Formation of corner waves in the wake of a partially submerged bluff body

We study theoretically and numerically the downstream flow near the corner of a bluff body partially submerged at a deadrise depth Δh into a uniform stream of velocity U, in the presence of gravity, g. When the Froude number, Fr=U/√gΔh, is large, a three-dimensional steady plunging wave, which is referred to as a corner wave, forms near the corner, developing downstream in a similar way to a two-dimensional plunging wave evolving in time. We have performed an asymptotic analysis of the flow near this corner to describe the wave's initial evolution and to clarify the physical mechanism that leads to its formation. Using the two-dimensions-plus-time approximation, the problem reduces to one similar to dam-break flow with a wet bed in front of the dam. The analysis shows that, at leading order, the problem admits a self-similar formulation when the size of the wave is small compared with the height difference Δh. The essential feature of the self-similar solution is the formation of a mushroom-shaped jet from which two smaller lateral jets stem. However, numerical simulations show that this self-similar solution is questionable from the physical point of view, as the two lateral jets plunge onto the free surface, leading to a self-intersecting flow. The physical mechanism leading to the formation of the mushroom-shaped structure is discussed

Considerations on bubble fragmentation models

n this paper we describe the restrictions that the probability density function (p.d.f.) of the size of particles resulting from the rupture of a drop or bubble must satisfy. Using conservation of volume, we show that when a particle of diameter, D0, breaks into exactly two fragments of sizes D and D2 = (D30−D3)1/3 respectively, the resulting p.d.f., f(D; D0), must satisfy a symmetry relation given by D22 f(D; D0) = D2 f(D2; D0), which does not depend on the nature of the underlying fragmentation process. In general, for an arbitrary number of resulting particles, m(D0), we determine that the daughter p.d.f. should satisfy the conservation of volume condition given by m(D0) ∫0D0 (D/D0)3 f(D; D0) dD = 1. A detailed analysis of some contemporary fragmentation models shows that they may not exhibit the required conservation of volume condition if they are not adequately formulated. Furthermore, we also analyse several models proposed in the literature for the breakup frequency of drops or bubbles based on different principles, g(ϵ, D0). Although, most of the models are formulated in terms of the particle size D0 and the dissipation rate of turbulent kinetic energy, ϵ, and apparently provide different results, we show here that they are nearly identical when expressed in dimensionless form in terms of the Weber number, g*(Wet) = g(ϵ, D0) D2/30 ϵ−1/3, with Wet ~ ρ ϵ2/3 D05/3/σ, where ρ is the density of the continuous phase and σ the surface tension

Influence of Geographic Location in Concrete Structures

It is very important to consider the geographical location of a building at the time of making their structural test. To do this, in this study we used the known technique of structural test based on the correlation of results between Ultrasonic Velocity (V) and Pressure Resistance (R), obtained from the samples extracted in reinforced concrete structural elements. To analyze the influence of the geographical location of the structure, this paper has classified the buildings studied in terms of their distance from the coast and following the Spanish Code on Structural Concrete, is using a reference distance of 500 meters that allows ordering the cases studied according to the aforementioned distance. As a conclusion, it is safe to say that the structures closest to the coast are more influenced by the environment, which greatly influences the quality of concrete structures

On the breakup of an air bubble injected into a fully developed turbulent flow. Part 2. Size PDF of the resulting daughter bubbles

Based on energy principles, we propose a statistical model to describe the bubble size probability density function of the daughter bubbles resulting from the shattering of a mother bubble of size D0 immersed in a fully developed turbulent water flow. The model shows that the bubble size p.d.f. depends not only on D0, but also on the value of the dissipation rate of turbulent kinetic energy of the underlying turbulence of the water, [epsilon]. The phenomenological model is simple, yet it predicts detailed experimental measurements of the transient bubble size p.d.f.s performed over a range of bubble sizes and dissipation rates [epsilon] in a very consistent manner. The agreement between the model and the experiments is particularly good for low and moderate bubble turbulent Weber numbers, Wet = [rho][Delta]u2(D0)D0/[sigma] where the assumption of the binary breakup is shown to be consistent with the experimental observations. At larger values of Wet, it was found that the most probable number of daughter bubbles increases and the assumption of tertiary breakup is shown to lead to a better fit of the experimental measurements

Influence of Age in Concrete Structures by Means of Core Testing

The structural test based on the correlation of results between Ultrasonic Velocity (V) and Pressure Resistance (R), obtained from samples extracted in structural elements of reinforced concrete serves as a tool for understanding the quality of the concretes. To analyze the influence of age, it has been used this method of correlation, confirming the better performance of structures aged less than 20 years. For older ages, it is statistically justified the need for intervention, repair – reinforcing based on the results of the test and results of the correlation ultrasonic velocity- compression on concrete testing cores

On the breakup of an air bubble injected into a fully developed turbulent flow. Part 1. Breakup frequency

