An investigation of the mechanical actions on a moving intruder into a granular medium subjected to a gravity field is provided using two-dimensional numerical simulation. The interactions between the grains are frictionless and modeled by Hertz's law with a viscous damping. The intruder has a cross-shaped geometry and was initially buried at a shallow depth. It has the ability to translate and rotate at constant velocities independently of each other, thus defining a translational Froude number $Fr$ and a rotational Froude number $\mathrm{\Gamma }$. We study the evolutions of the drag force $D_x$, the lift force $L_y$ and the torque $M_z$ exerted on the intruder. In the case of pure horizontal translation with a low Froude number, these quantities are constant and independent of $Fr$ with $M_z=0$. In the case of pure rotation leading to $D_x=0$, the torque is constant when $\mathrm{\Gamma }\to 0$ and increases with $\mathrm{\Gamma }$. For the combination of translation and rotation, we also determine the evolutions laws of the mechanical actions with $\mathrm{\Gamma }$: the rotation generates an increase of the torque on the intruder while the drag force decreases. We highlight the existence of a significant drop of the lift force favoring the anchoring of the intruder in the granular medium for a specific range of $\mathrm{\Gamma }$. By applying the granular resistive force theory, we determine theoretical expressions to describe the evolution of the drag force $D_x$ and the torque $M_z$. The theoretical results are in agreement with the simulation results.

Close

PrevNext

View figure in article

• 
• 
• 
• 

• Granular flows