 |
| Titel |
Horizontal rolls in a convective flow driven by differential heating |
| VerfasserIn |
Andrey Sukhanovsky, Peter Frick, Andrey Teymurazov, Vladimir Batalov |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046580
|
|
|
|
|
|
| Zusammenfassung |
| Secondary flows in the form of horizontal rolls are a common feature of a large variety of
flows of different nature and scale. Roll vortices are often observed in the atmospheric
boundary layer. Depending on their size and strength, rolls play a significant role in
transporting momentum, heat and moisture through the atmospheric boundary layer. Our
aim is to study the problem of horizontal rolls generation in a natural (not mixed)
convective flow above a partially heated surface in a closed domain with a free surface.
Horizontal rolls, generated in convective flow above a partially heated bottom in a
rectangular box are studied experimentally for a wide range of the Prandtl number
(7 -¤ Pr -¤ 1020), the Rayleigh number (300 -¤ Ra -¤ 2.8 -
107) and the aspect ratio
(0.08 -¤ a -¤ 0.7). Experimental studies are supported by direct numerical simulations,
which made possible the examination of the regimes inaccessible in the experiment,
and also to investigate in detail the heat transfer in the convective flow. A variety
of regimes with longitudinal helical rolls, with transverse rolls and with mixed
structures has been observed. The structure of secondary flows is defined by the level of
convective supercriticality in the boundary layer (Rayleigh number) and the intensity
of the throughflow, defined by the Reynolds number, which depends itself on the
heating and size, i.e. on the Rayleigh number. Though the Reynolds number is not a
governing parameter in a proper sense, we succeeded to clear separate domains with
different kinds of rolls on the Reynolds – Rayleigh numbers plane only. The transverse
rolls appear in the flow only under the conditions of the large vertical drop in the
temperature and weak large-scale flow (that is possible only at large values of the Prandtl
number). Both longitudinal and transverse rolls lead to remarkable heat transfer
enhancement. The formation and characteristics of horizontal rolls are described in details. |
|
|
|
|
|
|