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In the Wikipedia article on Slipstream (https://en.wikipedia.org/wiki/Slipstream ) it is said: "A slipstream is a region behind a moving object in which a wake of fluid (typically air or water) is moving at velocities comparable to the moving object".

The word "comparable", to me, creates the impression that the velocity is lower than that of the moving ebject.

Then in the article on "Wake" (https://en.wikipedia.org/wiki/Wake) it is said: "the wake is massively separated and behind the body is a reverse flow region where the flow is moving toward the body", implying that the relative velocity is positive.

I myself think the following way: the object pushes the air away as it moves, and hence, let us imagine the following experiment: The object is still, and a volume of air is deleted from the air behind it. This is equivalent to our initial problem. In this thought experiment, the observed flow will be directed towards the object, since there will be no air flowing in from that side. Is that a correct explanation?

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You need to add another wiki page to your thoughts; Flow Separation. As you see in the illustration there, there is circulating flows inside the slipstream. This means that the average velocity is practically zero, but in the typical case of a boat wake, there are two circulations which are rotating in the middle of the wake towards the boat, but on the flow separation zone away from the boat. This causes the visual effect that these slipstream flows doesn't move at all there where they contact the surrounding fluids, and that they travel with higher speed than the boat in the middle of the slipstream. When in reality, this rotating water just travels with the speed of the boat in the Slipstream.

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