Sharif Digital Repository

Mesoscopic hydrodynamic equations are solved employing a VOF based method to investigate the equilibrium shape of nanodroplets positioned over various topographic geometries of the supporting substrate for three-dimensional systems. By taking into account liquid-liquid and liquid-solid interactions a complex distribution for inter-molecular forces over the substrates (the disjoining pressure) is observed. In this research we show that motion of nanodroplets not only caused by contact angle difference in drplets two sides, but also depend on disjoining pressure parameters.Geometries with increasing complexities, from wedges to three dimensional edges and wedges, were explored with the main... 

Due to recent advances in laser technology and instruments, laser assisted machining processes has gained extra attention by scientists and industries. Naturally, effective modeling of the process is of great interest for researchers. Machining processes are generally modeled via FE tools and based on the requirements of model, it can be performed either mechanically or thermos-mechanically. About the LAM problems, it is basically meaningless to have a model without considering thermal effects. Hence, modeling is performed in two steps where through the first one, a thermal problem is solved to bring the temperature distribution of the work piece as the initial conditions of the next step.... 

Physicians use charts that are prepared by experiments on animals or humans to prescribe drug dosage for patients. This method requires much more time by the Ministry of Health to approve new drugs to be used in health-care centers. Furthermore،we have no sight on how a specific drug is going to be diffuse in our body. In order to predict the distribution of a drug or any minerals in the kidney we need to model it. The first step would be modeling the important species that influence the urine concentrating mechanism. Due to the complications in modeling that mechanism especially in the inner medulla zone، we hadn’t solid information regarding that area. It is about half a century that... 

The purposes of this research are one and three dimensional aerodynamic designs of a twin entry radial-inflow gas turbine's impeller. The GT4082 model Garrett turbocharger was chosen for this purpose. In order to predict existing turbine performance curves one dimensional model was prepared for whole turbine. For validating the 1d-modeling's results, widespread tests were performed on the turbine at Sharif University of Technology turbocharger lab. Comparing the results of 1d-modeling with experimental results, show 4.7% and 4% max difference for efficiency and mass parameter respectively. The wheel designing procedure started from primary design based on the mean line assumption, in 1-d... 

The objective of current research is to investigate the effects of Twin Swirler Injector on performance of turbine combustor. For this purpose, the swirlcup is assessed in a dump combustion chamber. The resultant simplicity in geometry leads to a facilitation in parametric studies as well as a reduction in modeling and meshing time. The target swirlcup, is a simplified model of CFM56 engine’s swirlcup.
Standard k-ε model is established to take into account turbulence effects. The non-reacting flow is at first simulated for capturing and recognising different phenomena. Adiabatic reacting flow simulations are conducted with Probability Distribution Function using Steady Laminar Flamelet... 

There are numerous ways available to achieve low temperatures that cryocoolers might be among the most important of them. In the meantime, the pulse tube refrigerator has a special place due to its simple geometry and not be using any moving parts. This simple property make the pulse tube refrigerator one of the most popular methods to achieve low temperatures. Nowadays, a pulse tube refrigerator is used for cooling in the range of 4 to 123 Kelvin in two form of one-stage and two-stage and up to an approximate power of 1 KW. Today, due to the temperature and the amount of power required for cooling, as well as the time it takes to reach that temperature, this chiller is used in medical,... 

The aim of the present research is to investigate the combustion chamber cooling with vortex method in presence of kerosene and liquid oxygen as propellants. For this purpose, a part of oxidizer is entered into the cylindrical combustion chamber tangentially (from bottem of the chamber), and creates a vortex flow (outer vortex). With motion of created outer vortex along the wall and eventually hit its top wall (the head of the chamber), secondary vortex (inner vortex) occurs along the center line, with a downward direction (opposite to the primary vortex). The fuel and other part of the oxidizer injection is also carried in the head of chamber, so by mixing the fuel and oxidizer that happens... 

The prediction of deposition efficiency of submicron particles in the pulmonary alveoli has received special attention due to its importance for drug delivery systems, and for assessing air pollutants health risks. In this work, the pulmonary alveoli of a healthy human are idealized by a three dimensional honeycomb like configuration and a fluid-structure interaction analysis is performed to study the normal cyclic breathing hydrodynamics. A viscoelastic model is used for the mechanical behavior of alveolar wall tissue. In contrast to previous works in which the inlet flow rate is predefined, in this model a negative pressure is imposed on the outside surface of the alveolus which causes air... 

In this work, simulation of 3D three-phase naturally fractured reservoirs is studied. Both Dual Porosity and Dual Porosity-Dual Permeability models which are commonly used in commercial softwares such as ECLIPSE and CMG, are utilized. The governing equations include the mass (in Black-oil model) and linear momentum (in Darcy law form) equations, which are converted into pressure equations and a set of transport equations for the saturations and mole fractions of phases. These equations are solved once for the matrix domain and subsequently for the fracture domain. These two set of equations are coupled through transfer functions. The accuracy of computations significantly depends on how... 

With the process of achieving a higher state of social development and technological advances, the need for higher and more strict safety standards has been increased. In this regard, it is of great importance to have an accurate understanding of the fire phenomena and its consequences. Among the adverse effects of fire, a significant percentage of the fire fatalities is related to the fire-induced buoyant gases (smoke) flow which can lead to suffocation. Therefore, it is necessary to know the physics of the fire phenomena well. In fire investigation methods, the numerical study is an appropriate choice, because of the lower executive cost (relative to the experimental study) and the wider... 

Researchers working at Mowafaghian Rehabilitation Research Center have decided to develop a telerehabilitation system named SEPANTA, especially designed for activity recognition of Parkinson's Disease patients. In this regard, the system uses 34 mobility exercises, including 20 LSVT-BIG activities (especially designed for PD patients) and 14 functional daily activities. Human Activity Recognition (HAR) systems faces various challenges e.g., intra-class variabilities, meaning differences in an activity performance by different persons or a person. Data augmentation and utilizing deep learning models are the most common solutions for the risen challenges. However, deep structures require an... 

The urine formation and excretion system has long been of interest for mathematicians and physiologists to elucidate the obscurities within the process happen in renal tissue. In this study, a novel and absolutely three-dimensional approach is utilized for modeling urine concentrating mechanism in rat renal outer medulla which is essentially focused on demonstrating the significance of tubule's architecture revealed in anatomic studies and physiological literature. Since nephrons and vasculatures work interdependently through a highly structured arrangement in outer medulla which is dominated by vascular bundles, a highly detailed functional unit is proposed and also it is strongly justified...