Fluidic oscillators (FOs) are used in a variety of applications, including process control and process intensification. Despite the simple design and operation of FOs, the fluid dynamics of FOs exhibit rich complexities. The inherently unstable flow, jet oscillations, and resulting vortices influence mixing and other transport processes. In this work, we computationally investigated the fluid dynamics of a new design of a planar FO with backflow limbs. The design comprised of two symmetric backflow limbs leading to bistable flow. The unsteady flow dynamics, internal recirculation, jet oscillations, secondary flow vortices were computationally studied over a range of inlet Reynolds numbers (2400-12,000). The nature and frequency of the jet oscillations were quantified. The computed jet oscillation frequency was compared with the experimentally measured (using imaging techniques) jet oscillation frequency. The flow model was then used to quantitatively understand mixing, heat transfer, and residence time distribution. The approach and the results presented in this work will provide a basis for designing FO's with desired flow and transport characteristics for various engineering applications.
The
interaction of two impinging liquid jets in a confined impinging
jet reactor (CIJR) is explored. Multiphase flow simulations were performed
using the volume of fluids (VOF) approach to investigate the impingement
dynamics of liquid impinging jets, and single-phase CFD simulations
have been performed to understand the turbulence and the mixing performance
in the system. At identical inlet velocities, the liquid sheet formed
on the impingement axis was found to move toward the liquid jet inlet
of the lesser density fluid until reaching equilibrium. The formation
and transient movement of liquid sheets are characterized for different
jet velocities. An improved reactor geometry is proposed that reduces
the wall effect on sheet formation and wall deposition on discharge
points of jets. Upon breaking away from the impinging film, the two
liquid phases are found to be intertwined in the form of ligaments
and droplets after fragmentation of the sheet, providing a higher
interfacial area. The performance of the novel CIJR device was confirmed
by performing high-throughput continuous antisolvent precipitation.
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