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H.J. de Koning Gans
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1
Flexible models have been used extensively in the literature to emulate hydroelastic behavior at model scale. Such models mainly depict ships, with fewer examples representing other platforms, such as wind turbines. For both ships and wind turbines, the most common method to emulate the structure is to produce a model in rigid segments and introduce a stiffness source by linking them with a flexible backbone. This approximation can often be sufficient for both types of structures, as their behavior in bending is beam-like. However, for floating platforms with a more 3-dimensional structure, the design of the model becomes significantly more complex. For instance, floating trusses are one of the suggested solutions for floating platforms of the future, but current studies are restricted to their bottom-fixed versions. In this study, the hydroelastic responses of a floating truss structure will be emulated. The platform has a triangular shape, with the truss system linking three cylindrical floaters at the points. A simplified model to emulate several of the mode shapes of the full-scale platform is designed, and produced using additive manufacturing. The instrumentation and calibration processes are described, and verification of the physical model against simulated responses is presented.
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Flexible models have been used extensively in the literature to emulate hydroelastic behavior at model scale. Such models mainly depict ships, with fewer examples representing other platforms, such as wind turbines. For both ships and wind turbines, the most common method to emulate the structure is to produce a model in rigid segments and introduce a stiffness source by linking them with a flexible backbone. This approximation can often be sufficient for both types of structures, as their behavior in bending is beam-like. However, for floating platforms with a more 3-dimensional structure, the design of the model becomes significantly more complex. For instance, floating trusses are one of the suggested solutions for floating platforms of the future, but current studies are restricted to their bottom-fixed versions. In this study, the hydroelastic responses of a floating truss structure will be emulated. The platform has a triangular shape, with the truss system linking three cylindrical floaters at the points. A simplified model to emulate several of the mode shapes of the full-scale platform is designed, and produced using additive manufacturing. The instrumentation and calibration processes are described, and verification of the physical model against simulated responses is presented.
Ships sailing in ice require a propeller that is able to endure both extreme loads and fatigue loads and operate efficiently in ice and open water. Knowledge and descriptions of the physical processes of propeller-ice interaction are essential to model the interaction with its dominant parameters and finally predict the loads. The research described in this paper uses an experimental setup to determine if the crushing strength of ice, or in general a solid, is a dominant parameter in propeller-ice interaction as stated in empirical and theoretical models. Warm model ice, a paraffin based material to be used at room temperature, with ex-situ tested crushing strength, density and elasticity, is supplied to an in-situ model propeller at different rpms. One blade of the propeller is equipped with a six-component load sensor. Impacts are recorded in the time domain and synchronised with high speed footage. The data is analysed to understand and explain the impact behaviour by comparing it with rotational speed, load and footage. Scaling of the warm model ice properties is discussed as well due to density differences between warm model ice and sea ice.
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Ships sailing in ice require a propeller that is able to endure both extreme loads and fatigue loads and operate efficiently in ice and open water. Knowledge and descriptions of the physical processes of propeller-ice interaction are essential to model the interaction with its dominant parameters and finally predict the loads. The research described in this paper uses an experimental setup to determine if the crushing strength of ice, or in general a solid, is a dominant parameter in propeller-ice interaction as stated in empirical and theoretical models. Warm model ice, a paraffin based material to be used at room temperature, with ex-situ tested crushing strength, density and elasticity, is supplied to an in-situ model propeller at different rpms. One blade of the propeller is equipped with a six-component load sensor. Impacts are recorded in the time domain and synchronised with high speed footage. The data is analysed to understand and explain the impact behaviour by comparing it with rotational speed, load and footage. Scaling of the warm model ice properties is discussed as well due to density differences between warm model ice and sea ice.
To predict loads on propellers in ice, model tests can be used. Using regular (refrigerated) cold model ice in ice basins is a valid option. However, these tests are expensive, difficult to reproduce and bound to time and location, due to the required cooling in ice model basins. An alternative would be to use warm model ice, a material with the properties of model ice at room temperature. This paper proposes one variety, using only materials available from DIY stores. Based on theoretical propeller-ice interaction models, it is assumed that the loads come from a crushing process. Hence, the compressive strength follows as dominant material property of ice. To match compressive strength of weak cold model ice, a large particle composite is proposed. Expanded Polystyrene (EPS) beads are used as particles, with paraffin as matrix to produce warm ice specimens. The compressive strength of these specimens were measured with a uniaxial compression test and matched with weak model ice. The specimens were designed for in-situ use in model scale propeller impact tests.
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To predict loads on propellers in ice, model tests can be used. Using regular (refrigerated) cold model ice in ice basins is a valid option. However, these tests are expensive, difficult to reproduce and bound to time and location, due to the required cooling in ice model basins. An alternative would be to use warm model ice, a material with the properties of model ice at room temperature. This paper proposes one variety, using only materials available from DIY stores. Based on theoretical propeller-ice interaction models, it is assumed that the loads come from a crushing process. Hence, the compressive strength follows as dominant material property of ice. To match compressive strength of weak cold model ice, a large particle composite is proposed. Expanded Polystyrene (EPS) beads are used as particles, with paraffin as matrix to produce warm ice specimens. The compressive strength of these specimens were measured with a uniaxial compression test and matched with weak model ice. The specimens were designed for in-situ use in model scale propeller impact tests.