Low Reynolds number friction reduction with polymers and textures

Jonathon K. Schuh, Randy H. Ewoldt

Research output: Contribution to journalArticlepeer-review

Abstract

We present an experimental investigation with surface textures and a Non-Newtonian polymer solution (polyisobutylene in oil) to determine synergistic effects on laminar hydrodynamic friction reduction. Gap controlled experiments were performed on a custom parallel disk tribo-rheometer to systematically vary the Reynolds number (0.1–16), Weissenberg number (0.1–30), and Deborah number (0.005–0.5) in bi-directional sliding motion with five different texture geometries: cylindrical holes with varying asymmetric angle β. Cavitation effects are not present, thus normal force is produced solely by the textures and the lubricant rheology. Contrary to Newtonian fluids without cavitation, the normal force is positive, independent of the direction of motion when shear normal forces dominate purely viscous effects. We observe that the normal thrust can be larger than a simple superposition of forces due to viscous hydrodynamics and shear normal stresses. This synergistic coupling between the asymmetric textures and the polymer solution (at high Wi) produces an optimal angle of texture asymmetry β for dramatically decreasing the effective coefficient of friction compared to the Newtonian oil without polymer.

Original languageEnglish (US)
Article number104167
JournalJournal of Non-Newtonian Fluid Mechanics
Volume273
DOIs
StatePublished - Nov 2019

Keywords

  • Full film lubrication
  • Gap-control
  • Non-Newtonian fluids
  • Surface textures

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering
  • Applied Mathematics

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