[Todos] Coloquios DF - Martin Obligado - Jueves 13/11

[Nahuel Andrés]

Estimadas/os,

Les invitamos al próximo coloquio del DF a cargo de,

*Martín Obligado* (Centrale Lille Institut, France)
*Dissipation and intermittency in turbulent wakes*

The study of turbulent flows continues to challenge researchers. For
instance, within the global effort to increase the generation of
alternative energy, the study of the flow downstream of one or multiple
turbines has drawn significant attention from the turbulence community due
to its complexity. It involves turbulent wakes, their interactions, and
their coupling with the background turbulent flow.

Many recent advances in the modelling of turbulent flows have yet to be
adapted for such studies. To advance this research, a deeper understanding
of the inner structure of turbulence, the energy cascade, is required. This
phenomenon governs how energy is transferred from large to small scales and
how it is ultimately dissipated. It has been found to play a crucial role
in defining key properties of turbulent wakes, such as their velocity
deficit and their streamwise spreading behaviour.

In this seminar, I will discuss recent advances in turbulence research,
particularly relevant to wind energy applications. I will present
experimental and theoretical evidence demonstrating the existence of a
non-canonical energy cascade observed across a broad range of flows,
including grid turbulence, turbulent boundary layers, and the turbulent
axisymmetric wake. I will explore how this alternative cascade may result
in turbulent wakes exhibiting scaling laws different from those predicted
by standard models, such as the Richardson–Kolmogorov cascade. Moreover, I
will illustrate how an oscillating freestream velocity influences this
effect, as dissipation follows a hysteresis cycle linked to the unsteady
term in the Kármán–Howarth equation.

Furthermore, I will introduce a newly discovered empirical law relating the
energy cascade to small-scale intermittency in turbulent wakes and other
inhomogeneous flows. Our findings, based on an extensive range of flows and
experimental conditions, reveal a relationship between the dissipation
constant, which characterises the energy cascade, and the intermittency
factor, which quantifies deviations from self-similarity within the
inertial range. Interestingly, while no prior theoretical expectation
exists for a direct correlation between these two parameters, our results
show that one evolves as the inverse of the other, potentially establishing
a new universal law for turbulent flows.

Aula Federman - Primer Piso - Pabellón 1 - Ciudad Universitaria - CABA.
Comisión organizadora de los coloquios del DF 2025.
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