Numerical simulations were performed for Rayleigh-Taylor (RT) hydrodynamic instabilities when a frontier is present. The frontier formed by the interface between two fluids prevents the free movement of the fingers created by the instability. As a consequence, transversal movements at the rear of the fingers are observed in this area. These movements produce collapse of the fingers (two or more fingers join in one finger) or oscillations in the case that there is no collapse. The transversal velocity of the fingers, the amplitude of the oscillations, and the wave number of the RT instabilities as a function of the Rayleigh number (Ra) were studied near the frontier. We verified numerically that in classical RT instabilities, without a frontier, these lateral movements do not occur; only with a physical frontier, the transversal displacements of the fingers appear. The transverse displacement velocity and the initial wave number increase with Ra. This leads to the collapse of the fingers, diminishing the wave number of the instabilities at the interface. Instead, no significant changes in the amplitude of the oscillations are observed modifying Ra. The numerical results are independent of the type or origin of the frontier (gas-liquid, liquid-liquid, or solid-liquid). The numerical results are in good agreement with the experimental results reported by Binda et al. [Chaos 28, 013107 (2018)]. Based on these results, it was possible to determine the cause of the transverse displacements, which had not been explained until now.

Lateral movements of the fingers in Rayleigh-Taylor hydrodynamic instabilities at the interface between two fluids are studied. We show that transverse movements appear when a physical boundary is present; these phenomena have not been explained until now. The boundary prevents one of the fluids from crossing it. Such frontiers can be buoyancy driven as, for example, the frontier to the passage of a less dense solution through a denser solution or when different aggregation states coexist (liquid and gaseous phases). An experimental study of the lateral movement velocity of the fingers was performed for different Rayleigh numbers (Ra), and when oscillations were detected, their amplitudes were studied. Liquid-liquid (L-L) and gas-liquid (G-L) systems were analysed. Aqueous HCl and Bromocresol Green (sodium salt, NaBCG) solutions were used in L-L experiments, and CO (gas) and aqueous NaOH, NaHCO, and CaCl solutions were employed for the G-L studies. We observed that the lateral movement of the fingers and finger collapses near the interface are more notorious when Ra increases. The consequences of this, for each experience, are a decrease in the number of fingers and an increase in the velocity of the lateral finger movement close to the interface as time evolves. We found that the amplitude of the oscillations did not vary significantly within the considered Ra range. These results have an important implication when determining the wave number of instabilities in an evolving system. The wave number could be strongly diminished if there is a boundary.

The Advection-Diffusion Reaction (ADR) equation appears in many problems in nature. This constitutes a general model that is useful in various scenarios, from porous media to atmospheric processes. Particularly, it is used at the interface between two fluids where different types of instabilities due to surface mobility may appear. Together with the ADR equation, the Darcy-Brinkman model describes the phenomena known as fingering that appear in different contexts. The study of this type of system gains in complexity when the number of chemical species dissolved in both fluids increases. With more solutes, the increasing complexity of this phenomenon generally requires much computational power. To face the need for more computational resources, we build a solver tool based on an Alternating Direction Implicit (ADI) scheme that can be run in Central Processing Unit (CPU) and Graphic Processing Unit (GPU) architectures on any notebook. The implementation is done using the MATLAB platform to compare both versions. It is shown that using the GPU version strongly saves both resources and calculation times.

Este trabajo ha obtenido el 1.er Premio Estudios Financieros 2010 en la modalidad de Trabajo y Seguridad Social. La coyuntura económica que vivimos desde hace dos años ha traído consigo la puesta en duda y revisión no sólo de las estructuras monetarias y financieras existentes, sino también de los regímenes occidentales de relaciones laborales, en especial de aquellos, como el español, en los cuales los efectos de la crisis se han dejado sentir con mayor virulencia. Con su materialización, se ha constatado la urgencia de emprender reformas en el seno de los sistemas productivos, recobrando un excepcional papel el concepto de la flexiseguridad, cuyos ejes de actuación se han considerado como fórmula magistral capaz de remediar todos los males que aquejan el modelo español de relaciones laborales. Tal es así que el recientemente aprobado Real Decreto-Ley 10/2010, de 16 de junio, de medidas urgentes para la reforma del mercado de trabajo, lo ha tomado como una fuente esencial de inspiración. El tema, además de reunir una significación y actualidad máximas, presenta una gran complejidad pues en el camino de las propuestas reformistas ni existe un itinerario único, ni las diferentes proposiciones son mutuamente excluyentes. El desafío está en cómo hacer encajar todas las piezas del puzle para alcanzar cuanto antes el mejor escenario posible. Eso sí, es necesario tener en cuenta que el trabajo no ha podido detenerse en todas y cada una de las caras de esta figura poliédrica, centrando su atención en una serie de elementos bien definidos, aun cuando la diversidad y pluralidad existentes lleven implícitas un tratamiento desigual en cuantos han sido seleccionados.

Como en cada una de las ocasiones precedentes en las que he tenido el gusto de reseñar un estudio de la profesora Susana Rodríguez Escanciano, Catedrática en el área del