This is demonstrably incorrect, as can be seen in the videos below, where one of the sheets is held away from the other and the air stream directed as in the above video. Note that the remaining sheet that is hanging moves toward the center even in the absence of the other sheet, so it does not form a narrow constriction. What is happening here is that the air moves along the surface of the sheet, according to the Coanda effect, leaving in a direction away from the center line of the two sheets. The reaction force on the sheet causes it to move toward the center line of the two hanging sheets. Click your mouse on the photographs below to see these two demonstrations of the Coanda effect.