Holding Force and Vertical Vibration of Emergency Gate in the Closing Process: Physical and Numerical Modelling

Abstract

A two-dimensional unsteady fluid–structure interaction numerical model was established, based on the physical model test, to investigate the influence of vertical vibration on the holding force of an emergency gate in the closing process. Gate motion was controlled by the user-defined function in Fluent. Attention was paid to the relationship between the vertical vibration, hydrodynamic loads and flow discharge. The experiment results show that holding force has three typical forms in the closing process and it is related to the service gate height. The numerical model can reflect the gate vertical vibration and the gate-closing displacement in the form of steps. Gate vertical vibration in the closing process is a motion-induced vibration caused by gate active falling. Moreover, the transition from full-flow to open-flow behind the emergency gate has a great influence on the gate vertical vibration. With a small gate opening, gate vertical vibration makes the flow discharge fluctuation increase. Furthermore, flow discharge has an influence on the gate body loads, which is mainly concentrated in the upstream plate and gate bottom. Finally, the lift force coefficient at the gate bottom is different from the standard and is mainly controlled by the outflow boundary condition. The simulation result is in good agreement with the experiment and the relative error meets engineering requirements, suggesting that the numerical model can successfully simulate the gate fluid–structure interaction and reproduce the characteristics of physical quantities in the closing process.

Experimental Study on the Slip–Stick Vibration of Plane Gate

“…From a frequency point of view, the slip-stick vibration of the plane gate is simplified into a single degree of freedom vibration [15,[23][24][25], and the natural frequency is ω n =…”

“…To sum up, it is believed that the slip-stick vibration in the gateclosing or gate-opening processes is not caused by fluid excitation at the gate bottom based on the difference of the intensity and frequency between fluid excitation and slip-stick vibration excitation. From a frequency point of view, the slip-stick vibration of the plane gate is simplified into a single degree of freedom vibration [15,[23][24][25], and the natural frequency is ωn = 𝐸𝐴 𝐿𝑚 ⁄ (where E is the elastic modulus of steel rope, A is the cross sectional area of steel rope, L is the length of steel rope and m is the system mass). The length of steel rope increases, and the natural frequency of the equivalent system decreases, as the plane gate drops.…”