Propagation velocity analysis of a single blob in the SOL

Nonlinear simulation of plasma blob propagation in the tokamak scrape-off layer is reported. Three types of model equations are introduced and the simulation results are compared. It is found that in the parameter regime where the interchange instability appears during the propagation process, the theoretical model of propagation velocity determined by the initial blob size provides a good approximation of the simulation results. In the regime where the Kelvin-Helmholtz instability appears, however, the blob velocity saturates at a lower value.