(666b) Hybrid 1D/3D Blood Flow Simulations of the Arterial Human Network

Continuing our previous work of blood flow simulations within the human arterial network [1,2] we present here an investigation of the effects of the non-Newtonian character of blood rheology.  This involves the implementation of a recently developed viscoplastic description of the steady-state blood flow rheology into the previously developed 1D model of the flow within the arterial network.  This new rheological model is still based on the Casson equation but involves a new parameterization of its coefficients in terms of important physiological parameters, such as the blood hematocrit and fibrinogen concentration, so that it much better fits available experimental data.  A similar re-parameterization is also performed for the apparent Newtonian viscosity used in the description of the transient component of the flow.

Those newly described aspects of non-Newtonian rheology of blood are then examined with respect to their influence to the predictions of the 1D approximate arterial flow model as well as with respect to their effect to a hybrid 1D/3D simulation, following [2], of the time-periodic blood flow through a non-axisymmetric (coronary) arterial bifurcation.  These simulations involve, as explained in [2], an efficient implementation of the proper (in vivo) outlet boundary conditions, as provided in the form of Fourier frequency impedance coefficients by the 1D model, to a commercial 3D (FLUENT) code.  In contrast to our previous simulations of the left coronary artery bifurcation [2] a much more faithful to the actual geometry mesh representation is used at this time, in addition to the implementation of non-Newtonian rheology characteristics both in FLUENT and in the 1D model (as described above).  The non-Newtonian effects are examined in two cases: First a healthy system, patterned after the left main coronary arterial system, and second a diseased case where an occlusion has developed in one of the daughter vessels, resulting in strengthening the asymmetry of the bifurcation.

References

[1] Johnson, D.A., Spaeth, J.R., Rose, W.C., Naik, U.P., Beris, A.N., An Impedance model for blood flow in the human arterial system, Part I: Model Development and Matlab Implementation. Computers in Chemical Engineering, 35(7): 1304-1316, (2011).

[2] Johnson, D.A., Naik, U.P., Beris, A.N., Efficient implementation of the proper outlet flow conditions in blood flow simulations through asymmetric arterial bifucations. Int. J. Numer. Meth. Fluids, 66(11): 1383-1408, (2011).

Acknowledgement

This work is supported by NSF, Grant Award # NSF CBET 1033296