Investigation of the air-lubrication effect on friction resistance

Abstract

The new IMO (International Maritime Organization) introduced new requirements (some of them compulsory) for reducing the GHG emissions from shipping. These requirements stimulated the implementation of new energy saving devices and methods and revived the interest to some, already known but not sufficiently studied. One of the latter is the idea of air lubrication of the hull. Since the resistance component, affected mostly by air lubrication, is frictional resistance, the study will consider a simplified model of a flat plate, using CFD (ANSYS Fluent and Compass Tdyn). Different configurations of air-injection openings/slots will be investigated with varying combinations of air flow fate and water flow velocities. The hydrostatic pressure can be also prescribed and varied to simulate different depths of the plate (ship bottom). The computations will monitor the air-layer pattern and thickness and the effect on frictional resistance. Experiments can be carried out (depending on the state of refurbishment of the small towing tank of TU-Varna) with a flat-bottom barge to validate, at least qualitatively, the numerical results. Estimation of the power demand for air injection to evaluate the trade-off between resistance reduction and air-blow expenses.