Experimental Study on the Hydrodynamic Drag Reduction of a Catamaran Vessel Using Micro-Bubbles Injection Method

Increase in speed and range of hydrodynamic systems, which ultimately lead to enhance in its performance, is one of the most important goals in design of marine systems. Achieving this goal, is required to reduce hydrodynamic drag. Micro-bubble injection technique is one of the active methods to reduce hydrodynamic drag. This approach has high efficiency for drag reduction and in comparison to the other active methods, it has less environmental pollution and it is easy to install on the hydrodynamic vehicles. The main aim of this research is experimental investigation of the hydrodynamic drag reduction of a catamaran vessel using micro-bubbles injection method and determining the effective parameters on the performance of this technique. For this purpose, at first, a catamaran vessel model is made with length of 70cm. In the following, the micro-bubble injectors are designed and installed with necessary equipment, for measurement of air flow rate, on three locations at fore, middle and aft sections of model. Experimental tests are carried out in towing tank laboratory for catamaran vessel with and without injection system for Froude numbers in the range of 0.44 to 1.48 and finally, the ability of micro-bubbles injection method to reduce hydrodynamic drag of catamaran vessel model is evaluated at different velocities. The experimental results revealed that, the average hydrodynamic drag reduction is attained about 17%. additionally, by increasing Froude number, the capability of miro-bubble injection method to reduce drag has been decreased from 21.15% to 11.8% for Fr=0.54 and Fr=1.25, respectively.