National Repository of Grey Literature 21 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Investigation of aeroelastic bridge instabilities using the multidimensional Fokker-Planck equation and wind-tunnel experiment
Král, Radomil
Stability of bridges and other line-like engineering structures is an important part of their overall design. It is also still of great interest nowadays due to a higher demand on increasing the span while maintaining an economical cost and service. During the previous decades sophisticated methods for the aeroelastic instability prediction have evolved and successfully applied to the real structures and many questions have been adequately answered.
Comparison of flutter derivatives for Kao Pin Hsi Bridge and flat plate
Buljac, A. ; Pospíšil, Stanislav ; Kozmar, H. ; Kuznetsov, Sergeii ; Král, Radomil
Focus of this work is put on evaluation of dimensionless aeroelastic coefficients, i.e. flutter derivatives, which are considered to be indicators of the aeroelastic stability of bridges. A comprehensive experimental study on dynamic wind-induced behavior of the Kao-Pin-Hsi bridge in Taiwan is described. The results are compared to those of the thin flat plate with high width to height ratio, which previously proved to be aeroelastically stable.
Solution of the multi-dimensional Fokker-Planck by means of finite element method
Náprstek, Jiří ; Král, Radomil
As a demonstrative example, the two-degree-of-freedom system is investigated. A combination of Rayleigh\nor Van der Pol with Duffing types of differential equations are assumed characterized by the\nnonlinear behavior both in the stiffness and damping. This system is subjected to the additive and\nthe multiplicative Gaussian white noise which represents a part of non-linear aero-elastic effects in\nthe system.
Finite element solution of the nonlinear 2DOFs dynamic system under random Gaussian excitation using the Fokker-Planck equation
Král, Radomil ; Náprstek, Jiří
Papers published until now are dealing with single degree of freedom (SDOF) systems. So the respective FP equation includes two independent space variables only (x1, x2). Nevertheless stepping over this limit and entering into a true multi-dimensionality a number of specific problems must be overcome. While in usual FEM practice the number of space variables is two or three, investigating FP equation, so 2n independent space variables emerges. It means for instance 12 space variables when random motion of a rigid body in space with six degrees of freedom is studied. Many requirements should be respected which are out of a conventional practice of Finite Element employment.
The stability of the cable supported bridge deck during wind and traffic
Král, Radomil ; Buljac, Andrija ; Pospíšil, Stanislav ; Kuznetsov, Sergeii
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.
Transient heat transfer coefficient on precooled circular cylinder at various reynolds numbers
Král, Radomil ; Beran, Pavel ; Kuznetsov, Sergeii
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.
Stability of a U-shaped profile and combination of wind flow velocity 0-18 m/s
Král, Radomil ; Kuznetsov, Sergeii ; Pospíšil, Stanislav ; Buljac, Andrija
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.
Visualization methods of flow in the climatic wind tunnel
Kuznetsov, Sergeii ; Trush, Arsenii ; Král, Radomil ; Pospíšil, Stanislav
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.
Wind pressures on envelope surfaces of the building Waste to Energy Plant - LEEDS
Pospíšil, Stanislav ; Kuznetsov, Sergeii ; Král, Radomil ; Plut, Mihael
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.
Stochastic resonance of cylinder induced wind flow
Pospíšil, Stanislav ; Kuznetsov, Sergeii ; Trush, Arsenii ; Král, Radomil
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.

National Repository of Grey Literature : 21 records found   1 - 10nextend  jump to record:
See also: similar author names
1 KRÁL, Radan
2 KRÁL, Radim
2 Král, Radek
3 Král, Richard
3 Král, Robert
1 Král, Robin
3 Král, Roman
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