Free Surface, Velocity Gradient Flow Past Hemisphere

Flammer, Gordon H.; Tullis, J. Paul; Mason, Earl S.

doi:10.1061/jyceaj.0002563

Cited by 28 publications

(5 citation statements)

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“…We see kinks in the data when the flow reaches the point where it encounters the top of The free-surface is the dynamic and turbulent surface of the rivers' flow, and therefore is affected by flow disturbing REs (Muraro et al, 2021). Flammer et al (1970) observed that as relative submergence increased, the flow transitions between three phases of pronounced, gradual and negligible free-surface effects. These free-surface effects are shown to be white water generating structures such as surface waves and riffles (Brocchini & Peregrine, 2001).…”

Section: Re Impact On Sub-aerial Soundmentioning

confidence: 78%

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The Influence of In‐Channel Obstacles on River Sound

Osborne

Hodge

Love

et al. 2022

Water Resources Research

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Section: Re Impact On Sub-aerial Soundmentioning

confidence: 78%

“…Flammer et al. (1970) observed that as relative submergence increased, the flow transitions between three phases of pronounced, gradual and negligible free‐surface effects. These free‐surface effects are shown to be white water generating structures such as surface waves and riffles (Brocchini & Peregrine, 2001).…”

Section: Discussionmentioning

confidence: 99%

The Influence of In‐Channel Obstacles on River Sound

Osborne

Hodge

Love

et al. 2022

Water Resources Research

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“…Neither Equations 2 or 3 have a dependence on the Froude number, but Flammer et al. (1970) showed that dra significantly increases with shallows due to particle surface wave effects, so one could argue that the presence of surface waves could impact the drag and lift forces that affect sediment entrainment and transport, but only in very shallow flows ( h / D < 1). Lamb et al.…”

Section: Methodsmentioning

confidence: 99%

“…where ρ is the density of water, u is the local velocity and the angle brackets denote a spatial average over A, the upstream facing surface area of the particle exposed to the flow, C D is a drag coefficient, and C L is the lift coefficient that must be estimated empirically (Lamb et al, 2008(Lamb et al, , 2017Schmeeckle et al, 2007;Wiberg & Smith, 1987). Neither Equations 2 or 3 have a dependence on the Froude number, but Flammer et al (1970) showed that dra significantly increases with shallows due to particle surface wave effects, so one could argue that the presence of surface waves could impact the drag and lift forces that affect sediment entrainment and transport, but only in very shallow flows (h/D < 1). Lamb et al (2017) explored how C D and C L are affected by relative submergence by directly measuring C D and C L in shallow flows and found that when the particles are not fully submerged, the C L is affected by surface waves.…”

Section: Experimental Designmentioning

confidence: 99%

Experiments on Gravel‐Sand Transitions: Behavior of the Grain Size Gap Material

Dingle,

Venditti

2023

JGR Earth Surface

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River bed sediments often lack fine gravel between 1 and 5 mm, a phenomenon referred to as the “grain size gap.” The gap corresponds to the rapid reduction in grain size associated with the gravel‐sand transition (GST), where median bed material grain size reduces from ∼10 mm gravel to ∼1 mm sand. Fine gravel grain sizes are often present in hillslope sediment, so it is not clear why they are absent on riverbed surfaces. We present a phenomenological laboratory experiment examining changes in sediment dynamics across a GST to examine the behavior of grain size gap material when included in the bed and feed grain size distributions. Our observations indicate that where sand falls out of washload, forming persistent surficial deposits at the GST, grain size gap material experiences enhanced mobility. This is due to hydraulic smoothing by sand that occurs because of a geometric effect, where medium sand bridges interstitial pockets in fine gravel bed surfaces. Our experiments show that gap gravel flux is enhanced by sand deposition, making gravel beds mobile at the threshold of motion. We are unable to maintain an immobile grain size gap gravel bed when sand is fed which explains why gravel beds composed of 1–5 mm particles are so rare on Earth. We hypothesize that in natural systems, grain size gap particles are either buried in the diffuse extension of GSTs or transported into coastal and marine environments where they are more commonly observed.

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“…Even though our approach is not derived from a rigorous physical analysis like that suggested by Flammer et al (1970), nothing about it is incompatible with known physics. Furthermore, such as reported in Mueller et al (2005), the process that drives bed load transport in gravel-and cobble-bed streams changes in several important ways as channel gradient increases, and for high slopes, there are also changes in flow structure (regime) that act independently of changes in sediment texture to alter transport thresholds (Sumer et al, 2003).…”

Section: Water Resources Researchmentioning

confidence: 99%

Analysis of Flow Resistance Equations in Gravel‐Bed Rivers With Intermittent Regimes: Calabrian fiumare Data Set

Mendicino

Colosimo²

2019

Water Resources Research

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This study addresses the evaluation of flow resistance in natural gravel‐bed rivers. Through a new data set collected on 136 reaches of 78 gravel‐bed rivers (Calabrian fiumare) in southern Italy, different conventional flow resistance equations to predict mean flow velocity in gravel‐bed rivers were tested in their original form. These equations have shown considerable disagreement with observed data, especially in river reaches characterized by high bed load conditions and for the domains of intermediate‐ and large‐scale roughness. This disagreement produced in almost all the cases an underestimation of the flow resistance, which can be corrected by introducing the Froude number and a particular form of the Shields sediment mobility parameter into the Manning, Chezy, and Darcy‐Weisbach equations. Through analyses carried out both on the whole data set and on its subsets, we propose a semiempirical approach with which, on the one hand, the tractive forces exerted by the flow on the bed are taken into account by considering the ratio between the sediment mobility parameter and its critical value, and on the other hand, water surface distortions are evaluated using the Froude number. This approach has been further validated using a literature‐based data set showing, even in this case, excellent performances. Finally, the literature‐based data set allowed us to improve the performances of the proposed approach in the field of large‐scale roughness. Efficiency tests indicate that the new equations can better reproduce the flow velocity in river reach where conventional flow resistance equations are not able to explain the entire dissipative process.

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Free Surface, Velocity Gradient Flow Past Hemisphere

Cited by 28 publications

References 0 publications

The Influence of In‐Channel Obstacles on River Sound

The Influence of In‐Channel Obstacles on River Sound

Experiments on Gravel‐Sand Transitions: Behavior of the Grain Size Gap Material

Analysis of Flow Resistance Equations in Gravel‐Bed Rivers With Intermittent Regimes: Calabrian fiumare Data Set

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