Sergio Pirozzoli

TL;DR: In this paper, Huang et al. studied compressible turbulent flow in a circular pipe at computationally high Reynolds number and found that Huang's transformation yields excellent universality of the scaled Reynolds stresses distributions, whereas the transformation proposed by Trettel and Larsson (2016) yields better representation of the effects of strong variation of density and viscosity occurring in the buffer layer on the mean velocity distribution.

Abstract: We use a direct numerical simulations (DNS) database for turbulent flow in a square duct up to bulk Reynolds number to quantitatively analyse the role of secondary motions on the mean flow structure. For that purpose we derive a generalized form of the identity of Fukagata, Iwamoto and Kasagi (FIK), which allows one to quantify the effect of cross-stream convection on the mean streamwise velocity, wall shear stress and bulk friction coefficient. Secondary motions are found to contribute approximately 6 % of the total friction, and to act as a self-regulating mechanism of turbulence whereby wall shear stress non-uniformities induced by corners are equalized, and universality of the wall-normal velocity profiles is established. We also carry out numerical experiments whereby the secondary motions are artificially suppressed, in which case their equalizing role is partially taken by the turbulent stresses.

TL;DR: The application of the analysis to wave propagation problems in a two-dimensional environment demonstrates that the analysis carried out for the scalar case directly applies to the propagation of monochromatic sound waves.

TL;DR: In this paper, high-resolution numerical simulations of the Euler and Navier-Stokes equations for a pair of colliding dipoles are presented, and it is shown that the formation of an inertial range is accompanied by transfer of energy that is local in both physical and spectral space.

TL;DR: In this paper, the authors study turbulent flows in pressure-driven ducts with square cross-section through direct numerical simulation in a wide enough range of Reynolds number to reach flow conditions which are representative of fully developed turbulence.