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Development of a Model to Investigate Energy Production Potential from Sea Applying GIS Technique
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Majid (Supervisor)
Abstract
The growing requirements for renewable energy production lead to the development of a new series of systems, including wave and tidal energy conversion systems. Due to their sensitivity and the impact of the aggressive marine environment, the selection of the most adequate location for these systems is a major and very important task. Several factors, such as technological limitations, environmental conditions, administrative and logistic conditions, have to be taken into account in order to support the decision for best location. The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called ‘the Atlas’) to map out wave and tidal resources...
Effect of Aquatic Plants on Hydrodynamic and Dispersion in the Wave Motion
, Ph.D. Dissertation Sharif University of Technology ; Jamali, Mirmosadegh (Supervisor)
Abstract
Aquatic plants play an important role in water environment. Increasing drag force, distorting the velocity and turbulence structures and other related parameters, are the results of the presences of plants. These changes affect the dispersion and mass transport in the aquatic areas. This thesis presents laboratory visualizations and measurements of wave motion, and passive solute surface dispersion (longitudinal and lateral) in arrays of cylinders, a model for emergent, rigid aquatic plants. In the range of (where is Keulegan–Carpenter number, is the maximum oscillatory velocity perpendicular to the cylinder axis, is the period of oscillation, and is the diameter of the cylinder), and (where...
A novel shape memory alloy-based element for structural stability control in offshore structures under cyclic loading
, Article Ships and Offshore Structures ; Volume 15, Issue 8 , 2020 , Pages 844-851 ; Alam, M. S ; Seethaler, R. J ; Zabihollah, A ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Wind and ocean waves highly influence the performance and functionality of structures, requiring an efficient control element. The structural behavior of one of the most recent structural control elements, namely shape memory alloys (SMA)-based control element, under cyclic loadings of oceans waves, has been investigated. Shape memory alloys are one of the attractive smart materials with the ability to return to the initial shape after experiencing large deformation. Experimental tests have been conducted to study the effects of cyclic loads on several specimens of the SMA wires. The SMA wires are being used in the SMA-based structural control system to dissipate the energy of external...
Experimental study on the interfacial instability of particle-laden stratified shear flows
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 40, Issue 4 , April , 2018 ; 16785878 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Springer Verlag
2018
Abstract
Turbidity currents are one of the more frequently observed types of stratified flows. In these currents, the density difference is created as a result of suspended particles. The interfacial instability of turbidity current is studied experimentally in the present research. Both Kelvin–Helmholtz and (asymmetric) Holmboe instabilities are observed during the experiments; the first one was downstream, and the second one was upstream of the obstacle. Kelvin–Helmholtz instability is observed by approximately zero (phase) speed with respect to the mean flow. With the aim of measuring spectral distribution of velocity fluctuations, the effects of some parameters are studied on interfacial waves;...
Numerical modeling of subaerial and submarine landslide-generated tsunami waves—recent advances and future challenges
, Article Landslides ; Volume 13, Issue 6 , 2016 , Pages 1325-1368 ; 1612510X (ISSN) ; Ataie Ashtiani, B ; Sharif University of University
Springer Verlag
Abstract
Landslide-generated waves (LGWs) are among natural hazards that have stimulated attentions and concerns of engineers and researchers during the past decades. At the same period, the application of numerical modeling has been progressively increased to assess, control, and manage the risks of such hazards. This paper represents an overview of numerical studies on LGWs to explore associated recent advances and future challenges. In this review, the main landslide events followed by an LGW hazard are scrutinized. The uncertainty regarding landslide characteristics and the lack of data concerning generated tsunami properties highlights the necessity of probabilistic analysis and numerical...
An investigation into the effect of pressure source parameters and water depth on the wake wash wave generated by moving pressure source
, Article Scientia Iranica ; Volume 25, Issue 4 , 2018 , Pages 2162-2174 ; 10263098 (ISSN) ; Binns, J ; Thomas, G ; Renilson, M ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
In this study, the effect of moving pressure source and channel parameters on the generated waves in a channel was numerically investigated; draught, angle of attack, and profile shape as parameters of pressure source, and water depth and blockage factor as channel parameters for wave height. Firstly, the chosen Computational Fluid Dynamics (CFD) approach was validated with the experimental data over a range of speeds. Then, the CFD study was conducted for further investigations. It was shown that that by enlarging draught, angle of attack, and beam of the pressure source, the wave height generated would be increased. Channel study showed that it was possible to increase the wave height...
Free water surface oscillations in a closed rectangular basin with internal barriers
, Article Scientia Iranica ; Volume 15, Issue 3 , Volume 15, Issue 3 , 2008 , Pages 315-322 ; 10263098 (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Sharif University of Technology
2008
Abstract
Thee enclosed basin has certain natural frequencies of seiche, depending on the geometry of the water boundaries and the bathymetry of water depths. Therefore, the variation in the water surface at a point becomes irregular, as caused by the combination of several natural frequencies, which may be considered as the superposition of sinusoidal frequency components of different amplitude. This paper is mainly concerned with the motion of an incompressible irrotational fluid in a closed rectangular basin with internal impervious barriers. An analytical solution is presented for predicting the characteristic of generated waves in these types of basin. The equations of free water surface...
