The spectrum of the vortex line density in a turbulent superfluid

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The spectrum of the vortex line density in a turbulent superfluid's image

Description:	Roche, PE (CNRS) Monday 29 September 2008, 16:00-16:30

Created:

2008-10-20 16:09

Collection:

The Nature of High Reynolds Number Turbulence

Publisher:

Isaac Newton Institute

Roche, PE

Language:

eng (English)

Credits:

Author:	Roche, PE
Producer:	Steve Greenham


Abstract:	Over the last twenty years, experiments and numerical simulations revealed strong similarities between Superfluid turbulence and Navier-Stokes turbulence. In particular, most measurements of integral quantities -such as the head loss in a pipe- or fluctuating ones -such as the velocity in the inertial range- could be interpretated by analogy with classical turbulence. Recently, measurements of the local fluctuations of the vortex lines density in superfluid 4He near 1.5 K have been reported. Over more than one decade of inertial range, the power spectrum was fitted with a f^(-5/3) power law. Remarkably, such a scaling differs from the one found in Navier-Stokes turbulence for the enstrophy, or for the absolute value of vorticity, which are often considered as classical counterparts of the vortex line density. We argue that this observation could be interpreted as the signature of a passive advection of the superfluid vortex lines by the largest scales of the flow. more info on : Roche P.-E. & Barenghi C. , EPL 81: 36002 (2008) http://crtbt.grenoble.cnrs.fr/helio/GROUP/infa.html A seminar from the Inertial-Range Dynamics and Mixing conference in association with the Newton Institute programme: The Nature of High Reynolds Number Turbulence www.newton.ac.uk/programmes/HRT/seminars/

Abstract:

Over the last twenty years, experiments and numerical simulations revealed strong similarities between Superfluid turbulence and Navier-Stokes turbulence. In particular, most measurements of integral quantities -such as the head loss in a pipe- or fluctuating ones -such as the velocity in the inertial range- could be interpretated by analogy with classical turbulence. Recently, measurements of the local fluctuations of the vortex lines density in superfluid 4He near 1.5 K have been reported. Over more than one decade of inertial range, the power spectrum was fitted with a f^(-5/3) power law. Remarkably, such a scaling differs from the one found in Navier-Stokes turbulence for the enstrophy, or for the absolute value of vorticity, which are often considered as classical counterparts of the vortex line density. We argue that this observation could be interpreted as the signature of a passive advection of the superfluid vortex lines by the largest scales of the flow.

more info on :
Roche P.-E. & Barenghi C. , EPL 81: 36002 (2008)
http://crtbt.grenoble.cnrs.fr/helio/GROUP/infa.html

A seminar from the Inertial-Range Dynamics and Mixing conference in association with the Newton Institute programme: The Nature of High Reynolds Number Turbulence www.newton.ac.uk/programmes/HRT/seminars/

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