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Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 55
Yanovych, Vitalii , Duda, Daniel , Uruba, Václav , Procházka, Pavel , Antoš, Pavel
Effect of Cylinder Roughness on Strouhal Number

The main goal of this paper is to establish a better understanding of the relationship between a Strouhal number and surface roughness. Hot-wire anemometry was used to evaluations the characteristics of turbulent flow behind circular cylinders with different relative roughness 0% (smooth...

Duda, Daniel , Yanovych, Vitalii , Uruba, Václav
Simple Rheoscopic Flows Used in Teaching Fluid Mechanics

Four simple demonstration experiments are presented. They are used as a support in the teaching of Fluid Mechanics I (a compulsory lecture at the University of West Bohemia in Pilsen). All mentioned experiments use the rheoscopic fluid obtained as a water solution of mica powd...

Duda, Daniel , Abrhám, Vladimír , Uruba, Václav , Yanovych, Vitalii
Turbulent jet stability increased by ribs inside the nozzle – Stereo PIV measurement one diameter past the nozzle

We observe that decreasing the inner nozzle surface by adding longitudinal ribs increases the jet stability in terms of the amount of turbulent kinetic energy in the near shear layer. We try to explain our observation as a stabilization effect of secondary flow vortices emergi...

Yanovych, Vitalii , Duda, Daniel , Uruba, Václav , Kosiak, Pavlo
The structure of turbulent flow behind the NACA 0012 airfoil at high angles of attack and low Reynolds number

This paper shows the results of a study of the turbulent structure behind the NACA 0012 airfoil. During the experiment, the flow velocity was 20 m·s−1. That corresponds the Reynolds number 1.3·105. The point behind the trailing edge was chosen for experimental studies. Measurements...

Richter, Lukáš , Rendlová, Zdeňka , Plánička, Stanislav , Seeger, Jan , Taschek, Marco , Volf, Michal , Pelikán, Martin , Linhart, Vít
Experimental and numerical analysis of an oil-flooded air screw expander

This article describes the results of a project whose task is to research and develop a screw expander through the inversion of a screw compressor. The article summarizes aspects of the construction of an experimental device that works with an oil-flooded air screw expander. T...

Yanovych, Vitalii , Duda, Daniel
Using ARAMIS system for measurement of structural stability of running wind tunnel

Wind tunnels are popularly used to study various aerodynamic phenomena. Their design significantly influences the quality of the created airflow. During the flow generation, the construction parts of the wind tunnel to get deformed due to pressure variations. This phenomenon significantly co...

Duda, Daniel , Yanovych, Vitalii , Uruba, Václav , Němec, Martin , Žitek, Pavel
Vortices inside a single-stage axial air turbine captured by Particle Image Velocimetry

Particle Image Velocimetry (PIV) is an experimental method of fluid research resulting into a spatially resolved two-dimensional velocity field. We measured the velocity inside a single-stage axial test turbine at the Czech Aerospace Research Centre. We studied the axial × tangential plane&#...

Duda, Daniel , Jelínek, Tomáš , Němec, Martin , Uruba, Václav , Yanovych, Vitalii , Žitek, Pavel
Observation of flow structure past a full-stage axial air turbine at the nominal and off-design states

The air flow inside single-stage test turbine is studied experimentally by Particle Image Velocimetry (PIV). Here we report the measurements results at axial-tangential plane just behind the rotor wheel at middle blade radius. We studied one nominal state and two off-design states. We&#...

Duda, Daniel , Jelínek, Tomáš , Němec, Martin , Uruba, Václav , Yanovych, Vitalii , Žitek, Pavel
Particle image velocimetry measurement inside axial air test turbine - Effect of window

We measure the two dimensional instantaneous velocity fields inside an axial turbine by using the technique PIV (Particle Image Velocimetry). The measured plane is located just behind the rotor wheel and it is oriented in axial × tangential direction. We measured a single overloade...

Rubanenko, Olena , Miroshnyk, Oleksandr , Shevchenko, Sergiy , Yanovych, Vitalii , Danylchenko, Dmytro , Rubanenko, Oleksandr
Distribution of wind power generation dependently of meteorological factors

Analyses of trends increasing annual wind power plant capacity and power generation in the World and Europe are presented in this paper. Investigated main problems of increasing the power generation of renewable energy sources in distributed power grids. Proposed ways to decide them...

