Effects of Spacing and Geometry of Distributed Roughness Elements on a Two-Dimensional Turbulent Boundary Layer

Stewart, Devin

doi:10.21236/ada462101

Cited by 10 publications

(9 citation statements)

References 39 publications

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“…The effect of structures on flow properties depends on their size, spacing, geometry and density (Wooding et al 1973, Stewart 2005, Frostick et al 2014. Here, controlling for density and biomass (size and geometry) revealed that spatial arrangement had no effect on mean instantaneous velocities over reef surfaces, although under fast flow conditions (48 cm s −1 ), velocities over randomly arranged mussels were up to 3.1 × faster than instantaneous velocities over clumped mussels; a difference not apparent under slow flow conditions.…”

Section: Discussionmentioning

confidence: 99%

Spatial arrangement of biogenic reefs alters boundary layer characteristics to increase risk of microplastic bioaccumulation

Lim

Fraser

Knights

2020

Environ. Res. Lett.

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Microplastics are now synonymous with human impacts on the environment and as a threat to marine organisms. Numerous taxa are at risk from microplastics including commercially valuable bivalves as seafood, which are also disproportionately important as biogenic reef-forming species that enhance biodiversity such that they are commonly protected under conservation actions. As a sessile filter-feeding organism, bivalves are highly susceptible to microplastic ingestion but despite their socio-economic and ecological importance, no research has been undertaken to assess how a reef 's structural arrangement might affect plastic ingestion. Here, using a series of flume experiments, we examined how change in spatial arrangement of the blue mussel, Mytilus edulis, interacts with different flow speeds to effect retention of microplastic over reef surfaces and ingestion risk by individual mussels. Our results show that clumped spatial arrangements reduce boundary layer velocities, and increase turbulence, boundary layer thickness and plastic retention over reef surfaces under faster flow conditions, increasing plastic ingestion by 3-fold. Our findings suggest that the structural arrangement and rugosity of natural reef structures may create natural sinks of anthropogenic pollution, and species like Mytilus that are also important species for human consumption, while disproportionately susceptible to microplastic pollution, may be useful bioindicators of microplastic pollution.

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Section: Discussionmentioning

confidence: 99%

Spatial arrangement of biogenic reefs alters boundary layer characteristics to increase risk of microplastic bioaccumulation

Lim

Fraser

Knights

2020

Environ. Res. Lett.

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“…Bennington also studied the sweeping motion behind the element, the turbulent triple products, and made comparisons between elements with smooth edges and sharp edges. Stewart [20] and Varano [22] studied the effect of long fetches of sparsely spaced roughness elements. Stewart's roughness elements included…”

Section: Previous Researchmentioning

confidence: 99%

Structure of Turbulent Boundary Layers and Surface Pressure Fluctuations on a Patch of Roughness Elements

Rusche

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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I would like to thank my advisor, Dr. Roger Simpson, for his guidance and support throughout my M.S. program. His experience has taught me how to be a better researcher, and I am grateful for all of his help. I would also like to thank the other members of my committee, Dr. William Devenport and Dr. Joseph Schetz, for their input on my thesis and defense. I am grateful to my parents for their support throughout my education. Thank you to my friends and family for the encouragement to finish my graduate program. My fellow coworkers have helped me considerably throughout the past two years. Thank you to Andrew Hopkins, Nathaniel Varano, and Joe Derlaga for their assistance getting me up to speed with the DAQ systems. Thank you to Gwibo Byun for all of the little problems that he helped me out with. Thank you to Dr. Todd Lowe for being an excellent source of information as well as a great mentor. I also thank the entire Virginia Tech AOE department staff for their help in the office and machine shop.

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“…Further details about the seeding process can be found in Stewart (2005). These particles were injected in the wind tunnel upstream, right after the first contraction, before entering the test section.…”

Section: Third Generation Comprehensive Laser Doppler Velocimetermentioning

confidence: 99%

An Experimental Study of Turbulent Boundary Layers Subjected to High Free-Stream Turbulence Effects

Orsi¹

2005

Self Cite

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The work presented in this thesis was on nominally two-dimensional turbulent boundary layers at zero pressure gradient subjected to high free-stream turbulent intensities of up to 7.9% in preparations for high free-stream turbulence studies on three-dimensional boundary layers, which will be done in the future in the Aerospace and Ocean Engineering Boundary Layer Wind Tunnel at Virginia Tech. The two-dimensional turbulent flow that will impinge three-dimensional bodies needed to be characterized, before the three-dimensional studies can be made. An active turbulence generator designed to create high free-stream turbulence intensities in the wind tunnel was tested and modified in order to obtain the lowest possible mean flow non-uniformities. A sevenhole pressure probe was used to obtain planes of mean velocity measurements. A threecomponent state of the art laser-Doppler velocimeter (LDV) was used to obtain mean and fluctuating velocities. Previous high free-stream turbulence studies have been reviewed and are discussed, and some of the previously published data of other authors have been corrected. Based on the measurements obtained with the LDV, it was also determined that the semi-log law of the wall is valid for high free-stream turbulence cases, but with different constants than the ones proposed by Coles, where the constants for the high free-stream cases may be dependent on the turbulence intensity. For the first time, the skin friction coefficient (C f ) was deduced from the viscous sublayer. The difference between the U τ obtained in the viscous sublayer mean velocity profile and the U τ obtained in the semi-log layer from 2 τ U uv = − was 1.5%. The skin friction coefficient was determined to increase by 10.5% when the two-dimensional turbulent boundary layer was subjected to high free-stream turbulence effects. Spectral data obtained with the LDV, were compared to the von Kármán model spectrum and to the Pope's model spectrum, where the von Kármán spectrum was proven to fit the spectral data slightly better than the Pope's spectrum. Finally, the Hancock-Bradshaw-Blair parameter obtained for this experiment agreed very well with previously published data.

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Effects of Spacing and Geometry of Distributed Roughness Elements on a Two-Dimensional Turbulent Boundary Layer

Cited by 10 publications

References 39 publications

Spatial arrangement of biogenic reefs alters boundary layer characteristics to increase risk of microplastic bioaccumulation

Spatial arrangement of biogenic reefs alters boundary layer characteristics to increase risk of microplastic bioaccumulation

Structure of Turbulent Boundary Layers and Surface Pressure Fluctuations on a Patch of Roughness Elements

An Experimental Study of Turbulent Boundary Layers Subjected to High Free-Stream Turbulence Effects

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