Split Trailing Suction Hopper Dredgers (Split TSHD) have longitudinally-split hull, which symmetr... more Split Trailing Suction Hopper Dredgers (Split TSHD) have longitudinally-split hull, which symmetrically opens when executing gravity-driven unloading of the cargo, while being exposed to various environmental conditions. Even though they have variable hull geometry, their hydrostatic and stability characteristics are usually calculated for initial and unchanged loading conditions only, which is a requirement imposed by classification society stability regulations for TSHD ships [2, 3, 4]. In order to investigate the significance of the discharge process dynamics on actual ship stability, unsteady numerical simulations were performed with the Discrete Element Method (DEM) for symmetrical hopper opening during cargo discharge procedure, without the hull opening failure modes examined. The ship hydrostatic properties, which are pre-calculated analytically using Radial Basis Functions (RBF) for all possible states [11], are used in combination with the solver in order to compute the rig...
One of the main tasks of ship's computational geometry is calculation of basic integrals of s... more One of the main tasks of ship's computational geometry is calculation of basic integrals of ship's hydrostatics. In order to enable direct computation of those integrals it is necessary to describe geometry using analytical methods, like description using radial basis functions (RBF) with L1 norm. Moreover, using the composition of cubic and linear Polynomial radial basis functions, it is possible to give analytical solution of general global 2D description of ship geometry with discontinuities in the form of polynomials, thus enabling direct calculation of basic integrals of ship hydrostatics.
For the prediction of ship resistance in the preliminary stages of the ship design process, naval... more For the prediction of ship resistance in the preliminary stages of the ship design process, naval architects often use methods that are less complex and expensive than CFD simulations and experiments. Michell's thin ship theory can be used to quickly evaluate wave-making resistance, although, the original theory gives poor estimates for conventional hulls. In this work, techniques to improve the theory are introduced that account for viscous and non-linear effects. The improvements are validated by numerical simulation on three profoundly different hull forms: parabolic Wigley hull, Series 60, and a containership hull. Relatively better results were obtained compared to the original thin-ship theory and Holtrop-Mennen’s method. However, further study is necessary to improve the introduced formulations.
The Croatian, as well as European shipbuilding industry, cannot compete with Far East shipbuildin... more The Croatian, as well as European shipbuilding industry, cannot compete with Far East shipbuilding industries in a matter of low prices and short delivery time for production of conventional new ships. The way out from continuously decreasing production lies in orientation towards building more technically demanding and complex objects, and to merge, both, regionally and through production programs. The floating objects, as marine objects without self propulsion systems, equipped with own electrical energy sources, water supplies and waste water treatment systems, that provide object?s autonomy, would be one of very useful production solution, designed in cooperation with architects and curators for different purposes: restaurants, congress centers, cafe bars and disco clubs, apartments, car parking, etc. In the paper some ideas of using a floating objects in coastal cities is presented.
Modern high-speed ships demand application of materials that are light and with a good fatigue st... more Modern high-speed ships demand application of materials that are light and with a good fatigue strength and corrosion resistance. Various aluminum alloys can be technologically improved to match these demands. It is known that shot-peening method can be applied to improve fatigue properties of aluminum alloys. However, the quality of the results obtained by this method is very sensitive to various parameters. This paper presents results of the investigation of some influential parameters, like nozzle angle and peening distance, on shot-peening of aluminum alloy Al2024-T3 that can be used in production of new types of high-speed ships in Croatian shipbuilding. Presented experiment results indicate the importance of a careful selection of shot-peening parameters since adversely chosen parameters can even lead to the aggravation of material properties.
Abstract A meshless CFD method is proposed for numerical simulation of incompressible flows and e... more Abstract A meshless CFD method is proposed for numerical simulation of incompressible flows and estimation of hydrodynamic loads during green water events. In this paper, governing equations are described in Finite Differences context, where spatial operators are derived using Weighted-Least Squares. Volume-conservative Lagrangian advection is handled by solving a set of geometrical constraints, while adjusting to moving boundaries represented by triangulated meshes. The validation of the method is performed by simulating four green-water experiments on fixed and moving structures, and comparing the kinematics of flow and hydrodynamic loads during impacts. It is shown that the method accurately reproduces patterns of waves that are wetting the deck, as well as the pressure distribution along the deck. The resulting method intrinsically handles violent fluid–structure interaction with free surface fragmentation, while providing second-order accurate pressure field.
