This research investigates viscous drag reduction methods that may be applied to certain marine vehicles. These methods include the injection of microbubbles into the boundary-layer and the use of riblets and various transition-control devices. Experiments were performed in the USNA towing tank with two single rowing shells (hull shapes for which the viscous resistance is dominant). Resistance, sinkage, and trim were measured for speeds up to 20 ft/sec. In the case of air injection, the residual resistance was a function of interactive viscous, form, and wave making components making it difficult to ascertain whether or not the viscous component was actually reduced, despite the increase in overall resistance. Riblet surfaces produced up to 30 to 4 percent overall vehicle drag reduction, which is consistent with previous results for forms whose frictional resistance accounts for about 85 percent of the total resistance. While the overall vehicle drag was increased with the addition of a trip wire to the bare hull at low velocities, there was drag reduction up to 2 to 3 percent at the highest velocities, possibly due to venting of the trip wire. The maximum drag reduction of about 6 percent was obtained with both riblets and trip wire for the maximum velocity of 20 ft/sec. Results for the combination of riblets and trip wire were apparently additive across the velocity range of the experiment. (JHD)


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    Title :

    Viscous Drag Reduction for Slender Surface Craft


    Contributors:

    Publication date :

    1989


    Size :

    92 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English




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