A novel method for automatic transition prediction of flows over airfoils based on dynamic mode decomposition

Transition prediction is crucial for the simulation of steady and unsteady flows, since it can improve the accuracy of predicting the aerodynamic forces as well as capturing the flow phenomena. By combining dynamic mode decomposition (DMD) and e^N method, a novel transition prediction method for flows over airfoils is proposed. Compared with conventional linear stability-analysis-based e^N method, DMD requires neither the solution of boundary layer and linear stability equations, nor the assumption of parallel flows, and has better applicability in theory and is more algorithmically robust. Transition prediction of steady flows around NLF0416 and S809 airfoils and unsteady flow around SD7003 airfoil are carried out. The predicted transition locations are in reasonably good agreement with the experimental data and the results of e^N method based on linear stability analysis. It is shown that the proposed DMD/e^N method is feasible for transition prediction for steady and unsteady flows over airfoils, including the flows with laminar separation bubbles.