Gravity Force in Capillary Flow Through Open Channels

Certain conditions of superficial properties can provoke spontaneous movement of liquids at corners such as liquid filaments. The understanding of this type of fluid dynamics phenomena is very important in many areas, for example, oil recovery or design of gathering systems of condensed fluids with capillary forces. In previous studies, several models were developed for formation and advancing of filaments at horizontal corners neglecting the gravity force. The objective of this investigation was to provide a mathematical tool to estimate the influence of gravity and to establish a clear approach for taking this effect into account or not. The proposed model is developed from a differential equation applied to an open corner for Poiseuille flow. It provides good agreement with experimental values with a maximum deviation of 3.3%.     

Toward the border between neural and Markovian paradigms

A new tendency in the design of modern signal processing methods is the creation of hybrid algorithms. This paper gives an overview of different signal processing algorithms situated halfway between Markovian and neural paradigms. A new systematic way to classify these algorithms is proposed. Four specific classes of models are described. The first one is made up of algorithms based upon either one of the two paradigms, but including some parts of the other one. The second class includes algorithms proposing a parallel or sequential cooperation of two independent Markovian and neural parts. The third class tends to show Markov models (MMs) as a special case of neural networks (NNs), or conversely NNs as a special case of MMs. These algorithms concentrate mainly on bringing together respective learning methods. The fourth class of algorithms are hybrids, neither purely Markovian nor neural. They can be seen as belonging to a more general class of models, presenting features from both paradigms. The first two classes essentially include models with structural modifications, while two later classes propose algorithmic modifications. For the sake of clarity, only main mathematical formulas are given. Specific applications are intentionally avoided to give a wider view of the subject. The references provide more details for interested readers.     

Visualization of liquid bridge rupture due to flow induced by corner effects

A high-speed visualization of the phenomenon of rupture of liquid bridges placed in a square cross-section capillary tube was done for three different hydrocarbons (n-Decane, iso-Octane and Decyl-alcohol). The process of rupture could be visualized from side and front views. This technique permitted to observe that the break-up of the bridge was caused by the draining of the liquid through the liquid filaments that were formed at the corners. The rupture of the interface occurred smoothly without any appreciable perturbation on the free surface, starting with a small hole that grows up until the interface splits in four parts. This rupture is strongly determined by geometric and surface properties, such as contact and geometrical angles.