Sharif Digital Repository

In the present study, an incompressible smoothed particle hydrodynamics based on the artificial compressibility method is applied for simulating the incompressible turbulent flows. The Reynolds-averaged incompressible Navier–Stokes equations using the artificial compressibility method in the Eulerian reference frame are written in the Lagrangian reference frame to provide an appropriate incompressible SPH algorithm for the turbulent flow computations. Here, the k-L_m turbulence model, which is a simplified k-ϵ turbulence model, is used and formulated in the Lagrangian reference frame. The SPH formulation implemented here is based on an implicit dual-time stepping scheme to be capable of... 

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... 

Surface piercing propellers are particular type of supercavitating propellers that are commonly used for High-speed vessels. Most studies on this type of propellers has been investigating the hydrodynamic forces. But in recent years with increase in SPPs diameter used in vessels, structural analysis of this type of propellers is considered. For this purpose, studies on the stresses exerted on the propeller structures under load is done with the help of Hydro elastic methods. In this type of analysis, structura of propeller is intended to be flexible and Displacements under pressure checked and Tensions resulting from it are studied.
The present Thesis using ANSYS software to analyze a... 

This thesis is concerned with measurement and analysis of noise for an underwater propeller by means of numerical and experimental methods. A major cause of noise in buoyant bodies is the propeller. Detection and measurement of such noise is a part of various engineering and maritime applications. Thus detecting the sources of sound and ways of its propagation under water is the first step in many engineering and maritime applications of underwater acoustics which leads to noise reduction and control. Due to its wide subject, this thesis presents a phenomenology of propeller noise and discusses numerical and experimental methods. In the section that deals with numerical methods, the... 

The collective behavior of active matters, e.g. colony of micro swimmers and flocks of birds is modeled with self-propelled particles. It is evident that a continuum description of such systems is useful in determining the collective behavior in large scales. One can make continuum equations in active matter with the help of symmetry arguments. However, the equation is in a phenomenological level with undetermined transport coefficients. It is possible to construct the continuum equations from microscopic rules to find the transport coefficients in terms of microscopic parameters with approximations. One of the usual approximations called truncation method is to truncate the Fourier series... 

In this research, acoustic field around an underwater vessel generated by different sources is studied. Hull vibration due to harmonic forces from rotating machinery inside the vessel, flow induced noise due to flow around the hull, and propeller generated noise were considered. Finite Element Method (FEM) was used to determine hull vibration due to mechanical excitations by internal machinery. A 3-D boundary element computer code was then developed to solve Helmholtz equation in the surrounding water by which Acoustic field around the vessel was then obtained. To calculate flow induced noise and propeller noise, Navier-Stocks equations with LES turbulent model was solved around the vessel... 

In recent years, unmanned vehicles have intensively been developed to reduce human dangers for marine applications. Predicting the hydrodynamic coefficients of an autonomous underwater vehicle is important during the vehicle’s design phase. In other words to design an AUV, one must clarify its maneuverability and controllability based on a mathematical model. The mathematical model contains various hydrodynamic forces and moments expressed collectively in terms of hydrodynamic coefficients. Therefore, the correct values of the coefficients must be known to precisely design the controller of AUVs. SUT-2 is an AUV, being developed by Marine Engineering Laboratory of Sharif University of... 

Scientists want to know how they can control fluids motion. They use electric fields for controlling the fluids in different dimensions. In small size, application of electric fields is very important because of biological applications. We use electric current and field for rotating freely suspended films. Here, we study soap, polar and non-polar liquids, MBBA liquid crystal and ferrofluids films. We show that the surface charge plays the crucial role in rotating the films.We study the correlation between rotation of a film and different physical quantities.Our experiments confirm that dipole moments of fluid molecules do not show a clear effect on the rotation. Increasing the dipole moment... 

In this thesis, we propose and discuss efficient GPU implementation using CUDA for simulating electromagnetic scattering. We use SPH as a meshless particle method to electromagnetic transient simulation in time domain. Smoothed particle hydrodynamics (SPH) has been recently reformulated by the authors, and implemented in the so-called smoothed particle electromagnetics (SPEM) method. In SPEM two set of electric and magnetic staggered particles have to be generated. These particles are the points in which the field components are computed at each time step by using the information belonging to the neighboring ones.
On the other hand, CUDA™ is a general purpose parallel computing platform... 

The idea of using under water vehicles inspired by nature has gained considerable attention during the past few decades. This interest is due to the advantages of swimming and moving by this technique, in comparison with the conventional methods. Benefits are such as increasing speed, improved power, better manoeuvre ability,greater stability, optimal hydrodynamic performance ... etc. The purpose of this study was developing a model to simulate a stingray Manta Ray moving behaviour. Ansys- Fluent software was applied to solve the related equations of viscous laminar flow in 3-D form.Simulation of Manta Ray was performed with the flapping pectoral fin with dynamic mesh. Using this... 

