Peclet

Peclet is a surname of French origin. In science and engineering, it is associated most prominently with the Péclet number, a dimensionless quantity used to characterize transport processes in which advection competes with diffusion.

In mass transfer, the Péclet number is defined as Pe = UL/D, where U is a characteristic velocity, L a characteristic length, and D the molecular diffusion coefficient. In heat transfer, Pe = UL/α, where α is the thermal diffusivity (α = k/(ρ c_p)). In momentum transport, Pe can be written as Pe = UL/ν, and is related to Reynolds and Prandtl or Schmidt numbers through Pe = Re·Sc or Pe = Re·Pr, depending on the transport being considered.

Interpretation: A large Pe indicates that advection dominates the transport process; a small Pe indicates diffusion dominates. The value around unity marks a balance between mechanisms. The concept is widely used to nondimensionalize the convection–diffusion equation and to compare transport rates in different systems.

Applications span chemical engineering, environmental engineering, microfluidics, heat exchanger design, groundwater hydrology, atmospheric and oceanic flows, and chromatography. It also informs scale-up and modeling choices when simulating transport phenomena.

Origin: The term is named after a 19th-century French scientist who studied advection and diffusion in transport problems; the surname appears in various spellings, including Péclet and Peclet.

See also: convection–diffusion equation, Reynolds number, Schmidt number, Prandtl number.