A numerical study of the load on cylindrical piles exerted by internal solitary waves

摘要

A continuously stratified nonlinear model is employed to simulate the generation of internal solitary waves (ISWs) over a sill by tidal flows, and it is shown that the simulated ISW-induced current field basically agrees with that observed. Then the force and torque on a supposed small-diameter vertical cylindrical pile exerted by the simulated ISW packet are calculated. According to the calculation, it is found that, no matter whether the direction of the ISW-induced current is the same as that of the tidal current or not, the force exerted by the ISW would be much larger than that by only the tidal current; if the direction of the ISW-induced current is the same as that of the tidal current, then the torque exerted by the ISW would also be much larger than that by only the tidal current; whilst if the direction of the ISW-induced current is against that of the tidal current, then the torque exerted by the ISW has the same order as that exerted by only the tidal current. It is shown that, under the same conditions, the maximum force on the cylindrical pile is 6.58 × 10~2 kN, which is larger than that by the modal separation method of Cai et al., whilst the maximum torque is 2.46 × 10~5 kN m, which is less than that given by Cai et al. During the passage of the ISW, the time series of the force and torque on the cylindrical pile can also be shown. Finally, the effect of the characteristics of the Gaussian sill on the force is studied, and the resulted empirical formulas on the force with the wave amplitude and the non-dimensional variable of the sill parameters are put forward.