BazTech - Yadda

1

Mixing effects in the river downstream from pollution discharge point

Bielski Andrzej

Technical Transactions

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2021

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Vol. 118, iss. 1

art. no. e2021004

EN

This paper follows the propagation of pollution in a river with a rectangular crosssection of the river bed and a variable cross-sectional velocity. The calculations were made for steady flows and steady pollutant concentrations. To approximate the velocity distribution in the river bed a set of equations for current and vorticity functions was solved. The distribution of pollutant concentrations in the river was calculated from a bidirectional advection and turbulent diffusion equation. Analysis of the distribution of concentrations leads to the conclusion that the effects of transverse advection associated with a lateral inflow of pollutants disappear relatively quickly. Therefore, the distribution of concentrations in cross sections further downstream from the point of pollutant discharge can be determined quite accurately just from an advection-diffusion model, with no transverse advection effects included. Such a level of accuracy is usually sufficient to assess the impact of a pollution source on the aquatic environment. The transverse mixing of pollutants in the stream proceeds slowly and creates a large mixing zone in which the concentrations of pollutants (low but still significant for water quality) can be detected in cross-sections that are remote from the pollutant discharge point. Transverse advection may be ignored while calculating concentrations in remote cross sections at straight watercourse sections and in steady state conditions.

2

Zastosowanie modelowania hydraulicznego 2D w weryfikacji prawidłowości położenia osi filarów mostowych w stosunku do kierunku przepływu

Bartosik Zbigniew, Batory Jakub, Pietrykowski Radosław, Rukść Sylwester

Gospodarka Wodna

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2021

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Nr 1

14--25

PL

Przedstawiono analizę oddziaływania usytuowania filarów przeprawy mostowej przez Wisłę na trasie Południowej Obwodnicy Warszawskiej (POW), na zmiany kierunków przepływu wody w korycie rzeki. Przedstawiono metodykę oraz wyniki symulacji różnego położenia filarów. Przedstawiono także ocenę wpływu lokalizacji przeprawy na kształtowanie Kępy Zawadowskiej - cennego obszaru przyrodniczego. Do analizy wykorzystano modelowanie numeryczne z wykorzystaniem aplikacji rodziny programów HEC-RAS.

EN

The article presents an analysis of impact of the location of pillars of the bridge crossing the Vistula River as part of the southern ring road for Warsaw (Południowa Obwodnica Warszawska, POW) on the direction of water flow in the riverbed. It presents the methodology and the results of simulations of different pillars locations. It also presents the impact assessment of the crossing location on the shape of Kępa Zawadowska - a precious natural area. The analysis uses numerical modelling including an application belonging to the HEC-RAS family.

3

Numerical study on two dimensional distribution of streamwise velocity in open channel turbulent flows with secondary current effect

Mohan S., Kundu S., Ghoshal K., Kumar J.

Archives of Mechanics

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2021

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Vol. 73, nr 2

175--200

EN

For studying mechanism of sediment transport in river flows, open channel flow is a prototype. Flow has always three components of velocity for all types of channel geometry and for a time independent uniform flow along streamwise or main flow direction, all the components of velocity are functions of lateral and vertical coordinates. The present study investigates the two dimensional distribution of streamwise (or longitudinal) velocity starting from the Reynolds averaged Navier–Stokes equation for a turbulent open channel flow which is steady and uniform along the main flow direction. Secondary flows both along the vertically upward direction and along the lateral direction are considered which are also taken as functions of lateral and vertical coordinates. Inclusion of the secondary current brings the effect of dip phenomenon in the model. The resulting second order partial differential equation is solved numerically. The model is validated for all the cross-sectional, transverse and centreline velocity distribution by comparing with existing relevant set of experimental data and also with an existing model. Comparison results show good agreement with data as well as with the previous model proving the efficiency of the model. It is found that the transverse velocity distribution depends on the formation of circular vortex in the cross-sectional plane and becomes periodic as the number of circular vortex increases for increasing aspect ratios.

4

Computational fluid dynamics (CFD) numerical simulation and particle image velocimetry (PIV) measurement of a packed flotation column

Yan X., Chen Z., Wang L.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

395--405

EN

Packing is a useful method to obtain a static separation environment for a high flotation recovery and selectivity. In this study, the single-phase flow field in a packed lab-scale cyclonic-static microbubble flotation column (FCSMC) was investigated by computational fluid dynamics (CFD) simulation. Turbulence model was verified by Particle Image Velocimetry (PIV) experiment; the simulation results obtained by the RSM (Reynolds Stress Model) are closer to the experimental data. Based on this validation, RSM turbulence model was used to obtain the effect of sieve-plate on the hydrodynamic characteristics in the column flotation zone. The results show that the sieve-plate packing arrangement greatly straightens the rotation flow and decreases the turbulence. To further improve the effect of packing, two layers of sieve plates were used, and one diameter (1D = 190 mm) was selected as the reasonable distance between the two layers of sieve plates. To quantitative evaluate the effect of sieve-plate packing, the logarithm of Pdk over the logarithm of Pdo was calculated based on the volume-averaged turbulence dissipation rate, increasing from 24.72 for one layer of sieve-plate packing to 216.96 for two layers of sieve-plate packing. The probability of detachment significantly decreased for two layers of sieve-plate packing, and the recovery efficiency was significantly improved.

5

The Influence of the Selected Turbulence Model and Grid Density Degree on the Results of Velocity Distribution Obtained with the Use of the Simulation Program SSIIM

Hammerling M., Walczak N., Nieć J.

Journal of Ecological Engineering

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2018

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Vol. 19, nr 3

106--114

EN

This paper analyzed the water flow parameters in the local scour created after building stones sills No 3 km 480 + 902 and 4 km 479 + 225 below the Jeziorsko reservoir on the river Warta. The analysis was carried out using the result of field measurements (velocity distributions) and SSIIM (freeware) software. The study of the geometry of the local scour, were used to create a numerical model and implementing it to the SSIIM software. In the research, the impact of grid density on the obtained results was estimated. The results included the qualitative and quantitative assessment. The conducted analysis can be used to determine the movement of sediment in local scour, and can predict the development in time, and also specify the sill stability under different conditions of the water flow.

6

Change in flow separation and velocity distribution due to effect of guide vane installed in a 90° pipe bend

Kumar Saha S., Nandi N.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 2

353--361

EN

Present paper makes an effort to study the flow separation and velocity distribution for incompressible turbulent flow through 90° pipe bend due to the effect of guide vane installed in the bend portion. It has been observed here how the normalized velocity distribution profile changes if the guide vane is provided. k-ɛ turbulence model has been adopted for simulation purpose. After validating with existing experimental results, a detailed study has been performed for a particular Reynolds number and four different positions of guide vane. The value of Curvature ratio (Rc/D) has been considered as 1 for present study. The results obtained from the present study have been presented in terms of graphical form. A flow separation region was found at bend outlet for flow through 90° pipe bend without guide vane. This secondary flow separation region was absent for the cases which deals with the flow through 90° pipe bend with guide vane. Velocity distribution at seven different downstream positions have been presented in graphical form. Position to get a fully developed velocity distribution profile for each cases has been estimated on the basis of presented results.

7

Significance of current velocity gradients for distribution patterns of charophytes versus mosses and vascular plant communities in a lowland stream

Jakubas E., Gąbka M.

Oceanological and Hydrobiological Studies

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2015

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Vol. 44, No. 2

139--150

EN

The study focused on the relationships between charophytes and the surrounding species composition and environmental factors in a lowland stream (Flinta stream, Western Poland). A total of 32 vegetation plots (4 m × 4 m) and 13 environmental variables were tested. Detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to describe the relationships between the species composition and the selected variables. Dominance curves of aquatic plants, response curves (GAMs model) of charophytes and other macrophytes to the velocity gradient (the most important environmental factor, the Monte Carlo test) were prepared. In this study, 2 species of charophytes were recorded: Chara vulgaris and Chara globularis and 5 other co-occurring macroscopic algae, 2 mosses and 10 vascular plants. In the studied stream, charophytes occupied the separate niche. Chara vulgaris stands with moss vegetation were found in stream sections with the highest velocity of the water current (0.29 m s-1 mean), and the Chara globularis (with dominant Potamogeton species), preferred sections with the smallest water current velocity (0.19 m s-1 mean). Charophytes seem to respond to ecological gradients differently from mosses and vascular plants. These differences are related to current velocity, pH, conductivity and organic matter in bottom sediments, and to the niche differentiation associated with them.

