Доступ предоставлен для: Guest

ISSN Online: 2377-424X

ISBN Print: 0-89116-130-9

International Heat Transfer Conference 6
August, 7-11, 1978, Toronto, Canada

HEAT TRANSFER AND PLOW INSTABILITY OF NATURAL CONVECTION OVER UPWARD-FACING HORIZONTAL SURFACES

Get access (open in a dialog) DOI: 10.1615/IHTC6.3220
pages 229-234

Аннотация

The two dimensional laminar flow field, which is built up over an upward-facing horizontal surface, becomes table as Rayleigh number increases. Then periodical variations of the field are observed for a certain range of Rayleigh number larger than 3 × 105. With a further increase of it, i.e. larger than about 108, the period becomes irregular. And the field gradually transfers to a turbulent state. The periodicity is not only experimentally observed, but also obtained by a conventional numerical calculation of the laminar flow field. According to the numerical means, it becomes obvious that the instability depends on the nonlinear interaction between the velocity and temperature fields. The instability, if it once occurs, gradually picks up three dimensional motions on the way to the down stream making lumps of fluid which have a temperature different from their surroundings. As the lumps diffuse a certain amount of heat, the heat transfer coefficient to the periodic flow field shows a behavior such as seen in a turbulent field.