The effect of the planform of hydrofoils on tip vortex roll-up and cav
itation has been investigated by testing three foils having the same N
ACA 16020 cross section but different shapes. One foil has an elliptic
al shape while the other two are shaped like quarters of ellipses; one
with a straight leading edge and the other with a straight trailing e
dge. Experiments were conducted in the ENSTA, Ecole Navale and IMHEF c
avitation tunnels,with homologous foils of different sizes to investig
ate Reynolds number effects. Hydrodynamic forces as well as cavitation
inception and desinence performance were measured as a function of Re
ynolds number and foil incidence angle. Laser Doppler measurements of
the tangential and axial velocity profiles in the region immediately d
ownstream of the tip were also performed. At equal incidence angle and
Reynolds number, the three foils show different critical cavitation c
onditions and the maximum tangential velocity near the tip increases a
s the hydrofoil rip is moved from a forward to a rear position. Howeve
r, the velocity profiles become more similar with increasing downstrea
m distance, and at downstream distances greater than one chord aft of
the tip, the differences between the foils disappear. The rate of tip
vortex roll-lcp is much faster for the straight leading edge than for
the straight trailing edge foil and, in the latter case, a significant
portion of the roll-up occurs along the foil curved leading edge. The
minimum of the pressure coefficient on the axis of the vortex was est
imated from the velocity measurements and correlated with the desinent
cavitation number for the largest free stream velocities. The correla
tion of data is very satisfactory. Ar the highest Reynolds number test
ed and at equal lift coefficients, the straight leading edge foil disp
lays the most favorable cavitation desinent numbers.