The transient evolution of the bubble-size probability density functions resulting from the breakup of an air bubble injected into a fully developed turbulent water ow has been measured experimentally using phase Doppler particle sizing (PDPA) and image processing techniques. These measurements were used to determine the breakup frequency of the bubbles as a function of their size and of the critical diameter Dc defined as Dc = 1.26 ([sigma]/[rho])3/5[epsilon][minus sign]2/5, where [epsilon] is the rate of dissipation per unit mass and per unit time of the underlying turbulence. A phenomenological model is proposed showing the existence of two distinct bubble size regimes. For bubbles of sizes comparable to Dc, the breakup frequency is shown to increase as ([sigma]/[rho])[minus sign]2/5[epsilon][minus sign]3/5 [surd radical]D/Dc[minus sign]1, while for large bubbles whose sizes are greater than 1.63Dc, it decreases with the bubble size as [epsilon]1/3D[minus sign]2/3. The model is shown to be in good agreement with measurements performed over a wide range of bubble sizes and turbulence intensitie

La recreación patrimonial en los videojuegos para el uso didáctico en las Ciencias Sociales

Las nuevas tecnologías son parte indisoluble del alumnado de Secundaria y Bachillerato que forma parte de los nativos digitales. En particular los videojuegos se integran en su cultura lúdica. Nos encontramos en la madurez del videojuego y la tendencia por el hiperrealismo en las producciones de alto presupuesto toman el Patrimonio Mundial de referencia para crear y contextualizar sus universos ya sean creativos o históricos. Así tanto en estos como también las desarrolladoras independientes y las propuestas con fin educativo encontramos una vía atractiva e inmersiva que han abordado distintos especialistas en el plano teórico como en el práctico llevándolo a las aulas para la alfabetización digital como la educación patrimonial que gana protagonismo en el currículo educativo. <br /

On the dynamics of buoyant and heavy partióles in a periodic Stuart vortex flow

In this paper, we study the dynamics of small, spherical, rigid particles in a spatially periodic array of Stuart vórtices given by a steady-state solution to the two-dimensional incompressible Euler equation. In the limiting case of dominant viscous drag forces, the motion of the particles is studied analytically by using a perturbation scheme. This approach consists of the analysis of the leading-order term in the expansión of the 'particle path function' <P, which is equal to the stream function evaluated at the instantaneous particle position. It is shown that heavy particles which re-main suspended against gravity all move in a periodic asymptotic trajectory located above the vórtices, while buoyant particles may be trapped by the stable equilibrium points located within the vórtices. In addition, a linear map for <P is derived to describe the short-term evolution of particles moving near the boundary of a vortex. Next, the assumption of dominant viscous drag forces is relaxed, and linear stability analyses are carried out to investígate the equilibrium points of the five-parameter dynamical system governing the motion of the particles. The five parameters are the free-stream Reynolds number, the Stokes number, the fluid-to-particle mass density ratio, the distribution of vorticity in the flow, and a gravitational parameter. For heavy particles, the equilibrium points, when they exist, are found to be unstable. In the case of buoyant particles, a pair of stable and unstable equilibrium points exist simultaneously, and undergo a saddle-node bifurcation when a certain parameter of the dynamical system is varied. Finally, a computational study is also carried out by integrating the dynamical system numerically. It is found that the analytical and computational results are in agreement, provided the viscous drag forces are large. The computational study covers a more general regime in which the viscous drag forces are not necessarily dominant, and the effects of the various parametric inputs on the dynamics of buoyant particles are investigated

El ladrillo de Valentín. Una tradición en vanguardia

Valentín es una pequeña pedanía muy cercana a la localidad de Calasparra, situada en el Noroeste de la Región de Murcia, con baja densidad de población, la mayor parte de ella dedicada a la fabricación de un tipo especial de cerámica. Se trata de: ladrillo cerámico macizo, teja curva y loseta de pavimento, fabricados por métodos tradicionales, con arcillas de la zona y que se destina principalmente a su uso en fachadas, como ladrillo “cara vista”, en aplacados decorativos, pavimentos rústicos y uso en Restauración. Se pretende mediante esta investigación profundizar en el origen, características del material, técnicas de fabricación y su disposición en obra. Para concluir destacar que se trata de un producto que aúna las cualidades de un material tradicional con gran potencial de uso en la actualidad

Vorticity dynamics in three-dimensional pulsating co-flowing jet diffusion flames

The vorticity dynamics in the near field of laminar (Re = 103) co-flowing jets subjected to the single or combined effeets of axial and azimuthal forcing is analyzed. It is shown that the interaction of the three-dimensional vortex structure resulting from the growth of the two and three-dimensional instabilities may result in large changes in the entrainment and mixing characteristics of the jet. For each azimuthal forcing, and for a fixed velocity ratio between the inner and outer jet, we show the existence of several instability modes leading to a pattern of lateral ejections of closed vortex loops. These modes and their topological changes are analyzed in view of the three-dimensional inviscid induction of the two concentric array of vortex rings emanating from the j e t s exit nozzle. For the case of methane-air diffusion flames, fiow visualizations revealed the existence of qualitatively similar patterns of closed fíame cells and fingers