ABSTRACT
This paper concerns with investigating experimentally and numerically two different
methods of drag force reduction over underwater vehicles. The first method is the
viscous friction drag reduction by air injection in the near wall layer and the second
one is the pressure drag reduction by changing the vehicle nose profile. An
experimental test rig was designed and manufactured with all required
measurements of drag force and water velocity. Additionally, the experimental work
was conducted on six underwater vehicle (torpedo) models with different nose
profiles and lengths at variable water velocities. Computational Fluid Dynamic (CFD)
simulation was performed using ANSYS. Furthermore, the computations were
extended to depict the velocity and pressure contours around two models having
different body nose profiles at water velocity of 50 m/s. The total drag forces over
eight models were predicted and compared. The numerical results showed good
agreement with the experimental ones. The experimental results showed that, for
speed range of 1-2.5 m/s the stubbed nose profile had the highest drag. On the other
hand, the stepped conical nose profile had the lowest drag force. Moreover, the
experimental results of air injection showed a decrease in drag force in the velocity
range of 1.7-2.5 m/s but an increase in the drag for velocity range of 1-1.7 m/s was
remarked. Finally, there was a significant decrease in drag force of elliptical nose
model compared to other models over the velocity range of (0 to 50 m/s).