Predicting the motion of driftwood around hydraulic structures such as bridge piers and spur dikes is important. We propose a numerical model for simulating driftwood motion that is based on coupling an Eulerian-type three-dimensional flow model and a Lagrangian-type two-dimensional driftwood model. Laboratory tests were carried out on the driftwood motion in a curved channel and around obstacles to obtain reference data. The computational results showed that three-dimensional flow features considerably affect the motion of driftwood in a curved channel. We defined the driftwood Richardson number (DRI) to classify the three-dimensional behavior of driftwood around obstacles. The experimental results showed that an increasing DRI indicates more three-dimensional behavior by driftwood and a decreased capture ratio by obstacles. We also developed a two-way model in which the drag force from driftwood on the flow is modeled to simulate the backwater elevation and the flow deceleration behind the stacked driftwood. The computational results showed that the two-way model could reproduce the increase of water level and the decrease of velocity at the upstream region of the obstacles. However, such effects caused by the driftwood jamming were underestimated if the jamming happened in a three-dimensional manner.

中文翻译：

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浮木理查森数的影响以及3D–2D模型对障碍物周围的重木阻塞的适用性

预测浮木在水力结构（例如桥墩和丁坝）周围的运动非常重要。我们提出了一个模拟浮木运动的数值模型，该模型基于耦合欧拉型三维流动模型和拉格朗日型二维浮木模型。对浮木在弯曲通道和障碍物周围的运动进行了实验室测试，以获取参考数据。计算结果表明，三维流动特征极大地影响了浮木在弯曲通道中的运动。我们定义了浮木理查森数（DRI）来对障碍物周围的浮木的三维行为进行分类。实验结果表明，DRI的增加表明浮木具有更多的三维行为，而障碍物的捕获率却降低。我们还开发了一种双向模型，其中对浮木对水流的拖曳力进行了建模，以模拟死水高程和堆积的浮木后面的水流减速。计算结果表明，双向模型可以再现障碍物上游区域水位的升高和速度的降低。但是，如果卡纸以三维方式发生，则低估了由浮木卡纸引起的这种影响。