What is it about?

This paper investigates how fluids moving back and forth inside a horizontal channel can suddenly begin to circulate due to temperature differences. When a fluid is pushed by a pulsating pressure gradient, its friction against the channel walls generates internal heat, a process known as viscous dissipation. If the lower boundary of the channel is insulated and the top is kept at a fixed temperature, this internal heating creates an unstable vertical temperature gradient. We used mathematical models and linear stability analysis to figure out exactly when this combination of fluid friction and buoyancy forces causes the fluid to undergo thermal convection.

Featured Image

Why is it important?

We have proposed a completely new mechanism for the onset of thermal convection that relies on the interaction between a pulsating flow, viscous heating, and buoyancy. Previously, stability analyses of pulsating flows primarily focused on hydrodynamic instabilities, rather than thermal ones driven by internal friction. These findings are particularly relevant for systems involving highly viscous fluids, such as propylene glycol, or flows with low pulsation frequencies. Understanding this behavior is vital for designing better engineering devices and explaining natural phenomena in geophysics and biophysics where pulsating pressure gradients occur.

Perspectives

Collaborating with Michele Celli on this theoretical framework was incredibly rewarding, as it allowed us to push the boundaries of classical fluid mechanics. By restricting our initial stability analysis to the stationary component of the basic state, we managed to tackle a highly complex problem and find a clear mathematical threshold for instability. I am particularly excited that our theoretical threshold for convection is something that can actually be reproduced in a laboratory environment. My hope is that this mathematical foundation will inspire experimentalists to validate our proposed instability mechanism and physically observe these convective cell patterns.

Andrey V Kuznetsov
North Carolina State University

Read the Original

This page is a summary of: A new mechanism for buoyancy driven convection in pulsating viscous flows: A theoretical study, International Journal of Heat and Mass Transfer, March 2018, Elsevier,
DOI: 10.1016/j.ijheatmasstransfer.2017.10.112.
You can read the full text:

Read

Contributors

The following have contributed to this page