scholarly journals An Experimental Study on the Influence of Drastically Varying Discharge Ratios on Bed Topography and Flow Structure at Urban Channel Confluences

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1147
Author(s):  
Zhiyuan Zhang ◽  
Yuqing Lin
Keyword(s):  
Transition Period ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
River Network ◽  
Morphological Alteration ◽  
Minor Role ◽  
Material Transport ◽  
Lateral Velocity ◽  
Basic Work ◽  
Discharge Ratio

The confluences of rivers are important nodes for energy conversion and material transport in the river network. A slight morphological alteration of the confluences may trigger the “butterfly effect”, which will bring about changes in the ecology and environment of the entire river network. During the transition period of the wet and dry seasons, the variation of discharge ratio will make the originally balanced river bed change again, which will bring a series of follow-up effects. This research mainly studied the features of water flow itself and results showed that the variation of discharge ratio caused secondary erosion of the balanced bed surface and transported the sediment downstream. Thus, the zone of maximum velocity was enlarged and the maximum flow velocity at the equal discharge was reduced, and more intense vortex and turbulence were generated. The lateral velocity, vertical velocity, and turbulent structure were mainly controlled by the quantity and ratio of the discharge, and the varying topography only played a minor role in local areas. Nowadays, some scholars have been studying the combination of flow field features and various environmental substances and biological habitats, and the basic work done in this article has laid the foundation for these studies.

Effect of shielding gas flow rate on arc behaviors in GMAW with single cable-typed wire

2019 ◽  
Vol 34 (01n03) ◽  
pp. 2040059
Author(s):  
Qingxian Hu ◽  
Lei Zhang ◽  
Juan Pu ◽  
Caichen Zhu
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Gas Metal Arc Welding ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Maximum Pressure ◽  
Arc Plasma ◽  
Shielding Gas ◽  
Gas Flow Rate

A three-dimensional numerical model of arc in gas metal arc welding (GMAW) with single cable-typed wire was established based on the theory of arc physics. The influences of different shielding gas flow rates on the features of temperature field, velocity field and pressure field were investigated. The results showed that the maximum velocity of arc plasma along radial direction and the arc pressure on the surface of workpieces were increased obviously with the increase of the shielding gas flow rate, while the arc temperature was changed little. This phenomenon was mainly attributed to the increasing collisions between arc plasmas and the self-rotation action of cable-typed wires. The arc temperature at the tip of the cable-typed wire reached the maximum. The maximum flow velocity of arc plasma was located at the tip of wire (2–8 mm). The arc pressures in the central axis reached the maximum pressure. The simulation results were in agreement with the experimental results.

scholarly journals Pressure and Water Flow Patterns in the Respiratory Tract of the Bass (Micropterus Salmoides)

1984 ◽  
Vol 113 (1) ◽  
pp. 151-164 ◽  
Author(s):  
GEORGE V. LAUDER
Keyword(s):  
Respiratory Tract ◽  
Flow Velocity ◽  
Buccal Cavity ◽  
Micropterus Salmoides ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Wave Form ◽  
Dimensional Changes ◽  
Velocity Wave ◽  
Phase Differences

Instantaneous water velocities in the respiratory tract of bass, Micropterus salmoides (Lacepéde), were measured using a fast-responding hot-filmanemometer. The flow velocity wave form varied within the buccal cavity, with lower peak velocities at the back than at the front. Flow velocity in both the buccal and opercular cavities varied over the respiratory cycle, and 80% of signal power in the velocity wave form was between 1 and 10 Hz. Flow within the buccal cavity reached a maximum velocity of 50cms−1 and did not decline to zero, even when differential pressure across the gills was negative. Simultaneous measurement of dimensional changes in the branchial apparatus, pressure and velocity fluctuations showed that gill bar adduction coincides both with the pressure reversal across the gills and with maximum flow velocities in the opercular cavity. The movement of the gillbars during respiration causes flow velocity fluctuation just in front of the primary lamellae and may be an important component of intraoral resistance contributing to the phase differences between pressure and velocity waveforms.

