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    Modeling and Designing Dynamic Positioning System for an Underwater Vehicle

    , M.Sc. Thesis Sharif University of Technology Hatami Landi, Mohammad (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    The aim of this study is to design a control system for an autonomous underwater vehicle and evaluate this system for different missions. Due to the non-linear behavior of the target robot, both linear and non-linear behavior of the system was studied. Model Predictive control method has been implemented since it can outline both linear and non-linear controllers. The first non-linear dynamics of this robot, maneuvering equipment, and external disturbances (waves and ocean current) were modeled. Then, to design the linear controller, the equations of motion have been linearized around the working point(cruise speed). In order to analyze both designed controllers, various duties have been... 

    Numerical Simulation of Cavitation in Rigid Body Motion in Unsteady State

    , M.Sc. Thesis Sharif University of Technology Asnaghi, Abolfazl (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    In this thesis, cavitating flow over 2D/3D geometries of cavitators and projectile bodies in stationary and moving conditions are simulated using the "Volume of Fluid" (VOF) technique. The main application of VOF model is for simulating free surface flows. In this work, another capability is added to the VOF algorithm to solve for gas phase and by applying analytical-numerical mass transfer models, cavitation phenomenon is simulated. The developed algorithm precisely simulates the geometrical parameters of supercavities such as dimension and shape in a wide range of cavitation numbers. In addition, the flow parameters of supercavity such as drag coefficient, pressure coefficient inside the... 

    Design and Manufacture of Steam Jet Propulsion System

    , M.Sc. Thesis Sharif University of Technology Khani Sinige, Mahmood (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Nowadays, there is a focus on developing a propulsion system with higher efficiency and performance in comparison to conventional systems. Many diverse systems have been designed for the vessel propulsion and everyday, utilizing new ideas, their performance and energy consumption are being improved. Direct use of steam energy is a noble and new idea. In this research, the steam jet propulsion system has been explained and current worldwide research on the topic has been investigated. Considering the shortage of primary data in the field and the novelty of subject, required information for the manufacturing of a sample model of this special propulsion system has been gathered and a design for... 

    Planing Hull Longitudinal Motion Simulation

    , M.Sc. Thesis Sharif University of Technology Seif, Tayyebe (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Planing crafts in waves are characterized by large and violent vertical motion and acceleration. The hull structure is subjected to high impact loads and the crew experiences high transient vertical acceleration and in most cases the crew needs to lower speed in order to avoid damage to the hull.In recent years, interest on increasingly faster marine vehicles has remarkably grown. Typical planing monohulls are: patrol vessels, pilot boats, rescue vessels, coast guard vessels and small navy vessels. So the behavior of planing monohulls in waves has been a widely researched topic since more and more planing monohulls appeared.The accurate prediction of large amplitude ship motions in severe... 

    Simulation of Wave Propagation in the Sea

    , M.Sc. Thesis Sharif University of Technology Taheri, Masoud (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    In positioning and navigation, Sonar with utilization of sound waves in water environments is similar to the role of Radar in not watered (irrigated) environments. In the Sonar field, modeling and simulation of propagation of sound waves in the undersea environment is a fundamental and very important topic. Nowadays simulation is significant tool that allow to the researchers to predict the quality of Sonar function respect to the experimental conditions. For simulation and modeling of sound wave propagation are used two different methods; Wave theory and Ray theory. In the wave theory, because of the large volume of data, the interpretation of the results is hard. Also in this method cannot... 

    Design Control System for Reducing High Speed Catamaran Longitudinal Motion with Control Surfaces

    , M.Sc. Thesis Sharif University of Technology Jocar, Amir Hossein (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Increasing the speed of marine transportation services for specific mission and rapidly movement of persons or product always have been considered major issue in maritime industry. In recent years different technology have been used by high speed vessels manufacturer for increasing the safety of crew and passengers at sea. Catamaran is one of the most important high speed craft in marine transportation industry. High speed catamaran nonlinear behavior in high velocity is causing longitudinal instability and large motions. Active control surfaces like hydrofoil and interceptor can be used for reducing high speed catamaran motions in waves. This control surfaces react an adequate action... 

    Investigation of Bilge Keel Influence on Nonlinear Roll Motion of a Small Cargo Carrier

    , M.Sc. Thesis Sharif University of Technology Dehestani Esfandabadi, Hamid (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Generally, Vessels at sea are exposed to water waves. Large displacement of the vessel affects its performance, passengers’ and crews’ activities or duties. Based on the type of the displacement (translational/rotational) and the orientation about the reference axes, floating vessels are collapse onto 6 distinct categories. One of the above-mentioned displacements about the reference axis is rolling motion. Rolling motion is the rotation of the vessel about its longitudinal axis. This displacement may lead the commuters or crews to seasickness. Furthermore, greatness of this displacement increases the probability of damage to the goods. Moreover, performance of the propulsion systems grows... 

