⌛ Hourglass Sand Flow (2D): Grain-by-Grain Beverloo Law with Orifice Sweep and Force Chains

A 2D hourglass in which every sand grain is a disc in a discrete-element solver: the flow through the neck is constant, follows the Beverloo (D - k d)^(3/2) law, and an orifice sweep fits the constants, with arch jamming, force chains and flow-pattern colouring.