Richardson number
The Richardson number is a dimensionless parameter. It is named after the British mathematician and meteorologist Lewis Fry Richardson (1881-1953) and describes the fluid dynamics of the relationship between potential and kinetic energy.
The definition varies depending on the application. For liquids or gases in a gravitational field, one can define, for example,
With the gravitational acceleration g, a typical length scale of the problem h (in the direction of the gravitational field ) and a typical velocity u in flight operations is the Richardson number, for example, indications of whether turbulence occurs - at typical values of Ri from 10 to 0.1 the smaller Ri, the more likely turbulence.
In this definition, the reciprocal of the square root of the Richardson number is also called Froude number.
In problems with thermal convection, the following definition is used:
Where g is the acceleration due to the gravitational field, the coefficient of expansion, the temperature of the heated wall, a reference temperature, a typical length of the problem, and a typical velocity.
This definition can with the Grashof number Gr and the Reynolds number Re and
Be written. Natural convection is negligible, forced convection is negligible. In between the both must be considered.
Example of use
In particular, in the design of heat storing the Richardson number is used to dimension an ordinary temperature stratification in the tank. The inflow into the reservoir must therefore be designed so that the incoming pulse does not destroy the tank stratification.
End of 2007, Europe's largest district heating store with over 2 million kWh of storage capacity in the power plant of EVN AG Tisza was put into operation. It has a diameter of 50 meters and a height of just over 20 meters. Despite these unfavorable conditions geometrically actually he has a perfect temperature stratification. In this memory, the input and Ausströmungsvorgänge were calculated by means of the Richardson number and the input and Ausströmimpulse were adjusted accordingly.
Swell
- Code ( Fluid Mechanics )