Characterizing the onset of dynamic stall using a vorticity-based criterion

Iowa State University

The objective is to characterize the onset of stall over airfoils undergoing unsteady maneuvers. Based on analysis of large-eddy simulation results, a fundamental, vorticity-based parameter, namely, the boundary enstrophy flux (BEF), was identified to signal imminent vortex formation in the incompressible regime. Extension to the compressible regime and identifying scaling parameters for the criterion are underway.

Characterizing precipitation over onshore and offshore sites in the US

Pacific Northwest National Laboratory

The goal of the project was to improve estimates of precipitation-induced leading edge erosion of wind turbine blades. Precipitation patterns over onshore and offshore sites in the US were characterized using large datasets of historical disdrometer data, for use in leading edge erosion prediction models.

Data-driven, reduced-order models for dynamic stall

Iowa State University

Explored modal decomposition techniques such as dynamic mode decomposition (DMD) and non-stationary spectral analysis using wavelet transforms (WT) to identify distinguishing behavior around dynamic stall onset for moderate Reynolds numbers (~O(10^5)). DMD yielded unstable eigenvalues both within and outside the stall onset regime. WT indicated the presence of energetic, small-scale structures, whose time of incidence varied relative to the stall onset regime for different cases with no observable trend.

Criterion for vortex breakdown in swirling flows

Indian Institute of Science

Vortex breakdown in swirling flows was studied through direct numerical simulations (DNS) of a closed cylinder with one rotating lid configuration. An in-house DNS code was modified for use with cylindrical coordinates. A helicity-based criterion representing vortex line linkages was proposed to characterize vortex breakdown.