What is the relation between turbulence length scale used in ANSWER and the length scale used in standard turbulence models?
A definition of length scale used in in many turbulence models is: The definition used in ANSWER is: Here Cm is the viscosity constant (with a value of 0.09 for the standard turbulence model) and k is the von Karman constant (with a value of 0.4187). Thus with the standard set of k-e constants, we get: The reason for the use of the second definition is that it leads to a simple relation for estimating length scale close to a wall. From the log-law it can be shown that in the vicinity of a wall in the fully turbulent boundary layer: Where y is the distance from the wall. Therefore the length scale as defined above is simply equal to the distance from the wall in the vicinity of the wall.
