  Three dimensional blob dynamics are simulated in X-point magnetic
configurations in the TORPEX device via a non-field-aligned coordinate system,
using an isothermal model which evolves density, vorticity, parallel velocity
and parallel current density. By modifying the parallel gradient operator to
include perpendicular perturbations from poloidal field coils, numerical
singularities associated with field aligned coordinates are avoided. A
comparison with a previously developed analytical model is performed and an
agreement is found with minimal modification. Experimental comparison
determines that the null region can cause an acceleration of filaments due to
increasing connection length, but this acceleration is small relative to other
effects, which we quantify. Experimental measurements are reproduced, and the
dominant acceleration mechanism is identified as that of a developing dipole in
a moving background. Contributions from increasing connection length close to
the null point are a small correction.
