Loading...
Search for:
breakwaters
0.006 seconds
Hydrodynamic Interactions of Artificial Reef using a Laboratory Model
,
M.Sc. Thesis
Sharif University of Technology
;
Borghei, Mahmoud
(Supervisor)
;
Aghtouman, Peyman
(Supervisor)
Abstract
Resources management is essential duo to sustainable development and marine resources limitations. There are several ways to restore coastal damaged ecosystems, one of the best and most cost effective solution is establishment of artificial reefs. A popular type of artificial reef is named Reef ball, a hollow hemisphere. In some regions these habitats has also been used as submerged breakwater. These structures recover and protect endangered species ecosystem although they provide aesthetic view to a beach. Main application of these structures is to provide a safe environment for marine creature. In this study initially Transmission coefficient variation in two-dimensional model experiments...
Numerical Modelling of Armour Layer Stability in Low-crested Breakwaters Using Smoothed Particle Hydrodynamics (SPH) and Discrete Element Method (DEM)
, Ph.D. Dissertation Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Rubble mound low-crested breakwaters protect the structures and ships in the port against wave attacks. Due to the overtopping, these structures provide a more attractive landscape and helps preserve the port's environment. Stability of low-crested breakwaters relies on the stability of the armor layer against the wave action, requiring the choice of the appropriate diameter for the armour blocks. For cubic armours that are of interest to the designers, there is currently no design relationship, and they inevitably use formulae specified for high-crested breakwaters that may not be in the safe side. The conventional method for determining the required armour diameter for a breakwater is...
Seismic Isolation of Structures using Trench Barriers
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Ground vibration induced by human activity such as industrial activities, Blasting, in construction or deconstruction operation. Ground vibration reaches the troublesome limit for men. In the densely populated urban regions and buildings housing, ground vibration has to be strictly controlled. Many vibration reduction methods have been proposed.A metod of protecting structures from dynamic loads is using trench wich will be located between the dynamic sources and the protected structures. Inappropriate designing of trenches will reduce its effect. In this research the effect of trenches and their different properties, such as type of material, width, trench depth, soil bed type and distance...
Numerical Analysis of the Armour Layer Stability in Rubble-Mound Breakwaters
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Rubble-mound breakwaters are one of the most customary breakwaters, which make a calm and safe area for ships to berth. To protect these structures from sea wave attacks, armour layers consisting of rocks or concrete blocks are put on their outer surface. Providing the stability of the armour layer is an important procedure in the design of breakwaters. Until now, design of the armour layer is based on the empirical formulae and physical modeling tests. The current research aims to study the stability of the armour layer by the numerical method and employing the commercial code FLOW-3D. In the present research, the effect of geometrical parameters such as breakwater slope and armour diameter...
A novel force-based approach for designing armor blocks of high-crested breakwaters
, Article Scientia Iranica ; Vol. 21, issue. 3 , 2014 , pp. 534-547 ; ISSN: 10263098 ; Sarfaraz, M ; Sharif University of Technology
Abstract
Rubble-mound breakwaters are common marine structures that provide a safe area for human coastal activities. The stability of these structures against sea-waves requires their seaward slope to be protected by an armor layer consisting of natural rock or concrete units. To provide a safe breakwater, it is reasonable to establish a relation between the exerted wave loads and the stability of the armor units. However, up to now, the empirical design equations, derived from model tests, relate wave parameters to armor weight, and keeps the effect of wave loads in a black box. In this paper, a new approach, based on numerically-derived wave loads on the armor, is presented to evaluate the...
A new design for floating offshore platforms
, Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE ; Volume 1 , 2012 , Pages 529-537 ; 9780791844885 (ISBN) ; England, G. L ; Moradkhan, E ; Valikhani, A. R ; Bahadori, M. R ; Sharif University of Technology
2012
Abstract
While for shallow waters the use of old offshore jackets still seems efficient and justifiable, for deep and ultra-deep waters such platforms cannot be used. During the past few decades the old generation of fixed offshore platforms was succeeded by the new floating platforms and new designs such as FPSOs. A new family of floating offshore platforms has been developed. These should be able to respond to size, weight and space for operating equipment, i.e. they can be constructed to have a wide range of load-bearing capacities. Use is made of the old concept of Life Saving Tubes, which in their simplest form can be a toroidal shaped tyre inner tube. The Torus-shaped idea can be further...