8

Effect of Reynolds Number and Curvature Ratio on Single Phase Turbulent Flow in Pipe Bends

Dutta P., Nandi N.

Mechanics and Mechanical Engineering

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2015

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Vol. 19, nr 1

5--16

EN

Curved pipes are very often used in hydraulic systems facilitating compact, lightweight designs. But they can also be the cause of complex secondary flows as the curvature brings change of velocity profile, generation of vortices and production of hydraulic losses. In the present study, turbulent single phase flows through circular 90˚ curved bend for different curvature ratio (Rc/D = 1 to 5), defined as the bend mean curvature radius (Rc) to pipe diameter (D) is investigated numerically for different Reynolds number (Re) ranging from 1×105 to 10×105. The purpose of this study is to simulate numerically the flow pattern and characterize the swirling secondary flow in 90˚ bends. Flow simulation using CFD techniques are performed to understand these phenomena. The k − " model with SIMPLE method is used for present study. After validation of present model with published experimental data, a detail study has been performed to characterize the flow separation and the dependency of swirl intensity on Reynolds number and curvature ratio in 90˚ pipe bend for single phase turbulent flow.

9

Laminar flow past the bottom with obstacles – a suspension approximation

Wojnar R., Bielski W.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2015

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Vol. 63, nr 3

685--695

EN

From Albert Einstein’s study (1905) it is known that suspension introduced to a fluid modifies its viscosity. We propose to describe the influence of obstacles on the Stokesian flow as a such modification. Hence, we treat the fluid flow through small obstacles as a flow with suspension. The flow is developing past the plane bottom under the gravity force. The spatial distribution of suspension concentration is treated as given, and is regarded as an approximation of different obstacles which modify the fluid flow and change its viscosity. The different densities of suspension are considered, beginning of small suspension concentration until 40%. The influence of suspension concentration on fluid viscosity is analyzed, and Brinkman’s formula as fitting best to experimental data is applied.

10

Modelowanie osiowosymetrycznych rozkładów prędkości dla przewodów zamkniętych o kołowym przekroju poprzecznym

Nawrat P., Waluś S.

Pomiary Automatyka Kontrola

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2014

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R. 60, nr 12

1196--1200

PL

Praca dotyczy modelowania rozkładów prędkości płynów w rurociągach. Przedstawiono rozkład prędkości wody w rurociągu o średnicy 1200 mm i profil prędkości powietrza w rurociągu o średnicy 100 mm. W pewnych warunkach lepszy jest model Krzyżanowskiego, niż powszechnie używany w podręcznikach model Prandtla. Zaproponowano trzy nowe modele: Walusia, Dąbrowskiego-Walusia i Nawrata. Okazało się, że najlepsze dopasowanie uzyskuje się dla dwóch ostatnich.

EN

The paper concerns of modeling of velocity distribution in pipe with various formulas, in purpose to achieve the best accordance with measuring data. This modeling is very important for estimation of calibration factor for sampling flow meters ([1, 7, 9]). The example of velocity distribution of water in 1200 mm pipe diameter (Fig. 1) and the profile of velocity of air for 100 mm pipe (Fig. 2) are introduced. The analysis of Prandtl model (2) was made, and it became to real that this model is not good enough for turbulent flow. In some conditions the Krzyżanowski formulae (3) is better. In the Figs 3 and 4 the results of Prandtl model’s parameters estimation are introduced. In the Fig. 5 the results for Dąbrowski-Waluś model are presented. The conditions for mathematical models describing the velocity distributions are formulated in Chapter 4, and are proposed some new models: Waluś (4), Dabrowski-Waluś (5) and Nawrat (6). Nine criterions of evaluating of model are presented, and in Table 1 their values of are given for Krzyżanowski model (3), Nawrat model (6) and for measurement data in the pipe of 100 mm (with probe without of blockage effect). Taking into account all of these criterions, the best fitting was achieved for Dabrowski-Walus model (5) and for Nawrat model (6). Results achieved in this paper shows, that there is the need for better estimation of velocity distribution model.