First order perturbation solution for axial vibration of tension leg platforms
, Article Scientia Iranica ; Volume 14, Issue 5 , 2007 , Pages 414-423 ; 10263098 (ISSN) ; Tabeshpour, M. R ; Seif, M. S ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
The dynamic response of the leg (tether) of a Tension Leg Platform (TLP), subjected to axial load at the top of the leg, is presented. The structural model is very simple, but several complicated factors, such as foundation effect, buoyancy and simulated ocean wave load, are considered. As an application, the effect of added mass fluctuation on the dynamic response of the leg subjected to such a load is presented. This effect is important in the fatigue life study of tethers. A first order perturbation method is used, in order to formulate and solve the problem. The differential equation is solved by means of non-harmonic Fourier expansion, in terms of eigenfunctions obtained from a...
Seismic analysis of a system of dam-massed foundation-reservoir under inclined excitation
, Article JVC/Journal of Vibration and Control ; 2021 ; 10775463 (ISSN) ; Ghaemian, M ; Sharif University of Technology
SAGE Publications Inc
2021
Abstract
One of the acceptable assumptions in engineering practice is vertical propagation of earthquake waves. When the source of earthquake is located very deep in the ground, this assumption is valid, but for sources located in shallow ground, it loses its viability. In this study, linear seismic analysis of a system of concrete dam-massed foundation-reservoir is performed under inclined earthquake excitation. Both P- and SV-type earthquakes are considered for the purpose of the seismic analysis. To consider the effects of inhomogeneous waves for the case of SV wave propagation, post-critical angles are also considered in the analysis. To investigate the effects of earthquake frequency content on...
Seismic analysis of a system of dam-massed foundation-reservoir under inclined excitation
, Article JVC/Journal of Vibration and Control ; Volume 28, Issue 13-14 , 2022 , Pages 1769-1780 ; 10775463 (ISSN) ; Ghaemian, M ; Sharif University of Technology
SAGE Publications Inc
2022
Abstract
One of the acceptable assumptions in engineering practice is vertical propagation of earthquake waves. When the source of earthquake is located very deep in the ground, this assumption is valid, but for sources located in shallow ground, it loses its viability. In this study, linear seismic analysis of a system of concrete dam-massed foundation-reservoir is performed under inclined earthquake excitation. Both P- and SV-type earthquakes are considered for the purpose of the seismic analysis. To consider the effects of inhomogeneous waves for the case of SV wave propagation, post-critical angles are also considered in the analysis. To investigate the effects of earthquake frequency content on...
An EWA framework for the probabilistic-based structural integrity assessment of offshore platforms
, Article Marine Structures ; Volume 59 , 2018 , Pages 60-79 ; 09518339 (ISSN) ; Yaghubi Namin, Y ; Matin Nikoo, H ; Estekanchi, H ; Kimiaei, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Endurance Wave Analysis (EWA) is a novel, simple, economical but yet reliable method for the integrity assessment of offshore platforms against extreme irregular waves. The current paper presents a framework for the probabilistic assessment of offshore platforms based on EWA. The stochastic nature and the uncertainties in the ocean waves were taken into account by introducing a set of artificial, random and gradually intensifying wave trains. To simulate other uncertainties in the loading and the strength of the structure a Latin Hypercube Sampling (LHS) type of Monte Carlo Simulation (MCS) was employed. The EWA methodology and different structural performance criteria were considered. The...
Directional dependence of extreme metocean conditions for analysis and design of marine structures
, Article Applied Ocean Research ; Volume 100 , 2020 ; Imani, H ; Karimirad, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Marine structures are typically sensitive to the direction of wind and waves, especially in extreme metocean conditions. The extreme metocean conditions and their associated predicted directions are not easily reachable from traditional design methodologies. In this research, the most probable combinations of different extreme metocean conditions along with their associated direction are predicted for the HyWind Scotland wind farm, Scotland. To achieve this, the Hierarchical Bayesian Modeling approach is applied to define the Joint Probability Distribution Function (JPDF) of four combinations of metocean parameters, including wave direction, wind direction and wind-wave misalignment. The...
Stability analysis of parametric resonance in spar-buoy based on Floquet theory
, Article Ocean Engineering ; Volume 266 , 2022 ; 00298018 (ISSN) ; Abazari, A ; Behzad, M ; Hayatdavoodi, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Parametric resonance is a phenomenon caused by time-varying changes in the parameters of a system which may result in undesirable motion responses and instability. Floating bodies like ships and spar-buoys are prone to Mathieu instability mainly due to the instantaneous change of the metacentric height. With the fast-growing developments in Ocean Renewable Energy systems, spar-buoys are commonly used for wave energy convertors and floating wind turbines. Undesirable, unstable motions as a result of the parametric resonance can be problematic as it may cause inefficiency in operations and structural risk integrity. In this research, a new approach has been developed to investigate these...