scholarly journals Field measurements of wake meandering at a utility-scale wind turbine with nacelle-mounted Doppler LiDARs

2021 ◽  
Author(s):  
Peter Andreas Brugger ◽  
Corey D. Markfort ◽  
Fernando Porté-Agel
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Wind Farm ◽  
Maximum Velocity ◽  
Field Measurements ◽  
Lateral Velocity ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Downstream Distance ◽  
Utility Scale

Abstract. Wake meandering is a low-frequency oscillation of the entire wind turbine wake that can contribute to power and load fluctuations of downstream turbines in wind farms. Field measurements of two Doppler LiDARs mounted on the nacelle of a utility-scale wind turbine were used to investigate relationships between the inflow and the wake meandering as well as the effect of wake meandering on the temporally averaged wake. A correlation analysis showed a linear relationship between the instantaneous wake position and the lateral velocity that degraded with the evolution of the turbulent wind field during the time of downstream advection. A low-pass filter proportional to the advection time delay is recommended to remove small scales that become decorrelated even for distances within the typical spacing of wind turbine rows in a wind farm. The results also showed that the velocity at which wake meandering is transported downstream was slower than the inflow wind speed, but faster than the velocity at the wake center. This indicates that the modelling assumption of the wake as an passive scalar should be revised in the context of the downstream advection. Further, the strength of wake meandering increased linearly with the turbulence intensity of the lateral velocity and with the downstream distance. Wake meandering reduced the maximum velocity deficit of the temporally averaged wake and increased its width. Both effects scaled with the wake meandering strength. Lastly, we found that the fraction of the wake turbulence intensity that was caused by wake meandering decreased with downstream distance contrary to the wake meandering strength.

scholarly journals Bulk scaling of flow characteristics in the interior of sparse, emergent and rigid vegetation patch

2018 ◽  
Vol 40 ◽  
pp. 02026
Author(s):  
Soumen Maji ◽  
Prashanth Reddy Hanmaiahgari
Keyword(s):  
Linear Equations ◽  
Flow Characteristics ◽  
Maximum Velocity ◽  
Local Maximum ◽  
Streamwise Velocity ◽  
Mean Flow ◽  
Lateral Velocity ◽  
Measuring Point ◽  
River Bank ◽  
Vegetation Patch

Vegetation has an important role on erosion and sedimentation of rivers, river bank and marshy lands, etc. This effect depends on type of flow characteristics present in a vegetation patch. However, it’s a great challenge to find out the flow characteristics in the interior of vegetation patch. The objective of this study is to determine the appropriate scaling of flow characteristics throughout the interior of an emergent and sparse vegetation patch for a given flowrate and depth, which can be used to predict the flow field in a similar vegetation conditions. In this study uniform acrylic cylinders were planted in a structured array to create a vegetation patch. Two different flow conditions by varying aspect ratio for a given Reynolds number were used in this laboratory study. Nortek ADV was used for measuring point velocities in the interior of the vegetation patch. Mean flow and turbulence quantities at all the measuring locations in the interior of the patch were scaled appropriately so that they collapse on a single curve. The local maximum velocity is found to be an appropriate scaling parameter for normalizing the streamwise velocity profiles, further the scaled velocity in the interior of the patch found to be following a power law. Lateral and vertical velocities in the interior of the patch are appropriately scaled by velocity vector across the section. Average bulk lateral velocity and scaled shear stress in a sparse and emergent vegetation patch can be described by linear equations in terms of scaled depth.

scholarly journals PENGARUH PILAR JEMBATAN PANGO TERHADAP POLA ALIRAN SUNGAI KRUENG ACEH

2018 ◽  
Vol 1 (4) ◽  
pp. 1005-1018
Author(s):  
Teuku Devansyah Putra ◽  
Eldina Fatimah ◽  
Azmeri Azmeri
Keyword(s):  
Flow Velocity ◽  
Flow Pattern ◽  
Cross Section ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Surface Water Modeling ◽  
River Cross Section ◽  
Maximum Flow Velocity ◽  
Banda Aceh ◽  
River Bend

