scholarly journals Three Methods for Estimating the Entropy Parameter M Based on a Decreasing Number of Velocity Measurements in a River Cross-Section

Entropy ◽  
2014 ◽  
Vol 16 (5) ◽  
pp. 2512-2529 ◽  
Author(s):  
Giulia Farina ◽  
Stefano Alvisi ◽  
Marco Franchini ◽  
Tommaso Moramarco
Keyword(s):  
Cross Section ◽  
Velocity Measurements ◽  
Entropy Parameter ◽  
River Cross Section

Estimating discharge in rivers through the combined use of dimensionless isovels and point velocity measurements

2017 ◽  
Vol 48 (3) ◽  
pp. 616-633 ◽  
Author(s):  
G. Farina ◽  
S. Alvisi ◽  
M. Franchini
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Accurate Estimation ◽  
Velocity Measurements ◽  
Combined Use ◽  
Point Velocity ◽  
New Formulation ◽  
The Relationship ◽  
River Cross Section

This paper presents a procedure for estimating discharge in a river cross-section based on the combined use of dimensionless isovels and point velocity measurements. Specifically, taking the Biot–Savart law on the magnetic field induced by an electric current in a wire as their basis as already done by other researchers, the authors propose a new formulation of the relationship characterizing the effect of the wetted perimeter on the range of velocities in a cross-section in order to take explicit account of roughness, expressed by means of Manning's coefficient. Once appropriately nondimensionalized, the isoeffect contours can be read as dimensionless isovels. Assuming in situ velocity measurements are available, discharge at a cross-section can be computed using two different methods. The proposed procedure was applied to six case studies characterized by river cross-sections which differed greatly from one another. The results show that the two methods proposed for estimating discharge lead to equivalent outcomes, and in all the cases the procedure as a whole enables a sufficiently accurate estimation of discharge, even when it is based on a limited number of velocity measurements or on the measurement of maximum surface-water velocity alone.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

scholarly journals Calculation of acoustic flow-rate measurements error with the help of Fermat’s principle

2018 ◽  
Vol 211 ◽  
pp. 04007
Author(s):  
Alexander Petrov ◽  
Semyon Shkundin
Keyword(s):  
Control Systems ◽  
Cross Section ◽  
Flow Rate ◽  
Three Dimensional ◽  
Air Flow Rate ◽  
Velocity Measurements ◽  
Three Dimensional Flow ◽  
Automatic Control Systems ◽  
A Value ◽  
Flow Changes

The establishment of dispatching and automatic control systems for mine ventilation is impossible without the availability of perfect air flow rate sensors. Existing anemometers (tachometer, heat) do not meet these requirements. The error of average in cross section velocity measurements with such sensors reaches 15-20, sometimes 30%. The reason - the speed measured at one point is interpreted as the average over the cross section. The reliability of the sensors is small, because they are exposed to the damaging effect of a dusty atmosphere. Stationary installed anemometers clutter cross section, which is not always allowed. Fermat’s variational principle is used for derivation of the formula for the time of propagation of a sonic signal between two set points A and B in a steady three-dimensional flow of a fluid or gas. It is shown that the fluid flow changes the time of signal reception by a value proportional to the flow rate independently of the velocity profile. The time difference in the reception of the signals from point B to point A and vice versa is proportional with a high accuracy to the flow rate. It is shown that the relative error of the formula does not exceed the square of the largest Mach number. This makes it possible to measure the flow rate of a fluid or gas with an arbitrary steady subsonic velocity field

scholarly journals ANALISIS TINGGI MUKA AIR BANJIR DAS BELAWAN DENGAN MENGGUNAKAN SOFTWARE HECRAS

2018 ◽  
Vol 7 (1) ◽  
pp. 26-29
Author(s):  
Asril Zevri
Keyword(s):  
Water Level ◽  
Cross Section ◽  
Return Period ◽  
Industrial Development ◽  
Daily Rainfall ◽  
Flood Water ◽  
Flood Discharge ◽  
Flood Level ◽  
Maximum Daily Rainfall ◽  
River Cross Section

Abstract: Belawan River Basin is one of the watershed, which currently change the land use because of the increasing population and industrial development. Rainfall with high intensity can cause rapid runoff, causing flood around the plains of the river cross section. The purpose of this research is to determine the flood water level of Belawan Watershed and flood discharge return period. Scope of activity in this research is analyzing daily rainfall Belawan watershed with the flood-discharge return period. Scope of activity in this research is analyzing maximum daily rainfall Belawan Watershed, and simulating flood water level with HECRAS. The result of the study shows that the potency of Belawan watershed flood water level is caused by flood discharge at 25 to 100 years especially in the middle to downstream of river cross section that is between 0.7 m and 3.3 m. Keywords: Flood Discharge, Flood Level, Belawan Watershed, Software HECRAS. Abstrak: Daerah Aliran Sungai Belawan adalah salah satu DAS yang pada saat ini mengalami perubahan tata guna lahan seiring bertambahnya jumlah penduduk dan perkembangan industri. Curah hujan yang tinggi dapat mengakibatkan limpasan sehingga menimbulkan tinggi muka air banjir di sekitar dataran penampang sungai. Tujuan dari penelitian ini adalah untuk mensimulasi tinggi muka air banjir DAS Belawan dengan debit banjir periode kala ulangnya. Lingkup kegiatan dalam penelitian ini yaitu menganalisa curah hujan harian maksimum rata-rata DAS Belawan dan menganalisa debit banjir kala ulang 2 sampai dengan 100 tahun, mensimulasi tinggi muka air banjir dengan HECRAS. Hasil studi menunjukan potensi tinggi muka air banjir DAS Belawan terjadi akibat debit banjir periode kala ulang 25 sampai dengan 100 tahun khususnya  di bagian tengah sampai hilir penampang sungai yaitu berkisar antara 0.7 m sampai dengan 3.3 m. Kata kunci: Debit banjir, Tinggi Banjir, DAS Belawan, Software HECRAS.

