Number of found documents: 13
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Impact of Turbulence Generators on Turbulent Characteristics and Structures
Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
2017 - English
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 Keywords: turbulence generator; wind channel; vorticity; quadrant analysis Fulltext is available at external website.
Impact of Turbulence Generators on Turbulent Characteristics and Structures

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 ...

Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
Ústav termomechaniky, 2017

CFD motivated applications of model order reduction
Isoz, Martin
2017 - English
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. Keywords: model order reduction; CFD; OpenFOAM Fulltext is available at external website.
CFD motivated applications of model order reduction

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 ...

Isoz, Martin
Ústav termomechaniky, 2017

Numerical Simulation of Laminar-Turbulent Transition in Accelerated Flows
Fürst, J.; Příhoda, Jaromír
2017 - English
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. Keywords: turbulence; laminar-turbulent transition; finite volume method Fulltext is available at external website.
Numerical Simulation of Laminar-Turbulent Transition in Accelerated Flows

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 ...

Fürst, J.; Příhoda, Jaromír
Ústav termomechaniky, 2017

Simulation of Transonic Flow Through a Mid-Span Turbine Blade Cascade with the Separation-Induced Transition
Straka, P.; Příhoda, Jaromír; Fenderl, D.
2017 - English
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. Keywords: mid-section blade cascade; boundary layer transition; shock wave interaction Fulltext is available at external website.
Simulation of Transonic Flow Through a Mid-Span Turbine Blade Cascade with the Separation-Induced Transition

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 ...

Straka, P.; Příhoda, Jaromír; Fenderl, D.
Ústav termomechaniky, 2017

Transition Modelling on Separated Flow in Turbine Cascade
Louda, Petr; Příhoda, Jaromír; Kozel, K.
2017 - English
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. Keywords: turbine cascade; transition model; separation bubble; shock wave-boundary layer interaction Fulltext is available at external website.
Transition Modelling on Separated Flow in Turbine Cascade

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 ...

Louda, Petr; Příhoda, Jaromír; Kozel, K.
Ústav termomechaniky, 2017

Force interaction of an airfoil in fluid flow
Uruba, Václav
2016 - English
The physical mechanism of lift and drag forces exerted on an airfoil is studied using results from mathematical modelling. Special attention is paid to lift force origin. The mechanism based on 3D flow-structure as a result of 2D flow-field instability is described. Keywords: airfoil; lift; stability; 3D flow; streamwise vortices Fulltext is available at external website.
Force interaction of an airfoil in fluid flow

The physical mechanism of lift and drag forces exerted on an airfoil is studied using results from mathematical modelling. Special attention is paid to lift force origin. The mechanism based on 3D ...

Uruba, Václav
Ústav termomechaniky, 2016

Možnosti zvýšení efektivity profilů lopatek
Uruba, Václav
2016 - Czech
Bude představen fyzikální mechanismus vzniku silových účinků na lopatkové profily při\nobtékání. Dále bude naznačena cesta pro ovlivnění relevantních parametrů těchto profilů,\nzejména velikosti vztlakové a odporové síly a tlakových ztrát. The physical mechanism of force origin exerting on blades in flow is to be explained. The\nway for modification of blades flow parameters will be indicated, special attention will be\npaid to drag and lift forces as well as to pressure loses. Keywords: profile blades; buoyancy; stability Fulltext is available at external website.
Možnosti zvýšení efektivity profilů lopatek

Bude představen fyzikální mechanismus vzniku silových účinků na lopatkové profily při\nobtékání. Dále bude naznačena cesta pro ovlivnění relevantních parametrů těchto profilů,\nzejména velikosti ...

Uruba, Václav
Ústav termomechaniky, 2016

Vortex structures generated by dbd plasma actuator
Procházka, Pavel P.
2013 - English
This article deals with the research of vortex structures generated by a plasma actuator. Plasma actuators belong to devices that can be used for active flow control. Plasma actuator flow control has been in the center of interest for the last two decades. However, one can find only a limited amount of information dealing with the physical principal of this phenomenon. The conclusion of this article is formulated to give an explanation of physical laws acting during generating, evaluating and decay vortex structures in a complex way to ensure that results could be apply in the future for more applicable research. Keywords: plasma; actuation; DBD; vortex; plazma; kontrola Fulltext is available at external website.
Vortex structures generated by dbd plasma actuator

This article deals with the research of vortex structures generated by a plasma actuator. Plasma actuators belong to devices that can be used for active flow control. Plasma actuator flow control has ...

Procházka, Pavel P.
Ústav termomechaniky, 2013

On the Reynolds number role in structure of recirculation zone b ehind backward facing step in a narow channel
Uruba, Václav
2013 - English
Topology of the time-mean flow-field behind the backward facing step in a narrow channel is presented for various Reynolds numbers. The flow-field is studied in planes close to the channel bottom and in the plane of symmetry. Special attention is devoted to the appearance of secondary and higher order structures defined on the time-mean basis. Experimental results are obtained from PIV measurements. Keywords: channel flow; backward facing step; Reynolds number; recirculation; Reynoldsovo číslo; čas Fulltext is available at external website.
On the Reynolds number role in structure of recirculation zone b ehind backward facing step in a narow channel

Topology of the time-mean flow-field behind the backward facing step in a narrow channel is presented for various Reynolds numbers. The flow-field is studied in planes close to the channel bottom and ...

Uruba, Václav
Ústav termomechaniky, 2013

On mathematical modelling of gust response using the finite element method
Sváček, P.; Horáček, Jaromír
2013 - English
In this paper the numerical approximation of aeroelastic response to sudden gust is presented. The fully coupled formulation of two dimensional incompressible viscous fluid flow over a flexibly supported structure is used. The flow is modelled with the system of Navier-Stokes equations written in Arbitrary Lagrangian-Eulerian form and coupled with system of ordinary differential equations describing the airfoil vibrations with two degrees of freedom. The Navier-Stokes equations are spatially discretized by the fully stabilized finite element method. The numerical results are shown. Keywords: aeroelasticity; Navier-Stokes equations for incompressible flow; airfoil section Fulltext is available at external website.
On mathematical modelling of gust response using the finite element method

In this paper the numerical approximation of aeroelastic response to sudden gust is presented. The fully coupled formulation of two dimensional incompressible viscous fluid flow over a flexibly ...

Sváček, P.; Horáček, Jaromír
Ústav termomechaniky, 2013

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