Frazil-ice entrainment of sediment: large-tank laboratory experiments
Frazil-ice entrainment of sediment: large-tank laboratory experiments
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碎冰夹带沉积物：大型水箱实验室实验
DOI：
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发表时间：
2001
期刊：
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通讯作者：
L. Smedsrud
中科院分区：
文献类型：
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作者：
L. Smedsrud
模拟自然冰形成过程和泥沙夹带在浅水的实验室实验。在20 m长、1 m深的室内槽中用叶轮施加10-30 cm s-1的电流。水流中的湍流使0.5 m深度处的沉积物悬浮液浓度保持在10-20 mg L-1。低气温（10 - 15 ° C）和5 m s-1的风速导致向上的总热通量在140-260 W m-2范围内。冷却产生frazil冰晶直径达2厘米，浓度高达4.5克L - 1，在0.5米深。记录了时间尺度< 1分钟的相当大的时间变异性。一个接近恒定的部分较小的frazil晶体保持悬浮液。几个小时后，构成大部分冰体积的较大晶体在表面积累成雪泥。目前的测量被用来计算湍流耗散率，并估计的垂直扩散。5至8小时后，表层淤泥中的沉积物浓度通常接近于水中的沉积物浓度。然而，2 - 4小时后，它们高出2-4倍。数据表明，泥沙夹带取决于高的热通量和相应的高的碎冰生产率，以及足够强的湍流。波浪似乎不会显著增加泥沙夹带。
Laboratory experiments that simulate natural ice-formation processes and sediment entrainment in shallow water are presented. A 10-30 cm s -1 current was forced with impellers in a 20 m long, 1 m deep indoor tank. Turbulence in the flow maintained a suspension of sediments at concentrations of 10-20 mg L -1 at 0.5 m depth. Low air temperatures (∼-15°C) and 5 m s -1 winds resulted in total upward heat fluxes in the range 140-260 W m -2 . The cooling produced frazil-ice crystals up to 2 cm in diameter with concentrations up to 4.5 g L - 1 at 0.5 m depth. Considerable temporal variability with time-scales of < 1 min was documented. A close to constant portion of the smaller frazil crystals remained in suspension. After some hours the larger crystals, which made up most of the ice volume, accumulated as slush at the surface. Current measurements were used to calculate the turbulent dissipation rate, and estimates of vertical diffusion were derived. After 5-8 hours, sediment concentrations in the surface slush were normally close to those of the water. After 24 hours, however, they were 2-4 times higher. Data indicate that sediment entrainment depends on high heat fluxes and correspondingly high frazil-ice production rates, as well as sufficiently strong turbulence. Waves do not seem to increase sediment entrainment significantly.