Understanding the strengths and limitations of the modeling capacity of surface flooding in urbanized floodplains is of utmost importance as such events are becoming increasingly frequent and extreme. In this study, we assess two computational models against laboratory observations of surface urban flooding in a reduced-scale physical model of idealized urban districts. Four urban layouts were considered, involving each three inlets and three outlets as well as a combination of three- and four-branch crossroads together with open spaces. The first model (2D) solves the shallow-water equations while the second one (3D) solves the Reynolds-averaged Navier-Stokes equations. Both models accurately predict the flow depths in the inlet branches. For the discharge partition between the outlets, deviations between the computations and laboratory observations remain close to the experimental uncertainties (maximum 2.5 percent-points). The velocity fields computed in 3D generally match the measured surface velocity fields. In urban layouts involving mostly a network of streets, the depth-averaged velocity fields computed by the 2D model agree remarkably well with those of the 3D model, with differences not exceeding 10%, despite the presence of helicoidal flow (revealed by the 3D computations). In configurations with large open areas, the 3D model captures generally well the trajectory and velocity distribution of main surface flow jet and recirculations; but the 2D model does not perform as well as it does in relatively channelized flow regions. Visual inspection of the jet trajectories computed by the 2D model in large open areas reveals that they substantially deviate from the observations.

中文翻译：

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城市化洪泛区地表洪水的 2D 和 3D 计算建模：各种建筑布局的建模性能

了解城市化洪泛区地表洪水建模能力的优势和局限性至关重要，因为此类事件变得越来越频繁和极端。在本研究中，我们根据理想化城市地区缩小规模的物理模型中地面城市洪水的实验室观察结果评估了两种计算模型。考虑了四种城市布局，分别涉及三个入口和三个出口，以及三分支和四分支十字路口与开放空间的组合。第一个模型 (2D) 求解浅水方程，而第二个模型 (3D) 求解雷诺平均纳维-斯托克斯方程。两种模型都能准确预测入口支管的流动深度。对于出口之间的排放分区，计算和实验室观察之间的偏差仍然接近实验不确定性（最大 2.5 个百分点）。以 3D 形式计算的速度场通常与测量的表面速度场相匹配。在主要涉及街道网络的城市布局中，尽管存在螺旋流（由 3D 计算揭示），但 2D 模型计算的深度平均速度场与 3D 模型计算的深度平均速度场非常吻合，差异不超过 10% ）。在具有大开放区域的配置中，3D 模型通常可以很好地捕获主表面流射流和再循环的轨迹和速度分布；但二维模型的表现不如在相对通道化的流动区域中的表现好。对大面积开放区域中二维模型计算出的射流轨迹进行目视检查表明，它们与观测结果存在很大偏差。