  This study reports on the vortex-induced lift production mechanisms in low
Reynolds number flows over low aspect-ratio rectangular wings. We use a
rigorous force partitioning method which allows for the estimation of the
pressure-induced aerodynamic loads due to distinct flow features or vortex
structures in the flow around the wing. The specific focus of this work is on
distinguishing the effect of spanwise and cross-span oriented vortex structures
on pressure-induced lift production. We quantify the lift induced on the wing
by these different vortices, and also estimate their influence within different
regions of the flow-field around the wing and in the wake. By varying the
aspect-ratio and angle-of-attack of the wing, we show that for most cases, the
spanwise oriented vorticity contributes less to the total lift than cross-span
oriented vortices. Furthermore, the spanwise vorticity in the near wake is
capable of producing net negative lift on the wing and this is explained by
separating and quantifying the influence of vortex cores and regions of strain
in the wake. The results demonstrate the utility of the force partitioning
method for dissecting the flow physics of vortex dominated flows.
