free water surface meaning in Chinese

地下水位
自由水面

In order to study the characteristics of the stepped spillway overflow comprehensively and seek for the measure to increase the energy dissipation of the stepped spillway at large unit discharge , the method of turbulence numerical simulation and model test are used to study the stepped spillway overflow . in view of the curved free water surface , complicated boundary condition and turbulence flow , it very difficult to simulate the stepped spillway overflow
为了对阶梯溢流坝面流场特性进行全面的研究，同时探求在大单宽流量下提高阶梯溢流坝消能率的措施，本文采用紊流数值模拟与实验相结合，数值计算为主、实验为辅的研究方法对阶梯溢流坝面流场进行了较系统深入的研究。