Nonlinear waves in counter-current gas–liquid film flow
Nonlinear waves in counter-current gas–liquid film flow
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DOI：
10.1017/s002211201000618x
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发表时间：
2011-02
影响因子：
3.7
通讯作者：
D. Tseluiko;S. Kalliadasis
中科院分区：
文献类型：
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作者：
D. Tseluiko;S. Kalliadasis
研究了倾斜通道下壁在重力作用下，湍流气体在薄层流液膜上方流动时，液膜的动力学特性。描述气液两相流动的完整方程组的求解面临着严重的技术困难。然而，许多假设允许隔离气体问题，并通过将界面视为实心墙来独立解决它。这使得可以找到闭合形式的湍流气体施加在界面上的压力和切向应力的扰动。然后，我们分析了这些扰动对液膜流动的影响，导出了描述界面动力学的一系列模型方程，即边界层方程、长波模型和弱非线性模型，这就是由于湍流气体的存在而增加了一项的Kuramoto-Sivashinsky方程。这一附加项是分散和不稳定的(对于逆流情况；在同时情况下稳定)。我们还将长波近似与加权残值技术相结合，得到了对雷诺数较大值有效的积分边界层近似。然后，该模型被用来系统地研究在各种实验中观察到的泛滥现象：随着气体流量的增加，最初向下下降的膜开始向上运动，而就在波反转之前，波的幅度迅速增长。我们通过计算积分边界层近似下的周期行波来证实大振幅驻波的存在，并通过与时间相关的计算来证实我们的行波结果。
We investigate the dynamics of a thin laminar liquid film flowing under gravity down the lower wall of an inclined channel when turbulent gas flows above the film. The solution of the full system of equations describing the gas–liquid flow faces serious technical difficulties. However, a number of assumptions allow isolating the gas problem and solving it independently by treating the interface as a solid wall. This permits finding the perturbations to pressure and tangential stresses at the interface imposed by the turbulent gas in closed form. We then analyse the liquid film flow under the influence of these perturbations and derive a hierarchy of model equations describing the dynamics of the interface, i.e. boundary-layer equations, a long-wave model and a weakly nonlinear model, which turns out to be the Kuramoto–Sivashinsky equation with an additional term due to the presence of the turbulent gas. This additional term is dispersive and destabilising (for the counter-current case; stabilizing in the co-current case). We also combine the long-wave approximation with a weighted-residual technique to obtain an integral-boundary-layer approximation that is valid for moderately large values of the Reynolds number. This model is then used for a systematic investigation of the flooding phenomenon observed in various experiments: as the gas flow rate is increased, the initially downward-falling film starts to travel upwards while just before the wave reversal the amplitude of the waves grows rapidly. We confirm the existence of large-amplitude stationary waves by computing periodic travelling waves for the integral-boundary-layer approximation and we corroborate our travelling-wave results by time-dependent computations.