.TRANSFORM.Utilities.CharacteristicNumbers.KnudsenNumber

Information

Defined to be the ratio of the length scale between interactions divied by the characteristic length scale of the problem

• Kn = L_ms/L_char

If Kn is not << 1 then continuum theory breaks down and the calculus assumption to derive dT/dx as the lim dx -> 0 is not valid.

This limit may be reached in micro and nano-scale systems where L_char becomes small as well as in problems involving rarefied gas where L+ms becomes large.

Interface

function KnudsenNumber
  extends Modelica.Icons.Function;
  input SI.Length L_ms "Distance between energy carrier interactions";
  input SI.Length L_char "Length scale that characterizes the problem";
  output Units.NonDim Kn "Jakob number";
end KnudsenNumber;