This research experimentally studied the granular flow in the optimised curved hoppers obtained from our recently published optimisation method. A series of optimised hoppers were manufactured by CNC machining and an experimental apparatus was constructed to measure the MDR of various granular materials in the hoppers. Our experiment confirmed that the MDR of the optimised curved hoppers has increased more than 100% from that of those conventional conical hoppers. The critical prefill level for reaching a steady discharge rate in the curved hoppers is related to a fixed ratio to the diameter of the hopper orifice, which increases with the initial half-angle of a curved hopper. Three types of granular materials, i.e. rice, urea powders and sands, differing in shape, density and surface roughness, all gained improved MDR in the same curved hoppers, which demonstrates the flexibility of the optimised curved hoppers to maximize MDR for different granular materials. (C) 2020 Elsevier B.V. All rights reserved.