An important part in designing stepped spillways is making the spillway in order to direct the flow appropriately on the first step. In low discharges, the water flow moves over the spillway and arrives at the first step, and if the first step is high enough, the flow may leave the first step horizontally, skip some steps and land as a free jet of water on the lower steps, which might cause some damages to the structure. One of the solutions to this problem is to use CEDEX profile, transition steps between the ogee crest and the stepped chute. The present research carries out a numerical study of the effects of CEDEX profile on various hydraulic parameters and also the effects of the chute slope on the performance of this profile in preventing the flow jump. For this purpose, four models were created with different geometries and were studied in various discharges with FLOW-3D software. The results show that deploying CEDEX profile in the initial parts of the spillway leads to lower velocity and less risk of cavitation. Also, the results illustrate that CEDEX profile can shift the inception point of aeration to downstream. Furthermore, findings show that CEDEX profile, in the slope of less than 50°, can prevent flow jump in the first step. In steeper slopes, however, it fails to achieve the optimal performance.

中文翻译：

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CEDEX剖面对阶梯式溢洪道水力参数影响的数值研究及该剖面在各种滑槽坡度中的性能

设计阶梯式溢洪道的一个重要部分是建造溢洪道，以便在第一步适当地引导水流。在低流量时，水流越过溢洪道到达第一步，如果第一步足够高，水流可能会水平离开第一步，跳过一些台阶并以自由射流的形式降落在较低的地方台阶，这可能会对结构造成一些损坏。解决此问题的方法之一是使用 CEDEX 型材，即 ogee 顶部和阶梯式溜槽之间的过渡台阶。本研究对 CEDEX 剖面对各种水力参数的影响以及斜槽斜率对该剖面防止流动跳跃的性能的影响进行了数值研究。以此目的，创建了具有不同几何形状的四个模型，并使用 FLOW-3D 软件在各种放电中进行了研究。结果表明，在溢洪道的初始部分部署 CEDEX 剖面会导致较低的流速和较小的气穴风险。此外，结果表明 CEDEX 配置文件可以将曝气的起始点转移到下游。此外，研究结果表明，CEDEX 剖面在小于 50°的斜率中可以防止第一步中的流动跳跃。然而，在较陡的斜坡上，它无法达到最佳性能。研究结果表明，CEDEX剖面在小于50°的斜率下，可以防止第一步的流动跳跃。然而，在较陡的斜坡上，它无法达到最佳性能。研究结果表明，CEDEX剖面在小于50°的斜率下，可以防止第一步的流动跳跃。然而，在较陡的斜坡上，它无法达到最佳性能。