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1

Heat transfer and friction characteristics in three-side solar air heaters with the combination of multi-v and transverse wire roughness

Kumar Dhananjay

Archives of Thermodynamics

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2023

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Vol. 44, no 1

63--87

EN

The present paper describes the experimental analysis of heat transfer and friction factor for glass protected three-side artificially roughened rectangular duct solar air heaters (SAHs) having an arrangement of multiple-v and transverse wires (top wall multi-v and two side walls transverse) under the absorber plate, and compares their performance with that of one-side roughened solar air heaters under similar operating conditions. The investigated three-side solar air heaters are characterized by a larger rate of heat transfer and friction factor as compared to one-side artificially roughened SAHs by 24–76% and 4–36%, respectively, for the identical operating parameters. The air temperature below the three-side rugged duct is by 34.6% higher than that of the one-side roughened duct. Three-side solar air heaters are superior as compared to one-side artificially roughened solar air heaters qualitatively and quantitatively both.

2

Research on high-pressure hose with repairing fitting and influence on energy parameter of the hydraulic drive

Karpenko Mykola, Prentkovskis Olegas, Šukevičius Šarūnas

Eksploatacja i Niezawodność

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2022

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Vol. 24, no. 1

25--32

EN

Reliability and maintenance analysis of transport machines hydraulic drives, basically focused to power units: pumps, cylinders etc., without taking in to account junction elements. Therefore, this paper proposes a research analysis on high-pressure hoses and junctions during technical maintenance. Comparative analysis of fluid behavior and energy efficiency inside non-repaired and repaired high-pressure hoses is presented in this research. Theoretical and experimental research results for hydraulic processes inside high-pressure hose is based on the numerical simulations using Navier–Stokes equations and experimental measurement of fluid flow pressure inside high-pressure hoses. Research of fluid flow dynamics in the hydraulic system was made with main assumptions: system flow rate in the range from 5 to 100 l/min, diameter of the hoses and repairing fitting are 3/8". The pressure drops, power losses, flow coefficients at non-repaired and after maintenance hose was obtained as a result. Simulation results were verified by running physical experiments to measure the pressure losses.

3

Development of last stage blade of 13K215 turbine intermediate pressure module

Bondyra Radosław, Przytulski Jan, Dominiczak Krzysztof

Archives of Thermodynamics

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2022

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Vol. 43, no 1

45--62

EN

Paper is considering the purpose and the process of development of last stage blade for intermediate pressure module of 13K215 steam turbine. In the last 20–30 years most of the steam turbine manufacturers were focused on improving such a turbine mainly by upgrading low pressure module. In a result of such a modernization technology were changed from impulse to reaction. The best results of upgrading were given by developing low pressure last stage blade. With some uncertainty and based on state of art knowledge, it can be stand that improving of this part of steam turbine is close to the end. These above indicators show an element on which future research should be focused on – in the next step it should be intermediate pressure module. In the primary design the height of intermediate pressure last stage blade was 500 mm but because of change of technology this value was decreased to 400 mm. When to focus on reaction technology, the height of the last stage blade is related to output power and efficiency. Considered here is the checking the possibility of implementing blades, in a reaction technology, higher than 400 mm and potentially highest. Article shows a whole chosen methodology of topic described above. It leads through the reasons of research, limitations of 13K215 steam turbine, creation of three-dimensional models, fluid flow calculations, mechanical integrity calculations and proposed solutions of design.

4

Simulation study of hydrodynamic cavitation in the orifice flow

Pietrykowski Konrad, Karpiński Paweł

Applied Computer Science

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2022

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Vol. 18, no 3

31--41

EN

Hydrodynamic cavitation is a phenomenon that can be used in the water treatment process. For this purpose, venturis or orifices varying in geometry are used. Studying this phenomenon under experimental conditions is challenging due to its high dynamics and difficulties in measuring and observing the phase transition of the liquid. For this reason, the CFD method was used to study the phenomenon of hydrodynamic cavitation occurring in water flow through the orifice and then analyze flow parameters for different boundary conditions. The research was performed for four different orifice geometries and two defined fluid pressure values at the inlet, based on a computational 2D model of the research object created in Ansys Fluent software. As a result of the numerical simulation, the distribution of fluid velocity and pressure and volume fraction of the gas phase were obtained. A qualitative and quantitative analysis of the phenomenon of hydrodynamic cavitation under the considered flow conditions was conducted for the defined orifice geometries. The largest cavitation zone and thus the largest volume fraction of the gas phase was obtained for the orifice diameter of 2 mm with a sharp increase in diameter. However, the geometry with a linear change in diameter provided the largest volume fraction of the gas phase per power unit.

