Národní úložiště šedé literatury Nalezeno 10 záznamů.  Hledání trvalo 0.00 vteřin. 
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.
Impact of Turbulence Generators on Turbulent Characteristics and Structures
Kellnerová, Radka ; Jurčáková, Klára ; Jaňour, Zbyněk
The turbulent generators are routinely used to produce very turbulent flows. Special type of vertically slenderize spires are applied to enhance turbulent diffusion from the surface upwards in order to increase the boundary layer depth. This paper studies the influence of variable upstream distance of generators on formation of both vortical and non-vortical organized structures within a test section. The 2-component 2-dimensional time-resolved particle image velocimetry measurement of the flow was performed in the wind channel with very rough surface. Intermittent flow dynamics was evaluated by means of higher order moments, vorticity, quadrant and wavelet analysis. The downstream evolution of the flow suggests that equilibrium between roughness- and spires-produced turbulence was reached at the distance of 7 spires height.\n
Simulation of Transonic Flow Through a Mid-Span Turbine Blade Cascade with the Separation-Induced Transition
Straka, P. ; Příhoda, Jaromír ; Fenderl, D.
The paper deals with the numerical simulation of the transonic flow through a mid-span turbine blade cascade by means of an in-house code based on the EARSM turbulence model of Hellsten [1] completed by the algebraic transition model of Straka and Příhoda [2]. The simulation using the transition model of Langtry and Menter [3] and Menter et al. [4] implemented in the commercial code ANSYS Fluent was used for the comparison. Simulations were carried out for the transonic regime close to the nominal regime. The flow separation on the suction side of the blade is caused by the interaction of the reflected shock wave with the boundary layer. The attention was focused on the modelling of the transition in the separated flow especially on the modelling of the length of the transition region. Numerical results were compared with experimental results.
Transition Modelling on Separated Flow in Turbine Cascade
Louda, Petr ; Příhoda, Jaromír ; Kozel, K.
The work deals with numerical simulation of turbulent ow through turbine cascade by RANS model with model of transition to turbulence. Performance of two transition models is compared. First one is gamma-zeta model based on transition criteria, second one algebraic transition model based on the concept of laminar uctuations energy (Kubacki, Dick 2016). The criterion for transition in separated state is re-formulated in order to remove stream-wise non-local formulation. The performance of the transition models is observed on the shock wave - boundary layer interaction on turbine blade.
Numerical Simulation of Laminar-Turbulent Transition in Accelerated Flows
Fürst, J. ; Příhoda, Jaromír
The article deals with the evaluation of two RANS based models for simulation of transitional flows including heat transfer. The work is focused on the transition and heat transfer in cases of accelerated flows over a flat plate and through a test turbine cascade.
Topical Problems of Fluid Mechanics 2017
Šimurda, David ; Bodnár, T.
The aim of the conference is to publish and to discuss the latest results of research in fluid mechanics.
Incompressible and compressible viscous flow with low Mach numbers
Balázsová, M. ; Feistauer, M. ; Sváček, Petr ; Horáček, Jaromír
In this paper we compare incompressible flow and low Mach number compressible viscous flow. Incompressible Navier-Stokes equations were treated with the aid of discontinuous Galerkin method in space and backward difference method in time. We present numerical results for a flow in a channel which represents a simplified model of the human vocal tract. Presented numerical results give a good correspondence between the incompressible flow and the compressible flow with low Mach numbers.
On the boundary conditions in the numerical simulation of stably stratified fluids flows
Bodnár, Tomáš ; Fraunié, P.
This paper presents the results of a numerical study of the stably stratified flow over a low smooth hill. The emphasize is on certain problems related to artificial boundary conditions used in the numerical simulations. The numerical results of three-dimensional simulations are shown for a range of Froude and Reynolds numbers in order to demonstrate the varying importance of these boundary issues in different flow regimes. The simulations were performed using the Boussinesq approximation model solved by a high-resolution numerical code. The in-house developed code is based on compact finite-difference discretization in space and Strong Stability Preserving Runge-Kutta time integration.
Note on the use of Camassa-Holm equations for simulation of incompressible fluid turbulence
Caggio, Matteo ; Bodnár, Tomáš
The aim of this short communication is to briefly introduce the Camassa-Holm equations as a working model for simulation of incompressible fluid turbulence. In particular we discuss its application for turbulent boundary layer flows. This model (and related models) is studied for several years in mathematical community, starting from Leray [23]. It can be understood as a generalization of some classical fluid models (Navier-Stokes equations, Prandtl boundary layer equations), showing some interesting mathematical properties in the analysis of the behavior of it's solution (e.g. Layton and Lewandowski [22]). It has been found however, that the model predictions can lead to surprising extensions of the use of the model in technical applications, namely in simulating the turbulent fluid flows. This brief paper should be understood as an introductory note to this novel class of models for applied scientists.
Note on the problem of dissipative measure-valued solutions to the compressible non-Newtonian system
Al Baba, Hind ; Caggio, Matteo ; Ducomet, B. ; Nečasová, Šárka
We introduce a dissipative measure-valued solution to the compressible non-Newtonian system. We generalized a result given by Novotný, Nečasová [14]. We derive a relative entropy inequality for measure-valued solution as an extension of the classical entropy inequality introduced by Dafermos [2], Mellet-Vasseur [11], Feireisl-Jin-Novotný [5].

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