Wavelet-based resolvent analysis of intermittently turbulent Stokes boundary layer

In this work, we study turbulent flow over periodic oscillating walls in the intermittently turbulent regime using wavelet-based resolvent analysis. Wavelet-based resolvent analysis uses wavelet transforms, rather than Fourier transforms in time, to form the resolvent operator. This preserves both frequency and time information and allows identification of time-localized nonlinear forcing modes that are optimally amplified by the linearized Navier-Stokes operator about a turbulent mean profile. This method is applied to the Stokes boundary layer systematically to study the time (phase)-localized forcing and response modes that inform the physical mechanism of this oscillatory flow with emphasis on the mechanism of temporal laminar-to-turbulent transition in the intermittently turbulent regime.