Simulating polymer drag reduction using a modified mixing length in zero pressure gradient

Abstract

It is known that a small concentration of polymer introduced to the boundary layer can produce a significant drag reduction for liquid flows. This effect has been extensively studied for internal flow and polymer injection in external flow. More recently, select external flow research has focused on drag reduction for ships where polymer is introduced by ablation of surface coatings. The present article introduces a simple yet effective model for simulating polymers in the boundary layer. That is a step toward a practical methodology for simulating the effect of ablative polymer paint. For the case of zero pressure gradient boundary layers, measured polymer drag reduction can be closely reproduced, to less than 10% error, by modifying the empirical von Kármán and van Driest constants in the simple mixing length turbulence model. Potential avenues for implementation in standard commercially available computational fluid dynamics solvers are explored.