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Stochastic resonance of cylinder induced wind flow
Pospíšil, Stanislav; Kuznetsov, Sergeii; Trush, Arsenii; Král, Radomil
2013 - English
The response of a dynamic nonlinear single degree of freedom system to combination of addtive random Gaussian white noise and external deterministic periodic force applied to the aerodynamic phenomena is studied. It is coming to light that under certain circumstances the jumping between wells of the bistable elastic potential can occur leading to internal hopping. The frequency of this hopping can be for certain combination of input parameters nearly the constant and corresponding to external periodic force frequency. This state leads to high ratio of periodic component amplitude and intensity of the random component of the response proces. As the object was chosen in tubulent flow.
Keywords:
stochastic resonance; aerodynamic phenomena; cylinder in turbulent flow
Available at various institutes of the ASCR
Stochastic resonance of cylinder induced wind flow
The response of a dynamic nonlinear single degree of freedom system to combination of addtive random Gaussian white noise and external deterministic periodic force applied to the aerodynamic phenomena ...
Stability of a U-shaped profile and combination of wind flow velocity 0-18 m/s
Král, Radomil; Kuznetsov, Sergeii; Pospíšil, Stanislav; Buljac, Andrija
2013 - English
The report presents experimental results regarding the aero-elastic stability of a U-shaped profile withan aspect-ratio (along wind length B, frontal height H) of B/H = 4.65. In the literature it can be found that a square prism (B/H =1) can perform galloping oscillations. However, this is not the case for a flat rectangular prism (B/H = 10). The aspect ratio of the U-beam under consideration here lies between these two values. Additionally, the asymetry of the profile possibly introduces interesting effects. In a comprehensive study of B/H = 4 rectangulsr prism, it is shown experimentally that vortex-induced as well as self-excited one-degree of freedom vibrations are possible. Our investigation aims at understanding the excitation mechanism and estimate critical velocities. Simulations and, more recently wind tunnel experiments are used in our investigations.
Keywords:
wind tunnel; aero-elastic stability; U-shaped profile
Available at various institutes of the ASCR
Stability of a U-shaped profile and combination of wind flow velocity 0-18 m/s
The report presents experimental results regarding the aero-elastic stability of a U-shaped profile withan aspect-ratio (along wind length B, frontal height H) of B/H = 4.65. In the literature it can ...
The stability of the cable supported bridge deck during wind and traffic
Král, Radomil; Buljac, Andrija; Pospíšil, Stanislav; Kuznetsov, Sergeii
2013 - English
With nowadays trends of elongation of span length in bridge structures, they are becoming more and more sensitive to wind loads, therefore analysis of their aero elastic stability is of great concern. These structures have low eigen frequencies and low damping, which makes them highly susceptible to actions of the wind. Studies of flow-induced vibrations, which are excited by complex interaction between airflow and moving bridge girder, are of great importance for estimation of dynamic response of bridge structures.
Keywords:
cable supported bridge; aeroelasticity; wind effects
Available at various institutes of the ASCR
The stability of the cable supported bridge deck during wind and traffic
With nowadays trends of elongation of span length in bridge structures, they are becoming more and more sensitive to wind loads, therefore analysis of their aero elastic stability is of great concern. ...
Wind pressures on envelope surfaces of the building Waste to Energy Plant - LEEDS
Pospíšil, Stanislav; Kuznetsov, Sergeii; Král, Radomil; Plut, Mihael
2013 - English
The aim is the determination of wind-induced pressures required for the design of components of envelope of the object using methods of a physical scale modeling in the Climatic wind Engineering Laboratory of the Centre of Excellence Telč for project of the building Waste to Energy Plant - Leeds.
Keywords:
boundary layer flow; experimental investigation; wind pressure
Available at various institutes of the ASCR
Wind pressures on envelope surfaces of the building Waste to Energy Plant - LEEDS
The aim is the determination of wind-induced pressures required for the design of components of envelope of the object using methods of a physical scale modeling in the Climatic wind Engineering ...
Transient heat transfer coefficient on precooled circular cylinder at various reynolds numbers
Král, Radomil; Beran, Pavel; Kuznetsov, Sergeii
2013 - English
In this work, the experimental investigation of unsteady averaged heat transport coefficient is carried out. Using precooled concrete circular cylinder being immersed into the air cross-flow at constant temperature level, the heat convection for various wind speed ranging from 5 to 15 m/s is determined. The attention is also given to the temperature distribution over the circular cross-section with respect the time evolution. Instantaneous energy lost is evaluated in average together with its distribution over the cylinder. The heat transfer effect expressed by the non-dimensional Nusselt numvber is identified and graphically interpreted.
Keywords:
heat transfer; wind tunnel; Reynolds number
Available at various institutes of the ASCR
Transient heat transfer coefficient on precooled circular cylinder at various reynolds numbers
In this work, the experimental investigation of unsteady averaged heat transport coefficient is carried out. Using precooled concrete circular cylinder being immersed into the air cross-flow at ...
