Loading...
Search for:
water-wave
0.005 seconds
Total 45 records
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...
Wave interaction pitch response of tension leg structures
, Article 13th International Congress on Sound and Vibration 2006, ICSV 2006, Vienna, 2 July 2006 through 6 July 2006 ; Volume 5 , 2006 , Pages 3508-3515 ; 9781627481502 (ISBN) ; Ataie Ashtiani, B ; Seif, M. S ; Golafshani, A. A ; Sharif University of Technology
2006
Abstract
Because of fluctuation in leg tension, pitch motion is very effective in fatigue and life safety of leg elements in tension leg structures (TLSs). In this paper exact solution for pitch vibration of a TLS interacting with ocean wave is presented. The legs are considered as elastic springs. The flow is assumed to be irrotational and single-valued velocity potentials are defined. The effects of radiation and scattering are considered in the boundary value problem. Because of linear behavior of legs during wave excitation, ignoring coupling effects with other degrees of freedom, the analytical solution of pitch response has good agreement with the real behavior of the structure
Viscous wave interaction due to motion of a surface wave over a sediment bed
, Article Journal of Offshore Mechanics and Arctic Engineering ; Volume 128, Issue 4 , 2006 , Pages 276-279 ; 08927219 (ISSN) ; Lawrence, G. A ; Sharif University of Technology
2006
Abstract
The results of a flume experiment and a theoretical study of surface wave motion over a fluidized bed are presented. It is shown that a resonant wave interaction between a surface wave and two interfacial waves at the interface of the fresh water and the fluidized bed is a strong mechanism for instability of the interface and the subsequent mixing of the layers. The interfacial waves are subharmonic to the surface wave and form a standing wave at the interface. The interaction is investigated theoretically using a viscous interaction analysis. It is shown that surface wave height and viscous effects are the determining factors in the instability mechanism. The results indicate that the net...
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...
Simulation of wave generated by landslides in Maku dam reservoir
, Article Prediction and Simulation Methods for Geohazard Mitigation - Proceedings of the International Symposium on Prediction and Simulation Methods for Geohazard Mitigation, IS-KYOTO 2009, 25 May 2009 through 27 May 2009 ; 2009 , Pages 91-96 ; 9780415804820 (ISBN) ; Ataie Ashtiani, B ; Sharif University of Technology
Abstract
In this work, impulsive wave generation and propagation generated by landslides are studied numerically for a real case. Maku dam reservoir, in the northwestern of Iran is considered as the case study. Generated wave heights, wave run-up, maximum wave height above the dam crest and the probable overtopping volume have been evaluated, using a two-dimensional numerical model (LS3D). This model is validated using available three-dimensional experimental data for simulating impulsive wave caused by sub-aerial landslides. Based on the results, the generated wave height for first and second scenarios are 12 m and 18 m respectively. The wave height of 8 m is observed close to dam body. Because of...
Simple model for exact heave motion of tension leg platform
, Article WSEAS Transactions on Mathematics ; Volume 5, Issue 5 , 2006 , Pages 500-506 ; 11092769 (ISSN) ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
2006
Abstract
In this paper the dynamic response of the leg of a tension leg platform (tether) subjected to the load simulated as ocean wave 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. Two continuous models are proposed to present the structural system and the mentioned effects. The problem is solved by means of non-harmonic Fourier expansion in terms of eigenfunctions obtained from a non-regular Sturm-Liouville system
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...
Second-order perturbation added mass fluctuation on vertical vibration of tension leg platforms
, Article Marine Structures ; Volume 19, Issue 4 , 2006 , Pages 271-283 ; 09518339 (ISSN) ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
2006
Abstract
Total motion in waves can be considered as a superposition of the motion of the body in still water and the forces on the restrained body. In this study the effect of added mass fluctuation on vertical vibration of tension leg platforms (TLP) in the case of vibration in still water for both free and forced vibration subjected to axial load at the top of the leg is presented. This effect is more important when the amplitude of vibration is large. Also this is important in fatigue life study of tethers. The structural model used here is very simple. Perturbation method is used to formulate and solve the problem. First- and second-order perturbations are used to solve the free and forced...
