Figure 6.

Comparison of the hydrodynamic forces acting on the fish with and without wake interception, contrasting factual and force-effect simulation of the escape turn shown in figure 2; forces are quantified along and perpendicular to the fish's instantaneous trajectory at the anterior body, which is the location of the wake interception. The difference is largest at times 18–24 ms (blue window) when the fish intercepts its wake. (a) Shear forces. (b) Pressure forces. The fluid force on the anterior body was mainly a drag force resisting motion. The force-effect simulation repeated the motion of the factual simulation, thus swimming velocities were identical.