scholarly journals Analytical Solution for Wave Diffraction by a Concentric Three-Cylinder System near a Vertical Wall

Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1876
Author(s):  
Zhenfeng Zhai ◽  
Weifeng Ye ◽  
Fei Xia ◽  
Lele Yang
Keyword(s):  
Analytical Solution ◽  
Wave Diffraction ◽  
Incident Angle ◽  
Vertical Wall ◽  
Addition Theorem ◽  
Hydrodynamic Performance ◽  
Critical Element ◽  
Linear Potential ◽  
Wave Loads ◽  
Ocean Engineering

In this study, a semi-analytical model was developed to study wave diffraction around a concentric three-cylinder system near a wall based on linear potential theory. As a critical element, the target problem is transformed into bidirectional incident wave diffraction around two concentric structures based on the image principle and an analytical solution is obtained through eigenfunction expansion combined with a matching technique and Graf’s addition theorem. The validity of the proposed model was verified by comparing its results to known values. Parametric studies on porosity, annular spacing, incident angle, space between the structure and wall, and water depth were performed. The hydrodynamic loads and free-surface elevations in the system were calculated and compared to those reported in existing works on impermeable and permeable cylinders near a wall. The results indicate that the wave loads and run-ups on the exterior cylinder increase significantly based on the existence of the wall. However, based on the presence of an exterior porous protective structure, a significantly reduced influence of the wall on the interior cylinder can be observed. Considering the widespread use of concentric circular structures in ocean engineering, it is essential to conduct study on the hydrodynamic performance of concentric systems near walls, which can provide useful information for the design of marine structures.

Water Wave Diffraction and Radiation by a Submerged Horizontal Circular Cylinder in Front a Vertical Wall

2020 ◽  
Author(s):  
Ai-jun Li ◽  
Yong Liu
Keyword(s):  
Circular Cylinder ◽  
Analytical Solutions ◽  
Wave Diffraction ◽  
Water Wave ◽  
Vertical Wall ◽  
Horizontal Cylinder ◽  
Linear Potential ◽  
Polar Coordinate ◽  
Horizontal Circular Cylinder ◽  
Unbounded Fluid

Abstract This article studies water wave diffraction and radiation by a submerged horizontal circular cylinder in front of a vertical wall under the assumption of linear potential flow theory. Based on the image principle, the hydrodynamic problem of a horizontal cylinder in front of a vertical wall is transformed into an equivalent problem involving symmetrical cylinders in a horizontally unbounded fluid domain. Then, analytical solutions for the present physical problem are developed using the method of multipole expansions combined with the shift of polar coordinate systems. The wave exciting forces on the cylinder as well as the added mass and radiation damping due to the cylinder oscillation are calculated. The analytical solutions converge very rapidly with the increasing truncated number of multipoles. Calculation examples are presented to examine the effects of different parameters on the hydrodynamic quantities of the cylinder. Results indicate that the hydrodynamic quantities of the cylinder in front of a vertical wall greatly differ from those in a horizontally unbounded fluid domain.

scholarly journals Hydrodynamic Performance of Submerged Plates During Focused Waves

2019 ◽  
Vol 7 (11) ◽  
pp. 389 ◽  
Author(s):  
Fang ◽  
Yang ◽  
Guo
Keyword(s):  
Potential Flow ◽  
Wave Structure ◽  
Flow Theory ◽  
Hydrodynamic Performance ◽  
Wave Loads ◽  
Ocean Engineering ◽  
Preliminary Calculation ◽  
Engineering Structures ◽  
Potential Flow Theory ◽  
Focused Wave

Submerged horizontal plates are widely employed in research of wave structure interaction as a simplification of coastal and ocean engineering structures. The hydrodynamic performance of submerged horizontal plates under focused waves has been seldom reported. Based on potential flow theory, this paper presents a general solution of the hydrodynamic pressure and wave forces exerted on submerged plates by a focused wave group. An existing experiment and two limiting cases are used to validate the accuracy of the present analytical model. With the validated model, the effect of wave properties and the configuration of the wave structure system on the hydrodynamic performance of submerged plates are investigated. It is found that the hydrodynamic performance of submerged horizontal plates varies with incident focused wave with different peak frequencies. The structural breadth significantly changes the hydrodynamic performance while the structural height has little influence. This paper shows the usefulness of potential flow theory for the preliminary calculation of wave loads on coastal and ocean engineering structures generated by focused waves.

