Thermal Effects in Incompressible Flow

Application of an HP-Adaptive Technique for Heat, Mass and Momentum Transport

Heat Transfer, Part A ◽

10.1115/imece2005-80079 ◽

2005 ◽

Author(s):

Xiuling Wang ◽

Darrell W. Pepper

Keyword(s):

Incompressible Flow ◽

Thermal Transport ◽

Thermal Effects ◽

Element Model ◽

Adaptive Finite Element ◽

Spectral Order ◽

Incompressible Viscous Flow ◽

Adaptation Procedure ◽

Mass Dispersion ◽

Adaptive Fem

A three-step hp-adaptive finite element model (FEM) is employed to solve the governing equations for incompressible flow including mass and thermal transport. The adaptive FEM uses both mesh enrichment (h-adaptation) and spectral order incensement (p-adaptation) to maximize the rate of decrease of the interpolation error. The three-step adaptive methodology can be used to solve a wide variety of problems related to incompressible viscous flow including mass dispersion along with thermal transport. Highly accurate solutions are obtained using an optimally refined final mesh. The L2 energy norm is calculated to guide the adaptation procedure. Simulation results for incompressible flow over a backward facing step, natural convection in a partitioned enclosure and mass transport within a partitioned enclosure under thermal effects are presented. Results are compared with experimental data and numerical simulations reported in the literature. The efficiency of the proposed numerical technology is discussed.

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Thermal Considerations in Lens Regulator Systems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100068783 ◽

1970 ◽

Vol 28 ◽

pp. 358-359

Author(s):

K.C. Newton

Keyword(s):

Electron Microscope ◽

Thermal Effects ◽

Environmental Control ◽

Reference Networks ◽

Better Than

Thermal effects in lens regulator systems have become a major problem with the extension of electron microscope resolution capabilities below 5 Angstrom units. Larger columns with immersion lenses and increased accelerating potentials have made solutions more difficult by increasing the power being handled. Environmental control, component choice, and wiring design provide answers, however. Figure 1 indicates with broken lines where thermal problems develop in regulator systemsExtensive environmental control is required in the sampling and reference networks. In each case, stability better than I ppm/min. is required. Components with thermal coefficients satisfactory for these applications without environmental control are either not available or priced prohibitively.

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Direct measurement of electron-diffraction-pattern intensities using an energy loss spectrometer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100155311 ◽

1989 ◽

Vol 47 ◽

pp. 668-669

Author(s):

A. G. Jackson ◽

M. Rowe

Keyword(s):

Thermal Effects ◽

Dynamic Range ◽

Scattering Amplitude ◽

Dynamical Theory ◽

Site Symmetry ◽

Proof Of Concept ◽

Parallel Acquisition ◽

Kinematic Approximation ◽

Speed Up ◽

Structure Calculations

Diffraction intensities from intermetallic compounds are, in the kinematic approximation, proportional to the scattering amplitude from the element doing the scattering. More detailed calculations have shown that site symmetry and occupation by various atom species also affects the intensity in a diffracted beam. [1] Hence, by measuring the intensities of beams, or their ratios, the occupancy can be estimated. Measurement of the intensity values also allows structure calculations to be made to determine the spatial distribution of the potentials doing the scattering. Thermal effects are also present as a background contribution. Inelastic effects such as loss or absorption/excitation complicate the intensity behavior, and dynamical theory is required to estimate the intensity value.The dynamic range of currents in diffracted beams can be 104or 105:1. Hence, detection of such information requires a means for collecting the intensity over a signal-to-noise range beyond that obtainable with a single film plate, which has a S/N of about 103:1. Although such a collection system is not available currently, a simple system consisting of instrumentation on an existing STEM can be used as a proof of concept which has a S/N of about 255:1, limited by the 8 bit pixel attributes used in the electronics. Use of 24 bit pixel attributes would easily allowthe desired noise range to be attained in the processing instrumentation. The S/N of the scintillator used by the photoelectron sensor is about 106 to 1, well beyond the S/N goal. The trade-off that must be made is the time for acquiring the signal, since the pattern can be obtained in seconds using film plates, compared to 10 to 20 minutes for a pattern to be acquired using the digital scan. Parallel acquisition would, of course, speed up this process immensely.

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