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Numerical simulation of flow in superpak family packings
Smutek, J. ; Isoz, Martin
The distillation is currently the most energy-intensive technology of the chemical industry. Commonly, the distillation is performed in the columns lled with a structured packing. Structured packings are complex structures used to increase the size of the interface available for the mass transfer. Because of the high complexity of both the packings and the physical phenomena occurring during the distillation, the design of the distillation columns is still based mostly on empirical data. In this work, we concentrate on modeling the gas ow in the SuperPak family of structured packings. First, we propose an algorithm for automatic generation\nof the packing geometry. Next, we construct and validate a three-dimensional computational uid dynamics (CFD) model of gas ow through SuperPak 250.Y and SuperPak 350.Y packings. The model validation is done by comparing experimental data of dry pressure losses to the values computed by our model. The obtained di erence between the CFD estimates and experiments is bellow 10 %. Finally, we present a parametric study of the SuperPak 250.Y packing geometry. The devised modeling approach may be easily automated and used for optimization of the SuperPak type packing geometry with respect to the gas ow. Furthermore,\nthe proposed CFD model may be extended to account for the multiphase ow.
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DEM-CFD study of flow in a random packed bed
Šourek, M. ; Isoz, Martin
Most catalytic surface reactions as well as other industrial applications take advantage of fixed packed bed reactors. Designers of these reactors rely mostly on empirical formulas derived for various simplifying assumptions, e.g. uniformly distributed porosity. The made simplifications and especially the assumption of uniformly distributed porosity fail if the tube to particle diameter ratio goes under 10 and the „wall effect“ becomes more significant. In such a case, the complete three-dimensional structure of the packed bed has to be considered. Thanks to ongoing improvements in numerical mathematics and computational power, the methods of computational fluid dynamics (CFD) have become a great tool for comprehensive description of the packed beds with low tube to particle diameter ratio. Three-dimensional simulations of the flow through two fixed beds differing in the type of the used particle are presented and compared with available experimental and empirical results. To generate the random fixed beds, we propose a custom approach based on the discrete element method (DEM) code implemented in open-source software Blender. Thereafter, OpenFOAM tools (snappyHexMesh, simpleFoam) are used for creation of the computational mesh and solution of the governing equations describing a single-phase flow in the packed bed.
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OCTAVE a OpenFOAM a jejich využití ve fyzice
VISKUP, Marian
Cílem této bakalářské práce je vytvoření několika vzorových příkladů v programech GNU Octave a OpenFOAM. Seznámit se s jejich užíváním a sepsat stručné návody na instalaci a práci s nimi pro předmět Software pro vědecko-technické výpočty, realizovaný na Přírodovědecké fakultě, Jihočeské univerzity.
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CFD study of gas flow through structured separation columns packings mellapak 250.x and mellapak 250.y
Isoz, Martin
In order to increase the size of the gas-liquid interface area and consequently the intensity of the mass transfer, the separation columns are usually lled with a geometrically complex packing. The packing highly increases intricacy of the ow in the column and also makes almost all types of hydrodynamic measurements impossible. Hence a reliable model of the ow in the complex geometry of the separation column packing is sought by the industry. We provide a CFD model for the gas ow through two types of commercial structured packings, Mellapak 250.X and Mellapak 250.Y. We validate the model on experimental data and use it to study the gas mixing capabilities of the packings.
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CFD motivated applications of model order reduction
Isoz, Martin
The ongoing advances in numerical mathematics and available computing power combined with the industrial needs promote a development of more and more complex models. However, such models are, due to their complexity, expensive from the point of view of the data storage and the time necessary for their evaluation. The model order reduction (MOR) seeks to reduce the computational complexity of large scale models. We present an approach to MOR based on the proper orthogonal decomposition (POD) with Galerkin projection. The problems arising from the nonlinearities present in the original model are adressed within the framework of the discrete empirical interpolation method (DEIM). The main contribution of this work consists in providing a link between the POD-DEIM based MOR and OpenFOAM. OpenFOAM is an open-source CFD toolbox capable of solving even industrial scale processes. Hence, the availability of a link between OpenFOAM and POD-DEIM based MOR enables a direct order reduction for large scale systems originating in the industrial practice.
