Large eddy simulation of a marine propeller with leading edge tubercles

Abstract

The results of large eddy simulations on a cylindrical grid consisting of 5.8 × 109 points are reported, dealing with marine propellers with leading edge tubercles (LETs). They are compared with the performance and flow fields of the baseline geometry without tubercles. In general, the efficiency of propulsion is not improved, but a substantial effect is produced on the development of the flow across the propeller blades. The minima of pressure on the suction side of the blades are confined in the troughs of the leading edge, with the potential of reducing the overall extent of the area of cavitation (cavitation funneling effect). In addition, local maxima of turbulence are produced on the suction side of the blades by the onset of streamwise vortices at the troughs of the LETs. Although the wake development is slightly modified across blade geometries, no obvious influence of the LETs on the major wake structures is observed. Due to their early breakup, the vortices developing across the span of the propeller blades, including those originating at the LETs, are able to affect indeed a very short extent of the propeller wake. Its dynamics is still dominated by the tip and hub vortices, as for the conventional design of the propeller. Meanwhile, the intensity of the root vortices shed by the conventional propeller is substantially reduced in the wake of the tubercled propellers, thanks to the modified geometry of the blades at their root, resulting also in a slightly slower instability of the hub vortex.