曝气诱导内波破坏水库水温分层的过程与效果

Process and effectiveness of destratification by aeration-induced internal waves in a reservoir

针对传统的水库破坏分层技术的低效率、高能耗等普遍问题,研制了能模拟基于自然对流而形成水温分层的中试模型水库,研究了曝气诱导形成内波混合破坏水温分层的可行性,过程和效果.扬水曝气产生的周期性出流能作为扰动源,在分层水环境中诱导形成内波.内波频率及波幅与曝气量有关.在曝气量0.07~0.28m3/（m2·h）,跃温层温度梯度0.29~0.48℃/m的中试条件下,内波破坏分层过程主要以减小表层和底层水温差别、驱使跃温层下潜、等温层变薄为特征,破坏分层的速度与曝气量正相关、与温度梯度负相关.内波通过垂向振荡和横向传播,促进不同温度的水层之间的热交换.相对传统的循环水流混合,在温度梯度约0.32℃/m和0.46℃/m的条件下,当曝气量从0.07m3/（m2·h）逐渐增加到0.28m3/（m2·h）时,内波混合可分别将破坏分层效率提高25.0%~40.0%和41.2%~60.0%.

Aiming at the common problems of conventional destratification technologies such as high energy consumption and low energy efficiency,a pilot model reservoir with a thermal structure evolved from the natural convection was developed and constructed,the feasibility of developing internal waves induced by aeration was explored,and the process and effectiveness of destratification by internal waves were analyzed. Periodic outflow from the water-lifting aerator could act as a disturbing source to generate internal waves in stratified water environments,and the periods and amplitudes of internal waves depended on the air flowrate. Under the experimental air flowrates of 0.07~0.28m3/（m2·h） and temperature gradients of 0.29~0.48℃/m in the thermocline,the destratification process was mainly characterized by reducing the temperature difference between epilimnion and hypolimnion,impelling the thermocline downwards and thinning the hypolimnion,the speed of destratification increased with the air flowrate but decreased with the temperature gradient. Heat exchange between water layers of different temperatures could be enhanced through vertical fluctuations and horizontal propagation by internal waves. Compared with the conventional destratification by circulated flow,under the temperature gradients of 0.32℃/m and 0.46℃/m,when the air flowrate was increased from 0.07m3/（m^2·h） to 0.28m3/（m^2·h）,the efficiencies of destratification by internal waves could be increased by 25.0%~40.0% and 41.2%~60.0%,respectively.