Numerical Investigation of Fluid Flow in a Chandler Loop

Abstract

The Chandler loop is an artificial circulatory platform for in vitro hemodynamic experiments. In most experiments, the working fluid is subjected to a strain rate field via rotation of the Chandler loop, which, in turn, induces biochemical responses of the suspended cells. For low rotation rates, the strain rate field can be approximated using laminar flow in a straight tube. However, as the rotation rate increases, the effect of the tube curvature causes significant deviation from the laminar straight tube approximation. In this manuscript, we investigate the flow and associated strain rate field of an incompressible Newtonian fluid in a Chandler loop as a function of the governing nondimensional parameters. Analytical estimates of the strain rate from a perturbation solution for pressure driven steady flow in a curved tube suggest that the strain rate should increase with Dean number, which is proportional to the tangential velocity of the rotating tube, and the radius to radius of curvature ratio of the loop. Parametrically varying the rotation rate, tube geometry, and fill ratio of the loop show that strain rate can actually decrease with Dean number. We show that this is due to the nonlinear relationship between the tube rotation rate and height difference between the two menisci in the rotating tube, which provides the driving pressure gradient. An alternative Dean number is presented to naturally incorporate the fill ratio and collapse the numerical data. Using this modified Dean number, we propose an empirical formula for predicting the average fluid strain rate magnitude that is valid over a much wider parameter range than the more restrictive straight tube-based prediction.

Hemocompatibility of styrenic block copolymers for use in prosthetic heart valves

“…The Chandler loop model is able to produce thrombi which are very similar to those observed in vivo [ 29 ]. Furthermore, the average shear rates generated by the Chandler loop with dimensions and rotation rate as previously described are comparable to those found in a major artery of 50–300 s −1 [ 30 , 31 ]. For the majority of hemocompatibility measures, the modified Chandler loop was successful at removing background activation: there were only small differences between the fresh blood and control tube results for inflammatory measures and platelet activation.…”

“…The loops were rotated vertically at 30 rpm in the water bath (37 °C). At 30 rpm a half-filled Chandler loop generates shear rates in the blood of between 50 and 300 s −1 [ 30 ], which are comparable to those found in major arteries [ 31 ]. After 90 min of circulation the blood was collected in appropriate syringes [ 15 ].…”

An In Vitro Hemodynamic Loop Model to Investigate the Hemocytocompatibility and Host Cell Activation of Vascular Medical Devices

“…The strain rate, generated by the rotation of the loops, is the major parameter that will initiate biochemical cascades of blood components, including cells and cell-free proteins. But as blood is a non-Newtonian fluid, the strain rate will also be influenced by the tube curvature, respectively the length of the tubes that are closed to loops 10 . Whenever the rotation speed or loop size is changed, it is important to consider that the correlation between strain rate and rotation speed is not linear.…”

Risk assessment on-a-chip: a cell-based microfluidic device for immunotoxicity screening

“…Since capillaries are characterized by laminar flow due to their small length scales and high viscosity, the Chandler Loop model may induce NP aggregation when used for nanotoxicology applications. 60 To address this technological gap, we developed a microfluidic model that can be used to study the effect of NPs on cells of the immune system and that includes shear stress. In the establishment of a proof-of-concept device, 10 nm PVP-AgNPs were employed as a model NPs, as they are well known for their cytotoxicity.…”