Publications related to Hydrodynamic stability

Painting Taylor vortices with cellulose nanocrystals: Suspension flow supercritical spectral dynamics

We study the flow stability and spatiotemporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow v ...

Aip Publishing2024

Stability of a liquid layer draining around a horizontal cylinder: Interplay of capillary and gravity forces

François Gallaire, Shahab Eghbali, Simeon Vladimirov Djambov

We study the drainage of a viscous liquid film coating the outside of a solid horizontal cylinder, where gravity acts vertically. We focus on the limit of large Ohnesorge numbers Oh, where inertia is negligible compared to viscous effects. We first study t ...

Amer Physical Soc2024

Liquid film instability of an internally coated horizontal tube

François Gallaire, Edouard Boujo, Yves-Marie François Ducimetière, Shahab Eghbali

We study numerically and theoretically the gravity-driven flow of a viscous liquid film coating the inner side of a horizontal cylindrical tube and surrounding a shear-free dynamically inert gaseous core. The liquid-gas interface is prone to the Rayleigh-P ...

AMER PHYSICAL SOC2023

A weakly nonlinear amplitude equation approach to the bypass transition in the two-dimensional Lamb–Oseen vortex

François Gallaire, Yves-Marie François Ducimetière

We analytically derive an amplitude equation for the weakly nonlinear evolution of the linearly most amplified response of a non-normal dynamical system. The development generalizes the method proposed in Ducimetière et al. (J. Fluid Mech., vol. 947, 2022, ...

Cambridge University Press2023

The effects of Prandtl number on the nonlinear dynamics of Kelvin-Helmholtz instability in two dimensions

Jeremy Peter Parker

It is known that the pitchfork bifurcation of Kelvin-Helmholtz instability occurring at minimum gradient Richardson number Ri(m) similar or equal to 1/4 in viscous stratified shear flows can be subcritical or supercritical depending on the value of the Pra ...

Cambridge University Press2021

Second-order adjoint-based sensitivity for hydrodynamic stability and control

Edouard Boujo

Adjoint-based sensitivity analysis is routinely used today to assess efficiently the effect of open-loop control on the linear stability properties of unstable flows. Sensitivity maps identify regions where small-amplitude control is the most effective, i. ...

Cambridge University Press2021

Evaluation of a Dynamic Transfer Matrix for a Hydraulic Turbine

François Avellan, Andres Müller, Keita Yamamoto

It is well known that hydraulic machines experience various types of flow instabilities causing a negative influence on the system under off-design operations. The transfer matrix method correlating the flow properties in upstream and downstream of hydraul ...

2020

Swirl number based transposition of flow-induced mechanical stresses from reduced scale to full-size Francis turbine runners

François Avellan, Christian Landry, Arthur Tristan Favrel, Keita Yamamoto, Joao Gomes Pereira Junior

At part load conditions, Francis turbines are subject to the emergence of a hydrodynamic instability in their draft tube, referred to as precessing vortex rope. It induces pressure pulsations in the water passages at the precession frequency of the vortex, ...

2020

Response of noise-amplifier flows: From linear control to nonlinear jet breakup

Isha Shukla

Among hydrodynamically unstable flows, the amplifier-flows are characterized by their large amplification potential in presence of external noise. Since amplifiers do not have an intrinsic dynamics, a chosen forcing can be applied to eventually control the ...

EPFL2019

Progress in disruption prevention for ITER

Olivier Sauter, Mengdi Kong, Alessandro Pau, Francesca Maria Poli, Umar Sheikh, Ji Hyun Kim

Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated in recent research worldwide. Recent analysis has identified the current density profile as the main drive ...

IOP Publishing Ltd2019

Bretherton's buoyant bubble

John Martin Kolinski, Wassim Dhaouadi

When a buoyant bubble is inserted into a closed capillary that is slightly smaller than the capillary length, it appears stuck; exactly why this is so is a puzzle that has remained unanswered over the past 50 years. Recent calculations suggest that the bub ...

2019

Pattern formation in thin liquid films: from coating-flow instabilities to microfluidic droplets

Gioele Mariano Nicolò Balestra

Nature and technical applications abound with thin viscous flows, ranging from the lava flow on volcanoes to the lubricating layer around confined bubbles in the microchannels of Lab-on-a-Chip devices. Countless are the examples where coating flows arise i ...

EPFL2018

Predictive control of spiral vortex breakdown

François Avellan, François Gallaire, Simon Pasche

The predictive control of the self-sustained single spiral vortex breakdown mode is addressed in the three-dimensional flow geometry of Ruith et al. (2003) for a constant swirl number S = 1.095. Based on adjoint optimization algorithms, two different contr ...

Cambridge University Press2018

Viscous growth and rebound of a bubble near a rigid surface

François Gallaire, Giacomo Gallino

Motivated by the dynamics of microbubbles near catalytic surfaces in bubble-powered microrockets, we consider theoretically the growth of a free spherical bubble near a flat no-slip surface in a Stokes flow. The flow at the bubble surface is characterised ...

Cambridge University Press2018

Rayleigh-Taylor instability under a spherical substrate

Gioele Mariano Nicolò Balestra, François Gallaire, David Minh-Phuc Nguyen

We investigate the Rayleigh-Taylor instability of a thin viscous film coating the inside of a spherical substrate. The aim of this work is to find and characterize the instability pattern in this spherical geometry. In contrast to the Rayleigh-Taylor insta ...

2018

Fluid dynamic instabilities: theory and application to pattern forming in complex media

François Gallaire, Pierre-Thomas Paul Brun

In this review article, we exemplify the use of stability analysis tools to rationalize pattern formation in complex media. Specifically, we focus on fluid flows, and show how the destabilization of their interface sets the blueprint of the patterns they e ...

Royal Society, The2017

Rayleigh-Taylor instability under an inclined plane

François Gallaire, Gioele Mariano Nicolò Balestra, Pierre-Thomas Paul Brun, Pierre Rieu

We revisit the canonical Rayleigh-Taylor instability and investigate the case of a thin film of fluid upon the underside of an inclined plane. The presence of a natural flow along the plane competes with the conventional droplet forming instability. In par ...

2015

A unified criterion for the centrifugal instabilities of vortices and swirling jets

François Gallaire

Swirling jets and vortices can both be unstable to the centrifugal instability but with a different wavenumber selection: the most unstable perturbations for swirling jets in inviscid fluids have an infinite azimuthal wavenumber, whereas, for vortices, the ...

Cambridge University Press2013

Counterpropagating Rossby waves in confined plane wakes

François Gallaire, Luca Biancofiore

In the present work, we revisit the temporal and the spatio-temporal stability of confined plane wakes under the perspective of the counterpropagating Rossby waves (CRWs). Within the context of broken line velocity profiles, each vorticity discontinuity ca ...

American Institute of Physics2012

Stability of a Double-Diffusive Interface in the Diffusive Convection Regime

Alfred Johny Wüest

In this paper, the authors explore the conditions under which a double-diffusive interface may become unstable. Focus is placed on the case of a cold, freshwater layer above a warm, salty layer [i.e., the diffusive convection (DC) regime]. The "diffusive i ...

Amer Meteorological Soc2012