Abstract: Pango Fly Over is located in the coordinate of 50 32' 07.32" LU (North Latitude) and 950 20' 52.90” BT (East Longitude) on Pango Village, Ulee Kareng Sub District, Banda Aceh. This bridge was built across Krueng Aceh River and the pillars were built in the river so that it narrows the river cross section and affecting the increasing of flow velocity. From the research location observation, it is found that the bridge pillars cause the more narrowing of the river cross section and there is the damage of the riverbank around the river bend located in the downstream of the pillars. If there is no further follow up, it will erode the national road. This research aims to find out flow pattern without and with the pillars, and to know the flow pattern behavior in the river bend. This research uses Surface Water Modeling System (SMS Version 11.2) Program. The length of the river reviewed is ± 500 meters. The flow discharge used in this research is the flood discharge which the period is Q – 100 and the value is 627.74 m³/second (passing the Pango Fly Over). From the result of the flow patter simulations, it is obtained that the maximum flow velocity without the pillars found in the middle location of V3 reviewed point on the distance 45 m from the riverbank is 0.45 m/sec and maximum flow velocity with the pillars found in the middle location of V3 reviewed point on the distance 33 m from the riverbank is 0.35/sec. In the outer bend of the flow pattern simulation result without pillars, it is obtained that the maximum velocity found in V6 reviewd location on the distance 50 m is 0.83 m/sec in the left side of the flow.Meanwhile in the downstream of the bend, the maximum velocity wit the bridge pillars found in V6 reviewd location on the distance 50 m is 0.95 m/det in the left side of the flow. In the bridge pillars downstream location, there is the river bend required the riverbank reinforcement and the riverbed reinforcement in order to avoid the erosion in the riverbank, because it will endanger the public facilities. Abstrak: Jembatan fly over Pango berada pada koordinat  50 32' 07.32" LU dan 950 20' 52.90” BT terletak di desa Pango Kecamatan Ulee Kareng kota Banda Aceh. Jembatan ini di bangun melintang Sungai Krueng Aceh dan pilar jembatan dibangun pada sungai sehingga terjadi penyempitan penampang sungai yang menyebabkan kecepatan aliran bertambah, Dari tinjauan lokasi penelitian pilar jembatan semakin mengalami penyempitan penampang sungai dan terjadi kerusakan tebing di sekitar belokan sungai yang berada di hilir jembatan. Bila tidak segera di tindak lanjuti akan berdampak tergerusnya jalan nasional. Penelitian ini bertujuan untuk mengetahui pola aliran tanpa adanya pilar dengan adanya pilar serta untuk mengetahui perilaku pola aliran yang terjadi pada belokan sungai. Penelitian ini menggunakan program Surfacewater Modeling System (SMS. Versi 11.2). Panjang sungai yang di tinjau ± 500 meter. Debit aliran yang digunakan pada penelitian ini mengunakan debit banjir periode ulang Q-100 tahunan yaitu 627,74 m³/detik (yang melewati jembatan fly over Pango). Dari hasil simulasi pola aliran didapatkan besaran kecepatan aliran tanpa pilar pada lokasi tengah aliran pada titik tinjauan V3 dengan jarak 45 m dari tanggul sungai kecepatan maksimumnya 0,45 m/det dan besaran kecepatan aliran dengan adanya pilar jembatan pada lokasi tengah pilar pada titik tinjauan V3 dengan jarak 33 m dari tanggul sungai kecepatan maksimumnya 0,35 m/det. Pada belokan luar dari hasil simulasi kecepatan aliran tanpa pilar besaran kecepatan maksimum pada titik tinjau V6 dengan jarak 50 m yaitu 0,83 m/det pada kiri aliran. Sedangkan di hilir belokan pada titik tinjau V6 dengan jarak 50 m dengan adanya pilar jembatan besaran kecepatan maksimum yaitu 0,95 m/det kiri aliran. Pada hilir pilar jembatan terdapat belokan sungai yang memerlukan perkuatan tebing dan perkuatan dasar agar tidak terjadi erosi di tebing sungai, sebab hal ini dapat membahayakan terhadap fasilitas umum.

