The transition region plays a critical role in the design of turbine blades, as it is accompanied by higher losses (1) and higher heat transfer rates (2). Most of the transition onset and length correlations have been developed from incompressible measurements with only a limited number of investigators addressing the effect of Mach number. Narasimha (3) investigates the $Reθ(ST)$ and concludes that it increases with Mach number; thereby delaying transition onset. In contrast, Schook et al. (4) found the $Reθ(ST)$ from compressible measurements to be consistently lower than that correlated by Mayle (5) for the incompressible range. Thus the experimental evidence is contradictory.

Dey and Narasimha (6) suggest a variation in the spot formation rate with no change up to a Mach number of 2, which would suggest that the...