In situ observation of the water-sediment interface in combined sewers, using endoscopy

2003 ◽  
Vol 47 (4) ◽  
pp. 11-18 ◽  
Author(s):  
C. Oms ◽  
M.-C. Gromaire ◽  
G. Chebbo
Keyword(s):  
Shear Stress ◽  
Small Diameter ◽  
Organic Layer ◽  
In Situ Observation ◽  
Bed Shear Stress ◽  
Bed Sediment ◽  
Plastic Tube ◽  
Non Destructive ◽  
Sediment Interface

A new method for water-sediment interface observation has been designed. This system is based on a small diameter endoscope protected by a graduated plastic tube. It makes it possible to visualise in a non-destructive manner the sediments and the water-sediment interface. The endoscope was used to investigate Le Marais catchment (Paris): an immobile organic layer was observed at the water-sediment interface. This layer appears in pools of gross bed sediment, at the upstream of collectors, in zones where velocity is slow and where bed shear stress is less than 0.03 N/m2.

Bed shear stress estimation on an open intertidal flat using in situ measurements

2016 ◽  
Vol 182 ◽  
pp. 190-201 ◽  
Author(s):  
Q. Zhu ◽  
B.C. van Prooijen ◽  
Z.B. Wang ◽  
Y.X. Ma ◽  
S.L. Yang
Keyword(s):  
Shear Stress ◽  
In Situ Measurements ◽  
Intertidal Flat ◽  
Bed Shear Stress ◽  
Stress Estimation

scholarly journals Critical conditions of bed sediment entrainment due to debris flow

2004 ◽  
Vol 4 (3) ◽  
pp. 469-474 ◽  
Author(s):  
M. Papa ◽  
S. Egashira ◽  
T. Itoh
Keyword(s):  
Shear Stress ◽  
Debris Flow ◽  
Erosion Rate ◽  
Sediment Concentration ◽  
Critical Conditions ◽  
Bed Shear Stress ◽  
Bed Sediment ◽  
Sediment Size ◽  
Flume Tests ◽  
Sediment Entrainment

Abstract. The present study describes entrainment characteristics of bed material into debris flow, based on flume tests, numerical and dimensional analyses. Flume tests are conducted to investigate influences of bed sediment size on erosion rate by supplying debris flows having unsaturated sediment concentration over erodible beds. Experimental results show that the erosion rate decreases monotonically with increase of sediment size, although erosion rate changes with sediment concentration of debris flow body. In order to evaluate critical condition of bed sediment entrainment, a length scale which measures an effective bed shear stress is introduced. The effective bed shear stress is defined as total shear stress minus yield stress on the bed surface. The results show that critical entrainment conditions can be evaluated well in terms of Shields curve using the effective bed shear stress instead of a usual bed shear stress.

Nature and dynamic behaviour of organic surface layer deposits during dry weather

2005 ◽  
Vol 52 (3) ◽  
pp. 103-110 ◽  
Author(s):  
C. Oms ◽  
M.C. Gromaire ◽  
G. Chebbo
Keyword(s):  
Surface Layer ◽  
Dynamic Behaviour ◽  
Organic Layer ◽  
Combined Sewer Overflows ◽  
Temporal Scales ◽  
Spatial And Temporal Scales ◽  
Combined Sewer ◽  
In Situ Observations ◽  
Sediment Interface

In-situ observations were performed at two different spatial and temporal scales, in order to get a better identification of the nature of the organic layer situated at the water–sediment interface, and which had previously been identified as major of combined sewer overflows organic loads. Its composition and its build up mechanisms during dry weather periods are presented. Results showed that the concept of dry weather accumulation and more generally the way organic sewer sediments are modelled needs to be reconsidered.

