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National Repository of Grey Literature 3 records found  Search took 0.03 seconds. 
Aeroelastic instability of differently porous U-profiles in crosswind direction
 Hračov, Stanislav ; Macháček, Michael
Flow-induced vibrations of the flexibly mounted slender U-shaped beams allowed to oscillate in the crosswind direction only are studied experimentally in the wind tunnel. All beams are characterized by a cross section having a side ratio of along-wind to across-wind dimension equal to two. The effects of two depths of U profiles and two porosities of their flanges ( 0 % and 75 %) onto a loss of aeroelastic stability are investigated under the smooth flow conditions and for low Scruton numbers. The results indicate almost similar proneness of the non-porous beams to galloping-type oscillations to a rectangular prism with the same side ratio regardless their depth. The onset of across-wind galloping occurred in these cases at wind velocity very close to von-Kármán-vortex-resonance flow speed, even though the critical velocity predicted by the quasisteady theory is much lower. For porous and shallower U profile this asynchronous quenching also takes\nplace. However, the higher flange porosity reduces significantly not only the vortex-shedding effect, but also causes an increase in the onset galloping velocity above the critical speed determined for non-porous profiles. In the case of deeper U-shaped beam, the effect of higher porosity even suppresses the proneness to galloping
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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.
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Numerical analysis of aeroelastic behaviour ot the vocal folds
 Horáček, Jaromír ; Švec, J. G.
The study contributes to a more profound understanding of the mechanism of human voice production. The contribution is a continuation of recent studies of the authors where an original mathematical model for vibration of the vocal folds in the airflow coming from the human subglottal tract was developed. The model of the vocal fold was designed as a dynamic system with two degrees of freedom vibrating in the wall of a channel conveying air. Unsteady 1D flow theory for the inviscid incompressible fluid was used for the airflow. Here we present the results of the numerical solution which yields the vibration characteristics (eigenfrequencies, mode shapes of vibration and damping) of the aeroelastic system including the instability thresholds.
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