Abstract
In this study, the decay of trailing vortex was discussed. The circulation by means of the turbulent vortex model was compared with the flight data. It was pointed out that in the core region the prediction is agreed well with the experimental data but in the o uter region not. The prediction with the viscous model was compared with the flight data too. But because the viscous model has only the molecular viscosity, the rapidly decay of circulation in a relatively short time scale was not predicted precisely.
