This image has been described in English and French as showing "Forces exerted by the VSP on water."
It seems to me to be the reverse of this situation. I think it might better be described as "Forces exerted by the water on the blades of the VSP."
The end result of this difference would reflect in the direction of motion of the craft using the device.
So if the blue arrow is the direction of rotation of the device, then the black arrows should show the direction of forces upon the blades, and thus the resulting direction of movement of the craft through the water.
I'm certainly not an engineer, however, so perhaps a qualified person could check what I'm trying to describe here.
