scholarly journals Hydrodynamics of submerged vegetated alluvial channel with downward seepage

2017 ◽  
Vol 44 (3) ◽  
pp. 174-181 ◽  
Author(s):  
Thokchom Bebina Devi ◽  
Bimlesh Kumar
Keyword(s):  
Oryza Sativa ◽  
Flow Velocity ◽  
Reynolds Stress ◽  
Time Scales ◽  
Flow Conditions ◽  
Vegetation Zone ◽  
Flow Measurements ◽  
Downward Seepage ◽  
Alluvial Channel ◽  
Zone Centre

The flow conditions in a channel covered with fully submerged Oryza sativa has been investigated considering downward seepage. The flow measurements taken at the upstream free vegetation zone, centre of the vegetation zone, and downstream free vegetation zone will provide a better understanding regarding the flow hydrodynamics in a vegetated channel. The flow velocity, Reynolds stress, and turbulent intensities are reduced at the downstream vegetated section. Downward seepage increases the occurrence of streamwise flux along the length of the channel and vertical flux in the vertically downward direction. Integral length and time scales increase as the percentage of downward seepage increases.

Turbulence Characteristics of Vegetated Channel With Downward Seepage

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Thokchom Bebina Devi ◽  
Anurag Sharma ◽  
Bimlesh Kumar
Keyword(s):  
Reynolds Stress ◽  
Reynolds Shear Stress ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Distribution Functions ◽  
Quadrant Analysis ◽  
Reynolds Stresses ◽  
Vegetation Zone ◽  
Increase With Increase ◽  
Downward Seepage

Experimental studies were carried out for investigating changes in flow characteristics with the presence of flexible vegetation in a channel. The study focuses on the effect of introducing downward seepage on velocity profiles, Reynolds shear stress (RSS), and different turbulent length scales in a vegetative channel. The presence of vegetation provides drag and reduces the flow velocity. The turbulence generation mainly comes from the oscillations occurring near the top of the vegetation as is evident from the achievement of maximum Reynolds stress near the top of the vegetation. Application of downward seepage results in a higher velocity zone in the lower vegetation zone and a higher Reynolds stress. Quadrant analysis shows that sweep and ejection contribute most to Reynolds stress. The dominance of sweep event over ejection event is more with the application of downward seepage which means more bed transport. Different turbulent length and time scales increase with increase in downward seepage percentage due to reduction in energy dissipation. The increase in the length scale and time scale with downward seepage infers that higher level of turbulence prevail near the bed with an increased eddy size resulting in higher Reynolds stresses with downward seepage. The universal probability distribution functions (PDFs) of velocity fluctuations, RSS, and conditional RSS of vegetative channel follow Gram Charlier (GC) series based on exponential distribution except that a slight departure of inward and outward interactions of conditional RSS is observed which may be due to weaker events.

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

scholarly journals Spectroscopic Techniques versus Pitot Tube for the Measurement of Flow Velocity in Narrow Ducts

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7349
Author(s):  
Francesco D’Amato ◽  
Silvia Viciani ◽  
Alessio Montori ◽  
Marco Barucci ◽  
Carmen Morreale ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Velocity ◽  
Pitot Tube ◽  
Optical Measurements ◽  
Trace Gas ◽  
Dual Function ◽  
Spectroscopic Techniques ◽  
Gas Composition ◽  
Flow Conditions ◽  
Theoretical Simulation

In order to assess the limits and applicability of Pitot tubes for the measurement of flow velocity in narrow ducts, e.g., biomass burning plants, an optical, dual function device was implemented. This sensor, based on spectroscopic techniques, targets a trace gas, injected inside the stack either in bursts, or continuously, so performing transit time or dilution measurements. A comparison of the two optical techniques with respect to Pitot readings was carried out in different flow conditions (speed, temperature, gas composition). The results of the two optical measurements are in agreement with each other and fit quite well the theoretical simulation of the flow field, while the results of the Pitot measurements show a remarkable dependence on position and inclination of the Pitot tube with respect to the duct axis. The implications for the metrology of small combustors’ emissions are outlined.

scholarly journals A NEW FULLY-AUTOMATIC PROCEDURE FOR THE IDENTIFICATION AND THE COUPLING OF THE OVERTOPPING WAVES

2018 ◽  
pp. 36 ◽  
Author(s):  
Sara Mizar Formentin ◽  
Barbara Zanuttigh
Keyword(s):  
Flow Velocity ◽  
Water Surface ◽  
Automatic Identification ◽  
Practical Relevance ◽  
Threshold Values ◽  
Flow Conditions ◽  
Fully Automatic ◽  
The Individual ◽  
Coupling Algorithm ◽  
Submerged Conditions

