0000000000749666
AUTHOR
V.p. Trubitsyn
A study of hydrothermal convection in saturated porous media
Abstract Because of its relevance to many geological and technical problems, hydrothermal convection is investigated here mainly with the aid of numerical models by a systematic analysis of the properties of this type of convection for a range of super-critical Rayleigh numbers. Calculations were performed for two-dimensional models with constant properties in a region of aspect ratio 2. The principal results in the case of temperature fixed at the impermeable top and bottom are the following for the Nusselt number Nu, the cell aspect ratio a, and the boundary layer thickness δ: Nu ≈ 1.7 R0.5, a ≈ 1.3 R−0.4, δc ≈ 0.4 R−0.4 for 2.5 R = R f /R f ∗ and Rf and R f ∗ are the ambient and critical…
A self-consistent 2-D model for the dip angle ofmantle downflow beneath an overriding continent
Abstract We demonstrate how the inclination of descending mantle flow is affected by thepresence of a continent overriding the downwelling zone. The mantle is modelled by a fluidhaving a temperature- and pressure-dependent viscosity which describes a low viscosityasthenosphere and a higher viscosity lower mantle. The fluid occupies a square x:y=10:1 boxheated from below. In the absence of overlying continents thermal convection sets in with colddownwellings being nearly vertical. A continent is placed on the convecting mantle and starts todrift. The continent is assumed to be a thick rigid plate. We consider models of two types. Model1 involves a free-floating continent. The continent is pu…
Effects of Rayleigh number length thickness of continent on time of mantle flow reversal
Abstract Numerical experiments are carried out to study the effects of continents on the structure of thermal convection in the mantle. The mantle is modelled by a viscous fluid occupying a horizontally extended rectangular 2-D region of aspect ratio 10:1. Continents are treated as thick rigid heat-conducting plates placed in the mantle, with free-slip and with no-slip conditions. Continents restrict the heat release from the underlying mantle; the mantle material heats up and becomes lighter; as a result, a hot upwelling flow replaces downwelling. We calculate the characteristic time τ of this restructuring for various values of model parameters and obtain analytical approximations for τ a…