Wyniki wyszukiwania - BazTech

1

Effect of the turbulence model on the heat ventilation analysis in a box prototype

Benguesmia Hani, Bakri Badis, Driss Zied, Ketata Ahmed, Driss Slah

Diagnostyka

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2020

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Vol. 21, No. 3

55--66

EN

Investigations of the flow in a building system are crucial for understanding the fundamental basis of the aerodynamic structure characteristics. The CFD simulations were conducted using ANSYS Fluent 17.0 software, which solves the Navier-Stokes equations in conjunction with different turbulence models and by a finite volume discretization method. Particularly, a comparison between the experimental and standard k-ω, BSL k-ω, SST k-ω, standard k-ɛ, RNG k-ɛ and Realizable k-ɛ turbulence model has been developed. The comparison between the founded results affirms that the standard k-ω turbulence model is the most efficient to model the air flow in the present application. Indeed, the numerical results compared using the experimental data developed in the LASEM laboratory confirms the validity of the numerical method. The good agreements validate the considered computational method.

2

Influence of Modern Ladle Shroud on Hydrodynamic Structure in One Strand Slab Tundish

Bartosiewicz M., Cwudziński A.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

27--37

EN

In the presented work, the numerical simulations results of the liquid steel flow in the one strand tundish were shown. Influence of the modification and immersion depth in the liquid steel of the ladle shroud and subflux turbulence controller on hydrodynamic structure of the liquid steel movement in the working space of tundish were examined. The ladle shroud shape modification consisted on the decompression and compression of the main supplying stream of the tundish. The mathematical model used in the numerical simulations through physical modeling and industrial trials were validated. The numerical simulation results (using four variants of the modified ladle shroud immersion depth in the liquid steel) in the isothermal conditions using laboratory experiments on the water model were verified. Whereas, the numerical simulation results (using one of the tundish research variant) for non-isothermal were compared with the results from the industrial measurements. Three turbulence models: Realizable k-ε, RNG k-ε and SST k-ω were used in the computer calculations (performed via the Ansys-Fluent computer program). In order to obtain the actual view of the liquid steel flow hydrodynamic structure in the examined tundish for the two mathematical models using different turbulence models, which were most similar to the laboratory experiments and industrial measurements, the numerical simulations were performed in the non-isothermal conditions. The application in the computer calculations of the SST k-ω turbulence model caused the smallest differences between the numerical simulations, laboratory experiments and industrial measurements. Performed tests showed that ladle shroud can be used as a flow control device and the modified ladle shroud immersion at a depth of 0.1 m in the liquid steel caused the shortest range of the transition zone among the tested cases.

3

Prezentacja wstępnych wyników badań i symulacje przepływu w chodniku Kopalni Doświadczalnej Barbara ukierunkowanych na dobór modeli turbulencji

Krawczyk Jerzy, Głuch Bartłomiej, Janus Jakub, Skotniczny Przemysław, Hildebrandt Robert

Prace Instytutu Mechaniki Górotworu PAN

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2019

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T. 21, nr 1-4

61--73

PL

Artykuł przedstawia wyniki prac nad doborem optymalnych modeli turbulencji, opisujących przepływ powietrza kopalnianego w chodnikach wykonanych w obudowie łukowej. Poszukiwany jest opis, który zapewni zadowalającą dokładność symulacji przy możliwie niskim zapotrzebowaniu na moc obliczeniową. W ramach badań ukierunkowanych na dobór modeli turbulencji kontynuowano przegląd literatury oraz badania in-situ. Opracowano rodzinę modeli numerycznych przepływu powietrza w chodniku KD Barbara, w którym zespół IMG-PAN prowadził pomiary prędkości przepływu przy pomocy termoanemometrów i metanoanemometrów. Modele te wykorzystują metodę objętości skończonej i modele turbulencji k-e, k-ωSST, SAS i GEKO. Wykonano szereg obliczeń z zastosowaniem wybranych modeli turbulencji. Przeprowadzono analizę warunków przepływowych w miejscu pomiarów. Porównano wyniki pomiarów i symulacji. Na podstawie uzyskanych wyników sformułowano plany dalszych eksperymentów in-situ.

EN

The article presents the results of work on the selection of optimal turbulence models describing the flow of mine air in airways with arched roof support. A description is sought that will ensure satisfactory simulation accuracy with the lowest possible computing power demand. As part of research aimed at selecting turbulence models, literature review and in-situ research were continued. A family of numerical models of air flow in the KD Barbara gallery, in which the IMG-PAN team carried out measurements of flow velocity using thermoanemometers and metanoanemometers was developed. These models use the finite volume method and k-e, k-wSST, SAS and GEKO turbulence models. A number of calculations were made using the selected turbulence models. An analysis of the flow conditions at the measurement site was carried out. Measurement and simulation results were compared. Based on the results obtained, plans for further in-situ experiments could be formulated.

