大坝泄洪下游水体溶解气体超饱和理论分析及应用

根据溶解气体的传输过程,对大坝泄洪导致下游水体溶解气体浓度超饱和现象进行了理论分析.引入溶解气体的有效饱和浓度、气泡被卷吸进入水体的有效水深等参数,认为下游水体中溶解气体的来源不仅依赖于大气在自由水表面的传质,而更多地依赖于气体在气泡界面的传质.把难以测量的气体传质系数、气泡尺寸等参数与水流的紊动特性参数建立定量关系,以美国Ice Harbor大坝为例,采用该定量关系式计算了下游水体中溶解气体浓度的分布,实测结果验证了理论分析的合理可靠性.

Theoretical analysis of dissolved gas supersaturation downstream of sluicing dam and application

According to the transfer processes of gas, a theory is analyzed for dissolved gas supersaturation downstream of the sluicing dam. The effective saturation concentration and the effective depth where bubbles are entrapped into water are introduced to explain consideration of the gas transfer across both the water surface and the bubble interface. It is difficult to measure many parameters such as the gas transfer coefficients, the bubble size, the air void ratio and so on. So the quantitative relations between these parameters and the water turbulence parameters, such as flow velocity, turbulence kinetic energy, are developed. Taking the Ice Harbor dam in U.S. for example, the dissolved gas concentrations downstream of the dam are simulated using the theoretical relations. The local measured data show the validation of the theory.