scholarly journals DEVELOPMENT OP A SEDIMENT TRANSPORT MEASURING SYSTEM

1984 ◽  
Vol 1 (19) ◽  
pp. 139 ◽  
Author(s):  
Eberhard Renger
Keyword(s):  
Sediment Transport ◽  
Settling Tank ◽  
Sediment Flux ◽  
Measuring System ◽  
Time Interval ◽  
Automatic Instrument ◽  
Major Development ◽  
Shipping Traffic ◽  
Delivery Pipe ◽  
Measurement Location

A new method for continuously recording sediment concert - trations with high accuracy has been developed. It is proposed to apply the method for In-situ measurements in connection with investigations of tidal control and sediment transport induced by shipping traffic. The operating principle is as follows: at the measurement location, sedime~nt laden water is continuously sucked-in by means of a pump and is forced under pressure into a hydrocyclone ( solid bowl centrifuge ) through a delivery pipe of varying length. Here the extracted sediment flux (particle size *> 5 nm) is delivered by the shortest route to a settling tank and continuously weighed under water (wet-weighing). Following calculation and appropriate adjustment to the sample discharge ( Q ) the weight increase for selected time intervals ( AG (At)) yields the mean concentration for the time interval ( c (At)) in weight / unit volume ( mg/1 ) (direct measurement, calibration not required ). Details and experiences of the 3 major development stages will be described. A fully-automatic instrument for continuously measuring nonsteady sediment movement is now available. The instrument may be installed above as well as below water as desired.

Mass balance controls on sediment scour and bedrock erosion in waterfall plunge pools

Geology ◽  
2021 ◽  
Author(s):  
Joel S. Scheingross ◽  
Michael P. Lamb
Keyword(s):  
Sediment Transport ◽  
Mass Balance ◽  
River Discharge ◽  
Sediment Load ◽  
Sediment Flux ◽  
Habitat Availability ◽  
Flux Divergence ◽  
Plunge Pool ◽  
Bedrock Erosion ◽  
Recurrence Intervals

Waterfall plunge pools experience cycles of sediment aggradation and scour that modulate bedrock erosion, habitat availability, and hazard potential. We calculate sediment flux divergence to evaluate the conditions under which pools deposit and scour sediment by comparing the sediment transport capacities of waterfall plunge pools (Qsc_pool) and their adjacent river reaches (Qsc_river). Results show that pools fill with sediment at low river discharge because the waterfall jet is not strong enough to transport the supplied sediment load out of the pool. As discharge increases, the waterfall jet strengthens, allowing pools to transport sediment at greater rates than in adjacent river reaches. This causes sediment scour from pools and bar building at the downstream pool boundary. While pools may be partially emptied of sediment at modest discharge, floods with recurrence intervals >10 yr are typically required for pools to scour to bedrock. These results allow new constraints on paleodischarge estimates made from sediment deposited in plunge pool bars and suggest that bedrock erosion at waterfalls with plunge pools occurs during larger floods than in river reaches lacking waterfalls.

scholarly journals Theoretical Interpretation of the Exceptional Sediment Transport of Fine-grained Dispersal Systems Associated with Bedform Categories

2018 ◽  
Author(s):  
Tian Zhao ◽  
Qian Yu ◽  
Yunwei Wang ◽  
Shu Gao
Keyword(s):  
Sediment Transport ◽  
Regime Shift ◽  
Sedimentary Environment ◽  
Sediment Flux ◽  
Theoretical Interpretation ◽  
Fine Grained ◽  
Transport Regime ◽  
Source To Sink ◽  
Bed Roughness ◽  
Set Up

