Ústav termomechaniky

Nejnovější přírůstky:
2019-02-13
17:43
Model order reduction technique for large scale flow computations
Isoz, Martin
Current progress in numerical methods and available computational power combined with industrial needs promote the 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 application of MOR to the problems originating in the finite volume (FV) discretization of incompressible Navier-Stokes equations. Our approach to MOR is based on the proper orthogonal decomposition (POD)\nwith Galerkin projection. Moreover, the problems arising from the nonlinearities present in the original model are adressed within the framework of the discrete empirical interpolation method (DEIM). We provide a link between the POD-DEIM based MOR and OpenFOAM, which is an open-source CFD toolbox capable of solving even industrial scale problems. 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.

Úplný záznam
2019-02-13
17:43
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.

Úplný záznam
2019-02-13
17:43
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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2019-02-13
17:43
Measurements on KR-D-1 Blade Cascade
Šimurda, David ; Luxa, Martin ; Radnic, Tomáš ; Hála, Jindřich
This report contains results and evaluation of aerodynamic measurements conducted on a transonic compressor blade cascade.

Úplný záznam
2019-02-13
17:43
Comparison of Finite Volume and Spectral/HP Methods on Navier - Stokes Equations for Unsteady Incompressible Flow
Pech, Jan ; Louda, Petr
We provide a comparison of solutions to the incompressible Navier-Stokes equations obtained using codes based on finite volume and spectral element methods. Convergence properties are compared on test case with analytical solution. The dependence of Strouhal and Reynolds numbers for flow over a cylinder is reconstructed for both methods.\n\n

Úplný záznam
2019-02-13
17:43
Flow in Branched Channel
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
Flow in a branched channel is investigated experimentally using the PIV method. The branches are issuing from the main cannel perpendicularly, all channels are of rectangular cross-section. The time-mean flow-fields in the main channel and in the branches are studied in details.

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2019-02-13
17:43
Měření na profilu NACA 0010-64
Luxa, Martin ; Hála, Jindřich
Zpráva se zabývá měřením transsonického proudění na symetrickém profilu s různou drsností jeho náběžné části. Při měření bylo využito pro zjišťování polohy přechodu mezní vrstvy metody interferometrické a též metody měření smykového tření žhaveným filmem.

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2019-02-13
17:43
Proceedings of Topical Problems of Fluid Mechanics 2018
Šimurda, David ; Bodnár, T.
The aim of the conference is to publish and to discuss the latest results of research in fluid mechanics.

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2019-02-13
17:43
Proceedings "XXIV Biennial Symposium on Measuring Techniques in Turbomachinery"
Šimurda, David
Aim of the symposium is to bring together researchers from the field of experimental research in turbomachines who can share and are interested in experience with the development of new experimental measurement techniques, new techniques for monitoring engine operation and performance, and application of new analysis techniques to experimental data.

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2019-02-13
17:43
Investigation of Vstol Aircraft Engine Surge Due to Ground Vortex Ingestion
Lepičovský, Jan ; duPont, A. A.
An investigation of flow instabilities in the inlet ducts of a two-engine vertical takeoff and landing aircraft DP-1C is described in this paper. The engines stalled during run ups while the aircraft was perated on the ground. These pop stalls occurred at relatively low power levels, sometimes as low as 60% of the engine full speed. The main focus of the paper is on instrumentation of the aircraft intake ducts and on high speed recording the flow instabilities during the engine rotating stall and surge events. The recorded data sets show the history of speeds of both engines and the associated history of pressure changes recorded by six pressure transducers installed in both inlet ducts. Analysis of recorded unsteady pressure data indicated that engine stalls were evoked by a sudden ingestion of a vortex generated between the two streams moving in the opposite directions: hot gas flow close to the ground streaming outbound from the main nozzle and inbound flow above in the engine inlets. The engine stall problem was eventually resolved by modifying the overall flow pattern at the engine intake lips by deploying a suitably shaped double scoop flow deflector.

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