• Visita a la Central de Guillena - Alumnos de la asignatura de Máquinas Hidráulicas.

• Grupo 1 •	• Grupo 2 •

• Fichero modelo por el resumen del Workshop:

1. Modelo latex: fichero.
2. Modelo Word: fichero.

• Sesión publica en honor y recuerdo del Académico Numerario Excmo. Sr. D. Antonio Barrero Ripoll

Praninfo de la Universidad de Sevilla, C/ San Fernando, a las 19 h, lunes 28 de marzo 2011.

• Ciclo de conferencias sobre centrales hidroeléctricas

Escuela Técnica Superior de Ingeniería, 11 y 18 de Noviembre de 2010, Campus de la Rábida, Huelva.

• 20-22 de Octubre 2010: The FERMaT - IMPACT - GIMFus Meeting

The FERMaT-IMPACT-GIMFus meeting is the first meeting of the three collaborate fluid mechanics institutions:

• IMPACT, Institute for Energy and Resources.
• FERMaT, Fluides, Energie, Réacteurs, Matériaux et Transferts.
• GIMFus, Grupo de Investigación en Mecánica de Fluidos de la Universidad de Sevilla.

• Seminario E.T.S.I. aula 09 a la 9h30 - 04/05/2010.

Heterogeneous bubble nucleation at surfaces has been notorious
because of its irreproducibility. Here controlled
multi-bubble surface cavitation is achieved by heterogenous nucleation
of bubbles on a hydrophobic surface patterned with micro-cavities.
The expansion of the nuclei in the micro-cavities is triggered by an 
impulsive lowering of the liquid pressure. The procedure allows to 
control and fix the bubble-distance within the bubble cluster. We
observe a perfect quantitative reproducibility of the cavitation
events where the inner bubbles in the two-dimensional cluster are 
shielded by the outer ones, reflected by their later expansion and their delayed collapse. Apart from the final bubble collapse phase 
(when jetting flows
directed towards the cluster's center develop), the bubble dynamics 
can be quantitatively described by an extended Rayleigh-Plesset 
equation, taking pressure modification through the surrounding 
bubbles into account.

When repeating the same experiments with flat polyamide and hydrophobized silicon
surfaces populated with surface nanobubbles (as can be seen through
atomic force microscopy), these nanobubbles do not act as nucleation sites for cavitation bubbles, in contrast to the
expectation. This implies that surface nanobubbles are not just
stable under ambient conditions but also under enormous reduction of
the liquid pressure down to -6MPa. We denote this feature as superstability.

• Seminario E.T.S.I. aula 09 a la 9h30 - 03/05/2010.

Thermally driven turbulence is one of the classical problems in fluid dynamics. The great interest into this problem
originates from the relevance of thermal turbulence in
meteorology, geophysics, oceanograpy, and astrophysics:
The weather in the atmosphere is driven by thermal convection,
convection transports the heat of the earth's interior to its surface, convection drives currents in the ocean.

In the last years we have developed a unifying theory for 
convection in a closed container which is called
Rayleigh-Benard convection. We calculate the heat transfer and
the degree of turbulence from the underlying fluid dynamical equations, as a function of the temperature difference and
the material properties.
This theory is based on a decomposition of the energy dissipation
and the thermal dissipation into a bulk and a boundary layer contribution,
and can account for various recent and often surprising experimental results.

• Seminario E.T.S.I. aula 09 a la 9h30 - 28/04/2010.

In many applications, such as airlifts or bubble columns, bubbles are injected into a liquid to enhance the transfers between a gas and a liquid. The buoyancy-driven motions of the bubbles generate an intense agitation of both phases. Various experimental investigations involving isolated bubbles and homogeneous swarms of rising bubbles allow us to determine the statistical properties of this agitation. On the one hand, the fluctuations of the bubble velocity are controlled by the instability of the individual bubble wakes and therefore weakly depend on the gas volume fraction. On the other hand, the fluctuations of the liquid velocity are almost uncoupled from those of the bubbles and combine two contributions of different natures: the first corresponds to the local spatial inhomogeneities of the flow in the vicinity of the bubbles while the second results from the flow instabilities that develop when the Reynolds number is large enough. Separating these two contributions is a very hard task with moving particles, it becomes however practicable with fixed ones. For that reason, we carried out experimental investigations of the flow trough a random array of spheres, which was shown to produce the same velocity fluctuations as a swarm of rising bubbles. The liquid velocity can thus be decomposed by using both time and spatial averagings. The statistical and spectral description of each contribution makes clear their respective roles in the dynamics of the streamwise and the transversal fluctuations. These two contributions, which have to be account for in the modeling of bubble-induced agitation, also leads to the existence of two distinct mixing mechanisms that will be described in the last part of this talk.

Fig.: Mixing of a fluorescent dye by bubble-induced turbulence.

• Seminario E.T.S.I. aula 09 a la 9h30 - 27/04/2010.

Bubbles are used in several process in water treatment. Flotation is first considered. Bubbles are used to capture particles in suspension in order to clean water. The collision efficency is considered using both experiments in a single bubble flotation column and direct numerical simulations. The effect of the bubble recovering by particle and interface contamination is considered. The second part of the talk is devoted to bubble oxygen transfer. In urban wastewater treatment, the main process to treat nitrogen and organic components of wastewater consist in using fine bubble aeration systems. We focus thants to direct numerical simulations to the effect of bubble deformation on the flux of oxygen at the bubble surface.

• Premio FAMA Universidad de Sevilla - Antonio Barrero Ripoll - 14/04/2010:

Se entrega el Premios FAMAS - Universidad de Sevilla a la trayectoria Investigadora al Profesor Dr. Antonio Barrero Ripoll, por el rector de la Universidad, que tendrá lugar en el Paraninfo de la Universidad (C/. San Fernando, 4).