Sensitivity analysis and modeling uncertainties quantification for impinging-film cooling via active subspaces

Within the context of exploiting efficient cooling methods for advanced gas turbine combustors, understanding the fundamental physics for impinging-film cooling under various operational conditions is of significance. In this paper, impacts of different interaction modes between coolant and hot mainstream on the impinging-film cooling are quantitatively evaluated via active subspace (AS) method. Three interaction modes are considered, i.e., a transitional flow (TF), a turbulent boundary layer (TBL) and a wall jet (WJ). Sensitivities and uncertainties of cooling effectiveness η with respect to coolant mass flow rate Mc and model parameters (Cμ,CΕ1,CΕ2,Prtw) are estimated. Results show that 1-D active subspaces are sufficient to map η in TF and TBL modes while high-dimensional active subspaces are warranted for WJ mode, indicating its more complicated interaction between cold and hot flows. η is the most sensitive to and dominated by Mc especially in the slot and far fields, and turbulent effects are more significant in the near field than other places. Specifically, an increase in Mc or a decrease in turbulent level monotonously improves η in TF and TBL modes while initially increases η then reduces it for WJ mode. Further analysis of flow characteristics of WJ mode demonstrates that the reduction in η results from the strengthened impingement-induced streamwise vortexes and thereby, enhanced mixing between the coolant and mainstream. The propagation of the input uncertainty to η is space- and operational condition-dependent, consistent with the evolution of active subspaces. © 2025 Elsevier Ltd