Equilibrium depth and time scale of local scour around a forced vibrating pipeline
The equilibrium depth and time scale of the scour evolution of a forced vibrating pipeline in unidirectional currents are experimentally investigated under clear-water conditions (θ < θcr, θcr = critical Shields parameter) with a water depth of 0.2–0.4 m and approach velocity of 0.125–0.261 m/s....
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sg-ntu-dr.10356-1734872024-02-07T01:34:01Z Equilibrium depth and time scale of local scour around a forced vibrating pipeline Zhang, Zhimeng Chiew, Yee-Meng Ji, Chunning School of Civil and Environmental Engineering Engineering Forced Vibration Pipeline The equilibrium depth and time scale of the scour evolution of a forced vibrating pipeline in unidirectional currents are experimentally investigated under clear-water conditions (θ < θcr, θcr = critical Shields parameter) with a water depth of 0.2–0.4 m and approach velocity of 0.125–0.261 m/s. The pipeline model with a diameter (D) of 3.5 cm, was vertically oscillated in a sinusoidal motion with varying amplitudes (A0 = 2–6 cm) and frequencies (f0 = 0.1–0.6 Hz). The initial gap (G0) between the lower pipeline surface and the undisturbed seabed was fixed at 1D. Both the equilibrium depth and the developing rate of the scour hole increase with the vibration amplitude, frequency, and the Shields parameter ratio (θ/θcr); the influence of A0 on accelerating the scour rate is more significant at high-amplitude conditions (A0 > G0) due to the direct impact of the pipe on the sand bed when compared with the low-amplitude conditions (A0 < G0). The scour time scale increases with the increase of the maximum pipe oscillation velocity and the Shields parameter ratio. A new empirical formula in exponential form for predicting the scour development history is proposed by considering the pipeline vibration effect through three different coefficients – vibration factor αe, coefficient Ce, and exponent ne. Both αe and Ce increase as the maximum pipe oscillation velocity increases. On the other hand, ne decreases with the increase of A0 and f0, where ne is mainly influenced by the vibration frequency in the low-amplitude condition, with vibration frequency only exerting a limited impact on ne in the high-amplitude condition. This work was financially supported by the National Natural Science Foundation of China (Grants No. 51779172, 51579175 and 51979186). The first author would like to acknowledge the support provided by China Scholarship Council (Grant No. 202006250062) for the one-year attachment at Nanyang Technological University (NTU). 2024-02-07T01:34:01Z 2024-02-07T01:34:01Z 2023 Journal Article Zhang, Z., Chiew, Y. & Ji, C. (2023). Equilibrium depth and time scale of local scour around a forced vibrating pipeline. Coastal Engineering, 185, 104378-. https://dx.doi.org/10.1016/j.coastaleng.2023.104378 0378-3839 https://hdl.handle.net/10356/173487 10.1016/j.coastaleng.2023.104378 2-s2.0-85172182636 185 104378 en Coastal Engineering © 2023 Elsevier B.V. All rights reserved. |
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Engineering Forced Vibration Pipeline Zhang, Zhimeng Chiew, Yee-Meng Ji, Chunning Equilibrium depth and time scale of local scour around a forced vibrating pipeline |
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The equilibrium depth and time scale of the scour evolution of a forced vibrating pipeline in unidirectional currents are experimentally investigated under clear-water conditions (θ < θcr, θcr = critical Shields parameter) with a water depth of 0.2–0.4 m and approach velocity of 0.125–0.261 m/s. The pipeline model with a diameter (D) of 3.5 cm, was vertically oscillated in a sinusoidal motion with varying amplitudes (A0 = 2–6 cm) and frequencies (f0 = 0.1–0.6 Hz). The initial gap (G0) between the lower pipeline surface and the undisturbed seabed was fixed at 1D. Both the equilibrium depth and the developing rate of the scour hole increase with the vibration amplitude, frequency, and the Shields parameter ratio (θ/θcr); the influence of A0 on accelerating the scour rate is more significant at high-amplitude conditions (A0 > G0) due to the direct impact of the pipe on the sand bed when compared with the low-amplitude conditions (A0 < G0). The scour time scale increases with the increase of the maximum pipe oscillation velocity and the Shields parameter ratio. A new empirical formula in exponential form for predicting the scour development history is proposed by considering the pipeline vibration effect through three different coefficients – vibration factor αe, coefficient Ce, and exponent ne. Both αe and Ce increase as the maximum pipe oscillation velocity increases. On the other hand, ne decreases with the increase of A0 and f0, where ne is mainly influenced by the vibration frequency in the low-amplitude condition, with vibration frequency only exerting a limited impact on ne in the high-amplitude condition. |
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School of Civil and Environmental Engineering |
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School of Civil and Environmental Engineering Zhang, Zhimeng Chiew, Yee-Meng Ji, Chunning |
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Article |
author |
Zhang, Zhimeng Chiew, Yee-Meng Ji, Chunning |
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Zhang, Zhimeng |
title |
Equilibrium depth and time scale of local scour around a forced vibrating pipeline |
title_short |
Equilibrium depth and time scale of local scour around a forced vibrating pipeline |
title_full |
Equilibrium depth and time scale of local scour around a forced vibrating pipeline |
title_fullStr |
Equilibrium depth and time scale of local scour around a forced vibrating pipeline |
title_full_unstemmed |
Equilibrium depth and time scale of local scour around a forced vibrating pipeline |
title_sort |
equilibrium depth and time scale of local scour around a forced vibrating pipeline |
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2024 |
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https://hdl.handle.net/10356/173487 |
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