scholarly journals Flow fields, bed shear stresses, and suspended bed sediment dynamics in bifurcations of a large river

2012 ◽  
Vol 48 (11) ◽  
Author(s):  
R. N. Szupiany ◽  
M. L. Amsler ◽  
J. Hernandez ◽  
D. R. Parsons ◽  
J. L. Best ◽  
...  
Keyword(s):  
Flow Fields ◽  
Large River ◽  
Sediment Dynamics ◽  
Shear Stresses ◽  
Bed Sediment ◽  
Bed Shear Stresses

scholarly journals SEDIMENT DYNAMICS IN LAGOS HARBOUR - RECONNAISSANCE ON EFFECTS OF DREDGING

2012 ◽  
Vol 1 (33) ◽  
pp. 75 ◽  
Author(s):  
Thomas Vijverberg ◽  
Michiel Reneerkens ◽  
Han Winterwerp ◽  
Olaf Scholl ◽  
Y. Haruna
Keyword(s):  
Sediment Concentration ◽  
Sediment Dynamics ◽  
Sand Transport ◽  
Shear Stresses ◽  
Model Simulations ◽  
The Past ◽  
Bed Forms ◽  
Small Model ◽  
Maintenance Dredging ◽  
Bed Shear Stresses

Due to economic growth, Lagos Harbour is expanding. Capital dredging is needed to allow larger vessels to call the port. As harbour siltation is already a problem, increase of maintenance dredging is a worry. In the past no data was available to understand the hydraulics and sediment transport to estimate maintenance dredging volumes. This paper presents the reconnaissance of the sediment dynamics in the harbour, based on field data and MIKE21 model simulations. Measurements of sediment concentration, salinity and flow velocity show that estuarine circulation occurs, transporting sediment from the ocean into the port. However, more upstream in the Commodore channel, at the location where dredging will be carried out, this circulation is small. Model simulations show that at that location, bed shear stresses are large, also after dredging. Therefore, fine sediment can not accumulate in the deepened areas and this will not result in large dredging volumes. Sand transport however can cause sedimentation, as bed forms can migrate. These mechanisms are also observed in initial sand transport simulations, but need to be studied further to fully understand the sediment dynamics in the harbour.

scholarly journals Applying of depth-averaged hydrodynamic modeling with different methods of turbulence closure for flow near channel groyne. Part I – hydrodynamic background

2018 ◽  
Vol 23 ◽  
pp. 00009
Author(s):  
Ryszard Ewertowski
Keyword(s):  
Eddy Viscosity ◽  
Rectangular Channel ◽  
Simulation Models ◽  
Shear Stresses ◽  
Research Activity ◽  
Simulation Experiments ◽  
Hydrodynamic Simulation ◽  
Training Structures ◽  
Averaged Model ◽  
Bed Shear Stresses

Training structures in flow stream play an important role in shaping flow and bed properties. Planning to introduce such training elements like groins or dikes into the river stream one need to know consequences they may introduce into flow field and bed shear stresses. These consequences can be investigated by laboratory experiments on hydraulic models or by numerical modelling using hydrodynamic simulation models. In the paper the second possibility is exploited by applying two-dimensional depth-averaged model for straight rectangular channel with a groyne. This paper contains the first part of the research results and it describes hydrodynamic background of the flow phenomenon, concentrating on hydrodynamic equations for depth-averaged flow, types of eddy viscosity method used and kind of boundary conditions applied. Based on the hydrodynamic descriptions, different simulation experiments have been conducted for the flow problem and the whole analysis of simulation results for flow in channel near groyne is contained in the second part of the research activity (Part II = Analysis of simulation).

scholarly journals Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

2010 ◽  
Vol 2010 ◽  
pp. 1-22 ◽  
Author(s):  
Curt D. Peterson ◽  
Harry M. Jol ◽  
Tom Horning ◽  
Kenneth M. Cruikshank
Keyword(s):  
Shear Stresses ◽  
Before Present ◽  
Beach Ridge ◽  
Beach Ridges ◽  
Cobble Beach ◽  
Bed Shear Stresses ◽  
Beach Plain

