Constructing wall turbulence using hierarchically attached hairpin vortices

Abstract: Wall-bounded turbulence is characterized by coherent, worm-like structures such as hairpin vortices. The organization of these vortices near the wall can be modeled using the attached-eddy hypothesis, which effectively describes velocity statistics in the log-law region and energy-containing motions. However, the complex geometry and diverse scales of vortex structures in wall turbulence present significant challenges for developing and applying physics-based models. Here, we model wall turbulence as an ensemble of complex vortices, offering a systematic approach to constructing turbulence fields enriched with hierarchically organized hairpin vortex packets at a range of Reynolds numbers. The geometry and distribution of these vortex packets are calibrated to match physical observations and flow statistics. Our model successfully reproduces key features of wall turbulence, including mean velocity profiles, higher-order velocity fluctuation moments, near-wall streaks, and energy spectra that align with theoretical and numerical findings of turbulent channel flows at friction Reynolds numbers from 1,000 to 10,000. Furthermore, the constructed channel turbulence transitions rapidly to fully developed turbulence through direct numerical simulation, demonstrating its practicality for generating inlet or initial conditions in numerical simulations. This approach significantly reduces computational costs associated with turbulence development while providing a robust framework for testing and advancing turbulence models based on vortex structures.