Migración de gotas por efecto termocapilar: dependencia cuadrática de la tensión superficial con la temperatura

Se estudia la migración de gotas depositadas sobre una superficie sólida a la cual se le aplica un gradiente uniforme de temperatura. El presente estudio está enfocado en líquidos parcialmente mojantes denominados “self-rewetting”, cuya característica distintiva es la dependencia cuadrática de la tensión superficial con la temperatura. A pesar de que estos líquidos presentan una dinámica compleja, aquí se mostrará como las soluciones obtenidas para líquidos con dependencia lineal en la temperatura pueden adaptarse y ser utilizadas para describir su flujo. A diferencia de los líquidos con tensión superficial lineal en la temperatura, el ancho de las gotas de líquido self-rewetting crece con el tiempo.We study the migration of droplets on a solid surface which is under a uniform temperature gradient. The present article focus on partial wetting fluids which surface tension depends on the squared temperature. These type of liquids, called self-rewetting, show a complex dynamics and here we will compare with those liquids of linear dependence in the temperature. Unlike to the latter ones, the droplet width increases with the time.Fil: Mac Intyre, J. R.. Aalto University; FinlandiaFil: Gomba, Juan Manuel. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Perazzo, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Medicina Traslacional, Trasplante y Bioingeniería. Fundación Favaloro. Instituto de Medicina Traslacional, Trasplante y Bioingeniería; Argentina. Universidad Favaloro; Argentin

X-ray Polarization of the Eastern Lobe of SS 433

How astrophysical systems translate the kinetic energy of bulk motion into the acceleration of particles to very high energies is a pressing question. SS 433 is a microquasar that emits TeV gamma-rays indicating the presence of high-energy particles. A region of hard X-ray emission in the eastern lobe of SS 433 was recently identified as an acceleration site. We observed this region with the Imaging X-ray Polarimetry Explorer and measured a polarization degree in the range 38% to 77%. The high polarization degree indicates the magnetic field has a well ordered component if the X-rays are due to synchrotron emission. The polarization angle is in the range -12 to +10 degrees (east of north) which indicates that the magnetic field is parallel to the jet. Magnetic fields parallel to the bulk flow have also been found in supernova remnants and the jets of powerful radio galaxies. This may be caused by interaction of the flow with the ambient medium.Comment: 8 pages, accepted in the Astrophysical Journal Letter

DRIVEN DROPLETS BY THERMOCAPILLARY EFFECT

We study the migration of droplets on a solid surface which is under a uniform temperature gradient. The present article focus on partial wetting fluids which surface tension depends on the squared temperature. These type of liquids, called self-rewetting, show a complex dynamics and here we will compare with those liquids of linear dependence in the temperature. Unlike to the latter ones, the droplet width increases with the time.Peer reviewe

Multiphase CFD modeling of front propagation in a Hele-Shaw cell featuring a localized constriction

We study a liquid-gas front propagation in a modulated Hele-Shaw cell by means of multiphase computational fluid mechanics based on the three-dimensional Navier-Stokes equations. In the simulations an obstacle that partially fills the gap is placed at the center of the cell, and the liquid-gas interface is driven at a constant velocity. We study the morphological differences between imbibition and drainage for a wide range of capillary numbers, and explore how the wetting properties of the constriction affect the amount of liquid that remains trapped in the draining process. We observe increasing remaining volumes with increasing capillary number and decreasing contact angle. The present CFD implementation for a single mesa defect provides insight into a wide number of practical applications