A new method to determine the rate of circulation fed into a leading-edge vortex (LEV) is presented for discrete-vortex methods (DVM). The strength of vortex particles shed from the leading edge is calculated based on the velocity at the shear layer, which is formulated in terms of an inviscid parameter from unsteady thin-airfoil theory (UTAT), the leading-edge suction parameter (LESP). This new model is compared against a widely established method to determine the best way of simulating leading-edge vortex shedding in low-order models. Computational fluid dynamics (CFD) simulations and experiments are combined to test the performance of both models in two distinctive scenarios dominated by large-scale vortices: rapid transient pitch up maneuvers at a Reynolds number as low as Re=10000 and classic dynamic stall studies, characterized by periodic oscillations around the static stall angle at a high Reynolds number of 550000. The improved performance of the new model is particularly evident when the effects of thickness and Reynolds number are important.