Revisiting RANS prediction of transitional flow on T3A flat plate subject to various freestream turbulences

A laminar–turbulent transition subject to a freestream turbulence involves highly complex flow mechanisms, which have received considerable interest in the past decades. Accurately predicting such complex physical phenomena is significantly challenging using computational fluid dynamics solvers, particularly in industrial engineering applications. In this study, the capability of two transitional turbulence models—k-kl- ω and k-ω-γ-Reθt—to predict a T3A plate transition scenario was revisited. First, the predicted boundary layer data was compared to ERCOFTAC experimental measurements. Subsequently, a transitional flow subject to constant and sinusoidal freestream turbulences was systematically investigated. Under a constant freestream turbulence, the two models exhibited opposite tendencies of the transition starting and ending positions with the increase in Refst. However, there were still some similarities between the results of the two models. When the length scale was fixed, the transition area moved upstream with increasing turbulence intensity. The transition zone was more sensitive to a small length scale than to a considerable length scale. The dynamic boundary layer under the sinusoidal combination condition was less disturbed than the sinusoidal turbulence intensity and the sinusoidal specific turbulence dissipation rate. Regardless of the type of sinusoidal freestream turbulence the boundary layer was exposed to, increasing the oscillation frequency significantly disturbed the transitional flow. It was observed that the inertia effect of the dynamic onset point was enhanced by increasing the oscillation frequency. Concurrently, a significant phase delay occurred, and the delay time was approximately proportional to the oscillation frequency. The extreme position of the transition onset close to the leading edge of the plate was not affected by the oscillation frequency, whereas it depended on the sinusoidal variable. However, the extreme downstream transition onset point was significantly affected by the oscillation frequency