Design of a ship model for hydro-elastic experiments in waves
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초록
Large size ships have a very flexible construction resulting in low resonance frequencies of the structuraleigen-modes. This feature increases the dynamic response of the structure on short period waves (springing) and onimpulsive wave loads (whipping). This dynamic response in its turn increases both the fatigue damage and the ultimateload on the structure; these aspects illustrate the importance of including the dynamic response into the design loadsfor these ship types. Experiments have been carried out using a segmented scaled model of a container ship in aSeakeeping Basin. This paper describes the development of the model for these experiments; the choice was made todivide the hull into six rigid segments connected with a flexible beam. In order to model the typical feature of the openstructure of the containership that the shear center is well below the keel line of the vessel, the beam was built into themodel as low as possible. The model was instrumented with accelerometers and rotation rate gyroscopes on eachsegment, relative wave height meters and pressure gauges in the bow area. The beam was instrumented with straingauges to measure the internal loads at the position of each of the cuts. Experiments have been carried out in regularwaves at different amplitudes for the same wave period and in long crested irregular waves for a matrix of wave heightsand periods. The results of the experiments are compared to results of calculations with a linear model based onpotential flow theory that includes the effects of the flexural modes. Some of the tests were repeated with additionallinks between the segments to increase the model rigidity by several orders of magnitude, in order to compare the loadsbetween a rigid and a flexible model.
Abstract
Large size ships have a very flexible construction resulting in low resonance frequencies of the structuraleigen-modes. This feature increases the dynamic response of the structure on short period waves (springing) and onimpulsive wave loads (whipping). This dynamic response in its turn increases both the fatigue damage and the ultimateload on the structure; these aspects illustrate the importance of including the dynamic response into the design loadsfor these ship types. Experiments have been carried out using a segmented scaled model of a container ship in aSeakeeping Basin. This paper describes the development of the model for these experiments; the choice was made todivide the hull into six rigid segments connected with a flexible beam. In order to model the typical feature of the openstructure of the containership that the shear center is well below the keel line of the vessel, the beam was built into themodel as low as possible. The model was instrumented with accelerometers and rotation rate gyroscopes on eachsegment, relative wave height meters and pressure gauges in the bow area. The beam was instrumented with straingauges to measure the internal loads at the position of each of the cuts. Experiments have been carried out in regularwaves at different amplitudes for the same wave period and in long crested irregular waves for a matrix of wave heightsand periods. The results of the experiments are compared to results of calculations with a linear model based onpotential flow theory that includes the effects of the flexural modes. Some of the tests were repeated with additionallinks between the segments to increase the model rigidity by several orders of magnitude, in order to compare the loadsbetween a rigid and a flexible model.
참고문헌 (19)
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