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

Seudoartrosis congénita de clavícula asociada a síndrome del estrecho torácico superior: presentación de un caso y revisión de la literatura

La seudoartrosis congénita de clavícula es una patología muy poco frecuente. Generalmente afecta al lado derecho y es asintomática. Su tratamiento quirúrgico sólo está indicado cuando produce una alteración estética en forma de tumoración. Presentamos un caso de seudoartrosis congénita de clavícula asociada a un síndrome de estrecho torácico superior, tratado con la resección de la primera costilla y la sección de la inserción del músculo escaleno anterior en la misma.Congenital pseudoartrosis of the clavicle is a very little frecuent patology. Usually it affects the right side and is asymptomathic. Surgery is only indicated for cosmetic reasons. We report a case of congenital pseudoarthrosis of the clavicle associated with vascular thoracic outlet syndrome treated with excision of the first rib and section of inserción of the scalenus anticus muscle on the first rib

Chemical weathering of the volcanic soils of Isla Santa Cruz (Galápagos Islands, Ecuador)

We present a study on weathering of volcanic soils using 43 profiles (131 horizons) sampled in Santa Cruz Island (Galapagos Islands). Several weathering indices, based on chemical composition, are used. Since the geological material is highly homogeneous the intensity of weathering is mostly related to climatic conditions controlled by topography. There is a gradient of increasing weathering from the arid conditions predominant in the coast to elevations of 400-500 m a.s.l. where much more humid conditions prevail

Revisión de la sucesión de la Sierra de la Zarzuela: último registro del Ediacárico-¿Fortuniense inferior? del Gran Anticlinorio Extremeño central, Zona Centroibérica meridional, Macizo Ibérico, España

In the southern Central Iberian Zone, unconformably lying on the Cadomian folded Lower Alcudian-Domo Extremeño Supergroup the most complete succession of late Ediacaran rocks crops out at the Sierra de la Zarzuela syncline. The purpose of this contribution is to study and redefine a regional lithostratigraphic framework for the “Upper Alcudian” rocks of this area related to the Ibor Group.En la Zona Centroibérica meridional se reconoce la sucesión más completa de rocas del Ediacárico tardío que afloran en el sinclinal de la Sierra de la Zarzuela, discordantes sobre el Supergroup del Alcudiense inferior-Domo Extremeño. El objetivo de esta contribución es estudiar y redefinir un marco litoestratigráfico regional para las rocas del “Alcudiense inferior” de este área relacionada con el Grupo de Ibor

Hydroelastic effects during the fast lifting of a disc from a water surface

Here we report the results of an experimental study where we measure the hydrodynamic force acting on a plate which is lifted from a water surface, suddenly starting to move upwards with an acceleration much larger than gravity. Our work focuses on the early stage of the plate motion, when the hydrodynamic suction forces due to the liquid inertia are the most relevant ones. Besides the force, we measure as well the acceleration at the centre of the plate and the time evolution of the wetted area. The results of this study show that, at very early stages, the hydrodynamic force can be estimated by a simple extension of the linear exit theory by Korobkin (J. Fluid Mech., vol. 737, 2013, pp. 368–386), which incorporates an added mass to the body dynamics. However, at longer times, the measured acceleration decays even though the applied external force continues to increase. Moreover, high-speed recordings of the disc displacement and the radius of the wetted area reveal that the latter does not change before the disc acceleration reaches its maximum value. We show in this paper that these phenomena are caused by the elastic deflection of the disc during the initial transient stage of water exit. We present a linearised model of water exit that accounts for the elastic behaviour of the lifted body. The results obtained with this new model agree fairly well with the experimental results

Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N₂, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, k_Cl&plusmn;2&sigma; (in units of cm³ molecule^&minus;1 s^&minus;1) were: trans-2-pentenal (1.31&plusmn;0.19)&times;10^&minus;10; trans-2-hexenal (1.92&plusmn;0.22)&times;10^&minus;10; trans-2-heptenal (2.40&plusmn;0.29)&times;10^&minus;10; n-pentanal (2.56&plusmn;0.27)&times;10^&minus;10; n-hexanal (2.88&plusmn;0.37)&times;10^&minus;10; n-heptanal (3.00&plusmn;0.34)&times;10^&minus;10. <P style='line-height: 20px;'> Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO₃ radicals

The effect of radial inertia on flow localization in ductile rods subjected to dynamic extension

The objective of this work is to investigate the influence of radial inertia on the flow localization in ductile rods subjected to dynamic extension. Using the theory of a straight Cosserat rod which includes normal cross-sectional extension it is possible to obtain an exact solution for nonlinear uniform extension of a rigid-plastic material using a functional form of the yield stress that models the effect of the more general stress field in the necking region of the rod. Linear stability analysis of this exact nonlinear solution yields equations that generalize the formulation reported in Ref. [1] to include radial stretching and inertia. Examples show the quantitative effect of radial inertia on the stabilization of the localization process and on the determination of the expected length of fragments.This research was partially supported by MB Rubin's Gerard Swope Chair in Mechanics. J. A. Rodríguez-Martínez is indebted to the Ministerio de Ciencia e Innovación de España (Project DPI/2011-24068) for the financial support