Fundamentals of Fluid Dynamics - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 125

Fig. 5.15 Sublayers within a turbulent velocity boundary layer. Viscous sublayer occurs at y + <5.
Transition layer occurs between 5 < y + < 30 where turbulence production is maximum. Log layer is
between 30 < y + < 400. There is a law of the wake (not shown on graph) which occurs for y + > 400
Fig. 5.16 a Wall function approach where the near-wall region is modelled by a wall function.
b LRN approach using a fine near-wall mesh to capture the sharp changes in the flow parameters.
c An example of a hybrid mesh of the nostril inlet using inflation/prism layers for the LRN approach
adjacent cells to corresponding quantities at the wall. This relaxes the requirement
of a very fine mesh in the near-wall region, and leads to significant reduction in com-
putational resources, especially for high Reynolds number flows where the turbulent
boundary layer becomes very thin. There are a wide range of wall functions and its
implementation needs to concur with the near-wall mesh. For example some wall