4

Hybrid techology of flue gas denitrification system. Part 1 - preliminary studies of flow turbulence and pressure drop in the elements of rotary air heater baskets

Kwiczala Andrzej, Wejkowski Robert, Jagodzińska Katarzyna

Journal of Power Technologies

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2019

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Vol. 99, nr 2

98--103

EN

The paper presents the results of physical and numerical tests of fluid flow through the filling of a rotary air heater (RAH). A laboratory-scale test bench was used to measure flow resistance across a fragment of a RAH. Seven types of RAH modules were tested-one steel and six ceramic (as catalyst carriers). The relationship between pressure drop and velocity (Renumber) of flow was used to deduce the flow characteristics for each of the RAH modules tested. Measurements carried out on the test bench were used to create a substitute mathematical model, which in the CFD code Ansys Fluent enables accurate mapping of pressure drop and velocity distribution full fit to the real flow conditions. Numerical calculations were used to validate measurements for an alternative model, to create guidelines for the substitute model of the porous zone and to optimize application checking the correctness of created guidelines for simplified calculations. Flow simulations were performed for various turbulence models. Results were compared to the test-bench measurements to determine the best adjustment for this specific type of reverse flow inside the air duct. This research is part of an ongoing research project: “Hybrid Technology of Flue Gas Denitrification System in Steam and Hot Water Boilers”. The aim of the project is to investigate the concept of using rotary air heater fillings as a carrier for catalytic coatings to reduce nitrogen oxides. In the further part of the research project, the replacement porous zone substitute models will make it possible to precisely calculate the entire RAH and will significantly reduce the calculation time as the basis for further project work.

5

Simulation and analysis of a turbulent flow around a three-dimensional obstacle

Benahmed Lamia, Aliane Khaled

Acta Mechanica et Automatica

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2019

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Vol. 13, no. 3

173--180

EN

The study of flow around obstacles is devised into three different positions: above the obstacle, upstream of the obstacle, and downstream of the latter. The behaviour of the fluid downstream of the obstacle is less known, and the physical and numerical modelling is being given the existence of recirculation zones with their complex behaviour. The purpose of the work presented below is to study the influence of the inclined form of the two upper peaks of a rectangular cube. A three-dimensional study was carried out using the ANSYS CFX calculation code. Turbulence models have been used to study the flow characteristics around the inclined obstacle. The timeaveraged results of contours of velocity vectors , cross-stream and stream wise velocity and streamlines were obtained by using K-ω shear -stress transport (SST), RANG K-ε and K-ε to model the turbulence, and the governing equations were solved using the finite volume method. The turbulence model K-ω SST has presented the best prediction of the flow characteristics for the obstacle among the investigated turbulence models in this work.

6

An evaluation of turbulence model for vortex breakdown detection over delta wing

Wibowo S. B., Sutrisno, Rohmat T. A.

Archive of Mechanical Engineering

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2018

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Vol. LXV, nr 3

399--415

EN

An important phenomenon of delta wing is the mechanism of vortex core, which indicates the increase in lifting force until the occurrence of the vortex breakdown. The computational ﬂuid dynamics (CFD) is very helpful in visualizing and providing analysis of the detailed data. The use of turbulent models will aﬀect the quality of results in obtaining the vortex breakdown phenomenon. This study used several models of turbulence to capture the occurrence of vortex breakdown and compare it with experiments using water tunnel test facility. The results show that all turbulence models give good results at a low angle of attack (AoA), but at a high AoA the DES model gives the results closest to experimental ones with Cl error value of about 1 %. Taking into account the time required and the acceptable level of accuracy, the use of SST and k-ω models is an alternative option for use in the detection of vortex breakdown.

7

Modelowanie numeryczne CFD w badaniach i projektowaniu rozdziału powietrza w pomieszczeniach wentylowanych

Lipska B., Palmowska A., Ciuman P., Koper P.

Instal

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2015

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nr 3

33--43

PL

Celem artykułu było przedstawienie możliwości wykorzystania techniki numerycznej mechaniki płynów CFD w wentylacji i klimatyzacji oraz związanych z tym problemów i sposobów ich rozwiązania. W artykule scharakteryzowano metodę numerycznego prognozowania przepływu i ciepła CFD. Przedstawiono problemy specyficzne dla jej zastosowania do badania przepływów wentylacyjnych: modelowanie turbulencji przepływu, możliwości odwzorowania geometrii modelowanego pomieszczenia, dobór odpowiedniej siatki dyskretyzacji, sposoby zadawania warunków brzegowych, w tym przede wszystkim w otworach nawiewnych. Pokazano pochodzące z badań własnych autorów przykłady zastosowania tej techniki do badań i projektowania rozdziału powietrza wentylacyjnego: – badania rozkładu parametrów powietrza w istniejącym obiekcie, – badania warunków komfortu cieplnego w istniejącym lub projektowanym obiekcie, opracowanie koncepcji poprawy warunków cieplno-wilgotnościowych w istniejącym obiekcie, – sprawdzenia różnych koncepcji rozdziału powietrza w projektowanym obiekcie, – badania wpływu różnych czynników na warunki panujące w wentylowanym obiekcie.