    Investigation of Resin Flow in Vacuum Infusion Process (VIP)

    , M.Sc. Thesis Sharif University of Technology Tajadod Khargerdi, Mohammad (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    The use of Vacuum Infusion Process (VIP) in some industries , to achieve optimal injection strategy is based on trial and error and it comes to the production of defective and unusable parts.The main problem is that no resin penetrate in some areas and creat dry spots and unsaturated resin regions Because of inadequate or incorrect positioning of the resin inlet and air outlet.Simulation is a powerful tool for understanding and identifying the behavior of resin flow and thereby save time and cost.In this research,in order to avoid the empirical testing of different injection techniques and avoid wasting time and cost in traditional methods of trial and error,the use of vacuum... 

    Modeling the Effects of Step and Spray Rails on Planing Hulls Hydrodynamics

    , M.Sc. Thesis Sharif University of Technology Aqajani, Alireza (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    High speed crafts due to their design, geometry, one of the parameters to improve the performance of hydrodynamic elements such as trim tabs, bow thruster, steps and Spray rails.Step is an element which change height of bottom and due to reduce wetted area and extra lift and finally cause to improve drag of vessel.In this thesis we have evaluated numerically and compared with experimental tests on planning crafts in calm water and waves, and the effects on the motions of floating and drag floating are compared.Numerical analysis is conducted to help Ansys.CFX software. First, to provide 2D modeling and analyzing real-bodies floating in calm water and waves with simple, step-paid. The... 

    Hydro-aerodynamic Mathematical Model and Optimization of WIG Craft Performance at Take-off Phase by Genetic Algorithm

    , Ph.D. Dissertation Sharif University of Technology Tavakkoli Dakhrabadi, Mohammad (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    In this thesis attempted to present practical hydro-aerodynanic model with low computational time and high accuracy for WIG craft with a compound wing, a catamaran hull form and a power augmented ram (PAR) platform at take-off phase. To achieve this innovation, aerodynamic and hudrodynamic model are coupled and dynamic air cushion between demi hull of catamaran under the wing was considered by modeling PAR platform with effect of flap. To validaty the results of hydro-aerodynanic model, two test models were producted and the results of hydro-aerodynanic model are compared with the experimental results that the presented results had good agreement with the experimental results. Influence of... 

    Reducing Ships Fuel Consumption by Adjusting Operational Trim and Draft

    , M.Sc. Thesis Sharif University of Technology Kazemipour Esferjani, Alireza (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Nowadays, the attempts to reduce fuel consumption, greenhouse gas emissions and atmospheric pollutants, and economic savings, besides alignment with new rules, have been become the top priorities in the marines industry. In order to satisfy these goals, many efforts have been undertaken, including the vessel's trim and draft optimization which has done both experimentally and numerically and also thrust system simulation, to set a logical link between the effects of trim and draft of the ship and the calculated value of the required thrust from simulation to be able to optimize the fuel consumption. In this method, the ship is considered at the specific draft and the trim in bow and stern... 

    Softer Supplying for Solve the Motion Equation for Mobile Submarine with Superstructure in Submerge Condition

    , M.Sc. Thesis Sharif University of Technology Foroughifar, Esmaeil (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Submarine is one of the strategic vehicles that its design depends on complex knowledge. Submarine design is very important for some countries because lack of information, and for this reason some submarines were bought from submarine designer countries. One of the important issues is maneuvering that it depends on motion conditions. To survey submarine motions assume that: Submarine is in submerge condition Submarine moves rapidly (dynamical maneuvering) and Trust forces determine To solving motion equation software was supply and simplifies motion equations. To simplifying motion equation some non-effective motion equations parameters were omitted by one symmetry plane. Then hull shape was... 

    Rudder and Propeller Interaction Analysis in Planing Craft

    , M.Sc. Thesis Sharif University of Technology Taheri, Mohammad (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Partially submerged propellers are new type of propellers which knowledges ragard them is limited. These propellers found a growing market ahead of them and expertsexpect to use these propellers for big vessels at high speeds. This type of propulsors do not lose their efficiences at high speeds and are assumped to be economical. Meanwhile due to continuosus hit to water surface, huge stresses are extered on tha blade witch needs to be fundamentally studied. Several researchers have studied the partially submerged propellers which unfortunately did not publish their results. Undergo less or more thrust and torques which in both cases the efficiency also increases. The use of numerical methods... 

