Channel geometry, bed material, and inferred flow conditions in ephemeral stream systems, barrier range, western N.S.W. Australia

1992 ◽  
Vol 6 (4) ◽  
pp. 417-433 ◽  
Author(s):  
D. L. Dunkerley
Keyword(s):  
Flow Conditions ◽  
Ephemeral Stream ◽  
Channel Geometry ◽  
Bed Material ◽  
Stream Systems

Experimental Investigation of Mixing in a T-Channel for Asymmetric Inlet Conditions

2012 ◽  
Author(s):  
Manjunath Basavarajappa ◽  
John Elsnab ◽  
Susan Thomas ◽  
Timothy A. Ameel
Keyword(s):  
Experimental Investigation ◽  
Volumetric Flow Rate ◽  
Flow Regimes ◽  
Laser Induced Fluorescence ◽  
Flow Conditions ◽  
Inlet Channel ◽  
Outlet Channel ◽  
Channel Geometry ◽  
Planar Laser ◽  
Inlet Conditions

An experimental investigation of water flow in a rectangular T-channel with inner dimensions of 20 × 20 mm (inlet channel) and 20 × 40 mm (outlet mixing channel) has been conducted. The inlet Reynolds number Re, based on inlet hydraulic diameter, ranged from Re1 = 90 to 775. Inlet flow conditions were asymmetric, and inlet Re ratios of Re1/Re2 = 1.24, 1.65 and 2.45 were obtained by varying volumetric flow rate. Dynamical conditions and T-channel geometry are directly applicable to microscale mixing. Planar laser induced fluorescence (LIF) was used to characterize flow regimes and behaviors, including periodicity, in the inlet and outlet channels. Two distinct flow regimes were identified and characterized for asymmetric inlet Re. For low inlet Re, Re1 ≤ 150, and all Re1/Re2, flows were steady. For higher Re and all Re1/Re2, a jet flow regime, characterized by two counter rotating vortices and increasingly turbulent at higher Re dominated the flow in the junction. Qualitative mixing characteristics for all flow regimes, based on LIF visualizations in the outlet channel, are also presented.

scholarly journals Characterising groundwater–surface water interactions in idealised ephemeral stream systems

2020 ◽  
Vol 34 (18) ◽  
pp. 3792-3806
Author(s):  
Edisson A. Quichimbo ◽  
Michael B. Singer ◽  
Mark O. Cuthbert
Keyword(s):  
Surface Water ◽  
Ephemeral Stream ◽  
Stream Systems

scholarly journals Morphodynamic effects of stone and wooden groynes in a restored river reach

2018 ◽  
Vol 40 ◽  
pp. 02038
Author(s):  
Bahaeldeen Zaid ◽  
Paride Nardone ◽  
Michael Nones ◽  
Christoph Gerstgraser ◽  
Katinka Koll
Keyword(s):  
Morphological Structure ◽  
Normal Flow ◽  
Flow Conditions ◽  
Bed Topography ◽  
Different Types ◽  
Fish Spawning ◽  
River Reach ◽  
Bed Material ◽  
Spree River ◽  
Flow Velocities

Restoration works on an 11 km long reach of the Spree River near Cottbus in Germany were accomplished in 2014. The overall objective was to improve the biodiversity, changing the morphological structure from a straight single-thread river to a braiding one with reshaped thalweg, and creating zones with varying flow velocities required for fish spawning. Several interventions were made, among which also two types of groynes were constructed along the reach: impermeable stone groynes, with an inclined crest so that only the tip is typically submerged during normal flow conditions, and wooden groynes made of several large trunks, which are mainly submerged at normal flow conditions. To compare local morphodynamic effects caused by the different types, flow velocities and bed topography were measured at distances of 12 m upstream and 16 m downstream of two selected groynes. The vertical profile was captured by measuring at five levels above the bed. Bed material was sampled at several locations around the groynes. The analysis of the measurements showed the effect of each groyne type on the flow velocity, bed topography and bed material. Furthermore, the differences in the effects of each groyne type on the flow, bed topography and bed material were highlighted.

scholarly journals Effect of Pressure Fluctuations and Flow Confinement on Shear Stress in Jet-Driven Scour Processes

