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The aim is to study the blood flow and vessel wall viscoelastic alterations at the boundary layer. Methods and Results: In 12 healthy men (18 - 52 years of age) at the different sites of the aorta peak velocity, net flow, flow acceleration has been investigated by Magnetic Resonance Angiography. In the aortic arch in the end systole blood flow separates into the opposite directed streams resulting in the wave superposition. At the outer curvature of the isthmus, flow acceleration in the initial diastole is 6.26 times higher than that in systole. Net flow from systole to diastole increases 2.5 ± 0.5 folds. From the end systole to the initial diastole there is a plateau on the net flow graph. At the outer curvature of isthmus, group wave at the boundary reflection, changes in phase at 180o. Herewith, flow wave oscillation frequency at the outer curvature is two times higher (2.5 Hz) than that at the inner (1.25 Hz). Conclusion: During the heart cycle, blood motion at the boundary layer, forms the surface wave and facilitates the blood structural rearrangement and flow. At the end systole, at the outer curvature of the isthmus, pulse pressure at the reflection is in the resonance with the end systolic pressure drop. Amplitude of the wall stress increases. Forming standing wave leads to the dissipation of the wall mechanical energy. Here, in the initial diastole, group wave, due to the wave reflection and frequency dispersion, facilitates the structural rearrangement/denudation of the vessel wall. By the removing resonance oscillation during the end systole/initial diastole between the heart and vessel wall, atherosclerosis can be avoided.

Wave Reflection at the Boundary Layer and Initial Factors of Atherosclerosis