Plan view: For , advection is negligible, and diffusion dominates mass transport.
For mass transfer, it is defined as:
Plan view: For , diffusion and advection occur over equal times, and both have a not negligible influence on mass transport.
Such ratio can also be re-written in terms of times, as a ratio between the characteristic temporal intervals of the system:
For the diffusion happens in a much longer time compared to the advection, and therefore the latter of the two phenomena predominates in the mass transport.
Plan view: For , diffusion is negligible, and advection dominates mass transport.
In engineering applications the Péclet number is often very large. In such situations, the dependency of the flow upon downstream locations is diminished, and variables in the flow tend to become 'one-way' properties. Thus, when modelling certain situations with high Péclet numbers, simpler computational models can be adopted.[1]
A flow will often have different Péclet numbers for heat and mass. This can lead to the phenomenon of double diffusive convection.
In the context of particulate motion the Péclet number has also been called Brenner number, with symbol Br, in honour of Howard Brenner.[2]
The Péclet number also finds applications beyond transport phenomena, as a general measure for the relative importance of the random fluctuations and of the systematic average behavior in mesoscopic systems
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