Progress in the CFD Modeling of Flow Instabilities in Anatomical Total Cavopulmonary Connections

Abstract

Abstract-Intrinsic flow instability has recently been reported in the blood flow pathways of the surgically created total-cavopulmonary connection. Besides its contribution to the hydrodynamic power loss and hepatic blood mixing, this flow unsteadiness causes enormous challenges in its computational fluid dynamics (CFD) modeling. This paper investigates the applicability of hybrid unstructured meshing and solver options of a commercially available CFD package (FLUENT, ANSYS Inc., NH) to model such complex flows. Two patient-specific anatomies with radically different transient flow dynamics are studied both numerically and experimentally (via unsteady particle image velocimetry and flow visualization). A new unstructured hybrid mesh layout consisting of an internal core of hexahedral elements surrounded by transition layers of tetrahedral elements is employed to mesh the flow domain. The numerical simulations are carried out using the parallelized second-order accurate upwind scheme of FLUENT. The numerical validation is conducted in two stages: first, by comparing the overall flow structures and velocity magnitudes of the numerical and experimental flow fields, and then by comparing the spectral content at different points in the connection. The numerical approach showed good quantitative agreement with experiment, and total simulation time was well within a clinically relevant time-scale of our surgical planning application. It also further establishes the ability to conduct accurate numerical simulations using hybrid unstructured meshes, a format that is attractive if one ever wants to pursue automated flow analysis in a large number of complex (patient-specific) geometries.

Aortic Arch Morphogenesis and Flow Modeling in the Chick Embryo

“…Mesh generation was performed using Gambit (ANSYS Inc). A pulsatile 2 nd Order CFD solver (Fluent 6.3.26, ANSYS Inc.) originally developed for complex subject-specific anatomical flows was utilized [29,38]. This experimentally validated model incorporated an implicit pressure based numerical method, high-order discretization schemes, and a robust pressure-correction algorithm to sequentially solve the pressure continuity and the linearized momentum equations assuming i kg/m 3 × 10 -3 Pa).…”

The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

“…A study by Szabo et al (40) reported increased E a and decreased E es as well using pressure-volume analysis conducted on measurements made in a dog SV model. In addition to experimental studies, theoretical models have also predicted similar changes in E a , E es , and cardiac reserve in a Fontan circulation (14,22,28).Most of the studies thus far on the Fontan circulation can be broadly categorized into two types: 1) those that study the Fontan circulation as a whole using in vivo animal and human studies (35,36,40); and 2) those that study the fluid mechanics of the surgically created TCPC in isolation from the SV circulation (27,41,42). There have not been many studies that have connected the two, i.e., those that relate the hemodynamics of the TCPC to upstream hemodynamics and cardiac function.…”

“…Most of the studies thus far on the Fontan circulation can be broadly categorized into two types: 1) those that study the Fontan circulation as a whole using in vivo animal and human studies (35,36,40); and 2) those that study the fluid mechanics of the surgically created TCPC in isolation from the SV circulation (27,41,42). There have not been many studies that have connected the two, i.e., those that relate the hemodynamics of the TCPC to upstream hemodynamics and cardiac function.…”

Histological Studies of the Effects of Monosodium Glutamate on the Superior Colliculus of Adult Wistar Rats

“…Many recent publications on computational fluid dynamics have advocated the importance of the TCPC route 1,2 . But, many of them presupposed the central PA as a straight line.…”

“…The configuration of the extracardiac total cavopulmonary connection (TCPC) has been discussed in several publications from the hydrodynamic perspective 1,2 . To obtain a good surgical result of TCPC, several other conditions, such as preservation of the pulmonary venous return, a proportionate pulmonary arterial flow into both lungs, and prevention of sinus node dysfunction, are required besides keeping the hydrodynamic energy loss to minimum.…”