11

Przepływ masy czekoladowej w szczelinie między płaską powierzchnia a walcem w procesie konszowania czekolady

Kiljański T.

Inżynieria i Aparatura Chemiczna

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2011

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Nr 1

23-24

PL

Rozpatrywano przepływ płynu opisanego równaniem Herschela-Bulkleya, reprezentującego własności reologiczne stopionej czekolady, w szczelinie między płaskim dnem aparatu a toczącym się po nim walcem. Wyprowadzono równania opisujące rozkład prędkości, naprężenia stycznego i gradientu ciśnienia w szczelinie oraz zapotrzebowanie mocy. Zaproponowano algorytm obliczeń powyższych wielkości.

EN

Flow of visco-plastic fluid described by the Herschel-Bulkley equation, representing rheological properties of molten chocolate, in a gap between the apparatus flat bottom and the cylinder rolling on it was considered. Equations describing velocity, shear stress, pressure gradient distribution and power consumption were derived. The algorithm for calculation of above mentioned properties was proposed.

12

The influence of the inlet and outlet conditions on the air velocity distribution in a large industrial hall

Lipska B., Skrzątek A.

Architecture Civil Engineering Environment

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2011

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Vol. 4, no. 4

131-146

EN

The paper presents the results of investigations aiming at an assessment of the effect of various factors connected with the supply and exhaust of ventilation air in the typical industrial hall at mixing ventilation with tangential flows of supplied air on the velocity distribution in the occupied zone. For this purpose the computer codes Flovent were used, based on the technique of computational fluid dynamics CFD and permitting to predict the airflow. The method of assessing and comparing the velocity distribution was suggested. The validation of the numerical calculations concerning the occupied zone was presented, basing on the measurements in the physical model of this hall. In the course of investigations the supply air velocity, the distance between the inlets, the angle of spread of the vanes in the inlets and the localization of the outlets was changed at isothermal and non-isothermal airflow, observing simultaneously the distribution of the air velocity in occupied zone. Based on these investigations the conclusions have been drawn that such factors as height of the positioning of the outlets or the spread of the vanes are in this case of less importance. Much more importance must be assigned to the supply air velocity and spacing of the inlets. These conclusions may constitute guidelines for designers of ventilation systems.

PL

W pracy przedstawiono wyniki badań mających na celu ocenę wpływu różnych czynników związanych z nawiewem i wywiewem powietrza wentylacyjnego w typowej hali przemysłowej z wentylacją mieszającą ze stycznym przepływem powietrza nawiewanego na rozkład prędkości w strefie przebywania ludzi. W badaniach wykorzystano program komputerowy Flovent, bazujący na technice numerycznej mechaniki płynów CFD, pozwalający prognozować przepływy powietrza. Zaproponowano metodę oceny i porównania rozkładów prędkości. Przeprowadzono walidację obliczeń numerycznych dotyczących strefy przebywania, wykorzystując w tym celu wyniki pomiarów w modelu fizykalnym tej hali. W trakcie badań numerycznych, prowadzonych w warunkach izotermicznych i nieizotermicznych, zmieniano prędkość nawiewania powietrza, odległość pomiędzy nawiewnikami, kąt rozwarcia łopatek nawiewników i lokalizację wywiewników, obserwując przy tym zmiany rozkładu prędkości powietrza w strefie przebywania ludzi. Stwierdzono, że takie czynniki, jak wysokość położenia wywiewników lub kąat rozwarcia łopatek nawiewników miały w rym przypadku małe znaczenie. Znacznie istotniejszy był wpływ prędkości nawiewania powietrza i rozstawu nawiewników. Wnioski te mogą stanowić wytyczne dla projektantów systemów wentylacyjnych w tego typu halach.

