Experimental Flow Studies in Exact-Replica Phantoms of Atherosclerotic Carotid Bifurcations Under Steady Input Conditions

Abstract

Extensive flow studies are conducted in two carotid bifurcation flow phantoms. These phantoms exactly replicate the lumen of the plaque excised intact from two patients with severe carotid atherosclerosis. The input flow into the phantom's common carotid artery is steady. Novel scanning techniques for flow visualization and particle image velocimetry are used. In addition, a novel boundary treatment technique is employed in velocimetry to extract first order accurate velocity gradients at walls. The data show that the flow fields are highly three-dimensional. Numerous separation and recirculation zones dominate the flow domain, except at the lowest Reynolds numbers. The separation regions are often so severe that highly directed internal jets form. At high Reynolds numbers, the flows become unsteady and chaotic, even though the input flow is steady. Flow fields have large regions of energetic flow and almost stagnant recirculation zones. These recirculation zones range in size from the full size of the arteries to zones within crevasses smaller than 1 mm. Velocity field and streamline patterns conform well to the lumen geometry. The streamlines are highly tortuous. Stagnation points correlate well with the topological features of the stenosis. Vorticity maps confirm the highly complex and three dimensional nature of the flow. Wall shear stresses at the stenoses are estimated to be on the order of 10 Pa. These studies conclusively show that the nature of the flow in the diseased bifurcation is primarily dictated by the lumen geometry.

A review of solid–fluid selection options for optical-based measurements in single-phase liquid, two-phase liquid–liquid and multiphase solid–liquid flows

“…The density of silicone rubber varies widely based on its exact composition; however, it is usually in the range of 1100-2300 kg/ m 3 . Flexibility makes silicone rubbers particularly useful for compliant models of flows through flexible structures or membrane-like tissues, e.g., in RIM models for bloodflow experiments and, as a result, have been frequently employed in such systems (Duncan et al 1990;Perktold et al 1997;Bale-Glickman et al 2003;Burgmann et al 2009;Shuib et al 2010;Yousif et al 2010;Gülan et al 2012;Pielhop et al 2012;Geoghegan et al 2012;Im et al 2013;Kefayati and Poepping 2013). Sylgard 184, manufactured by Dow Corning, has been identified as a silicone rubber of particularly interest (Duncan et al 1990;Perktold et al 1997;Hopkins et al 2000;Yousif et al 2010;Shuib et al 2010;Buchmann et al 2010Buchmann et al , 2011Geoghegan et al 2012 andKefayati andPoepping 2013).…”

“…Consequently, they are preferentially chosen for the study of flows in complex geometries, e.g., biological systems, moving machinery, etc. (Soranna et al 2008;Bale-Glickman et al 2003). Two manufacturing processes are commonly used for the production of plastic components (e.g., test sections) that are commonly employed in scientific studies, namely extrusion and casting; more recently, rapid prototyping and 3-D printing processes have allowed an even greater range of components to be made from suitable plastics.…”

“…(iii) Particle image/tracking velocimetry (PIV/PTV) and variants thereof have been covered in detail by Adrian (1986Adrian ( , 1991, Arroyo and Greated (1991), Maas et al (1993), Grant (1997) and Fu et al (2015), among others. These techniques can provide velocity information in two or three dimensions (2-D/3-D) and have been used in many RIM systems, e.g., by Northrup et al (1991), Peurrung et al (1995), Zachos et al (1996), Hopkins et al (2000), Longmire et al (2001), Bale-Glickman et al (2003), Ninomiya and Yasuda (2006), Burgmann et al (2009), Dietze et al (2009) Buchmann et al (2010, Berard et al (2013), Im et al (2013), Yagi et al (2013), Morgan et al (2013), , Krug et al (2014).…”

Particle collision and adhesion under the influence of near-fields

“…For extensive analyses addressing modeling and numerical procedures, see [Jou and Berger 1998;Berger and Jou 2000;Kaazempur-Mofrad and Ethier 2001;2004;Stroud et al 2002;Stroud et al 2000]. For experimentally-oriented physiological flow studies of atherosclerotic carotid bifurcations and related systems, see [Bale-Glickman et al 2003b;2003a]. Notably, Bale-Glickman et al [2003b;2003a] have constructed flow models which replicate the lumen of plaques excised intact from patients with severe atherosclerosis, which have shown that the complex internal geometry of the diseased artery, combined with the pulsatile input flows, gives exceedingly complex flow patterns.…”

“…For experimentally-oriented physiological flow studies of atherosclerotic carotid bifurcations and related systems, see [Bale-Glickman et al 2003b;2003a]. Notably, Bale-Glickman et al [2003b;2003a] have constructed flow models which replicate the lumen of plaques excised intact from patients with severe atherosclerosis, which have shown that the complex internal geometry of the diseased artery, combined with the pulsatile input flows, gives exceedingly complex flow patterns. They have shown that the flows are highly three-dimensional and chaotic, with details varying from cycle to cycle.…”