The bottom topography of ridged sea ice differs greatly from that of other sea-ice types. The form drag of ridge keels has an important influence on sea-ice drift and deformation. In this study, both laboratory experiment (LabE) and fluid dynamics numerical simulation (FDS) have been carried out for a physical ridge model in a tank to better understand the quantitative characteristics of the form drag. The LabEs covered both laminar and turbulent conditions. The local form drag coefficient of a keel, C_dw, varied with the keel depth h_w and the slope angle α_w in the turbulent regime. After validated by the LabE measurements, the FDSs were employed to extend the parameterization from the finite water depth to deep water. The results gave C_dw = 0.68∙ln (α_w/7.8°), R² = 0.998, 10° ≤  ≤ 90°, with C_dw ranging from 0.17 to 1.66, when the keel depth was much less than the water depth. For a large ridging intensity (keel depth/spacing ≥0.01), the variation of the local form drag coefficient and its contribution to total drag coefficient were sensitive to the keel slope angle. Assuming the log-normal distribution for this angle, the average value of the local form drag coefficient was 0.75, recommended for sea-ice dynamic models.

中文翻译：

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关于脊冰下的形式阻力系数：从理想尺度到深水的实验室实验和数值模拟

脊状海冰的底部地形与其他类型的海冰有很大不同。脊龙骨的形态阻力对海冰的漂移和变形有重要影响。在本研究中，对储罐中的物理脊模型进行了实验室实验 (LabE) 和流体动力学数值模拟 (FDS)，以更好地了解形状阻力的定量特性。LabEs 涵盖了层流和湍流条件。龙骨的局部形式阻力系数C _dw随龙骨深度h _w和倾斜角α _{w 变化}在动荡的政权中。经过 LabE 测量验证后，FDS 被用于将参数化从有限水深扩展到深水。结果给出C _dw  = 0.68∙ln ( α _w /7.8°), R ²  = 0.998, 10° ≤   ≤ 90° ，当龙骨深度远小于水深时，C _dw范围为 0.17 至 1.66。对于大的脊强度（龙骨深度/间距≥0.01），局部形式阻力系数的变化及其对总阻力系数的贡献对龙骨倾斜角敏感。假设这个角度的对数正态分布，局部形式阻力系数的平均值为 0.75，推荐用于海冰动力学模型。