Model Experimental on Dynamic Response of Deep-Sea Suspended Intake Riser under Internal and External Flow Effects
To study the impact of internal and external flows on the dynamic response of large-diameter,high internal flow velocity deep-sea suspended intake riser,the application of water intake riser in practical engineering is provided as a reference.Based on small-scale model experiments,the dynamic response characteristics of pipelines under internal and external flow,as well as the influence of top connection methods and bottom counterweights on their response are analyzed.The results reveal that the dominant modal and frequency responses to vortex-induced vibration mainly depend on the external flow velocity.Variations in internal flow velocity do not significantly affect the dominant vibration frequency but increase the tendency of the pipeline to shift to higher-order modes.Increased external flow leads to a transition in the Pl pipeline's vibration response from a single mode to multi-modal participation,making the"locking"phenomenon between vortex shedding and natural frequency,as well as modal transitions,more pronounced.When external flow is present,the displacement amplitude of the pipeline is primarily influenced by the external flow velocity.Participation of external flow increases motion periodicity,but as the external flow velocity increases,the water intake riser transitions from single-frequency vibration to complex multi-frequency vibration due to vortex-induced motion,gradually weakening the motion periodicity.The bottom displacement amplitude root mean square of the top-fixed pipeline is larger.When the outflow velocity is low,the counterweight significantly affects the pipeline's amplitude,especially when the counterweight constitutes 50％or more of the riser's weight,showing noticeable differences compared to scenarios without concentrated mass.The findings of this study are significant for refining theoretical models of suspended intake pipelines under internal and external flow conditions,and can provide certain references for the design and engineering implementation of actual deep-sea suspended intake risers.
suspended intake riservortex-induced vibrationinternal and external flowmodal transitionexperimental study
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