@article{21295,
  abstract     = {Depending on the type of flow, the transition to turbulence can take one of two forms: either turbulence arises from a sequence of instabilities or from the spatial proliferation of transiently chaotic domains, a process analogous to directed percolation. The former scenario is commonly referred to as a supercritical transition and frequently encountered in flows destabilized by body forces, whereas the latter subcritical transition is common in shear flows. Both cases are inherently continuous in a sense that the transformation from ordered laminar to fully turbulent fluid motion is only accomplished gradually with flow speed. Here we show that these established transition types do not account for the more general setting of shear flows subject to body forces. The combination of the two continuous scenarios leads to the attenuation of spatial coupling; with increasing forcing amplitude, the transition becomes increasingly sharp and eventually discontinuous. We argue that the suppression of laminar–turbulent coexistence and the approach towards a discontinuous phase transition potentially apply to a broad range of situations including flows subject to, for example, buoyancy, centrifugal or electromagnetic forces.},
  author       = {Yang, Bowen and Zhuang, Yi and Yalniz, Gökhan and Vasudevan, Mukund and Marensi, Elena and Hof, Björn},
  issn         = {1745-2481},
  journal      = {Nature Physics},
  publisher    = {Springer Nature},
  title        = {{Discontinuous transition to shear flow turbulence}},
  doi          = {10.1038/s41567-025-03166-3},
  year         = {2026},
}

@article{10925,
  abstract     = {Direct numerical simulations (DNS) of turbulent channel flows up to  Reτ≈1000  are conducted to investigate the three-dimensional (consisting of streamwise wavenumber, spanwise wavenumber and frequency) spectrum of wall pressure fluctuations. To develop a predictive model of the wavenumber–frequency spectrum from the wavenumber spectrum, the time decorrelation mechanisms of wall pressure fluctuations are investigated. It is discovered that the energy-containing part of the wavenumber–frequency spectrum of wall pressure fluctuations can be well predicted using a similar random sweeping model for streamwise velocity fluctuations. To refine the investigation, we further decompose the spectrum of the total wall pressure fluctuations into the autospectra of rapid and slow pressure fluctuations, and the cross-spectrum between them. We focus on evaluating the assumption applied in many predictive models, that is, the magnitude of the cross-spectrum is negligibly small. The present DNS shows that neglecting the cross-spectrum causes a maximum error up to 4.7 dB in the subconvective region for all Reynolds numbers under test. Our analyses indicate that the approximation of neglecting the cross-spectrum needs to be applied carefully in the investigations of acoustics at low Mach numbers, in which the subconvective components of wall pressure fluctuations make important contributions to the radiated acoustic power.},
  author       = {Yang, Bowen and Yang, Zixuan},
  issn         = {1469-7645},
  journal      = {Journal of Fluid Mechanics},
  publisher    = {Cambridge University Press},
  title        = {{On the wavenumber-frequency spectrum of the wall pressure fluctuations in turbulent channel flow}},
  doi          = {10.1017/jfm.2022.137},
  volume       = {937},
  year         = {2022},
}