An integrated SPH-polyhedral DEM algorithm to investigate hydraulic stability of rock and concrete blocks: application to cubic armours in breakwaters
, Article Engineering Analysis with Boundary Elements ; Volume 84 , 2017 , Pages 1-18 ; 09557997 (ISSN) ; Pak, A ; Sharif University of Technology
Abstract
In this paper, a combination of the Lagrangian meshfree method of SPH and Polyhedral DEM is presented to simulate the interaction between the free surface of water and solid objects possessing sharp edges and flat surfaces, such as armour units of breakwaters. Both SPH and DEM schemes are validated successfully against experimental data. The numerical scheme is utilized to inspect the stability of concrete cubic armours in rubble-mound breakwaters through systematic analyses with various geometrical parameters and environmental conditions. The numerical results regarding the required dimensions of the cubic blocks for providing stability of the armour units under the wave attack are compared...
Floating bulk cascode class-e power amplifier
, Article IEEE Transactions on Circuits and Systems II: Express Briefs ; 2018 ; 15497747 (ISSN) ; Toofan, S ; Lotfi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In this paper, the switching behavior of the cascode topology is improved through the floating bulk (FB) technique. Although the cascode structure has the advantage of reducing voltage stress on transistors, its parasitic elements increase power loss. The FB technique has been proposed to alleviate the power loss in the cascode class-E PA topology which results in enhancement of power added efficiency (PAE). In this method, the bulk of the common-gate (CG) transistor is connected to the ground through a resistor. As a result, the parasitic capacitances between the drain and source of the CG transistor create a new path of current that accelerates charging of parasitic capacitance at the...
Numerical investigation of the stability of armour units in low-crested breakwaters using combined SPH–Polyhedral DEM method
, Article Journal of Fluids and Structures ; Volume 81 , 2018 , Pages 14-35 ; 08899746 (ISSN) ; Pak, A ; Sharif University of Technology
Academic Press
2018
Abstract
Low-crested breakwaters have become more attractive because they do not hinder the beautiful coastal landscape and are more environmentally friendly comparing to traditional breakwaters. The available formulae for design of these types of structures mainly focus on wave transmission, reflection and dissipation aspects. However, stability of the armour blocks are not directly taken into account in the design process. In this study the Lagrangian meshfree method of SPH along with a discrete element method i.e. Polyhedral DEM are used to simulate the interaction between the sea water waves with different characteristics and low-crested breakwaters constructed using cubic armour blocks. SPH is...
A quantitative and qualitative comparison of coarse grid generation techniques for numerical simulation of flow in heterogeneous porous media
, Article SPE Reservoir Simulation Symposium 2009, The Woodlands, TX, 2 February 2009 through 4 February 2009 ; Volume 1 , 2009 , Pages 55-73 ; 9781605607771 (ISBN) ; Mahani, H ; Firoozabadi, B ; Landmark; HALLIBURTON ; Sharif University of Technology
2009
Abstract
Applying upscaling techniques is an undeniable demand in reservoir simulation, considering the difference between level of details in a geological model and level of details that can be handled by reservoir simulators. Upscaling reservoir model involves first constructing a coarse grid by employing gridding algorithms and then computing average properties for coarse grid blocks. Although various techniques have been proposed for each of these steps, one has to be aware of strengths and weaknesses of each technique before attempting to apply them. In this paper, we focus on different gridding methods and evaluate their performances. Three main grid generation techniques are considered:...
Floating bulk cascode Class-E power amplifier
, Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Volume 66, Issue 4 , 2019 , Pages 537-541 ; 15497747 (ISSN) ; Toofan, S ; Lotfi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this brief, the switching behavior of the cascode topology is improved through the floating bulk (FB) technique. Although the cascode structure has the advantage of reducing voltage stress on transistors, its parasitic elements increase power loss. The FB technique has been proposed to alleviate the power loss in the cascode class-E PA topology which results in enhancement of power added efficiency (PAE). In this method, the bulk of the common-gate (CG) transistor is connected to the ground through a resistor. As a result, the parasitic capacitances between the drain and source of the CG transistor create a new path of current that accelerates charging of parasitic capacitance at the...
