Assumptions in Hemodynamic Modelling: Limitations and Opportunities

The last decade has seen enormous growth in the use of computational methods for simulating arterial hemodynamics. As computational models become more sophisticated and their applications more varied, it is worth reconsidering the simplifying assumptions that have traditionally been made. In this presentation I will review some of the common assumptions about the constitutive properties of the arteries and the blood within, as well as the prevailing flow and pressure conditions, and their potential impact on the computed hemodynamics. In particular, I will discuss the impact of prescribing inflow/outflow boundary conditions, namely, when it is reasonable and when may be the need for multiscale modelling. Assumptions about the properties of blood are undoubtedly necessary, but the Newtonian / non-Newtonian dichotomy may prove too simplistic as simulations move from laminar flows to unstable and turbulent flows. The assumption of rigid walls, while expedient, becomes questionable for extensive domains and/or heterogeneities in the arterial wall structure and properties. Ultimately, however, it will be noted that what can be considered reasonable depends on an appreciation for the underlying uncertainties in the simulations, especially those based on imperfect medical imaging data; and that this in turn has an impact on how the results of computational models can and should be presented to engineering and clinical audiences.