The effect of unsteady turbulent flows on mass transfer in aquatic environments

提出的研究计划的目标是利用实验、实地和计算方法相结合的方法来检查质量运输在基本生物地球化学和生态过程中的作用。具体来说，我将研究湍流对水生系统中底栖动物（沉积物、大型植物、双壳类）的营养吸收、悬浮摄食/颗粒命运和颗粒通量的影响。在此过程中，除了平均流动条件对这些过程的影响外，我还将研究非定常流的作用——包括导致生物体振荡的流体-结构相互作用。我的具体目标是调查/确定：(1)流体与大型植物的相互作用，以及湍流诱导的植物运动如何通过将溶解的无机碳运输和吸收到发生营养吸收的叶片表面来影响大型植物的生产力；(2)颗粒（包括生物颗粒）在以淡水贻贝为食的悬浮层中运移的命运；(3)收集器运动对粒子捕获的影响，粒子捕获是必不可少的质量传递机制。实现这些目标直接关系到更好地了解水生环境的生产力和功能。

The objectives of the proposed research program are to examine the role of mass transport on fundamental biogeochemical and ecological processes using a combination of experimental, field, and computational approaches. Specifically, I will examine the influence of turbulence on nutrient uptake, suspension feeding/particle fate, and particle flux that occur in the benthos (sediments, macrophytes, bivalves) of aquatic systems. In doing so, I will examine the role of unsteady flow - including the fluid-structure interactions that cause organisms to oscillate - in addition to the influence of mean flow conditions on these processes. My specific objectives are to investigate/determine the: (1) fluid-macrophyte interactions and how turbulence-induced plant movements affect macrophyte productivity through the transport and uptake of dissolved inorganic carbon to the leaf surface where nutrient uptake occurs; (2) fate of particles (including biological ones) transported through beds of suspension feeding freshwater mussels; and (3) the effect of collector motion on particle capture, which is an essential mass transport mechanism. The fulfillment of these objectives relates directly to a better understanding of the productivity and function of aquatic environments. As an empiricist, I operate within a theoretical framework set by the fluid dynamics and modified by the specific attributes of the organism/system under study. This allows me to establish hypotheses based on existing physical theory and to examine whether ecological/biogeochemical processes conform to the expectations of that theory. In this way, it is possible to draw broader conclusions and further the development of theories of organism-environmental interactions. This often requires the use of a simplification, such as restricting the movement/geometry of an organism and using steady flow conditions, to ensure that conditions conform to the physical model (e.g. leaves of a plant must be flat and parallel to the flow direction to examine mass transport using the flat plate analogy). By incorporating unsteady flow conditions, including flow-induced interactions, I will be able to advance our understanding of biogeochemical/ecological response to hydrodynamics forcing. The results of this research program will facilitate the development of novel models of the unsteady conditions found in nature, which will inform scientists, engineers, and managers. There are direct implications for the fate/transport of contaminants, which are influenced if not dominated by surface phenomena. The results will also be used to address/mitigate the impacts of human activities on habitat and on water quality.