Interstitial flow, pressure and residual stress in the aging carotid artery model in FEBio.

Vascular smooth muscle cells (VSMCs) are subject to interstitial flow-induced shear stress, which is a critical parameter in cardiovascular disease progression. Transmural pressure loading and residual stresses alter the hydraulic conductivity of the arterial layers and modulate the interstitial fluid flux through the arterial wall. In this paper, a biphasic multilayer model of a common carotid artery (CCA) with anisotropic fiber-reinforced soft tissue and strain-dependent permeability is developed in FEBio software. After the verification of the numerical predictions, age-related arterial thickening and stiffening effects on arterial deformation and interstitial flow are computed under physiological geometry and physical parameters. We found that circumferential residual stress shifts outward in each layer and its gradient increases up to 6 times with aging. Internally pressurized CCA displays nonlinear deformation. In the aged artery, the circumferential stress becomes greater on the media layer (82-158 kPa) and lower on the intima and adventitia (19-23 kPa and 25-28 kPa, respectively). The radial compression of the intima reduces the total hydraulic conductivity by 48% in the young and 16% in the aged arterial walls. Consequently, the average radial interstitial flux increases with pressure by 14% in the young and 91% in the aged arteries. Accordingly, the flow shear stress experienced by the VSMCs becomes more significant for aged arteries, which may accelerate cardiovascular disease progression compared to young arteries.

An experimental study of the stability of liquid bridges subject to shear-induced closed-flow.

This paper shows via experiments, the effect of closed-flows on the stability of a liquid bridge. Experiments were conducted with a 3M HFE-7500 liquid as the liquid bridge and a mixture of sodium polytungstate solution and glycerine as the outer liquid, which is encapsulated in a cylindrical cavity. Depending on the glycerine content, the Bond number ranged from 0.04 to 0.25. It was shown that a closed-flow in both the encapsulating liquid and the bridge would increase the stability of a non-cylindrical bridge depending on the direction of shear, the Bond number and the bridge volume. It was also shown that, for a given bridge volume and Bond number, there is a capillary number that gives the maximum percentage stabilization. Any further increase in the capillary number flips the direction of the bulge from top to bottom or vice versa thereby decreasing the stabilization and at some capillary number even destabilizing the bridge. The scaling of the problem was analyzed through experimental data.