Energy dissipation and flux laws for unsteady turbulence

Direct Numerical Simulations of unsteady spatially periodic turbulence with time-dependent rms velocity u′(t) and integral length-scale L(t) show that not only the instantaneous energy dissipation rate but also the instantaneous energy flux at intermediate wavenumbers scales as View the MathML source where U0 and L0 are velocity and length scales characterizing initial or overall unsteady turbulence conditions. These high Reynolds number scalings are qualitatively different from the well-known u′(t)3/L(t) cornerstone scalings of equilibrium turbulence where the energy flux and dissipation are exactly balanced at all times

Nonequilibrium scalings of turbulent wakes

Nonequilibrium turbulent wake scalings are not the preserve of irregular (fractal-like/multiscale) plates but appear to be universal, as they also hold for regular plates over a very substantial downstream distance

The streamwise turbulence intensity in the intermediate layer of turbulent pipe flow

The spectral model of Perry et al. (J. Fluid Mech., vol. 165, 1986, pp. 163–199) predicts that the integral length scale varies very slowly with distance to the wall in the intermediate layer. The only way for the integral length scale’s variation to be more realistic while keeping with the Townsend–Perry attached eddy spectrum is to add a new wavenumber range to the model at wavenumbers smaller than that spectrum. This necessary addition can also account for the high-Reynolds-number outer peak of the turbulent kinetic energy in the intermediate layer. An analytic expression is obtained for this outer peak in agreement with extremely high-Reynolds-number data by Hultmark et al. (Phys. Rev. Lett., vol. 108, 2012, 094501; J. Fluid Mech., vol. 728, 2013, pp. 376–395). Townsend’s (The Structure of Turbulent Shear Flows, 1976, Cambridge University Press) production–dissipation balance and the finding of Dallas et al. (Phys. Rev. E, vol. 80, 2009, 046306) that, in the intermediate layer, the eddy turnover time scales with skin friction velocity and distance to the wall implies that the logarithmic derivative of the mean flow has an outer peak at the same location as the turbulent kinetic energy. This is seen in the data of Hultmark et al. (Phys. Rev. Lett., vol. 108, 2012, 094501; J. Fluid Mech., vol. 728, 2013, pp. 376–395). The same approach also predicts that the logarithmic derivative of the mean flow has a logarithmic decay at distances to the wall larger than the position of the outer peak. This qualitative prediction is also supported by the aforementioned data

Eulerian-Lagrangian aspects of a steady multiscale laminar flow

Accepted versio

Electromagnetically controlled multi-scale flows

Published versio

Physical scaling of numerical dissipation for LES

In this work, we are interested in an alternative way to perform LES using a numerical substitute of a subgrid-scale model with a calibration based on physical inputs

Particle tracking velocimetry and accelerometry (PTVA) measurements applied to quasi-two-dimensional multi-scale flows

Accepted versio