scholarly journals NEARSHORE CIRCULATIONS DUE TO WAVE INDUCED CURRENTS BY OFFSHORE BREAKWATER IN FINITE ELEMENTS

1986 ◽  
Vol 1 (20) ◽  
pp. 150
Author(s):  
Shinn-Chung Liang

The objective of the present study is concerned with the numerical prediction of wave patterns and wave induced currents adjacent to a breakwater. The wave theory used is that of Berkhoff's (1972) mild slope wave equation with effects of diffraction, refraction and reflection described as Bettess, Liang and Bettess (1984). A finite element model is applied with appropriate boundary conditions. The singularity in the velocity at the tip of the breakwater is modelled effectively using the technique of Henshell and Shaw (1975), originally developed for elasticity. In the case of waves induced currents a potential representation of velocity in the fluid has be€>n used to derive a set of radiation stress expressions based on the theory of Longuet-Higgins (1964, 1970a,b), which are for an arbitrary wave pattern and the bottom variation. These expressions used account for the mean sea level and satisfy Mei's (1973) static balance of momentum flux. The radiation stress is applied to obtain forcing terms for use in a shallow water equation in conjunction with limiting ratio wave breaking where wave height, wave period, wave steepness and beach slope may be considered. Finally, an offshore breakwater on a beach for shore protection has been applied in a complete finite element model to predict both wave pattern and nearshore currents. Two angles of wave incidence are chosen. A series result has been produced.

Author(s):  
Jean-Roch Nader ◽  
Song-Ping Zhu ◽  
Paul Cooper ◽  
Brad Stappenbelt

Hydrodynamic characteristics of floating OWC can be quite difficult to predict especially when a strong coupling is present between the chamber pressure and the device movements. Mooring properties, and air pressure inside the chamber can also considerably influence the motion of the device and therefore the energy output. A newly developed 3D finite element model based on the linear wave theory has been applied to a cylindrical type OWC device. The study focused principally on the effects of the mooring restoring force and pressure pneumatic damping in the chamber total volume flux and energy conversion of the device. Results show that properly chosen parameters could effectively increase the efficiency band width of such devices.


2020 ◽  
Vol S-I (2) ◽  
pp. 224-229
Author(s):  
S. Ryabushkin ◽  

This paper identifies trim & draft parameters (spatial trimming) of a real fast boat with low-capacity motor, mostly running as a displacement vessel. The paper discusses various loading cases and calculates integral parameters in still water and regular waves (of various frequencies and incidence angles) for the ship at standstill and running at different speeds, also giving response-amplitude operators (RAOs) of motions and wave-induced moments. The study also gives calculation results for threedimensional fields of hydrostatic and hydrodynamic pressures and acceleration for further analysis of stress-strain state taking into account that finite-element model has no supports. High compliance (both global and local) of non-metal hull implies that the procedure suggested in this paper could be experimentally validated in future.


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