Consolidating Data for Boundary Layer Transition Onset Under the Influence of Freestream Turbulence and Pressure Gradients

Abstract Laminar-turbulent transition in boundary layers is important to turbomachinery flows. Accurate prediction of the boundary layer state is necessary when calculating entropy generation and heat transfer rates on blades and end walls. Current practice uses a mix of empirical correlations, experimental testing, and the experience of the designer to account for transition; however, in complex flows at the decreasing Reynolds numbers found in modern machines, prior knowledge is insufficient. As such, there remains a need for correlations that can be fed into low-order methods for routine use in design. Many such correlations are available; however, the data they are based on are limited, particularly for flows with strong pressure gradients and high freestream turbulence such as those found in turbomachinery. This work consolidates existing literature data for boundary layer transition onset under the influence of freestream turbulence and pressure gradients. Details of the methods used in the original studies are discussed. Data are compared to existing correlations and areas with insufficient data are identified, along with suggestions for future work to fill gaps in the literature.