N. Sukhodolov, Alexander

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Article, Published VersionN. Sukhodolov, AlexanderField-scale experimentation in fluvial Hydrodynamics -experince and perspectivesHydrolinkVerfügbar unter/Available at: https://hdl.handle.net/20.500.11970/109174Vorgeschlagene Zitierweise/Suggested citation:N. Sukhodolov, Alexander (2012): Field-scale experimentation in fluvial Hydrodynamics -experince and perspectives. In: Hydrolink 2012/4. Madrid: International Association for Hydro-Environment Engineering and Research (IAHR). S. 114-117. https://iahr.oss-accelerate.aliyuncs.com/library/HydroLink/HydroLink2012_04_Fluid_Mechanics.pdf.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.Dr. Alexander N. Sukhodolov is an asso-ciate editor of the Journal of HydraulicResearch, and a senior scientist of theLeibniz-Institute of Freshwater Ecologyand Inland Fisheries (IGB), Berlin, Ger-many. He has over thirty years of experi-ence in field studies in river hydrody-namics, transport processes, andflow-biota interactions. he participatedand organized more than fifty fieldmeasurement studies and expeditions inRussia, Ukraine, Moldova, Poland, Ger-many, Italy, and the USA. These studieswere focussed on river turbulence, hy-drodynamics of recirculation flows andconfluences, flow structure in meanderbends, effects of bedforms, longitudinaldispersion and implications of hydrody-namics for benthic invertebrates, fish,and aquatic vegetation.  During the lastdecade he has been developing an origi-nal field-scale experimental approach inwhich high resolution flow measure-ments are combined with in-situ controlof flow variables. Presently he is a coor-dinator of IGB research platform on theTagliamento river.114 hydrolink number 4/2012During the last century research in fluvialhydraulics has demonstrated severalsuccessful attempts to expand the methods ofexperimentation to a prototype scale – the scaleof natural streams. With a few exceptions thoseresearch activities were primarily focusing onthe propagation of flood waves in rivers and theresults of those studies were used to verify andcalibrate numerical models. An experimentalcontrol of principal variables – a core element oflaboratory experimentation – in those studieswas achieved through the manipulation of flowrates during the releases of water from reser-voirs. These studies allowed rigorous testing ofmany theoretical approaches, for instance atheory of kinematic wave propagation, andexpanded their application for large-scalemanagement and engineering of fluvialsystems.Although the advantages of experimentation onthe prototype-scale are quite obvious, imple-mentation of this approach to the study of riverhydrodynamics until recently was almost impos-sible due to the technical limitations. Most of thestudies carried out in the field until 1995 can beclassified as measurements rather than true“experiments”. The measurements facilitatedthe assessment of flow resistance and mainlyfocused on the vertical structure of mean flowand, sometimes, turbulence. However, some ofthose studies, as for example the systematicstudies of river turbulence carried out in theUSSR by the late Prof. David I. Grinvald and hiscolleagues over thirty years period [1] andsystematic research on river confluencescarried out over the last two decades by Prof.B.L. Rhoads [2] in the USA, have contributed tothe development of experimental techniquesand established a methodology for interpre-tation of the results.In the mid- nineties, with the invention ofcommercial acoustic doppler velocimetersFIELD-SCALE EXPERIMENTATION IN FLUVIAL HYDRODYNAMICS: EXPERIENCE AND PERSPECTIVESBY ALEXANDER N. SUKHODOLOVField measurements and observations have been traditionally basicmethods in fluvial hydraulics before laboratory studies becamesuccessful and widespread. Despite the success of laboratorywork, observations and measurement studies in nature haveremained a major source of inspiration. Up-scaling the resultsobtained in the laboratory is often performed against coarse andepisodic measurements completed in the field. Recentdevelopments in acoustic velocimetry, computer technologies,laser survey and global positioning systems have greatly expandedthe possibilities for carrying out detailed field measurements.Nevertheless, the results of field observations remain snapshots ofreality while laboratory experiments give an insight into thedynamics of idealized systems. This paper reports on experienceand outlines perspectives in development of an alternativeapproach which combines field measurement studies with thetechniques of control on experimental variables.115hydrolink number 4/2012Fisheries (IGB) – the largest research center inGermanyfocused on the ecology of freshwatersystems. The necessity to quantify fluxes ofmomentum, heat, solutes and particulate matterwhich drive the functionality of aquaticecosystems in lotic and lentic environmentscomprises a modern paradigm in ecology. Thisinterest and the financial support provided bythe Deutsche Forschungsgemeinschaft  and bythe Netherland Organization for ScientificResearch allowed establishing of a researchplatform called the “Environmental FluidDynamics Laboratory in the Field (EFDL)”.EFDL was initiated by the Ecohydraulics groupof IGB in 2005 and joined by the EnvironmentalFluid Mechanics Section of Delft University ofTechnology in 2006 [4].     