Turbulent Boundary Layer Drag Reduction On An Axisymmetric Body Using Circular Ring Manipulators

Proceedings of the 4th European Drag Reduction Meeting

Drag reduction by ejection of high molecular weight polymers on free-running bodies of revolution has been demonstrated repeatedly. The quantities of polymer required have made the gains achieved marginal from a volume utilization tradeoff. The ejection process is hypothesized to be the controlling factor. Limited data obtained in pipe flow and flat plate flow experiments on ejection into developing boundary layers indicate a drastic reduction in polymer requirements for equivalent percent drag reductions. Extension to axisymmetric flow could result in significant achievable gains to volume utilization. This study examines these polymer ejection processes through measurement of wall and boundary layer concentration profiles and through a photographic study of the boundary layer. Tests performed with fresh water ejection and solutions of the drag reducing polymer, Polyox WSR-301, lead to the hypothesis that optimal ejection for minimum polymer usage requires ejection into a laminar boundary layer prior to turbulent flow transition. Analytical routines are developed which predict boundary layer parameters and polymer wall concentrations for this postulated optimal ejection process or the suboptimal case. Limited verification of the model is made. (Author).