Noticias

Nombramiento APS Fellow del Cat. José Manuel Gordillo

Nuestro compañero y director del grupo, el catedrático
de la Escuela Técnica Superior de
Ingeniería de la Universidad de Sevilla,
José Manuel Gordillo ha sido nombrado
Fellow del APS
(Amercian Physical Society)
por su contribución a la física.

Noticia de la US - Noticia de La Vanguardia

Noticia de la US - Noticia de La Vanguardia

Seminario E.T.S.I. aula 06 a la 12h30 - 14/12/2022

Bursting soap bubbles - does the ambient matter?

Uddalok Sen

Physical Chemistry and Soft Matter, Wageningen University and Research, Wageningen, The Netherlands.

Floating soap bubbles are often a sight to behold, particularly due to the plethora of colors they demonstrate as light gets reflected from the soap film. However, soap bubbles (or films) are inherently ephemeral, and burst soon after they are formed – often to the disappointment of the mesmerized observer. Interestingly, this bursting phenomenon itself is rich in physics, and has fascinated fluid dynamicists for nearly two centuries. Despite the long history of studying this bursting phenomenon, several key questions are still unanswered; in particular, what role, if any, the ambient plays in the physics of bursting. In this talk, I will revisit this age-old problem, with an emphasis on studying the influence of the ambient on the physics of bursting soap bubbles. I will show that high-speed imaging reveals new scalings in the dynamics of bursting films in an ambient, which can be further explained through scaling analysis and numerics. The findings of this talk are not only of fundamental importance, but are also relevant in understanding, and thus mitigating, oil spills in oceans and the spread of respiratory diseases via aerosols.

Algunos artículos de prensa sobre el 11th EFMC

• Sevilla World - Sevilla, foco mundial de los avances en mecánica de fluidos.

• El correo de Andalucia - Entrevista a José Manuel Gordillo, catedrático de Mecánica de Fluidos en la Universidad Hispalense. Es el primer espantilde; ol elegido por la Sociedad Europea de Mecánica para su consejo directivo y organiza en Sevilla, del 13 al 16 de este mes, su congreso científico, nunca celebrado antes en Espantilde; a.

• Universidad de Sevilla - Espantilde; a acoge por primera vez el Congreso Europeo de Mecánica de Fluidos.

• El correo de Andalucia - Entrevista a José Manuel Gordillo, catedrático de Mecánica de Fluidos en la Universidad Hispalense. Es el primer espantilde; ol elegido por la Sociedad Europea de Mecánica para su consejo directivo y organiza en Sevilla, del 13 al 16 de este mes, su congreso científico, nunca celebrado antes en Espantilde; a.

• Universidad de Sevilla - Espantilde; a acoge por primera vez el Congreso Europeo de Mecánica de Fluidos.

Seminario E.T.S.I. aula 08 a la 13h00 - 01/07/2016

Approach, collision and rebound of a sphere onto a textured wall

Thibault Chastel

Pierre et Marie Curie University. Paris, France

During this talk, I will discuss in detail the dynamics of sticking and bouncing of a fluid-immersed solid sphere onto a textured wall at low and moderate Reynolds and Stokes numbers. Using high-frequency interferometric measurements, the dynamics of the sphere is resolved in time and space, before, during and after collision with the wall. In particular, we will see the influence of the textures on the sphere velocity in the near-wall region. The textures consist of square arrays of square-micro pillars. At a given distance from the top of the pillars, the sphere velocity is found to be significantly larger than the corresponding velocity for a smooth solid wall.
In the first part, I will focus on the dynamics at low Reynolds number. A squeeze flow model of two adjacent fluid layers has been developed in the lubrication approximation. In the second part, I will focus on the dynamics at moderate Reynolds when the sphere can either stick or bounce off the textured wall. The critical Stokes number for bouncing is significantly influenced by the geometry of the texture, i.e. the surface fraction and the height of the micro-pillars. A modified Hertz model is developed to take into account the influence of this texture geometry on the collision dynamics. The predicted scaling for the collision penetration depth of the sphere into the textured wall is found to be in good agreement with the experimental measurements.

Nombramiento editor asociado del JFM de Pr. José Manuel Gordillo

Nuestro compañero y director del grupo, el profesor
de la Escuela Técnica Superior de
Ingeniería de la Universidad de Sevilla,
José Manuel Gordillo ha sido nombrado editor asociado
de la revista científica *Journal of Fluid Mechanics*.

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

Surface cavitation on micro- and nanometer scales

Detlef Lohse

University of Twente. The Netherlands

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

Detlef Lohse

University of Twente. The Netherlands

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, oceanography, 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

Dynamics of bubbly flows: agitation and mixing

Frédéric Risso

Institut de Mécanique des Fluides de Toulouse. France

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.

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

Bubbles and water treatment: flotation and oxygen transfer

Dominique Legendre

Institut de Mécanique des Fluides de Toulouse. France

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 efficiency 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.