Quantification of parametric uncertainty in c-Reh model for typical flat plate and airfoil transitional flows

Owing to the lack of physical knowledge of boundary layer transition, the y-Reo transi-tion model introduces closure parameters, which increase the uncertainty of transition prediction. The objective of this work is to quantify the uncertainties of closure parameters in the quantities of interests and identify the key parameters. The six closure parameters in the uncertainty intervals are used as input variables, and the uncertainties of the output results are propagated by a stochas-tic expansion based on the point-collocation nonintrusive polynomial chaos method. The relative contribution of each parameter to uncertainty is evaluated by the Sobol index. The computational cases include natural and bypass transitional flows on zero-pressure-gradient flat plates, and sub-sonic and transonic flows around airfoils. For most cases, ce2, ca2, and ca1 dominate the uncertainty, and the influence of aot is also significant when the history effects of flow are evident. The contri-bution of parameters in airfoils is more complex than that in flat plates. The transonic airfoil case shows that flow separation dramatically changes the distribution of Sobol indices, which poses a challenge to the accurate prediction of transition. Generally, ce2 and ca2 are the key parameters of the y-Reo model. (c) 2022 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Due to the lack of physical knowledge of boundary layer transition, the y-Reo transition model introduces closure parameters, which increase the uncertainty of transition prediction. This work quantifies the uncertainties of closure parameters in the quantities of interests and identifies the key parameters. The relative contribution of each parameter to uncertainty is evaluated by the Sobol index. The results show that ce2 and ca2 are the key parameters of the y-Reo model.