Electroconvective instability with a stabilizing temperature gradient. 1 - Theory
Perturbation theory for predicting electric field induced instability in fluid with stabilizing temperature gradients
Turnbull, R. J.↗
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Atmospheric temperature gradients related to clear air turbulence in the upper troposphere and lower stratosphere
Relationship between atmospheric temperature gradients and clear air turbulence of lower atmosphere
Kadlec, P. W.↗
Stresses and deformations in composite tubes due to a circumferential temperature gradient
A linear elasticity solution for determining the response of composite tubes subjected to a circumferential temperature gradient is presented. Numerical examples are used to show that, in a single layer tube, fiber orientation strongly influences response. When the fibers are aligned axially, all stress components in the tube are small. When the fibers are aligned circumferentially, the hoop stress becomes large. This difference in behavior is due to the large difference between the radial and circumferential coefficients of thermal expansion when the fibers are oriented circumferentially. In multilayer tubes, stresses are quite high and just two constants characterize the overall bending and axial deformations of the tubes.
Hyer, M. W.↗
Evaluation of Temperature Gradients During Cure of a Thick Carbon Fiber/Epoxy Composite
The purpose of this study is to evaluate the development of thermal gradients throughout thick (1") carbon fiber composites and determine the effect of internal temperature distribution during cure on the observed mechanical properties in those composites. Composites up to 1.5" thick (56 plies) were fabricated with T700S/TC380 braided prepreg from Tencate following a modified vacuum bag layup procedure to include embedded thermocouples within the plies of the composite. Composite panels were cured in a programmable oven with thermocouple reading embedded throughout the panel thickness. Maximum temperature gradients measured between regions of the composite did not exceed 10 degrees C for any given composite thickness. The most significant temperature variation was measured between the mid-thickness plies and the tool-side surface plies. Although through thickness temperature variation during cure was small, a measureable variation in coupon glass transition temperature was recorded between the tool side plies and the remainder of the part, prior to post cure. Thermal and mechanical behavior of coupons taken from segments through the thickness of the part were comparable following a post-cure cycle.
Miller, Sandi↗
A current generation by Compton scattering in a relativistic plasma with velocity shear and temperature gradient
Current generation by Thomson scattering in a non-relativistic plasma with the velocity shear and the temperature gradient (Hinata and Daneshvar, 1983) is extended to a relativistic plasma by replacing Thomson cross section by the Klein-Nishina formula. Because of the energy dependence of the cross-section, a numerical rather than analytic result is presented. The present calculation may be applied to a supernova implosion where the temperature may reach several MeV and a strong differential rotation is expected. It may also find applications in the early universe, and laser-pellet interaction.
Hinata, S.↗
Characterization of thermotropism in primary roots of maize: dependence on temperature and temperature gradient, and interaction with gravitropism
Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.
Non-NASA Center↗
Electroconvective instability with a stabilizing temperature gradient. II - Experimental results.
Electroconvective instability produced by uniform electric field in poorly conducting fluid under stabilizing vertical temperature gradient, noting heat flow increase
Turnbull, R. J.↗
Effect of the temperature gradient on the drift instabilities in a high-beta collisionless plasma
Inhomogeneous high-beta collisionless plasma temperature gradient effects on ion-acoustic and Alfvenic drift instabilities
Hung, R. J.↗
Infrared limb scanning in the presence of horizontal temperature gradients - An operational approach
Simulation and analysis of IR limb radiance obtained by a satellite-borne IR limb scanner have demonstrated that horizontal temperature gradients in the atmosphere play an important role in limiting the accuracy of retrieved temperature and constituents below approximately 25 km. A simple operational approach to converting these observed radiances to equivalent spherical radiances is developed which preserves the advantages of the sphericity assumption in the inversion process.
Roewe, D. A.↗
Temperature Gradients on the Cell Wall in the Critical Viscosity Experiment
Because of the diverging susceptibility delta rho/delta Tau near the liquid-vapor critical point, temperature gradients must be kept small to maintain adequate sample homogeneity. In our Science Requirements Document we paid particular attention to radial density gradients caused by equilibration of the xenon sample. Axial density gradients were addressed through the requirement that the cell's copper wall have a gradient less than 22 microK/m. This report re-examines the cell wall's temperature distribution in more detail by estimating all known significant contributions to temperature differences on the cell's wall.