EFDL was launched with a series of pilot-studies which were focused on flow hydrody-namics around a finite size patch of aquaticvegetation [5] and on the dynamics of shallowlateral shear layers [6]. Those studies werecarried out on the lowland river Spree andemployed two types of experimental controltechniques. In the case of aquatic vegetationthe experimental control was established byselection of position specific for the vegetationpatch and its composition (plant species, size ofthe plants, and spatial pattern). Populationdensity in the patch was varied between theexperimental runs and the response in the flowstructure was documented by detailedmeasurements. This experimental approachhas supported the development of severaltheoretical solutions and a rigorous comparisonwith laboratory results [5]. In the studies oflateral shallow shear layers experimental controlwas provided by the regulation of flow rates intwo parallel flows separated by a splitter wall.This field experiment included several factors(unhomogeneity of riverbed roughness andpressure distribution) which were excluded inthe previous laboratory studies. The resultsobtained provided new insights into the problemand have facilitated the development of atheoretical approach that accounts for thefactors ubiquitous in natural environments [6].International Research PlatformTagliamentoSince 2008 the studies of EFDL are continuingon the river Tagliamento in Italy, Fig. 1. Thisalmost intact Alpine river system represents amodel fluvial ecosystem of European impor-tance on which intensive research has been(ADV), research on river hydrodynamics hasgained a new inspiration and valuable prerequi-sites for the development of experimentation ona prototype scale. Several field measurementstudies have proved ADVs as reliable androbust instruments capable of the accurateassessment of turbulent flows [2, 3]. Progresswas further strengthened by developments ingeodetic instrumentation and acoustical surveytechnologies which made routine surveys ofextended river reaches easy and accurate.Concomitant with these technical advancesthere appeared an obvious trend for carryingout experimental research on larger scale facil-ities. Probably the most well-known exampletoday of these facilities is the OutdoorStreamLab built in 2007 at the University ofMinnesota in the USA. This paper informs onanother initiative in field-scale experimentationwhich for a while received less attention in themedia though it has proven a success througha series of recent research projects. Environmental Fluid DynamicsLaboratory in the FieldField studies of turbulent flows have been of aspecial interest for the scientists of the Leibniz-Institute of Freshwater Ecology and InlandIAHRFig. 1    A view of the experimental river reach on the Tagliamento riverin Italy.Fig. 2   Experiments in vegetated groynefields with rigid emergent vegetation (left), and flexible submerged models of aquatic plants (right).Individual membership benefits:●     ●        ●    ●    ●         ●      ●     ●     ●    welcome IAHR         ● River and coastal hydraulics● Water resources management● Eco-hydraulics● Ice engineering● Hydraulic machinery● Hydroinformatics● Hydraulic structures, marine outfalls and urban drainage● Education and Professional Development● Fluid Mechanics● GroundwaterMembership Fees for different categories:Our two-tier fee structure reflects the countries economic standardCountry Base fee € (in 2013) Senior, Student fee € (in 2013)High income 78 39Low income 39 20IAHR, founded in 1935, is a worldwide, independent organisation of engineers and water specialists working in fields relatedto hydro-environmental science and its practical application*For information on income level of country and benefits of different categories visit “About IAHR / Membership” on the IAHR website www.iahr.org (for information: 1 Euro is approximately equivalent to 1.30 US Dollars)Join now atwww.iahr.orgSupported byTANRETNI TAICOSSALANOI ORDYHROFNOI TNEMNORIVNE-otAGNIREENIGNE HCRAESERDNpemoceb lrowehtfotra orivne-ordyhd eenignetnemn aeserdnagnir tinummochcr !y117hydrolink number 4/2012carried out by several international teams duringthe last decade [7]. This research is based on aresearch station located at the village ofManazzons in Friuli, Italy. The station has anecological lab, a set of field equipment, a dormfor the personnel and a field vehicle for trans-portation to the study sites. The region of theTagliamento River provides highly diversenatural environments suitable for a widespectrum of scientific research. Typical studiescarried out during the last decade includeresearch on bio-diversity of fluvial ecosystems,morphodynamics of braided channels and theeffects of riparian vegetation, transportprocesses of organic matter. Most recent studies of EFDL have benefitedfrom the advantages of the Tagliamentoresearch platform. In August-September 2012the studies of hydrodynamics in a vegetatedgroyne field were carried out there. A series ofseven emergent groynes was built of gravel in astraight and shallow river reach. An experimentalgroyne field was populated with the modelvegetation of two kinds: rigid cylinders andflexible silicone models of aquatic plants, Fig. 2.In the experimental runs the population densityof vegetation, its submergence and spatialpatterns were varied. The experimental setupconsisted of portable rails that supported a flatframe with an array of ADV and a bridge fordeployment operation. Detailed measurementsresolved the flowfield on a fine grid. In total eightexperimental runs were successfully completedat the steady conditions of the main flow in theriver thus allowing for further direct evaluation ofthe vegetation effect in this complex recircu-lation flow.       