foreseeing the behavior of naval panels to such solicitation. A broad state-of-the-art survey links the mechanical stress-strain response of materials and the influence of local reinforcements in flexural and lateral-torsional buckling to the hydrodynamic relations that govern the propagation of pressure waves prevenient from blasts. Numerical simulation approaches used in computational modeling of underwater explosions are reviewed, focusing on Eulerian and Lagrangian fluid descriptions, Johnson-Cook and Gurson constitutive materials for naval panels, and the solving methods FEM (Finite Element Method), FVM (Finite Volume Method), BEM (Boundary Element Method), and SPH (Smooth Particle Hydrodynamics). The confrontation of experimental tests for evaluating different hull materials and constructions with formulae and virtual reproduction practices allow a wide perception of the subject from different yet interrelated points of view.

scholarly journals NUMERICAL ALGORITHM OF SEISMIC ATTENUATION ESTIMATION IN ANISOTROPIC FRACTURED POROUS FLUID-SATURATED MEDIA

2021 ◽  
Vol 2 (2) ◽  
pp. 186-195
Author(s):  
Mikhail A. Novikov ◽  
Vadim V. Lisitsa
Keyword(s):  
Fluid Flow ◽  
Seismic Wave ◽  
Numerical Algorithm ◽  
Wave Attenuation ◽  
Seismic Attenuation ◽  
Staggered Grid ◽  
Filling Material ◽  
Seismic Wave Attenuation ◽  
Saturated Media ◽  
Wave Induced

In our work we investigate the effect of transport and elastic properties anisotropy on seismic attenuation due to fracture-to-fracture wave-induced fluid flow using numerical algorithm of estimation of seismic wave attenuation in anisotropic fractured porous fluid-saturated media. Algorithm is based on numerical solution of anisotropic Biot equations using finite-difference scheme on staggered grid. We perform a set of numerical experiments to model wave propagation in fractured media with anisotropic fractured-filling material providing wave-induced fluid flow within interconnected fractures. Recorded signals are used for numerical estimation of inverse quality factor. Results demonstrate the effect of fracture-filling material anisotropy on seismic wave attenuation.

Natural Convection in a Vertical Cavity Partially Filled With Porous Medium: Effect of Aspect Ratio, Darcy and Fluid Rayleigh Numbers

Volume 1 ◽  
2004 ◽  
Author(s):  
Sushant Anand ◽  
R. C. Arora
Keyword(s):  
Porous Medium ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Saturated Porous Medium ◽  
Darcy Number ◽  
Medium Effect ◽  
Staggered Grid ◽  
Medium Increase ◽  
Diffusive Fluxes ◽  
Volume Method

Numerical investigation of natural convection in a rectangular cavity partially filled with fluid-saturated porous medium has been carried out. Rayleigh number (104 to 107) and Darcy Number (10−1 to 10−10), Aspect Ratio (0.75, 1.0, and 1.25) are considered parameters. The governing equations have been solved numerically by SIMPLEC, a finite volume method on staggered grid arrangement. Power-law scheme has been used to approximate convective and diffusive fluxes. The results obtained are presented for the streamlines, isotherms and variation of Nusselt number at the walls. For values of Darcy Number above 10−4, a convective regime has been found to exist in which flow is nearly independent of Darcy Number, while at low values (below 10−6) the conduction dominated region occurs in the porous medium. Increase in Aspect Ratio increases intensity of circulation while maintaining the symmetry with respect to diagonals. Increase in aspect ratio increases the region of uniform temperature which covers most of the porous region.

Numerical Simulation of Effect of Nose Shape on Tunnel Entry/Exit Wave Induced by a High-Speed Train Passing through a Tunnel

2011 ◽  
Vol 97-98 ◽  
pp. 712-715
Author(s):  
Jian Lin Xu ◽  
Yuan Gui Mei ◽  
Fan Yang ◽  
Xin Liu
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
High Speed Train ◽  
High Speed Trains ◽  
Nose Shape ◽  
Volume Method ◽  
Wave Induced ◽  
Tunnel Entrance

The air flow around the high-speed train passing through a tunnel is three dimensional, compressible and unsteady in nature. This paper carried out the numerical simulation of it and evaluated the effect of nose shapes of high-speed trains on tunnel entry/exit waves radiated directly from tunnel entrance or exit. The elliptical, parabolic and conical nose shapes were analyzed. A commercial CFD code STAR-CD based on the finite volume method was used applying the SIMPLE algorithm and a moving grid technology. The comparison study shows that though the patterns of tunnel entry waves or exit waves induced by high-speed trains with above three nose shapes are similar, the amplitudes of them are different. The wave amplitude of elliptical shape is the highest, and that of conical shape is the lowest, which implies that with the nose shape be more streamlined and slender, it might be more likely to reduce the amplitudes of tunnel entry/exit waves.

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