Sharif Digital Repository

In order to design a ship with waterjet system, estimation of its hydrodynamic performance is crucial. Presence and operation of waterjet propulsion system changes the flow field and pressure distribution in bottom and stem of ship hull, so affect hydrodynamic performance of craft. In the present thesis, CFD analysis is applied to free surface flow around a waterjet propelled ship using ANSYS CFX software. Also a waterjet propulsion system is built and settled in a ship model and resistance and self propulsion tests are performed. In order to performing a systematic process in project, in the first step, pump design is performed with extracting optimum efficiency relations and cavitation... 

An important characteristic of sea waves is their high energy density, which is the highest among renewable energy sources. Many different types of wave-energy converters of various categories have been proposed yet. In this thesis the performance of a novel wave energy converter (WEC) is studied. The system, extracts the wave energy from heaving motion of a cylinder buoy in head seas. This heaving cylindrical floating buoy is tested with sinusoidal incident waves in a wave channel in marine engineering laboratory, Sharif University of Technology (SUT). The study begins with a thorough review on types of renewable energy and their application in Iran. Then an introduction to ocean wave,... 

Whenever and wherever there is shipping, there exist risks of marine accidents. Subsequently, such accidents at sea may result in potential economic loss,environmental pollution and fatalities. In fact, ship grounding accident is a type of marine accident that involves the impact of a ship on seabed or waterway side. It may result in the damage of the submerged part of the ship’s hull and in particularly the bottom structure; potentially leading to water ingress, which may at the end compromise the ship's structural integrity, stability, and finally safety. An overall view on groundings categorizes the accidents in two major groups: Soft Grounding and Hard Grounding. A soft grounding does... 

Internal combustion (IC) engines are the major source of motive power in the ships. as the severity of the energy dearth and environmental pollution, different researches try to increase the total efficiency and reduce emissions. one of the improvable method is to get waste heat energy and reuse it to produce electricity, cooling and heating. studies of energy balance for marine diesel engine shows that there is potential to recovery waste heat from these motors. in this study a combined electricity, cooling and heating system based on regenerative Rankine cycle with an open feedwater heater and with two open feedwater heater and absorption refrigeration cycle is offered to recover the... 

In recent years, ground source heat pumps (GSHPs) have received increasing attention for space heating and cooling, and domestic hot water production due to their high energy performance and low environmental impacts. The most common type of ground heat exchanger used in the GSHP systems is borehole heat exchanger (BHE) that consists of U-shaped tubes placed in the vertical boreholes. In this system, the heat is absorbed from or rejected to the ground by circulation of a fluid through the ground loop. The GSHP systems provide high seasonal performance factors when the ground loads are well balanced over the year. However, most buildings in cold or hot climates have unbalanced loads. When the... 

In recent years, planing boats have been used in more exposed areas, for instance as patrol boats, pilot boats, coast guard and small naval vessels. When such a small vessel operating in a rough-water environment, frequently experiences violent motions and vertical acceleration. Even on calm water, porpoising may occur and may be severe as the speed is increased. Operation of the crew, equipments and overall operability of the vessel always suffer from mentioned motions. In the present study, the impact of fixed and controlled interceptors on a planing crafts hydrodynamic and seakeeping quality is investigated through application of an experimental and theoretical methods. Two scaled-down... 

Nowadays, science and technology, once again, lead approach to renewable natural resources to access energy due to fossil resources restrictions. Growing need for energy, being concerned about exhaustion of fossil resources, environmental pollution caused by burning fossil materials, climate warming and the greenhouse effect and etc. are obvious evidences of aforesaid fact. On the other hand, oceans and seas are large reservoirs of energy which comes from sunlight, geothermal resources, Earth's rotation and gravity by means of mechanical and hydrothermal processes. During the years, many ideas were conducted to achieve and mine the mentioned enormous energy potential of the oceans and seas.... 

In this research, the feasibility of the usage of the Wells turbine for direct conversion of the hydro-mechanical energy of the surface waves is studied via analytical and numerical methodologies. The results produced, showed for the first time that the Wells turbine can be employed for such waves directly and the performance variables are quite reasonable and even efficient considering low cost of HKWT system and abundant availability of those waves. For the low-frequency waves, the turbine is tested for different wave velocities to discover the best angular velocity of the rotor in terms of performance and the rotational velocity of 300 RPM has been found to be the optimum amount. Further,... 

The ocean thermal energy conversion system is one of a variety of renewable marine energy that is made up of a thermodynamic cycle, and it uses the difference between the temperature of hot water at the ocean surface and cold water at the depths of the ocean to generate electricity. The closed cycle is one type in which the system uses a working fluid which its boiling point less than the boiling point of water. Increasing the temperature of the fluid inlet in the cycle increases the system efficiency, which has been applied in this study to increase the efficiency of the OTEC system. The required energy to increase this temperature has been achieved by adding a solar collector to this... 

