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Basic reproduction number: number of infections caused on average by an infectious individual over entire infectious period: epidemiology: Body fat percentage: total mass of fat divided by total body mass, multiplied by 100: biology Kt/V: Kt/V: medicine (hemodialysis and peritoneal dialysis treatment; dimensionless time) Waist–hip ratio
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
The Stanton number (St), is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid. The Stanton number is named after Thomas Stanton (engineer) (1865–1931). [1] [2]: 476 It is used to characterize heat transfer in forced convection flows.
The Eckert number (Ec) is a dimensionless number used in continuum mechanics. It expresses the relationship between a flow's kinetic energy and the boundary layer enthalpy difference, and is used to characterize heat transfer dissipation. [1] It is named after Ernst R. G. Eckert. It is defined as
The third chart in each set was supplemented by Gröber in 1961, and this particular one shows the dimensionless heat transferred from the wall as a function of a dimensionless time variable. The vertical axis is a plot of Q / Q o , the ratio of actual heat transfer to the amount of total possible heat transfer before T = T ∞ .
A Graetz number of approximately 1000 or less is the point at which flow would be considered thermally fully developed. [ 2 ] When used in connection with mass transfer the Prandtl number is replaced by the Schmidt number , Sc, which expresses the ratio of the momentum diffusivity to the mass diffusivity.
The Reynolds and Womersley Numbers are also used to calculate the thicknesses of the boundary layers that can form from the fluid flow’s viscous effects. The Reynolds number is used to calculate the convective inertial boundary layer thickness that can form, and the Womersley number is used to calculate the transient inertial boundary thickness that can form.
Alternative forms of this number do exist depending on the approach by which Darcy's Law is made dimensionless and the geometry of the system. [2] The Darcy number is commonly used in heat transfer through porous media.