# Numerical Simulation and Analysis of Heart-Aorta Fluid-Structure Interaction Based on S-ALE Method
## 1 Introduction  
Cardiovascular disease is one of the leading causes of death worldwide, and the pathogenesis of aortic diseases (such as aortic dissection and aneurysms) is closely related to hemodynamic factors [1, 2]. The heart and aorta form a complex FSI system, and the interaction between blood flow and the vessel wall directly affects the mechanical response of the vessel and the pathological development. Traditional medical imaging techniques, e.g., ultrasound, computed tomography (CT), and cardiovascular magnetic resonance (CMR) can provide basic information about blood flow and vascular morphology, but they are unable to accurately quantify hemodynamic parameters such as WSS and pressure distribution and cannot directly reflect the dynamic deformation process of the vascular wall [3, 4]. Therefore, numerical simulation analysis has become an important research method for effectively reflecting hemodynamic responses under physiological states. In recent years, the integration of computational fluid dynamics (CFD) and the finite element method (FEM) has provided an effective approach for FSI simulations [5, 6, 7]. However, conventional CFD-FEM coupling methods face challenges such as mesh distortion and poor computational stability when dealing with large deformation problems (e.g., pulsatileexpansion of the aorta) [8]. The Arbitrary Lagrangian-Eulerian (ALE) method has been widely adopted in cardiovascular FSI simulations due to its ability to effectively balance the Eulerian description of the fluid domain and the Lagrangian description of the structure domain, making it suitable for large deformation FSI problems [9]. The Structured-ALE (S-ALE) method is based on the ALE method and incorporates structured meshes and adaptive technology to effectively improve the computational stability of large deformation problems. This methodology has been successfully validated in impact mechanics, particularly in ship engineering applications [10; 11]. However, its application in biomedical engineering, particularly for heart-aorta FSI simulations, remains an area requiring further exploration. The hemodynamics of the vascular system is a complex physiological process. The dynamic mechanical loads generated by periodic pulsatile blood flow can affect the tissue structure of the vascular wall, thereby inducing various vascular diseases. To investigate the FSI action mechanisms between blood flow and vascular walls, scholars have developed a variety of research methods and made significant progress [12; 13; 14; 15]. However, due to computational efficiency considerations, some studies typically model only local regions of the blood vessels [16; 17] or even use idealized structural models to simplify the analysis [18; 19]. For example, [PERSON] et al. [20] employed an idealized thin-walled cylindrical model to simplify the geometric characteristics of real blood vessels when conducting a comparative analysis of the effects of arterial wall structure on hemodynamics and vascular deformation in normal and stenotic states. However, the reliability of this model was lacked sufficient experimental or clinical data validation. In terms of fluid domain modeling, [PERSON] et al. [21] used the smooth particle hydrodynamics (SPH) method to discretize blood components. However, due to computational efficiency limitations, each particle only represented the average characteristics of the blood components and could not accurately reflect the continuity of real blood flow. Although the ALE method is widely used in blood-related FSI analysis, its fluid domain modeling is highly dependent on high-quality hexahedral meshes [22; 23; 24]. During the preliminary modeling phase, a significant amount of time is often required for mesh generation. In order to obtain a high-quality mesh, it is usually necessary to simplify the geometry of the model, which can affect the accuracy of the simulation to a certain extent.