1. Kinematics and hydrodynamics of free swimming.
Kinematics and hydrodynamics of free swimming. High-speed video recordings of (A) the power and (B) the recovery strokes for a water boatman (8 ms intervals) revealed a similar paddling motion to tethered swimming (Fig. 4), but here the insect was free to advance forward. (C) Reversals in the wrist angle were used to define the duration of the power strokes (gray bars). We measured (C) the angle and (D) the velocity (uP) of the paddle (relative to the body) to model thrust. Forward dynamic simulations included thrust and drag on the body to predict changes in the speed of the body over time (Eqn 8). (E) These predictions of speed (black curve) were tested against measurements (gray curve) for the same sequence. (F) The thrust (red curve) predicted by this model peaked at around the middle of the body stroke as the total drag generated by the body and appendages (blue curve) lagged behind in time, as the body gained speed as a result of the thrust impulse. (G) The power generated by the paddle (purple curve, Eqn 11) and that applied to thrust (red curve, Eqn 12) are plotted with the power lost through the generation of drag (blue curve, Eqn 13). The peak thrust power progressively exceeded the power generated by the paddle as a result of the increased body velocity across power strokes. (H) These values for power were integrated over time in comparison to the kinetic energy of the body (green curve, Eqn 15).
Victoria Ngo, and Matthew James McHenry J Exp Biol 2014;217:
© Published by The Company of Biologists Ltd