The table shows the definitions of a lot of dimensionless quantities used in chemistry, fluid flow and physics engineering. Below the table, the symbols used in the formulas are explained and given with SI units.
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|Name||Symbol||Formula||Areas of application|
|Alfvén number||Al||Al = ν(ρ μ)½/B||Study of magnetic fields|
|Cowling number||Co||Co = B2 /(μ ρ ν2)||Study of magnetic fields|
|Euler number||Eu||Eu = Δp /(ρ ν2)||Characterization of energy losses in fluid flows|
|Fourier number||Fo||Fo = a t / l2||The ratio of diffusive or conductive heat transport rate to the heat storage rate|
|Fourier number for mass transfer||Fo*||Fo* = D t / l2||The ratio of diffusive mass transport rate to the mass storage rate|
|Froude number||Fr||Fr = ν /(l g)½||Determine the resistance of a partially submerged object moving through water|
|Grashof number||Gr||Gr = l3 g α ΔT ρ2 / η2||Study situations involving natural heat convection|
|Grashof number for mass transfer||Gr*||Gr* = l3 g (∂p/∂x)T,p (Δx p / η)||Predictions of mass flow patterns|
|Hartmann number||Ha||Ha = B l (κ/η)1/2||Describes the ratio of electromagnetic force to the viscous force|
|Knudsen number||Kn||Kn = λ / l||Determine whether statistical mechanics or the continuum mechanics formulation of fluid dynamics should be used to model a situation|
|Lewis number||Le||Le = a / D||Characterize fluid flows where there is simultaneous heat and mass transfer|
|Mach number||Ma||Ma = ν / c||Determine the approximation with which a flow can be treated as an incompressible flow|
|Nusselt number||Nu||Nu = h l / k||The ratio of convective to conductive heat transfer across (normal to) a boundary surface, predicts flow patterns.
|Nusselt number for mass transfer||Nu*||Nu* = kd l / D
||Predicts mass flow patterns|
|Peclet number||Pe||Pe = ν l / a||For transport phenomena in a continuum, the ratio of advective to diffusive heat transport rates, to decide the simplicity/complexity of computational models|
|Peclet number for mass transfer||Pe*||Pe* = ν l / D||The ratio of advective to diffusive mass transport rates|
|Prandtl number||Pr||Pr = η / (ρ a)||Determine the thermal conductivity of gases at high temperatures|
|Rayleigh number||Ra||Ra = l3 g α ΔT ρ /(η a)||Predict if heat transfer appear as conduction or convection|
|Reynolds number||Re||Re = p ν l / η||Predictions of fluid flow patterns|
|Magnetic Reynolds number||Rem||Rem = ν μ κ l||Estimates of the relative effects of advection or induction of a magnetic field|
|Schmidt number||Sc||Sc = η /(ρ D)||Characterization of fluid flows in which there are simultaneous momentum and mass diffusion convection processes|
|Stanton number||St||St = h /(ρ ν cp)||Characterization of heat transfer in forced convection flows, the ratio of heat transferred into a fluid to the thermal capacity of fluid|
|Stanton number for mass transfer||St*||St* = kd / ν||To characterize mass transfer in forced convection flows|
|Strouhal number||Sr||Sr = l f / ν||Describing oscillating flow mechanisms|
|Weber number||We||We = ρ ν2 l / γ||Analysing fluid flows where there is an interface between two different fluids|
ν = speed [m/s]
η = viscosity [kg/(m s)]
ρ = density, mass density, [kg/m3]
m = mass [kg]
V = volume [m3]
l = length [m]
a = thermal diffusivity [m2/s]
t = time [s]
μ = permeability [kg m/(s2A2)]
B = magnetic flux density [kg/(s2A)]
Δp = pressure difference [kg/(m s2)]
g = acceleration of free fall [m/s2]
α = cubic expansion coefficient [1/K]
ΔT = temperature difference
κ = electric conductivity [s3 A2/(kg m3)]
λ = mean free path [m]
D = diffusion coefficient [m2/s]
c = speed of sound [m/s]
h = coefficient of heat transfer [kg/(s3 K)]
k = thermal conductivity [kg m/(s3 K)]
cp = specific heat apacity at constant pressure [kg m2/(s2 K)]
f = frequency [1/s]
γ = surface tension [kg/s2]
x = mole fraction 
kd = mass transfer coefficient [m/s]
The SI-system, unit converters, physical constants, drawing scales and more.
Engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more.
Designation of large number in US vs. other countries.
Introduction to the Euler Number used in fluid mechanics.
Introduction to the Froude Number.
An introduction to the Mach Number.
Calculate square, cube, square root and cubic root. Values tabulated for numbers ranging 1 to 100.
A dimensionless number approximating the ratio of momentum diffusivity to thermal diffusivity.
Introduction and definition of the dimensionless Reynolds Number - online calculators.
Introduction to the Strouhal Number
Explanation of symbols used as subscripts or superscripts to tell more about the type of chemical reaction, process or condition.
Common thermodynamic terms and functions - potential energy, kinetic energy, thermal or internal energy, chemical energy, nuclear energy and more.
The Weber Number may be useful when analyzing fluid flows where there is an interface between two different fluids.