Damage detection in all kinds of human-made structures has been given serious attention as one of the main branches of engineering sciences, and significant progress has been made in this field, especially in the field of civil engineering, aerospace and heavy industries. However, although this topic is discussed academically in the field of offshore structures for two decades, not much development has happened in practice and it is still in the stage of knowledge development. One of the most important characteristics of practical online damage detection methods is the ability to be used knowing little information about the modal characteristics of the structure. In this research, an attempt... 

Increasingenergy requirements, limitedfossil resources, environmental pollutioncaused byfossilfuels, global warmingand other factorshaveled tothe approach ofscience and technologyfor renewable energies. One of the renewable energies is the energy relevant to ocean currents that is mainlydue to theinteractionbetween thetidalattraction ofthe moon,sun andearth. In our country,due tothehigh tideon the southern coast, there isgood potentialto use thistype of energy. One of themost favorableareasformarinecurrentpower plantslocated inthe northern part ofthe islandof Qeshmchannel.In this thesis,to exploitthis potential, the newidea ofHunter tidalturbine was investigated,because... 

One of the biggest problems in improving the performance of submersible propellers is the acoustic standard in conventional propellers. Recently, new solutions in propellers geometry have been used to reduce non-cavitation noise. Designing CRP licenses is one of these methods. This research includes numerical analysis. Numerical analysis in this research solves RANS equations of flow and extraction of hydrodynamic parameters and impeller noise in Ansys software. The results of numerical hydrodynamic solution are validated by laboratory results.DTMB 4119 three-blade propeller is used for hydrodynamic and hydroacoustic validation. The solution of Lighthill equations by FW-H method is... 

The integration of renewable energy sources introduces several issues including islanding operation. Therefore, Islanding phenomenon should be detected by a fast and reliable islanding detection method. In this thesis an intelligent-based approach is proposed to detect islanding state for Photovoltaic (PV) and Doubly Fed Induction Generator (DFIG) units. Decision tree classification algorithm is chosen as weak classifier and by Adaptive Boosting (AdaBoost), detection accuracy is improved. 16 features are employed to construct feature vectors. Because of intermittency of renewable electricity generation, different states for PV and DFIG generation are assumed. Probable events are simulated... 

Petroleum is the main source of energy in the world. So, exploration and production of this strategic matter from earth and sea has a major importance. A large amount of this black gold is hidden under deep seas floors and extraction of these sources requires knowledge of design and technology of construction of deep water offshore platforms and equipments. Convetional Tension Leg Platform (CTLP), configured as 4 cloumns and 4 pontoons, is one of deep offshore platforms moored by several pretensioned tethers. The dynamic behavior characteristics of CTLPs are extracted in this thesis by numerical modeling of CTLP and regular wave interaction. A computer program PARADISE is developed in... 

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... 

One of the unusual features of some ceramic materials is the piezoelectric effect. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electrical field. In the last decades, many research has been done on the use of these materials for the self-charging low-power... 

It is possible to unload a transmission line for a while. In line restoration voltage and current of the line will have some dynamic changes. So the apparent impedance of distance relay will have dynamic changes. These changes may cause some bad results including entrance of apparent impedance to the operational zones of distance relay and even relay tripping. Consequently if relay trips, the line restoration process will stop and may not be possible.
So we want an algorithm to distinguish line restoration from short circuit condition and block the relay. This algorithm must be able to stop blocking if there is any fault in the operational zones of the relay.
In this thesis an... 

In recent decades, bio-inspired design has become a common approach among engineers. Research and study of biological systems show that these systems are very efficient and consume the least amount of energy in a definite process. Specifically, marine mammals and fishes are great sources of inspiration. As an example, recently vertical axis wind turbine farms have been designed and constructed inspired by schools of fish, to produce more electricity. Boxfishes (Teleostei: Ostraciidae) are known for their hydrodynamic stability and relatively low drag coefficient. Highly maneuverable underwater robots have been designed according to morphology of boxfishes. Furthermore, Mercedes-Benz has... 

In the present study, the objective was to obtain the forward and backward swimming equation for the fiery eel and the European Eel in the experimental section. Then, by processing the videos, swimming equations were extracted. The obtained equations were used to move the 3D eel geometry of the STAR-CCM + software. The purpose of numerical modeling is to study the effect of body amplitude and wave frequency on the forces applied on the eel body during swimming. Numerical simulations were performed for the three amplitudes of 0.1, 0.115, and 0.138m and four different frequencies of 1, 1.2, 1.2 Hz, and Reynolds number 3857. The results of numerical work show us that the increase in the wave... 

In recent decades, SPM system has become a great method for transferring petroleum products to tankers and vice versa. SPM technology has shown his confidence and operation abilities. Sea waves are the most important phenomenon to be considered in the design of coastal and offshore structures. In this study dynamic motion of SPM floating structure is modeled under sea waves loading. Mooring lines connected to structure is modeled by using static stability equations and equivalent stiffness matrix is computed. First the SPM floating structure motion is modeled in 2 dimension (3 degree of freedom) using the boundary element method in frequency domain under regular sea waves loading and the...