Full-scale unsteady RANS CFD simulations of ship behaviour and performance in head seas due to slow steaming

Loads for use in the design of ships and offshore structures

Dynamic overset CFD simulations of wind turbine aerodynamics

The KCS container ship was investigated in calm water and regular head seas by means of EFD and CFD. The experimental study was conducted in FORCE Technology’s towing tank in Denmark, and the CFD study was conducted using the URANS codes CFDSHIP-IOWA and Star-CCM+ plus the potential theory code AEGIR. Three speeds were covered and the wave conditions were chosen in order to study the ship’s response in waves under resonance and maximum exciting conditions. In the experiment, the heave and pitch motions and the resistance were measured together with wave elevation of the incoming wave. The model test was designed and conducted in order to enable UA assessment of the measured data. The results show that the ship responds strongly when the resonance and maximum exciting conditions are met. With respect to experimental uncertainty, the level for calm water is comparable to PMM uncertainties for maneuvering testing while the level is higher in waves. Concerning the CFD results, the computation shows a very complex and time-varying flow pattern. For the integral quantities, a comparison between EFD and CFD shows that the computed motions and resistance in calm water is in fair agreement with the measurement. In waves, the motions are still in fair agreement with measured data, but larger differences are observed for the resistance. The mean resistance is reasonable, but the first order amplitude of the resistance time history is underpredicted by CFD. Finally, it seems that the URANS codes are in closer agreement with the measurements compared to the potential theory.

EFD and CFD for KCS heaving and pitching in regular head waves

Hydroelastic impact of a wedge-shaped body

Strongly coupled fluid―structure interaction method for structural loads on surface ships

This paper presents simulation results of the structural response of a surface vessel advancing in head seas. In this particular fluid-structure interaction problem, the discretized geometry in the fluid domain is significantly different than that of the structuralmodel. It is therefore necessary to use interpolation to transfer information between the two domains. In this paper we discuss a numerical procedure to obtain the dynamic response of a marine vessel based on fluid-structure interaction as applied to the test case of the S175 container ship. The vessel is advancing in head seas, and the sea conditions result in bow-flare and bottom impact slamming. The fluid and structure interact in a one-way coupled scheme where the fluid stresses are applied to the structural modal model. The simulation results are compared to previously published experimental data.

Dynamic Response of a Marine Vessel Due to Wave-Induced Slamming

During the operation of ships in harsh environmental conditions the ship structure is subjected to large loading due to excitation of large waves that are of the same size of the vessel, as well as to localized loading that occurs when the shell plating re-enters the water with a vanishingly small contact angle between the body and the water surface. This second type of extreme loading occurs over very small space and time scales, and the magnitude of the forcing depends non-linearly on the environmental conditions such as impact velocity and effective deadrise angle. Ships are designed with consideration for impact loading, but the methods are crude and leave designers with little confidence that the resulting structures are prepared for the loading that they see in service. A model problem that represents a simplified slamming event is the impact of an elastic wedge upon a calm-free surface. This problem has been studied numerically and experimentally [1-3]. In the present work, we use the OpenFOAM CFD library to predict the hydrodynamic forcing on the relevant geometry of the ship during a slamming event. We use the commercial FEA software ABAQUS to perform modal extraction of a wet structural model of the ship. We then couple the results from the two programs using our own research tools to predict the structural response in the time domain. In our presentation, we will give an overview of our simulation method and process, and show results for several validation cases and compare with theoretical and experimental results from the literature [1-3]. Also, we will show an application of our method to the case of stern slamming of the JHSS vessel. We will pay particular attention to how we have incorporated the OpenFOAM library into our analysis process.

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Fluid-structure interaction during ship slamming

This paper presents the results of the structural response due to slamming in the stern region of the Joint High Speed Sealift (JHSS) vessel. A slamming event is identified by performing rigid-body large-amplitude seakeeping simulations using the LAMP program. The event is characterized by the relative motion between the free-surface and hull at a specific point near the stern of the vessel. The structure is developed using ABS and other conventional design guidelines, and it is analyzed using the commercial FEA software ABAQUS. The stress of the fluid on the structure is obtained by using a computational fluid dynamics (CFD) solver built on the open source CFD Library OpenFOAM. The fluid stress is applied to the modal model of the structure using a robust and flexible grid-matching routine. Finally, the structural response is determined in the time domain by solving the system of modal equations of motion.

Donghee Lee

Papers

Hydroelastic impact of a wedge-shaped body

Strongly coupled fluid―structure interaction method for structural loads on surface ships

Dynamic Response of a Marine Vessel Due to Wave-Induced Slamming

Fluid-structure interaction during ship slamming

Hydroelastic impact of stern structure using CFD and FEA