Environmental issues and rising fuel prices necessitate better energy efficiency in all sectors. Shipping industry is a stakeholder in environmental issues. Shipping industry is responsible for approximately 3% of global CO2 emissions, 14-15% of global NOX emissions, and 16% of global SOX emissions. Ship trim optimization has gained enormous momentum in recent years being an effective operational measure for better energy efficiency to reduce emissions. Ship trim optimization analysis has traditionally been done through tow-tank testing for a specific hullform. Computational techniques are increasingly popular in ship hydrodynamics applications. The purpose of this study is to present MOERI container ship (KCS) hull trim optimization by employing computational methods. KCS hull total resistances and trim and sinkage computed values, in even keel condition, are compared with experimental values and found in reasonable agreement. The agreement validates that mesh, boundary conditions, and solution techniques are correct. The same mesh, boundary conditions, and solution techniques are used to obtain resistance values in different trim conditions at Fn = 0.2274. Based on attained results, optimum trim is suggested. This research serves as foundation for employing computational techniques for ship trim optimization.
Passive and active flow control methods are used to manipulate flow fields to reduce acoustic signature, aerodynamic drag and heating experienced by blunt bodies flying at supersonic and hypersonic speeds. This paper investigate the use of active opposing jet concept in combination with geometric variations of the opposing jet nozzle to alleviate high wave drag formation. A numerical study is conducted to observe the effects of simple jet as well as jet emanating from a divergent nozzle located at the nose of a blunt hemispherical body. An initial discussion is presented of the complex shock wave pattern flow physics occurring when opposing jet ejected from a nozzle under various operating conditions interacts with the free stream flow. The complex flow physics that include long penetration and short penetration mode is studied in conjunction with effect on drag. The numerical setup consists of supersonic free stream flow interacting with an opposing sonic jet under varying pressure ratios. Initial computational results are validated by identifying prominent flow features as well as comparing available experimental data of surface pressure distributions. Preliminary validation is followed by the introduction of a divergent nozzle in the blunt body nose region. A series of numerical iterations are performed by varying nozzle geometric parameters that include nozzle divergent angle and nozzle length for a certain jet pressure ratio. Long penetration mode, short penetration mode as well as flow separations are captured accurately during the analysis. The results show a considerable reduction in drag by the use of a divergent nozzle. Specifically, 46 % and 56% reduction in drag coefficient is achieved at pressure ratio of 0.6 and 0.8 respectively in the divergent nozzle cases as compared to the simple blunt body without any nozzle.
Environmental issues and nsmg fuel prices necessitate better energy-efficiency in all sectors. Shipping industry is one of the stakeholders in environmental issues. Shipping industry is responsible for 3 % of global C02 emissions, 14-15 % of global NOx emissions and 16 % of global SOx emissions. Shipping industry also has critical role in global economy since 90 % of world trade goods are carried by ships. This trade has little or no alternate means of transportation other than ships at this point and foreseeable future. In addition, shipping is a better environmental option for transportation compared to other available means of transportation due to lowest gC02/ton.km emissions. European Union (EU) and United Nations Framework Convention on Climate Change (UNFCCC) are pushing hard to regulate emissions in all sectors. International Maritime Organization (IMO) is working on regulating emissions from shipping with unprecedented attention and it seems clear that emissions from shipping will be regulated within few years. Furthermore, continuously rising fuel prices are also a reason to focus on new ways for better energy-effectiveness in addition to better environmental performance. Green ship concept requires exploring and implementing technologies/practices on ships to reduce emissions.Propeller efficiency is an important area to increase efficiency and reduce emissions since propellers are merely around 60 % efficient. This paper provides a comprehensive review of the propeller efficiency options to increase efficiency and reduce emissions. The paper will discuss basic concepts and principles, and popular technologies for enhancing propeller efficiency. The author will also comment on the core-issues and challenges, and scope for future development in propeller efficiency area.
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