ABSTRACT: Unsteady fluid flows often exhibit symmetries that manifest spatially and temporally. Interestingly, many flows that are expected to be symmetric can turn out to be asymmetric. Such breaking in symmetry can result in undesirable impacts on engineering systems, but it can also be manipulated and leveraged to improve their performances. In this talk, we will discuss our recent attempts of explaining and exploiting the development of spatial-temporal asymmetries in unsteady wake flows. We will first understand the development of spanwise flow asymmetries over a symmetric finite-span wing via the phase interference between symmetric and anti-symmetric modes, through the lens of eigenvalue/structural sensitivity and spatial-temporal harmonic resolvent analyses. Next, we will break the temporal symmetry of a periodic-shedding cylinder wake by a time-varying external forcing that follows a chaotic time series to characterize the generalized synchronization between the two nonlinear systems and its use for physical reservoir computing.

BIOSKETCH: Chi-An Yeh is an Assistant Professor in the Department of Mechanical and Aerospace Engineering at North Carolina State University. He was a Postdoctoral Scholar at UCLA, and received his Ph.D. from Florida State University, M.S. from the National Taiwan University, and B.S. from the National Chiao Tung University, all in Mechanical Engineering. His research is supported by the U.S. Army Research Office and the Department of Agriculture. He is a senior member of AIAA and currently serving on the Fluid Dynamics Technical Committee.