Modeling and parallel computation of the non-linear interaction of rigid bodies with incompressible multi-phase flow
, Article Computers and Mathematics with Applications ; Volume 72, Issue 4 , 2016 , Pages 1055-1065 ; 08981221 (ISSN) ; Ghasemi, A. M ; Nikbakhti, R ; Ghasemi, A. R ; Hedayati, F ; Sharif University of Technology
Elsevier Ltd
Abstract
A computational tool is developed to capture the interaction of solid object with two-phase flow. The full two-dimensional Navier–Stokes equations are solved on a regular structured grid to resolve the flow field. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. A two-step projection method along with Multi-Processing (OpenMP) is employed to solve the flow equations. The computational tool is verified based on numerical and experimental data with three scenarios: a cylinder falling into a rectangular domain due to gravity, transient vertical oscillation of a cylinder by releasing above its equilibrium position,...
Experimental investigation of instability of fluid mud layer under surface wave motion
, Article Physics of Fluids ; Volume 34, Issue 3 , 2022 ; 10706631 (ISSN) ; Jamali, M ; Sharif University of Technology
American Institute of Physics Inc
2022
Abstract
Motivated by environmental impacts of surface-wave induced mixing of fluid mud with clear water in nearshore areas, this paper presents quantitative measurements of excitation of interfacial waves over a bed mud layer by a surface wave in a wave flume. After an initial fluidization process, a quasi-standing interfacial wave comprised of four interfacial waves was observed at the interface as a result of a resonant wave interaction with the surface wave. The interfacial waves were subharmonic to the surface wave and traveled at the maximum possible angle from it. The growth rate and kinematic properties of the interfacial waves were measured, and good agreement with theoretical predictions of...
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 technique for detection of interfacial waves forming a two-dimensional pattern
, Article Fluid Dynamics Research ; Vol. 46, issue. 1 , 2014 ; ISSN: 01695983 ; Fazeli M ; Jamali, M ; Sharif University of Technology
Abstract
In this paper, we consider resonant interaction between a surface wave and sub-harmonic interfacial waves forming a two-dimensional pattern at the interface between two fluid layers. The resulting interfacial pattern changes both in time and space. An image processing technique is proposed to extract information about the evolution of the component interfacial waves in a wave flume. The technique proved to give accurate and consistent results when applied to different stages of the interaction. The experimental measurements were used to verify the theoretical predictions. The method can be used for detection of some other wave motions
Dispersion around a circular cylinder in surface wave motion
, Article Scientia Iranica ; Vol. 21, issue. 3 , 2014 , p. 548-556 ; 10263098 ; Jamali, M ; Sharif University of Technology
Abstract
In this paper, we examine fluid flow and associated dispersion around a circular cylinder under progressive surface wave motion. The flow field and vortex shedding patterns were studied using flow visualization and Particle Image Velocimetry (PIV). Several patterns of vortex shedding were identified around a single cylinder. The vortex shedding patterns under progressive wave motion are similar to those observed in planar oscillatory flow, except in the way the vortices form and in the orientation they take. The observed vortex patterns in progressive wave motion are more unstable than those in planar oscillatory flow. Using particle tracking and the Lagrangian dispersion method, the...
Lattice Boltzmann method for simulating impulsive water waves generated by landslides
, Article Scientia Iranica ; Vol. 21, issue. 2 , 2014 , p. 318-328 ; 1026-3098 ; Sarfaraz, M ; Sharif University of Technology
Abstract
Impulsive water waves generated by landslides impose severe damage on coastal areas. Very large mass ows in the ocean can generate catastrophic tsunamis. Preventing damage to dams and coastal structures, and saving the lives of local people against landslide-generated waves, has become an increasingly important issue in recent years. Numerical modeling of landslide-generated waves is a challenging subject in CFD. The reason lies in the difficulty of determining the interaction between the moving solids and sea water, which causes complicated turbulent regimes around the moving mass and at the water surface. Submarine or aerial types of landslide can further complicate the problem. Up to now,...
Integrating constrained random waves in endurance time analysis of offshore structures subjected to sea waves
, Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 1 July 2012 through 6 July 2012 ; Volume 2 , July , 2012 , Pages 677-684 ; 9780791844892 (ISBN) ; Estekanchi, H ; Zeinoddini, M ; Golestani, M ; Sharif University of Technology
2012
Abstract
This paper introduces a novel methodology for design and assessment of offshore structures exposed to irregular sea waves. For this, Constrained NewWave (CNW) is integrated with the Endurance Time Analysis (ETA) methodology, which is basically developed for the performance based analysis of onshore structures to earthquake loads. In this approach, the offshore structure is simulated in time-domain under a set of calibrated intensifying wave functions. They are devised to represent a gradually increasing roughness of the sea state by time. A performance index such as base shear, drift or stress in a critical structural members are monitored until they reach to a predefined maximum value. A...