Ships

Scale model tests are conducted of a Surface Effect Ship in a near-shore developing sea. A beach is built and installed in a wave tank, and a wavemaker is built and installed in the same wave tank. This arrangement is used to simulate developing sea conditions and a 1:30 scale model SES is used for a series of experiments. Pitch and heave measurements are used to investigate the seakeaping response of the vessel in developing seas. The air-cushion pressure and the vessel speed are varied, and the seakeeping results are compared as functions of these two parameters. The experiment results show a distinct correlation between the air-cushion pressure and the response amplitude of both pitch and heave. The results of these experiments are compared against results of a computer model of a Surface Effect Ship (SES).

In the present dissertation, the hydrodynamic and hydro-elastic characteristics of ship hull and plate vibrations are analyzed using theoretical and numerical methods. The wave forces are determined using a suite of methods which include the Froude-Krylov method for incident wave forces, Wagner's method and ABS rules for the slamming wave force, and numerical methods for nonlinear wave radiation forces. Finite difference methods are developed to determine the wave forced vibrations of ship hull plates which are modeled using a range of plate theories including nonlinear plate theory with and without material damping and orthotropic plate theory for stiffened hull plates. For small amplitude deformation of thin plates, a semi-theoretical superposition method is used to determine the free and forced vibrations. The transient ship hull vibration due to whipping is also analyzed using the finite difference method. Results, in the form of deformations and stress distributions, are obtained for a range of scantling and wave parameters to identify key parameters to consider in ship structural design.

This thesis analyses the behavior of an induction motor based on a mathematical model created for its simulation. The model describes the interaction of its several non linear differential equations to present a simulated output of induced torque and mechanical speed. Considering the applications to marine propulsion, it is also the goal of the project to design and test a control system for the speed of the motor by maintaining a specific cruse speed regardless the perturbations.

The use of surface piercing propellers (SPPs) shows promise for high speed operation by virtually eliminating appendage drag, which can be as much as 30 percent of the total drag on a vehicle at high speeds. The scarcity of available systematic test data has made reliable performance prediction difficult. The primary objective of this research is to obtain experimental performance prediction data that can be used in SPP design. In a series of open water tests in a non-pressurized towing tank facility, force transducer measurements were taken at tip immersion ratios from 0.5 to .33, yaw angles from 0° to 30° and inclination angles from 0° to 15° over a range of advance ratios from 0.8 to 1.8. Force transducer measurements were taken for thrust, torque, side forces and moments. These results will help develop a baseline for the verification of SPP performance prediction.

In the present study, 3 wake parameters are semi-automatically measured in 63 composite-labeled images of a surface piercing propeller tested at yaw angles 0-30 degrees, pitch angles 0-15 degrees, propeller immersion ratios of 0.33 and 0.50 and scaled advance ratios 0.656-1.927. A fourth wake parameter is measured in four composite labeled images of yaw angles 0-30 degrees, pitch angle 0 degrees, immersion ratios of 0.33 and 0.50 and scaled advance ratios 1.363-1.927. Measurements are plotted against propeller's angular position. Major findings include the behavior of wake parameters as the values of scaled advance ratio, yaw angle, pitch angle, and immersion ratio vary.