Abstract. Being a widespread source-to-sink sedimentary environment, the fine-grained dispersal system (FGDS) features remarkably high sediment flux, interacting closely with local morphology and ecosystem. Such exceptional transport is believed to be associated with changes in bedform geometry, which further demands theoretical interpretation. Using van Rijn (2007a) bed roughness predictor, we set up a simple numerical model to calculate sediment transport, classify sediment transport behaviors into dune and (mega-)ripple dominant regimes, and discuss the causes of the sediment transport regime shift linked with bedform categories. Both regimes show internally consistent transport behaviors, and the latter, associated with FGDSs, exhibits considerably higher sediment transport rate than the previous. Between lies the coexistence zone, the sediment transport regime shift accompanied by degeneration of dune roughness, which can considerably reinforce sediment transport and is further highlighted under greater water depth. This study can be applied to modeling of sediment transport and morphodynamics.

scholarly journals CALCULATION OF THE RATE OF NET ON-OFFSHORE SEDIMENT TRANSPORT ON THE BASIS OF FLUX CONCEPT

1984 ◽  
Vol 1 (19) ◽  
pp. 91 ◽  
Author(s):  
Ichiro Deguchi ◽  
Toru Sawaragi
Keyword(s):  
Sediment Transport ◽  
Water Depth ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Spatial Variations ◽  
Sediment Flux ◽  
Bed Load ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model

Time and spatial variations of sediment concentration of both bed load and suspended load in the process of two-dimensional beach deformation were investigated experimentally. At the same time, the relation between the velocities of water-particle and sediment migration was analyzed theoretically. By using those results,a net rate of on-offshore sediment_ transport in the process of two-dimensional model beach deformation qf was calculated on the basis of sediment flux. It is found that Qf coincides fairly well with .the net rate of on-offshore sediment transport calculated from the change of water depth.

Measurement of total respiratory impedance in infants by the forced oscillation technique

1991 ◽  
Vol 71 (2) ◽  
pp. 770-776 ◽  
Author(s):  
K. N. Desager ◽  
W. Buhr ◽  
M. Willemen ◽  
H. P. van Bever ◽  
W. de Backer ◽  
...  
Keyword(s):  
Forced Oscillation ◽  
Random Noise ◽  
Measuring System ◽  
Time Interval ◽  
Forced Oscillation Technique ◽  
Significant Difference ◽  
Before And After ◽  
Bias Flow ◽  
Sinusoidal Oscillations ◽  
Ventilatory Lung Function

The forced oscillation technique according to Landser et al. (J. Appl. Physiol. 41:101–106, 1976) was modified for use in infants. Adaptations, including a flexible tube to connect the infant to the measuring system and a bias flow to avoid rebreathing, did not influence impedance values. The linearity of the respiratory system was assessed and confirmed by 1) applying pseudo-random noise oscillations at three different amplitudes to 7 infants and 2) comparing in 12 infants impedance values obtained with pseudo-random noise and with sinusoidal oscillations at 12 and 32 Hz. Intersubject variability, averaged for all frequencies, was 6%. In 17 infants the relative error (+/- SD) between two series of five measurements within a time interval of 15 min was 0.5 +/- 5.7%. No statistically significant difference was found between impedance values before and after repositioning of the infant's head, whereas rotation resulted in a decrease in resistance and no effect on reactance. Our results indicate that the infant-adapted forced pseudo-random noise oscillation technique has the potential to give valuable information about ventilatory lung function in infants.

System Implications of the Ambulance Arrival-to-Patient Contact Interval on Response Interval Compliance

1994 ◽  
Vol 9 (4) ◽  
pp. 230-232 ◽  
Author(s):  
Jack P. Campbell ◽  
Matthew C. Gratton ◽  
Joseph A. Salomone ◽  
Daniel J. Lindholm ◽  
William A. Watson
Keyword(s):  
Response Time ◽  
Statistical Significance ◽  
Public Utility ◽  
Third Party ◽  
Measuring System ◽  
System Response ◽  
Time Interval ◽  
Patient Access ◽  
Time Intervals ◽  
Chi Square

