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Gravity-driven thermoviscous liquid film down a heated or cooled vertical cylinder

Sana Khanum and Naveen Tiwari
Phys. Rev. Fluids 5, 094005 – Published 18 September 2020

Abstract

Stability analysis of gravity-driven flow of a thermoviscous liquid on the exterior surface of a uniformly heated or cooled vertical cylinder is presented. The film evolution model derived using lubrication approximation consists of four dimensionless groups, namely, Marangoni number, Biot number, Bond number, and thermoviscosity number. The viscosity of the liquid is modeled as an exponentially varying function of temperature. The thermocapillary stress significantly affects the Rayleigh-Plateau instability for flow over a nonisothermal cylinder with intricate dependence on various parameters involved. For the temporally unstable system, spatiotemporal stability analysis is performed to delineate the parameter regions for convectively and absolutely unstable systems. Brigg's criterion is employed and the critical value of a composite parameter β is evaluated to study the transition from convective to absolute instability. A proper rescaling of the dispersion relation shows that the condition on the composite parameter is β<1.507 for the existence of absolute instability, which is consistent with an earlier work on isothermal flows. Further, an expression is found for the critical composite Marangoni number beyond which the film is always absolutely unstable independent of the Bond number. This critical value is shown to be an increasing function of thermoviscosity number. Results from the nonlinear simulations are in agreement with the predictions of the linear temporal and spatiotemporal analyses.

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  • Received 20 May 2020
  • Accepted 11 August 2020

DOI:https://doi.org/10.1103/PhysRevFluids.5.094005

©2020 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Sana Khanum1 and Naveen Tiwari2,*

  • 1Department of Chemical Engineering, Purdue University, Indiana 47907-2100, USA
  • 2Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India

  • *Corresponding author: naveent@iitk.ac.in

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Issue

Vol. 5, Iss. 9 — September 2020

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