A constructal hemodynamic study of bypass grafts with size constraint

Abstract

A blood vessel bypass is a common way to restore blood flow due to blocked or narrowed arteries allowing oxygen-rich blood to be routed to the tissues. Herein, using a three-dimensional numerical simulation, the response of various vessel bypass designs to blood flow under size-limiting constraints is explored and compared to the flow in healthy arteries. Finding the best design requires a size constraint in the analysis; otherwise, the result is a configuration with excessive size in a limited allocated space, which represents a waste of material and an unnecessary space occupied by it. This study unveils the geometrical features of bypass grafts that have structural integrity while also minimizing the rate of entropy generation under volume constraint (constructal design). In a stenosed vessel with a bypass, the effect of bypass geometry, graft-vessel(host) diameter ratio, and stenose degree is analyzed and compared to a healthy vessel. This study concludes, among other things, that leaving the stenosed region of the vessel permeable to blood flow is only safe if the degree of stenosis is less than 0.5, both in terms of not being significantly different from flow conditions in a healthy vessel and also in terms of the structural integrity of the graft. The results presented here can be applied to any bypass graft and provide designers and practitioners with basic information.