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Microbubble Skin Friction Reduction on an Axisymmetric Body
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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A reduction in skin friction drag is shown when gas is introduced into the liquid turbulent boundary layer of a submerged axisymmetric body. The 89 mm diameter, 632 mm long body has an cylindrical balance 273 mm long. Free stream speeds in the 305 mm diameter tunnel are as high as 17 msec, giving length Reynolds numbers of up to 10 million. In general, skin friction reduction is shown to increase with increasing free stream speed. At high speeds, helium injection is shown to be more effective at reducing skin friction than is air injection. Maximum skin friction reduction is near 80--a value in good agreement, with the maximum value observed in the flat plate work of Madavan, Deutsch and Merkle MDM. Maximum skin friction reduction is found at 17 msec for the axisymmetric case, however, as opposed to 5 msec for flat plate work.
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