Surface Tracking Map: oil separation and droplet formation of a simulated oil-plume discharging from the ocean floor.

An in-house second order accurate finite-volume code “Chem3D” is used for simulation. The domain of interest is a rectangular box representing the ocean body with an oil-plume discharge at the bottom. The oil trajectory is identified via a multi-block surface tracking algorithm. An unstructured triangular mesh is identified as the oil-water interface, where as the bulk fluid is discretized using multi-block Cartesian cells. At each time step, the interface is advanced, and since it deforms in time, the interface mesh has to be regenerated. However, this approach provides a natural pathway to including surface tension and surface chemistry effects. Droplet breakoff is represented by a model, and separated droplets/bubbles are tracked individually. This method gives an approach towards accurate mapping of the oil separation and droplet formation effects. The velocity field data set provides geometrical coordinates used for modeling, velocity field, pressure field, flag indicator determining which volumetric grid contains the surface and phase indicator determining the different phases of the fluid. The data set is unsteady data set with ten timesteps which amounts to 1 second of physical time. The surface coordinates data set provides the evolution of the surface as the coordinates of the surface at each time step. Figure 1 shows the velocity contour at the final timestep at the symmetry plane. Figure 2 shows the tracked surface at the final timestep.本研究采用自主研发的二阶精度有限体积法（finite-volume）代码"Chem3D"开展数值模拟。计算域为表征海洋水体的矩形箱体，其底部设置油羽流排放源。采用多块曲面追踪算法识别油相运动轨迹：油-水界面采用非结构化三角网格离散，而主体流场则通过多块笛卡尔网格进行离散。每一时间步长下均需更新界面，由于界面随时间发生形变，因此需对界面网格进行重构。不过该方法可自然引入表面张力与表面化学效应。通过模型表征液滴断裂过程，并对分离出的液滴/气泡进行单独追踪。该方法可实现油相分离与液滴形成过程的精准刻画。本速度场数据集包含建模所需的几何坐标、速度场、压力场、用于标识体网格是否包含界面的标记指标，以及用于区分流体不同相态的相场指标。该数据集为非定常数据集，共包含10个时间步，对应物理时长1秒。界面坐标数据集则给出各时间步下的界面坐标，以完整表征界面演化过程。图1展示了对称平面处最终时间步的速度云图。图2展示了最终时间步下的追踪界面。