Micro-bubble Drag Reduction by Multi Discrete Hole Plate on SelfPropelled Barge Ship Model

Abstract

Ship resistance is one of the main problems dealing with ship performance and fuel consumption. Microbubble Drag Reduction System (MBDRS) which is applied by injecting air onto the bottom of the hull is a promising technique of active method which it has been developing in various ways. The particular applications of these methods in relatively bottom displacement flat hull (self-propelled barge) are significant to support other available data. Moreover, the complex relationof the ship speeds, injection rates, and hull form take into account in this paper and need to be studied further in which show the optimization between the injection rate and ship speed at the particular cases as well as the bubble and air layer effects account for these results. The injected air bubbles to the bottom of the ships are supposed to modify the turbulent boundary layer properties in which can reduce the hull friction. The objective of this research is to identify the effect of microbubble injection on a self-propelled barge (SPB) model with main dimensions: L = 2000 mm, B = 521.6 mm and T = 52.5 mm. The optimum injector location and injection ratio at each ship speed can be obtained by conducting a towing tank test microbubble injection of self-propelled barge ship model at the after bow (0.35L) and after midship (-0.025L) sections at Fnrange 0.11 -0.31 and injection ratio 0.2 -0.6. Bubble size distribution for each case describes the phenomena of the results obtained. There is the pilling-up effect of the microbubble during the propagation covering the bottom surface hull and so does in this experimental results visualization. Sometimes the size seems bigger in the after side due to the interaction between different injection rate and different model speed. The size of the microbubble in micro size while come out from the porous media as shown in the scale bar of bubble visualization. The test results show that after bow injection area gives the lowest drag reduction compares to the after midship injection with different optimum injection ratio for each case.