Sharif Digital Repository

Nowadays, autonomous underwater vehicles (AUVs) are implemented to carry out various activities under water. Amongst applications of these vehicles we can mention monitoring of marine creatures, mine installation and neutralization, and many military applications. The objective of this research is designing a control algorithm for underwater vehicles such that an under actuated vehicle can reckon a moving target as a reference and whilst chasing it, vehicle can keep a fixed distance from this target. First the dynamics of underwater vehicles are modeled and in this modeling different effects due to under water motion such as drag force, buoyancy force, and also added mass are included... 

Asphaltene are the heaviest components if some crude oil which are in thermodynamic equilibrium. Any change in the equilibrium condition including change in temperature, pressure or composition may render asphaltene to come out of solution and precipitate. Asphaltene precipitation and deposition is one of the main problems in some of the oil fields. Precipitated asphaltene may deposit in the reservoir, near wellbore, wellstring, transport pipeline and surface facilities. In porous media, the deposited asphaltene over the surface and/or across pore throat can severely reduce the effective permeability and results in decreasing of the oil production. Also, the deposited asphaltene results in... 

The main objective of this project is to study the effect of the presence of nanoparticles on mass transfer in liquid-liquid systems. To do this research, TiO2/water, Al2O3/water, CNTs/water and CNTs/toluene have been used as nanofluids. The experiments of TiO2/water nanofluid were been carried out in water-acetone-toluene system at two weigh percents of TiO2 nanoparticles. The result showed that mass transfer decreased in 0.5wt% of TiO2, compared to base fluid, and it increase in 1 %wt. Also in 0.5%wt the decrease in interfacial tension decreased diameter of drops and as a result mass transfer decreased too. In 1%wt the increase in viscosity increased the diameter of drops and then the... 

Communication Buoys are devices that facilitate radio communication between underwater ships and surface stations. In this research such device is thoroughly designed for a submersible application. The system comprises of buoy, connection cable, buoy cavity, cable passage, winch and other supporting and safety subsystems. Buoy and cable system was analyzed in a general form and their stable states were determined for different ship maneuvers, sea streams, and wave conditions. Based on this, optimum buoy geometry and cable length were found for the defined application and other subsystems were detail designed. To evaluate the design, some of the system components were manufactured and... 

In this work, we use computational fluid dynamic simulation tools for investigation two dimensional of eel movement. Firstly, the numerical study of smooth particle hydrodynamics was applied for determination drag coefficient and lift coefficient of undulation movement eel body. The initial mesh was manual. So, the effective parameters of eel movement were investigated. The smooth particle hydrodynamic method was not use, because of saving on time. Therefore, fluent software was used. UDF were added to the fluent software, which it can be move the boundary layer of mesh with eel movement. The dynamic mesh tools of fluent software were used. Initial shape had a curvature and utilized for... 

This paper was directed to recognize maneuver equations perfectly, and with regard to CFD method maneuver simulation is going to be done in form of two and three dimensional. Today, since CFD methods have been exerted in different works, further and more actual development of floating body's maneuver is going to be our special need. As numerical methods for floating body's maneuver simulation by RANS method are developing, more researches are being done about this field as well. This thesis is going to simulate primitively maneuver of one floating body by Smoothed Particle Hydrodynamic(SPH) method in order to be as the beginning of maneuver simulation by this method in which with regard to... 

Underwater robots have found various applications such as military ones, environmental monitoring, oil pipe exploration and surgeries. Design of highly maneuverable robot fish is mostly based on their propulsion mechanism, anatomy of the base fish, highly controllable fins and high propulsion efficiency.
In this research, we design a robot fish by using of experimental results on fish hydrodynamics, flow pattern around the model and various mechanisms of the fish.
In the experimental section, we arranged advanced image processing and optical measurement of DPIV setup in order to reviewing and analyzing movements of two species of fish (trout and Pangasius). The swimming speed of... 

Magnetite (Fe3O4) nanoparticles were synthesized and coated with Oleic Acid using the co-precipitation method. The particles were characterized using DLS, FT-IR, SEM, XRD, VSM and UV-Vis spectrophotometry analysis. The mean size of particles was 28.8 nm and the FT-IR analysis indicated that Oleic Acid was coated suitably on the nanoparticles. The vsm test indicated no hysteresis loop for the particles, defining the superparamagnetism of them. A nanofluid containing nanoparticles in 5wt% Acetic Acid in Toluene as the base fliud was prepared. The stability of this nanofluid was determined using UV-Vis spectrophotometry to be less more then 95% in the first two hours. This nanofluid is used as... 

In this project, for hydrodynamic simulation of RIPI experimental bubble column with concerning chemical reaction, first only hydrodynamic simulation and then hydrodynamic with reaction was done. For complete knowledge about bubble columns hydrodynamic, all common flow regimes were studied. First of all a rectangular semi-batch bubble column with bubbly flow regime and gas flow of 0.26 m3/h was simulated with commercial CFD software, FLUENT v. 14.5. Euler-Euler approach in 2D and 3D was used and because of bubbly flow regime a mean constant diameter was assumed for dispersed gas phase. Effect of interfacial forces (e. g drag, lift and virtual mass) was studied and compared with experimental... 

