In vivo evidence of blood flow slippage: failure of the no-slip boundary condition assumption

TL;DR

This study provides the first in vivo evidence that blood exhibits slip at vessel walls, challenging the fundamental no-slip boundary condition assumption in cardiovascular fluid dynamics.

Contribution

It demonstrates that blood can slip at vessel walls in vivo, which has significant implications for cardiovascular modeling and understanding blood flow dynamics.

Findings

Blood wall velocities are 30-80% of luminal velocity.

First in vivo evidence of blood slip at vessel walls.

Challenges the no-slip boundary condition assumption.

Abstract

The assumption that blood adheres to vessel walls, the ``no-slip'' boundary condition, is an essential premise of cardiovascular fluid dynamics. Yet, whether it holds true \emph{in vivo} has not been established. Using 4D flow magnetic resonance imaging of the human thoracic aorta and modeling blood as a Navier--Stokes fluid, we quantify the velocity of blood at the wall. We find tangential wall velocities of about 30--80\% of the mean luminal velocity, providing clear evidence of blood slippage. To our knowledge, this is the first demonstration that the no-slip condition does not apply to blood flow \emph{in vivo}. This finding challenges a fundamental assumption in cardiovascular modeling and directly affects key blood flow characteristics such as pressure drop, vorticity, wall shear stress, and energy dissipation, all of which play important roles across a wide range of cardiovascular conditions.