THE INCLUSION OF VORTICAL FLOW STRUCTURES IN ANALYTIC DEPTH-AVERAGED FLOW MODELS OF FLOODING

本文主要研究明渠流动中纵向涡量和平台涡量之间的基本相互作用。平台涡度先验地排除在所有雷诺平均纳维-斯托克斯（RANS）方程模型之外，但已知在大多数河岸上流动中存在。Shiono & Knight分析方法（SKM）是一种分析方法，用于模拟垂直结构的影响，模拟4个关键的主导流动过程，避免使用三维湍流模型，并适用于全尺寸。尽管最近在HR Wallingford的工作证实了SKM方法的价值，但已知F（涡度相关）的原始辅助方程不适用于某些类型的非棱柱形洪泛平原和强烈蜿蜒的河流。一种很有前景的方法是使用两层SKM模型，将深度平均过程垂直地分成两部分，分别位于富油阶段的上方和下方。这允许将横向切片模型放置在另一个切片模型的顶部，并添加水平面间剪切。然后，每个薄片中较低的F值代表顺流的二次流，而较高的F值模拟了漫滩/主河道边界的二次流和平面涡度。与更复杂的三维湍流模型（LES或RANS）相比，这为这些类型的通道提供了一个更简单的二维深度平均方法，具有SKM的所有优点。我们需要探索这种新颖的理论方法，并评估它是否可以转化为实用的电子表格工具，供工程师模拟洪水使用。

This proposal focuses on the fundamental interaction between longitudinal & planform vorticity in open channel flow. Planform vorticity is a priori excluded from all Reynolds averaged Navier-Stokes (RANS) equation models, but is known to be present in most overbank flows . The Shiono & Knight method of analysis (SKM) is an analytic approach to modelling the influence of vortical structures, mimics 4 key dominant flow processes, avoids the use of 3-D turbulence models and applies at full scale.Despite the value of the SKM approach being confirmed by recent work at HR Wallingford, the original ancillary equations for F (vorticity linked) are known to be inadequate for certain types of non-prismatic floodplains and strongly meandering rivers. One promising approach is to use a two-layer SKM model, splitting vertically the depth-averaging process into two parts, above and below the bankfull stage. This allows a laterally sliced model to be placed on top of another sliced model, with horizontal inter-facial shear added. The lower F values in each slice then represent the streamwise secondary flows, and the upper ones mimic both secondary flows at floodplain/main channel boundaries and plan form vorticity. This produces a much simpler 2-D depth-averaged approach for these types of channel, with all the advantages of SKM, over more complex 3-D turbulence models (LES or RANS). Work is needed to explore this novel theoretical approach, and to assess whether it can be turned into practical spreadsheet tools for use by engineers modelling floods.