Linear Thermal Gradient Research Articles

Dewatering of a metamorphic pile

Hydraulic fracturing, induced by thermal expansion of water, is invoked as a common phenomenon by which metamorphic fluid is progressively lost from a sediment pile undergoing metamorphism and subsequent orogeny. On linear thermal gradients, water loss may occur by this mechanism for all gradients greater than 12°C/km at depths greater than 5 to 10 km. During burial on lower gradients, water is retained in the pile and may cause widespread metasomatism.

The onset of transient convective instability

The stability of a horizontal fluid layer when the thermal (or concentration) gradient is not uniform is examined by means of linear stability analysis. Both buoyancy and surface-tension effects are considered, and the analogous problem for a porous medium is also treated. Attention is focused on the situation where the critical Rayleigh number (or Marangoni number) is less than that for a linear thermal gradient, and the convection is not (in general) maintained. The case of constant-flux boundary conditions is examined because then a simple application of the Galerkin method gives useful results and general basic temperature profiles are readily treated. Numerical results are obtained for special cases, and some general conclusions about the destabilizing effects, with respect to disturbances of infinitely long wavelength, of various basic temperature profiles are presented. If the basic temperature gradient (considered positive, for a fluid which expands on heating, if the temperature decreases upwards) is nowhere negative, then the profile which leads to the smallest critical Rayleigh (or Marangoni) number is one in which the temperature changes stepwise (at the level at which the velocity, if motion were to occur, would be vertical) but is otherwise uniform. If, as well as being non-negative, the temperature gradient is a monotonic function of the depth, then the most unstable temperature profile is one for which the temperature gradient is a step function of the depth.

Heat Flow in the Aegean Sea

Summary Heat flow measurements taken in the Aegean Sea indicate a high heat flow in the northern and central Aegean. Nine stations at which a linear thermal gradient was measured give a mean value of 2-08 HFU. Four stations in the southern Aegean at which the gradient was non-linear gave limits to the heat flow in this area of between 1.0 and 1.6 HFU. Two high values in the north are associated with a deep bathymetric feature and intense magnetic anomalies. The high heat flow in the Aegean Sea is considered to be due to underthrusting of oceanic crust similar to that which occurs in the marginal basins of the north-west Pacific.

Crystallization of polypropylene measured by differential thermal analysis

AbstractThe crystallization of polypropylene has been studied by DTA in a linear thermal gradient type furnace. The crystallization rate was found to be linear with temperature, and the rate data were correlated on an Arrhenius type plot. The rate of crystallization of the low molecular weight fraction was lower at the same temperature than the rate for a higher molecular weight fraction.

Deformation and Moments in Elastically Restrained Circular Plates Under Arbitrary Load or Linear Thermal Gradient

The problem of a circular plate, with a central hole, elastically constrained against rotation and deflection, acted upon by a transverse linear temperature gradient or a general axisymmetrical loading condition is considered in this paper. With the aid of presented graphs and simple algebraic equations, it is a relatively simple matter to construct the desired deflection and stress pattern for any combination of elastic constraints and load distribution.

Closure to “Discussion of ‘Deformation and Moments in Elastically Restrained Circular Plates Under Arbitrary Load or Linear Thermal Gradient’” (1960, ASME J. Eng. Ind., 82, p. 438)

Closure to “Discussion of ‘Deformation and Moments in Elastically Restrained Circular Plates Under Arbitrary Load or Linear Thermal Gradient’” (1960, ASME J. Eng. Ind., 82, p. 438)

Bending Stresses Due to Temperature in Hollow Circular Plates, Part I

Note on Slow Viscous Flow Through the Space Between Two Coaxial Circular Cones With the Same Vertex T. K. CHAUDHURY 963 I PREVIOUS NOTES, 1, 2 formulas and curves have been presented for the nondimensional deflection, moments, and shears in a circular plate with a concentric hole subject to a linear thermal gradient through the thickness. . This note will give formulas and design curves for the deflections and moments (shear is identically zero) for the following problems: