Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019 NUMERICAL MODELING OF A VERY LARGE CRUDE OIL CARRIER USING ANSYS


CFX: A CASE STUDY OF SALINA (DOI No: 10.3940/rina.ijme.2019.a4.560)


H Hakimzadeh, Department of Marine Sciences, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University, Iran, M Torabi Azad*, Department of Physical Oceanography, North Tehran Branch, Islamic Azad University, Iran, M A Badri, Isfahan University of Technology, Research Institute for Subsea Sciences & Technology, Iran and F Azarsina, Department of Marine Structures, Faculty of Engineering, Science and Research Branch, Islamic Azad University, Iran andM Ezam, Department of Marine Sciences, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University, Iran


SUMMARY


Specification of the frictional resistance values of tankers is the first step in managing their fuel consumption. Drag force of a very large crude oil carrier has been calculated using the numerical simulation method. With application of the ANSYS CFX software, the scaled model of the mentioned tanker with the length of 2.74 meters, width of 0.5 meters, draft of 0.17 meters was used for numerical simulation of the drag force in the tanker. Furthermore, the numerical solution of the drag force of the model was performed for 5 different speeds ranging from 0.65 to 0.85m/s. Based on the validations carried out, with mean drafts of 8 and 16.5cm, the difference between the results of the experimental and numerical models at low speeds was about 7%. However, the difference was observed to be up to 15% at higher Froude numbers. The results of the present study with respect to the SALINA are based on the method presented in ISO 19030 standard addressing the performance monitoring during vessel servicing.


1. INTRODUCTION


Shipping companies are constantly involved in the development and improvement of their fleet operations as well as application of optimum fuel consumption techniques. Hence, a good number of researchers are concerned about the identification and minimization of the factors affecting the resistance on the vessels’ hull taking advantage of various scientific methods. In comparison with vessels traveling shorter distances, vessels traveling long voyages have fewer options for reducing or optimizing their fuel consumption. That is why it is very crucial to recognize the effect of the hull and propeller roughness on the skin friction and fuel consumption of an ocean-going tanker in various marine environmental conditions. Increasing drag forces leads to an increase in fuel consumption. The most expensive operating cost of a vessel during a voyage is related to the cost of its fuel consumption, which accounts for more than half of the total cost of a voyage. In this regard, the 19030 standard, aimed at monitoring the optimal performance of the vessel, has provided guidelines and scientific methods that are constantly being developed and updated. According to the mentioned standard, the use of computational fluid dynamics to estimate the resistance of a vessel to various drafts is of great significance (Park, et al, 2017). Numerical methods performed using computational fluid dynamics software impose less cost on the owners and provide more details of the simulation results. However, due to lesser accuracy of the results, the findings of the numerical model should be compared with those of the experimental simulation to pursue the validation goals. One of the problems encountered in identifying the drag of vessels’ hull is scaling the small-scale roughness of their hull, in proportion to their full-scale dimensions. In recent years, direct numerical simulation (DNS) has been


©2019: The Royal Institution of Naval Architects


used as a more reliable scientific method to thoroughly comprehend the physics of the flow on the vessels’ sides. However, it must be mentioned that this method can only be implemented on a limited scale of Reynolds numbers. In 2004, Zalek, et al, has conducted a research addressing the effects of drag. Van et al. (1998) measured the flow around a very large crude carrier. Ogiwara et al. (1994) conducted studies on series 60 ships and calculated the pressure distribution around the hull surface. Jones and Clarke (2010) performed the numerical simulations of the current flow around a warship with the application of the ANSYS Fluent software. Obreja et al. (2005) have conducted several experimental tests on a bulk carrier. Korkut and Usta (2013) performed studies on five different types of aluminum plate, which examined increasing the resistance of the ship’s hull in response to increasing the hull roughness with the application of a computational fluid dynamics model. Furthermore, Lungu (2007) conducted a research on a three- dimensional flow of surface turbulence around a liquid petroleum gas carrier. In 2009, Donnelly focused on the effect of turbulent boundary layer on the ship resistance. Moreover, Jakobsen (2010) presented the turbulent model of transverse flows entered on the vessel body. Hakan et al. (2007) calculated the resistance of a vessel model and compared the obtained value with the experimental results. Banks et al. (2010) quantified the resistance components of a container ship using ANSYS CFX software and compared the results with the experimental findings.


The purpose of the present study is to measure the hull drag force of SALINA. The findings will pave the way for future studies to use the calculated drag force values to measure the actual increase of vessels’ fuel consumption and involuntary reduction of their speed with consideration of the standard 19030 guidelines


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