经过圆柱体的脉动流:人工肺流场的实验模型
The focus of this study is an experimental apparatus thatserves as a model for studying blood flow in a total artificiallung (TAL), a prototype device intended to serve as a bridge tolung transplantation or that supports pulmonary function duringthe treatment of severe respiratory failure. The TAL consistsof hollow cylindrical fibers that oxygen-rich air flowsthrough and oxygen-poor blood flows around. Because gasdiffusivity in the TAL is very small, a convection mechanismdominates the gas transport, which is why we focus on thevelocity around the fibers (modeled as a 0.05-cm-in-diameterand 5-cm-long cylinder). We designed a low-speed watertunnel to study the flow mechanism around the cylinder,across which the flow is generated by a linear actuator thatallows different flow patterns to mimic the flow in a TAL. Wetested the flow in the test section by numerical simulation andby the particle image velocimetry method to study the flowprofile. The results show a uniform flow near the centerline ofthe water tunnel where the cylinder is placed. This decreasesthe effects of free-stream turbulence in the shear layers andreduces the uncertainty in determining the flow patternsaround the cylinder. Knowledge gained from the flow aroundone cylinder (fiber) is beneficial for understanding vortexformation around multiple cylinders. We present a summaryof 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 formationmay provide principles for designing artificial lungs toenhance convective mixing. We anticipate that the pulsatileflow circuit presented here can be used to mimic the flow notonly in TALs but in other physiological systems.