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Hydrodynamic performance of multiple co-axial heave plates with different diameters
, Article Ships and Offshore Structures ; Volume 15, Issue 4 , 2020 , Pages 380-392 ; Behzad, M ; Thiagarajan, K. P ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Heave plates are structural components of a floating structure whose primary purpose is to increase damping and added mass in heave or pitch direction. If multiple plates are stacked along a common axis, then the relative diameters and spacing in between are important factors affecting the performance. In the present study, hydrodynamic coefficients of single, double and triple disks are experimentally investigated in different arrangements as Uniform, Concave and Convex edge shapes. It is observed that each disk in a multiple arrangement with lower diameter ratio have better hydrodynamic performance compared to the cases with higher diameter ratio when the spacing is small compared to the...
Experimental and Numerical Investigation on the Hydrodynamic Properties of Heave Plates in Translational and Rotational Oscillations
, Ph.D. Dissertation Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Many offshore platforms as TLP, Semi-submersible and Spar are used for oil extraction and energy harvesting. One of the challenges of these structures is related to vibrations due to the environmental sea waves and wind loads. The optimal way for the response reduction of an offshore structure in heave direction is the installing of thin heave plate. The heave plate induces vortex shedding and pressure drop on fluid flow downstream. Diameter difference of heave plates in an array can improve the obtained damping and added mass for a given small spacing between plates, which has not been studied up to now. Hence, in the present thesis it was observed that converting of the uniform to...
Design and Simulation of a Spar_Buoy Wave Energy Converter Using Piezoelectric Materials
, M.Sc. Thesis Sharif University of Technology ; Tabeshpour, Mohammad Reza (Supervisor) ; Abbaspour, Madjid (Supervisor)
Abstract
Nowdays, the world’s need for energy from renewable sources is increasing due to the excessive use of non - renewable resources and the pollution of the environment. Energy converters are classified into three general types: electromagnetic, electrostatic, and piezoelectric, in which piezoelectric materials are used in converters that convert mechanical energy into electrical energy (and vice versa). In the last decade there has been extensive research into the use of these materials for self-charging of low consumption electrically-powered devices such as sensors. For this purpose, in this study, a new method for harvesting electrical energy from the sea using piezoelectric elements is...
Vortex shedding modes around oscillating non-uniform double heave plates
, Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; 2020 ; Alvandi, M ; Behzad, M ; Thiagarajan, K. P ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
Multiple co-axial heave plates of uniform geometry are attached to offshore platforms for inducing damping and added mass. These effects generally decrease the magnitude of the dynamic response of the platform under applied environmental excitation forces. When spacing between heave plates is decreased the damping and added mass performance are altered due to their strong vortex interaction. A new non-uniform plate configuration is proposed that may create different hydrodynamic characteristics. The modes of vortex shedding around plate edges in a non-uniform arrangement under forced harmonic oscillation are investigated via the CFD method. Furthermore, a new simplified formula for the total...
Hydrodynamic damping enhancement by implementing a novel combined rigid-elastic heave plate
, Article Journal of Marine Science and Technology (Japan) ; 2020 ; Behzad, M ; Thiagarajan, K ; Sharif University of Technology
Springer
2020
Abstract
Heave plates are structural components used for reducing the vibrations caused by environmental forces on marine and offshore structures by changing the hydrodynamic properties. The fact that the added mass increase via heave plates does not always lead to the structural response reduction underscores the role of damping in maintaining the vibration amplitude within allowable limits. In the present experimental study, a novel combined rigid-elastic design is used to improve the damping through the velocity increase in the elastic part and added mass creation in the central rigid part. The desired percentage of total added mass and damping can be adjusted by changing the rigid-to-elastic...