Turbulent Drag Reduction Using Compliant Coatings

Abstract : An experimental study was carried in a water tunnel, where the drag of several compliant coatings in the turbulent boundary layer was measured. An axi-symmetric test model similar to that used by NUWC was designed and built, and identical compliant coatings were tested as a part of collaboration between UK, U.S. and Russia. While experimental results in the UK show small drag reductions by up to 3% in some of the compliant coatings tested, skin-friction drags of compliant coatings measured at MIT are consistently greater than that of rigid surface. The Russian data are not yet available at the time of writing this report. The aging of the compliant coatings are thought to be the reason for these discrepancies. A better coordination will be required for the rest of the program to overcome this problem.