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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

EXPERIMENTAL INVESTIGATION OF DRAG REDUCING MECHANISM OF COMPLIANT COATING WITH OPTIMAL VISCOELASTIC PROPERTIES

pages 891-895
DOI: 10.1615/TSFP6.1430
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要約

In this study, a wind tunnel experiment has been performed to investigate the effect of the dynamic viscoelastic properties of a silicone RTV rubber on the drag reducing efficiency in turbulent boundary layer. A specially designed flat plate was mounted vertically over the center line in the wind tunnel of the Pusan National University. The plate is 2 m long, 0.8 m high and 8 cm thick. The measurements were performed in velocity range from 15 to 30 m/s. Removable insertions of 0.55×0.25m2 size were mounted in the trailing part of the plate. The following set of the insertions was designed and manufactured: metal standard with polished surface and coated with a compliant material of different thickness. The compliant coatings were manufactured of a silicone rubber Silastic® S2 (Dow Corning Inc.). To modify the viscoelastic properties of the rubber, its composition was varied: 90% of the rubber + 10% catalyst (standard), 92.5% + 7.5% (weak), 85% + 15% (strong). Modulus of elasticity, the loss tangent and Poisson's ratio were measured in detail for these materials in the frequency range from 40 Hz to 3 KHz using the proposed innovative technique. The skin friction drag was measured by the strain balances mounted in the trailing part of the plate over removable insertions. The development of velocity profiles measured at all four surfaces under study are found to be self-similar. The strong compliant coating achieved 5% drag reduction within a velocity range 20~40 m/s.

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