If I remember correctly, in the book Skunkworks they explain that it would increase the air pressure. The analogy made was that it was similar to putting a fing

If I remember correctly, in the book Skunkworks they explain that it would increase the air pressure. The analogy made was that it was similar to putting a finger on a garden hose to partially block it, thus increasing the water pressure. Obviously there must be some complex physics going on but that was the gist of it. Probably someone with more knowledge can confirm or correct me :)