One of the major challenges in space exploration robotics is understanding the interactions between robot wheels and planetary terrains that consist of granular regolith under reduced gravity conditions. A deeper understanding can contribute to robot wheel design and mobility control. A key factor, and the focus of this work, is the effect of gravity. A candidate theoretical framework for wheel-soil interactions is Taylor Couette (TC) flow, which models the flow between a rotating inner and a stationary outer concentric cylinder. This research models TC continuum granular flow in quasi-static and intermediate regimes to capture complexities neglected by terramechanics models without the computational expense of discrete element method (DEM). This research uses the experimental results produced by flying a TC cell aboard a reduced-gravity aircraft presented in literature to investigate the three following methods: (1) an analytical model which captures the relative trends of velocity profiles at various vertical positions and gravities, but not the absolute values; (2) finite element method (FEM) accompanied by a nonlocal constitutive model, which on average is consistent with the experimental results, but does not capture the differences at various vertical positions and gravities; and (3) material point method (MPM) accompanied by a Drucker-Prager plasticity model, which results in both absolute velocity values and trends consistent with the experimental results, at different gravity conditions. This research identifies MPM as an appropriate continuum solver to model granular flows under the influence of gravity.