Showing papers by "John W. M. Bush published in 2012"
TL;DR: While suction is the most common drinking strategy, various alternative styles have evolved among creatures whose morphological, physiological and environmental constraints preclude it.
Abstract: We examine the fluid mechanics of drinking in nature. We classify the drinking strategies of a broad range of creatures according to the principal forces involved, and present physical pictures for each style. Simple scaling arguments are developed and tested against existing data. While suction is the most common drinking strategy, various alternative styles have evolved among creatures whose morphological, physiological and environmental constraints preclude it. Particular attention is given to creatures small relative to the capillary length, whose drinking styles rely on relatively subtle interfacial effects. We also discuss attempts to rationalize various drinking strategies through consideration of constrained optimization problems. Some biomimetic applications are discussed.
84 citations
TL;DR: In this article, the results of an experimental investigation of fluid drops impacting an inclined rigid surface covered with a thin layer of high viscosity fluid were presented, and the conditions under which droplet bouncing, splitting, and merger arise.
Abstract: We present the results of an experimental investigation of fluid drops impacting an inclined rigid surface covered with a thin layer of high viscosity fluid. We deduce the conditions under which droplet bouncing, splitting, and merger arise. Particular attention is given to rationalizing the observed contact time and coefficients of restitution, the latter of which require a detailed consideration of the drop energetics.
83 citations
TL;DR: It is demonstrated that the hummingbird can attain the fastest nectar uptake when its tongue is roughly semicircular, and the relative importance of capillary suction and a recently proposed fluid trapping mechanism is assessed.
Abstract: We present the results of a combined experimental and theoretical investigation of the dynamics of drinking in ruby-throated hummingbirds. In vivo observations reveal elastocapillary deformation of the hummingbird's tongue and capillary suction along its length. By developing a theoretical model for the hummingbird's drinking process, we investigate how the elastocapillarity affects the energy intake rate of the bird and how its open tongue geometry reduces resistance to nectar uptake. We note that the tongue flexibility is beneficial for accessing, transporting and unloading the nectar. We demonstrate that the hummingbird can attain the fastest nectar uptake when its tongue is roughly semicircular. Finally, we assess the relative importance of capillary suction and a recently proposed fluid trapping mechanism, and conclude that the former is important in many natural settings.
50 citations
TL;DR: In this paper, the authors developed a conceptually simple theoretical model of nonwetting drop impact on a rigid surface at small Weber numbers, and provided a reasonable estimate for these two parameters with the simplest model possible.
Abstract: We develop a conceptually simple theoretical model of non-wetting drop impact on a rigid surface at small Weber numbers. Flat and curved impactor surfaces are considered, and the influence of surface curvature is elucidated. Particular attention is given to characterizing the contact time of the impact and the coefficient of restitution, the goal being to provide a reasonable estimate for these two parameters with the simplest model possible. Approximating the shape of the drop during impact as quasi-static allows us to derive the governing differential equation for the droplet motion from a Lagrangian. Predictions of the resulting model are shown to compare favorably with previously reported experimental results.
47 citations
12 Dec 2012
TL;DR: In this article, the authors present a review of the role of bubbles in the formation of clouds and their role in their formation in the evolution of water vapor, and show how bubbles can be formed and deformed.
Abstract: Bubbles. and. drops. are. ubiquitous. in. nature. and. play. critical. roles.in.many.important.environmental.processes..Most.familiar.is.the.life-sustaining.role.of.rain..Less.familiar.are.their.roles. in.the.thermal.budget.of.the.atmosphere,.chemical.and.biological.dispersion,.volcanoes.and.exploding.lakes,.and.disease.transmission..The.goal.of.this.review.is.twofold..First,.we.review.the. fundamental.physics.of.droplets.and.bubbles,.thereby.providing. a.framework.for.understanding.their.myriad.roles.in.fluid.transport. and. the. sustenance. of. life. within. the. aqueous. and. aerial. environments..Second,.we.review.the.many.environmental.settings. in. which. they. arise,. briefly. reviewing. well-studied. problems.while.highlighting.exciting.new.research.directions. Our.review.will.highlight. the.processes. that.enable. the.creation.of.drops.and.bubbles..Bubbles.may.form.in.water.through. exsolution.of.dissolved.gases,.as.may.be.prompted.by.change.in. chemistry.or.temperature,.or.through.cavitation.resulting.from. vigorous. flow.. Likewise,. droplet. formation. in. the. atmosphere. may. arise. through. condensation. of. water. vapor. prompted. by. either.cooling.or.dynamic.low.pressures..A.solid.phase.can.play. a.critical.role.in.the.birth.of.drops.and.bubbles:.through.reducing. the.energetic.barrier. to.drop.and.bubble. formation,. rough. solids.often.serve.as.nucleation.sites..The.lifetime.of.a.water.drop. falling. in. the. atmosphere. is. generally. limited. by. evaporation. and.fracture.by.dynamic.stresses,.and.may.be.extended.through. coalescence.with.other.droplets.and.growth.through.condensation.. Similarly,. the. lifetime. of. a. bubble. in. a. fluid,. be. it. a. lake,. ocean,. or. magma. chamber,. will. be. limited. by. dissolution. and. flow-induced.fracture,.and.may.be.extended.via.growth.through. coalescence.with.other.bubbles.and.exsolution.of.dissolved.gases.. The.fate.of.drops.and.bubbles.is.thus.intimately.connected.to.the. chemical,.thermal,.and.dynamic.state.of.the.ambient..The.interplay.between.drops.and.bubbles.will.also.be.made.clear:.droplets.impacting.a.free.surface.may.generate.underwater.bubbles,. while.the.bursting.of.bubbles.may.be.a.source.of.microdroplets. Our.review.of.the.basic.physics.of.drops.and.bubbles.will.indicate. that. stable.water.drops. in.air.or.bubbles. in.water.are.generally. limited. in.size. to. the.capillary. length,.a. few.millimeters.. While.this.size.limitation.makes.them.less.apparent.on.the.macroscale,.it.increases.their.range.in.the.presence.of.ambient.flow,. making.them.more.efficient.carriers.of.chemical.and.biological. material.. Indeed,. our. review. will. highlight. the. critical. role. of. bubbles.and.drops.in.thermal,.chemical,.and.biological.transport. between.atmosphere.and.ocean,.sea,.and.land..Since.biomaterial. is.often.surface.active,.it.tends.to.adhere.to.interfaces;.hence,.biodispersion.is.greatly.enhanced.by.the.substantial.range.of.drops. and.bubbles..Such.dispersion.can.be.beneficial,.as.in.the.case.of. the.spread.of.life-promoting.minerals.or.biomaterial.in.the.surf. zone,.or.deleterious,.as.in.the.case.of.pathogen.transport.in.closed. environments.such.as.airplanes.and.hospitals..Finally,.our.review. will.highlight.the.myriad.ways.in.which.drops.and.bubbles.are. exploited.by.living.creatures.for.drinking,.feeding,.and.breathing.. Just. as. the. subtle. water-proofing. strategies. of. plants. and. insects.have.provided.important.guidance.in.the.rapid.advances. in.the.development.of.superhydrophobic.surfaces.[14],.we.expect. that. such. natural. strategies. may. inform. and. inspire. new. technologies.for.microfluidic.transport.and.liquid.management. 32
17 citations
Journal Article•
TL;DR: In this paper, a large fluid torus is levitated over a circular trough, and a poloidal flow inside the ring generates a wave on its inner side, making it polygonal.
Abstract: Levitating a liquid over a vapor film was limited to droplets. Here we show that on curved substrates a larger quantity of fluid can be suspended. This opens a new possibility for exploring free-liquid-surface phenomena without any contact with a solid. In one of the simplest possible situations, a large fluid torus is levitated over a circular trough. A poloidal flow inside the ring generates a wave on its inner side, making it polygonal. This wave is described by a solitonic model which balances surface tension and the pressure depletion due to the distortion of the poloidal flow.
16 citations
Journal Article•
13 citations
TL;DR: In this article, the role of flexibility in the weight-bearing characteristics of bodies floating at an interface is considered, and a theoretical model for a two-dimensional thin floating plate that yields the maximum stable plate load and optimal stiffness for weight support is developed.
Abstract: We consider the role of flexibility in the weight-bearing characteristics of bodies floating at an interface. Specifically, we develop a theoretical model for a two-dimensional thin floating plate that yields the maximum stable plate load and optimal stiffness for weight support. Plates small relative to the capillary length are primarily supported by surface tension, and their weight-bearing potential does not benefit from flexibility. Above a critical size comparable to the capillary length, flexibility assists interfacial flotation. For plates on the order of and larger than the capillary length, deflection from an initially flat shape increases the force resulting from hydrostatic pressure, allowing the plate to support a greater load. In this large plate limit, the shape that bears the most weight is a semicircle, which displaces the most fluid above the plate for a fixed plate length. Exact results for maximum weight-bearing plate shapes are compared to analytic approximations made in the limits of large and small plate sizes. The value of flexibility for floating to a number of biological organisms is discussed in light of our study.
12 citations
TL;DR: The behaviour of broadcast spawners is rationalized by considering the encounter rates of gametes on the surface and in the fluid bulk, and the advantage of surfacing is quantified by considering an infinitely wide body of water of constant depth.
9 citations
TL;DR: A rationale for the vast volume of biological data on optimal nectar concentrations measured in a laboratory setting is provided and the relative importance of nectar transport via trapping and capillary rise in the specific case of hummingbird feeding is briefly touched on.
Abstract: Our article (1) provided a rationale for the vast volume of biological data (20 species of birds, bats, and insects) on optimal nectar concentrations measured in a laboratory setting. The comment of Rico-Guevara and Rubega (2) bears on our footnote, where the relative importance of nectar transport via trapping and capillary rise in the specific case of hummingbird feeding is briefly touched on. The point of their comment is evidently to contest the fact that hummingbirds use capillary suction, so as to defend their claim to the contrary (3).
2 citations
Posted Content•
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TL;DR: In this paper, a passive pipetting mechanism based on the coupling of the elasticity of thin plates and the hydrodynamic forces at the liquid interface has been proposed for petal-shaped objects with maximum grabbing capacity.
Abstract: We introduce a novel technique for grabbing water with a flexible solid This new passive pipetting mechanism was inspired by floating flowers and relies purely on the coupling of the elasticity of thin plates and the hydrodynamic forces at the liquid interface Developing a theoretical model has enabled us to design petal-shaped objects with maximum grabbing capacity