Scaling behavior for the onset of convection in a colloidal suspension.
Scaling behavior for the onset of convection in a colloidal suspension.
复制标题
胶体悬浮液中对流开始时的缩放行为。
DOI：
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发表时间：
2005
影响因子：
8.6
通讯作者：
M. Giglio
中科院分区：
文献类型：
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作者：
R. Cerbino;S. Mazzoni;A. Vailati;M. Giglio
我们研究了高溶质瑞利数Ras时胶体悬浮液中质量对流的早期阶段。从阴影图像的时间演变和假设边界层的扩散增长，我们得到了对流开始时浓度边界层厚度delta*的间接测量。我们发现，无量纲边界层厚度delta=delta*/d的尺度为Ra-ps，其中Ras=Rasdelta是对流的修正溶质瑞利数，它解释了实际密度不平衡，d是样品层的厚度。这种标度行为类似于简单流体中湍流对流稳态时的标度行为。我们发现稳态下简单流体湍流热对流的p=0.35，一个与指数1/3相容的值。
We investigate the early stages of mass convection in a colloidal suspension at high solutal Rayleigh number Ras. From the time evolution of shadowgraph images and by assuming a diffusive growth of the boundary layers we obtain an indirect measurement of the concentration boundary layer thickness delta* at the onset of convection. We show that the dimensionless boundary layer thickness delta=delta*/d scales as Ra-ps, where Ras=Rasdelta is a modified solutal Rayleigh number for convection which accounts for the actual density unbalance and d is the thickness of the sample layer. This scaling behavior is analogous to that reported at steady state for turbulent convection in simple fluids. We find p=0.35, a value compatible with the exponent 1/3, reported for turbulent heat convection in simple fluids at steady state.