The Seaside beach ridge plain was inundated by six paleotsunamis during the last ~2500 years. Large runups (adjusted >10 m in height) overtopped seawardmost cobble beach ridges (7 m elevation) at ~1.3 and ~2.6 ka before present. Smaller paleotsunami (6–8 m in height) likely entered the beach plain interior (4-5 m elevation) through the paleo-Necanicum bay mouth. The AD 1700 Cascadia paleotsunami had a modest runup (6-7 m height), yet it locally inundated to 1.5 km landward distance. Bed shear stresses (100–3,300 dyne cm−2) are estimated for paleotsunami surges (0.5–2 m depths) that flowed down slopes (0.002–0.017 gradient) on the landward side of the cobble beach ridges. Critical entrainment shear stresses of 1,130–1,260 dyne cm−2 were needed to dislodge the largest clasts (26–32 cm diameter) in paleotsunami coulees that were cut (100–200 m width) into the landward side of the cobble ridges.

scholarly journals Investigation of bed shear stresses subject to external turbulence

2003 ◽  
Vol 24 (6) ◽  
pp. 816-824 ◽  
Author(s):  
Nian-Sheng Cheng ◽  
B.Mutlu Sumer ◽  
Jørgen Fredsøe
Keyword(s):  
Shear Stresses ◽  
External Turbulence ◽  
Bed Shear Stresses

Model Studies at Mechanical Aortic Heart Valve Prostheses—Part I: Steady-State Flow Fields and Pressure Loss Coefficients

1988 ◽  
Vol 110 (4) ◽  
pp. 334-343 ◽  
Author(s):  
Martin Knoch ◽  
Helmut Reul ◽  
Ralf Kro¨ger ◽  
Gu¨nter Rau
Keyword(s):  
Heart Valve ◽  
Vortex Formation ◽  
Flow Fields ◽  
Turbulent Shear ◽  
Human Aorta ◽  
Shear Stresses ◽  
Scaled Model ◽  
Jude Medical ◽  
Heart Valve Prostheses ◽  
Valve Prostheses

In a 3:1 scaled model of the human aorta models of the Omniscience, Bjo¨rk-Shiley Convexo-Concave, Bjo¨rk-Shiley Monostrut, Medtronic-Hall, Duromedics (Hemex) and the Saint Jude Medical heart valve prostheses are studied in steady flow representing the systolic peak flow phase. Detailed flow visualization experiments show flow separations at all inner ring surfaces as well as at most of the occluders. The resulting stagnation areas increase the risk of thrombus accumulation. Flow separations also stimulate vortex formation and turbulent mixing at the downstream jet boundaries and thus may intensify blood damage by turbulent shear stresses. The different influences of struts and occluder guides on the flow around the occluders are discussed. The effects of the individual valve components on the flow fields are analyzed and correlated with the resulting pressure losses.

scholarly journals VESSEL WAKE INDUCED SEDIMENT MOBILITY AT EAGLE HARBOR, WASHINGTON, USA

2012 ◽  
Vol 1 (33) ◽  
pp. 58
Author(s):  
David Michalsen ◽  
Zeki Demirbilek ◽  
Okey Nwogu
Keyword(s):  
Puget Sound ◽  
Critical Shear Stress ◽  
Washington State ◽  
Shear Stresses ◽  
Difference Model ◽  
Stability Model ◽  
Sediment Mobility ◽  
Bed Stress ◽  
Passenger Ferry ◽  
Bed Shear Stresses

Eagle Harbor is a small natural harbor located in central Puget Sound on the eastern side of Bainbridge Island, Washington State, USA. Over a period of about 80 years, the harbor was severely contaminated. Approximately 28.3 hectares of the contaminated harbor were capped with dredged and upland sediments from 1993 to 2008. Recent monitoring data has concluded portions of the subtidal cap has eroded and may not be physically stable. Erosion in the vicinity of the car passenger ferry sailing line suggests the cap material may not be of sufficient size to achieve the objectives of providing a physical barrier for chemical isolation. Here, a two-dimensional finite difference model using a coupled Boussinesq-Panel method is used to investigate bed shear stresses on the existing sediment cap to analyze cap stability. Model results indicate the subtidal cap experiences over 100 Pa of bed stress within a 30 meter swath of the ferry sailing line. These bed stresses significantly exceed the critical shear stress of the original cap material indicating the cap is not physically stable.

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