International Shipbuilding Progress - Volume 62, issue 1-2

Authors: Hu, Li-fen | Tian, Zhongmin | Sun, Zhongyu | Zhang, Quanzhong | Feng, Baofu

Article Type: Research Article

Abstract: A good counter-flooding strategy is vital to the decision maker in case of emergency, but how to evaluate the scheme is still lack of a definite function. To establish a definite evaluation standard, this paper presents a counter-flooding decision model for scheme evaluation and decision support in shipboard flooding emergency. It adopts genetic algorithm to solve the proposed optimization model, which involves the combination of counter-flooding tanks that should be filled or evacuation in order to achieve an optimal response to a flooding accident. The genetic algorithm is developed with roulette wheel selection, one-point crossover, mutation, and iterative process continues …until terminating condition is encountered. The stopping criterion proposed in this paper is the tilt angle, also the heeling angle is another terminate rule. The computational results validate the effectiveness of proposed optimization model and genetic algorithm. Show more

Keywords: Counter-flooding, decision model, genetic algorithm, evolutionary strategy

DOI: 10.3233/ISP-140114

Citation: International Shipbuilding Progress, vol. 62, no. 1-2, pp. 1-15, 2015

Authors: Edessa, Desta Milkessa | Bronsart, Robert

Article Type: Research Article

Abstract: In reverse engineering (RE) there are several strategies, technologies and mathematical numerics involved from data acquisition system to surface fitting. This makes the reverse engineering methods always computationally expensive, time taking and more over error prone. Therefore, developing application specific RE method can offer the required quality with reasonable associated time and then cost. This paper presents a practical and efficient ship hull form reconstruction strategy which align the reverse engineering results into traditional hull form design procedures. The developed approach reads points from a set of unorganized noisy 3D point cloud and fits to cross-sectional curves network (transversal and …waterline sections). It consists of several point cloud pre-processing functions, the curves fitting (interpolation and approximation) and presents different Non-Uniform Rational B-Spline (NURBS) surface fitting approaches from curves network. The point cloud pre-processing removes outliers and extracts transversal and waterline sections. It is also equipped with different functions to successfully filter and smooth point cloud so that it can be fitted to curves by interpolation or approximation. The suitability of different existing surface generations (lofting, patching and surface from curves network) are experimented based on cross-sectional curves. The developed approach is tested against two hull forms (scanned and manually generated) point cloud. The tests reveals that, the developed approach is time saving and suitable for hull form reconstruction. Show more

Keywords: Reverse engineering, hull form, point cloud, curves network, surface fitting

DOI: 10.3233/ISP-150115

Citation: International Shipbuilding Progress, vol. 62, no. 1-2, pp. 17-42, 2015

Authors: Chandrasekaran, Srinivasan | Madhavi, N.

Article Type: Research Article

Abstract: Presence of perforated members in ocean structures reduces the wave force on the damaged member because of the wave structure interaction; breakwaters with perforated members are classical examples of such kind. While retrofitting and rehabilitation is usually related to strengthening of members, the presented concept is a novel attempt as it addresses decrease in the encountered forces on the members. The present study is attempted numerically to quantify the force reduction on ocean structures encompassed by perforated outer covers with different geometric configuration of outer cylinder. Present study highlights the reduction of hydrodynamic response of perforated members under regular waves …using numerical simulation. Hydrodynamic responses of cylinders with and without perforated cover are estimated for different sea states which are categorized as low, medium and steep wave steepness index. Based on the studies carried out, it is shown that there is average force reduction of about 60% is seen for the chosen geometric configuration. For this study the orientation of the structure under regular waves are also considered. Show more

Keywords: Force reduction, hydrodynamic response, perforated members, ocean structures, orientation of structure

DOI: 10.3233/ISP-150116

Citation: International Shipbuilding Progress, vol. 62, no. 1-2, pp. 43-56, 2015

Authors: Dash, Anil Kumar | Nagarajan, Vishwanath | Sha, Om Prakash

Article Type: Research Article

Abstract: An 8 DoF ship maneuvering motion model for a twin-propeller twin-rudder high-speed hull form is developed from captive model experiment data available from literatures. The degrees of freedom considered are surge, sway, yaw, roll, rudder rate and propeller rate. Besides maneuvering motion model, variation of port/starboard propeller thrust and torque and port/starboard rudder normal force and rudder torque are also included in the model. An uncertainty analysis computation for the mathematical model is carried out. Uncertainties in the experimental data and the polynomial curve fitting during modeling are included in the computation. It is shown that the mathematical model uncertainty is …higher than the experimental uncertainty. Uncertainty is propagated to full-scale zigzag maneuver using the conventional Monte Carlo simulation (MCS) method. The uncertainty analysis results will be useful for further improvement of mathematical model, validation of CFD simulation results of appended hull maneuvering tests, etc. We have also shown the utility of asymmetric operations of the twin-propeller and twin-rudder by carrying out full-scale simulation a zigzag maneuver and showing the variation of the rudder normal force and torque. Show more

Keywords: Maneuvering model, twin-propeller asymmetry, twin-rudder asymmetry, uncertainty assessment, MCS

DOI: 10.3233/ISP-150117

Citation: International Shipbuilding Progress, vol. 62, no. 1-2, pp. 57-111, 2015