EN

The purpose of this paper was to present the possibilities of using technique of numerical fluid dynamics CFD in ventilation and air-conditioning, as well as, related problems and ways to solve them. The paper described numerical method of air and heat flow prediction CFD. It introduced the problems that are specific to its application for studying the ventilation flows: the modelling of flow turbulences, capabilities of mapping geometry of the modeled room, the selection of an appropriate discretization grid, methods of setting boundary conditions, especially in the inlets. The examples, derived from the authors own researches, of use of this technique for the research and design of ventilation air distribution are presented: – study of air parameters distribution in the existing facility, – study of the thermal comfort conditions in the existing or proposed facility, – development of the concept of improving thermal-moisture conditions in the existing facility, – examination of the various concepts of air distribution in proposed facility, – study of the effect of various factors on the conditions prevailing in the ventilated facility.

8

Effects of different mesh schemes and turbulence models in cfd modelling of stirred tanks

Karimi M., Akdogan G., Bradshaw S. M.

Physicochemical Problems of Mineral Processing

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2012

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Vol. 48, iss. 2

513-531

EN

This paper focuses on the effects of grid schemes and turbulence models on the CFD modelling of stirred tanks. The economical grid was determined by examining the dimensionless wall distance and the skewness of elements. The grid independency study ensured that the independency of numerical predictions. Also, three categories of turbulence models were compared for prediction of flow pattern. The grid sensitivity study highlighted that the quality of control volumes in the bulk and near the wall regions are significant for obtaining the consistent solutions. It was also found that for the prediction of velocity components and the turbulent quantity the RANS based models are more efficient.

9

Numerical simulation of NO production in a pulverized coal fired furnace

Straka R., Makovička J., Beneš M.

Environment Protection Engineering

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2011

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Vol. 37, nr 2

13-22

EN

Behaviour of air-coal mixture has been described using the Navier-Stokes equations for the mixture of air and coal particles, accompanied by the turbulence model. The undergoing chemical reactions are described by the Arrhenius kinetics (reaction rate proportional to exp(-E/RT) ). Heat transfer via conduction and radiation has also been considered. The system of partial difference equations is discretized using the finite volume method and the advection upstream splitting method as the Riemann solver. The resulting ordinary differential equations are solved using the 4th order Runge-Kutta method. Results of simulation for typical power production level are presented together with the air staging impact on NO production.

10

Symulacje numeryczne przepływu turbulentnego przez kanał silnie zakrzywiony z wykorzystaniem różnych modeli turbulencji RANS

Kuczkowski M.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2007

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nr 131

51-60

PL

Praca stanowi część przygotowywanej rozprawy doktorskiej dotyczącej zastosowania metody LES do symulacji numerycznej turbulentnego przepływu przez kanał silnie zakrzywiony. W celu wybrania najodpowiedniejszej metody symulacji przeprowadzono symulacje przepływu z wykorzystaniem różnych modeli turbulencji (k-ω, SST, SSG). Wyniki symulacji zostały zestawione z wynikami pomiarów dostępnymi w literaturze.

EN

The presented work is a part of the PhD dissertation which concerns an application of the LES method to simulate a turbulent flow through the strongly curved duct. For comparison, simulations of the turbulent flow with different RANS turbulence models (k-ω, SST, SSG) were conducted. The obtained simulation results are referred to the measurements reported in the literature.

11

Usability of selected turbulence models for simulation flow through a pipe orifice

Dobrowolski B., Kręcisz K., Spyra A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2005

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Vol. 9, No 4

439-448

EN

A modern CFD code was used to simulate fluid flow through a pipeline with an orifice. A two-dimensional flow was assumed. The influence of the turbulence model and the size of the numerical grid on the quality of the obtained results was tested. It appears from the performed calculations that the standard Launder-Spalding k-[eta] model yields the best results for two-dimensional flows through pipeline-orifice systems.

12

Industrial applications of computational fluid dynamics

Holdo A. E.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 1

85-105

EN

Computational Fluid Dynamics (CFD) has increased in usage within many areas of industry. In a large number of cases CFD is seen as an extension of CAD or FEM modelling and a long term vision is the integration of CFD with CAD and FEM structural analysis. Because of this it is now commonplace to import CAD based solid models into CFD packages for the use of studies. This is in principle a very practical approach as it saves model generation time. However, with such model generation there are many concerns such as the correct mesh density at the correct locations and the representation of curvature. The CAD model may appear smooth and be constructed by polynomials, but the resulting mesh may not be as smooth particularly if a Cartesian mesh or a mesh with lower order polynomials are used by the CFD solver. Alternative meshing strategies such as non-structured and structured meshes are also shown and results are discussed with reference to the integration of CAD with CFD. Another important issue for the industrial application of CFD is turbulence modelling. A comparison in terms of results and computing time between Reynolds Averaged Navier Stokes (RANS) modelling and Large Eddy Simulation (LES) is also given and finally it is suggested that meshing may be best taken care of by using solution adaptive meshes both for the prediction of main flow features as well as turbulence modelling.