Volf, Michal , Demianenko, Maryna , Starynskyi, Oleksandr , Liaposhchenko, Oleksandr , Pavlenko, Ivan
Numerical Simulation of the Mass-Transfer Process Between Ammonia and Water in the Absorption Chiller

This paper describes the absorption process of gaseous ammonia into liquid water in the plate heat exchanger, which is considered to be the crucial part of an absorption cooling system. Two approaches are utilized to numerically simulate this absorption process. In the first approa...

Duda, Daniel , Yanovych, Vitalii , Uruba, Václav
Analysing mysterious turbulence

It is often said that turbulence is the last unsolved problem of classical physics \cite{Uriel}. This is caused by its enormous complexity resulting from the mutual interactions of large number of \emph{objects} of different sizes and strengths -- the \emph{vortices} and other...

Yanovych, Vitalii , Duda, Daniel , Horáček, Vít , Uruba, Václav
Research of a wind tunnel parameters by means of cross-section analysis of air flow profiles

Wind tunnel is constructed. It is characterized by a high degree of airflow laminarization. The main constructive element of this aerodynamic tube is the laminarization module. It allows the destruction of turbulent fluxes by providing a homogeneous laminar flow. In order to evaluate&#x...

Bém, Jindřich , Duda, Daniel , Kovařík, Jiří , Yanovych, Vitalii , Uruba, Václav
Visualization of secondary flow in a corner of a channel

We report observation of secondary flow in one corner of developing channel air flow. Length of the channel, i.e. length of boundary layer, is 400?mm, which is 3.2 times the channel cross-sectional size. Three components of velocity are measured by using a Stereo Particle Imag...

Richter, Lukáš , Uruba, Václav , Procházka, Pavel , Volf, Michal , Vacková, Michaela , Pavlíček, Petr , Krejčí, Miroslav
The Reynolds number effect on dynamics of the wake behind a circular cylinder

Circular cylinder in cross-flow was studied experimentally using time-resolved PIV technique. Reynolds numbers based on the cylinder diameter were in range from 3 850 up to 19 260. Effect of the Reynolds number on wake time-mean topology as well as the dynamical behavior is st...

Rubanenko, Olena , Yanovych, Vitalii , Miroshnyk, Oleksandr , Danylchenko, Dmytro
Hydroelectric power generation for compensation instability of non-guaranteed power plants

This paper presented research small- and minihydroelectric power plants as an effective source of compensation for instability of non-guaranteed renewable energy sources (RES) power plants. HPPs play the main role for balancing the power system operation mode. To somehow compensate for the&#...

Procházka, Pavel , Uruba, Václav
On the Recirculation Zone Behind a Cylinder of Finite Length with Subcritical Aspect Ratio

The Particle Image Velocimetry is utilized to investigate flow behind a cylinder of finite length with subcritical value of Aspect Ratio (AR). The cylinder is submitted to uniform freestream with very low intensity of turbulence and thin laminar boundary layer. The flow field canno...

Uruba, Václav
Reynolds Number in Laminar Flows and in Turbulence

Reynolds number is the basic parameter determining the flow-field topology and its evolution in time unambiguously if only inertial, pressure and viscous effects are involved. However the Reynolds number definition is not unique and its physical meaning depends strongly on its actual de...

Uruba, Václav , Procházka, Pavel , Skála, Vladislav
On the 3D dynamics of the wake behing a circular cylinder

Flow in the wake of a circular cylinder is studied experimentally using time-resolved stereo PIV method. Special attention is paid to 3D topology of dynamical structures. While the distribution of statistic quantities along the cylinder is uniform, and i.e. 2D, the instantaneous flow&#x...

Uruba, Václav , Procházka, Pavel
POD Spectrum of the Wake behind a Circular Cylinder

The wake dynamics behind a long circular cylinder in cross-flow was studied using the POD method. The temporal parts of POD modes, Chronoses, are subjected to frequency analysis. Five groups of modes are distinguished according to the frequency contents. The low order high energy&#...

Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 55