  Laminar-turbulent transitions occur at different Reynolds numbers for
different flow configurations and different fluids. In order to study
quantitatively the similarity among the transition processes of wall-bounded
shear flows, a uniform definition of transition parameter is required. The
transition parameters defined with properties of fluid element are compared and
discussed in terms of theoretical basis, physical definition, and expression,
and their application limitations in plane-Poiseuille flow, plane-Couette flow,
and Hagen-Poiseuille flow are clarified.
