ENH: New wallfunction blending approaches
Summary
This merge request is a discussion placeholder for two topics:
Potential improvements to the wallfunction hierarchies Wallfunction blending treatments between viscous and inertial sublayers
Wallfunction hierarchy
Arguably, the wallfunction hierarchies need a reexamination as the relations have "grown organically" in the course of time. One recent problem is that {omega,epsilon,k}Wall
functions use data members from nutWallFunction
base class even though the former group is not derived from the latter.
One practical consequence is that {omega,epsilon,k}Wall
always require a nut
wall function is defined in the nut
dictionary, otherwise simulation in question noisily fails without informing the user with useful information, e.g. CFDOnline:Error with komega SST and simpleFoam (21Feb20), and the bugfix:55776069.
Wallblending treatments

Four wallfunction blending treatments were introduced:
STEPWISE
MAX
BINOMIAL
EXPONENTIAL

.. For the following wall functions:
epsilonWallFunction
omegaWallFunction
nut{k,U}WallFunction

The headerfile documentations were improved for the following wall functions for which the blending treatments were not applicable (e.g. due to the continuous treatment in
nutUSpaldingWallFunction
):nutU{Spalding,Tabulated,Blended}WallFunction
nut{k,U}RoughWallFunction
nutLowReWallFunction
{kLowRe,kqR}WallFunction

Based on:
 Viegas and Rubesin (1983); Viegas et al. (1985) (i.e. the option:
STEPWISE
)  Menter and Esch (2001) (i.e. the option:
BINOMIAL
)  Popovac and Hanjalić (2007) (i.e. the options:
MAX
,EXPONENTIAL
)  Knopp et al. (2006) (i.e. the option:
TANH
only foromega
)
 Viegas and Rubesin (1983); Viegas et al. (1985) (i.e. the option:
Resolved bugs
N/A
Risks
High risk, yet bitwise backward compatibility, and regression were verified for each modified functionality.