Numerical Analyses Of The Flow In The Parallel Plate Flow Chamber And Carotid Bifurcation

With the development of cellular mechanics, several kinds of devices were developed to provide the stress or strain stimulus to the cultured cells in vitro, to study the biological response of cells, the interaction among cells or between cells and other materials. The parallel plate flow chamber (PPFC) is one of the most common used devices, which is usually used to study the effects of fluid shear stress on cells under steady or unsteady flow conditions. Current research on PPFC is reviewed in this work. Then the follow studies were achieved:(1) The effect of three different inlet & outlet structures on the flow field of PPFC are numerical evaluated. The results show that the chamber sizes are more important than the inlet and outlet structures in the design of PPFC.(2) Aiming at the PPFC developed by the laboratory of biomechanical engineering of Sichuan university, the effect of the chamber sizes on the lumped-parameter resistance of the particular PPFC was studied numerically, and the lumped-parameter resistance expression was obtained by use of the least square fitting method. Flow rate, wall shear stress, and wall pressure were derived from the lumped- parameter resistance expression. And a critical height of PPFC was found, near which the effect of chamber height on WSS is the least under the same pressure difference across the inlet and the outlet.(3) Three dimensional flow field and shear stress distribution are analyzednumerically under two different unsteady pressure differences respectively, i.e., a sine wave form and the recorded inlet and outlet pressure waveforms from the experiment. The flow rate, the distribution of wall shear stress and the pressure on the surface of the lower plate are obtained.(4) The blood flow in the carotid bifurcation was simulated numerically, with three different constitutive relations of blood respectively, i.e., Newtonian, Casson and a hybrid fluid. Comparisons were made among them. The results show that Newtonian fluid is a good approximation of constitutive relation in the carotid bifurcation. The rational shear strain rate range versus the course of red blood cell congregation should be considered when the non-Newtonian property of blood couldn't be ignored. In addition, the distribution of wall shear stress indicates that the wall shear stress varies dependent upon the cellular location on artery vessel wall, which prompt that different shear stress should be applied to the cells in vitro in order to provide similar stress environment of the different location of artery vessel wall in vivo.(5) The steady flow in carotid bifurcation with symmetrical contraction in the sinus was simulated numerically, and was compared with normal carotid bifurcation. In the carotid bifurcation with symmetrical contraction, new contraction will be formed symmetrically in the downstream sinus due to the symmetrical distribution of low wall shear stress on the location. However in the actual case, the contraction will be formed firstly on the external wall of sinus, then spreads near by along the wall. Therefore, in order to simulate the contraction in carotid sinus, non-symmetrical anatomical contraction should be simulated in the future study.