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Large-scale tomographic PIV in forced and mixed convection using a parallel SMART version

Kühn, Matthias and Ehrenfried, Klaus and Bosbach, Johannes and Wagner, Claus (2012) Large-scale tomographic PIV in forced and mixed convection using a parallel SMART version. Experiments in Fluids, Vol. 53 (1), pp. 91-103. Springer Verlag. DOI: 10.1007/s00348-012-1301-9. ISSN 0723-4864 (Print), 1432-1114 (electronic version).

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Official URL: http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s00348-012-1301-9

Abstract

Large-scale tomographic particle image velocimetry (tomographic PIV) was used to study large-scale flow structures of turbulent convective air flow in an elongated rectangular convection cell. Three flow cases have been investigated, that is, pure forced convection and mixed convection at two different Archimedes numbers. The Reynolds number was constant at Re = 1.04 × 10^4 for all cases, while the Archimedes numbers were Ar = 2.1 and 3.6 for the mixed convection cases, corresponding to Rayleigh numbers of Ra = 1.6 × 10^8 and 2.8 × 10^8, respectively. In these investigations, the size of the measurement volume was as large as 840 mm × 500 mm × 240 mm. To allow for statistical analysis of the measured instantaneous flow fields, a large number of samples needed to be evaluated. Therefore, an efficient parallel implementation of the tomographic PIV algorithm was developed, which is based on a version of the simultaneous multiplicative reconstruction technique (SMART). Our algorithm distinguishes itself amongst other features by the fact that it does not store any weighting coefficients. The measurement of forced convection reveals an almost two-dimensional roll structure, which is orientated in the longitudinal cell direction. Its mean velocity field exhibits a core line with a wavy shape and a wavelength, which corresponds to the height and depth of the cell. In the instantaneous fields, the core line oscillates around its mean position. Under the influence of thermal buoyancy forces, the global structure of the flow field changes significantly. At lower Archimedes numbers, the resulting roll-like structure is shifted and deformed as compared to pure forced convection. Additionally, the core line oscillates much more strongly around its mean position due to the interaction of the roll structure with the rising hot air. If the Archimedes number is further increased, the roll-like structure breaks up into four counter-rotating convection rolls as a result of the increased influence of buoyancy forces. Moreover, large-scale tomographic PIV reveals that the orientation of these rolls reflects a ‘W’-like shape in the horizontal X–Z-plane of the convection cell.

Document Type:Article
Additional Information:Published online: 04. May 2012
Title:Large-scale tomographic PIV in forced and mixed convection using a parallel SMART version
Authors:
AuthorsInstitution or Email of Authors
Kühn, Matthiasmatthias.kuehn@dlr.de
Ehrenfried, KlausUNSPECIFIED
Bosbach, JohannesUNSPECIFIED
Wagner, ClausUNSPECIFIED
Date:2012
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:Vol. 53
DOI:10.1007/s00348-012-1301-9
Page Range:pp. 91-103
Publisher:Springer Verlag
ISSN:0723-4864 (Print), 1432-1114 (electronic version)
Status:Published
Keywords:tomographic particle image velocimetry; tomographic PIV; Tomo-PIV; large-scale PIV; Helium-filled soap bubbles; Helium bubbles; SMART implementation; simultaneous algebraic reconstruction technique; parallelization; high-performance computing; HPCC; validation; large-scale flow structures; confined forced convection; confined mixed convection
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Systems & Cabin
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Fluid Systems
Deposited By: Matthias Kühn
Deposited On:08 May 2012 11:23
Last Modified:26 Mar 2013 13:20

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