A note on constraints in turbulence modelling

We show that the class of constitutive relations for turbulence models put forward by Wang (1997) in this journal conflicts with dimensional analysis, unless the turbulent Reynolds stresses were to be tied to the molecular vi scous stresses everywhere in the flow. We then reiterate, using counter-exa mples, that the controversial postulate of material frame-indifference is u nfounded for turbulence, and is counter-productive in the quest for accurac y. We add a comment on the role of acceleration.