The Wind Tunnel (Page 7)

Look at the backspin spin and the topspin spin. What happened here? The wake deflection is the opposite of what it should be! This is a rare fluid phenomena called "reverse Magnus effect".

Greg Zilliac the wind tunnel manager at NASA Ames decided to glue very small glass beads to the bowling ball. The glass beads looked like sugar crystals. He and Dr. Rabi Mehta felt that the beads would roughen up the surface of the ball - more like the tennis ball. Now look at the backspin and topspin in these videos. It worked! We reran the test with the rough surface bowling ball and the reverse Magnus effect disappeared.