Álvaro Meseguer, professor d'Enginyeria Física, ha publicat un PRL junt amb altres investigadors

Álvaro Meseguer, professor del Grau en Enginyeria Física, junt amb altres investigadors, ha publicat un article al Physical Review Letters (PRL) titulat Subcritical Equilibria in Taylor-Couette Flow.

Short review

The origin of turbulence often follows the destabilisation of the laminar flow due to shear, centrifugal or thermal-convective, among other, mechanisms. There are cases, however, in which turbulence arises without an intervening instability of the laminar flow. These flows, which are sensitive to finite amplitude disturbances, are said to undergo subcritical transition, and they have puzzled generations of scientists and engineers since Osborne Reynolds first identified the phenomenon over a century ago.

The latest developments in the field of subcritical transition to turbulence have come from the treatment of the equations governing fluid motion as describing an infinite-dimensional dynamical system. All the machinery of nonlinear dynamics, including bifurcation and deterministic chaos theory, is now deployed to try and cast light on the long standing mystery of fluid flow going disordered unexpectedly and for no apparent reason. One of the fundamental elements of this new understanding of transition is the numerical quest for nonlinear unstable solutions of the equations. These solutions, which typically take the form of stationary, travelling or pulsating waves, undergo then a series of transitions to flows of ever growing complexity that result in turbulence.

The nonlinear fluid dynamics research group of the Universitat Politècnica de Catalunya is very active in the search and study of such solutions in a number of fundamental fluid flows using state-of -the-art topnotch numerical methods. It keeps ongoing collaboration with a number of international research groups working in the field. One of these collaborations has recently resulted in the discovery (Phys. Rev. Lett. 112 (18), 184502; on the cover) of the first subcritical nonlinear wave that gathers all the ingredients to be a precursor to subcritical turbulence in Taylor-Couette flow, the flow between two differentially rotating concentric cylinders. The figure shows a scheme of the flow setup and a visualisation of the wave found. Its finding and analysis gets us one step closer to the understanding of subcritical transition.