Bio-inspired shape-morphing actuation of a heaving plate: An experimental study to explore its flow physics and hydrodynamic performance

In this study, we present a comprehensive experimental investigation of the effect of shape-morphing on the flow physics of a submerged heaving plate in a quiescent, incompressible, Newtonian viscous fluid. Motivated by bio-inspired underwater swimmers that change body shape to optimize fluid–structure interactions (FSI), shape-morphing is explored here as a mechanism for adaptive hydrodynamic performance via modulation of vortex shedding and convection patterns. Shape-morphing is implemented on a robotic platform comprising a heaving plate actuated to produce dynamic changes of its cross section in phase with a rigid oscillation. To inform the experiments, a boundary element method model is first used to study an idealized shape-morphing heaver under linear hydrodynamic conditions, isolating how shape-morphing interacts with heaving motion to reduce force and power. Through a systematic experimental campaign conducted on our shape-morphing robot, we analyze both qualitative flow features, such as vortex dynamics and symmetry breaking, and quantitative aspects of the hydrodynamic forces, employing particle image velocimetry and direct measurements via a load cell. Results show that shape-morphing significantly impacts the FSI, particularly by reducing vortex shedding intensity, minimizing hydrodynamic forces, and lowering energy dissipation. These effects are primarily governed by the prescribed shape-morphing angle, with force minimization occurring at specific optimal angles. Our findings provide key insights into the relationship between shape-morphing actuation and hydrodynamic force control, with implications for underwater propulsion in soft robotics.