    The Effect of Performance of Ships Propeller on its Maneuvering in Shallow and Deep Water

    , M.Sc. Thesis Sharif University of Technology Kargar, Soroush (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    In this thesis ship propeller performance in maneuvering conditions have been investigated which means an oblique flow condition for working propeller. Then results of these investigations have been put to use to simulate maneuvering using MMG equations. These calculations have been done to investigate nominal wake variations in different drift angles and depth conditions. In this project displacement vessel KVLCC2 and propeller POTSDAM VP1304 have been studied due to the abundance of experimental data. Calculations in this study have been carried in three steps: 1, calculation of nominal wake of the vessel in different drift angles and depths via CFD. 2, Using the results of previous... 

    Influence of Control Elements in Numerical Simulation of Ship Motions

    , M.Sc. Thesis Sharif University of Technology Mehdi Hoseyni, Amin (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Ship motion is one of the most complicated problems in hydrodynamics. These motions accompany with non linear phenomena and their modeling is very difficult. Analytical solution for governing equations for such problems is not possible and experimental study is very expensive. In this state we need remarkable time for investigating of influences of environmental condition changes. In previous research done by Jahanbakhsh and Panahi,a software created that could solve fluid domain and rigid body equations. But the software needs to be developed in some aspects. Aim of this research is expanding of rigid body motion section of software. The software is capable of getting force or moment and... 

    The Effect of Control Surfaces on Longitudinal Motions of High Speed Catamaran Vessels

    , Ph.D. Dissertation Sharif University of Technology Najafi, Amin (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    The purpose of this study is extracting a dynamic model of longitudinal motions of high speed catamaran in regular and irregular waves, and then motion control of vessels by using of foil control elements and interceptor. For simulating longitudinal motions in regular waves, at first the longitudinal hydrodynamic coefficients of vessels should be extracted, then by substituting extracted coefficients in cumminz equation and using system identification methods, some equations are presented to estimate longitudinal two degree of freedom motions of high speed catamaran in waves. In this thesis the extraction of hydrodynamic coefficients is based on both numerical and experimental methods. ANSYS... 

    Study of Drag Reduction of Ship by Different Coating and Paint

    , M.Sc. Thesis Sharif University of Technology Kianejad, Sadroddin (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Reduction ships resistance is the major issues that always been about moving the ship into a water. In the course of research, many scientists have been interest to resistance reduction. It is important protect the body of ship against damage caused by sticking marine algae and crustaceans as protection against corrosive agents. Marine organisms such as algae, crustaceans and bacteria stick on submerged surfaces and increase the ship resistance. In this thesis resistance reduction using coating is evaluated. Foul release paint make smooth surface and low surface energy therefore ship with foul release coating experience lower drag contrast ship with another coating in the unfouled condition.... 

    Performance Evaluation of a Flying Boat before Take-Off in Head Sea Condition

    , M.Sc. Thesis Sharif University of Technology Maali Amiri, Mojtaba (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    An assessment of the relative speeds and payload capacities of airborne and waterborne vehicles highlights a gap which can be usefully filled by a new vehicle concept, utilizing both hydrodynamic and aerodynamic forces. A high speed marine vehicle equipped with aerodynamic surfaces (called a Flying Boat, 'Aerodynamically Alleviated Marine Vehicle') is one such concept. The purpose of this thesis is to evaluate the performance of a Flying Boat before take-off in head sea condition. First, performance will be assessed in calm water, and then will be evaluated in waves. Performance is defined as the variation of Resistance Force and Trim Angle of a vessel in an arbitrary interval. This... 

    Nonlinear Ship Maneuvering Simulation

    , M.Sc. Thesis Sharif University of Technology FathiKazerooni, Mohammadreza (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Ship maneuvering simulation and prediction in preliminary design stages has been concerned since forty years ago due to accidents occurred to large vessels and so many efforts have been held to develop the methods for simulation of ship maneuvering. Standards concerning ship maneuvering have been presented by International Maritime Organization that is known as a criteria to evaluate maneuvering performance of the ships. Traditionally ship maneuvering has been simulated in deep water and without any environmental conditions such as wind, wave, marine currents and effects resulted by asymmetric flow around ship hull during waterway entrance and shallow waters. Furthermore by introducing the... 

    Mathematical Model for Longitudinal Motions of Hysucat Vessel with Respect to the Interaction Between Hydrofoil and Hull

    , M.Sc. Thesis Sharif University of Technology Hosseinzade, Saeed (Author) ; Seif, Mohammad Saeed (Supervisor)
    Abstract
    Dynamics modeling of high speed crafts in waves is one of the major problems in design precess. Mathematical models compared with other methods have lower cost for studying behavior of ships in waves. On the other hand, experimental methods may also be suitable for various problems. Due to nonlinear behavior of high speed crafts, dynamics modeling of these vessels will be. Combination of experimental and mathematical models to predict the precise dynamics of high speed craft in wave is a suitable method. In this study, a nonlinear method is used for predicting the motions of vessels in waves. In this method, nonlinear time domain behavior of vessel is studied. At first a monohull vessel...