Flow behind a Finngulf 43 asymmetrical spinnaker at AWS= 3,3 m/s (7 kn) and AWA= 150 degrees. This animation illustrates well how complex the flow behind the sails can be when running downwind.

Air escaping under the foot of the spinnaker reverts back and spreads on the surface of the sail, to be further bent forward by the external flow from behind. Two different vortices are being formed, one from the foot/leech and the other from the luff. Note: this represents only an instant in the ever changing, turbulent flow behind the sails on the run. These vortices will be dissolved in the turbulent wake, to be replaced by new ones.