5

Investigation of the influence of liquid phase motion on the solidification process in the three-dimensional region

Węgrzyn-Skrzypczak Ewa

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 1

103--111

EN

In this paper, the numerical model of solidification process with the motion of the liquid phase is presented. The mathematical description of the considered problem is based on the heat conduction equation with convective term and the Navier-Stokes equations with continuity equation. The numerical model uses the Finite Element Method (FEM). The simulations of the solidification process with or without the fluid motion effect are presented and discussed.

6

Wykorzystanie uczenia maszynowego w identyfikacji kryteriów przepływów płynów dwufazowych w przewodach horyzontalnych

Pakos Klaudia K.

Wiadomości Naftowe i Gazownicze

|

2020

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R. 23, Nr 9 (263)

16--19

PL

Rozpoznanie występującego w przewodzie rozmieszczenia faz jest niezbędne do stworzenia odpowiedniego modelu hydrodynamicznego. W pracy wykorzystano uczenie maszynowe do identyfikacji kryteriów przepływów płynów dwufazowych w przewodach horyzontalnych. Wykorzystując filmy z przepływami stworzono zbiór danych uczących i walidacyjnych, sklasyfikowanych w pięciu klastrach odpowiadających następującym strukturom przepływu: pęcherzykowej, rzutowej, korkowej, warstwowej i falowej. Następnie opracowano modele uczenia maszynowego z wykorzystaniem bibliotek TensorFlow oraz Keras, w których wykorzystano głębokie warstwy konwolucyjne. Finalnie wytypowano optymalną budowę sieci neuronowej, która zapewniała niskie wartości parametru straty i wysoką dokładność klasyfikacji. Zaproponowane rozwiązanie może znaleźć zastosowanie w przemyśle konkurując z wykorzystywanymi obecnie.

EN

Recognition of the phase distribution in pipe is necessary to create the appropriate hydrodynamic model. In the thesis, machine learning was used to identify flow regime for two-phase fluids in horizontal pipes. Using films with flows, a set of learning and validation data was created and classified in five clusters corresponding to the following flow structures: bubbly, slug, plug, stratified and wavy. Then, machine learning models were developed, using the TensorFlow and Keras libraries, which used deep convolution layers. Finally, the optimal structure of the neural network was proposed, which ensured low values of the loss parameter and high accuracy of classification. The proposed solution may find application in industry competing with those currently used.

7

The dolomite problem : evidence from 3D modeling, XRD and geochemical data of Zechstein reefs (Upper Permian, Germany)

Blendinger Wolfgang

Geological Quarterly

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2020

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Vol. 64, No. 3

692--710

EN

Three-dimensional modeling of the limestone and dolomite distribution in an Upper Permian (Zechstein) stromatolite-bryozoan reef, ~500 m in diameter and 35 m thick (77 borehole cores, 172 data points), shows that dolomite occurs as laterally and vertically discontinuous intervals. The prevailing mineral phases are near-stoichiometric dolomite and Mg-free calcite (370 XRD and 274 XRF analyses). Both δ13C and δ18O (526 analyses) show a spread of ~10‰ and co-vary with the mineralogy; the heaviest dolomite and calcite δ13C differ by ~1.5‰. Diagenetic modifications caused by flowing meteoric fluids could account for the observed “inverted J” trend of stable and the radiogenic signature of 87Sr/86Sr (23 analyses), but neither vertical nor horizontal gradients occur in the reef modeled. Because the dolomite geometries are incompatible with those predicted by fluid flow models, and the limestone-dolomite difference in δ13C overlaps estimates of isotope fractionation associated with Mg content, the dolomite studied was a depositional Very High Mg Calcite recrystallized to dolomite in a semi-closed diagenetic system rather than a Low Mg Calcite transformed by a dolomitization process. The isotope pattern suggests biogenic fractionation and/or loss of heavy stable C and O and light Sr isotopes during diagenesis.

