Negative Normal Components in UPrime2Mean Patch Fields - channel395DFSEM

Hi,

Problem: I observed negative values in the normal components of UPrime2Mean, e.g. u'u', on patch fields (not internal fields) in a tutorial as well as in-house case. These components, however, are by definition positive.

MWE: Please run OpenFOAM-v1712/channel395DFSEM tutorial with UPrime2Mean on. For an arbitrary instant of solution, executing

postProcess -func minMaxComponents'(UPrime2Mean)' -latestTime yields:

...
Executing functionObjects
fieldMinMax minMaxComponents(UPrime2Mean) write:
    min(UPrime2Mean) = (-110.6187451010895 -71.67069008796911 -57.02833388170411 -15.05621144511252 -12.23325724312694 -8.60988994091587) in cell 17517 at location (0 1.869010129293147 3.122436600824001)
    max(UPrime2Mean) = (6.906486416596863 1.071684114359736 0.9375168777607903 0.7322488089670033 0.1589319170416081 1.301374985649687) in cell 1529601 at location (50.83096913508285 1.891711244092694 0.3256528970184543)
...

As can be seen, negative values appear in the UPrime2Mean normal components. Manual inspection showed me that these negative values exist in patch fields, rather than internal fields.

Kind regards,