Novel rotational effects of granular intruders in dense granular systems
Item statusRestricted Access
Embargo end date03/07/2021
In the present numerical work, it is demonstrated that the ﬂow generated by the rotation of an intruder with a circular cross-section fully immersed within a dry granular system compacted by gravity generates a lift force, in addition to a horizontal force on the intruder. Typically, such horizontal component of force is found to be in the direction opposite to that of friction on its lower surface, counterintuitively antithetic to that of a rotating object (e.g. a wheel) on a frictional surface. For a rotating intruder, this results in motion along the direction of such forces. Furthermore, it is demonstrated that the Magnus effect isn’t applicable to granular systems as a rotating circular intruder within a uniform granular ﬂow experiences a negative lift force. These phenomena are shown to be peculiar of granular systems. An extensive parametric study of forces on the intruder and of its motion is carried out, and relationships developed for the following system properties: intruder diameter and length, angular velocity, frictional coefﬁcient, velocity restitution coefﬁcient, as well as properties peculiar to each system. These results shed new light on the peculiar nature of granular systems and they open exciting possibilities in terms of industrial applications, by enabling non-destructive propulsion within ubiquitous granular systems such as cereal grains and chemical powders.