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Study of Turbulence and Torsional Amplitude Effect on Aerodynamic Forces of Rectangular Prism

Author: HuHaiBo
Tutor: ZhangZhiTian
School: Hunan University
Course: Bridge and Tunnel Engineering
Keywords: Turbulence Amplitude Pressure Aerodynamic Self-excited forces Cross correlation Flutter Derivatives
CLC: U441.3
Type: Master's thesis
Year: 2010
Downloads: 75
Quote: 0
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Abstract


At present, the international assessment of the performance of the span bridges pneumatic stable mainly based Scanlan Professor establish the linear self-excited forces theoretical model and the corresponding test identification method, the theories and methods did not consider the impact of the turbulence structure aerodynamic performance amplitude dependent. In view of this, the paper focuses on the turbulent and amplitude of the bluff body cross-section of the unsteady aerodynamic launched a pilot study of the impact of self-excited forces. Based on the results of wind tunnel tests on several flow field in still and vibration model aerodynamic spanwise correlation. Manometry study the turbulent flow field model surface dynamic pressure distribution to more microscopic understanding of the impact of the turbulence of the self-excited forces forced vibration model. The impact of the turbulence on the aerodynamic performance of the bridge is not entirely related to the performance of self-excited forces, as well as the total aerodynamic force along the span direction. With the turbulence increases, whether it is stationary or vibration model, the pressure peak region is moved in the upstream direction. The turbulence caused by the phenomenon of changes in the distribution of pneumatic pressure change caused by the structure of the overall stability characteristics. As the wind speed increases, whether stationary or vibration model, the gas dynamic spatial correlation improved. This fully shows that the elongated structure stochastic theory of wind-induced vibration analysis model assumes buffeting force spatial correlation of wind speed increased unchanged this assumption is not established. Therefore, the theoretical model will span bridge buffeting, can consider the spatial correlation of wind speed buffeting force change this feature, create fine the buffeting theory model and eliminate interference recognize aerodynamic admittance factors have important significance. Sectional results show that the self-excited force, the presence of turbulence reduces the self-excited forces spatial correlation. From the unsteady aerodynamic pressure distribution and flutter derivatives starting with the two aspects of amplitude changes, the use of forced vibration test device to study the impact of the change of amplitude bluff body of rectangular cross-section aerodynamic performance. Aerodynamic cross-section of the structure is evolving with the amplitude variations. Aspect is relatively small rectangular cross-section, the changes in amplitude of flutter derivatives H3 * value great influence H2 *, A3 *; major flutter derivatives of A2 * values ??increase with increasing amplitude , its aerodynamic damping decreases with increasing amplitude, performance disaster nonlinear. The for Aspect relatively large rectangular cross section, with the increase of the amplitude of the main flutter guide number A2 * value is reduced, the performance of its aerodynamic damping increases with increasing amplitude, the performance of good state nonlinear. And the as commuted wind speed increases, the amplitude of the influence of the relatively large rectangular cross section of aspect is more obvious. This fully shows that the amplitude changes in the aerodynamic performance of the structure itself can not be ignored.

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CLC: > Transportation > Road transport > Bridges and Culverts > Structural principles, structural mechanics > Bridge vibration and damping device
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