Showing papers on "Metacentric height published in 1992"

Experimental investigation into the physics of roll damping of a long slender hull form

Abstract: The results of an extensive experimental program to study the roll damping characteristics of a warship model are reported. The simple free decay curves obtained for a towed as well as a self-propelled nine metre model, fitted with and without bilge keels, rudder and propellers, were analysed using an energy approach. A new nondimensionalisation scheme is used for the representation of the results and used to derive relationships relating the damping coefficient to the value of the metacentric height of the model. The nonlinearity of the damping with forward speed is explained.

Coupled Roll and Directional Stability Characteristics of Surface Ships

Abstract: : The problem of roll, sway and yaw motions of surface ships is considered. A mathematical model is developed which consists of the nonlinear maneuvering equations and incorporates cross coupling between sway force, yaw moment and the roll angle induced during a steady turn. The hydrodynamic derivatives and coefficients of a typical container ship were used as the base- line study model. The coupled system of nonlinear algebraic equations is formulated and solved to predict the steady state roll angle, sway velocity and turning rate as a function of the rudder angle and compared to the decoupled systems currently employed. A local perturbation is implemented in the vicinity of the above steady states to investigate dynamic stability of motion. Sensitivity analysis with respect to important design parameters such as speed loss during turing, approach speed, transverse metacentric height and trim is performed. Results demonstrate the significance of the coupling between roll, sway and yaw and the need to incorporate similar studies in the ship design and analysis process.

Lightweight four man rowing shell

Abstract: Four man rowing shells in heavyweight and lightweight configurations have an elongated hull with a bow and stern and a smoothly tapered hull surface therebetween. The hull surfaces have particular cross-sections below the waterline at stations spaced along the hull waterline. Other parameters for both heavyweight and lightweight hulls are provided such as waterline length, entry and exit angles, maximum beam, maximum draft, and metacentric height. In both configurations, the hull itself may be made of a laminate of a fiber composite skin over a core, such as a carbon fiber/honeycomb laminate, or of natural materials such as wood.

Oscillations of a body floating in an U-tube filled with a liquid

Abstract: A system analogous to a hydropower plant with a slender cylindrical body floating vertically in the surge shaft is studied. This is done in the context of a general study to see whether a throttled surge shaft can dampen oscillations. An U-tube is filled with a liquid. In one of its legs a body with big metacentric height is floating. If the system is perturbed two coupled oscillations occur. One of the natural frequencies is identical with the simple frequency of pitch oscillations of the body. The other one is proportional to the first one and also dependent on the ratio between the length of the body and the length of the water column.