Split Trailing Suction Hopper Dredgers (Split TSHD) have longitudinally-split hull, which symmetr... more Split Trailing Suction Hopper Dredgers (Split TSHD) have longitudinally-split hull, which symmetrically opens when executing gravity-driven unloading of the cargo, while being exposed to various environmental conditions. Even though they have variable hull geometry, their hydrostatic and stability characteristics are usually calculated for initial and unchanged loading conditions only, which is a requirement imposed by classification society stability regulations for TSHD ships [2, 3, 4]. In order to investigate the significance of the discharge process dynamics on actual ship stability, unsteady numerical simulations were performed with the Discrete Element Method (DEM) for symmetrical hopper opening during cargo discharge procedure, without the hull opening failure modes examined. The ship hydrostatic properties, which are pre-calculated analytically using Radial Basis Functions (RBF) for all possible states [11], are used in combination with the solver in order to compute the rig...
One of the main tasks of ship's computational geometry is calculation of basic integrals of s... more One of the main tasks of ship's computational geometry is calculation of basic integrals of ship's hydrostatics. In order to enable direct computation of those integrals it is necessary to describe geometry using analytical methods, like description using radial basis functions (RBF) with L1 norm. Moreover, using the composition of cubic and linear Polynomial radial basis functions, it is possible to give analytical solution of general global 2D description of ship geometry with discontinuities in the form of polynomials, thus enabling direct calculation of basic integrals of ship hydrostatics.
For the prediction of ship resistance in the preliminary stages of the ship design process, naval... more For the prediction of ship resistance in the preliminary stages of the ship design process, naval architects often use methods that are less complex and expensive than CFD simulations and experiments. Michell's thin ship theory can be used to quickly evaluate wave-making resistance, although, the original theory gives poor estimates for conventional hulls. In this work, techniques to improve the theory are introduced that account for viscous and non-linear effects. The improvements are validated by numerical simulation on three profoundly different hull forms: parabolic Wigley hull, Series 60, and a containership hull. Relatively better results were obtained compared to the original thin-ship theory and Holtrop-Mennen’s method. However, further study is necessary to improve the introduced formulations.
The Croatian, as well as European shipbuilding industry, cannot compete with Far East shipbuildin... more The Croatian, as well as European shipbuilding industry, cannot compete with Far East shipbuilding industries in a matter of low prices and short delivery time for production of conventional new ships. The way out from continuously decreasing production lies in orientation towards building more technically demanding and complex objects, and to merge, both, regionally and through production programs. The floating objects, as marine objects without self propulsion systems, equipped with own electrical energy sources, water supplies and waste water treatment systems, that provide object?s autonomy, would be one of very useful production solution, designed in cooperation with architects and curators for different purposes: restaurants, congress centers, cafe bars and disco clubs, apartments, car parking, etc. In the paper some ideas of using a floating objects in coastal cities is presented.
Modern high-speed ships demand application of materials that are light and with a good fatigue st... more Modern high-speed ships demand application of materials that are light and with a good fatigue strength and corrosion resistance. Various aluminum alloys can be technologically improved to match these demands. It is known that shot-peening method can be applied to improve fatigue properties of aluminum alloys. However, the quality of the results obtained by this method is very sensitive to various parameters. This paper presents results of the investigation of some influential parameters, like nozzle angle and peening distance, on shot-peening of aluminum alloy Al2024-T3 that can be used in production of new types of high-speed ships in Croatian shipbuilding. Presented experiment results indicate the importance of a careful selection of shot-peening parameters since adversely chosen parameters can even lead to the aggravation of material properties.
Abstract A meshless CFD method is proposed for numerical simulation of incompressible flows and e... more Abstract A meshless CFD method is proposed for numerical simulation of incompressible flows and estimation of hydrodynamic loads during green water events. In this paper, governing equations are described in Finite Differences context, where spatial operators are derived using Weighted-Least Squares. Volume-conservative Lagrangian advection is handled by solving a set of geometrical constraints, while adjusting to moving boundaries represented by triangulated meshes. The validation of the method is performed by simulating four green-water experiments on fixed and moving structures, and comparing the kinematics of flow and hydrodynamic loads during impacts. It is shown that the method accurately reproduces patterns of waves that are wetting the deck, as well as the pressure distribution along the deck. The resulting method intrinsically handles violent fluid–structure interaction with free surface fragmentation, while providing second-order accurate pressure field.
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Papers by Dario Ban