International Shipbuilding Progress - Volume 69, issue 2

Authors: Wellens, Peter

Article Type: Editorial

DOI: 10.3233/ISP-229001

Citation: International Shipbuilding Progress, vol. 69, no. 2, pp. 91-92, 2022

Authors: Lovato, Stefano | Toxopeus, Serge | Settels, Just | Keetels, Geert

Article Type: Research Article

Abstract: The ship’s resistance and manoeuvrability in shallow waters can be adversely influenced by the presence of fluid mud layers on the seabed of ports and waterways. Fluid mud exhibits a complex non-Newtonian rheology that is often described using the Herschel–Bulkley model. The latter has been recently implemented in a maritime finite-volume CFD code to study the manoeuvrability of ships in the presence of muddy seabeds. In this paper, we explore the accuracy and robustness of the CFD code in simulating the flow of Herschel–Bulkley fluids, including power-law, Bingham and Newtonian fluids as particular cases. As a stepping stone towards the …final maritime applications, the study is carried out on a classic benchmark problem in non-Newtonian fluid mechanics: the laminar flow around a sphere. The aim is to test the performance of the non-Newtonian solver before applying it to the more complex scenarios. Present results could also be used as reference data for future testing. Flow simulations are carried out at low Reynolds numbers in order to compare our results with an extensive collection of data from the literature. Results agree both qualitatively and quantitatively with literature. Difficulties in the convergence of the iterative solver emerged when simulating Bingham and Herschel–Bulkley flows. A simple change in the interpolation of the apparent viscosity has mitigated such difficulties. The results of this work, combined with our previous code verification exercises, suggest that the non-Newtonian solver works as intended and it can be thus employed on more complex applications. Show more

Keywords: CFD, sphere, drag coefficient, regularisation, uncertainty estimation, validation

DOI: 10.3233/ISP-220002

Citation: International Shipbuilding Progress, vol. 69, no. 2, pp. 93-117, 2022

Authors: Bos, R.W. | van der Eijk, M. | den Besten, J.H. | Wellens, P.R.

Article Type: Research Article

Abstract: Loads due to wave impacts are a limiting factor in the design of liquefied natural gas (LNG) tankers and their insulation. The current methodology considers the load independent from the response of the tank. Better tanks can be designed by knowing the effect of the interaction between the wave loads and the response, however predicting these effects is computationally expensive. In this paper a new application of the non-hydrostatic shallow water equations are presented, namely as a reduced order model (ROM) for fluid structure interaction for wave impacts. Our ROM is compared to a high fidelity model. The proposed ROM …is fast and accurately predicts the total impulse and added mass, and therefore the general behaviour of the structure during the free vibration phase. It does however not always accurately predict the maximum force. It is therefore considered an appropriate tool for a first screening of the loads for which fluid-structure interaction is important, after which a more accurate method can be used to evaluate the most interesting cases. A sensitivity study is performed for various impact angles and velocities, showing that the importance of fluid structure interaction depends highly on the specific situation. Show more

Keywords: Fluid-structure interaction, sloshing, dynamics, non-hydrostatic shallow water equations, wave impact

DOI: 10.3233/ISP-220003

Citation: International Shipbuilding Progress, vol. 69, no. 2, pp. 119-138, 2022

Authors: Gabriel, Maarten | Wellens, Peter

Article Type: Research Article

Abstract: A two-dimensional (2D) boundary element method is developed for the rapid assessment of the hydrodynamic performance of floating structures in waves. The boundary element method is based on potential flow and has panels along all boundaries of the fluid domain – not only along the boundary of the floater – to make the extension to second order feasible. Panels along all boundaries requires the development of generating absorbing boundary conditions for use at radiation boundaries to send incident waves into the domain while absorbing waves originating from the floating body at the same boundary, at the same time. The model is verified …by means of conservation of energy of a heaving wave energy converter, and by means of the propagation of second-order waves. The performance in terms of conservation of energy with 12 panels per wave length is good, the generating absorbing boundary condition works according to expectation and the second-order wave propagation corresponds to theory. Show more

Keywords: Boundary element method, second order, generating absorbing boundary condition, wec

DOI: 10.3233/ISP-210007

Citation: International Shipbuilding Progress, vol. 69, no. 2, pp. 139-159, 2022

Authors: Hao, Wu | Cong Hong, Lu | Qiang, Liu | Xin, Yu | Wei, Fan | Bi Ye, Peng

Article Type: Research Article

Abstract: Background: The green ship technologies are gaining in importance in diverse areas of ship design. Objective: To explore the energy-saving and environmentally friendly ship during the primary ship designs stage. Methods: A hull form optimization method based on the full parametric modeling is proposed, in which the Computational Fluid Dynamic (CFD) analysis is integrated, and the algorithms of Sobol and NSGA-II are used. Taking a 674 m3 single trawler as an example, the full parametric modeling of forebody hull form is adopted by employing an F-spline curve with the software CAESES and the total resistance of …the full-scale ship is computed by the integrated software SHIPFLOW numerically. Results: It is proved that the presented optimization method can engage well in the automation process of the hull form design under the constraints of displacement and longitudinal center of buoyancy. Compared with the initial hull form, the total resistance of the optimal ship at the design speed of 11.5 kn decreases 12.2%. Conclusions: It indicates that the proposed method of hull form optimization based on full parametric modeling proposed in this paper has better engineering applicability and broad application prospect in practical ship design practices. Show more

Keywords: Single trawler, hull form optimization, full parametric modeling, f-spline, CFD, NSGA-II

DOI: 10.3233/ISP-220006

Citation: International Shipbuilding Progress, vol. 69, no. 2, pp. 161-179, 2022