Newton saw the truth -- on the nature of fluid flow and viscous interaction

TL;DR

This paper challenges the classical viscosity model in fluid dynamics by proposing a slip-based model supported by experiments and differential geometry, leading to new insights in laminar flow and turbulence.

Contribution

It introduces a novel viscous interaction model based on molecular slip, supported by experimental validation and analytical solutions, revising classical flow theory.

Findings

Experimental data support the slip viscosity model.

Analytical solutions match Newton's ideal experiment results.

Differences in flow solutions can distinguish viscosity models.

Abstract

The viscous interaction of fluid is understood as the response to deformation, which is proportional to the strain rate. This model has gradually become the standard since Stokes, and has become the basis of the classical flow theory, namely the Navier-Stokes (N-S) equations. However, it has never been accurately verified in the curved laminar flow. Here, a distinctive unambiguous simple experiment is designed to falsify the viscosity model of deformation, and instead a new model is proposed, that is, the viscous friction originates from the slip of fluid layering at molecular scale. Though Newton contributed the initial idea of slip viscosity, the new model cannot be formulated without the help of modern differential geometry. From the new model, the analytical solution of laminar Taylor-Couette (T-C) flow between two concentric cylinders can reproduce the result of the ideal experiment proposed by Newton as the outer cylinder being infinite, which was once considered a mistake of Newton. A significant difference with the solution of the N-S equations when the outer cylinder is relatively large can be used to distinguish the viscosity models, even for the simplest case with both cylinders rotating with the same angular velocity. The accurate measurement data by the LDA support the slip model, and the consequent flow theory inevitably leads to a new vision in turbulence research.