Flow Control Through Bio-inspired Leading-Edge Tubercles: Morphology, Aerodynamics, Hydrodynamics and Applications PDF
Preview Flow Control Through Bio-inspired Leading-Edge Tubercles: Morphology, Aerodynamics, Hydrodynamics and Applications
Daniel T. H. New · Bing Feng Ng Editors Flow Control Through Bio- inspired Leading- Edge Tubercles Morphology, Aerodynamics, Hydrodynamics and Applications Flow Control Through Bio-inspired Leading-Edge Tubercles Daniel T. H. New Bing Feng Ng (cid:129) Editors Flow Control Through Bio-inspired Leading-Edge Tubercles Morphology, Aerodynamics, Hydrodynamics and Applications 123 Editors DanielT. H.New BingFengNg Schoolof MechanicalandAerospace Schoolof MechanicalandAerospace Engineering Engineering NanyangTechnological University NanyangTechnological University Singapore, Singapore Singapore, Singapore ISBN978-3-030-23791-2 ISBN978-3-030-23792-9 (eBook) https://doi.org/10.1007/978-3-030-23792-9 ©SpringerNatureSwitzerlandAG2020 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained hereinorforanyerrorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregard tojurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland This book is dedicated to our mentors and friends, as well as past and present postdoctoral researchers and graduate students, who had given us so much. Foreword The field of biomimetics attempts to use nature as a resource to transition anatomical and physiological features from biological organisms into engineered systems. The expectation is that the lessons learned from biology can improve the performanceofengineeredsystems.Evolutionhasbeenresponsibleforasystemof natural experimentation in which organisms performed the cost-benefit analysis through the Darwinian mechanism of natural selection. The multitude of species, both extant and extinct, had to evolve adaptations as solutions to problems related to survival in their biological and physical environments. Many of these problems are the same that humans attempt to solve through their own technologies. Thus, biomimetics provides a new way of thinking and inspiration so that living organ- isms become a wide resource base of adaptations, which can be adapted for engineering applications. Emulation of organisms through the manufacture of devices has been a long-standing idea both in mythology and history. Icarus and Daedalus were supposed to have escaped their imprisonment by fashioning bird-like wings for flight. Birds as model systems for flying machines were incorporated into the designs of Da Vinci, Lilienthal, and the Wright brothers. Borelli (circa 1680) designed a submarine with buoyancy control based on the swim bladder of a fish and a propulsion system inspired by the action of the paddling feet offrogs. Inmorerecenttimes,apartnershipbetweenbiologistsandengineershasfocused attention on the use of biological organisms as model systems to improve engi- neered systems. Examples of biomimetic applications have included Velcro from plant burrs, drag reduction from shark scales, concept car design based on the boxfish,dryadhesionbasedonthegeckofoot,airconditioningfromexaminationof termite mounds, structural color and its application to paints and cosmetics, flap- ping finsand wings for bio-inspired aquaticand aerialdrones, thelotusleaf effect, spider silk, bullet train design based on the beak of kingfishers, exoskeletons, cooperative behavior, and echolocation, to mention a few areas of potential application.Whilebiomimeticsystemscontinuetobeproposed,manyarestillatan early stage of development and although extremely tantalizing they have been vii viii Foreword elusive in an understanding of the physics of these systems and their eventual application for commercial products. Theleading-edgetuberclesoftheflipperofthehumpbackwhalehaveprovedto be a structural adaptation that affords the whale enhanced maneuvering perfor- mance.Inelucidatingthephysicsbehindthefunctionofthetubercles,thisresearch has opened up new avenues in aero/hydrodynamic flow control and provided new commercial opportunities. While the original discovery in the biology of the structuraldesignandmechanicswasserendipitous,thepurposeofthetubercleswas the result of hydrodynamic analysis and testing from engineering. What has been ascertainedisthatthetuberclescontrolflowoverwing-likesurfaces.Bygenerating paired vortices in what can be called a sacrificed separation, the tubercles can maintain regions of accelerated flow along a wing that avoid separation and delay the stall condition beyond what would be normal for wings devoid of tubercles. This form of bio-inspiredpassive flow controlhas potential applicationsin aircraft and nautical design, wind and water turbines, compressors, and pumps. The tuberclesonwhaleflippersalsorepresentanauthenticexampleforbiomimeticsthat has inspired future generations of students to pursue careers in biology, engineer- ing, and energy conservation. This book offers a snapshot of the research on leading-edge tubercles as more research on the phenomenon is being performed around the world. The breadth of the chapters covered in this book demonstrated the significance and interest on thetopic.Aleadingexpertinthefieldofbiologyorengineeringwroteeachchapter. Thetopicscoveredaddresskeyissuespertainingtothefunctionoftheleading-edge tubercles. Chapter “Biomimetics and the Application of the Leading-Edge Tubercles of the Humpback Whale Flipper” defines the biomimetic approach, provides an overview of the biology of the humpback whale with respect to the function of the tubercles, and reviews the potential applications. Chapter “Tubercled Wing Flow Physics and Performance” discusses wind tunnel experi- ments focusing on the aerodynamic properties involving the tubercles as vortex generators,theirReynoldsnumbereffects,andexperimentationinaeroacoustics.In chapter “Tubercle Geometric Configurations: Optimization and Alternatives,” the geometryofthetuberclesforoptimizationofaerodynamicperformanceisexplored