# Application of Mathematical Models for Blood Flow in Aorta and Right Coronary Artery
## 4 Discussion
For instance, the superior performance of viscoelastic models in the RCA suggests that these formulations are better suited to capturing flow behaviors in small-caliber, tortuous vessels under non-uniform conditions. Therefore, beyond pure accuracy, the error distribution itself becomes a useful indicator of model suitability--offering a comparative understanding of when and where each rheological approach is most effective. This interpretation complements the working hypothesis and supports the idea that model selection should be context-driven, based on anatomical and physiological relevance as much as on numerical output. As discussed in Section 2.3 regarding the boundary conditions, the current simulations assume rigid vessel walls, which simplifies the computational setup, making this approximation a reasonable compromise between accuracy and efficiency for current clinical applications. We reiterate that in some cases, particularly when vascular stiffness is markedly increased, this assumption may be entirely valid. Nevertheless, we acknowledge that arterial walls exhibit elastic and viscoelastic behavior, particularly in large vessels such as the aorta, and incorporating FSI models in future studies would enable a more physiologically accurate representation of hemodynamic behavior. Therefore, in this study, we adopted the rigid wall assumption and used COMSOL Multiphysics(r) to focus on isolating and comparing the effects of different rheological models on blood flow under controlled, physiologically realistic conditions. Although this approach does not include direct experimental validation, it allows for a systematic and reproducible comparison across models, which is a critical step in understanding their relative predictive behavior. The rigid wall approximation is widely accepted in preliminary CFD studies, particularly when vessel wall properties are uncertain or patient-specific data are unavailable. It also offers a favorable balance between computational efficiency and physiological realism, especially in scenarios where increased vascular stiffness justifies this simplification. Furthermore, although the graphical outputs generated by COMSOL Multiphysics(r) are primarily intended for visualization, they are grounded in numerically robust solutions of the governing equations and can provide meaningful qualitative and quantitative insight when interpreted in conjunction with detailed numerical data. Accordingly, the simulation framework employed--despite its inherent simplifications--represents a methodologically sound and computationally efficient platform for the systematic comparison of rheological models under physiologically motivated boundary conditions. Finally, it should be noted that the model is steady-flow but arterial flows are not quasi-stationary--i.e., the flow field at an instant of a cardiac cycle is not the same as a steady flow at that instantaneous flow rate. The flow differs on acceleration and deceleration. This represents a limitation. An additional limitation of this study is the lack of direct experimental validation (e.g., by Doppler ultrasound or MRI) for the specific vascular geometries analyzed. However, an indirect validation strategy was adopted, comparing the simulation results with theoretical values based on physiological data available in the literature. This approach, commonly used in similar CFD studies, provided good agreement and supports the reliability of the simulation results.