| 1. |
- Di Caterino, F., et al.
(författare)
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A numerical way for a stepped planing hull design and optimization
- 2018
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Ingår i: Technology and Science for the Ships of the Future - Proceedings of NAV 2018. - : IOS Press. ; , s. 220-229
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Konferensbidrag (refereegranskat)abstract
- Stepped planing hulls enable the feasibility of running at a relatively low drag-lift ratio by means of achieving more optimal trim angle at high speeds than a similar non-stepped hull. Furthermore, stepped planing hulls ensure good dynamic stability and seakeeping qualities at high speeds. However, there is no precise method to analyze these hulls over the full range of operating speeds. For the above-mentioned reason, in this study, a CFD-based design was presented, starting from a non-stepped hull configuration, a multiple step solution was developed and an optimization of the unwetted aft body area behind the steps was performed. The goal of the optimization is the drag reduction and a dynamic stability. The CFD results were compared with the well-known empirical approach and a novel 2D+T analytical method.
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| 2. |
- Niazmand Bilandi, R., et al.
(författare)
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Development of a 2D+T theory for performance prediction of double-stepped planing hulls in calm water
- 2019
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Ingår i: Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment. - : SAGE Publications Ltd. - 1475-0902 .- 2041-3084. ; 233:3, s. 886-904
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a mathematical model based on the 2D+T theory has been developed to predict the performance of two-stepped planing hulls in calm water. It has been attempted to develop a mathematical model without using regression formulas. It leads to development of a computational model with no common limitations related to empirical models which have an individual range of applicability. For this purpose, theoretical solution of water entry of a two-dimensional wedge section has been implemented to compute the pressure distribution over wedge section entering water, and then normal forces acting on the two-dimensional sections are computed. Bottom of the boat has been divided into three different planing surfaces including fore, middle and aft bodies. Computations are performed for each of these surfaces. By integrating the two-dimensional sectional normal forces over the entire wetted length of the vessel, the trim angle, wetted surface and resistance have been obtained. To evaluate the accuracy of the presented method, the obtained results are compared against experimental data and a previous empirical-based method developed by authors. The comparison suggests that the proposed method predicted dynamic trim angle, wetted surface and resistance of double stepped boats with reasonable accuracy. The mean errors in prediction of trim angle, wetted surface and resistance are, respectively, 13%, 16% and 8%. It should also be noted that although computation of running attitudes and resistance of double-stepped planing boats are targeted in this article, the mathematical model has been developed in such a way that it has the potential to model transverse and vertical motions of two-stepped planing hulls in future studies.
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| 3. |
- Tavakoli, S., et al.
(författare)
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Dynamic of a planing hull in regular waves : Comparison of experimental, numerical and mathematical methods
- 2020
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 217
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Tidskriftsartikel (refereegranskat)abstract
- The unsteady planing motion in waves is a complicated problem, that can lead to uncomfortable riding situation and structural damages due to large wave-induced dynamic responses and vertical accelerations. In the current research, this problem is investigated using different approaches, including towing tank tests, Computational Fluid Dynamics (CFD), and the 2D + t model. Results obtained from all three approaches are compared against each other in details. The spectral analysis shows that all motions can be nonlinear, but CFD and 2D + t model may predict weaker nonlinear behaviour at higher speed, especially for the case of vertical accelerations corresponding to longer waves. Interestingly, the vertical acceleration found by 2D + t model is seen to be under-predicted at moderate and long wavelengths and to be over-predicted at short waves. The values of sectional forces found by 2D + t model were compared against CFD results, showing that, while the 2D + t model computes smaller sectional forces, it can also compute negative sectional forces near the bow of the vessel at short waves when the boat exits the water. The emergence of negative sectional forces is likely to be the reason why the 2D + t model over-predicts the vertical acceleration in short waves.
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