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Showing 1 to 20 of 43 for “"Rayleigh number"”.
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A spectral method determination of the first critical Rayleigh number for a low-Prandtl number crystal melt in a cylindrical container
The onset of laminar Rayleigh-Bénard convection is investigated for a low-Prandtl number liquid metal in a cylindrical container. All surfaces are considered to be solid and no-slip. Two cases are considered for the thermal boundary conditions at the side wall: conducting and insulated surfaces. A …
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A Numerical And Interferometric Study Of Natural Convective Heat Transfer From Divided And Undivided Vertical Channels
… centre line. The study examined the effect of Rayleigh number, plate-to-channel length ratio, vertical plate position, and plate thickness on the heat transfer from the channel walls, the dividing plate and the channel as a whole.;Solutions to both the full elliptic and parabolic forms of the …
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Numerical Simulation of Natural Convection in Rectangular Enclosures of Varying Aspect Ratios and its Feasibility in Environmental Impact Management Studies
… a variety of different aspect ratios (AR) and Rayleigh numbers (Ra). Each aspect ratio (1, 2, 4, 6, 8, and 10) was examined using different sets of Rayleigh numbers. The first numerical experiment used only external Rayleigh number (RaE = 2x104, 2x105, and 2x106) which simulated natural …
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The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth
… be explained by conductive cooling with age. A number of these anomalies require additional convective thermal sources at depths below the plate: mid-plate swells, the evolution of fracture zones, the mean depth and heat flow relationships with age and the observation of small scale (150-250 km) …
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The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth
… be explained by conductive cooling with age. A number of these anomalies require additional convective thermal sources at depths below the plate: mid-plate swells, the evolution of fracture zones, the mean depth and heat flow relationships with age and the observation of small scale (150-250 km) …
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Thermal convection in slender laterally-heated cavities
… walls, are studied numerically over a range of Rayleigh numbers and Prandtl numbers. As the Rayleigh number increases, nonlinearity first affects the flow structure in the turning regions near the ends of the cavity. These `end-zone problems' have been investigated by a combined computational …
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A Quantitative Analysis of a Non-Eruptive Volcanic Event: Mt. Spurr, Alaska, 2002-2006
… Scaling hydrothermal convection in terms of its Rayleigh number and using boundary layer analysis suggests that the mean permeability of the volcanic edifice prior to the unrest event was ~10-14 m2. CO2 release, most likely related to mechanical fracturing of the edifice by over-pressurized …
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A Thermistor Based Method for Measurement of Thermal Conductivity and Thermal Diffusivity of Moist Food Materials at High Temperatures
… measured with a temperature step of 5.0 °C. A Rayleigh number was defined to study the notion of a critical Rayleigh number at the onset of convection. This study found that when the Rayleigh number was below 43, convection could not be demonstrated. For a Rayleigh number of 84 and higher, …
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The Stability Properties of Some Rheological Flows
… are characterised by a critical Reynolds number which represents the ratio of inertial forces to viscous forces, and instability occurs when the inertial forces become large.<br/><br/>For non-Newtonian viscoelastic fluids the instability is characterised by a critical Weissenberg number, …
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Investigation of mean flow and vertical vorticity in turbulent convection using spectral simulations on massively parallel processors
Direct numerical simulations of Rayleigh-Benard convection are performed at several values of Rayleigh number (Ra). The computational domain consists of a square-planform rectangular box with horizontal-to-vertical aspect ratio equal to four. This domain is periodic in the horizontal directions, …
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Convective Heat Transfer in Quasi-one-dimensional Magnetic Fluid in Horizontal Field and Temperature Gradients
… by optical flow method. Calculated Nusselt numbers, Rayleigh number, and Grashof number show that the convective flow is the main heat transfer mechanism in applied fields in our geometry. It was found that when the field gradient is parallel with temperature gradient, the fields enhance the …
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Studying 3D Spherical Shell Convection using ASPECT
… the root mean square velocity (Vrms) and Nusselt number agree, often to within 1%. The 3D cases come from Zhong et al. (2008). Modifications were made to the simple.cc and harmonic_perturbation.cc files in the ASPECT code in order to reproduce the initial conditions and temperature-dependence of …
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Particle image velocimetry for natural convection in a cube at high Rayleigh numbers
… the dominant flow structures. The low turbulence Rayleigh number regime 5.08E7<Ra<3.40E8 is examined for the first time and experimental results including streamlines, the two velocity components in the vertical and horizontal direction, Reynolds stresses, swirling strength and vorticity are …
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Thermally driven circulation
… parameter controlling the circulation is now the Rayleigh number, which is a measure of the relative importance of gravitational and viscous forces. The effects of the convective overturning adjustment is investigated at different Rayleigh numbers. It is shown that not only is the stratification …
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A matrix-free numerical bifurcation method applied to sheared annular electroconvection
… the main nondimensional control parameter, the Rayleigh number R. This method consists of a natural continuation method by detecting fixed points of two different discrete-time dynamical systems based on numerical integration, and a linear stability analysis that identifies the local behaviour …
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Adaptive State Feedback Control of Lorenz Systems to Its Non-Trivial Equilibrium
… loop. The Lorenz system is chaotic for large Rayleigh number. In this chaotic regime, we implement a linear state feedback controller to stabilize the state trajectory at its original nontrivial equilibrium. The state variable for feedback is easily measurable. The system is proved to be …
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The effects of thermal radiation on dry convection
… models. The first type of model resembles Rayleigh-Benard convection, except that thermal radiative transfer is included. This type of system can be investigated in the laboratory. The second type of model is a more faithful representation of the earth's atmosphere. In this model, the …
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The Spatial Structure of Turbulent Rayleigh-Benard Convection
… the cellular structures commonly observed at low Rayleigh numbers. The circulation cells are proposed as a physical description (not an explanation) of the phenomenon referred to in the literature as the wind of turbulence. They were found to contain approximately 40% of the total kinetic energy, …
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Experimental Investigation of Liquid and Gas Fueled Flames Towards the Development of a Burning Rate Emulator (BRE) for Microgravity Applications
… Dimensionless correlations, using a Rayleigh number and the orientation angle, collapsed most of the data, but not for the horizontal and vertical cases. The measured heat flux correlated with expected averages based on burning rate data; theoretical results were similar but radiation …
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A New Numerical Method--Asymptotically Simplified Iteration Method With Patching as Applied to Free and Mixed Convection Heat Transfer
… It is based on the natural structure of high Rayleigh number free convection, which consists of thin thermal and viscous boundary layers surrounded by a region of negligible viscous and conductive influences. Iteration techniques appropriate for each region are obtained from considerations of …
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