vanDriestDelta documentation - the default value of Cdelta

Hi,

Please see the two remarks below for vanDriestDelta implementation:

1. As can be seen in vanDriestDelta.C lines: [87-91], the van Driest function formulation (doi: 10.2514/8.3713, 1956) is slightly different from its original form. A minimum switch was introduced by de Villiers (http://bit.ly/1unTPaB, 2006) as shown in pages: [124, 260]. IMHO, it would be nice of you as well as useful to some users if his heuristic modification/work is noted and cited in the Extended Code Guide, which is currently absent.

2. In addition, vanDriestCoeffs's Cdelta is (most of the time) kept equal to 0.158 by default in the tutorials as can be found in tutorials/incompressible/pimpleFoam/LES/channel395DFSEM/constant/turbulenceProperties of v1712, for instance. However, as shown in de Villiers, the unnumbered equation in page 260, Cdelta is actually Cs. This may suggest, at least for channel395DFSEM tutorial, that Cdelta needs to equate Cdelta=Cs=0.065 rather than 0.158. Not sure if it is of practical importance though. Just an observation :)

Kind regards,