Stopping manoeuvre of high speed vessels fitted with screw and waterjet propulsion

Concern about the increase in high-speed vessel traffic necessitates steps to bring out safety guidelines in order to regulate and improve their manoeuvrability. The stopping abilities of vessels ranging from medium speed containerships to high-speed vessels have been estimated. Assuming a straight contour track, the stopping distances have been checked against the known stopping criteria of IM

Textural evolution and phase transformation in titania membranes: Part 1. -unsupported membranes

Textural evolution in sol–gel derived nanostructured unsupported titania membranes has been studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermal gravimetry (TG), X-ray diffraction (XRD) and N2 adsorption. The anatase-to-rutile phase transformation kinetics were studied using the Avrami model. The precursor gel had a surface area of ca. 165 m2 g–1, which after heat treatment at 600 °C for 8 h reduced to zero. Undoped titania-gel layers transformed to more than 95% rutile after calcination at 600 °C for 8 h. The causes of surface-area reduction and pore growth were anatase crystallite growth and the enhanced sintering of rutile during transformation. Lanthanum oxide was identified as a suitable dopant for shifting the transformation temperature to ca. 850 °C. Lanthanum oxide doped titania showed an improved stability of porous texture compared to that of the undoped titania membranes

Prediction of load on mooring ropes of a container ship due to the forces induced by a passing bulk carrier

The hydrodynamic surge and sway forces and yaw moment on a moored ship induced by a anothership moving near and parallel to it are estimated. The results are compared with the values obtained byexperiments carried out in the Towing tank for manoeuvres in shallow water (co-operation Flanders Hydraulics -Ghent University) in Antwerp. Subsequently, equations of motion of the moored ship are solved to determine theloads on the mooring ropes. The effect of underwater form of the ships on the forces is also discussed

Synthesis and textural properties of unsupported and supported rutile (TiO2) membranes

Two approaches were postulated for improving the stability of porous texture of titania membranes: (1) retarding the phase transformation and grain growth; (2) avoiding the phase transformation. Based on the second approach, rutile membranes were made directly from a rutile sol, prepared by the precipitation of titania on SnO2 nuclei. The rutile membranes were stable up to 800 °C, with a porosity of ca. 40%, whereas normal titania membranes (starting with anatase) show very little porosity above 600 °C. Alumina substitution retards grain growth and pore growth at 850 °C for unsupported as well as supported membranes. \u

Experimental and Numerical Study of Motion Chracteristics of An Equi-Hull Trimaran

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Biological Propulsion Systems for Ships and Underwater Vehicles

Regulations and performance requirements related to technology development on all modes of transport vehicles for reduced pollution and environmental impact have become more stringent. Greening of transport system has been recognized as an important factor concerning global warming and climate change. Thus environment-friendly technical solutions offering a reduction of noxious exhaust gases are in demand. Aquatic animals have good swimming and maneuvering capabilities and these observations have motivated research on fish-like propulsion for marine vehicles. The fish fin movements, used by fish for their locomotion and positioning, are being replicated by researchers as flapping foils to mimic the biological system. Studies show that flapping foil propulsion systems are generally more efficient than a conventional screw propeller, which suffers efficiency losses due to wake. The flapping foil propulsors usually do not cavitate and have less wake velocity variation. These aspects result in the reduction of noise and vibration. The present study will cover an overview of aquatic propulsion systems, numerical simulations of flapping foils and ship model self-propulsion experiments performed using flapping foil system, particle image velocimetry (PIV), and digital fluoroscopy studies conducted on fish locomotion. Studies performed on underwater and surface vehicles fitted with flapping fins will also be presented

Textural evolution and phase transformation in titania membranes: Part 2. - Supported membranes

Nanostructural evolution and phase transformation in supported and unsupported titania membranes have been studied using Raman spectroscopy, X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). Densification of unsupported membranes started at ca. 450 °C and reached more than 97% density at 600 °C, whereas the supported membranes had a density of only ca. 70–75% even at 700 °C when calcined for 8 h. At 700 °C the average crystallite size of supported and unsupported membranes was ca. 20 and 70 nm, respectively. This behaviour is primarily attributed to the decrease in the driving force for sintering due to the stress developed during the constrained sintering of a film attached to a rigid support and to the inhibition of the reorganization process within the film, resulting in lower coordination numbers in supported membranes. Supported membranes showed a higher transformation temperature (slower rate of transformation) than did the unsupported. Supported and unsupported membranes, calcined for 8 h, transformed to ca. 90% rutile (calculated from Raman spectrum) after calcination at 850 and 650 °C, respectively. This difference in phase transformation behaviour is attributed primarily to the large stress which is developed in a constrained environment owing to the negative volume change during the anatase–rutile transformation

Horizontal Planar Motion Mechanism (HPMM) Incorporated to the existing towing carriage for Ship Manoeuvring Studies

Planar Motion Mechanism (PMM) equipment is a facility generally attached with Towing Tank to perform experimental studies with ship models to determine the manoeuvring characteristics of a ship. Ship model is oscillated at prescribed amplitude and frequency in different modes of operation while it is towed along the towing tank at predefined speed.The hydrodynamic forces and moments are recorded, analyzed and processed to get the hydrodynamic derivatives appearing in the manoeuvring equations of motion of a ship. This paper presents the details about the Horizontal Planar Motion Mechanism (HPMM) equipment which is designed, developed and installed in Towing Tank laboratory at IIT Madras