新型人工浮岛流场数值模拟与结构优化分析

Numerical simulations of the flow field and analyses of the optimal filling structure for a new type of constructed floating island

近期提出的新型人工浮岛是通过两种不同透水能力基质材料的填充在系统内部形成2个不同水流与溶解氧浓度区域,两区域的过流能力及两者之间水流交换量对系统脱氮除磷效果具有较大的影响。为实现这一新型人工浮岛基质结构设计参数的优化,进一步提高净化能力,应用数值模拟方法对不同结构条件下流场进行了模拟。模拟结果发现,影响两区域水流交换量及其过流能力的主要因素包括:基质材料的填充形状、填充深度及透水能力,其中"钟乳状"形态较"层状"填充形态人工浮岛具有更好的两区域间水流交换能力及过流能力,理论上具有更好的净化效果。根据模拟结果确定的设计参数构建小试试验系统进行对比试验研究,试验结果与数值模拟结论吻合。可见,采用数值模拟方法对人工浮岛内部水流状态进行模拟分析,能够为人工浮岛结构优化设计提供依据。

A new remediation approach for effective removal of nitrogen and phosphorus from surface water called multi-media constructed floating island was previously proposed in which two types of different filling media were used and two zones with different flow statuses and DO concentrations can be established.The water flux in each zone and water exchanges between the two zones control considerably removal efficiency of nitrogen and phosphorus.The numerical simulation approach was implemented to investigate the flow field of the proposed constructed floating island in order to identify the primary factors controlling the flow field and understand the op- timal design of filling structure. The numerical simulation results showed that the filling shape of the porous medium, filling depth of the porous medium, and hydraulic conductivities of the filling media determined essentially water flux in each zone and water exchanges between the two zones. It was computed that the stalactitic filling structure generated more water fluxes in the porous medium zone and water exchanges between the two zones than the layered filling structure, which indicated theoretically the former should offer more effective removal of N and P than the latter. A filed pilot-scale experiment was implemented and the consistent experimental results were ob- tained with the numerical simulation analyses.