1,721,072 research outputs found
Ship resistance and propulsion: practical estimation of ship propulsive power
No full textShip Resistance and Propulsion is dedicated to providing a comprehensive and modern scientific approach to evaluating ship resistance and propulsion. This book, written by experts in the field, includes the latest developments from applied research, including those in experimental and CFD techniques, and provides guidance for the practical estimation of ship propulsive power for a range of ship types. A large number of fully worked examples are included to illustrate applications of the data and powering methodologies; these include cargo and container ships, tankers and bulk carriers, ferries, warships, patrol craft, work boats, planing craft and yachts. The book is aimed at a broad readership including practising naval architects and marine engineers, seagoing officers, small craft designers, undergraduate and postgraduate degree students. It should also appeal to others involved in transportation, transport efficiency and eco-logistics who need to carry out reliable estimates of ship power requirements.Contents1. Introduction; 2. Propulsive power; 3. Components of ship resistance; 4. Model-ship extrapolation; 5. Model-ship correlation; 6. Restricted water depth and breadth; 7. Measurements of resistance components; 8. Wake and thrust deduction; 9. Numerical estimation of ship resistance; 10. Resistance design data; 11. Propulsor types; 12. Propeller characteristics; 13. Powering process; 14. Hull from design; 15. Numerical methods for propeller analysis; 16. Propulsor design data; 17. Applications.<br/
Development and use of a velocity prediction program to compare the effects of changes to foil arrangement on a hydro-foiling Moth dinghy
No full textThe International Moth dinghy is a 3.355m long single handed, una-rigged monohull dinghy. The class rules allow the use of hydrofoil that in certain wind conditions can significantly reduce resistance. A new velocity prediction program (VPP) has been developed to evaluate the impact of hydrofoil design and set-up on the performance of a Moth dinghy by simulating racing on a windward - leeward course. The VPP generates polar diagrams indicating the speed of the craft in a range of true wind strengths and angles. Sail force and windage are modelled using aerofoil theory. The drag model includes hull skin friction and residuary resistance, profile and induced drag for every foil, wavemaking drag of the lifting foils and spray drag of the surface piercing foils. Using an iterative process the VPP determines the boat speed that balances resistive forces with drive force, heeling moment and righting moment and vertical lift forces with weight. A series of case studies demonstrate the use of the VPP by examining the effects of changing the span of the forward foil, adding end plates, and using different foil geometries on performance.</p
Transition from vortex to wall driven turbulence production in the Taylor-Couette system with a rotating inner cylinder
No full textAxisymmetrically stable turbulent Taylor vortices between two concentric cylinders are studied with respect to the transition from vortex to wall driven turbulent production. The outer cylinder is stationary and the inner cylinder rotates. A low Reynolds number turbulence model using the k- formulation, facilitates an analysis of the velocity gradients in the Taylor-Couette flow. For a fixed inner radius, three radius ratios 0.734, 0.941 and 0.985 are employed to identify the Reynolds number range at which this transition occurs. At relatively low Reynolds numbers, turbulent production is shown to be dominated by the outflowing boundary of the Taylor vortex. As the Reynolds number increases, shear driven turbulence (due to the rotating cylinder) becomes the dominating factor. For relatively small gaps turbulent flow is shown to occur at Taylor numbers lower than previously reported
Application of RANS to the hydrodynamics of bilge keels and baffles
No full textThis investigation first focuses on modelling the flow around cantilever plates in normal oscillation, providing key guidance for attaining sufficient accuracy for most engineering applications, in terms of turbulence modelling, mesh refinement and time step selection. The modelling approach is then applied to the hydrodynamics of a ship-like section fitted with vertical bilge keels, rolling at free surface. The results obtained from RANS are compared to available experimental data and predictions obtained from potential flow analysis. Viscous effects arising from the presence of the bilge keels are shown to influence more hydrodynamic coefficients than just roll fluid damping. Finally, empirical formulae commonly used to allow for the influence of viscous roll damping are compared to RANS predictions and experimental data.</p
Investigation of cavitation erosion-corrosion of duplex stainless steel and nickel aluminium bronze in 3.5% nacl solution
No full text- …
