Optimal helical entry flow in a helical vessel

Many large arteries present a double curvature that is known to reduce the development of flow stagnating regions, which are related to the formation of arteriosclerosis. It is not known, however, how a helical geometry affects the energetic properties of the flowing blood and whether these depend on the presence of a rotation in the entry flow. This work analyzes the flow in a finite length helical vessel of constant cross-sectional area in presence of a swirl at the entrance. The analysis is performed by numerical simulations for one geometric condition that is typical for large arteries. As expected, the optimal entry flow rotation is found in correspondence of the natural helical twist of the the vessel geometry. The energetic losses were minimized in a small range between optimal rotation and no rotation. In any case, a helical vessel presents a larger dissipation of kinetic energy than those found in a corresponding straight vessel. Although limited to steady flow and one geometric configuration, this result provides a preliminary basis for considering whether the rotation observed in the flow ejected from the heart ventricles could be part or not of a physiological optimization.