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The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode
Pešek, Luděk ; Šnábl, Pavel ; Bula, Vítězslav
The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss couplings vibrating at a higher resonant mode, i.e. mode with 6 nodal diameters (ND). The numerical solution of the wheel based on 3D finite element method with surface-to-surface dry friction contact model is applied. Due to dry friction contacts and non-linear solution, it leads to HPC computations and long computation times. Therefore, the earlier proposed computational strategy for damping evaluation where the resonant attenuation is computed directly from the defined resonant initial conditions given by the 6ND mode is used. Comparison of experimental and numerical results of dynamical behaviour of the bladed wheel yields a reasonable agreement for the studied vibration mode.
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Contribution to HPC FEM calculations of bladed disk dynamics with dry-friction contacts
Pešek, Luděk ; Šnábl, Pavel ; Bula, Vítězslav
The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tie-bosses based on 3D finite element method with surface to surface dry-friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behaviour and damping estimation of our bladed wheel design yielded a reasonable agreement. Due to dry-friction contacts and non-linear solution of 3D FE model it, however, leads to HPC computations and long computation times. The contribution deals with description of computational strategy for damping evaluation and achieved results, too.
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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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Development and validation of the new model of thermal conditions of urban environment in fine resolution
Resler, Jaroslav ; Krč, Pavel ; Belda, Michal ; Juruš, Pavel ; Benešová, N. ; Lopata, J. ; Vlček, O. ; Damašková, D. ; Eben, Kryštof ; Derbek, P. ; Maronga, P. ; Kanani-Sühring, F.
The assessment of different scenarios of the city development to air quality and thermal comfort in the areas of street canyons was our main goal inside the project UrbanAdapt. It follows the need for a model which allows to simulate air flows in fine resolution of the order of meter and realistically predict turbulence in the complex terrain of streets and buildings. The LES models comply with such requirements but the review showed that there was no free available LES model which could model the energy exchange in urban environment, i.e. the interaction of energy and air flows including effects of vegetation and different properties of urban surfaces and materials. Thus we decided to extend the existing LES model PALM by a new module USM (Urban Surface Model) which describes the most important energy exchanges in the urban environment. The validation of the model was done against observations obtained by IR camera in the course of heat wave episode in July 2015.
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