Drag reduction for marine vessels using air-filled dimpled surfaces

Abstract

This research involves the use of air-filled cavities as a means for reducing drag experienced by marine vessels. There are many benefits of utilizing this technology; the main benefit is significant energy reduction or smaller carbon footprint in overcoming drag forces exerted by the seawater on the vessels. This Final-Year Project focuses on the use of Computational Fluid Dynamics software ANSYS 14.0 and its solver FLUENT to study the drag characteristics of the multiphase transient flow near air-filled cavities, and yields a final design which optimizes drag reduction.

In this project, the half ellipse geometry is used for the air cavity region and the rectangular geometry is used for the water region to simulate water flow under the vessel’s hull. For 2-dimensional study, the velocity of air emerging from the inlet, the position of the air inlet, and the height of the cavity are varied to achieve minimum drag. Chamfering is then carried out on the optimized model to further reduce the average drag. Convergence studies is done for the final 2D chamfered geometry. For the 3-dimensional study, the optimized 2D geometry is extruded to a length of 6 m to form a 3D model. Same conditions fixed for 2D cases are applied to the 3D. Further analysis of the multiphase flow is carried out. Large Eddy Simulations (LES) turbulence model will be used throughout the course of this project.