Analysis of the unsteady surface pressure distribution of a pitching airfoil using modal decomposition

This work presents an exploratory attempt to understand how modal decomposition can be utilized for characterizing the behavior of the unsteady surface pressure distribution on a pitching airfoil. The unsteady aerodynamics of a thick airfoil geometry across a wide range of conditions were studied. Analyzing the pressure distributions across cases with different levels of flow separation yielded results that exhibited transitional behavior that encouraged modal analysis. The utility of the Proper Orthogonal Decomposition in capturing the distinct physical features of the unsteady pressure distribution was then evaluated. The first four global spatial modes extracted from surface pressure data resemble important and understandable attributes of the pressure distribution for an oscillating airfoil. The four-mode description sufficiently reconstructs the surface pressure data even for conditions with complex unsteady flow interactions. The resulting reconstructed pressure distributions can be used to approximate lift and moment coefficients with good accuracy. Graphic Abstract