Physical Review Journal Club: From Oblique-Wave Forcing to Streak Reinforcement: A Perturbation-Based Frequency-Response Framework
Thursday, July 23, 2026
12 p.m. ET, 18:00 CET
Video link
The Physical Review Journal Club is back, this time for a discussion with author Mihailo Jovanović (University of Southern California), presenting the recently published Physical Review Fluids paper “From Oblique-Wave Forcing to Streak Reinforcement: A Perturbation-Based Frequency-Response Framework.”
After the presentation, the author will answer questions from the audience in a live Q&A session, moderated by Kunihiko Taira (University of California, Los Angeles). Registration is free and a video recording will be provided to all registrants.
Summary:
In this work, the authors presented a perturbation-based frequency-response framework that expands the input–output dynamics of Navier-Stokes equations in the amplitude of external forcing. Fluctuation dynamics at each perturbation order are governed by the resolvent of the laminar base flow, with successive nonlinear interactions among lower-order responses driving the evolution at higher orders.
At second order, quadratic interactions of unsteady oblique-wave fluctuations generate steady streamwise streaks via the lift-up mechanism. The accuracy of the second-order weakly nonlinear expansion is confirmed through DNS at small forcing amplitudes.
At higher forcing amplitudes, the dynamics are governed by higher-order interactions between oblique waves and the induced streaks. These interactions generate a streak perturbation series whose wall-normal profile is captured by the second output singular function. Once the forcing amplitude exceeds a critical value, the perturbation series loses convergence, and DNS exhibits a transition to sustained unsteadiness.
Taken together, these results establish a self-consistent, physics-based framework for analyzing subcritical amplification mechanisms that incorporates nonlinear interactions within a frequency-response paradigm.
Read ahead:
From oblique-wave forcing to streak reinforcement: A perturbation-based frequency-response framework
Dušan Božić, Anubhav Dwivedi, and Mihailo R. Jovanović
Phys. Rev. Fluids 11, 063901
