An entirely SPH-based FSI solver and numerical investigations on hydrodynamic characteristics of the flexible structure with an ultra-thin characteristic

The fluid-flexible-structure interaction (FFSI) is characterized by the large deformation, the thin structure, and the complex turbulent flow field. Accurately simulating FFSI poses three challenges, which are the modeling of the thin structure, the capture of moving interface, and the numerical stability of multi-physics field coupling, respectively. In this study, the FFSI is simulated by the entirely smoothed particle hydrodynamics (SPH) because of its natural advantage in dealing with the moving interface within a unified framework. The shell model with single-layer particles is introduced into SPH to simulate the thin flexible structure. The truncation error caused by the single-layer boundary is modified by the normal flux approach. The k-ε turbulence model is incorporated into SPH to improve numerical accuracy in capturing turbulent details. In addition, other techniques or models that ensure the efficiency and stability of the calculation are used in this study, including PST (particle shifting technique), δ-SPH model, and GPU (graphics processing unit). The flows around the single filament and the hydrostatic benchmark are simulated to verify the accuracy of the current SPH method for simulating FFSI. The interaction between fluid and single filament and the interaction between fluid and dual-filament system are simulated to study the interacting mechanism between fluid and flexible structures. Three important conclusions are obtained by the discussions of numerical results: the critical values of dimensionless parameters can be found to determine whether the filament vibration attenuates or tends to stabilize; the stabilization time of the filament movement can be effectively reduced as the initial orientation angle increases or the perturbation of upstream flow field increases; the movement of filament with a small mass ratio is more sensitive to the perturbation of upstream flow field.