The focus of this study is an experimental apparatus that
serves as a model for studying blood flow in a total artificial
lung (TAL), a prototype device intended to serve as a bridge to
lung transplantation or that supports pulmonary function during
the treatment of severe respiratory failure. The TAL consists
of hollow cylindrical fibers that oxygen-rich air flows
through and oxygen-poor blood flows around. Because gas
diffusivity in the TAL is very small, a convection mechanism
dominates the gas transport, which is why we focus on the
velocity around the fibers (modeled as a 0.05-cm-in-diameter
and 5-cm-long cylinder). We designed a low-speed water
tunnel to study the flow mechanism around the cylinder,
across which the flow is generated by a linear actuator that
allows different flow patterns to mimic the flow in a TAL. We
tested the flow in the test section by numerical simulation and
by the particle image velocimetry method to study the flow
profile. The results show a uniform flow near the centerline of
the water tunnel where the cylinder is placed. This decreases
the effects of free-stream turbulence in the shear layers and
reduces the uncertainty in determining the flow patterns
around the cylinder. Knowledge gained from the flow around
one cylinder (fiber) is beneficial for understanding vortex
formation around multiple cylinders. We present a summary
of vortex formation behind a cylinder for Reynolds numbers
(Re) of 1, 3, and 5 and Stokes numbers (Ns) of 0.18 to 0.37;
results show that higher Re and Ns favor vortex formation.
These findings regarding the parameter range for vortex formation
may provide principles for designing artificial lungs to
enhance convective mixing. We anticipate that the pulsatile
flow circuit presented here can be used to mimic the flow not
only in TALs but in other physiological systems.
serves as a model for studying blood flow in a total artificial
lung (TAL), a prototype device intended to serve as a bridge to
lung transplantation or that supports pulmonary function during
the treatment of severe respiratory failure. The TAL consists
of hollow cylindrical fibers that oxygen-rich air flows
through and oxygen-poor blood flows around. Because gas
diffusivity in the TAL is very small, a convection mechanism
dominates the gas transport, which is why we focus on the
velocity around the fibers (modeled as a 0.05-cm-in-diameter
and 5-cm-long cylinder). We designed a low-speed water
tunnel to study the flow mechanism around the cylinder,
across which the flow is generated by a linear actuator that
allows different flow patterns to mimic the flow in a TAL. We
tested the flow in the test section by numerical simulation and
by the particle image velocimetry method to study the flow
profile. The results show a uniform flow near the centerline of
the water tunnel where the cylinder is placed. This decreases
the effects of free-stream turbulence in the shear layers and
reduces the uncertainty in determining the flow patterns
around the cylinder. Knowledge gained from the flow around
one cylinder (fiber) is beneficial for understanding vortex
formation around multiple cylinders. We present a summary
of vortex formation behind a cylinder for Reynolds numbers
(Re) of 1, 3, and 5 and Stokes numbers (Ns) of 0.18 to 0.37;
results show that higher Re and Ns favor vortex formation.
These findings regarding the parameter range for vortex formation
may provide principles for designing artificial lungs to
enhance convective mixing. We anticipate that the pulsatile
flow circuit presented here can be used to mimic the flow not
only in TALs but in other physiological systems.
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