Sharif Digital Repository

In the present paper, conceptual duct shape design for kinetic energy extraction with hydrokinetic turbines is discussed. The goal is to find a single-passage axisymmetric geometry that holds stable flow with maximum kinetic energy flux at duct throat. For finding the optimum duct shape, the fluid flow was numerically simulated in a wedge shaped space with Flow-Simulation Software. In a multi-stage conceptual design, tabulated configurations were employed to study each geometrical characteristic separately. These include curvature of profile camber, trailing edge shape, profile tip shape, and duct exit cross sectional area. The revolved profile of each duct consists of a well constrained... 

Mechanical properties and fracture toughness micromechanisms of copolypropylene filled with different amount of nanometric CaCO3 (5-15 wt %) were studied, J-integral fracture toughness was incorporated to measure the effect of incorporation of nanoparticle into PP matrix. Crack-tip damage zones and fracture surfaces were studied to investigate the effect of nanofiller content on fracture toughness micromechanisms. It was found that nanofiller acted as a nucleating agent and decreased the spherulite size of polypropylene significantly, J-integral fracture toughness (Jc) of nanocomposites was improved dramatically. The Jc value increased up to approximately two times that of pure PP at 5 wt %... 

The search for higher ship speeds and better propulsive performance has resulted in many performance enhancement techniques. One technique is to introduce an air film along the bottom of the hull to reduce skin friction drag. The air film system opens many possibilities for using designs with larger payloads such as barges and tankers, as well as catamarans with larger deck space which otherwise are not attractive because of their higher propulsion power. Although reducing hull drag by air injection was proposed in the beginning of this century, it still remains to be fully exploited. In this thesis, two models are used to do the experiments. The first one was a simple catamaran model and... 

The hydro-acoustic analysis of submerged propellers is an important issue in marine industries, which is examined to reduce the vibrations and noise level of vessels alongside reducing fuel consumption and improving hydrodynamic efficiency. B-series propellers are common propellers whose hydrodynamic and acoustic investigation through applying suitable rake, and skew angle can offer proper results to designers for enhancing the hydrodynamic performance and reducing noise. In this study, a model of the five-bladed B-series propeller with the normal skew angle is chosen. The effects of geometric parameters, including the rake angle, skew angle, geometric pitch ratio, and the number of blades...