Flow and transport at an interface between a turbulent flow and a porous medium

本文研究了多孔介质/湍流界面上的交换过程。我们集中研究了河流地表水和地下水混合的潜流带的流动和传质。该带对地表水的生态功能有重要贡献。我们打算在不同雷诺数下对由随机填充球体组成的多孔床上的湍流进行直接数值模拟。在这些模拟中，孔隙空间将被分解。我们涵盖了从平滑到完全粗糙的湍流状态的范围。模拟将在最近发表的实验数据的帮助下进行验证，这些数据来自使用最先进的实验技术的实验，从而提供湍流量的详细测量。我们扩展了实验中可用的雷诺数范围，并对界面上的传质进行了额外的模拟。这将使我们能够通过采用双平均方法提供湍流动量和质量输运的详细信息。后者将用于区分由最上层（布林克曼）层时间平均流引起的输运和由湍流波动引起的输运。我们希望这些模拟将提供重要的信息，有助于模拟质量和动量传递在潜流区，适用于其他界面之间的多孔介质和湍流。

This proposal deals with the exchange processes at a porous media/turbulent flow interface. We concentrate on the flow and mass transfer in the hyporheic zone in which streamborne surface waters and subsurface waters mix. This zone has a significant contribution to the ecological functioning of surface waters. We intend to perform Direct Numerical Simulations of the turbulent flow over a porous bed consisting of randomly packed spheres at various Reynolds numbers. In these simulations the pore space will be resolved. We cover the range from smooth to fully rough turbulent regimes. The simulations shall be validated with the help of recently published data from an experiment using state-of-the art experimental techniques thus providing detailed measurements of turbulent flow quantities. We extend the range of Reynolds numbers available from the experiment and perform additional simulations of the mass transfer over the interface. This will enable us to provide detailed information of turbulent momentum and mass transport by adopting a double-averaged approach. The latter will be used to distinguish between transport due to the time-averaged flow in the upper-most (Brinkman) layer and transport due to turbulent fluctuations. We hope that these simulations will provide essential information helpful for modelling mass and momentum transfer in the hyporheic zone that is applicable to other interfaces between porous media and turbulent flows.