Abstract We investigate isothermal continuous gravity currents down on an incline of 5 ° . The front region with strong mixing and the shallower layer behind it are modelled using computational fluid dynamics in order to discuss the dilution process in accidental releases. The simulations were performed using two different customised packages for compressible and a non-compressible flows. The heavy fluid dilution was analysed considering RANS (Reynolds Average Navier Stokes) approach and three turbulence models k − e , k − ω SST and RNG k − e . The simulated gravity currents were compared with experimental by means of the density distribution in the flow and volume of the current. As far as dense gas cloud prediction is concerned, the numerical findings agree with the experimental data and there seems to be good indication that the solvers are suitable for consequence analysis. Shear instabilities caused by the flow of two fluids near the interface zone are well captured by RNG k − e turbulence model. The simulations show that the modelling of small scale turbulence and associated rate of deformation are important to mimic the wavy instabilities and curling of the interface region of the released and ambient fluid. Such process is of paramount importance when predicting the mixing and dilution of the released material. Analysis of the results shows that better agreement is observed when the proper modelling of the shear instabilities is considered as well as the extra source of turbulence due to the effects of buoyancy.

中文翻译：

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倾斜平面上的分层流动和相关的剪切不稳定性建模

摘要 我们研究了倾斜 5° 的等温连续重力流。使用计算流体动力学对具有强烈混合的前部区域和其后的较浅层进行建模，以讨论意外释放中的稀释过程。模拟是使用两种不同的定制包进行的，可压缩和不可压缩的流动。考虑到 RANS（雷诺平均纳维斯托克斯）方法和三个湍流模型 k - e 、k - ω SST 和 RNG k - e 来分析重质流体稀释。通过电流的流动和体积的密度分布将模拟的重力流与实验进行比较。就密集气体云预测而言，数值结果与实验数据一致，似乎有很好的迹象表明求解器适用于后果分析。RNG k - e 湍流模型很好地捕捉了由界面区附近的两种流体流动引起的剪切不稳定性。模拟表明，小尺度湍流和相关变形率的建模对于模拟释放和周围流体的界面区域的波浪不稳定性和卷曲很重要。在预测释放材料的混合和稀释时，该过程至关重要。结果分析表明，当考虑剪切不稳定性的适当建模以及由于浮力影响而产生的额外湍流源时，观察到更好的一致性。RNG k - e 湍流模型很好地捕捉了由界面区附近的两种流体流动引起的剪切不稳定性。模拟表明，小尺度湍流和相关变形率的建模对于模拟释放和周围流体的界面区域的波浪不稳定性和卷曲很重要。在预测释放材料的混合和稀释时，该过程至关重要。结果分析表明，当考虑剪切不稳定性的适当建模以及由于浮力影响而产生的额外湍流源时，观察到更好的一致性。RNG k - e 湍流模型很好地捕捉了由界面区附近的两种流体流动引起的剪切不稳定性。模拟表明，小尺度湍流和相关变形率的建模对于模拟释放的流体和环境流体的界面区域的波浪不稳定性和卷曲非常重要。在预测释放材料的混合和稀释时，该过程至关重要。结果分析表明，当考虑剪切不稳定性的适当建模以及由于浮力影响而产生的额外湍流源时，观察到更好的一致性。模拟表明，小尺度湍流和相关变形率的建模对于模拟释放的流体和环境流体的界面区域的波浪不稳定性和卷曲非常重要。在预测释放材料的混合和稀释时，该过程至关重要。结果分析表明，当考虑剪切不稳定性的适当建模以及由于浮力影响而产生的额外湍流源时，观察到更好的一致性。模拟表明，小尺度湍流和相关变形率的建模对于模拟释放和周围流体的界面区域的波浪不稳定性和卷曲很重要。在预测释放材料的混合和稀释时，该过程至关重要。结果分析表明，当考虑剪切不稳定性的适当建模以及由于浮力影响而产生的额外湍流源时，观察到更好的一致性。