International Shipbuilding Progress - Volume 21, issue 242

Authors: Haddara, M.R.

Article Type: Research Article

Abstract: An analytical method for the study of transient behaviour as well as the stationary solution of nonlinear ship motion in random waves is presented. The problem of rolling motion of a ship travelling in oblique random waves is considered for the purpose of illustrating the method. The presence of nonlinear damping and restoration terms of general form is allowed. Differential equations which govern the propagation of the expected value and the variance of the motion in this case are derived, using the Fokker-Plank equation. The results are specialized to the case of a ship rolling in beam waves. Results …are compared with similar results obtained by other methods. This method gives the exact stationary solution when the damping is linear. Show more

DOI: 10.3233/ISP-1974-2124201

Citation: International Shipbuilding Progress, vol. 21, no. 242, pp. 283-288, 1974

Authors: Donohue, G.L. | Hoyt, J.W.

Article Type: Research Article

Abstract: Problem: Develop data to ascertain the magnitude of the sewage pollution problem arising from Navy ships anchored in or moving through a harbor, with particular reference to amphibious training exercises in which large numbers of personnel may be brought to nearshore areas for relatively short times. Results: A number of releases of dyed sewage were made in Wilson Cove Harbor of San Clemente Island at rates corresponding to those at which sewage would be discharged by amphibious task forces of from 500 to 10,000 men. The movement of the sewage was traced by photography, bacterial counts, dye, and …BOD measurements in the surrounding water and on the shoreline. The results show that the diffusion (rate of spreading) of the sewage was much lower than that predicted from open-ocean data, and hence Navy ships can stay in a small harbor, such as Wilson Cove, much longer than originally anticipated without danger of sewage contamination of the shoreline. An operational-guidance chart was constructed indicating those times and minimum distances for a given manning level of a task force that would prevent contamination of the shore. Show more

DOI: 10.3233/ISP-1974-2124202

Citation: International Shipbuilding Progress, vol. 21, no. 242, pp. 289-299, 1974

Authors: Lee, Chuan

Article Type: Research Article

Abstract: The distribution of singularities (i.e. source, sink and dipole) representing a ship’s hull has played an important role on studying the wave resistance in naval hydrodynamics. Based on the theoretical wave resistance formula from linearized free surface theory, six different wave resistance expressions in terms of three wave components along a longitudinal cut parallel to the ship’s course are presented. To demonstrate the numerical accuracy of these wave resistance expressions, the analysis has been applied to the theoretical wave profiles generated by a submerged point dipole and the results are compared to the known theoretical value.

DOI: 10.3233/ISP-1974-2124203

Citation: International Shipbuilding Progress, vol. 21, no. 242, pp. 300-308, 1974