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# On a consistent linearized theory of the wave-making-resistance of ships : 16th Georg-Weinblum-Memorial-Lecture

Citation Link: https://doi.org/10.15480/882.968

Publikationstyp

Technical Report

Publikationsdatum

1993

Sprache

English

Author

On a consistent linearized theory of the wave-making-resistance of ships : 16th Georg-Weinblum-Memorial-Lecture

There are few discussions on the uniqueness in the theory of the wave-making resistance of ships. Moreover, a line integral term singularity distribution around a periphery of the water plane area, appearing in the theory casts a shadow on the uniqueness of the boundary value problem.

There is the only one well-known consistent theory, that is, two-dimentional theory of planing on the water surface in which a line integral term does not appear explicitly. In this theory, the sinkage and trim vary with speed and also the wetted length changes to fulfill Kutta's condition. However, in a usual ship, displacement ship, having a nearly vertical stem, the wetted length could not vary as in the planing ship. In the present paper, introducing a new singularity just before the bow, we try to obtain a consistent linearized theory for a displacement ship. We solve numerically the boundary value problem,investigating the properties of solutions and then calculate the sinkage and trim when a barge is running freely or is being towed without any external force or moment except a towing force.

Then, it is found that this free running becomes unstable over the speed Fr.=.61 regardless of the bottom shape. The resistance consists of three components, namely, the wave-making, the spray and the water head resistance. The former two components are well-known and the last one is a component introduced and named so here temporarily. This component resembles a wave-breaking resistance but we have no direct explanation.

There are few discussions on the uniqueness in the theory of the wave-making resistance of ships. Moreover, a line integral term singularity distribution around a periphery of the water plane area, appearing in the theory casts a shadow on the uniqueness of the boundary value problem.

There is the only one well-known consistent theory, that is, two-dimentional theory of planing on the water surface in which a line integral term does not appear explicitly. In this theory, the sinkage and trim vary with speed and also the wetted length changes to fulfill Kutta's condition. However, in a usual ship, displacement ship, having a nearly vertical stem, the wetted length could not vary as in the planing ship. In the present paper, introducing a new singularity just before the bow, we try to obtain a consistent linearized theory for a displacement ship. We solve numerically the boundary value problem,investigating the properties of solutions and then calculate the sinkage and trim when a barge is running freely or is being towed without any external force or moment except a towing force.

Then, it is found that this free running becomes unstable over the speed Fr.=.61 regardless of the bottom shape. The resistance consists of three components, namely, the wave-making, the spray and the water head resistance. The former two components are well-known and the last one is a component introduced and named so here temporarily. This component resembles a wave-breaking resistance but we have no direct explanation.

Schlagworte

boundary value problem

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Bericht_Nr.536_M.Bessho_On_a_Consistent_Linearized_Theory_of_the_Wave_making_Resistance_of_Ships_16th_Georg_Weinblum_Memorial_Lecture.pdf

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