AbstractBackground:Background: In some emergency medical services (EMS) system designs, response time intervals are mandated with monetary penalties for noncompliance. These times are set with the goal of providing rapid, definitive patient care. The time interval of vehicle at scene-to-patient access (VSPA) has been measured, but its effect on response time interval compliance has not been determined.Purpose:To determine the effect of the VSPA interval on the mandated code 1 (<9 min) and code 2 (<13 min) response time interval compliance in an urban, public-utility model system.Methods:A prospective, observational study used independent third-party riders to collect the VSPA interval for emergency life-threatening (code 1) and emergency nonlife-threatening (code 2) calls. The VSPA interval was added to the 9-1-1 call-to-dispatch and vehicle dispatch-to-scene intervals to determine the total time interval from call received until paramedic access to the patient (9-1-1 call-to-patient access). Compliance with the man dated response time intervals was determined using the traditional time intervals (9-1-1 call-to-scene) plus the VSPA time intervals (9-1-1 call-to-patient access). Chi-square was used to determine statistical significance.Results:Of the 216 observed calls, 198 were matched to the traditional time intervals. Sixty three were code 1, and 135 were code 2. Of the code 1 calls, 90.5% were compliant using 9-1-1 call-to-scene intervals dropping to 63.5% using 9-1-1 call-to-patient access intervals (p<0.0005). Of the code 2 calls, 94.1% were compliant using 9-1-1 call-to-scene intervals. Compliance decreased to 83.7% using 9-1-1 call-to-patient access intervals (p = 0.012).Conclusion:The addition of the VSPA interval to the traditional time intervals impacts system response time compliance. Using 9-1-1 call-to-scene compliance as a basis for measuring system performance underestimates the time for the delivery of definitive care. This must be considered when response time interval compliances are defined.

Self-organisation of morphology and sediment transport in alluvial rivers

2020 ◽  
Author(s):  
Eric Lajeunesse ◽  
Anais Abramian ◽  
Olivier Devauchelle
Keyword(s):  
Sediment Transport ◽  
Equilibrium Shape ◽  
Boltzmann Distribution ◽  
Physical Review ◽  
Bedload Transport ◽  
Sediment Flux ◽  
Sediment Discharge ◽  
Alluvial Rivers ◽  
Braided Rivers ◽  
Streamwise Streaks

&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;The coupling of sediment transport with the flow that drives it shapes the bed of alluvial rivers. The channel steers the flow, which in turns deforms the bed through erosion and sedimentation. To investigate this process, we produce a small river in a laboratory experiment by pouring a viscous fluid on a layer of plastic sediment. This laminar river gradually reaches its equilibrium shape. In the absence of sediment transport, the combination of gravity and flow-induced stress maintains the bed surface at the threshold of motion (Seizilles et al., 2013). If we impose a sediment discharge, the river widens and shallows to accommodate this input. Particle tracking reveals that the grains entrained by the flow behave as random walkers. Accordingly, they diffuse towards the less active areas of the bed (Seizilles et al., 2014). The river then adjusts its shape to maintain the balance between this diffusive flux, which pushes the grains towards the banks, and gravity, which pulls them towards the center of the channel. This dynamical equilibrium results in a peculiar Boltzmann distribution, in which the local sediment flux decreases exponentially with the elevation of the bed (Abramian et al., 2019). As the sediment discharge increases, the channel gets wider and shallower. Eventually, it destabilizes into multiple channels. A linear stability analysis suggests that it is diffusion that causes this instability, which could explain the formation of braided rivers (Abramian, Devauchelle, and Lajeunesse, 2019).&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Abramian, A., Devauchelle, O., and Lajeunesse, E., &amp;#8220;Streamwise streaks induced by bedload diffusion,&amp;#8221; Journal of Fluid Mechanics 863, 601&amp;#8211;619 (2019).&lt;/li&gt; &lt;li&gt;Abramian, A., Devauchelle, O., Seizilles, G., and Lajeunesse, E., &amp;#8220;Boltzmann distribution of sediment transport,&amp;#8221; Physical review letters 123, 014501 (2019).&lt;/li&gt; &lt;li&gt;Seizilles, G., Devauchelle, O., Lajeunesse, E., and M &amp;#769;etivier, F., &amp;#8220;Width of laminar laboratory rivers,&amp;#8221; Phys. Rev. E. 87, 052204 (2013).&lt;/li&gt; &lt;li&gt; &lt;p&gt;Seizilles, G., Lajeunesse, E., Devauchelle, O., and Bak, M., &amp;#8220;Cross-stream diffusion in bedload transport,&amp;#8221; Phys. of Fluids 26, 013302 (2014).&lt;/p&gt; &lt;/li&gt; &lt;/ul&gt;

