Dive into the latest issue of Fluid Dynamics & Materials Processing (FDMP)
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Dive into the latest issue of Fluid Dynamics & Materials Processing (FDMP) where cutting-edge research explores the intricate dance of forces in both micro and macro realms. This issue features studies on complex flows in microchannels, smart phase transitions in bot swarms, and the impactful role of sulfate ions in crude oil desorption from carbonate rocks. Below are the highlights of these fascinating investigations.
Elena Mosheva, Ivan Krasnyakov
Continuous-flow microchannels are widely employed for synthesizing various materials, including nanoparticles, polymers, and metal-organic frameworks (MOFs), to name a few. Microsystem technology allows precise control over reaction parameters, resulting in purer, more uniform, and structurally stable products due to more effective mass transfer manipulation. However, continuous-flow synthesis processes may be accompanied by the emergence of spatial convective structures initiating convective flows. On the one hand, convection can accelerate reactions by intensifying mass transfer. On the other hand, it may lead to non-uniformity in the final product or defects, especially in MOF microcrystal synthesis. The ability to distinguish regions of convective and diffusive mass transfer may be the key to performing higher-quality reactions and obtaining purer products. In this study, we investigate, for the first time, the possibility of using the information complexity measure as a criterion for assessing the intensity of mass transfer in microchannels, considering both spatial and temporal non-uniformities of liquid’s distributions resulting from convection formation. We calculate the complexity using shearlet transform based on a local approach. In contrast to existing methods for calculating complexity, the shearlet transform based approach provides a more detailed representation of local heterogeneities. Our analysis involves experimental images illustrating the mixing process of two non-reactive liquids in a Y-type continuous-flow microchannel under conditions of double-diffusive convection formation. The obtained complexity fields characterize the mixing process and structure formation, revealing variations in mass transfer intensity along the microchannel. We compare the results with cases of liquid mixing via a pure diffusive mechanism. Upon analysis, it was revealed that the complexity measure exhibits sensitivity to variations in the type of mass transfer, establishing its feasibility as an indirect criterion for assessing mass transfer intensity. The method presented can extend beyond flow analysis, finding application in the controlling of microstructures of various materials (porosity, for instance) or surface defects in metals, optical systems and other materials that hold significant relevance in materials science and engineering.
Dmitry Bratsun, Kirill Kostarev
Swarms of self-organizing bots are becoming important elements in various technical systems, which include the control of bacterial cyborgs in biomedical applications, technologies for creating new metamaterials with internal structure, self-assembly processes of complex supramolecular structures in disordered media, etc. In this work, we theoretically study the effect of sudden fluidization of a dense group of bots, each of which is a source of heat and follows a simple algorithm to move in the direction of the gradient of the global temperature field. We show that, under certain conditions, an aggregate of self-propelled bots can fluidize, which leads to a second-order phase transition. The bots’ program, which forces them to search for the temperature field maximum, acts as an effective buoyancy force. As a consequence, one can observe a sudden macroscopic circulation of bots from the edge of the group to its center and back again, which resembles classical Rayleigh-Benard thermal convection. In the continuum approximation, we have developed a mathematical model of the phenomenon, which reduces to the equation of a self-gravitating porous disk saturated with an incompressible fluid that generates heat. We derive governing equations in the Darcy-Boussinesq approximation and formulate a nonlinear boundary value problem. An exact solution to the linearized problem for infinitesimal perturbations of the base state is obtained, and the critical values of the control parameter for the onset of the bot circulation are calculated. Then we apply weakly nonlinear analysis using the method of multiple time scales. We found that as the number of bots increases, the swarm exhibits increasingly complex patterns of circulation.
Nannan Liu, Hengchen Qi, Hui Xu, Yanfeng He
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Low salinity water containing sulfate ions can significantly alter the surface wettability of carbonate rocks. Nevertheless, the impact of sulfate concentration on the desorption of oil film on the surface of carbonate rock is still unknown. This study examines the variations in the wettability of the surface of carbonate rocks in solutions containing varying amounts of sodium sulfate and pure water. The problem is addressed in the framework of molecular dynamics simulation (Material Studio software) and experiments. The experiment’s findings demonstrate that sodium sulfate can increase the rate at which oil moisture is turned into water moisture. The final contact angle is smaller than that of pure water. The results of the simulations show that many water molecules travel down the water channel under the influence of several powerful forces, including the electrostatic force, the van der Waals force and hydrogen bond, crowding out the oil molecules on the calcite’s surface and causing the oil film to separate. The relative concentration curve of water and oil molecules indicates that the separation rate of the oil film on the surface of calcite increases with the number of sulfate ions.
We hope these studies pique your academic interest and inspire you to delve deeper into these exciting topics. If you're intrigued, explore more of FDMP's cutting-edge research and discover new insights. We warmly invite you to engage with our content, share your thoughts, and contribute to the ongoing discourse in the field!
About the journal
Fluid Dynamics and Materials Processing is an essential reading for all those concerned with complex fluids, multiphase flows and the intersection of fluid dynamics with materials processing and/or with the more general field of engineering optimization. It features original theoretical, computational, and experimental investigations.?
Editor-in-Chief: Prof. Marcello Lappa, University of Strathclyde, UK.
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