13

Visualization of an outflow in the radial blade passage on the basis of thermoanemometric measurements

Fortuna S., Siwek T., Figiel P.

Mechanics and Control

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2010

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Vol. 29, no. 1

11-15

EN

In this paper results of measurements of velocity distribution in the blade passage of radial rotor are presented. Construction of professional test rig with covered rotor passage and thermoanemometr usage made possible fluid flow visualization and detailed analysis of flow direction. Carried out tests showed high speed in negative pressure region. This means contrast to recently known theory about positive pressure regions. Correctness of measurements and results has been confirmed by smoke visualization and examples of computational simulations.

PL

Artykuł prezentuje rezultaty badań rozkładu prędkości w kanale międzyłopatkowym wirnika promieniowego. Skonstruowanie specjalnego stanowiska badawczego z zaklejonym kanałem wirnika i wykorzystanie termoanemometru umożliwiło wykonanie wizualizacji przepływu czynnika wraz z dokładną analizą kierunku jego przepływu. Przeprowadzone doświadczenia wykazały występowanie wysokiej prędkości promieniowej po stronie podciśnieniowej łopatki, a nie jak dotąd sądzono po stronie nadciśnieniowej. Poprawność badań została potwierdzona na podstawie wizualizacji dymowej oraz literaturowych symulacji komputerowych.

14

Heat transfer analysis inside a duct under laminar flow condition using variational method

Banerjee M. K., Banerjee R.

International Journal of Applied Mechanics and Engineering

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2008

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Vol. 13, no 4

889-901

EN

When a fluid flows through a pipe line, the velocity and temperature distribution across the pipe cross section is required to be determined in order to properly utilize the fluid and its associated energy in a process plant. In the present paper, a variational method has been used to determine this distribution in a pipeline of rectangular as well as square cross section under laminar condition. The mathematical equations have been developed describing the velocity and temperature distributions under two cases. In the first case, the heat flow rate is taken to be uniform along the axial direction and in the second case, the wall temperature has been taken to be uniform. In both the cases, the velocity and temperature distribution curves have been drawn from the mathematical equations derived. The distribution curves are presented for a variety of thermal boundary conditions around the periphery of the duct cross section.

15

The identification method of airflow character in combustion engines

Kolanek Cz., Tkaczyk M.

Journal of KONES

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2006

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Vol. 13, No. 3

131-137

EN

This work contains description about place to determine: not invasive methods distribution velocity of air in combustion engines cylinder, invasive methods define velocity flow of air in inlet track. Moreover contain progress measurements about description in used laser- end thermoanemometry. Determined values was created witch the aid of algorithm weight rests, worked out and graphic presented. The last part contains identification of flow character on the basis of findings. The schema of the measuring-stand, the schema of the laser- measuring-system, plots velocity components are presented in the paper. Research showed that at given parameters eddying perimetric round the axis of the cylinder did not occur. In points being found nearest the plate of the valve smallest values absolute velocity were registered. Shape of the intake air channel introducing perimetric eddy in the cylinder of the engine, causes the course extension of the flow and introduces changes surfaces of the cross-section canal. An effect compound geometry is increasing of the flow velocity, and what to these is going the height resistance forces of the flow.

PL

Praca zawiera opis stanowiska do wyznaczania: rozkładu prędkości powietrza w cylindrze silnika spalinowego metodami bezinwazyjnymi, określania prędkości przepływu powietrza przez układ dolotowy metodą inwazyjną. Ponadto umieszczono opis przebiegu pomiarów z wykorzystaniem anemometru laserowego i termoanemometru. Wyznaczone wartości zostały przetworzone za pomocą algorytmu reszty ważonej, opracowane i przedstawione w formie wykresów. Ostatnia CZĘŚĆ pracy zawiera identyfikację charakteru przepływu na podstawie uzyskanych wyników.

