Particle image velocimetry for natural convection in a cube at high Rayleigh numbers

The study of natural convection in enclosures has attracted the attention of numerous researchers over the past decades due to its applications in many practical engineering problems. Some examples include air conditioning and ventilation systems, electronic cooling devices, heat exchangers and thermal storage. In the present work an experimental investigation of natural convection developed in an air filled cube of side H=0.35m is conducted using Particle Image Velocimetry (PIV) to measure the velocity field within the cavity and visualize the dominant flow structures. The low turbulence Rayleigh number regime 5.08E7<Ra<3.40E8 is examined for the first time and experimental results including streamlines, the two velocity components in the vertical and horizontal direction, Reynolds stresses, swirling strength and vorticity are reported. In addition, Proper Orthogonal Decomposition (POD) was employed to analyze the flow and identify its major components. The estimated error from PIV measurements is within 1-2%, thus the high accuracy of the results can form experimental benchmark data and can be used to validate future CFD codes. Flow visualization enabled the study of the evolution of the boundary layers along the isothermal and adiabatic walls. Furthermore, two secondary re-criculations in the upper left and lower right corner of the cavity where measurements were conducted were also observed and reported. The two regions are anti-symmetric with the one in the upper left corner being initially stronger. Finally, heat transfer measurements on the hot wall were conducted and Nusslet number for the corresponding Rayleigh number was estimated. A correlation between the two numbers was obtained and compared against other correlations in the literature. A deviation from the classical power law theory was observed and it is attributed to radiation and non-Boussinesq effects. A concurrent computer simulations effort was also conducted and the results are presented for comparison with experimental data.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Georgiou, Marios

Contributors dc:contributor

• Georgiadis, John G.
• Jacobi, Anthony M.
• Brewster, M. Quinn
• Litchfield, J. Bruce

• Natural convection
• enclosures
• Particle Image Velocimetry (PIV)
• Proper Orthogonal Decomposition (POD)

Statement dc:rights

• Copyright 2014 Marios Georgiou

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/50345

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/50345