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L'école > Actualités > Séminaire au LEMTA de Nancy par Benoit Talbot
Séminaire au LEMTA de Nancy par Benoit Talbot
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Le Laboratoire d'Energétique et de Mécanique Théorique et Appliquée (LEMTA) de Nancy recevra le Jeudi 17 Décembre à 14h, Benoit Talbot, enseignant chercheur de l'EcoLe d'Ingénieurs des Sciences Aérospatiales (ELISA Aerospace).

Le Laboratoire d'Energétique et de Mécanique Théorique et Appliquée (LEMTA) de Nancy recevra le Jeudi 17 Décembre à 14h, Benoit Talbot, enseignant chercheur de l'EcoLe d'Ingénieurs des Sciences Aérospatiales (ELISA Aerospace) sur le thème:

Shock wave intensification in non-homogeneous isothermal compressible flows with variable-viscosity

We study isothermal shocklets which occur within compressible mixing layers and that constitute one of the major challenges faced in the design of high-speed vehicles. The main question we address here is: what influence on the wave steepening arises when viscosity of the medium through which the wave propagates is not constant? This question is quite relevant since within the shock transition zone viscous effects are important while they are negligible in both the pre-shock and post-shock zones, and, on the other hand, most real flows involve variable-viscosity flows.
A one-dimensional Burgers's flow with variable-viscosity model governed by an advection-diffusion equation has been derived from the set of fully 1D compressible equations and has been studied analytically and numerically. The inhomogeneous shocklet is modeled by a fixed sine wave for the initial velocity profile whilst different sine waves of higher frequency are used for the initial embedded distribution of scalar. The initial kinematic viscosity ratio Rn ranges from 1 to 4. For all conditions at Rn > 1, three major discrepancies with the classical isoviscous waves (Rn = 1) are demonstrated, that are : (i) a steeper maximum gradient in the shock transition zone, (ii) a tendency for the velocity spectra to extend their scaling k-1 in the inertial range toward the highest wavenumbers, and (iii) an enhanced energy dissipation rate. Results found are the opposite of what is observed with the isoviscous Burgers equation that demonstrates the noticeable effects of a variable-viscosity on the shock structure.


[1] : C.V. Tran and D.G. Dritschel, Energy dissipation and resolution of steep gradients in one-dimensional Burgers flows, Phys. Fluids, 22, 037102, 2010
[2] : B. Talbot, Y. Mammeri and N. Bedjaoui, Viscous shock anomaly in a variable-viscosity Burgers flow with an active scalar, Fluid Dynamics Research 47, 065502, 2015