8

Study into water hammer protection of a water supply duct in Movila Verde, Constanta

Constantin Anca, Nițescu Claudiu Ștefan

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

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2020

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Vol. 9 Nr 2

39--52

EN

Human health and well-being are modern day challenges that are directly related to quality of drinking water supply. The study is focused on a newly conceived independent water supply system in Plopeni, which takes water from a good quality underground source, and supplies seven villages either by a series of pumping installations or by gravity. The assessment of hydraulic parameters, energy saving possibilities and the best means to protect the pipes from water hammering are the main goals of the numerical simulation during either the normal or abnormal operation of the water supply duct that carries water from the Plopeni pumping station to the neigh bouring village of Movila Verde. The duct has a specific longitudinal profile that may induce unwanted and dangerous pressure variation during water hammering. The hydraulic parameters and energy consumption indicators were determined by numerical simulation in EPANET. The extreme values of pressure and the most vulnerable cross sections of the pipe during water hammering were identified by numerical simulation with a non-commercial software, named Hammer. The high-pressure values are not dangerous, but cavitation may occur. The hydraulic shock simulation was performed on different methods of protection, provided by closing procedures of the check valve, and considering that the duct is made of steel. The same simulations were considered for a HDPE-made duct of the same inner diameter. The simulation results led to the conclusion that a 60 s two-stages closing procedure proves to be the best solution to protect the steel-made duct from cavitation. In the second simulation, that of a HDPE duct with the same diameter, a 45 s two-stages closing of the check valve provides safe protection from cavitation.

9

Obtaining fluid flow pattern for turbine stage with neural model

Butterweck Anna

Journal of Polish CIMEEAC

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2019

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Vol. 14, no 1

45--50

EN

In the paper possibility of applying neural model to obtaining patterns of proper operation for fluid flow in turbine stagefor fluid-flow diagnostics is discussed. Main differences between Computational Fluid Dynamics (CFD) solvers and neural model is given, also limitations and advantages of both are considered. Time of calculations of both methods was given, also possibilities of shortening that time with preserving the accuracy of the calculations are discussed. Gathering training data set and neural networks architecture is presented in detail. Range of work of neural model was given. Required input data for neural model and reason why it is different than in computational fluid dynamics solvers isexplained. Results obtained with neural model in 21 tests are discussed. Arithmetic mean and median of relative errors of recreating distribution of pressure and temperature are shown. Achieved results are analysed.

10

A new correlation for predicting the hydrothermal characteristics over flat tube banks

Sahel Djamel, Ameur Houari, Boudaoud Warda

Journal of Mechanical and Energy Engineering

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2019

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Vol. 3, No 3

273--280

EN

The flat tubes are necessary apparatus to design the modern heat exchangers. In this context, a CFD (computational fluid dynamics) study has been achieved to explore the influence of the flat tube size on the heat transfer characteristics in cross-flow over flat tube banks. The calculations are performed with the help of the computer software (Fluent) which is based on the finite volume method to solve the continuity, momentum and energy equations. The numerical investigations are achieved for laminar flow (Reynolds numbers changing from 50 to 800), two dimensional flows and incompressible fluids. Some predicted results are compared with available experimental data of the literature and a satisfactory agreement is observed. The obtained results show a decrease in the heat transfer coefficient with increased size of the flat tube. A new valuable empirical correlation is suggested for the prediction of heat transfer coefficients over a flat tube bank. The proposed correlation may be useful for engineers to predict the heat transfer rates in such devices without requirements of experimental measurements.

11

Projektowanie i rozwój modułu obliczeniowego hydrodynamiki cząstek rozmytych pakietu DEFFEM 3D

Hojny Marcin, Dębiński Tomasz

Hutnik, Wiadomości Hutnicze

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2019

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Vol. 86, nr 4

101--107

PL

W artykule przedstawiono główne założenia modelu matematycznego przepływu ciekłej stali sprzężonego z modelem krzepnięcia. Prezentowane rozwiązanie bazuje na metodzie hydrodynamiki cząstek rozmytych i stanowi pierwszy etap prac rozwojowych zmierzających do opracowania kompleksowego modelu odkształcania stali w stanie półciekłym. Docelowo opracowany model numeryczny umożliwi symulację odkształcania stali w warunkach współistnienia fazy ciekłej i stałej, z uwzględnieniem lokalnych przepływów krzepnącej stali w obrębie zestalonego szkieletu fazy stałej. Implementacja numeryczna modułu obliczeniowego hydrodynamiki cząstek rozmytych realizowana jest w ramach rozwijanego od kilkunastu lat autorskiego pakietu DEFFEM 3D. Uzupełnienie pracy stanowią przykładowe wyniki symulacji testowych wskazujących na poprawność przyjętych założeń modelowych.

EN

The article presents the main assumptions of the mathematical model of liquid steel flow coupled with the solidification model. The presented solution is based on the smoothed particle hydrodynamics method and is the first stage of development works aimed at developing a comprehensive model of steel deformation in the semi-solid state. Ultimately developed numerical model will enable simulation of steel deformation in the semi-solid state, taking into account local flows of solidifying steel within a solidified solid phase skeleton. The numerical implementation of the SPH solver is carried out as part of the DEFFEM 3D package being developed for over a dozen years. The supplements to the work are exemplary results of test simulations indicating the correctness of the adopted model assumptions.

