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1
Content available Pomiar i regulacja strumienia ścieków w kanałach z powierzchnią swobodną
Kabza Zdzisław, Rząsa Mariusz R.
Pomiary Automatyka Robotyka
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2020
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R. 24, nr 2
39--43
PL
Pomiar parametrów ścieków należy do stosunkowo trudnych zadań. Ścieki, w większości przepadków, to mieszanina dwufazowa. W ściekach zanieczyszczeniami mogą być ciała stałe lub ciecze, które rozpuszczają się w wodzie lub nie. W pracy autorzy zaproponowali, rozwiązanie systemu do pomiaru strumieni ścieków o szerokim zakresie pomiarowym, odporne na osadzanie się frakcji stałej oraz możliwe do zamontowania na już istniejących kanałach ściekowych. Zaproponowane rozwiązanie oparte jest na przepływomierzu szczelinowym z możliwością regulowania szczeliny w przegrodzie pomiarowej. Podstawowym mierzonym parametrem, na podstawie którego obliczany jest strumień objętościowy przepływających ścieków, jest wysokość ustawienia przegrody. Jest ona funkcją pola przekroju poprzecznego przewężenia. Autorzy przedstawili szczegółowy opis metody pomiarowej.
EN
Measurement of sewage parameters is relatively difficult because sewage is, in most cases, a two-phase mixture. Contaminants in wastewater can be liquids and solids. Liquids in water may have a density higher or lower than the density of water. Density affects the movement of individual mixtures. Liquids with a density higher than the density of water move at the bottom of the channel and the speed of their movement are not equal to the speed of the water. In the case of liquids having a density less than the density of water, they are carried on the surface of the flowing water. Solids move very similarly. Solids with a lower density than water are raised to the water surface, and denser usually roll on the bottom. Furthermore, the fractional differential distribution of solids often results in congestion by deposition of the solid fraction in sewers and measuring apparatus. In this work, the authors proposed a solution for a system for measuring wastewater in a wide range of flows. This solution is insensitive to settling of the solid fraction, and can be mounted on the existing sewers. The proposed solution is based on a slotted flow meter with some modification consisting in adjusting the gap in the measuring partition. The basic parameter, measured based on which the volumetric flow of sewage is calculated, is the height of the partition, which is a function of the cross-sectional area of the narrowing. A detailed description of the measurement method and measurement methodology is provided.
2
Content available Inverse Problem for Looped River Networks – Lower Oder River Case Study
Kurnatowski J.
Archives of Environmental Protection
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2013
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Vol. 39, no. 1
105-118
EN
Identification of coefficients determining flow resistance, in particular Manning’s roughness coefficients, is one of the possible inverse problems of mathematical modeling of flow distribution in looped river networks. The paper presents the solution of this problem for the lower Oder River network consisting of 78 branches connected by 62 nodes. Using results of six sets of flow measurements at particular network branches it was demonstrated that the application of iterative algorithm for roughness coeffi cients identification on the basis of the sensitivity-equation method leads to the explicit solution for all network branches, independent from initial values of identifi ed coefficients.
3
Content available Spatially Averaged Log-Law for Flows over Rough Bed in Zero- and Non-Zero-Pressure Gradient Boundary Layers
Czernuszenko W.
Archives of Hydro-Engineering and Environmental Mechanics
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2011
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Vol. 58, nr 1-4
65-86
EN
Theoretical bases for building a logarithmic law for non-uniform flows over a large relative roughness are presented. In order to define the equivalent velocity distribution and to smooth out 3D flow irregularities, a special spatial averaging operation is defined. Basic equations are spatially averaged and double-averaged momentum equations for primary component velocity are derived for uniform flow over a gravel bed as well as for non-uniform flows. A new hypothesis is proposed, and some assumptions are introduced to solve these momentum equations. This results in a new version of the logarithmic velocity distribution (log law). To define this distribution, a full reconstruction of Nikuradse's graph for flows over an irregular gravel riverbed is considered. It is based on very precise measurements of velocity and other hydraulic parameters. In the case of non-uniform flows, the logarithmic velocity profile appears also in accelerating flows in a gravel bed channel, but the friction velocity should be re-defined according to Eq. (24). The same applies to decelerating flow with a positive pressure gradient, but only if the gravitational force exceeds the pressure gradient. For accelerating flows, the additive constant BP depends on the pressure gradient, and its values grow with a growing pressure gradient.
4
Content available remote Analiza możliwości zastosowania metody najmniejszych kwadratów w algorytmie pomiarowym przepływomierza elektromagnetycznego dla kanału otwartego
Jakubowski J., Michalski A.
Przegląd Elektrotechniczny
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2008
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R. 84, nr 5
126-131
EN
The paper presents a discussion on the application of the least squares method as a possible measuring procedure for open channel electromagnetic flowmeters. The basic drawback of the method connected with the differences between measuring paths of the signal components and the signal itself is presented together with the efforts to reduce it.
5
Content available Shear Stress Statistics in a Compound Channel Flow
Czernuszenko W., Rowiński P. M.
