Numerical study of granular flow and deposition influenced by hemispherical ellipsoid obstacles

In recent years, there has been growing attention to protecting against particle flow dominated natural disasters such as debris flows and landslides. Due to the complexity of disaster flows, assessing the impact of obstacles and arrays is challenging. In this study, we employ a depth-integrated Savage–Hutter model to simulate granular flows impacting hemispherical ellipsoid obstacles on steep terrain under various inflow conditions. The interactions between unsteady inflows and obstacle arrays of different heights, row numbers, and deflection angles are systematically investigated, and protective regulation is quantified using runout and deflection efficiencies. Furthermore, the flow near a single obstacle is analyzed revealing two distinct granular shock wave modes—moving shock for obstacle rotation angle of 90 ° and stationary shock for 0°—depending on obstacle orientation and inflow characteristics. Velocity evolution and Froude number variations upstream of the obstacle are examined, and the results are validated against a shock theory corrected for earth pressure effects. These detailed characterization highlights the obstacle's ability to dissipate energy, intercept, and deflect granular flows, providing new insights into the mechanisms of shock formation and offering practical guidance for the design of protective structures in natural disaster scenarios.