The heated laminar vertical jet

[1] Laboratory experiments and numerical calculations are used to study how a laminar thermal plume deforms and penetrates a buoyant and viscous layer, which serves as an analog for continental lithosphere. The viscosity contrast between the two liquids and the buoyancy ratio B (the ratio between the intrinsic chemical density contrast and the thermal density contrast due to temperature differences) are varied by 3 orders of magnitude and 1 order of magnitude, respectively. The manner of plume-lithosphere interaction is not sensitive to the viscosity contrast, which sets the timescale for displacement of the interface, and depends mostly on the B value, which sets the magnitude and shape of interface deformation. Heating of the upper layer by plume material plays an important role. For B > 0.6, plume material spreads beneath the interface and applies a buoyancy force which deforms the interface. For B < 0.6, true plume penetration into the upper layer occurs with a significant vertical velocity component. With time, the upper layer may become unstable and develop an active upwelling which entrains material from the lower layer. Approximate scaling laws allow prediction of interface displacement as a function of time for the whole parameter range studied. Applied to the continental lithosphere, these results show that true plume penetration through Archean lithosphere requires thermal anomalies larger than 300 K corresponding to buoyancy fluxes in excess of those determined today for the Hawaiian plume. Mantle plumes have different effects on lithospheres of different ages and composition, which precludes diagnosis of a single ''typical'' plume signature.Citation: Jurine, D., C. Jaupart, G. Brandeis, and P. J. Tackley (2005), Penetration of mantle plumes through depleted lithosphere,

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“…One consequence is that a thermal plume rises at a constant velocity [Fujii, 1963;Brand and Lahey, 1967].…”

Section: B2 Outputsmentioning

confidence: 99%

Penetration of mantle plumes through depleted lithosphere

et al. 2005

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“…Numerical results are available up to a Prandtl number of 10 (e.g. Fujii 1963;Brand & Lahey 1967;Worster 1986) and an asymptotic analysis for large Prandtl numbers may be found in Worster (1986). These analyses are valid for the plume stem far from the leading edge (the cap) and do not specify the cap behaviour.…”

Section: Introductionmentioning

confidence: 99%

Laminar starting plumes in high-Prandtl-number fluids

Kaminski

Jaupart

2003

J. Fluid Mech.

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Experimental studies of laminar axisymmetric starting plumes are performed to investigate the dependence of the flow on the Prandtl number, focusing on large Prandtl numbers. Thermal plumes are generated by a small electric heater in a glass tank filled with viscous oils. Prandtl numbers in the range of 7–104 were investigated. Experimental conditions are such that viscosity variations due to temperature differences are negligible. Plumes ascend in two different regimes as a function of distance to source. At short distances, the plumes accelerate owing to the development of the viscous boundary layer. At distances larger than about five times the heater size, the ascent velocity is constant and increases as a function of the Prandtl number, as predicted by theory for steady plumes. This velocity is, within experimental error, proportional to the steady plume centreline velocity.

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“…For the constant viscosity case (C=O) with a linear rheology (n=1), these equations reduce to the point source equations of (Brand and Lahey, 1967;Liu and Chase, 1991).…”

Section: Boundary Layer Plume Modelmentioning

confidence: 99%

Geochemical and fluid dynamic investigations into the nature of chemical heterogeneity in the Earth's mantle

Hauri¹

1992

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The heated laminar vertical jet

Cited by 64 publications

References 3 publications

Penetration of mantle plumes through depleted lithosphere

Penetration of mantle plumes through depleted lithosphere

Laminar starting plumes in high-Prandtl-number fluids

Geochemical and fluid dynamic investigations into the nature of chemical heterogeneity in the Earth's mantle

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