脉动压力在板块缝隙中传播衰变机理研究

探讨高坝下游水垫塘内脉动压力在底板缝隙水介质中的传播机理,分析缝隙粗糙程度及堵塞程度对脉动压力传播的衰变影响,进一步阐明脉动压力在水垫塘底板破坏中的作用。基于一维瞬变流模型和特征线法,同时考虑缝隙通道的阻滞作用,对脉动压力在缝隙中的传播进行数值模拟,得出单体板块入口端瞬时感应到低频余弦脉动压力干扰波、出口端分别为盲端和自由端时,不同堵塞系数下底板缝隙中点处的点脉动压力时间过程。分析得出:缝隙中点处的脉动压力是由低频干扰波和由于缝隙中类似于水击的水力瞬变引起的高频波的叠加。受缝隙通道阻滞作用,脉动压力的高频脉动分量在短时间内迅速衰变,时间过程曲线趋于与干扰波同频率的余弦曲线。

Study on mechanism of pulsating pressure propagation disintegration in joints of bottom slab

The propagation of pulsating pressure of water within joints of bottom slab on the downstream plunge pool for high dam is discussed herein; in which the roughening and blocking effects of the joints on the propagation disintegration of pulsating pressure are discussed and the damaging effect of the pulsating pressure on the bottom slab of plunge pool is further illustrated. Based on the one-dimensional model of transient flow and method of characteristics, the pulsating pressure propagation disintegration in joints of bottom slab is numerically simulated and then obtains the duration of the point pulsating pressure at the points of the bottom slab under different blocking coefficients from the instantaneous induction at the entrance end of the single slab to the disturbing wave of low-frequency cosine pulsating pressure when the outlet ends of the slab are blind end and free end respectively. The analysis gives that the pulsating pressure at the point of joint is the superposition of both the low-frequency disturbing wave and the high-frequency wave caused by the hydraulic transient similar to the water hammer within the joints. Under the blocking effect of the passage in the joint, the high-frequency pulsating component of the pulsating pressure is to be rapidly disintegrated in short time, and the time-depended duration curve is to be towards the cosine curve with the frequency similar to that of the disturbing wave.