一、引言许多环境水流的问题都涉及到非均匀旋转水流态中物质的混掺和传输。在这些流态中,由于运动主流方向是连续变化的,其扩散应作为二阶张量来处理。这类旋转流流态的实例有:沿不规则河堤、过水建筑物的背水面、港湾的死水区以及大范围急流区所产生的回流或二次流。明渠中的二次流已被各种研究人员所探讨或进行了相应的模型试验。研究表明,这类流 I. INTRODUCTION Many environmental water flow problems involve the mixing and transport of materials in non-uniform swirling flow regimes. In these flow regimes, since the direction of the mainstream motion is continuously changing, the diffusion should be treated as a second-order tensor. Examples of such swirling flow regimes are backflow or secondary flow along irregular embankments, backwater of over-water structures, backwater areas in harbor areas, and large-area rapid-flow areas. The secondary flow in the open channel has been explored by various researchers or has been modeled accordingly. Research shows that such flows