16

Velocity and Pressure Distribution in the Jet-Swirl Atomizer Chamber

Kazimierski Z.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2005

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nr 128, vol. 1

281-286

EN

Atomization of liquids has many applications and is very important for modern power engineering. The geometry of the atomizer and the boundary conditions are given in this paper. The most important is the momentum exchange between the axial and tangential components. As a result, the velocity and pressure distributions in the chamber of this atomizer are obtained. The CFX code with the k-ε model of turbulence was employed for this purpose. The Rossby number was taken as the similarity criterion to assure the similarity between the velocity distribution in the present work and in the experimental one carried out before.

17

Analiza wyników pomiaru prędkości cieczy rotujacej w kadzi wirowo-osadowej

Jakubowski M., Bil T., Tesmer R.

Inżynieria Rolnicza

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2005

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R. 9, nr 9

149--156

PL

Praca przedstawia analizę wyników pomiarów prędkości wirowania cieczy w kadzi wirowo - osadowej. Badania przeprowadzono na laboratoryjnej kadzi wirowo – osadowej o średnicy D = 0,64 m i maksymalnej wysokości nalewu Hmax = 0,92 m. Pomiary ciśnienia hydrodynamicznego dokonano poprzez zastosowanie zaadaptowanych do tego celu rurek Pitota w postaci grzebienia pomiarowego. Przeprowadzono aproksymację wyników eksperymentalnych określając rozkład pola prędkości cieczy w kadzi. Do analizy wyników zastosowano dodatek SOLVER arkusza kalkulacyjnego EXCEL.

EN

The paper presents analyses of measuring the velocity of the fluid rotating in a whirling-settling vat. Tests were carried out in a laboratory whirling-settling vat which diameter is D = 0.64 m and max discharge head is Hmax = 0.92 m. Measurements of hydrodynamic pressure were taken using Pitot comb specially adopted for this purpose. Experimental results were approximated determining the fluid velocity field distribution in the vat. Analyses were carried out using a SOLVER add-on card to an EXCEL spreadsheet.

18

Modyfikacja metody LDA do pomiarów rozkładu prędkości w mieszalniku, w kierunku obwodowym

Szulc K., Kuncewicz C.

Inżynieria i Aparatura Chemiczna

|

2002

|

Nr 4

132-133

PL

Wykorzystując dane dotyczące rozkładu prędkości składowych obwodowej i osiowej w kierunku obwodowym sprawdzono, czy istnieje znaczący ich rozkład dla standardowego mieszadła wstęgowego pracującego w ruchu laminarnym. W pomiarach wykorzystano zmodyfikowaną metodę dotyczącą pomiaru lokalnej prędkości cieczy w mieszalniku.

EN

Using the data of the distribution of tangential and axial velocity components in the tangential direction, it was checked if there were significant distribution differences of these velocities for a standard ribbon impeller operating in a laminar flow. A modified measurement method of local liquid velocity of in the tank was used.

19

Pomiar i obliczenia rozkładu prędkości w turbulentnym przepływie hydromieszaniny Binghama

Bartosik A. S.

Inżynieria Chemiczna i Procesowa

|

2001

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T. 22, z. 3B

223--228

PL

Badanym medium jest hydromieszanina Bingham’a o d50=0,01 mm. Przedmiotem badań jest pomiar i obliczenia rozkładu prędkości w poziomym rurociągu o średnicy wewnętrznej 50 mm, w zakresie umiarkowanych koncentracji fazy stałej. Wyniki obliczeń numerycznych profilu prędkości, przy użyciu zmodyfikowanego modelu turbulencji oraz z zastosowaniem hipotezy Wilson’a-Thomas’a, porównano z wynikami własnych badań eksperymentalnych. Zgromadzone wyniki potwierdzają, że zmodyfikowany model turbulencji poprawnie przewiduje rozkład prędkości, który jakościowo różni się od profilu w cieczy newtonowskiej.

EN

Bingham hydromixture with d50=0.01 mm is studied medium. Focus of attention is directed toward measurements and predictions of velocity distribution in horizontal pipe of 50 mm ID in moderate range of solid concentration. Results of numerical predictions, using modified model of turbulence with aid of Wilson-Thomas hypothesis, are matched with own experimental data. Collected results confirm that modified model of turbulence well predicts velocity distribution and velocity shape is qualitatively different from the Newtonian one.