# Richardson Number - related to Reynolds number

## Description

The Richardson number (Ri) is named after Lewis Fry Richardson (1881 – 1953). It is the dimensionless number that expresses the ratio of potential to kinetic energy. In certain fields the Froude number is more commonly used and is the reciprocal of the square root of the Richardson number or Ri = 1/Fr^2

The Richardson number can also be expressed by using a combination of the Grashof number and Reynolds number.

Typically, the natural convection is negligible when Ri < 0.1, forced convection is negligible when Ri > 10, and neither is negligible when 0.1 < Ri < 10. It may be noted that usually the forced convection is large relative to natural convection except in the case of extremely low forced flow velocities. In the design of water filled thermal energy storage tanks, the Richardson number can be useful.

## Variables

Ri | Richardson number (dimensionless) |

Gr | Grashof number (dimensionless) |

Re | Reynolds number (dimensionless) |