WIND-TUNNEL EXPERIMENTS ON A FULLY APPENDED LAMINAR-FLOW SUBMERSIBLE FOR OCEANOGRAPHIC SURVEY

This paper reports experimental measurements of the hydrodynamic force s acting on a low drag submersible. The model was manufactured using s tandard, cost-effective methods without undue attention paid to the ro ughness or waviness of the model's surface. It was seen, using flow vi sualisation techniques, that the laminar boundary layer extended over 70% of the vehicle length; furthermore, no separation of the flow was seen over the remaining 30% of the body. Hydrodynamic forces were meas ured, and a significant reduction in drag was found compared with stan dard turbulent submersible shapes. The low drag performance was quite resilient to changes in incidence, showing a large drag ''bucket'' for angles of incidence between +/- 4-degrees. With the addition of a set of cruciform fins at the rear of the body, incorporating control surf aces, it was found that for a centre of gravity position forward of 41 .3% of the body length, the vehicle would be statically stable both st ick-free and stick-fixed. Finally, using a pitot tube wake rake the ve locity profile of the boundary layer at the propeller location was fou nd to be that of an attached, turbulent boundary layer closely matchin g a 1/5.35 power law. The importance of full interference measurement tests to allow for the support strut effects is clearly demonstrated.