It has been demonstrated that terrestrial dust devils emit ULF magnetic radiation. On Mars, dust devils may also generate such magnetic emissions, which might be used as a hazard alert for manned missions. Specifically, grains in dust devils become charged via contact electrification, and it has been proposed that the cyclonic motion of these charged grains in the vortex wind fields accounts for the magnetic emission. To test this hypothesis in general and the possible Mars application, a computer simulation of the contact electrification/wind blowing phenomena was created, with the charge distribution and resulting magnetic fields monitored as a function of time. The results indicate that indeed a fluctuating charge distribution in a vortex wind can account for the ULF magnetic fields measured from a dust devil. The contact electrification process is a function of composition, and we demonstrate that the various compositions will give rise to different magnetic field responses from the dust devil. We also demonstrate that this system of swirling charged grains develops vertical currents and associated electric fields, as suggested in preceding works.