Experimental and Computational Characterization of a Hydrofoil System for a Retrofit Inflatable Boat Platform

Abstract

The Center for Marine Autonomy and Robotics at Virginia Tech has been contracted by the Office of Naval Research to design, test, and validate a hydrofoil retrofit kit for a rigid- hull inflatable boat, using fully submerged, flapped hydrofoils to improve small-craft speed and ride quality. The fore foil of this system was first characterized analytically, then measured directly in a tow tank across a wide matrix of speed, incidence, and flap deflection. A three-dimensional CFD model of the isolated foil was developed and validated against these measurements. The validated model was then extended to the complete, integrated starboard-side foil system, and used to evaluate a strut fairing and a wingtip endplate as drag-reduction and lift-recovery devices. The fairing was found to increase lift and reduce drag at the same time, while the endplate recovered further lift at a moderate drag cost. Together, these results indicate good potential for hydrofoil retrofits of this kind. However, full validation of the craft's dynamic takeoff behavior would require further development of a coupled fluid-body simulation and real world testing of the complete system.