Perspectives and new directionsThe interest to EFDL is steadily growing andmore research groups are joining this initiative.Since 2010 the IGB EFDL team was extendedby the participation of Prof. H.M. Nepf (MIT,USA) and Prof. G.S. Constantinescu (Universityof Iowa, USA) in the research project on flow-vegetation interaction at a scale of a patch (DFGSU 629/1). This project exploits the synergybetween the field, laboratory and numericalexperimental approaches carried on the samemethodological platform. The studies of thisproject will deliver understanding on howrelevant are species-specific properties ofnatural aquatic plants for hydrodynamicprocesses at the scale of individual plants and ascale of a vegetation patch.In 2012 the EFDL research program wasexpanded with a new direction focusing on thedynamics of atmospheric boundary layers overfluvial floodplains and the role this dynamicsplay in the dispersal of aquatic insects. Aquaticinsects are vital components of fluvialecosystems. They spend most of their life cycleunderwater as benthic invertebrates. Toreproduce aquatic insects emerge for shortperiods of time and are subjected to the aerialflows over river floodplains. Only little is currentlyknown about these linkages between environ-mental factors and dispersal of aquatic insectsand the new research within the context of EFDLseeks to bridge this knowledge gap. In thisresearch the experience gained in EFDL onvegetated flows in rivers will be expanded to theaerial flows and their interaction with riparianvegetation in river corridors. In these studies theEFDL team employs ultrasonic anemometersmounted on the portable expositional musts,Fig. 3There is strong evidence that field-scale experi-mentation has become a reliable approach thatopens new fascinating perspectives in fluvialhydrodynamics. Most of the experimental and theoreticalresearch in fluvial hydrodynamics is focusing onidealized flows.  In idealized setups researcherseliminate or minimize some processes orcomponents of dynamic systems and therebyseek for particular solutions in the dynamics ofcomplex systems. Field-scale experiments havethe potential for encountering solutions of amore general character. For example, recentfield measurements on river confluences haveclearly demonstrated the importance of lateralfluxes of mean momentum [2] and inspireddetailed field experimentation research thataddresses the role of those fluxes in thebehavior of the lateral shear layers [4].Although this short article demonstrates theimportance and effectiveness of the field experi-mental approach, field measurements andexperimentation remain difficult and rare. One ofthe principal reasons for a relatively smallnumber of field studies and field experiments isthe lack of a specialized education and trainingof both scientific and technical personnel.Presently this gap in educational programs isnot compensated by any occasional trainingprogram in framework of summer schools orshort courses. Another reason is the absence ofspecialized equipment for field experiments. Forinstance, mounting equipment for instrumen-tation in the field is presently manufactured onlyon customized basis. There is a lack of guide-lines and information on the methodical aspectsof field measurements and experimentation isscattered among specialized papers. Inconclusion I would like express a hope that theIAHR community might consider these points ofconcern and can improve the situation byoffering some educational courses in theframework of existing summer schools andsupporting the preparation of guidelines.      References[1]   Grinvald D. I., and V.I. Nikora (1988) River turbulence,Hydrometeoizdat, Leningrad, Russia.[2]   Rhoads B.L., and A. Sukhodolov (2008) Lateral momentum fluxand the spatial evolution of flow within a confluence mixinginterface, Water Resources Research, 44, W08440.[3]    Sukhodolov A., Thiele M., and H. Bungartz (1998) Turbulencestructure in a river reach with sand bed, Water ResourcesResearch 34, 1317-1334.[4]   Sukhodolov A., and W.S.J. Uijttewaal (2010) Assessment of a riverreach for environmental fluid dynamics studies. Journal ofHydraulic Engineering 136, 880-888.[5]    Sukhodolova T., and A. Sukhodolov (2012) Vegetated mixing layeraround a finite-size patch of submerged plants: Part I   Theoryand field experiments.  Water Resources Research 48, W10533.[6]    Sukhodolov A., Schnauder I., and W.S.J. Uijttewaal (2010)Dynamics of shallow lateral shear layers: experimental study in ariver with a sandy bed.  Water Resources Research 46, W11519.[7]    Tockner K., J.V. Ward, D.B. Arscott, P.J. Edwards, J. Kollmann,A.M. Gurnell, G.E. Petts, and B. Maiolini (2003) The Tagliamentoriver: a model ecosystem of European importance. AquaticSciences 65, 239-253.Fig. 3  Measurements of wind profiles over the floodplain of the Tagliamento.

Field-scale experimentation in fluvial Hydrodynamics - experince and perspectives

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Field-scale experimentation in fluvial Hydrodynamics - experince and perspectives

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