I put my fans on the back, pointing up. Partly because that's where I could fit them, and partly so that I their noise isn't too loud. When I tried them on the sides or in front, their noise was a lot louder.
Anyway, the effect is that they flow air over the top and down the front. So I get visor-clearing airflow and, the way the fans work, the air being drawn into them cools the nape of my neck.