includingalternativedesignsaffectingdrag.Inchapter“FlowControlbyHydrofoils withLeading-EdgeTubercles,”flowbehaviorandcontrolareexaminedfromwater tunnel studies and computational fluid dynamics demonstrating the tubercles as vortex generators and exploring their function in low Reynolds number flow. The effect of tubercles on spanwise flow is examined in chapter “Leading-Edge Tubercles on Swept and Delta Wing Configurations” with an emphasis on swept and delta wing configurations. Chapter “Effects of Leading-Edge Tubercles on Dynamically Pitching Airfoils” introduces the reader to actively pitching airfoils andhowleading-edgetuberclescontroldynamicstall.Lastly,theaeroelasticeffects with structural considerations are reviewed in chapter “Effects of Leading-Edge Tubercles on Structural Dynamics and Aeroelasticity”. Foreword ix While much of the scientific aspects of the leading-edge tubercles that are presented in this book are geared toward engineering, this book has utility for biologists as well in demonstrating how engineering techniques can be used to study the biological role of adaptations possessed by an organism. In addition, biologistscan see how particularadaptationscan be selectedthat exhibit thenovel qualities that make them appropriate for biomimetic applications. As more sophisticatedmethodologiesaredevelopedtocontendwiththeparticularattributes of living organisms (i.e., small size, chemical motors, compliant wet structural materials, complex neural networks, self-healing), greater union among biologists and engineers will flourish to advance both fields through biomimetics and bio-inspired design. Frank E. Fish LiquidLifeLaboratory,DepartmentofBiology West Chester University West Chester, PA, USA Preface Appreciating and leveraging upon Mother Nature’s well-honed solutions, or bio- mimicry, have always been behind many engineering innovations. From early flying machines envisioned by Da Vinci, shark-skin-inspired surfaces for drag reduction, to bat echolocation for target tracking optimizations, humans have always attemptedto adapt nature’s answers tophysical challengestowards solving engineering problems and create new solutions. Over the last two decades since protuberances or tubercles along whale-flipper leading-edges (LE) had been pos- tulatedtoberesponsiblefortheunderwatermaneuverabilityofhumpbackwhales,a tremendous amount of research efforts had been expended to elucidate the capa- bilities of LE tubercles in terms of their functionalities, flow mechanisms under- lying favorable flow influences, and how they may be optimized for various hydrodynamics and aerodynamics applications. It is now a generally accepted notion that the implementation of LE tubercles upon lifting surfaces with the appropriate geometries tends to delay stall through mitigation of flow separation events, as compared to conventional lifting surfaces that do not have any. The unique physical features of LE tubercled lifting surfaces also led to highly three-dimensional and intriguing flow features, especially when different surface planforms such as swept or delta configurations are used. Several studies have reportedthattheLEtubercleseffectivelyfunctionasvortexgenerators,whilesome reported them as influencing both the streamwise and spanwise pressure gradients. Regardless,goodflowcontrolabilitiesofappropriatelyconfiguredLEtuberclesare observed and recognized in most experimental and simulation studies. In fact, the usefulness of leading-edge tubercles goes beyond conventional planar lifting sur- faces, as several studies have demonstrated their potential usage upon marine propellers and wind turbine blades as well. Furthermore, their effectiveness also extendsbeyondsimplyincreasingliftandreducingdrag,asstudieshaveshownthat they may be able to reduce wing flutter. As the study of LE tubercles gradually transits from understanding them and theirfloweffectstoimplementingthemforproof-of-conceptsoractualengineering applications, their designs and optimizations have also become increasingly com- plex. While the use of modern experimental techniques and numerical flow xi xii Preface modeling helped to mitigate some of these challenges, a firm grasp of the funda- mentals and the preceding research work associated with LE tubercles remains necessary, particularly in the selection and optimization of LE tubercle geometries/configurations for specific usages. As such, a book that provides key information upon the morphology of LE tubercles, how earlier studies have better inform researchers intheir design decisions, flow characteristics, and performance, as well as some of the possible applications that they could be used for, will be timely anduseful to researchers atthis point intime.The editorsand authors hope thatthisbookwillexposenewreaderstothisresearchareaandinformthemofthe current state-of-the-art research and application information, as well as inspiring themtotapintotheknowledgethathasbeengarneredthusfar.Todothat,thisbook will first introduce the readers to the practice of biomimetics with a particular emphasis on humpback whale flipper, as well as some of the new emerging engineering applications that tap into this novel bio-inspired solution. Thereafter, aerodynamicsandhydrodynamicsperformanceassociatedwithLEtubercledwings andhydrofoilswillbeelaborated. Subsequently,theeffectsofsignificantspanwise flow changes induced by the LE tubercles on swept and delta wings will be dis- cussed,followedbytheflowbehaviorofLEtubercledwingsundergoingoscillatory pitching motions. To wrap things up, new insights on the potential use of LE tubercles to control wing flutter will be presented. Last but not least, the editors would like to express their deep appreciation towardallauthorsfortheircontributionstowardthepresentbookdespitetheirbusy schedules.Itwouldnothavebeenpossiblewithouttheirdedicationandenthusiasm. Singapore Daniel T. H. New April 2019 Bing Feng Ng
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