Verification of drag-reduction capabilities of stiff compliant coatings in air flow at moderate speeds

• Published in: International journal of naval architecture and ocean engineering Vol. 3; no. 4; pp. 242 - 253
• Main Authors: Boiko, Andrey V., Kulik, Victor M., Chun, Ho-Hwan, Lee, Inwon
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2011; De Gruyter Open; Elsevier; 대한조선학회
• Subjects: Compliant coating; Drag reduction; Turbulent boundary layer; Wind tunnel experiment; 조선공학; Turbulent boundary layer; Wind tunnel experiment; Compliant coating; Drag reduction
• ISSN: 2092-6782; 2092-6790; 2092-6782
• DOI: 10.2478/ijnaoe-2013-0068

Skin frictional drag reduction efficiency of “stiff” compliant coating was investigated in a wind tunnel experiment. Flat plate compliant coating inserts were installed in a wind tunnel and the measurements of skin frictional drag and velocity field were carried out. The compliant coatings with varying viscoelastic properties had been prepared using different composition. In order to optimize the coating thickness, the most important design parameter, the dynamic viscoelastic properties had been determined experimentally. The aging of the materials (variation of their properties) during half a year was documented as well. A design procedure proposed by Kulik et al. (2008) was applied to get an optimal value for the coating thickness. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coatings. The compliant coatings with the thickness h = 7mm achieved 4~5% drag reduction within a velocity range 30~40 m/s. The drag reduction mechanism of the attenuation of turbulence velocity fluctuations due to the compliant coating was demonstrated. It is envisioned that larger drag reduction effect is obtainable at higher flow velocities for high speed trains and subsonic aircrafts.