河道人工湿地的构建及其对河道水流的影响

Wetland construction along river course and its effect on water flow

提出了河道人工湿地的构建方法:在河道两侧的滩地上,每间隔一段距离设一弦长为S、弓高为B、高程在正常水位以下0.5 m的圆弧形扩展段,且扩展段于河道两侧呈犬牙交错状布置,洪没枯出形成旱湿交替的人工湿地场.采用三维湍流数值计算和分析方法,优化确定河道人工湿地断面的主要参数S和B,使人工湿地内获得了最佳水流条件.算例模拟计算表明,河道人工湿地床体主要构建参数的最优值为S=2.0D,B=0.7D(D为河道口宽).从河道流场、断面平均流速沿程分布及垂线平均流速横向分布3方面分析了人工湿地对河道水流的影响.分析结果表明:人工湿地构成后,整体河道会形成缓变与急变交错的流态;人工湿地段断面平均流速明显衰减;湿地与河道主槽内的水流流速差异较大.

The method for wetland construction was proposed, i.e. to construct eircular expanding section at certain intervals along the beach of two sides of river course with the chord length S and the arc height B at the elevation of 0.5m below the normal water level. The staggered arrangement of the expanding section forms wetlands of wet-dry alternation. In the study, 3D numerical calculation and analysis method of turbulent flow was adopted for optimization of the main parameters S and B for the cross-section of wetlands so that the optimal river flow condition could be obtained, and the optimal values S = 2.0D and B = 0.7D （D： the width of river mouth） for the constructed wetlands were derived from ease study. Then, the effects of wetland construction on river flow were analyzed from three aspects, i.e. the flow field of river the course, the cross-section average flow velocity distribution along river course, and the depthaveraged flow velocity distribution in river eross-section. The result shows that wetland eonstruction leads to alternate flow patterns in the whole river course, that the mean flow velecity in cross-section of the wetland section decreases evidently, and that the difference of flow velecity between wetland section and main river channel is significant.