Berg, Robert F.↗
Computer program performs frequency analysis of nonuniform turbine disk subjected to temperature gradients
Computer program determines the natural frequencies of a turbine disk of variable thickness subjected to uniform rotation and radial temperature gradients by using Rayleigh-Ritzs procedure. The program involves the potential and kinetic energy expressions for a circular flat plate of variable thickness.
Soo, P. P.↗
Variable-Temperature-Gradient Device for Solidification Research
Device for research in solidification and crystal growth allows crystallization of melt observed as occurs. Temperature gradient across melt specimen increased or decreased rapidly while solidification front proceeds at constant speed across sample. Device moves sample at same speed, thereby holding position of liquid/solid interface stationary within field of optical microscope. Device, variabletemperature-gradient microscope stage, used to study crystal growth at constant rate while thermal driving force is varied.
Kaukler, W. F.↗
Electroconvective instability with a stabilizing temperature gradient. I - Theory.
Linear perturbation theory to predict instability threshold conditions caused by electric field in poorly conducting liquid subject to vertical temperature gradient
Turnbull, R. J.↗
Non-Maxwellian velocity distribution functions associated with steep temperature gradients in the solar transition region. Paper 1: Estimate of the electron velocity distribution functions
It was shown that, in the presence of the steep temperature gradients characteristic of EUV models of the solar transition region, the electron and proton velocity distribution functions are non-Maxwellian and are characterized by high energy tails. The magnitude of these tails are estimated for a model of the transition region and the heat flux is calculated at a maximum of 30 percent greater than predicted by collision-dominated theory.
Roussel-Dupre, R.↗
Experimental and numerical determination of temperature gradients for a single tube alkali metal thermal-to-electric converter cell
This paper presents the results from the experimental and numerical determination of shell temperature gradients for a single tube AMTEC cell evaluated under simulated deep space operating conditions.
alkalai metal thermal-to-electric converter cell A↗
The doubled CO2 climate - Impact of the sea surface temperature gradient
The Goddard Institute for Space Studies (GISS) GCM of Hansen et al. (1983) was run, with 4 deg x 5 deg resolution, with doubled CO2 and two sets of sea surface temperature gradient distributions. One set was derived from the equilibrium doubled CO2 run of the 8 deg x 10 deg GISS GCM, with minimal high latitude amplification. The other set resembled closely the GFDL model results, with greater amplification. Both experiments had the same global mean surface air temperature change. The two experiments were often found to produce substantially different climate characteristics. With reduced high latitude amplification (set one), and thus, more equatorial warming, there was a greater increase in specific humidity and the greenhouse capacity of the atmosphere, resulting in a warmer atmosphere in general. Features such as the low-latitude precipitation, Hadley cell intensity, jet stream magnitude, and atmospheric energy transports all increased in comparison with the control run. In contrast, these features all decreased in the experiment with greater high latitude amplification (set two).
Rind, David↗
Acoustic response of a rectangular waveguide with a strong transverse temperature gradient
An acoustic wave equation was developed for a perfect gas with spatially-variable temperature. The strong-gradient wave equation was used to analyze the response of a rectangular wave guide containing a thermally-stratified gas. It was assumed that the temperature gradient is constant, representing one-dimensional heat transfer with a constant coefficient of conductivity. The analysis of the waveguide shows that the resonant frequencies of the waveguide are shifted away from the values that would be expected from the average temperature of the waveguide. For small gradients, the frequency shift is proportional to the square of the gradient. The factor of proportionality is a quadratic function of the natural frequency of the waveguide with uniform temperature. An experiment is designed to verify the essential features of the strong-gradient theory.
Zorumski, William E.↗
Influence of temperature gradients on the measurement accuracy of IR imaging systems
Implementing a new experimental aerodynamic technique, a long electrically heated wire was placed across flows with general velocity distributions (wakes, jets). By measuring the temperature distribution along the wire with an IR camera, the flow behavior was identified. Furthermore, it is suggested that by using Nusselt number correlations, the velocity distributions can be deduced. Comparing the results with predictions based on heat transfer correlations, it was found that the IR camera cannot accurately track high gradient temperature fields. A correction procedure is outlined to account for the errors found in the measured results.
Gartenberg, Ehud↗