The simulation of an ice formation and rain drops on surface cables of cable supported bridges and stability measurements of dynamic response
Pospíšil, Stanislav; Kuznetsov, Sergeii; Marušić, Ante; Tatara, Marcin
2013 - English
This project is the first part of larger project which aims to analyse aerodynamic characteristic of cable-stayed bridges in certain climatic conditions when ice accretion on cables occur. Covering the whole process from rain simulation to extraction of aerodynamic characteristic, this is the first project ever conducted in climatic section of wind tunnel at Center of Exelence Telč.
Keywords:
aerodynamic characteristic; cable supported bridges; climatic tunnel
Available at various institutes of the ASCR
The simulation of an ice formation and rain drops on surface cables of cable supported bridges and stability measurements of dynamic response
This project is the first part of larger project which aims to analyse aerodynamic characteristic of cable-stayed bridges in certain climatic conditions when ice accretion on cables occur. Covering ...
Methods of measurement and control of the wind tunnel boundary layer with turbulence generators
Kuznetsov, Sergeii; Plut, Mihael
2013 - English
As with every new wind tunnel, the first step is the detailed mapping of turbulent flow characteristic. In the next step, commonly the characteristic of the boundary layer simulation are being investigated prior to proceeding with test on engineering structures, air pollution dispersion, wind energy and urban micrometeorology. This type of wind tunnel has been commonly used in the field of wind engineering. The work was carried out within the CET Start-up pilot project.
Keywords:
atmospheric boundary layer; turbulent flow characteristic; wind tunnel
Available at various institutes of the ASCR
Methods of measurement and control of the wind tunnel boundary layer with turbulence generators
As with every new wind tunnel, the first step is the detailed mapping of turbulent flow characteristic. In the next step, commonly the characteristic of the boundary layer simulation are being ...
Visualization methods of flow in the climatic wind tunnel
Kuznetsov, Sergeii; Trush, Arsenii; Král, Radomil; Pospíšil, Stanislav
2013 - English
Visualization of wind tunnel flow around the test model - one of the most informative and demonstrative techniques used in the study of aerodynamics models. Most fluids, gaseous or liquid, are transparent media, and their motion remains invisible to the human eye during direct observation. The visualisation of complex flows has been played a unique role in the improvement of understanding of fluid dynamic phenomena. Flow visualization has been used to verify existing physical principles and has to led the discovery of numerous flow phenomena. In addition to obtaining qualitative global pictures of the flow, the possibility of acquring quantitative measurements without introducing probes, which invariably disturb the flow. A great variety of such methods is known that enable one to make fluid flows visible.
Keywords:
wind tunnel; wind flow; visualization methods
Available at various institutes of the ASCR
Visualization methods of flow in the climatic wind tunnel
Visualization of wind tunnel flow around the test model - one of the most informative and demonstrative techniques used in the study of aerodynamics models. Most fluids, gaseous or liquid, are ...
Mineralogical, chemical-physical characterization of mineral fibers and their interaction with the human body
Viani, Alberto; Pérez-Estébanez, Marta; Mácová, Petra
2013 - English
A standardized protocol of analysis of the mineral fibers with a preliminary full mineralogical characterization has never been applied so far. There are thousands of contributions in the literature on specific aspects of the problem but very few attempts to draw a general picture based on a multidisciplinary approach. To the eye of the proposers of the project, this seems to be the only way to reach a conclusive and shared general view at a molecular level of the bio-toxicity of mineral fibers at a structural level. In this first stage of a more vast project, the study of mineral fibers has been conducted using different experimental approaches. Eight samples of mineral fibers have been selected for their economic and social importance with the objective to systematically characterize their structural, physical-chemical characteristics and attain a direct comparison. X-rays diffraction data, micro-Raman and micro-Infrared spectra of some of them were collected at CET.
Keywords:
mineral fibers; chrysotile asbestos; materials analysis
Available at various institutes of the ASCR
Mineralogical, chemical-physical characterization of mineral fibers and their interaction with the human body
A standardized protocol of analysis of the mineral fibers with a preliminary full mineralogical characterization has never been applied so far. There are thousands of contributions in the literature ...
Testing of CaLoSiL treatment effects on historic rendering at Rosa Coeli Monastery in Dolní Kounice
Bryscejn, Jan; Drdácký, Miloš; Valach, Jaroslav; Zíma, Pavel
2010 - English
The report describes testing of impregnation effects of various consolidants on historic plasters. Peeling test, resistance micro-drilling and micro-tube gage for water uptake were applied. The agents and their application modes were assessed and ranked according to the measured effects.
Keywords:
historic render; consolidation; CaLoSiL
Available at various institutes of the ASCR
Testing of CaLoSiL treatment effects on historic rendering at Rosa Coeli Monastery in Dolní Kounice
The report describes testing of impregnation effects of various consolidants on historic plasters. Peeling test, resistance micro-drilling and micro-tube gage for water uptake were applied. The agents ...
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