水电站进水塔动水压力研究和探讨

基于理想流体,将进水塔简化成水中悬臂梁体系,推导了其受迫振动时的动力响应方程,给出了进水塔内外表面动水压力的解析表达式。与有限元法、水工抗震规范公式计算结果进行了对比,分析验证了该方法在进水塔结构上的适用性及准确性。结果表明:动水压力表达式与结构振型密切相关。该方法的动水压力曲线趋势与有限元方法相似,均在水面以下某深度处迅速变大及达到最大值后曲线值减小弯回,两者最终在塔体底部收于相近的值;最大值大于有限元法,其最大值处曲线折回明显,幅度较大。弹性模量和进水塔高度对动水压力的曲线形态和数值有重要影响。同时,输入激励荷载的频率对动水压力影响巨大,尤其频率与进水塔某阶频率相近时会导致动水压力的异常增大。该方法对分析进水塔动水压力具有参考价值。

Study and discussion on hydrodynamic pressure at intake tower of hydropower station

Based on ideal fluid，the intake tower is simplified into a cantilever beam system in water，and then the equation for its dynamic response under forced vibration is deduced，thus the analytical expression for the inside and outside surface hydrodynamic pressures of the intake tower is given out. From which the result is compared with the calculation results from both the finite element method and the formulas given in the code for seismic design of hydraulic structures，while the applicability and accuracy of the method when it used for the structure of intake tower are analyzed and verified. The result shows that the expression of hydrodynamic pressure is closely related to the vibration pattern of the structure. The trend of the dynamic pressure curve from this method is similar to that from the finite element method，i.e. both of them are rapidly enlarged at a certain depth under water surface and then the curve values are reduced and bended back after reaching to the maximum values，and finally become the similar values at the bottom of the tower； of which the maximum value is larger than that from the finite element method with an obvious turn-back of the curve of large amplitude at the maximum value. The elastic modulus and the height of the intake tower have important effects on the curve pattern and numerical values of the hydrodynamic pressure. Meanwhile，the frequency of the input load has great impact on the hydrodynamic pressure，especially the abnormal enlargement of the hydrodynamic pressure is to be caused when the frequency is close to a specified frequency of intake tower. The method has reference value for the analysis made on hydrodynamic pressure of intake tower.