Deformation and breakup of drops are the basisof many interfacial flow studies and appear in a number of industrial applications, e.g., spray painting, spray combustion, emulsion, foam, sedimentation, and rain. Following their formation, drops may enter a region where hydrodynamicforces are large enough to cause their significant deformation and breakup. When a drop breaks apart into a multitude of small fragments due to disruptive hydrodynamicforces, the process is termed secondary atomization or breakup. Due to many engineering and scientific applications of multiphase and multi-component flows, they have been the main topic of many researchers for many years. Particularly, interfacial... 

Dynamic positioning system is a controller system used to maintain the position and heading of a vessel with no use of anchors, jack ups but only using the propellers installed on the vessel. A vessel has six degrees of freedom, including three rotations and three transfer. In dynamic positioning systems, the vessel is controlled only on the horizontal plane such that its position and heading are controlled according to predetermined values. To achieve this, position and heading of the vessel is determined and the controller system computes the direction and required power of each propeller. Preliminary systems utilized PID controllers. As the control science has advanced, model based... 

Taghizadeh Manzari, M. (In this work, a modified Smoothed Particle Hydrodynamics (SPH) method, with a new moving solid boundary treatment approach, is utilized to simulate the particulateflow problems. The renormalized first and second derivative schemes which lead tothe consistency of the method, are also used along with a modification to the continuityequation which prevents the spurious pressure oscillations. The proposed methodis validated by solving benchmark problems of solid body motion in channel flows.There is a good agreement between the obtained results and those reported in theliterature. The convergence of solutions for different domain discretizations is alsoassessed. In order... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas an oil well stimulation is prevailing. Not only this method is environment friendly, but also it is economic. Although the application of this method is proved to be of outstanding positive influences in field operations, it suffers from lack of knowledge about the main governing mechanisms and also there are few mathematical models describing the process. In this study it is intended to investigate the role of ultrasonic waves on rate of recovery and the total recovery from porous media. A model is proposed which can predict the recovery at different times of operation. The results... 

In this study a new SPH model for solving free surface and fluid-fluid interaction problems is presented. The numerical model is capable of simulating two dimensional hydraulic problems with arbitrary boundary and initial conditions and large number of particles. It has the ability to model multi-fluids domain with different densities and viscosities. Several corrections are implemented in SPH formulation such as treatment of free surface and correction of viscous term in order to conserve the angular momentum. Several examples are conducted in fluid-fluid domains to measure the capability of model in this area of study. This new model use Incompressible SPH method for more accurate... 

One of the approaches to study the plasma phase of quantum chromodynamics is to investigate the motion of probes in the quark-gluon plasma. In the case of a moving heavy quark, the medium affects the quark by exerting a drag force on it. Since we finally detect hadron jets in detectors, the goal is to compute the darg force formula in a form compatible with the espectrum of final hadrons. On the other hand due to strong coupling, perturbative methods fail in the medium. So a nonperturbative method is needed. We use gauge gravity duality and compute the drag force exerted on a heavy quark in the hydrodynamic regime, up to first order in derivative expansion  

Smoothed particle hydrodynamics (SPH) is a meshfree method, based on Lagrangian formulation of Navier-Stokes equations, in which fluid is discretized to particles. This method is suitable and gives much better results for problems in which other methods have severe difficulties, (e.g., tracking of particles, moving boundaries, and problems with large deformations and, physical discontinuity). No need to follow a regular geometric structure in solution process and simple adaptation and coupling with methods such as finite element, are the positive characteristics of this numerical method. In this work, a systematic study of the processes, which are part of a membrane failure in a... 

High-Speed Crafts’ motion has lots of hydrodynamic complexities, so analytical study of their motion is not feasible. Meanwhile, experimental analysis of their reactions in water is not time-consuming & cost-effective. In spite of code generating & developing problems and complexities in the primary stage of numerical modeling of such problems, this method is the most popular & efficient one. On the other hand, flow around high-speed craft bodies has a turbulent nature and needs special cares to predict reasonable results. In the present study, after representing an introduction about the turbulence modeling, we discissed about governing equation such as momentum, volume fraction and rigid... 

Marine hotels are a new idea in marine industries all over the world. Also, it's not done any targeted and academic research on them in the country even in other countries up to now. For this reason in this project a conceptual design sequence is presented for marine hotels particularly floating hotels. At first, it's presented a complete introduction for modern marine structures such as floating hotels, under water tunnels, marine aquarium and restaurants. Also there is introduction to their working system, environmental conditions, their effeteness on environment and feasibility of their construction. In the following a simple cylindrical model of a floating hotel and its systems are... 

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...