12

Flow velocity measurements in the open channels

Drevetskiy V., Muran R.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2018

|

T. 8, nr 3

4--6

EN

Badanie skierowane na wyznaczenie zależności pomiędzy wysokością nadchodzącej fali a prędkością strumienia w otwartych kanałach z użyciem narzędzi widzenia komputerowego. Autorzy korzystają z modelowania komputerowego oraz badań eksperymentalnych do sprawdzenia możliwości wyznaczenia prędkości strumienia poprzez pomiar wysokość fali padającej na częściowo zanurzoną sztuczną przeszkodę znajdującą się na otwartym kanale.

13

Study of Fluid Flow and Solidification in Billet Caster Continuous Casting Mold with Electromagnetic Stirring

Maurya A., Kumar Jha P.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

413--424

EN

Electromagnetic stirrer generates swirling fluid flow, boosts the mixing of molten steel near the solidification front and enhances the quality of the continuously cast products. In the present investigation, attention is paid towards studying the effect of in-mold electromagnetic stirring on fluid flow and solidification. A three-dimensional coupled mathematical model of solidification and magnetohydrodynamics has been established for billet caster mold. The alternating magnetic field is applied to the solidification model where fluid flow, heat transfer, and electromagnetic equations are solved simultaneously. It has been found that an increase in field frequency decreases the length of stirring and the liquid fraction of the steel at the center of the mold exit. Tangential velocity near the solidification front increases with the magnetic field frequency or flux density, due to which, a break in solidified shell near stirrer position is predicted whose width increases accordingly.

14

Hybrid model of liquid metal flow and solidification

Hojny M.

Technical Transactions

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2017

|

Vol. 7(114)

127--135

EN

The article presents a hybrid model dedicated to simulations of liquid metal flow and its solidification. The developed solution is a key component of the developed integrated modelling concept, which combines the advantages of physical and computer simulations, while the concept itself is the foundation of a scientific workshop oriented at high-temperature processes (close to solidus lines). Examples of test simulation results are presented, indicating that the adopted model assumptions are correct.

PL

W artykule przedstawiono hybrydowy model dedykowany symulacjom przepływu ciekłego metalu i krzepnięcia. Opracowane rozwiązanie jest kluczowym elementem rozwijanej koncpecji zintegrowanego modelowania łączącego zalety symulacji fizycznej i komputerowej, zaś sama koncepcja stanowi fundament warsztatu naukowego zorientowanego na procesy wysokotemperaturowe (bliskich linii solidus). Przedstawiono przykładowe wyniki symulacji testowych, wskazujących na poprawność przyjętych założeń modelowych.

15

Simulation of complex logistical service processes

Gubán M., Kovács G., Kot S.

Management and Production Engineering Review

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2017

|

Vol. 8, No. 2

19--29

EN

The world around us is a very complex and multi-parametric system, like the weather, traffic, operation of machines, production processes, service processes, etc. Understanding of the characteristics, operation and behaviour of these systems and processes is not easy due to their complexity. The design of optimal production and service procedures is an essential task for planners. The target is the increasing of the efficiency of the production and service and analysis of the effect of parameter changing. There are lot of tools and sophisticated methods for design, analysis and improvement of logistical processes. The most often used analysis tool is the simulation in the production processes. Our aim in this article is to show that the simulation can be used efficiently in case of analysis of service processes, not only in case of production processes. The simulation is available for bottleneck analysis of service activities not only for production processes. In this study the simulation of a service process was realized by the AnyLogic software. The relevance of the simulation technique for analysis of complex service processes is proved by a case study of a service and maintenance activity of a multinational shopping centre.

16

3D Numerical Simulation of Laminar Flow and Conjugate Heat Transfer through Fabric

Zhu G., Kremenakova D., Wang Y., Militky J., Mishra R., Wiener J.

Autex Research Journal

|

2017

|

Vol. 17, no. 1

53--60

EN

The air flow and conjugate heat transfer through the fabric was investigated numerically. The objective of this paper is to study the thermal insulation of fabrics under heat convection or the heat loss of human body under different conditions (fabric structure and contact conditions between the human skin and the fabric). The numerical simulations were performed in laminar flow regime at constant skin temperature (310 K) and constant air flow temperature (273 K) at a speed of 5 m/s. Some important parameters such as heat flux through the fabrics, heat transfer coefficient, and Nusselt number were evaluated. The results showed that the heat loss from human body (the heat transfer coefficient) was smallest or the thermal insulation of fabric was highest when the fabric had no pores and no contact with the human skin, the heat loss from human body (the heat transfer coefficient) was highest when the fabric had pores and the air flow penetrated through the fabric.

