Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Laboratory studies of high Rayleigh number circulation in an open-top Hele-Shaw cell: An analog to mid-ocean ridge hydrothermal systems
Autore:
Cherkaoui, ASM; Wilcock, WSD;
Indirizzi:
Univ Washington, Sch Oceanog, Seattle, WA 98195 USA Univ Washington Seattle WA USA 98195 , Sch Oceanog, Seattle, WA 98195 USA
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
fascicolo: B6, volume: 106, anno: 2001,
pagine: 10983 - 11000
SICI:
0148-0227(20010610)106:B6<10983:LSOHRN>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
DE-FUCA RIDGE; THERMAL BALANCE MODEL; PACIFIC RISE CREST; MIDOCEAN RIDGE; POROUS-MEDIUM; OSCILLATORY CONVECTION; NATURAL-CONVECTION; SULFIDE DEPOSITS; PERMEABILITY; HEAT;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
59
Recensione:
Indirizzi per estratti:
Indirizzo: Cherkaoui, ASM Univ Calif Santa Cruz, Dept Earth Sci, Santa Cruz, CA 95064USA Univ Calif Santa Cruz Santa Cruz CA USA 95064 CA 95064 USA
Citazione:
A.S.M. Cherkaoui e W.S.D. Wilcock, "Laboratory studies of high Rayleigh number circulation in an open-top Hele-Shaw cell: An analog to mid-ocean ridge hydrothermal systems", J GEO R-SOL, 106(B6), 2001, pp. 10983-11000

Abstract

Ridge crest hydrothermal systems are generally characterized by high heat fluxes and a permeable top which allows fluids to flow freely across the seafloor. The basic patterns of flow and heat transport in such systems are poorly known especially at high Rayleigh numbers. We present the results of a laboratory study using a wide-aspect ratio, open-top Hele-Shaw cell heated from below. The model is an analog for two-dimensional hydrothermal convection. The onset of convection occurs at a Rayleigh number Ra = 20.4 in good agreement with numerical predictions. Above onset, the spacing of upwelling plumes decreases quickly with the Rayleigh number before reaching an asymptotic limit in the range 0.2-0.3 above Ra approximate to 125. Periodic unsteady flow is first observed at Ra approximate to 47 and is a result of small thermals that are advected horizontally in the bottom boundary layer. The amplitude, frequency, and irregularity of oscillations increase with theRayleigh number. Unsteadiness can also result from the repeated formation of new plumes accompanied by the merging of plumes elsewhere in the model. Above Ra approximate to 590, the flow patterns show no dominant frequency and are chaotic. In the unsteady regime the frequency of oscillations scalesas Ra-1.92 and the Nusselt number scales as Ra-0.91 above Ra approximate to 200. These relationships are in close agreement with theoretical scalingsfor high Rayleigh number porous convection, Nu a Ra and f proportional to Ra-2. Assuming vigorous mid-ocean ridge systems can be approximated by flowthrough a Darcy porous media, our results predict that upwelling sites will be spaced at about half the depth of circulation. This is compatible withobservations on the Endeavour segment of the Juan de Fuca Ridge. Our results also predict that ridge crest hydrothermal systems with Nusselt numbers of 10-500, will exhibit unsteady flow at periods of similar to 500-0.2 years. Unsteady convection has not yet been observed, perhaps because highly permeable flow channels stabilize the flow in real systems.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 09/04/20 alle ore 13:21:25