Airflow Field and Shelter Effect Around Flexible Plants Using Fluid-Structure Interaction (FSI)-Large-Eddy-Simulation (LES) Simulations

Vegetative windbreaks have a significant advantage in regulating microclimates and improving soil conditions. Some studies highlight the importance of turbulence and plant flexibility, but few has investigated the relationship between flexibility and the shelter effect of windbreaks. Therefore, we perform a series of 3D fluid-structure interaction (FSI)-large-eddy-simulation (LES) simulations to study the airflow passing through flexible single-plant windbreaks. We first model the plants with branches according to their geometric features in the field, present a FSI solver to strongly couple the airflow velocity field and windbreak vibration, and then use a LES turbulent model to resolve the turbulent flows. Based on the simulations, the airflow fields around the plants (Plant #1 and Plant #2) with different flexibilities, evaluated by Young's modulus, were analyzed and compared. Afterward, the shelter effect of flexible plants is analyzed based on three indices, including turbulence intensity, surface shear stress and plant swing displacement. The peak turbulence intensity of the three plants follows the order Plant #1 > Plant #2 > rigid plant. Regardless of wind speed, the surface shear stress around the plants follows the order Plant #1 < Plant #2 < rigid plant. The swing displacement increases as the velocity and flexibility increase. It is concluded that the flexible plant has a better shelter effect than the rigid plant, and within a certain range, the stronger the flexibility of the plant is, the better its shelter effect. This study not only investigates the interaction mechanism between flexible plants and airflow, but also provides a theoretical reference for the application of flexible plants in wind protection engineering.