Deciduous trees shed their leaves each autumn to survive cold weather. A first step in this process causes the lose hydrophobic layer--a phenomenon that is hastened by pollution. Little known about physical details of raindrop-leaf interaction as hydrophobicity changed, yet these affect premature leaf loss and vulnerability rainstorms. The authors model dynamic response a raindrop an elastic cantilever beam, find surface can protect against impact better than hydrophilic one. These results...

Cavitation bubbles induce impulsive forces on surrounding substrates, particles, or surfaces. Even though cavitation is a traditional topic in fluid mechanics, current understanding and studies do not capture the effect of suspended objects fluids. In present work, dynamics spherical particle due to bubble experimentally characterized compared with an analytical model. Three phases are observed: growth where pushed away, its collapse approaches bubble, longer time scale postcollapse...

In nature, several seabirds (e.g., gannets and boobies) dive into water at up to 24 m/s as a hunting mechanism; furthermore, boobies have slender neck, which is potentially the weakest part of body under compression during high-speed impact. this work, we investigate stability bird's neck plunge-diving by understanding interaction between fluid forces acting on head flexibility neck. First, use salvaged bird identify phases. Anatomical features skull were acquired quantify effect beak...

Small animals and robots must often rapidly traverse large bump-like obstacles when moving through complex 3-D terrains, during which, in addition to leg-ground contact, their body inevitably comes into physical contact with the obstacles. However, we know little about performance limits of bump traversal how body-terrain interaction affects traversal. To address these, challenged discoid cockroach an open-loop six-legged robot dynamically run a varying height discover maximal performance,...

Significance Cats and dogs are assumed to drink similarly, but little is known about the actual physical mechanisms that use transport fluids when lapping. We observed drinking behavior of a wide range across breeds body size, used experiments mimic motion dog’s tongue as it exits water. Dogs accelerate upward more quickly than do cats, then time their bite coincide with pinch-off column. The everyday experience messy drinkers results from backward curl tongue, which increases size water...

Many snakes live in deserts, forests, and river valleys traverse challenging 3-D terrain like rocks, felled trees, rubble, with obstacles as large themselves variable surface properties. By contrast, apart from branch cantilevering, burrowing, swimming, gliding, laboratory studies of snake locomotion focused on that simple flat surfaces. Here, to begin understand complex terrain, we study how the kingsnake, a terrestrial generalist, traversed step friction height (up 30% snout-vent length)....

Many organisms live in confined fluidic environments such as the thin liquid layers on skin of host or partially-saturated soil. We investigate collective behaviour nematodes a layer, which was first described by Gray and Lissmann [J. Exp. Biol., 1964, 41, 135]. show experimentally that film come into contact spontaneously. By analysing time scales this aggregation, we suggest initial aggregation is driven random collisions between but continued motion due to an attractive force them arising...

It is well known that animals can use neural and sensory feedback via vision, tactile sensing, echolocation to negotiate obstacles. Similarly, most robots deliberate or reactive planning avoid obstacles, which relies on prior knowledge high-fidelity sensing of the environment. However, during dynamic locomotion in complex, novel, 3-D terrains such as forest floor building rubble, suffer bandwidth limitation large noise are sometimes even impossible. Here, we study rapid over a gap, simple,...

Droplets splash around when a fluid volume is quickly compressed. This phenomenon has been observed during common activities such as kids clapping with wet hands. The underlying mechanism involves being compressed vertically between two objects. compression causes the to be ejected radially and thereby generate threads droplets at high speed. In this study, we designed performed laboratory experiments observe process of thread drop formation after squeezed. A thicker rim outer edge forms...

The utility, efficiency, and reliability of legged robots has increased dramatically in recent years. Limbed are now capable locomotion across a variety terrains, however, achieving both rapid efficient operation when ground conditions complex or deformable is still challenging. Resistive terrains such as streams, snow, mud, littoral regions, tall grass an important class set difficult terrain which commonly found the desired operating environments robots. This work presents reduced-order,...

This paper explores whether artificial ground-mobile systems exhibit a consistent regularity of relation among mass, power, and speed, similar to that which exists for biological organisms. To this end, we investigate an empirical allometric formula proposed in the 1980s estimating mechanical power expended by organism given mass move at applicable over several orders magnitude broad range species, determine if comparable applies vehicles. We show empirically not only does apply wide variety...

Although they take many forms, legged robots rely upon springs to achieve high speed, dynamic locomotion. In this paper we examine the effect of adding parallel that on virtual compliance. Specifically, consider trade-off between energetic efficiency and leg versatility comes while using Parallel Elastic Actuators (PEAs). To do this, vary ratio physical compliance for systems a) a modified SLIP model, b) single hopping robot, c) multibody simulation quadruped robot LLAMA. each case show...

Locomotion through resistive media is an organic occurrence during traversal of the natural world. Due to complexities required analyze effect these on dynamics locomotion, controllers legged robots generally neglect or treat them as disturbances. In this paper, we address challenge producing optimal locomotion control in media. We do so by applying trajectory optimization techniques within a direct collocation framework onto reduced-order model locomotion: Fluid Field SLIP model. The...

The main objective of the work described in this paper was to design, construct and test a high-frequency response air-data probe, Fast-Response Atmospheric Turbulence probe (FRAT probe), capable ingesting sampling ambient air. This incorporates gasingesting openings that can sample passively air, measure atmospheric thermodynamic properties or content gases. be mounted on manned unmanned aircraft, dropped by parachutes. Wind tunnel testing ingestion humidity sensors are decribed. A new...