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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.
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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.
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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.
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