Predicting In-Canopy Velocity and Retention Time for Aquatic Canopies

预测植被对速度异质性和运输的影响Heidi Nepf水生植被以几种方式影响水和栖息地质量。 水生植物吸收营养并产生氧气。它们产生减小床应力的区域，促进颗粒的保留并影响形态演变。 众所周知，淹没和露出的树冠都能减缓波浪，减少海岸和河岸的侵蚀。 最后，通过引入空间异质性的速度场，植被增加栖息地的多样性，从而物种多样性。由于它的许多好处，一些研究人员现在提倡广泛的重新种植和基于生态的管理渠道和沿海植被。在以前的赠款（EAR0309188，EAR0125056），PI描述了流动和运输长，紧急和淹没冠层，即纵向范围远大于冠层的高度或宽度。 这些项目使用刚性冠层模型，这是一个合理的替代挺水植被，但不太适合沉水植物，往往是灵活的。 连续的刚性座舱盖是必要的第一步，因为它很容易通过数学模型表示，允许鲁棒的模型测试。 我们现在准备建立在这些第一个简单的模型，并探索在自然界中存在的树冠形态的范围。 这项工作将分两部分进行。 其中一个项目将开发单向流和波浪下的柔性树冠模型。 第二个将开发模型淹没和紧急冠层的有限长度和宽度，几何形状，现有的二维模型不适用。 第二个项目将再次使用刚性檐篷，以方便测试新的数学模型。 这两个部分有很强的智力协同作用。 从事这两项工作的学生将举行小组会议，共享共同的实验室空间，新的想法将在项目之间快速转移，每个项目将受益于不同形态的持续比较和对比。 植被水动力学的联合活动也将吸引更多的访问学者，为工作带来新的想法和观点。 第二，有限冠层项目被设想为使用刚性模型。 当同时工作时，柔性顶篷项目将提供如何将刚性模型适应柔性顶篷的见解，并将提供一个柔性顶篷来测试这些见解。 通过这种方式，有限冠层的研究将进一步扩大新的有限冠层模型灵活的形态。 第三，植被对波浪阻尼的研究将大大扩展，因为柔性和刚性冠层模型将在实验室中可用。 由于湖泊和海洋海岸都有淹没柔性冠层和刚性应急冠层的区域，因此描述这两个区域的波浪阻尼特性非常重要。 这项工作将通过在圣安东尼福尔斯实验室（明尼苏达大学）的野外规模户外溪流实验室中进行真实的植被实验，朝着实地测试迈出重要一步。 生态学家，地质学家和流体力学家将同时使用室外流实验室，促进跨学科的联系。

Predicting the Impact of Vegetation on Velocity Heterogeneity and TransportHeidi NepfAquatic vegetation impacts water and habitat quality in several ways. Aquatic plants remove nutrients and produce oxygen. They create regions of diminished bed stress that promote the retention of particles and influence morphological evolution. Both submerged and emergent canopies are known to damp waves and reduce coastal and bank erosion. Finally, by introducing spatial heterogeneity to the velocity field, vegetation increases habitat diversity, and thus species diversity. Because of its many benefits, some researchers now advocate wide spread replanting and ecologically based management of channel and coastal vegetation.Under previous grants (EAR0309188, EAR0125056), the PI has described flow and transport in long, emergent and submerged canopies, i.e. with longitudinal extent much larger than canopy height or width. These projects used rigid canopy models, which are a reasonable surrogate for emergent vegetation, but are less appropriate for submerged plants, which tend to be flexible. The continuous, rigid canopy was a necessary first step, as it is easily represented through mathematical models, allowing robust model testing. We are now ready to build on those first simple models and explore the range of canopy morphology present in nature. This work will proceed in two parts. One project will develop models for flexible canopies under both unidirectional flow and waves. The second will develop models for submerged and emergent canopies of finite length and width, geometries for which the existing two-dimensional models do not apply. The second project will again use rigid canopies to facilitate the testing of new mathematical models. The two parts have strong intellectual synergy. The students working on the two will hold group meetings and share common lab space, new ideas will be quickly transferred between projects, and each project will benefit from ongoing comparison and contrasting of different morphologies. The combined activity in vegetation hydrodynamics will also attract more visiting scholars, bringing new ideas and perspectives to the work. Second, the finite-canopy project was conceived to use rigid models. When working simultaneously, the flexible canopy project will provide insight into how one adapts rigid models to flexible canopies and will also provide a flexible canopy for testing these insights. In this way, the finite-canopy study will progress much further in extending new finite-canopy models to flexible morphologies. Third, the study of wave-damping by vegetation will be greatly expanded, because both flexible and rigid canopy models will be available in the lab. Because both lake and ocean coasts have zones of submerged flexible canopies as well as rigid emergent canopies, it is important to characterize wave damping in both zones. The work will take an important step toward field testing through experiments with real vegetation in the field-scale Outdoor StreamLab at the Saint Anthony Falls Laboratory (Univ. of Minnesota). Ecologists, geologists, and hydrodynamicists will be using the Outdoor StreamLab simultaneously, facilitating inter-disciplinary connections.