Sand Transport under Irregular and Breaking Waves Conditions

用于海岸工程实践的数值地貌动力学模型系统由波浪、水流、泥沙运动和河床水位变化的耦合模型组成。输沙模型通常包括波浪平均悬浮泥沙的平流扩散模型和推移质或近床面总沙的实用输沙公式，其中输沙与局部水沙条件经验相关。有充分依据的实用模型是基于对净输沙率的测量和对关键基本过程的理解的组合，这些过程以参数化的方式被捕捉到模型中。然而，大多数实用模型是基于实验室实验中测量的传输速率和过程，这些实验几乎完全涉及规则的、不破碎的波。波浪实际上是不规则的，在许多(如果不是大多数)海岸工程中有实际意义的情况下都在破碎，这一事实提出了一个问题：为了使该模型适用于不规则和破碎波条件，在实际输沙模型中需要包括哪些与波浪不规则和波浪破碎相关的关键过程？拟议的研究有两个主要目的：(1)显著提高对大尺度不规则和破碎波条件下发生的近床流体动力学和输沙过程的理解；(2)开发一个新的实用模型来预测波浪下的输沙。以实验数据和对基本过程的理解为基础来解释波浪不规则性和波浪破碎。跨国项目团队包括阿伯丁大学、利物浦大学和特温特大学，并与英国和荷兰的行业项目伙伴合作。大型实验将在巴塞罗那的加泰罗尼亚理工大学的阿伯丁振荡流隧道和大型波浪水槽中进行。这些实验的物理理解和数据，结合两个基于过程的数值模型的见解，将被用来开发一种新的实用的输沙模型，该模型可以解释波浪不规则性和波浪破碎。与行业项目伙伴合作，新模型将在沿海工程从业者使用的地貌动力学建模系统中实施，并进行实际应用测试。

Numerical morphodynamic modelling systems used in coastal engineering practice consist of coupled models for waves, currents, sediment transport and bed level change. The sediment transport model usually comprises an advection-diffusion model for the wave-averaged suspended sediment and a practical sand transport formula for bed-load or near-bed total-load, in which the sand transport is empirically related to the local flow and sediment conditions. Well-founded practical models are based on a combination of measurements of net sand transport rates and understanding of the key fundamental processes, which are captured in the model in a parameterised way. However, most practical models are based on measured transport rates and processes from laboratory experiments involving regular, non-breaking waves almost exclusively. The fact that waves are in reality irregular and are breaking in many (if not most) cases of practical interest in coastal engineering, raises the question: what key processes associated with wave irregularity and wave breaking need to be included in a practical sand transport model for the model to be applicable to irregular and breaking wave conditions?The proposed research has two main aims: (1) To substantially improve understanding of the near-bed hydrodynamics and sand transport processes occurring under large-scale irregular and breaking wave conditions and (2) to develop a new practical model for predicting sand transport under waves, accounting for wave irregularity and wave breaking in a way that is well founded on experimental data and understanding of the fundamental processes. The transnational project team involves the Universities of Aberdeen, Liverpool and Twente in collaboration with UK and Dutch industry-based Project Partners. Large-scale experiments will be conducted in the Aberdeen Oscillatory Flow Tunnel and the Large Scale Wave Flume at the Catalonia University of Technology in Barcelona. Physical understanding and data from these experiments, combined with insights from two process-based numerical models, will be used to develop a new practical sand transport model that accounts for wave irregularity and wave breaking. Working with the industry Project Partners, the new model will be implemented in morphodynamic modelling systems used by coastal engineering practitioners and tested for practical applications.