arXiv subjects

John T. Antolik

Publications and source records attributed to John T. Antolik.

3 recordsLinked to original sources

arXiv2025

CyberDiver: an untethered robotic impactor for water-entry experiments

We present the CyberDiver, an untethered robotic impactor capable of actively modulating the fluid physics during high-speed water entry. First, we utilize the CyberDiver to extend our understanding of the water entry of passively flexible systems, designing a high-bandwidth controller that enables the CyberDiver to operate as a cyber-physical system that permits an arbitrary programmable structural coupling to be experimentally tested. Onboard sensors record the body acceleration during impact and reveal that the introduction of damping or a nonlinear force-versus-displacement structural law can significantly reduce impact loading as compared to a linear elastic case, with implications for damage mitigation in aerospace and naval applications. Next, by operating the CyberDiver in a displacement control mode, we demonstrate that the splash size can be dramatically altered depending on the parameters of an active maneuver, laying a groundwork for better understanding the techniques of human competitive divers.

physics.flu-dyn↗

arXiv2023

Slamming Forces During Water Entry of a Simple Harmonic Oscillator

When a blunt body impacts an air-water interface, large hydrodynamic forces often arise, a phenomenon many of us have unfortunately experienced in a failed dive or "belly flop." Beyond assessing risk to biological divers, an understanding and methods for remediation of such slamming forces are critical to the design of numerous engineered naval and aerospace structures. Herein we systematically investigate the role of impactor elasticity on the resultant structural loads in perhaps the simplest possible scenario: the water entry of a simple harmonic oscillator. Contrary to conventional intuition, we find that "softening" the impactor does not always reduce the peak impact force, but may also increase the force as compared to a fully rigid counterpart. Through our combined experimental and theoretical investigation, we demonstrate that the transition from force reduction to force amplification is delineated by a critical "hydroelastic" factor that relates the hydrodynamic and elastic timescales of the problem.

physics.flu-dyn↗

arXiv2023

Hydrodynamic irreversibility of non-Brownian suspensions in highly confined duct flow

The irreversible behavior of a highly confined non-Brownian suspension of spherical particles at low Reynolds number in a Newtonian fluid is studied experimentally and numerically. In experiment, the suspension is confined in a thin rectangular channel that prevents complete particle overlap in the narrow dimension and subjected to an oscillatory pressure-driven flow. In the small cross-sectional dimension particles rapidly separate to the walls, whereas in the large dimension features reminiscent of shear-induced migration in bulk suspensions are recovered. Furthermore, as a consequence of the channel geometry and the development and application of a single-camera particle tracking method, three-dimensional particle trajectories are obtained that allow us to directly associate relative particle proximity with the observed migration. Companion simulations of a steadily flowing suspension highly confined between parallel plates are conducted using the Force Coupling Method which also show rapid migration to the walls as well as other salient features observed in the experiment. While we consider relatively low volume fractions compared to most prior work in the area, we nevertheless observe significant and rapid migration which we attribute to the high degree of confinement.

physics.flu-dyn↗