A Numerical Simulation of Non-Linear Air-Gap for Deepwater Semi-Submersible Platform

2021 ◽  
Author(s):  
Zhuang Kang ◽  
Yansong Zhang ◽  
Haibo Sui ◽  
Rui Chang
Keyword(s):  
Air Gap ◽  
Second Order ◽  
Difference Frequency ◽  
Hydrodynamic Performance ◽  
Wave Loads ◽  
Order Difference ◽  
Motion Response ◽  
Nonlinear Motion ◽  
Non Linear ◽  
Simulation Results

Abstract Air gap is pivotal to the hydrodynamic performance for the semi-submersible platform as a key characteristic for the strength assessment and safety evaluation. Considering the metocean conditions of the Norse Sea, the hydrodynamic performance of a semi-submersible platform has been analyzed. Based on the three-dimensional potential flow theory, and combined with the full QTF matrix and the second-order difference frequency loads, the nonlinear motion characteristics and the prediction for air gap have been simulated. The wave frequency motion response, the second-order nonlinear air gap response and nonlinear motion response of the platform have been analyzed. By comparing the simulation results, the air gap response of the platform considering the nonlinear motion is more intense than the results simulated by the first-order motion without considering the second-order difference frequency loads. Under the heavy metocean conditions, for the heave and pitch motion of the platform, the non-linear simulation values for some air gap points and areas are negative which means the wave slam has been occurred, but the calculation results of linear motion response indicate that the air gap above has not appeared the wave slamming areas. The simulation results present that the influence of the second-order wave loads is a critical part in the air gap prediction for the semi-submersible platform.

Numerical Modelling of a Heaving Point Absorber in Front of a Vertical Wall

2013 ◽  
Author(s):  
Julius Schay ◽  
Joydip Bhattacharjee ◽  
C. Guedes Soares
Keyword(s):  
Numerical Modeling ◽  
Numerical Modelling ◽  
Vertical Wall ◽  
Large Body ◽  
Hydrodynamic Performance ◽  
Large Structure ◽  
Energy Converter ◽  
Point Absorber ◽  
Individual Point ◽  
Heading Angle

The hydrodynamic performance of a heaving point absorber as a wave energy converter near a large body is studied through numerical modeling. First the study is performed for an individual point absorber in the absence of large structure and the results are compared with the results available in the literature. Next, the performance of a point absorber floating in the vicinity of a large body, which is considered as a fixed vertical wall, is investigated. The efficiency of the power absorption in regular and irregular seas is examined based on different floater sizes, floater shapes, drafts, wave heading angle and positioning of the floater. Numerical simulations are based on hydrodynamic forces and coefficients, obtained with the commercial software WAMIT.

Effects of a Nonabsorbable Gas on Interfacial Heat and Mass Transfer for the Entrance Region of a Falling Film Absorber

1996 ◽  
Vol 118 (1) ◽  
pp. 45-49 ◽  
Author(s):  
T. A. Ameel ◽  
H. M. Habib ◽  
B. D. Wood
Keyword(s):  
Mass Transfer ◽  
Water Vapor ◽  
Analytical Solution ◽  
Liquid Film ◽  
Heat And Mass Transfer ◽  
Vertical Wall ◽  
Lithium Bromide ◽  
Entrance Region ◽  
Falling Film ◽  
Aqueous Lithium Bromide

An analytical solution is presented for the effect of air (nonabsorbable gas) on the heat and mass transfer rates during the absorption of water vapor (absorbate) by a falling laminar film of aqueous lithium bromide (absorbent), an important process in a proposed open-cycle solar absorption cooling system. The analysis was restricted to the entrance region where an analytical solution is possible. The model consists of a falling film of aqueous lithium bromide flowing down a vertical wall which is kept at uniform temperature. The liquid film is in contact with a gas consisting of a mixture of water vapor and air. The gas phase is moving under the influence of the drag from the falling liquid film. The governing equations are written with a set of interfacial and boundary conditions and solved analytically for the two phases. Heat and mass transfer results are presented for a range of uniform inlet air concentrations. It was found that the concentration of the nonabsorbable gas increases sharply at the liquid gas interface. The absorption of the absorbate in the entrance region showed a continuous reduction with an increase in the amount of air.

Predicted wave field in a laboratory wave basin

1990 ◽  
Vol 17 (6) ◽  
pp. 1005-1014 ◽  
Author(s):  
Michael Isaacson ◽  
Shiqin Qu
Keyword(s):  
Wave Field ◽  
Wave Diffraction ◽  
Diffraction Theory ◽  
Ocean Engineering ◽  
Laboratory Facilities ◽  
Rectangular Basin ◽  
Diffraction Wave ◽  
Wave Basin ◽  
Wave Generator ◽  
Reflection Boundary

The present paper describes a numerical method for predicting the wave field produced by a segmented wave generator undergoing specified motions in a wave basin which may contain partially reflecting sides. The approach used is based on linear diffraction theory and utilizes a point source representation of the generator segments and any reflecting walls that are present. The method involves the application of a partial reflection boundary condition, which is discussed. Numerical results are presented for the propagating wave field due to specified wave generator motions in a rectangular basin. Cases that are considered include both perfectly absorbing and partially reflecting beaches along the basin sides, as well as the presence of perfectly reflecting short sidewalls near the generator. The method appears able to account adequately for the effects of wave diffraction and partial reflections, and to predict the generated wave field realistically. Key words: coastal engineering, hydrodynamics, laboratory facilities, ocean engineering, wave diffraction, wave generation, wave reflection.

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