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 718 ◽  
Author(s):  
Simone Pagliara ◽  
Michele Palermo
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Pressure Fluctuations ◽  
Flow Conditions ◽  
Effect Of Pressure ◽  
Black Water ◽  
Stress Coefficient ◽  
Average Shear ◽  
Confined Environment ◽  
Bed Material

The effect of pressure fluctuations and flow confinement on shear stress still represents a challenging problem for hydraulic engineers. Only a few studies investigated such aspects, but they did not focus on jet-driven scour processes in granular bed material. Following a recent theoretical framework, this paper presents a novel analytical procedure to assess the effect of pressure fluctuations on the average shear stress for 2D equilibrium configuration, under steady, black water flow conditions. The analysis of experimental data evidences that published formulas underestimate the maximum shear stress, because of the significant flow confinement and the presence of rotating material in the scour hole. Therefore, based on the hydrodynamic similitude characterizing the jet diffusion in a confined environment, a new shear stress coefficient and a novel equation are proposed to estimate the maximum shear stress for the tested configuration.

scholarly journals Mud in sandy riverbed deposits as a proxy for ancient fine-sediment supply

Geology ◽  
2021 ◽  
Author(s):  
N. Wysocki ◽  
E. Hajek
Keyword(s):  
Fine Sediment ◽  
Sediment Supply ◽  
Primary Control ◽  
Flow Conditions ◽  
Sediment Retention ◽  
Channel Networks ◽  
High Discharge ◽  
River Deposits ◽  
Series Of Experiments ◽  
Bed Material

The amount of silt and clay available to rivers reflects source-terrain composition and weathering and can be a primary control on the form and dynamics of channel networks. Fine sediment also affects the permeability of buried fluvial reservoirs. Despite this significance, there is currently a lack of methods for reconstructing how much fine sediment was transported by ancient rivers. Mud accumulations in sandy river deposits are often interpreted as indicators of variable flow conditions; however, these deposits may present an opportunity to constrain how much fine sediment was transported through ancient rivers. We report results from a series of experiments designed to evaluate how much clay and silt are preserved in sandy riverbed deposits under constant and variable discharge conditions. Our results demonstrate that (1) mud deposits, including drapes and lenses, form readily under constant, high-discharge conditions, (2) the amount of fine sediment recovered from bed-material deposits increases as fine-sediment supply increases, and (3) fine-sediment retention is higher during bed aggradation than during bypass conditions. These results indicate that the net retention of clay and silt in sandy riverbed deposits may be a simple but powerful proxy for comparing the overall amount of fine sediment supplied to ancient rivers.

Fluvial reservoirs in dryland endorheic basins: the Lake Eyre Basin as a world-class modern analogue

2014 ◽  
Vol 54 (1) ◽  
pp. 119 ◽  
Author(s):  
Sara Morón ◽  
Kathryn Amos ◽  
Sandra Mann
Keyword(s):  
Grain Size ◽  
Single Channel ◽  
Hydrocarbon Exploration ◽  
Geological Time ◽  
Fluvial Systems ◽  
Channel Geometry ◽  
Modern Analogue ◽  
Exploration And Production ◽  
Hydrocarbon Exploration And Production ◽  
Bed Material

Intracratonic dryland basins have been common throughout geological time and significant hydrocarbon reservoirs are contained in these basins. Based on a literature compilation of fluvial dryland reservoirs, the authors demonstrate the need for new modern analogue data from dryland fluvial systems, and present new field data from the Neales River, in the Lake Eyre catchment. The selected study reach has a complex planform, with a downstream transition from single channel to anabranching. Results of the observations of the channel bed grain size, the geomorphology and the channel geometry (width and depth) allow the authors to infer that the channel bed grain size is more strongly related to planform geomorphology than the channel geometry (width to depth ratios). Based on the grain size and channel geometry data the authors present, the authors conclude that the planform geomorphology exerts a greater control on channel bed material size than channel geometry. This interpretation is based on the analysis of satellite imagery, topographic survey data and grain size descriptions. In this paper, the authors provide channel geometry data and grain size data that will improve understanding of dryland fluvial sedimentology. The authors hope this contributes to enhancing hydrocarbon exploration and production in petroleum reservoirs developed in dryland fluvial settings.

