The impact of mesh adaptivity on the gravity current front speed in a two-dimensional lock-exchange
The impact of mesh adaptivity on the gravity current front speed in a two-dimensional lock-exchange
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DOI：
10.1016/j.ocemod.2011.01.003
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发表时间：
2011
期刊：
影响因子：
3.2
通讯作者：
H. Hiester;M. Piggott;P. Allison
中科院分区：
文献类型：
--
作者：
H. Hiester;M. Piggott;P. Allison
对二维锁交换流动的数值模拟被用来评估在非静力有限元模型FLONIDITY-ICOM中实现的自适应网格的性能。船闸交换是一个被广泛研究的实验室规模的装置，它产生两个水平传播的重力流，并包括与包括海洋溢出在内的许多尺度上的重力流有关的关键物理过程。采用弗劳德数(无量纲前沿速度)对固定结构网格、固定非结构网格和自适应非结构网格进行了数值模拟，并对不同的自适应网格结构进行了比较。流动性-国际博协成功地捕捉到了流动的动力学，包括开尔文-亥姆霍兹波流的发展。网格自适应由一个度量来指导，该度量是自适应网格表示流的能力的关键。基于解字段的曲率和用户定义的解字段权重，FLOBIDITY-ICOM中使用的度量很简单。重力流前沿区域的良好表示对解的质量至关重要，而对于自适应网格，这是通过降低边界附近的水平速度场权重来实现的。以这种方式配置的自适应网格的性能与高分辨率固定网格一样好，同时使用的节点至少少一个数量级。弗劳德数也与之前公布的由实验、数值和理论方法确定的值进行了很好的比较。自适应网格使用的节点数的大幅减少特别令人鼓舞，因为这表明在三维模拟和更大规模的问题中可能获得更大的收益。结果表明，采用的自适应网格方法的成功使用需要清楚地理解系统的物理和度量。这些考虑对于自适应网格方法在更复杂的海洋流动的数值模拟中的有效应用至关重要。
Numerical simulations of the two-dimensional lock-exchange flow are used to evaluate the performance of adaptive meshes as implemented in the non-hydrostatic, finite-element model Fluidity-ICOM. The lock-exchange is a widely studied laboratory-scale set up that produces two horizontally propagating gravity currents and incorporates key physical processes associated with gravity currents over many scales including ocean overflows. The Froude number (non-dimensional front speed) is used to assess simulations performed on fixed-structured, fixed-unstructured and adaptive-unstructured meshes and different adaptive mesh configurations are compared. Fluidity-ICOM successfully captures the flow dynamics, including the development of Kelvin–Helmholtz billows. Mesh adapts are guided by a metric which is key to the ability of an adaptive mesh to represent the flow. The metric employed in Fluidity-ICOM is simple, based on the curvature of the solution fields and user-defined solution field weights. Good representation of the gravity current front region is essential to the quality of the solution and for the adaptive meshes this is achieved by reducing the horizontal velocity field weight near the boundaries. Adaptive meshes that are configured in this way are seen to perform as well as high-resolution fixed meshes whilst using at least one order of magnitude fewer nodes. The Froude numbers also compare well with previously published values determined from experimental, numerical and theoretical approaches. The substantial reduction in the number of nodes used by the adaptive meshes is particularly encouraging as it suggests that even greater gains may be achieved in three-dimensional simulations and larger-scale problems. Results show that successful use of the adaptive mesh approach employed requires a clear understanding of the physics of the system and the metric. These considerations will be vital to the effective application of adaptive mesh approaches in numerical modelling of more complex ocean flows.