1. Primary instability of a shear-thinning film flow down an incline: experimental study
- Author
-
Valéry Botton, Bülent Güzel, Mohamed Hatem Allouche, H. Ben Hadid, Daniel Henry, Séverine Millet, Simon Dagois-Bohy, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), INSA Euro-Méditerranée, and Institut National des Sciences Appliquées (INSA)
- Subjects
Physics ,Shear thinning ,business.product_category ,Mechanical Engineering ,Reynolds number ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Instability ,010305 fluids & plasmas ,symbols.namesake ,Flow velocity ,Mechanics of Materials ,Free surface ,0103 physical sciences ,symbols ,Newtonian fluid ,Wavenumber ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,Inclined plane ,010306 general physics ,business ,ComputingMilieux_MISCELLANEOUS - Abstract
The main objective of this work is to study experimentally the primary instability of non-Newtonian film flows down an inclined plane. We focus on low-concentration shear-thinning aqueous solutions obeying the Carreau law. The experimental study essentially consists of measuring wavelengths in marginal conditions, which yields the primary stability threshold for a given slope. The experimental results for neutral curves presented in the $(Re,f_{c})$ and $(Re,k)$ planes (where $f_{c}$ is the driving frequency, $k$ is the wavenumber and $Re$ is the Reynolds number) are in good agreement with the numerical results obtained by a resolution of the generalized Orr–Sommerfeld equation. The long-wave asymptotic extension of our results is consistent with former theoretical predictions of the critical Reynolds number. This is the first experimental evidence of the destabilizing effect of the shear-thinning behaviour in comparison with the Newtonian case: the critical Reynolds number is smaller, and the ratio between the critical wave celerity and the flow velocity at the free surface is larger.
- Published
- 2017