This contribution presents a new procedure for the automatic identification of the individual overtopping events. The procedure is based on a zero-down-crossing analysis of the water-surface-elevation signals and, based on two threshold values, can be applied to any structure crest level, i.e. to emerged, zero-freeboard, over-washed and submerged conditions. The results of the procedure are characterized by a level of accuracy comparable to the human-supervised analysis of the wave signals. The procedure includes a second algorithm for the coupling of the overtopping events registered at two consecutive gauges. This coupling algorithm offers a series of original applications of practical relevance, a.o. the possibility to estimate the wave celerities, i.e. the velocities of propagation of the single waves, which could be used as an approximation of the flow velocity in shallow water and broken flow conditions.

Control of Hemorrhage in Critical Femoral or Inguinal Penetrating Wounds—An Ultrasound Evaluation

2006 ◽  
Vol 21 (6) ◽  
pp. 379-382 ◽  
Author(s):  
Michael Blaivas ◽  
Stephen Shiver ◽  
Matthew Lyon ◽  
Srikar Adhikari
Keyword(s):  
Flow Velocity ◽  
Abdominal Aorta ◽  
Femoral Artery ◽  
Iliac Artery ◽  
Common Femoral Artery ◽  
Body Armor ◽  
Mean Flow ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Ultrasound Evaluation

AbstractIntroduction:Exsanguination from a femoral artery wound can occur in sec-onds and may be encountered more often due to increased use of body armor. Some military physicians teach compression of the distal abdominal aorta (Abdominal Aorta) with a knee or a fist as a temporizing measure.Objective:The objective of this study was to evaluate if complete collapse of the Abdominal Aorta was feasible and with what weight it occurs.Methods:This was a prospective, interventional study at a Level-I, academ-ic, urban, emergency department with an annual census of 80,000 patients. Written, informed consent was obtained from nine male volunteers after Institutional Research Board approval. Any patient who presented with abdominal pain or had undergone previous abdominal surgery was excluded from the study. Subjects were placed supine on the floor to simulate an injured soldier. Various dumbbells of increasing weight were placed over the distal Abdominal Aorta, and pulsed-wave Doppler measurements were taken at the right common femoral artery (CFA). Dumbbells were placed on top of a tightly bundled towel roughly the surface area of an adult knee. Flow measurements at the CFA were taken at increments of 20 pounds. This was repeated with weight over the proximal right artery iliac and distal right iliac artery to eval- uate alternate sites. Descriptive statistics were utilized to evaluate the data.Results:The mean velocity through the CFA was 75.8 cm/ sec at 0 pounds. Compression of the Abdominal Aorta ranging 80 to 140 pounds resulted in no flow in the CFA. A steady decrease in mean flow velocity was seen starting with 20 pounds. Flow velocity decreased more rapidly with compression of the prox- imal right iliac artery, and stopped in all nine volunteers by 120 pounds of pressure. For all nine volunteers, up to 80 pounds of pressure over the distal iliac artery failed to decrease CFA flow velocity, and no subject was able to tolerate more weight at that location.Conclusion:Flow to the CFA can be stopped completely with pressure over the distal Abdominal Aorta or proximal iliac artery in catastrophic wounds. Compression over the proximal iliac artery worked best, but a first responder still may need to apply upward of 120 pounds of pressure to stop exsanguination.

Determination of the Flow Field in LP Steam Turbines

1986 ◽  
Author(s):  
J. Wachter ◽  
G. Eyb
Keyword(s):  
Flow Field ◽  
Measuring Equipment ◽  
Short Description ◽  
Test Stand ◽  
Steam Turbines ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Last Stage ◽  
The University

Up to now the determination of flow conditions across the entire circumference in LP steam turbines appears to be a difficult undertaking. The difficulties are mainly caused by the condensing medium steam and by the limited access to the stage from outside. The Last Stage Test Stand at the University of Stuttgart is a suitable facility for flow measurements in the LP part of steam turbines. Besides a short description of the test stand itself, the measuring equipment and the newly developed methods for data acquisition and evaluation are presented. Finally the flow field behind the last stage is shown and the results interpreted.

