Predicting In-Canopy Velocity and Retention Time for Aquatic Canopies

预测植被对流速非均质性和运输的影响研究海带植被对水和生境质量的影响有几个方面。水生植物除去营养物质并产生氧气。它们创造了减少床应力的区域，促进颗粒的保留并影响形态进化。众所周知，淹没和浮现的树冠都能抑制海浪，减少海岸和河岸的侵蚀。最后，通过引入速度场的空间异质性，植被增加了生境多样性，从而增加了物种多样性。由于它的许多好处，一些研究人员现在提倡广泛的补种和基于生态的渠道和海岸植被管理。在先前的拨款（EAR0309188, EAR0125056）下，项目已经描述了长、涌现和淹没冠层的流动和运输，即纵向范围远远大于冠层高度或宽度。这些项目使用刚性冠层模型，这是一个合理的替代应急植被，但不太适合淹没植物，往往是灵活的。连续的、刚性的顶篷是必要的第一步，因为它很容易通过数学模型表示，允许稳健的模型测试。我们现在准备在第一个简单模型的基础上，探索自然界中存在的冠层形态的范围。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柔性树冠的模型。第二部分将开发有限长度和宽度的水下和紧急冠层模型，现有二维模型不适用于这些几何形状。第二个项目将再次使用刚性天篷，以方便测试新的数学模型。这两个部分具有很强的智力协同作用。在这两个项目上工作的学生将举行小组会议并共享共同的实验室空间，新的想法将在项目之间快速传递，每个项目都将从不断的比较和对比不同的形态中受益。植被流体动力学的联合活动也将吸引更多的访问学者，为工作带来新的思路和视角。其次，有限冠层项目被设想为使用刚性模型。当同时工作时，柔性树冠项目将提供如何将刚性模型适应于柔性树冠的见解，并将提供一个柔性树冠来测试这些见解。这样，有限冠层的研究将在将新的有限冠层模型扩展到柔性形态方面取得更大的进展。第三，由于实验室将同时提供柔性和刚性冠层模型，植被减波研究将得到极大的拓展。由于湖泊和海洋海岸都有水下柔性冠层和刚性涌现冠层，因此表征这两个区域的波浪阻尼是很重要的。这项工作将通过在圣安东尼瀑布实验室（明尼苏达大学）的野外尺度户外流实验室进行真实植被实验，向实地测试迈出重要的一步。生态学家、地质学家和流体动力学家将同时使用户外流实验室，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.