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... 

This work is related to the research in the fields of particulate flow with the presence of external magnetic field and simulating movements of particles till making chain of particles. Using direct numerical simulation method for a two-way coupling of fluid and magnetic governing equations makes a more roboust and precise method. Also, using some assumptions simplified general maxwell equations to set of magnetostatic equations. these eqautions are solved by the boundary element method and the integral equations. Using analytic integrals and calculation of magnetic intensity are some techniques suggested for improving the preciesion of the presented work. the magnetic force and torques can... 

This research studies a 3D channeled myocardium scaffold with computational fluid dynamics. It proposes a mathematical model to evaluate the impact of oxygen carriers and scaffold geometry on cell growth in a 3D cardiac construct. The modeling results show that using 5.4% perfluorocarbon oxygen carrier (PFC) has increased cardiac cells density 15% of the initial seeded cells comparing to pure culture medium without PFC supplementation. Effects of the scaffold geometry on cell density in the construct were examined by increasing channel numbers and changing the construct length. The results show that increasing channel numbers (by 50% decreasing channels diameter and wall to wall spacing) the... 

Underwater robots are broadly used in oceanography to explore ocean environments,inside inspection of pipes, and also to provide security at maritime boundaries. To design an underwater autonomous robot, it is compulsive to take advantage of a high efficient propulsion mechanism to lengthen the tour time span. Since fish-like propulsion mechanisms have presented higher efficiency comparing other mechanisms, they have been paid a lot of attention.In the present research, the hydrodynamic of a thunniform fish robot is analyzed under some reasonable simplifications. Based on the results achieved from this study, closed expressions are developed to predict the steady mean velocity and the... 

Design optimization of ships by taking maneuverability in account has great influence on the performance of the vessels. Thus providing a method to predict the behavior of vessel in the design process is very important. Ship maneuverability is remarkable from different aspects of view. Especially in high speed vessels of various applications and missions’ good maneuverability would be a positive rating for it. For example, military vessels in specific situations need to change the speed and direction and this is a crucial capability of them. Also in accordance to the rules of IMO all of the vessels should perform maneuvering trials and fulfil the minimum requirements. Accordingly, this issue... 

Numerous experimental and modeling efforts have been paid done to investigate the behavior of gas-solid fluidized beds. Existence of a velocity gradient in the axial direction in tapered fluidized beds causes unique dynamic characteristics of this type of beds relative to cylindrical fluidized beds. Because of these characteristics, fluidized beds with inclined walls have found wide applications in industrial processes. Gas bubbles play an important role in the hydrodynamics of bubbling gas-solid fluidized beds; so, fundamental understanding of the bubbling behavior of fluidized beds is required to describe bubble-related phenomena such as solids mixing, segregation, reaction conversion,... 

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... 

Nowadays, underwater vehicles designed by getting inspiration from aquatic animals’ motions have considerable merits; therefore, the issue of designing and building such vehicles has great significance. One of the aquatic animals, which can be a source of inspiration for designing vehicles with optimized propulsion and maneuver ability, is turtle. In order to design a robot under the inspiration of turtle locomotion, at first, it requires analyzing its locomotion carefully. In this project, it has been tried to do so. Having examined the motions of turtles and other aquatic animals thoroughly, the basics of their motions are achieved. Next, the locomotion of both sea and pond turtle are... 

One of the most important noise produced by craft, is the propeller noise which must be identified and measured for many reasons, including military and engineering applications. Therefore, in the first step, the sources of noise emissions in the propeller are studied, and after describing the research background, the governing equations of this research are examined. Then, to validate, the DTMB 4119 propeller, which has hydrodynamic and hydroacoustic results, is used. In order to carry out the investigations, a B series propeller model is selected and compared with changing the parameters of the Rake, Skew, Pitch ratio and the number of blades for their hydrodynamic and hydroacoustic... 

One main problem in many numerical simulations is the lack of sufficient infrastructure data to precisely model and analyze the flow through complex geometries. Since experimental procedures are generally very expensive; and sometimes impossible, it becomes necessary to find alternative ways such as numerical approaches to predict the flow behavior through complex geometries. The heat exchangers can be categorized as geometries with complex configuration and apparently expensive to solve numerically. They are widely used in different industries including the aerospace. The restrictions in design and implementation of aviation’s heat exchangers have promoted the related companies to converge... 

Improving the performance of modular, low-cost autonomous underwater vehicles (AUVs) in such applications as long-range oceanographic survey, autonomous docking, and shallow-water mine countermeasures requires improving the vehicles’ maneuvering precision and battery life. These goals can be achieved through the improvement of the vehicle control system. A vehicle dynamics model based on a combination of theory and empirical data would provide an efficient platform for vehicle control system development, and an alternative to the typical trial-and-error method of vehicle control system field tuning. As there exists no standard procedure for vehicle modeling in industry, the simulation of...