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Analysis of thermal plumes by means of combined velocity and temperature field measurements

Schmeling, Daniel (2015) Analysis of thermal plumes by means of combined velocity and temperature field measurements. Offenes Kolloquium „Experimentelle Thermofluiddynamik“, 10. Dez. 2015, Magdeburg, Deutschland.

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Abstract

Combined particle image thermography and particle image velocimetry (PIT / PIV) using thermochromic liquid crystals (TLCs) is presented as a measurement technique for the simultaneous acquisition of instantaneous temperature and velocity fields in air flows. Details of the particle generation, their illumination, a noise-filtering routine and the color-temperature calibration are presented. This technique is applied to mixed convection in a cuboidal sample. Therein, the dynamics of thermal plumes and their abundance is investigated. The working fluid is air at ambient pressure. Combined PIT and PIV is conducted in a horizontal layer close above the bottom thermal boundary layer and in a vertical layer. Within the vertical layer the formation of thermal plumes, which transport the heat from the warm bottom plate towards the cold top plate of the sample, are visible. The temperature and the velocity fields reveal the mean wind and the detachment of the plumes. The fingerprints of sheet-like plumes and those of the stems of mushroom like plumes are visible in the instantaneous temperature fields of the horizontal measurement plane. A study of temperature PDFs reveals, that the distributions can be described by a sum of two Gaussian distributions. Analyzing the ratio of the probabilities P_2/P_1 reveals a sudden change at a critical Ra_c. Here P_1 denotes the abundance of fluid temperatures imprinted by the bulk flow, while P_2 represses the abundance of temperatures ascribed to warm thermal plumes. Accordingly, P_2/P_1 is a measure for the plume fraction in the measurement plane.

Item URL in elib:https://elib.dlr.de/100972/
Document Type:Conference or Workshop Item (Speech)
Title:Analysis of thermal plumes by means of combined velocity and temperature field measurements
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Schmeling, DanielDaniel.Schmeling (at) dlr.deUNSPECIFIED
Date:2015
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:PIT / PIV, thermochromic liquid crystals (TLCs), mixed convection, thermal plumes
Event Title:Offenes Kolloquium „Experimentelle Thermofluiddynamik“
Event Location:Magdeburg, Deutschland
Event Type:Other
Event Dates:10. Dez. 2015
Organizer:Otto von Guericke Universität Magdeburg, Fakultät für Verfahrens- und Systemtechnik, Institut für Strömungstechnik und Thermodynamik, Prof. Dr. Dominique Thévenin
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Terrestrial Vehicles (old)
DLR - Research area:Transport
DLR - Program:V BF - Bodengebundene Fahrzeuge
DLR - Research theme (Project):V - Next Generation Train III (old)
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Fluid Systems
Deposited By: Micknaus, Ilka
Deposited On:17 Dec 2015 10:42
Last Modified:10 May 2016 23:38

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