Biomedical Engineering Reference
In-Depth Information
Fig. 6 Schematic of pulsed
stretch-flow bioreactor.
From [ 24 ]
the manifold through a three way valve. During forward motion, a fixed-volume
pulse of culture medium flowed through the manifold and was distributed to each
graft; consequently, each mounted graft experienced a pressure wave with resul-
tant graft distension and transmural flow. Due to the manifold symmetry, each
mounted graft was subjected to a similar pressure wave; some variations occurred
since the graft properties at the time of mounting are not identical. During reverse
motion, the syringe withdrew medium from the jar. An in-line pressure transducer
and DO sensor were placed between the top manifold and the three way valve to
provide data for use in the computational model.
Fluid flow was modeled in 3D using the transient Navier-Stokes equation in
COMSOL Multiphysics. The full bioreactor geometry was simplified to a 1/6th
slice based on symmetry, which reduced the number of degrees of freedom from
over 250,000 to approximately 42,000. Further symmetrical simplification to
1/12th was not employed so that solutions could be more easily visualized. The
true bioreactor system has a single outlet port near the upper manifold that would
break symmetry; however, approximate flow velocity fields were deemed
acceptable for assessing fluid mixing in the system and to maximize information
gained with efficient use of computational time. The model was further simplified
by neglecting the tissue deformation that occurs during pressurization of the graft,
maintaining the tissue in a fixed position during pressurization.
 
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