Hydrodynamic Transport Phenomena Research Articles

Microfluidic Transport in Ternary Liquid Layers Due to Sinusoidal Thermocapillary Actuation

Abstract The large-scale applicability of the micro- and nanofluidic devices demands continuous technological advancements in the transport mechanisms, especially to promptly mix the analytes and reagents at such a small scale. To this end, thermocapillarity-induced Marangoni hydrodynamics of three-layered, immiscible fluid streams in a microchannel is analytically explored. The system is exposed to periodic and sinusoidal thermal stimuli, and a theoretical framework is presented. The diffusion of the periodic thermal stimuli across and along the fluidic interfaces creates axial surface tension gradients, which induce vortical motion of the participating fluids within the microconduit. We show that depending on the physical parameters of the three participating fluids, such vortex patterns may be fine-tuned and controlled to obtain desired transport behavior. An analytical solution for the thermal and the hydrodynamic transport phenomena is obtained by solving the momentum and energy conservation equations under the umbrella of creeping flow characteristics (very low Reynolds and thermal Marangoni numbers), and nearly undeformed fluid interfaces (negligibly small Capillary number). The approximate profiles of the deformed interfaces are also quantified theoretically to justify the assumption of flat and undeformed interfaces. The independent influence of crucial thermophysical properties, the microchannel system parameters, and features of the applied thermal stimuli are shown in detail for a fixed combination of other parameters.

Anomalous hydrodynamic transport in interacting noncentrosymmetric metals

In highly conductive metals with sufficiently strong momentum-conserving scattering, the electron momentum is regarded as a long-lived quantity, whose dynamics is described by an emergent hydrodynamic theory. In this paper, we develop an electron hydrodynamic theory for noncentrosymmetric metals, where a novel class of electron fluids is realized by lowering crystal symmetries and the resulting geometrical effects. The obtained hydrodynamic equation suggests a nontrivial analogy between electron fluids in noncentrosymmetric metals and chiral fluids in vacuum, and predicts novel hydrodynamic transport phenomena, that is, asymmetric Poiseuille flow and anomalous edge current. Our theory also gives a hydrodynamic description of the counterpart of various anomalous transport phenomena such as the quantum nonlinear Hall effect. Furthermore, we give a symmetry consideration on the hydrodynamic equation and propose several experimental setups to realize such anomalous hydrodynamic transport in the existing hydrodynamic materials, including bilayer graphene and Weyl semimetals.

Environmental Flow Assessment of River Ganga - Importance of Habitat Analysis as a Means to Understand Hydrodynamic Imperatives for a Sustainable Ganga Biodiversity

Environmental-flow (e-flow) assessment is still at a rudimentary level in India. Among such assessment studies that have been undertaken for the Ganga River Basin, a large fraction is based on the use of simple, less robust methods where ecology has not received due attention. Owing to the ecological importance of the river, we propose the use of habitat analysis methods for assessing e-flows. Studies incorporating knowledge of river hydrology and hydrodynamic transport phenomena coupled with a knowledge of ecological preferences of indigenous species can provide robust and more realistic solutions. Limitations and difficulties in using these methodologies need to be documented and, hopefully, with their resolution.

Highly discretized dynamics

The efforts in the last ten years or so to find a particle dynamics, wherein, the spatial coordinates are confined to lattice positions and the velocity coordinates to a few speeds, have unfortunately failed. It was hoped to duplicate the success of the Ising model, which would have allowed, if not for an analytic treatment, at least much more efficient computational methods to deal with hydrodynamic transport phenomena, particularly turbulence. The next course of action, in view of this failure, will be discussed after the reasons for the failure are outlined.