Large wood (LW) is used for river restoration, aquatic habitat conservation, and flood control; however, it can pose a threat to human life and the built environment. The formation of LW jams, river management strategies, and design of mitigation measures crucially all depend on how the large wood is transported along a river. This paper experimentally analyses at laboratory scale the motion of natural sticks in a long stretch of a straight channel (16 m), when LW is released at different locations and with different flow conditions. Results show that instream large wood, following a transient motion shortly after being released at the water surface, tends to follow preferential patterns along the channel. Froude number and location of large wood input may provide an estimation of the LW location in downstream reaches. Several mechanisms of motion were observed, some of which were very common, including a frequent tendency to assume a tilted position with respect to the direction parallel to the flow. The experiments also suggest that theories on secondary cells responsible for channeling LW in preferential directions are incomplete. A new model, based on acceleration induced by hydrodynamic actions, has been established and proposed in this work, showing promising results and paving the way for the development of a comprehensive model for transport of large wood at the river surface in full-scale applications.

中文翻译：

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模拟河流中大型木材位移的实验和数值方法

大木材 (LW) 用于河流修复、水生栖息地保护和防洪；然而，它可能对人类生命和建筑环境构成威胁。LW 堵塞的形成、河流管理策略和缓解措施的设计都取决于大木材如何沿河流运输。本文在实验室规模上通过实验分析了天然木棒在一段长直通道中的运动（16 m)，当 LW 在不同位置和不同流动条件下释放时。结果表明，在水面释放后不久的瞬态运动后，入流的大木材往往会沿着通道遵循优先模式。大量木材输入的 Froude 数量和位置可以提供下游河段 LW 位置的估计。观察到了几种运动机制，其中一些非常常见，包括经常倾向于相对于平行于流动的方向采取倾斜位置。实验还表明，负责在优先方向上引导 LW 的二次电池的理论是不完整的。在这项工作中，已经建立并提出了一种基于水动力作用引起的加速度的新模型，