  In recent years, a number of authors have studied entropy generation in Wells
turbines. This is potentially a very interesting topic, as it can provide
important insights into the irreversibilities of the system, as well as a
methodology for identifying, and possibly minimizing, the main sources of loss.
Unfortunately, the approach used in these studies contains some crude
simplifications that lead to a severe underestimation of entropy generation
and, more importantly, to misleading conclusions.
  This paper contains a re-examination of the mechanisms for entropy generation
in fluid flow, with a particular emphasis on RANS equations. An appropriate
methodology for estimating entropy generation in isolated airfoils and Wells
turbines is presented. Results are verified for different flow conditions, and
a comparison with theoretical values is presented.