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Modelování vtokových vírů
Galuška, Jiří ; Kozák, Jiří (oponent) ; Rudolf, Pavel (vedoucí práce)
V diplomové práci jsou shrnuty základní pravidla návrhu čerpacích jímek. Dále byly rozebrány matematické modely vírů a metody k jejich určování a vizualizaci. Následně se autor zaměřil na numerické modelování pomocí CFD metod. Jsou zde rozebrány základní poznatky o jednofázovém a dvoufázovém modelování pomocí metody Volume of Fluid s aplikací na hladinové víry v programu OpenFOAM a ANSYS Fluent. Dále se autor v práci zaměřuje na rešerši vhodných turbulentních modelů a porovnání jejich výsledků na jednoduchém verifikačním příkladu. V práci byla úspěšně verifikována jednofázová metoda na určování délky vzduchového jádra hladinového víru. Na stejném příkladu byla verifikována i dvoufázová simulace v programu OpenFOAM a ANSYS Fluent. Výsledky obou řešičů a metod byly mezi sebou porovnány. Dosažené poznatky byly použity k návrhu experimentální nádrže s geometrii podobnou průmyslovým čerpacím jímkám. Byla vytvořena mapa výskytů hladinových vírů pro různé provozní body. Jeden provozní bod s výskytem vírů byl přepočítán jednofázovou a dvoufázovou metodou. Bylo dosaženo pouze částečné shody experimentu s numerickým modelem.
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Modelling of the Laminar/Turbulenttransition on a Heated Flat Plate Using the k-kL-w Model
Kožíšek, Martin ; Fürst, J. ; Příhoda, Jaromír
The contribution deals with the numerical simulation of the transition to turbulence on a heated flat plate by means of the k-kL-k-kL-w model of Walters and Cokljat (2008). The revised version of the three-equation model was implemented into the OpenFOAM code for the incompressible and compressible flows. Numerical simulations of the boundary-layer development were carried out according to measurements of Sohn and Reshotko (1991). The transition model was tested by means of the skin friction and the Stanton number distributions for various free-stream turbulence levels. Results were compared with empirical correlations expressing the Reynolds analogy according to Kays and Crawford (1993) and with experimental data of Pinson and Wang (2000).
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2-D externí aerodynamika tělesa nestandardního tvaru
Mohyla, Daniel ; Gal, Pavel (oponent) ; Dohnal, Miloslav (vedoucí práce)
Tato bakalářská práce se zaměřuje na analýzu jevu proudění kapaliny kolem válcové tyče v 2-D prostoru za využití metodiky výpočtové dynamiky tekutin (CFD) s populárními modely turbulence k- SST and k- SSTSAS. První část této práce je úvodem do problematiky o obtékání těles proudem kapaliny a uvedení pojmu CFD. V této části jsou popsané jevy jako odtržení mezní vrstvy od tělesa, modelování turbulence a popis různých modelů turbulence. Druhá část pojednává o nastavení výpočetní domény simulace uvnitř open source softwaru OpenFOAM a získaných výsledcích z domény. Poslední část se věnuje diskuzi o dosažených výsledcích a jsou porovnána s experimentem.
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Study of the Dissipation in Spiraling Vortical Structures
Štefan, David ; Drábková, Sylva (oponent) ; Koutník,, Jiří (oponent) ; Skoták, Aleš (oponent) ; Rudolf, Pavel (vedoucí práce)
This work deals with study of swirling flows where the spiral vortical structure appears. The main relation is to flow seen in the draft tube cone of hydraulic turbines operated out of the design point (i.e. best efficiency point). In this cases large coherent vortex structure (vortex rope) appears and consequently high pressure pulsations are propagated to the whole machine system leading to possible restriction of turbine operation. This flow features are consequence of flow instability called vortex breakdown in case of Francis turbine operated at part load (flow rate lower than optimal one). The present study is carried out using simplified device of swirl generator in order to access similar flow conditions as can be found in real hydraulic turbines. Both the dynamic and dissipation effect of spiral vortex breakdown are investigated. The first part of thesis deals with spiral form of vortex breakdown. The experimentally measured velocity profiles (LDA) and wall static pressures are correlated with numerical simulations carried out using open-source CFD package OpenFOAM 2.2.2. The high speed camera recording of cavitating vortex core is used to obtain image ensemble for further post-processing. The dissipation effect of spiral vortex structure is in detail discussed based on computed flow fields. The second part of thesis is dedicated to the application of POD decomposition to the study of spatio-temporal features of spiral vortex dynamics. Firstly the POD is applied to the both the experimentally obtained image ensemble of cavitating vortex and numerically computed static pressure fields. Secondly the comprehensive analysis of spiral vortex mitigation effect by the axial water jet is analyzed. The collaborative study employing the swirl generator apparatus designed by the researchers from Politehnica University of Timisoara in Romania is performed and changes in spatio-temporal vortex dynamic are studied. In this study the numerical data (in a form of three-dimensional pressure and velocity fields) are obtained using commercial CFD software ANSYS Fluent R14.
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