scholarly journals PENGARUH BENDUNG TERHADAP PROFIL MUKA AIR SUNGAI BATANG GADIS

2014 ◽  
Vol 8 (1) ◽  
pp. 1
Author(s):  
Sudarmanto ,
Keyword(s):  
Numerical Integration ◽  
Cross Section ◽  
Water Surface ◽  
Surface Profile ◽  
Uniform Flow ◽  
Flood Discharge ◽  
Before And After ◽  
Numerical Integration Methods ◽  
The Village ◽  
River Cross Section

Placement of the weir in the river Batang Gadis will cause population anxiety in the village Pulungan which located upstream weir as far as 3 km, due to a weir can cause water surface profile of the river getting higher and ultimately to increase the pool of flooding in residential areas.Assuming modeling of river a uniform flow, river cross-section has a rectangular shape with width 50 m and 40 m, the roughness Manning 0.0025, the profile of water flow floods that occurred in 2 yaears, 25 years, and 100 years before and after the existing weir can be calculated by numerical integration methods.  From the calculation, the length of the water behind the weir is 1.4 km upstream towards the weir, which means that the depth of the water level rises to as far as 1.4 km and after that the depth of water before and after there the weir is same. Because the village Pulungan located 3 km to the upstream, the weir did not affect the increase in the flood waters in the village Pulungan. At 2 years flood discharge does not cause inundation in the village Pulungan, but the flood discharge 25 years and 100 years has led to inundation in the village Pulungan with the depth of each pool 0.971 m and 1.675 m. Keywords: uniform flow, numerical integration, inundation, flood discharge.

Modelling the distribution of velocity in a river cross‐section

1997 ◽  
Vol 31 (2) ◽  
pp. 155-162 ◽  
Author(s):  
Derek G. Goring ◽  
Jeremy M. Walsh ◽  
Peter Rutschmann ◽  
Jürg Trösch
Keyword(s):  
Cross Section ◽  
River Cross Section

scholarly journals Surface water resources of small agricultural watershed in the Kujawy region, central Poland

2017 ◽  
Vol 33 (1) ◽  
pp. 131-140
Author(s):  
Zygmunt Miatkowski ◽  
Karolina Smarzyńska
Keyword(s):  
Surface Water ◽  
Water Resources ◽  
Cross Section ◽  
Crop Production ◽  
Groundwater Resources ◽  
Arable Land ◽  
Agricultural Watershed ◽  
Surface Water Resources ◽  
The Mean ◽  
River Cross Section

AbstractThe goal of the paper was to determine surface water resources of an agricultural watershed representative for the areas of intensive crop production in the Kujawy region. This area is characterised by the lowest average annual precipitation in Poland and high water demands related to the intensive crop production.Hydrological studies were carried out in 2007–2011 in the upper Zgłowiączka River watershed located in the eastern part of the analysed region. Over 90% of the study area is used as an arable land.Water velocity in the river bed and water level were measured at the outlet of the watershed in the river cross-section Samszyce.The upper Zgłowiączka River has a snow-rainfall hydrological regime, strongly modified by anthropogenic activities related to the intensive crop production and installation of subsurface drainage system. The study period was characterised by very large temporal variability of hydrological conditions. The mean annual outflow coefficient amounted to 18% and varied highly in time: from 3% in the average years to 62% in the abnormally wet 2011. Average discharge (SSQ) in the Samszyce river cross-section was equal to 0.25 m3·s−1, and the mean unit outflow – to 3.2 dm3·s−1·km−2. The results of the study show that disposable surface water resources of the Kujawy region are very small, especially in the summer half-year. Thus, their utilization as a potential source of water for crop irrigation can be taken into account only, if water excesses will be retained within the watershed and used in conjunction with groundwater resources.

The Drift Velocity of Electrons in Water Vapour at Low Values of E/N

1990 ◽  
Vol 43 (6) ◽  
pp. 755 ◽  
Keyword(s):  
Momentum Transfer ◽  
Water Vapour ◽  
Cross Section ◽  
Drift Velocity ◽  
Velocity Measurements ◽  
Low Energies ◽  
Momentum Transfer Cross Section

The drift velocity of electrons in water vapour at 294 K has been measured over the E/N range 1�4 to 40 Td with an error estimated to be 35 Td. The present data show that J.lN decreases monotonically with decreasing E/N at low E/N values as observed by Wilson et al. (1975) and does not become independent of E/N as indicated by Lowke and Rees (1963). The present values, although lower than those of Lowke and Rees, lie within the combined error limits, except for values below 2 Td. The present data suggest that the momentum transfer cross section at low energies is approximately 10% larger than that obtained by Pack et al. (1962) from their drift velocity measurements.

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