Real-time multi-band synthesis of ocean water with new iterative up-sampling technique
, Article Visual Computer ; Volume 25, Issue 5-7 , 2009 , Pages 697-705 ; 01782789 (ISSN) ; Sargazi Moghadam, M. H ; Famil Samavati, F ; Emadi, M ; Sharif University of Technology
2009
Abstract
Adapting natural phenomena rendering for realtime applications has become a common practice in computer graphics.We propose a GPU-based multi-band method for optimized synthesis of "far from coast" ocean waves using an empirical Fourier domain model. Instead of performing two independent syntheses for low- and high-band frequencies of ocean waves, we perform only low-band synthesis and employ results to reproduce high frequency details of ocean surface by an optimized iterative up-sampling stage. Our experimental results show that this approach greatly improves the performance of original multi-band synthesis while maintaining image quality. © Springer-Verlag 2009
Passive devices for wave induced vibration control in offshore steel jacket platforms
, Article Scientia Iranica ; Volume 16, Issue 6 A , 2009 , Pages 443-456 ; 10263098 (ISSN) ; Gholizad, A ; Sharif University of Technology
2009
Abstract
Performances of tuned mass dampers and friction dampers to mitigate the wave induced vibrations in jacket type offshore platforms have been compared in this study. Due to the random nature of ocean waves, a full stochastic analysis method has been used to evaluate the response of the structures equipped with these devices. A stochastic linearization technique has been used to take the nonlinear behavior of friction dampers into account. The developed mathematical formulation has been applied to evaluate the response of realistic models, and to find out the optimal values for the adjustable parameters of friction dampers. The results have been verified in comparison with time domain nonlinear...
Parallelized numerical modeling of the interaction of a solid object with immiscible incompressible two-phase fluid flow
, Article Engineering Computations (Swansea, Wales) ; Volume 34, Issue 3 , 2017 , Pages 709-724 ; 02644401 (ISSN) ; Nikbakhti, R ; Ghasemi, A ; Hedayati, F ; Malvandi, A ; Sharif University of Technology
Abstract
Purpose - A numerical method is developed to capture the interaction of solid object with two-phase flow with high density ratios. The current computational tool would be the first step of accurate modeling of wave energy converters in which the immense energy of the ocean can be extracted at low cost. Design/methodology/approach - The full two-dimensional Navier-Stokes equations are discretized on a regular structured grid, and the two-step projection method along with multi-processing (OpenMP) is used to efficiently solve the flow equations. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. The full...
Numerical simulation of wave generated by landslide incidents in dam reservoirs
, Article Landslides ; Volume 8, Issue 4 , 2011 , Pages 417-432 ; 1612510X (ISSN) ; Yavari Ramshe, S ; Sharif University of Technology
2011
Abstract
In this work, a two-dimensional fourth-order Boussinesq-type numerical model is applied to estimate the impact of landslide-generated waves in dam reservoirs. This numerical model has recently been extended for simulating subaerial landslides. The extended model is validated using available three-dimensional experimental data, and a good agreement is obtained. The numerical model is then employed to investigate the impact of landslide-generated waves in two real cases, the Maku and Shafa-Roud dam reservoirs in the northwestern and the north of Iran, respectively. Generated wave heights, wave run-up, maximum wave height above dam crest, and dam overtopping volume have been estimated for each...
Numerical modeling of turbulent surface wave motion using a coupled boundary element-finite difference technique
, Article 2008 ASME Fluids Engineering Division Summer Conference, FEDSM 2008, Jacksonville, FL, 10 August 2008 through 14 August 2008 ; Volume 1, Issue PART B , 2009 , Pages 1025-1029 ; 9780791848418 (ISBN) ; Fluids Engineering Division, ASME ; Sharif University of Technology
2009
Abstract
In this paper an effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the wave and boundary layer characteristics. A mixing-length theory is used for turbulence modeling. The results are compared with previous experimental data. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2008 by ASME
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...
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...
Modeling of forced vibration of marine structural systems under dynamic loads of sea waves
, Article 18th Australasian Coastal and Ocean Engineering Conference 2007, COASTS 2007 and the 11th Australasian Port and Harbour Conference 2007, PORTS 2007, Melbourne, VIC, 18 July 2007 through 20 July 2007 ; 2007 , Pages 560-565 ; 9781622764280 (ISBN) ; Kanani, A ; Farahani, R. J ; Sharif University of Technology
2007
Abstract
Predicting the reaction and function of marine structures towards sea waves, is of significant importance in the design of them. There are some uncertain parameters which can be optimized to increase safety factors as well as to decrease the costs. Knowing the maximum oscillation of marine structures due to dynamic forces will play a great role on structures' safe design. The objective of this paper is to employ a reliable numerical technique to analyze the interaction between marine structures and sea waves. Simulink is an object oriented dynamic simulation package. It can develop new analysis tools aimed at a better understanding and prediction of the physics that governs the behavior of...
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,...
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,...