Modeling (partly) cohesive sediment transport in sewer systems

1996 ◽  
Vol 33 (9) ◽  
pp. 171-178 ◽  
Author(s):  
Jean E. Berlamont ◽  
Hilde M. Torfs
Keyword(s):  
Sediment Transport ◽  
Circular Cross Section ◽  
Flow Conditions ◽  
Transport Models ◽  
Rectangular Section ◽  
Sewer Systems ◽  
Cohesive Sediment Transport ◽  
The Many ◽  
Bed Material ◽  
Cohesive Bed

Although the basic mechanisms of sediment transport in sewers are the same as in rivers, it is not necessarily appropriate to use the many models that have been developed for sediment transport in rivers also in sewers. Different reasons are: 1) sewer sediments are often mixtures of cohesive and non cohesive material, and the bed is often stratified; 2) due to consolidation of the (partly cohesive) bed material, the erosion resistance of the bed may vary with time; 3) the flow conditions in sewers are usually unsteady, which is not accounted for in the classical sediment transport models; 4) existing models have been derived from experiments in rectangular flumes: the results are not directly applicable to sewers with circular cross section where the distribution of bed shear stress may be completely different from a rectangular section; 5) the limited availability of erodible material and the varying supply of sediments add additional difficulty to the modelling of sediment transport in sewers.

scholarly journals An Evaluation of Data Collected by Middle School and College-Level Students in Stream Channel Geomorphic Assessment

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Martin D. Lafrenz
Keyword(s):  
Middle School ◽  
Cross Sections ◽  
Stream Velocity ◽  
College Level ◽  
Stream Channel ◽  
Channel Geometry ◽  
Student Groups ◽  
Portland State University ◽  
Bed Material ◽  
Accuracy And Repeatability

This project tested the accuracy and repeatability of geomorphic stream channel assessments conducted by two different middle school classes from the Walt Morey Middle School in Troutdale, OR and college students from Portland State University in Portland, OR. Each group surveyed the same three cross-sections in Fairview Creek, a tributary to the Lower Columbia River, in order to assess stream channel geometry, discharge, composition of the bed material, and water quality. The three student groups were all able to accurately document the stream channel geometry, including stream width and mean depth, indicating that these data can be successfully collected by volunteers of various ages. However, stream velocity obtained using the float method was consistently overestimated leading to a biased calculation of discharge, and the low precision of the measurements did not allow for a correction of the bias. The median particle size of the bed material determined by a pebble count was also overestimated by each group, but the low precision also negated the possibility of correcting the estimate. The stored fine sediment in the bed was underestimated by each group and again with low precision. The temperature, pH, and conductivity measured with a calibrated multimeter were accurate and precise for all groups.

Thrombus formation on artificial surfaces: Correlative microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 840-841
Author(s):  
Quintin J. Lai ◽  
Stuart L. Cooper ◽  
Ralph M. Albrecht
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Low Voltage ◽  
Thrombus Formation ◽  
Blood Platelets ◽  
Polymer Surfaces ◽  
Flow Conditions ◽  
Transmission Electron ◽  
Adhesion Of Platelets ◽  
Microscopic Techniques

Thrombus formation and embolization are significant problems for blood-contacting biomedical devices. Two major components of thrombi are blood platelets and the plasma protein, fibrinogen. Previous studies have examined interactions of platelets with polymer surfaces, fibrinogen with platelets, and platelets in suspension with spreading platelets attached to surfaces. Correlative microscopic techniques permit light microscopic observations of labeled living platelets, under static or flow conditions, followed by the observation of identical platelets by electron microscopy. Videoenhanced, differential interference contrast (DIC) light microscopy permits high-resolution, real-time imaging of live platelets and their interactions with surfaces. Interference reflection microscopy (IRM) provides information on the focal adhesion of platelets on surfaces. High voltage, transmission electron microscopy (HVEM) allows observation of platelet cytoskeletal structure of whole mount preparations. Low-voltage, high resolution, scanning electron microscopy allows observation of fine surface detail of platelets. Colloidal gold-labeled fibrinogen, used to identify the Gp Ilb/IIIa membrane receptor for fibrinogen, can be detected in all the above microscopies.

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