Modification of Near-Wall, High-Reynolds Number Velocity Profiles With Polymer Solution

Oklahoma State University, Stillwater OK

Investigators

Abstract

PI: Elbing, Brian Proposal Number: 1604978 The addition of a very small amount of polymers to a fluid can result in a dramatic reduction of friction for turbulent flows. It is proposed to conduct state-of-the-art experiments in a newly built facility to obtain an extensive amount of detailed data for the process at different conditions, and then develop a predictive model for the polymer effects on the fluid velocity. Drag reduction with polymers can be used to save energy for fluid transportation over long distances, e.g., for oil pipelines. It can also reduce energy costs for ocean faring vehicles (ships and submarines). The proposed research is to investigate how drag-reducing polymer solutions modify the near-wall region of a high-Reynolds number turbulent boundary layer. While this has been thought to be understood for decades, recent numerical and experimental data show significant deviation from the classical view. Available data shows a non-universal behavior when the drag reduction is above 40%, which can only be partially explained by a Reynolds number effect. Consequently, the behavior must be dependent on polymer properties. Thus, this project will focus on characterizing the near-wall region at various values of drag reduction, Reynolds number and polymer properties (i.e., Weissenberg number, viscosity ratio, and length ratio). The first objective is to perform this characterization in a polymer ocean to eliminate the influence of a non-homogeneous polymer concentration field. Then testing will be repeated with polymer injection to assess the sensitivity of the profiles to the homogeneity of the concentration field. Finally, the ultimate profile, an empirically derived upper limit for the velocity shift, will be reexamined in both a polymer ocean and with polymer injection to determine the validity of numerical and experimental observations that the profile is not logarithmic. It will also be examined under what conditions this profile can actually be exceeded. In addition to graduate and undergraduate student participation, high-school students will be engaged in research through the PI's involvement with the job-shadowing component of Oklahoma State University's Upward Bound program, which is focused on low-income and/or first generation high school students. Each year, up to 3 of these students would work with the PI for 6 weeks.