Péclet Number Calculator

This template provides two calculation for the Péclet number, one for mass transfer and one for heat transfer. Péclet number provides insight into whether advection or diffusion dominates the transport processes within a fluid flow.
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CalculatorsAccess the two subpages below for Péclet number describing  mass transfer or heat transfer.
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Péclet number (for mass transfer using Reynolds number)
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Péclet number (for heat transfer using Reynolds number)
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ExplanationPéclet number provides insight into whether advection or diffusion dominates the transport processes within a fluid flow. 
Mathematically it is expresses as:
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Pe=advection ratediffusion ratePe = \dfrac{\text{advection rate}}{\text{diffusion rate}}Pe=diffusion rateadvection rate​
Where:
Advection is the transport of a substance within a fluid by the motion of the fluid itself. The transported substance moves along with the fluid without mixing with the fluid. For example, take a river that is carrying leaves downstream, the leaves are being advected by the flow of water in the river. Advection is driven by the velocity field of the fluid, such as wind in the atmosphere or currents in the ocean. 
Diffusion is the movement of substances from regions of higher concentration to regions of lower concentration. It is driven by the random motion of particles within the fluid. Diffusion leads to the mixing of substances within a fluid. For example, a spray of perfume will get diffused into the air.
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Leaves advected by a river current
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Dye diffusing in water
Typically:
﻿﻿Pe≈0
 means diffusion is the dominant transport of the substance with negligible advection
﻿﻿Pe=1
 means advection and diffusion have the same effect on transport of the substance
﻿﻿Pe→∞
 means advection is the dominant transport of the substance with negligible diffusion
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, simpler computational models can be adopted when modelling certain situations with high Péclet numbers.
A flow will often have different Péclet numbers for heat and mass. This can lead to the phenomenon of double-diffusive convection.
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Related ResourcesBernoulli Mass Flow Rate Calculator
Froude Number Calculator: Open Channel Flow
Reynolds Number Calculator
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