Multi-dimensional Intra-wave Modelling of coupled Sediment transport and Turbulence (MIMST)

泥沙运动是海岸动力学的重要组成部分，它与许多物理、化学、生物和生态过程有关。计算机模拟方法是海岸带管理和预测海岸带系统对不断变化的环境条件的反应的重要工具。所使用的模型必须建立在对沉积物过程的良好物理理解基础上，并提供经过验证的预测能力。它们只能与潜在物理过程的表现一样好，这通常被归咎于沿海尺度物理模型的预测能力仍然有限。特别是，海床附近的混合极大地影响了物质的输运，对近海床湍流的良好描述对于准确描述沉积物输运至关重要。现有的证据表明，在沿海海洋模型中，对于波浪在波纹上的流动，近床湍流的预测仍然很差。接下来的关键问题是确定哪些过程导致了糟糕的预测，以及如何更好地表示它们。在MIMST项目中，我们建议使用计算机建模技术来显著增加我们对近床湍流和波纹床上沉积物运输的理解。我们将结合计算机模拟和与现有高质量实验数据的严格比较。这种方法将使我们能够开发并仔细验证一种新的波浪流体动力学、湍流和沉积物输运耦合模型。与目前的实验相比，由此产生的模型将能够提供更多关于小规模湍流和沉积物过程的信息。反过来，我们将使用新的精细尺度数值结果来评估和改进目前在海岸尺度模型中波纹床上近床湍流和沉积物运输的表征。通过结合观测和先进的数值模拟，该项目将为理解发生在海床附近的尚未解决的复杂物理过程提供坚实的科学基础。它可以更好地预测沿海地区对环境强迫变化的反应。该项目建立在波浪流体动力学和结构之间相互作用的研究之上，然后它将允许预测人造结构对沉积物动力学的影响，反之亦然。

The movement of sediment is a key part of coastal dynamics and it has relevance to many physical, chemical, biological and ecological processes. Computer modelling approaches are an important tool for coastal zone management and to predict the response of coastal systems to changing environmental conditions. The models used must be grounded in sound physical understanding of sediment processes and offer proven predictive abilities. They can only be as good as the representation of the underlying physical processes, which is commonly blamed for the still limited predictive power of coastal-scale physically-based models. In particular, mixing near the sea bed greatly affects the transport of matter and a good description of near-bed turbulence is crucial to accurately describe sediment transport. The available evidence shows that near-bed turbulence is still poorly predicted for wave flows over ripples in coastal ocean models. The key issues are then to determine which processes are responsible for the poor predictions, and how they can be better represented. In the MIMST project, we propose to use computer modelling techniques to significantly increase our understanding of near-bed turbulence and sediment transport over rippled beds. We will combine computer simulations with rigorous comparisons against existing high-quality experimental data. This approach will enable us to develop and carefully validate a new coupled wave hydrodynamics, turbulence, and sediment transport model. The resulting model will be able to provide more information on small-scale turbulent and sediment processes than experiments presently can. In turn, we will use the new fine-scale numerical results to assess and improve the current representation of near-bed turbulence and sediment transport over rippled beds in coastal-scale models. By combining observations and advanced numerical modelling, the project will provide a firm scientific foundation for understanding complex unresolved physical processes occurring near the sea bed. It will allow better predictions of coastal responses to changes in environmental forcing. The project builds on studies of the interaction between wave hydrodynamics and structures, and it will then allow predictions of the impact of man-made structures on sediment dynamics, and vice versa.