The Gravity node is a default node and can be used to exert a gravitational force on grains. The gravity vector can point in any direction with any magnitude, although the default is for grains to move downward using the acceleration due to gravity at Earth’s surface. This feature can only be added once to the model and it applies to all grains throughout the model.

Enter coordinates based on space dimension for the Acceleration of gravity g (SI unit: m/s2). The default magnitude for the gravity vector is g_const, which is a built-in physical constant equal to g = 9.80665 m/s2 corresponding to the standard acceleration due to gravity on Earth. The default direction is the negative y direction in a 2D geometry or the negative z direction for a 3D geometry.