Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

TRANSITION OF THERMAL BOUNDARY LAYERS AND ITS IMPLICATION FOR HEAT TRANSFER

Get access (open in a dialog) DOI: 10.1615/IHTC16.kn.000021
pages 395-408

Abstrakt

This paper describes experimental and numerical investigations of pure natural convection (thermal) boundary layers undergoing natural and controlled transitions. The natural transition takes place naturally under the influence of arbitrary or random perturbations, whereas the controlled transition is triggered by artificial perturbations of particular forms. In this study, two types of controlled transitions including K-type and H-type transitions are investigated. It is found that a frequency and wavenumber filtering process takes place in thermal boundary layers undergoing natural transition, and aligned and staggered Λ-shaped structures appear in thermal boundary layers undergoing the K-type and H-type transitions respectively. The transition depends on both the perturbation frequency and amplitude. The numerical simulation further demonstrates that the transition of thermal boundary layers is controlled by buoyancy effects rather than by Reynolds stresses, and the heat transfer through the heated surface is enhanced significantly as a result of the thermal boundary layer transition.