Effect of spark discharge energy scheduling on ignition under quiescent and flow conditions

2020 ◽  
Vol 234 (12) ◽  
pp. 2878-2891
Author(s):  
Zhenyi Yang ◽  
Xiao Yu ◽  
Hua Zhu ◽  
David S-K Ting ◽  
Ming Zheng
Keyword(s):  
Flow Velocity ◽  
High Power ◽  
Cross Flow ◽  
Spark Discharge ◽  
Discharge Process ◽  
Discharge Energy ◽  
Flow Conditions ◽  
Flame Kernel ◽  
Spark Plug ◽  
Spark Energy

The enhancement of the breakdown power during the spark discharge process has been proved to be beneficial for the flame kernel formation process under lean/diluted conditions. Such a strategy is realized by using a conventional transistor coil ignition system with an add-on capacitance in parallel to the spark plug gap in this paper. In practical application, the use of different ceramic material other than aluminum oxide can change the parasitic capacitance of the spark plug, achieving similar effect in terms of rescheduling the discharge energy released during the breakdown phase. Detailed research has been carried out to investigate the effect of the parallel capacitance and the cross flow velocity on the flame kernel formation and propagation process. With the increase in parallel capacitance, more spark energy is delivered during the breakdown phase, while less energy is released during the arc/glow phase. Shadowgraph images of the spark plasma reveal that the high-power spark discharge can generate a larger high-temperature area with enhanced electrically prompted turbulence under quiescent conditions, as compared with that using the conventional transistor coil ignition discharge strategy under the same condition. The breakdown enhanced turbulence of the high-power spark is proved to be beneficial for the flame kernel development, especially with the lean or exhaust gas recirculation diluted combustible mixtures, given that sufficient spark energy is available for the high-power spark strategy to successfully generate the breakdown event. The results of combustion tests under flow conditions reveal that the breakdown enhanced turbulence of the high-power spark tends to be overshadowed by the turbulence generated from the flow field, and both the increase in flow velocity and parallel capacitance contribute to the reduction in discharge duration of the arc/glow phase. Therefore, the benefits brought about by the high-power spark discharge tend to diminish with the intensification of flow velocity.

Meiofauna constitute a considerable portion of invertebrate drift among moss-rich patches within a karst hydrosystem

Biologia ◽  
2014 ◽  
Vol 69 (3) ◽  
Author(s):  
Mirela Perić ◽  
Tvrtko Dražina ◽  
Maria Špoljar ◽  
Ines Radanović ◽  
Biserka Primc ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Spatial Scale ◽  
Early Summer ◽  
Small Scale ◽  
Invertebrate Drift ◽  
Flow Conditions ◽  
Small Spatial Scale ◽  
Minor Influence ◽  
Drift Density ◽  
A Minor

AbstractAiming to establish the most frequent invertebrate taxa in drift at the small spatial scale within a moss-rich karst tufa-precipitating hydrosystem, we sampled drift among microhabitats differing in substratum type and flow conditions along a tufa barrier-cascading lotic reach. Additionally, we addressed the question of the contribution and the potential significance of meiofauna within the overall invertebrate drift at the small spatial scale. During the study period, a total of 60 invertebrate taxa were recorded in the drift. Six of these taxa belonged to the annelid/arthropod meiofauna and they represented 35% of total drift density. Macroinvertebrates found in drift were represented mainly by larval insects. The composition of the most abundant taxa in total drift was as follows: Alona spp. (Cladocera 26.7%), Riolus spp. (Coleoptera: Elmidae 13.2%), Simulium spp. (Diptera: Simuliidae 12.2%), Enchytraeidae (Oligochaeta 10.4%), Hydrachnidia (6.3%), Orthocladinae (Diptera: Chironomidae 3.9%) and Naididae (Oligochaeta 3.6%). Faunal drift densities and amounts of transported particulate matter (PM) were highest at the fast-flowing sites located at the barriers and lowest at the slow-flowing sites within pools. Similarly to the seasonal amounts of transported PM, faunal drift was lowest in winter, and peaked in autumn and in late spring/early summer. Correlation between flow velocity and PM-faunal drift densities suggested a significant effect of the dislodged PM, though a minor influence of discharge and flow velocity on faunal drift. We suggest that the small-scale habitat heterogeneity and the respective feeding and refugial strategies of the fauna, as well as faunal passive dislodgement initiated by the shear forces of the flow were the most important drivers of observed drift patterns.

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