Experimental investigation on response and efficiency of moored pontoon type floating breakwaters
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 31, Issue 1 , 2007 , Pages 95-99 ; 03601307 (ISSN) ; Akbari, M ; Sharif University of Technology
2007
Abstract
This paper presents the experimental results of an investigation on the response and efficiency of floating pontoon type breakwaters. Random waves modeled by the Pierson Moskowits wave spectrum are used for various configurations of floating breakwaters. The experimental results are presented in graphs for the transmission coefficient as a function of incident wave length and height for breakwaters used in this study. The obtained results for the breakwaters of this study show that by increasing the wave period and length, the transmission coefficient increases, while increase in the mass and draft of the floating breakwater causes the transmission coefficient to reduce. © Shiraz University
Investigation of the effect of the added mass fluctuation and lateral vibration absorbers on the vertical nonlinear vibrations of the offshore wind turbine
, Article Nonlinear Dynamics ; Volume 103, Issue 2 , 2021 , Pages 1499-1515 ; 0924090X (ISSN) ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
In this article, the effects of the changes in the mass of the floating wind turbine (as a multi-body system) on its nonlinear vertical vibrations are investigated. The fluctuations of the hydrodynamic added mass of the floating platform and the mass of the vibration absorbers, which added to the structure to mitigate the lateral vibrations, change the mass and consequently the dynamics of the vertical vibrations. In this regard, first, the governing equations of the vertical vibrations of the floating wind turbine are derived. The FAST code is used to validate the proposed model of the dynamics of the vertical vibrations through numerical simulations. Then, derived equations are solved...
Large deformation finite element modeling of rubble mound breakwater built on soft seabed using coupled eulerian–lagrangian method
, Article Indian Geotechnical Journal ; Volume 51, Issue 2 , 2021 , Pages 315-328 ; 09719555 (ISSN) ; Shahir, H ; Pak, A ; Sharif University of Technology
Springer
2021
Abstract
For the design of rubble mound breakwaters on soft soil, it is essential to predict the behavior of soft soil and large deformations phenomena occurring in the course of construction of the rubble mound breakwater. Large deformations in various problems can be well simulated using the coupled Eulerian–Lagrangian (CEL) method. In this study, the CEL method has been used to simulate the rubble mounds construction on soft soil and predict the resulting settlements. To validate the numerical model, the results of three experiments conducted in the physical modeling laboratory at Kharazmi University were used. Also, two case studies of real rubble mound breakwaters constructed on soft seabeds...
Experimental study of scour due to breaking waves in front of vertical - Wall breakwaters
, Article 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, BC, 20 June 2004 through 25 June 2004 ; Volume 3 , 2004 , Pages 563-566 ; Jamali, M ; Sharif University of Technology
2004
Abstract
Scour is an important cause of instability of breakwaters. In case of vertical-wall breakwaters, toe scour can cause collapse of the whole structure. This paper is concerned with an experimental study of the effects of regular breaking waves on scour at toe of vertical-wall breakwaters. Experiments were carried out in a wave flume with regular waves for two cases of a beach with and without a breakwater. Bed profiles and scour depths for various wave heights, periods and depths were recorded. For the case of a beach without a breakwater, the observed bed profile types are compared to predictions. For the case of a beach with a breakwater, factors affecting the scour are investigated, and an...
Experimental studies on the effects of placement method and packing density of cubic armour units on the stability of low-crested breakwaters
, Article Ocean Engineering ; Volume 266 , 2022 ; 00298018 (ISSN) ; Pak, A ; Aliasgary, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Although concrete armour units have traditionally been used in two layers, the application of single-layer armour has attracted more attention in recent years because of its lower concrete volume and faster construction pace. Single-layer amour relies mainly on the contact between units to provide stability; however, installation of special armour types with surface projections for better interlocking, increases the possibility of breakage. During the last decade the idea of using bulky armour units such as cubes has been raised, and the application of these single-layer armour units has become common for high-crested breakwaters. However, the application of cube armours for low-crested...