Sharif Digital Repository

Dynamic compaction is a widely used soil improvement method in dry and/or saturated soils. Despite its vast application, its design basis is still empirical and the mechanisms that are involved in the procedure are not fully understood. A fully coupled dynamic finite element code has been developed in order to clarify the ambiguities in the process and predict the strain/displacement field in the ground, determine depth and degree of improvement, and also calculate the pore pressure variation during the process. This model can be used as a rational design tool for dynamic compaction projects  

The hydraulic performances of drain pipes are very important in drainage projects and systems. Usually these pipes are used in a saturated soil to decrease the water table to a favorable level or, drain the excess water. However, drain pipes can be used in a water or wastewater tank for different purposes such as selective withdrawal. There are not much published documents on the performance of drain pipes in submerged situations. Therefore, the aim of this study was to examine the performance of drain pipe in a submerged tank. For this, a horizontal pipe of 26.5 mm inner diameter, 5 meter long with 48 circular drain inlets of 10 mm diameter at equal distances along the pipe have been tested... 

An analytical/numerical model based on the assumption of rigid incompressible water column and compressible air bubble, is derived to simulate the pressure fluctuations, void fraction, air/water flow rate, water velocity in a closed conduit and water depth at upper reservoir due to formation of unstable slug flow. It is a comprehensive model which can generate different hydraulic situations of instability in a closed conduit based on hydraulic approach. The boundary conditions are the system of algebraic or/and simple differential equations. The steady solution of the governing differential equations is generally performed as the initial data. The frequency of pressure fluctuation and... 

An experimental investigation has been carried out to verify characteristics of pressure fluctuations inside a circular, horizontal and inclined pipeline (90mm inside diameter and 10 m long) carrying two-phase air-water flow in a controlled manner (operating at room temperature and normal pressure). The pressure fluctuation was considered to be due to interaction between the fluid and air bubble compressibility in the pipe. The fluctuating pressure was studied in detail while the flow pattern was mainly slug, wavy or stratified flow. The tests were carried out varying with time, space, water flow rate/air flow rate ratio and pipe inclination. The pressure fluctuations were measured... 

Thermopneumatic micropump is one type of positive displacement micropump, which has many applications due to its relatively large stroke volume, low working voltage, and simple fabrication in microscale. In this paper, a numerical study of heat transfer and fluid flow in a valveless thermopneumatically driven micropump is presented. For rectifying the bidirectional flow, a nozzle and a diffuser are used as the inlet and outlet channels of the chamber. Since the fluid flow is induced by the motion of a diaphragm, the numerical simulation includes fluid structure interaction, which requires applying a dynamic mesh. The domain of solution is divided into two sections; the actuator unit, which... 

There is currently a significant focus on using boundary layer control (BLC) approach for controlling the flow around bodies, especially the foil sections. In marine engineering this is done with the hope of increasing the lift - to - drag ratio and efficiency of the hydrofoils. In this paper, effects of the method on hydrodynamic characteristics and tip vortex formation of a hydrofoil are studied. Steady water injection at the tip of the hydrofoil is simulated in different conditions by using ANSYS-CFX commercial software. Validity of the proposed simulations is verified by comparing the obtained results against available experimental data. Effects of the injection on the lift, drag, and... 

The soil permeability coefficient plays a key role in the process of numerical simulation of the liquefaction phenomenon. Liquefaction causes a considerable increase in soil permeability, due to the creation of easier paths for water flow. The work presented in this paper tries to investigate the effects of permeability coefficient on the results of numerical modeling of the liquefaction phenomenon. To do this, a fully coupled (u-P) formulation is employed to analyze soil displacements and pore water pressures. Two different versions of a well-calibrated critical state bounding surface plasticity model, which possesses the capability to utilize a single set of material parameters for a wide...