We compare solute transport experiments to simulations in a partially-saturated, variable-aperture fracture in measured fracture aperture and entrapped-air geometry fields. The computational model tracks particles through a quasi-three-dimensional velocity field that is based on the two-dimensional solution to the Reynolds equation. The model predicts 84% of the relative increase in dispersion caused by the entrapped phase, and reproduces the experimentally observed nonlinear velocity-dependence of solute dispersion.