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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

COUPLED TEMPERATURE AND VELOCITY MEASUREMENTS AND USE OF THE POD FOR THE ESTIMATION OF TURBULENT HEAT FLUXES IN A DIFFERENTIALLY HEATED CAVITY

DOI: 10.1615/TFESC1.fnd.012703
pages 909-923

Pierre Belleoud
Pprime Institute – CNRS – ENSMA – University of Poitiers, 1 avenue Clément Ader – BP 40109, F-86961 Futuroscope CEDEX, France

Didier Saury
Pprime Institute – CNRS – ENSMA – University of Poitiers, 1 avenue Clément Ader – BP 40109, F-86961 Futuroscope CEDEX, France

Denis Lemonnier
Laboratoire d'Etudes Thermiques, UMR CNRS 6608 Ecole Nationale Superieure de Mécanique et d'Aerotechnique, BP 40109, 86961, Futuroscope cedex, France


KEY WORDS: turbulent natural convection, differentially heated cavity, coupled measurements, POD, Coherent structures

Abstract

Natural convection flows have been investigated for decades; however, there are still pending issues especially concerning turbulent regimes. Indeed, simulations can predict even complex laminar flows with a high level of realism. But in order to improve calculation codes in turbulent regimes, like RANS models or LES subgrid models, the access to certain quantities (as thermal turbulent fluxes: and ) appears as a necessity as a matter of validation.
An experimental set-up consisting in a 4 m high differentially heated cavity is used where synchronized temperature and velocity measurements are carried out. The particular and rare dimensions of this cavity allow to obtain turbulent natural convection flows with a Rayleigh number (based on the height) equal to 1.2×1011 under the Boussinesq approximation. Temperature measurements have been performed using a K-type microthermocouple (12.7 μm in diameter) coupled with velocity measurements carried out using Particles Image Velocity (PIV). Measurements were carried out at mid-depth of the cavity. A suitable treatment, involving filtering methods based on Proper Orthogonal Decomposition (POD), led to the calculation of turbulent heat fluxes and other gradient-based quantities required for instance to the detection of coherent structures (vorticity, Q criteria…).
In this paper, a description of the experimental set-up and its boundary conditions will be provided. Then a description of the turbulent flow and temperature field in such a cavity will be presented. The results from coupled temperature and velocity measurements as well as profiles of turbulent heat fluxes at different locations of the cavity will finally be provided.

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