2024-11-26
10:48 |
Úplný záznam
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2024-11-26
10:48 |
Investigation of 3D flow structures in a linear blade cascade with stereo particle image velocimetry
Šnábl, Pavel ; Procházka, Pavel P. ; Uruba, Václav ; Pešek, Luděk
In most experiments and numerical calculations of flow through blade cascades, there is a tendency to reduce the problem to 2D. This is understandable due to the design of the experimental rigs and measurement methods, as well as the very long computation times of 3D numerical flow simulations. In reality, however, 3D flow structures such as streamwise vortices begin to appear in wakes behind profiles even for 2D geometry even at low Reynolds nubers. They can create force variations acting along the blade span, which can be represented on average by the 2D measurement and simulation and give a correct result, e.g. for the total lift and drag of the profile. However, when investigating dynamic aeroelastic instabilities such as flutter, local variations in aerodynamic forces can greatly influence the overall behaviour, e.g. by inducing stall flutter.
Úplný záznam
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2024-11-26
10:48 |
EXPERIMENTAL INVESTIGATION OF AEROACOUSTICS OF COMPLEX PROPELLER SYSTEM
Prasad, Chandra Shekhar ; Procházka, Pavel P. ; Skála, Vladislav ; Šnábl, Pavel
The reasearch deals with the experimental study of aeroacoustics noise generated by high-speed turboprop propellers and methods to minimize its causes. In the current project the study will focus mainly on the interaction of the propeller blade tip vortex and the wake with other propeller blades of multi blade and unconventional rotating propellers. The vortex flow visualization will be carried out using PIV and acoustics noise (far field and near field) will be measured two set different microphones by at different rotational speeds. Experimental results will be compared with high-fidelity numerical models. The influence of the propeller geometry and flow conditions on the aeroacoustics noise generation will be studied in detail.
Úplný záznam
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2024-11-26
10:48 |
EXPERIMENTAL BLADE CASCADE FOR AEROELASTIC STUDIES IN THE PRESENCE OF 3D FLOW STRUCTURES: INITIAL DESIGN IDEA
Šnábl, Pavel ; Prasad, Chandra Shekhar ; Pešek, Luděk ; Procházka, Pavel P.
In order to study the aeroelasticity in a blade cascade experimentally, simplifications must be made to make any measurements possible. Therefore, most researchers use linear cascades: parallel blades with constant cross-sections which essentially reduce the problem to 2D. Although linear cascades lack some key features such as rotational periodicity and the radial flow component, it is still possible to obtain and study aeroelastic couplings. The aim of the experimental cascade presented in this paper is to include the radial flow component by creating a bypass flow loop on the wind tunnel and having deformable blades fixed on one side only. When such blades oscillate, the channel width between the blades changes unevenly along the blade span. This experimental setup allows the effect of 3D flow in a blade cascade to be studied.\n
Úplný záznam
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2024-11-26
10:48 |
Stanovení dynamických charakteristik modelového turbínového kola a ověření parametrů měřicích, řidicích a bezpečnostních systémů zkušebního stroje laboratoře rotační laserové vibrometrie
Voronova, Evgeniya ; Procházka, Pavel ; Maturkanič, Dušan ; Mekhalfia, Mohammed Lamine ; Hodboď, Robert
Zpráva popisuje práce spojené s instalací nového modelu lopatkového kola turbíny v Laboratoři rotační laserové vibrometrie, které se od původního odlišuje tvarem lopatek s aerodynamickým profilem a volnými konci. Popis prací je uveden včetně modifikací zkušebního zařízení, které zahrnují dodání potřebných měřicích a ochranných prvků pro zvýšení kvality měření a pro bezpečnější provoz. Součástí instalace kola bylo také zprovoznění celého systému, měření pro ověření parametrů nového kola a stanovení provozních charakteristik a podmínek provozu, jaké mohou mít vliv na optimální využití zařízení při výzkumných experimentech. Zpráva rovněž obsahuje hodnocení výsledků měření se sledováním výskytu chyb a nejistot zaznamenávaných dat pro posuzování přesnosti u metody Blade Tip Timing.
Úplný záznam
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2024-09-22
00:06 |
Role of submembrane spaces in the control of transmembrane ion flux and cellular inotropic state in a model of human ventricular cardiomyocyte
Pásek, Michal ; Bébarová, M. ; Christé, G.
We have recently developed a model of a human ventricular cardiomyocyte incorporating the t-tubular and surface submembrane spaces and restricted ion exchange between these spaces and cytosol. After incorporating the experimental finding that the majority of Na+-Ca2+ exchanger proteins are located at the t-tubular membrane of human ventricular cardiomyocytes, we explored the consequences of ion concentration changes in the submembrane spaces on the electrophysiological activity of these cells. Consistently with published experimental and modelling studies, our model predicts an increased Ca2+ extrusion during the action potential. However, our model also predicts a significant reduction of Ca2+ extrusion throughout the diastole, which can ultimately lead to an increase in cellular inotropy.
Úplný záznam
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2024-05-12
00:02 |
Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna ; Bílek, V. ; Haidl, J. ; Isoz, Martin ; Pivokonský, M.
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and savings of operational costs. However, it is currently based on trial-and-error experimental approaches. In this contribution, we focus on flow modeling in stirred flocculation tanks that would, after coupling with a calibrated model of particle aggregation, enable simulationbased flocculation optimization. Despite the abundance of literature on stirred tank modeling, there is no universal agreement on the methodology used to describe turbulence nor on the approach to the computational mesh creation. Consequently, there is no unified methodology for simulations and their validation. To address this, we present a best-practice methodology for economical, yet reliable flow simulations in the said device. This methodology includes the choice of the turbulence model, the approach to the design of a high quality mesh suitable for arbitrary geometries, and results evaluation. It is developed based on an extensive literature review, a multitude of flow simulations using several meshes of progressively higher quality and resolution, and various strategies to converge to steady-state flow conditions. The simulation quality indicators used here involve comparison with the experimental data on fluid velocity, stirrer power output, and flow rate through the impeller zone. Additionally, the resulting flow simulation models are compared using tracer transport simulations, hinting at their potential for coupling with particle aggregation models.
Úplný záznam
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2024-04-15
12:40 |
Úplný záznam
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2024-04-15
12:40 |
Computational and experimental assessment of natural frequencies in a bladed disk system
Mekhalfia, Mohammed Lamine ; Procházka, Pavel ; Maturkanič, Dušan ; Voronova, Evgeniya ; Hodboď, Robert
This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring natural frequencies and mode shapes under different operational conditions. A comparative analysis is conducted to assess modal properties obtained from both analytical and experimental approaches, while also considering the influence of rotation speed. Additionally, Finite Element Method (FEM) outputs are used to accurately position the strain gauge. Integrating these techniques provides a comprehensive understanding of the bladed disk's behaviour under varying rotational speeds, enhancing result accuracy and facilitating thorough investigation within rotating machinery systems.
Úplný záznam
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2024-04-15
12:40 |
Úplný záznam
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