Observation of plant roots in situ

1971 ◽  
Vol 49 (10) ◽  
pp. 1850-1852 ◽  
Author(s):  
J. Waddington
Keyword(s):  
Fiber Optics ◽  
Fiber Bundle ◽  
Small Diameter ◽  
Root Penetration ◽  
Image Transfer ◽  
Transparent Plastic ◽  
Plastic Tube ◽  
Made In

A technique is described which permits the determination of root penetration, distribution, and density with minimal disturbance to the plant. A small diameter tunnel is made in the soil and fitted tightly with a glass or transparent plastic tube. A fiber optics probe is used to observe the arrival of roots at the wall of the tube at various depths and to estimate their distribution and density. The probe consists of a light source and fiber bundle for illumination, a coherent fiber bundle for image transfer to the surface, a right angle viewing attachment at the objective end, and adjustable lenses.

scholarly journals Flume Experiments to Assess the Effect of Bottom Roughness, Temperature, Water Velocity and Oil Condition on Critical Shear Stress Estimates of Heavy Fuel Oil

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
MELISSA GLOEKLER ◽  
NANCY KINNER ◽  
TOM BALLESTERO ◽  
ESHAN DAVE
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Maximum Velocity ◽  
Water Velocity ◽  
Fuel Oil ◽  
Bed Shear Stress ◽  
Heavy Fuel Oil ◽  
Kaolinite Clay ◽  
Sunken Oil

Non-floating oil is challenging to detect, track, and recover due to limited visibility inhibiting verification of the oil's location and subsurface movement. Oil that sinks to the bottom (i.e., sunken oil) can form large mats or small agglomerates on the bottom, mix into sediments, or remobilize into the water column and move with currents potentially impacting shorelines, benthic and pelagic organisms, intakes for drinking water, and power plants. Trajectory models exist that predict movement of floating and submerged oil; however, many models cannot accurately address sunken oil movement because the bed shear stress (BSS) necessary to mobilize oil (i.e., critical shear stress (CSS)), neglects the effects of bottom roughness and assumes an immobile bed. The goal of this research is to provide responders and modelers with more precise CSS estimates that include the effect of bottom roughness and incorporate results into a response tool to predict sunken oil movement. The transport of oil depends upon in-situ environmental conditions and oil properties. This research used the Coastal Response Research Center's (CRRC) 2180-liter straight flume to test the effects of water velocity, water temperature, oil mass, and bottom friction on fresh and weathered No. 6 Heavy Fuel Oil (HFO) on an immobile boundary. The flume's test section provided a uniform, one-dimensional flow field measured in 3D by an acoustic Doppler velocimeter (ADV), a Nortek AS (Norway) Vectrino II Profiling Velocimeter. The fresh or weathered (%Ev=5) HFO was mixed with kaolinite clay as a sinking agent, and 100 grams of the mixture was injected into static water via subsurface injection. The water velocity was incrementally increased in a stepwise manner by 0.07 m/s intervals and held for 15 minutes at each velocity. This occurred until: (1) oil had stopped eroding or was completely eroded from the substrate, or (2) the maximum velocity of 1.04 m/s was reached. Bottom roughness was evaluated using the velocity profile and bed shear stress (BSS) was calculated using multiple methods applicable to lab and field conditions. The oil's behavior was documented by downward- and side-facing GoPro cameras and reviewed to estimate mass loss per velocity interval, the distance the oil migrated along the bottom, and the corresponding CSS. In the case of an oil spill, responders can compare CSS estimates, determined through this research, with in-situ BSS estimates predicting under what conditions the sunken oil will become mobile.

scholarly journals Strength and fracture of Si micropillars: A new scanning electron microscopy-based micro-compression test

2007 ◽  
Vol 22 (4) ◽  
pp. 1004-1011 ◽  
Author(s):  
B. Moser ◽  
K. Wasmer ◽  
L. Barbieri ◽  
J. Michler
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Small Diameter ◽  
In Situ Observation ◽  
Compression Tests ◽  
Strain Measurements ◽  
Pillar Diameter ◽  
Novel Method ◽  
Scanning Electron

A novel method for in situ scanning electron microscope (SEM) micro-compression tests is presented. The direct SEM observation during the instrumented compression testing allows for very efficient positioning and assessment of the failure mechanism. Compression tests on micromachined Si pillars with volumes down to 2 μm3are performed inside the SEM, and the results demonstrate the potential of the method. In situ observation shows that small diameter pillars tend to buckle while larger ones tend to crack before failure. Compressive strength increases with decreasing pillar diameter and reaches almost 9 GPa for submicrometer diameter pillars. This result is in agreement with earlier bending experiments on Si. Difficulties associated with precise strain measurements are discussed.

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