Banding of the pulmonary trunk in preparation for a Fontan operation

1999 ◽  
Vol 9 (1) ◽  
pp. 49-54
Author(s):  
Takahiko Sakamoto ◽  
Yorikazu Harada ◽  
Takamasa Takeuchi ◽  
Katsumasa Morishima ◽  
Gengi Satomi ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Fontan Operation ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Pulmonary Trunk ◽  
Trunk Length ◽  
Pulmonary Flow ◽  
Pulmonary Arterial ◽  
Maximum Flow Velocity ◽  
Aorta Diameter

AbstractBanding of the pulmonary trunk is an important surgical procedure for patients who have con genital cardiac malformations with unrestricted pulmonary flow. We propose a new concept for determining in such circumstances the most appropriate length of the band used to constrict the pulmonary trunk in preparation for a Fontan operation. We studied 14 patients undergoing banding of the pulmonary trunk and measured the following parameters: diameter of aorta, diameter of pulmonary trunk, length of pulmonary arterial band and maximum flow velocity across the banded segment. We calculated an index from our orig inal parameter based on the formula; length of band/(diameter of aorta diameter of pulmonary trunk). The diameter of aorta was 9.5 ± 1.4 mm, and that of the pulmonary trunk was 9.6 ± 2.3 mm. The length of the band was 16.5 ± 3.4 mm, giving a calculated index of 0.188 ± 0.038. The maximum flow velocity was 4.02 ± 0.46 m/s. No correlation was found between the length of the band and body weight, and also no correlation was found between the length of the band and maximum flow velocity. The calculated index had a negative correlation with the maximum velocity of flow across the band (y = -8.13x + 5.56, R = 0.74, p < 0.01). We believe that the proposed index is a useful guide in determining the length of a pulmonary band when preparing patients for a Fontan operation.

Effects of Winter Floods on Fishes in the Sierra Nevada

1988 ◽  
Vol 45 (12) ◽  
pp. 2195-2200 ◽  
Author(s):  
Don C. Erman ◽  
Edmund D. Andrews ◽  
Michael Yoder-Williams
Keyword(s):  
Sierra Nevada ◽  
Brook Trout ◽  
Critical Role ◽  
Maximum Flow ◽  
Timber Harvesting ◽  
Snow Accumulation ◽  
Buffer Strips ◽  
Material Transport ◽  
Bed Material ◽  
The Impact

Winter floods in the Sierra Nevada mountains kill age 0 class brook trout (Salvelinus fontinalis) and Paiute sculpin (Cottus beldingi) because bed-material transport increases greatly when high flows are constrained by snow banks. In February 1982, dead Paiute sculpin were collected while sampling bedload during a rain-on-snow flood. Population estimates by electrofishing at nine permanent stations the following summer showed that density (3586∙ha−1) and biomass(12.9 kg∙ha−1) of Paiute sculpin were lower than the respective means (12 017∙ha−1 and 40.3 kg∙ha−1) obtained during previous studies from 1952 to 1961. These estimates were also below those obtained in 1956, after the largest winter flood from 1952 to 1961. Brook trout fry were also less abundant in 1982 than previously reported. Maximum flow depth, rather than discharge, were the likely cause offish mortality. Winter floods are severe because accumulated snowpack increases the effective height of the streambank and confines most or all of a rain-on-snow flood within the channel. Shear forces on the bed increase and as a result bed-material transport increases rapidly. These conditions directfy kill many benthic-living fishes such as the Paiute sculpin or buried eggs of fall-spawning fishes such as the brook trout by mechanical grinding or crushing. The impact of snow-constrained floods was not uniform along Sagehen Creek due to patchiness in types of riparian canopy. The relationship among canopy cover, snow accumulation, and winter floods points to one more critical role that buffer strips may play in ameliorating effects of timber harvesting.

scholarly journals Интенсификация ламинарного течения в узком микроканале с однорядными наклоненными овально-траншейными лунками

2018 ◽  
Vol 44 (9) ◽  
pp. 73
Author(s):  
С.А. Исаев ◽  
П.А. Баранов ◽  
А.И. Леонтьев ◽  
И.А. Попов
Keyword(s):  
Laminar Flow ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Parallel Channel ◽  
Flow Core ◽  
Single Row ◽  
Channel Section ◽  
Smooth Channel ◽  
Laminar Air Flow ◽  
Maximum Flow Velocity

