Modeling Natural Hydrodynamic Systems with a Differential-Turbulence Column

Brunk, Brett K.; Weber‐Shirk, Monroe L.; Jensen, Anna Lyhne; Jirka, Gerhard H.; Lion, Leonard W.

doi:10.1061/(asce)0733-9429(1996)122:7(373)

Cited by 24 publications

(11 citation statements)

References 6 publications

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“…In situ sampling can be performed for introducing chemical species and monitoring chemical dynamics. Under homogeneous and open channel flow, turbulent conditions, sediment profiles obtained in the differential‐turbulence column accurately followed conventional theory (Brunk et al . 1996).…”

Section: Integrated Process Studies On Erosion Risks and Pollutant Mosupporting

confidence: 52%

“…The differential-turbulence column was developed at Cornell University (Ithaca, NY, USA) in the framework of a doctoral thesis by Brett Brunk and was initially used to simulate the homogeneous, turbulent kinetic energy and sediment-loading profiles for open channel flow (Brunk et al 1996). The reactor consists of five vertically spaced grids which oscillate to simulate turbulence in natural hydrodynamic systems.…”

Section: Erosion Risk Assessment: Pressure Duct Experiments On Sedimementioning

confidence: 99%

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Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

Förstner

2004

Lakes & Reservoirs

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Characteristic dynamic features of sediment-related processes in rivers include dramatic effects of stormwater events on particle transport, rapid and far-reaching effects of sulphide oxidation during resuspension, and biological accumulation and potential release of toxic chemicals. Pollutant mobility is the net result of the stabilizing and mobilizing effects in both hydraulic and chemical fields. In practice, emphasis has to be given to fine-grained sediments and suspended matter as these materials exhibit large surface areas and high sorption capacities. Organic materials are highly reactive. Degradation of organic matter will induce oxygen depletion and might enhance formation of flocs and biofilms. Study of variations of sediment and water chemistry should predominantly include changes of pH and redox conditions, competition of dissolved ions and processes such as complexation by organic substances. Major questions relate to the potential reduction of sorption sites on minerals and degradation of organic carrier materials. All these processes will influence solution/solid equilibrium conditions and have to be studied prior to modelling the overall effects of pollutants on the water body and aquatic ecosystems. With respect to handling and remediation of contaminated river sediments, either in-place or excavated, a chemical and biological characterization of the material, of the (disposal) site and of the long-term processes is crucial. Passive techniques (e.g. in situ stabilization, subaqueous capping) provide economic advantages as there are no operation costs following their installation. However, the success of these ecological and geochemical engineering approaches is mainly based on an in-depth knowledge of the underlying processes.

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Section: Integrated Process Studies On Erosion Risks and Pollutant Mosupporting

confidence: 52%

Section: Erosion Risk Assessment: Pressure Duct Experiments On Sedimementioning

confidence: 99%

Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

Förstner

2004

Lakes & Reservoirs

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“…The first mode of grid operation is a short, relatively rapid oscillation centered on a fixed location (Estrada et al 1987, K i~r b o e et al 1990, Saiz et al 1992, Howarth et al 1993, Hwang et al 1994, Landry et al 1995, Brunk et al 1996. This mode has several advantages.…”

Section: W E L L -M I X E D M E S O C O S M S T R a T I F I E D M E Smentioning

confidence: 99%

“…This mode has several advantages. A large portion of the water column is undisturbed, there are good published measurements of oscillating grid turbulence (Brumley & Jirka 1987, Hill et al 1992, Howarth et al 1993, Brunk et al 1996, and direct measurement of mixing power is possible through the use of force and displacement transducers (Kiarboe et al 1990). The major disadvantage of this mode of operation is that there is an extremely large gradient in turbu.lent dissipation rate away from the center of oscillation.…”

Section: W E L L -M I X E D M E S O C O S M S T R a T I F I E D M E Smentioning

confidence: 99%

Turbulent mixing in experimental ecosystem studies

Sanford¹

1997

Mar. Ecol. Prog. Ser.

122

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ABSTRACT. Turbulent mixing is an integral aspect of aquatic ecosystems Turbulence affects ecosystem features ranglng from phytoplankton blooms at large scales through microscale interactions in the plankton. Enclosed experimental ecosystems, if they are to mimic the function of natural ecosystems, also must mimic natural turbulence and its effects. Large-scale velocity gradients and unstable buoyancy fluxes generate turbulent mixing in nature, most often at the surface and bottom boundaries and in the pycnocline. Large eddy sizes are controlled by the mixed layer depth, boundary layer thickness, or overturning length in the pycnocl~ne. Turbulent energy cascades through smaller and smaller eddy scales until it can be dissipated by molecular viscosity at the smallest scales. In contrast, artificial apparatuses frequently are used to generate turbulent m~x i n g in the interior of experimental ecosystem enclosures Large eddy sizes are controlled by the size of the generation apparatus, and they usually are much smaller than in nature Mismatched large eddy length scales and differences in turbulence generation mechanisms are responsible for the difficulties in mimicking natural turbulent mixing in experimental enclosures. The 2 most important turbulence parameters to consider in experimental ecosystem research are overall mixing time, T,,,, and turbulence dissipation rate, E. If the levels, spatial dlstribut~ons, and temporal variability of T,,, and E can be matched between an enclosure and the natural system it IS to model, then potential mixing artifacts can be minimized. An important additional consideration is that benthic ecosystems depend on the time-averaged boundary layer flow a s much as the turbulence. Existing designs for m i x~n g experimental ecosystems are capable of reasonably representing some aspects of natural turbulent mixing Paddle and grid stirring are the best available techniques for water column mixing, and flumes are best for benthic turbulence. There is no design at present that represents both environments adequately. More work also is needed on mixing of flexiblewall in situ enclosures. A more serious problem, however, is that turbulent mixing in experimental ecos)~stem studies too often is ignored, inadequately characterized, or unreported. Several methods are available for reasonable characterlzation of mixing in enclosures without sophisticated technology, and the technology for direct velocity measurements is becoming more accessible. Experimental ecosystem researchers should make a concerted effort to implement, characterize, and report on turbulent mixing In t h e~r enclosures.

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“…11). In contrast to the turbulence column described by Brunk et al (1996), the turbulence is not produced by single grids but with five pairs of oscillating grids driven by 10 individually controlled motors, respectively. The main difference to laboratory flumes or field studies is the possibility to produce turbulence without the action of shear, created by the mean flow.…”

Section: Particle Interaction In Open Channel Turbulencementioning

confidence: 93%

PIV measurements in environmental flows: Recent experiences at the Institute for Hydromechanics in Karlsruhe

Weitbrecht

Seol

Negretti

et al. 2011

Journal of Hydro-environment Research

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Particle-Image-Velocimetry (PIV) has been applied to many different environmental flows in the last twelve years at the Institute for Hydromechanics, Karlsruhe Institute of Technology. The present paper gives an overview about the most important results gained with PIV during this period and summarizes the advantages and disadvantages of this measurement technique. PIV applications to determine velocities at the water surface as well as internal flows characteristics are discussed with respect to physical and technical aspects. It can be concluded that PIV is still not a standard tool, every application needs adaptation and comprises certain limitations. Every element of the measurement system (window size, camera, spatial and temporal resolution, etc.) has to fit exactly the physical problem to be examined. Ó

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Modeling Natural Hydrodynamic Systems with a Differential-Turbulence Column

Cited by 24 publications

References 6 publications

Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

Turbulent mixing in experimental ecosystem studies

PIV measurements in environmental flows: Recent experiences at the Institute for Hydromechanics in Karlsruhe

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