有限宽度桩体绕流的阻塞效应数值模拟研究

Numerical Simulation Study on the Blockage Effect of Flow around Finite Width Piles

有限宽度水槽或风洞研究桩体绕流流场特性引起阻塞效应,导致绕流场脱落涡受壁面在横向、纵向的压缩,使桩周力学参数变化。采用数值模拟的方法研究不同阻塞比条件下三维绕流流场的重整效应、桩周阻力系数、表面压力、分离角以及St等参数的变化规律,研究结果表明:①平均阻力系数及脉动升力系数随阻塞比增大而增大,而脉动阻力系数减小;②随阻塞比增大,桩周表面压力增大,分离角增大,且脱落涡的强度增大;③存在临界阻塞比,大于该值时,绕流流场发生根本性改变;④小阻塞比时,流场St及阻力系数与阻塞比近似呈线性相关。该成果可供机组桩基绕流相关荷载分析、设计等参考。

The study on the flow field characteristics around piles using finite width water channel or wind tunnel could cause blockage effect,resulting in horizontal and vertical compression of the shedding vortex wall in the flow field and the changes of the mechanical parameters around the piles.Thus,numerical simulations are carried out to study the reforming effect of the three-dimensional flow field around piles and the variation of the pile resistance coefficient,surface pressure,separation angle,and St parameters under different blockage ratios.The results show that the average resistance coefficient and the pulsating lift coefficient increase with the increase of the blockage ratio,while the pulsating resistance coefficient decreases.With the increase of the blockage ratio,the surface pressure around piles and the separation angle increase,and the strength of the shedding vortex increases.When the blockage ratio exceeds a critical value,the flow field undergoes fundamental changes.When the blockage ratio is small,the St value and the resistance coefficient are approximately linear with the blockage ratio.The results can be useful reference for the analysis and design of loads related to the flow around pile foundation of units.