Testing seismic noise caused by highly concentrated sediment flows in laboratory experiments

2020 ◽  
Author(s):  
Marco Piantini ◽  
Florent Gimbert ◽  
Alain Recking ◽  
Hervé Bellot
Keyword(s):  
Sediment Transport ◽  
Seismic Noise ◽  
Laboratory Experiments ◽  
River Flow ◽  
Mechanistic Model ◽  
Transport Processes ◽  
Sediment Flux ◽  
Extreme Floods ◽  
Starting Point ◽  
Grain Sorting

&lt;p&gt;Sediment transport processes and fluxes play a key role in fluvial geomorphology and hazard triggering. In particular, extreme floods characterized by highly concentrated flows set the pace of mountain landscape evolution, where the linkage between streams and sediment sources leads to strong solid inputs characterized by significant grain sorting processes. The main observation that river processes generate ground vibrations has led to the application of seismic methods for monitoring purposes, which provides an innovative system that overcomes traditional monitoring difficulties especially during floods. Mechanistic models have been proposed in the attempt to invert river flow properties such as sediment fluxes from seismic measurements. Although those models have recently been validated in the laboratory and in the field for low transport rates, it remains unknown whether they are applicable to extreme floods.&lt;/p&gt;&lt;p&gt;Here we carry a set of laboratory experiments in a steep (18% slope) channel in order to investigate the link between seismic noise and sediment transport under extreme flow conditions with highly concentrated sediment flows. The originality of this set-up is that instead of feeding the flume section directly as usually done, we feed with liquid and solid discharge a low slope storage zone connected to the upstream part of the steep channel. This allows us to produce sediment pulses of varying magnitude (up to the transport capacity) and granulometric composition, traveling downstream as a result of alternate phases of deposition and erosion occurring in the storage area. We measure flow stage, seismic noise, sediment flux and grain size distribution. We find that the previously proposed relationships between seismic power, sediment flux and grain diameter often do not hold in such sediment transport situations. We support that this is due to granular interactions occurring between grains of different sizes within the sediment mixture and leading to complex grain sorting processes. In particular, we observe that bigger grains do not directly impact the bed but rather roll over fines or smaller grains, such that observed seismic power is much lower than expected. These results constitute a starting point for the development of a new mechanistic model for seismic power generated by highly concentrated bedload sediment flows.&lt;/p&gt;

scholarly journals SEDIMENT TRANSPORT AT THE BOTTOM OF SEA WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 47
Author(s):  
Giovanna Vittori ◽  
Paolo Blondeaux
Keyword(s):  
Boundary Layer ◽  
Sediment Transport ◽  
Empirical Relationship ◽  
Temporal Distribution ◽  
Sediment Concentration ◽  
Sediment Flux ◽  
Sea Waves ◽  
Wall Boundary Layer ◽  
Sea Bottom ◽  
Local Water

The flow in the wall boundary layer generated close to the sea bottom by the propagation of a monochromatic surface wave is determined by considering small values of both the wave steepness and the ratio between the thickness of the boundary layer and the local water depth. Depending on the hydrodynamic conditions, the sea bottom can be plane or rippled. The geometrical characteristics of the bottom forms are predicted using empirical formulae and, then, the bedforms are assumed to behave as a bottom roughness, the size of which is related to the size of the ripples. The bottom boundary layer is assumed to be turbulent and the flow field is computed by means of a two-equation turbulence model. Then the sediment transport is evaluated. The bed load is obtained using an empirical relationship. The suspended load is determined by computing the sediment flux, once the spatial and temporal distribution of sediment concentration is determined. A comparison of the model findings with the experimental results supports the approach.

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