Archives of Hydro-Engineering and Environmental Mechanics
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2008
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Vol. 55, nr 1-2
3-27
EN
The results of comprehensive measurements of three-dimensional turbulent velocities carried out in a laboratory compound channel are presented. Tests were performed in a two-stage channel with a smooth main channel bed consisting of concrete and rough floodplains and sloping banks. Instantaneous velocities were measured with the use of a three-component acoustic Doppler velocimeter. The main aim of the study is the recognition of structure of Reynolds stresses in turbulent open channel flows. Particular attention has been paid to bursting events such as ejections and sweeps. The bursting phenomenon occurs originally near the buffer layer and then shows a coherent or organized flow structure during its convection process. The probability density distributions of the turbulent velocities were measured at different distances from the bed in the main channel and also above the inclined walls. In the main channel, the lateral turbulent velocity is seen to follow the normal Gaussian distribution more closely than the remaining two components. Above the inclined walls, all distributions turned out to have greater skewness. The probability density distributions of correlations between velocity fluctuations were also calculated. These distributions have long tails and sharp peaks and fit the theoretical distributions very well. The structure of instantaneous Reynolds stresses was analyzed by a quadrant technique with an arbitrarily chosen threshold level. It has been shown that the largest contribution to turbulent stresses comes from the second quadrant (ejection) and the fourth quadrant (sweep). The basic temporal characteristics for quadrant events, like the average and maximum time for a zero hole size, have been determined in the study. Calculations of maximum duration times for all events reveal that times are greater for even quadrants than for odd quadrants.
6
Content available Measurements of 3D turbulence structure in a compound channel
Czernuszenko W., Kozioł A., Rowiński P. M.
Archives of Hydro-Engineering and Environmental Mechanics
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2007
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Vol. 54, nr 1
55-73
EN
The paper describes some turbulence measurements carried out in an experimental compound channel with flood plains. The surface of the main channel bed was smooth and made of concrete, whereas the floodplains and sloping banks were covered by cement mortar composed with terrazzo. Instantaneous velocities were measured be means of a three-component acoustic Doppler velocity meter (ADV) manufactured by Sontek Inc. This article presents the results of measurements of primary velocity, the distribution of turbulent intensities, Reynolds stresses, autocorrelation functions, turbulent scales, as well as the energy spectra.
7
Content available Boundary problem for equations of steady gradually varied flow in open channels
Szymkiewicz R.
Archives of Hydro-Engineering and Environmental Mechanics
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2001
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Vol. 48, nr 4
23-37
EN
In this paper the problem of solution of ordinary differential equations describing a steady, gradually varied flow is discussed. It is shown that, apart from the initial problem usually solved for open channels, the formulation of the boundary problem is necessary when water levels are imposed at ends of channel. This approach is the mathematically correct formulation of the solution problem for steady, gradually varied flow equations. It enables us to determine directly the water profile and discharge for a single channel, as well as for channel network, instead of the trial and error method usually used. Moreover the formulation of boundary problem with respect to the Manning coefficient and lateral inflow is presented. To solve the listed problems the finite differences method is used.
8
Content available remote Conveyance calculation for channels overgrown with grass by applying hydraulic equivalent thickness of grass layer
Rimkus A.
Journal of Water and Land Development
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2000
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no. 4
123-135
EN
The slopes of canalised brooks and ditches, which are the drainage water receivers, including open channels of other purposes are usually overgrown by grass. The slopes of naturalised channels are seldom if ever mowed. Therefore, when performing hydraulic calculations (for an average discharge at vegetation time, a maximum discharge during summer floods), it must be presumed that these channels are overgrown with luxuriant grass of 50-70 cm height. Thus, by estimating channel conveyance, i.e., possibility to allow the vegetation to exist, it is necessary to take the grass influence into account. For this purpose, it was necessary to work out a hydraulic calculation method for such channels. In the Lithuanian Institute for Water Management, a hydraulic calculation model was developed for naturalised channels overgrown by trees and grasses (RIMKUS, 1996). To estimate the grass influence, the hydraulic research data published by DĄBKOWSKI and POPEK (1997) (Warsaw Agricultural University) were employed. To apply these data it was necessary to employ the method of equivalent hydraulic bottom.
PL
Wiele z rowów naturalnych cieków wodnych zarasta roślinnością trawiastą. Zmienia ona hydrauliczne właściwości koryt w tym także spadek hydrauliczny w korytach poddawanych zabiegom renaturalizacyjnym. Prowadząc obliczenia przepustowości takich koryt trzeba uwzględniać możliwość ich zarastania trawami o wysokości do 50-70 cm. Przyjęto, że praktyczniej jest w obliczeniach stosować współczynnik szorstkości i głębokości strumienia odnoszone do powierzchni pochylonych traw. Wykorzystując dane z doświadczeń DĄBROWSKIEGO i POPKA [1997] sporządzono dla trzech natężeń przepływu q zależności współczynnika szorstkości n1 od głębokości h1, odnoszących się do przekroju strumienia do dna koryta (tab. 1 i rys. 1). Z krzywych wyrównujących te zależności odczytano wyrównane wartości odpowiadających sobie n1 i h1. Przyjęto, że w analizowanym przypadku (gładkie szklane ściany boczne) promień hydrauliczny jest równy głębokości wody. W dalszych analizach wprowadzono pojęcie zastępczego dna koryta na poziomie wierzchołków przygiętych traw. Głębokość strumienia wody przy takim założeniu wynosi h = h1 - t, gdzie t jest grubością przygiętych traw. Stosując wzór Chezy'ego dla całego przekroju i dla przekroju zastępczego o głębokości h i odpowiadającego jej współczynnika szorstkości n uzyskano wyrażenie (4), a następnie ze wzoru (5) na grubość warstwy traw t. Ze wzoru (5) obliczono wartości t przy założeniach czterech wartości współczynnika szorstkości warstwy przygiętych traw n i zebrano je w tabelach 3-6. Zmianę współczynnika szorstkości n wyrażono wzorem (6), w którym hgr jest wysokością traw w analizowanych doświadczeniach. Do obliczeń grubości warstwy przygiętych traw t użyto wzoru (7). Współczynniki liczbowe a1-a5 występujące w tym wzorze obliczono na podstawie wyników wspomnianych doświadczeń dla dwóch przypadków, opisanych wzorami (9) i (11). Wysokość traw w doświadczeniach wynosiła 0,35 m.
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