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Modelling nonlinear aerodynamic damping during transverse aerodynamic instabilities for slender rectangular prisms with typical side ratios
Abstract The transverse aerodynamic instabilities of rectangular cylinders with three typical side ratios (width-to-depth-ratio as 2:1, 1:1 and 1:2) were investigated through a series of elastically-supported sectional model tests. Experimental results indicate that side ratio plays an important role in the phenomena of transverse instabilities and a larger side ratio B/D generally corresponds to a stronger interaction of VIV and galloping. For side ratio B/D = 2, all test cases exhibited unsteady galloping starting from the Kármán vortex resonance wind speed. When Scruton number is larger than a threshold value between 12.1–19.4, the unsteady galloping of B/D = 1 shows a separate behavior of VIV and galloping with a twofold-amplitude phenomenon. Whereas, side ratio B/D = 0.5 exhibited a pure transverse VIV. The feasibility of classical quasi-steady theory was found not able to predict the onset wind speeds and stable amplitudes. An empirical model was established to consider the aerodynamic nonlinearity by two amplitude-dependent damping terms and aerodynamic unsteadiness by expressing aerodynamic parameters as functions of reduced frequency. The empirical model was validated, having a satisfactory accuracy in predicting the vibration amplitudes of unsteady galloping and VIV. The proposed model represents a promising tool in engineering applications where the interference of VIV and galloping is concerned.
Highlights Transverse aerodynamic instabilities of rectangular cylinders with typical side ratios were investigated. A novel empirical model was proposed for unsteady galloping and VIV. The nonlinear energy mechanism during VIV and unsteady galloping was clarified.
Modelling nonlinear aerodynamic damping during transverse aerodynamic instabilities for slender rectangular prisms with typical side ratios
Abstract The transverse aerodynamic instabilities of rectangular cylinders with three typical side ratios (width-to-depth-ratio as 2:1, 1:1 and 1:2) were investigated through a series of elastically-supported sectional model tests. Experimental results indicate that side ratio plays an important role in the phenomena of transverse instabilities and a larger side ratio B/D generally corresponds to a stronger interaction of VIV and galloping. For side ratio B/D = 2, all test cases exhibited unsteady galloping starting from the Kármán vortex resonance wind speed. When Scruton number is larger than a threshold value between 12.1–19.4, the unsteady galloping of B/D = 1 shows a separate behavior of VIV and galloping with a twofold-amplitude phenomenon. Whereas, side ratio B/D = 0.5 exhibited a pure transverse VIV. The feasibility of classical quasi-steady theory was found not able to predict the onset wind speeds and stable amplitudes. An empirical model was established to consider the aerodynamic nonlinearity by two amplitude-dependent damping terms and aerodynamic unsteadiness by expressing aerodynamic parameters as functions of reduced frequency. The empirical model was validated, having a satisfactory accuracy in predicting the vibration amplitudes of unsteady galloping and VIV. The proposed model represents a promising tool in engineering applications where the interference of VIV and galloping is concerned.
Highlights Transverse aerodynamic instabilities of rectangular cylinders with typical side ratios were investigated. A novel empirical model was proposed for unsteady galloping and VIV. The nonlinear energy mechanism during VIV and unsteady galloping was clarified.
Modelling nonlinear aerodynamic damping during transverse aerodynamic instabilities for slender rectangular prisms with typical side ratios
Gao, Guangzhong (Autor:in) / Zhu, Ledong (Autor:in) / Li, Jiawu (Autor:in) / Han, Wanshui (Autor:in)
17.12.2019
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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