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An experimental study of the impact of glycerol/water drops onto a dry glass surface at Reynolds and Weber numbers around the splashing/deposition threshold is presented. Some new observed phenomena that may shed further light on the mechanisms underlying air bubble entrainment and splashing for high-viscosity liquids are presented and discussed. The experiments were recorded with a high-speed camera using two complementary lighting setups that enhance the visualization of different features of the air entrainment phenomena: backlighting with a light diffuser and oblique lighting without diffuser. Besides the ring of micro-bubbles surrounding the central entrapped bubble and the cloud of bubbles entrained as a result of the interaction between a levitated thin film and the solid surface, which have been studied by other authors in previous works, a second ring of micro-bubbles that delimits the outer cloud of bubbles has been detected in our investigation. Attention is mainly focused on analyzing the dependency of the behavior of the two rings of microbubbles on the drop impact velocity, the ranges of the relevant dimensionless numbers in which the rings are formed and the existence, in certain impact conditions, of an abrupt increase in the size of the second ring, which substantially modifies the impact outcome.

One of the most important problems encountered in die-casting processes is porosity due to air entrapment in the molten metal during the injection process. The aim of this work is to study experimentally and numerically the different air entrapment phenomena that may take place in the early stages of the filling of a vertical die cavity with a rectangular shape for operating conditions typically used in low and medium-pressure die-casting processes. Special attention is given to determining the influence of the gravitational forces on the flow pattern. Numerical simulation of the flow in the die cavity is carried out for the liquid phase using a commercial computational fluid dynamics (CFD) code (FLOW-3D) based on the solution algorithm-volume of fluid (SOLA-VOF) approach to solve the coupling between the momentum and mass conservation equations and to treat the free-surface, while the amount of air evacuated through vents is calculated by using an unsteady one-dimensional adiabatic model that retains friction effects. The main characteristics of the flow at the early instants of the die cavity filling are analyzed for different operating conditions, and the different flow patterns are summarized in a map as a function of the Reynolds and Froude numbers. Also, filling visualization experiments are carried out on a test bench using water as working fluid in a transparent die model and a high-speed camera. The numerical and experimental results obtained for the free-surface profile evolution are compared for different inlet velocities of the fluid and the viability of the numerical tools used to predict the final amount of trapped air in the die cavity is discussed.

El Altiplano del Titicaca conserva una abundante variedad de restos de las culturas precolombinas, tales como las “llallahuas” o habitaciones primitivas hechas de puramente piedra como las que todavía se ven en Tancatenca y la isla de Taquilam, las “chacas” especie de altaros en las cumbres de algunos cerros donde ofrecen sus sacrificios y ofrendas a la tierra y al sol; los “cachis” o cuarteles, los “pucaras”, las “chullpas”, etc., que por la premura del tiempo no ha sido posible traer estudios a la consideración de la Mesa Redonda, pero sería imperdonable dejar de dar siquiera una somera noticia de las “pinturas rupestres” de las cuevas de Pizacoma, descubiertas por el arqueólogo Dr. José María Franco Inojosa que vive en Juli.

A graded-adaptive grid projection method to solve the Navier-Stokes equations for incompressible interfacial flows characterized by large density ratios is presented. The numerical model is similar to the one we proposed in [7] and extended to 3D problems in [8]. The free surface is described using a level set method. A Godunov-type method and a Crank-Nicholson temporal discretization scheme are used to solve the advection equation of the level set function and to update of the momentum equation. The reinitialization procedure of the distance function is based on solving a hyperbolic equation to steady state using third-order Runge-Kutta and fifth-order WENO schemes. The conservation equations are discretized on a rectangular adaptive grid with an octree data structure and the pressure stored at the grid cell vertices. In order to avoid spurious pressure oscillations, the velocity components are stored at the cell edges. This new storage scheme combines the advantages of vertex-based schemes, in which the nodes where the pressure is stored are aligned, and cell center-based schemes, which avoid pressure-velocity coupling problems. The numerical model incorporates a continuous surface tension model based on the balanced-force algorithm proposed in [6]. A special treatment of T-nodes (nodes located at vertices, edges or faces of cells belonging to two different refinement levels) is proposed that considerably improves the efficiency of the method. Several tests in two and three dimensions have been carried out to assess the accuracy and efficiency of the proposed method. In this work we present some numerical results for a 3D kinematic test, which are compared with those obtained by other authors. We also present results for the impact of a drop of water onto a liquid surface, which are compared with experimental visualization results.

La información financiera resulta incompleta para comprender la realidad de las empresas y establecer su verdadero valor. Los inversores y otros grupos interesados en la información corporativa toman, cada vez más, sus decisiones basándose no solo en la información financiera, sino también en la información no financiera que tiene en cuenta aspectos sociales, medioambientales y de gobernanza. La divulgación de este tipo de información por parte de las empresas, conjuntamente con las previsiones de futuro, los riesgos a que se ven sometidas y la forma de gestionarlos, incrementarán la credibilidad y la reputación de las organizaciones. La Unión Europea, tomando conciencia de esta realidad, ha aprobado la Directiva 2014/95/UE, sobre divulgación de información no financiera e información sobre diversidad, con el fin de incluir este tipo de información en las cuentas anuales de las grandes empresas. En este artículo examinamos esta nueva directiva comunitaria y, avanzando un paso más, la analizamos considerando sus interrelaciones con la nueva corriente internacional sobre información integrada, que aboga por la creación de un nuevo paradigma orientado a la divulgación de la información corporativa a través de un informe único en el que se integre toda la información de las organizaciones, apoyado en el uso de nuevas herramientas tecnológicas.

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