posted on 2023-12-13, 04:29authored byAaqib
H. Khan, Arijit Ganguli, Mohan Edirisinghe, Sameer V. Dalvi
In recent years, there has been a notable increase in
the interest
toward microfluidic devices for microbubble synthesis. The upsurge
can be primarily attributed to the exceptional control these devices
offer in terms of both the size and the size distribution of microbubbles.
Among various microfluidic devices available, capillary-embedded T-junction
microfluidic (CETM) devices have been extensively used for the synthesis
of microbubbles. One distinguishing feature of CETM devices from conventional
T-junction devices is the existence of a wall at the right-most end,
which causes a backflow of the continuous phase at the mixing zone
during microbubble formation. The back flow at the mixing zone can
have several implications during microbubble formation. It can possibly
affect the local velocity and shearing force at the mixing zone, which
in turn can affect the size and production rate of the microbubbles.
Therefore, in this work, we experimentally and computationally understand
the process of microbubble formation in CETM devices. The process
is modeled using computational fluid dynamics (CFD) with the volume-of-fluid
approach, which solves the Navier–Stokes equations for both
the gas and liquid phases. Three scenarios with a constant liquid
velocity of 0.053 m/s with varying gas velocity and three with a constant
gas velocity of 0.049 m/s at different liquid velocities were explored.
Increase in the liquid and gas velocity during microbubble formation
was found to enhance production rates in both experiments and simulations.
Additionally, the change in microbubble size with the change in liquid
velocity was found to agree closely with the findings of the simulation
with a coefficient of variation of 10%. When plotted against the time
required for microbubble generation, the fluctuations in the pressure
showed recurrent crests and troughs throughout the microbubble formation
process. The understanding of microbubble formation in CETM devices
in the presence of backflow will allow improvement in size reduction
of microbubbles.