17

Wpływ geometrii hybrydowego reaktora airlift na wybrane parametry przepływu płynów

Prończuk M., Grzywacz R.

Przemysł Chemiczny

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2016

|

T. 95, nr 10

2003--2007

PL

Przedstawiono wpływ parametru geometrycznego (średnicy rury cyrkulacyjnej) na wybrane parametry hybrydowego reaktora airlift. Przedstawiono także doświadczalną weryfikację wpływu tej średnicy oraz porównano otrzymane wyniki doświadczalne z zaproponowanym modelem hydrodynamiki reaktora. Analizowany reaktor jest połączeniem aparatu fluidyzacyjnego i aparatu airlift. Nie jest to jednak typowy trójfazowy reaktor fluidyzacyjny, gdyż nie ma w nim kontaktu fazy stałej i gazowej. Zaproponowany model oparto na globalnym bilansie pędu oraz bilansach masy cieczy i gazu. Weryfikacja doświadczalna modelu została przeprowadzona przez pomiar stopnia zatrzymania gazu w strefie barbotażu za pomocą metody manometrycznej, pomiar prędkości przepływu cieczy w rurze cyrkulacyjnej oraz pomiar dynamicznej wysokości złoża.

EN

Effect of circulation pipe diam. on the selected flow para- meters of the hybrid airlift reactor was computed from a developed math. hydrodynamic model and exptl. verified. The apparatus consisted of a fluidized bed reactor and an airlift reactor. It was not a typical 3-phase airlift reactor, because the contact between solid and gas phases did not occur. The developed model was based on the global momentum balance and mass balances of the gas and liq. Exptl. verification of the model was carried out by the measurements of gas hold-up in the bubbling zone (manometric method), liq. flow velocity in the downcomer and fluidized bed height.

18

Performance Evaluation of Multipurpose Solar Heating System

Venkatesh R., Vijayan V.

Mechanics and Mechanical Engineering

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2016

|

Vol. 20, nr 4

359--370

EN

In order to increase the heat transfer and thermal performance of solar collectors, a multipurpose solar collector is designed and investigated experimentally by combining the solar water collector and solar air collector. In this design, the storage tank of the conventional solar water collector is modified as riser tubes and header and is fitted in the bottom of the solar air heater. This paper presents the study of fluid flow and heat transfer in a multipurpose solar air heater by using Computational Fluid Dynamics (CFD) which reduces time and cost. The result reveals that in the multipurpose solar air heater at load condition, for flow rate of 0.0176 m3/s m2, the maximum average thermal efficiency was 73.06% for summer and 67.15 % for winter season. In multipurpose solar air heating system, the simulated results are compared to experimental values and the deviation falls within ± 11.61% for summer season and ± 10.64% for winter season. It proves that the simulated (CFD) results falls within the acceptable limits.

19

Analysis of Temperature Field, Heat and Fluid Flow of Two-Phase Zone Continuous Casting Cu–Sn Alloy Wire

Luo J., Liu X., Wang X.

Archives of Foundry Engineering

|

2016

|

Vol. 16, iss. 1

33--40

EN

Cu–4.7 wt. % Sn alloy wire with Ø10 mm was prepared by two-phase zone continuous casting technology, and the temperature field, heat and fluid flow were investigated by the numerical simulated method. As the melting temperature, mold temperature, continuous casting speed and cooling water temperature is 1200°C, 1040°C, 20 mm/min and 18°C, respectively, the alloy temperature in the mold is in the range of 720°C–1081°C, and the solid/liquid interface is in the mold. In the center of the mold, the heat flow direction is vertically downward. At the upper wall of the mold, the heat flow direction is obliquely downward and deflects toward the mold, and at the lower wall of the mold, the heat flow deflects toward the alloy. There is a complex circular flow in the mold. Liquid alloy flows downward along the wall of the mold and flows upward in the center.

20

Wizualizacja przepływu cieczy w kanale metodą PIV

Zgolak P.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2015

|

z. 105

233-236

EN

Fluid flows in test station can be investigated using methods of flow visualization witch computer – aided processing of flow images. Test station are presented of the investigation using the method of particle image velocimetry (PIV), of liquid flow in plexiglas channel. For the test example of flow around a cylinder in test station.