AbstractA fully developed laminar air flow in a plane-parallel channel of width 6 and height 1 with single-row inclined oval-trench dimples on the walls are calculated using multiblock computing technologies at Re = 10^3. A periodic channel section of length 4 with one dimple of length 4.5, width 1, an angle of inclination to the flow of 45°, and a depth varying from 0 to 0.375 is considered. Intensification of a laminar flow in the flow core in a channel supplied with trench dimples of depth more than 0.25, such that the maximum velocity is 1.5 times higher than the maximum flow velocity in a smooth channel, is found.

The Effect of Frequency on the Flow and Particle Collection Patterns under Electroosmosis

2014 ◽  
Vol 605 ◽  
pp. 59-62
Author(s):  
Che Hung Wei ◽  
Lin Chi Wu
Keyword(s):  
Flow Velocity ◽  
Bottom Electrode ◽  
Low Frequency ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Ac Electroosmosis ◽  
Particle Collection ◽  
Modified Polystyrene ◽  
Maximum Flow Velocity

The collection and manipulation of small objects is important in bioassays. One commonly used force to manipulate small objects is electroosmosis which has the advantages of easy fabrication and small power consumption. Many factors affect the electroosmosis like surface charge density, applied voltage and frequency. For ac electroosmosis, frequency affects flow pattern and particle collection. In this study, the role of frequency is investigated by experiments and verified by numerical simulation. The electroosmosis collecting chip is made of two parallel electrodes separated by a spacer. The chip consists of a top ITO electrode and a bottom electrode made by Corning 1737 glass with different patterned sputtered Cr electrode. The spinning photoresist on the bottom electrode is used as dielectric layer and the electrodes are separated by a curing PDMS spacer. The amine-modified polystyrene particles were collected by varying frequency. To further investigate the mechanism, numerical simulations were carried out using commercial software Comsol with multi-physics setting. The results show the particle flow and collection pattern is sensitive to frequency. For low frequency 100 Hz, the maximum flow velocity occurred in the peripheral boundary of the bottom electrode and the particles are depleted in the central and accumulated in the peripheral area. For high frequency 1000 Hz, the particles are accumulated in the center region of the bottom electrode where the maximum velocity occurs. From simulation, the maximum flow velocity occurs from the boundary towards the center as frequency increases. Meanwhile, the magnitude of the maximum flow velocity is also proportional to the applied frequency. For particles collected by electroosmosis, varying frequency will result in different flow and collection pattern.

scholarly journals IMPROVEMENTS IN DESCRIBING WAVE OVERTOPPING PROCESSES

2012 ◽  
Vol 1 (33) ◽  
pp. 35 ◽  
Author(s):  
Steven A Hughes ◽  
Christopher I Thornton ◽  
Jentsje W Van der Meer ◽  
Bryan N Scholl
Keyword(s):  
Weibull Distribution ◽  
Shape Factor ◽  
Empirical Relation ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Empirical Relationships ◽  
Wave Overtopping ◽  
Hydrodynamic Parameters ◽  
Applicable Range

This paper presents a new empirical relation for the shape factor in the Weibull distribution that describes the distribution of overtopping wave volumes. This improvement increases the applicable range of the Weibull distribution from very low average overtopping discharges to large discharges resulting from combined wave overtopping and steady surge overflow at negative freeboards. The effect this improvement has on wave overtopping simulation is also discussed. Measured maximum flow thicknesses, velocities, and discharges from experiments of combined wave and surge overtopping are examined to learn more about the variability of these key parameters as a function of individual overtopping wave volumes. A key finding is that wave volumes containing the 2%-exceedance value of maximum velocity typically have maximum flow thicknesses well below the 2%-exceedance level, and vice-versa. Furthermore, the 2%-exceedance hydrodynamic parameters do not occur in the 2%-exceedance wave volumes. Finally, empirical relationships are developed for several parameters that showed strong trends.

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