Numerical Simulation of Micro-Bubble Drag Reduction on a Container Ship
Date Issued
2009
Date
2009
Author(s)
Huang, Sau-Ting
Abstract
This study conducted simulations of injecting air and water into the flow field around a container ship by two-phase flow method of computational fluid dynamics (CFD). In order to understand behavior of air-water mixed fluid in different flow conditions, many conditions were investigated and analyzed. The influence parameters were taken into account , including injection velocities, void fractions of air , ship speed and injection positions . These results were helpful to determine which position and condition is better for drag reduction. BSL k- turbulence model and CSBC RD542_2 model were used to proceed numerical computing . At first , the design condition of void fraction of air were set between 10% to 90% , and inject position were at the end of bulbous bow. It has been shown that the drag reduction rate will decrease when void fraction of air increase and void fraction between 10% to 20% has better reduction rate. Then we used constant air-water ratio fluid (10%) to inject into four other different positions and compared the track of bubble flow with friction reduction rate . t last , we want to observe how the other influence factors can effect friction reduction rate . So the conditions of three different Froude number , three different jetting velocities , three different void fractions of air and four different positions were desighed to compute and compare the results with friction reduction rate. Among these results , we found that the reduction capability was better when the jet direction faced downward ship hull rather then toward hull side. And when ship speed increase , the flow field can allow injecting more air quantity as well as producing higher friction reduction rate.
Subjects
micro-bubble
drag reduction
numerical simulation
CFD
Type
thesis
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