scholarly journals The Evolution of an Average Solar Granule

1980 ◽  
Vol 51 ◽  
pp. 51-51 ◽  
Author(s):  
R.C. Altrock
Keyword(s):  
Temperature Fluctuations ◽  
Line Center ◽  
Line Profiles ◽  
Dimensional Model ◽  
Vacuum Tower ◽  
Velocity Fluctuations ◽  
Maximum Brightness ◽  
One Dimensional ◽  
Sacramento Peak Observatory ◽  
Better Than

AbstractHigh-resolution photographic spectra of the center of the solar disk have been obtained with the Vacuum Tower Telescope at Sacramento Peak Observatory. Two weak iron lines and the neighboring continuum were recorded with 40 sec time resolutions and better than 1” spatial resolution over a period of 40 min. Intensity and velocity fluctuations were obtained in the two lines and continuum as a function of time and space, and 300 sec oscillations were filtered out. The resulting fluctuations, due solely to granulation, were assembled into an ensemble average of the center of a granule and the center of an intergranular lane, as a function of time. The intensity-fluctuation data have been analyzed through calculation of model line profiles to yield temperature fluctuations in a granule as functions of time and height. We find that the line parameters are distinctly out of phase with continuum brightness, so that, for example, maximum brightness at line center occurs approximately 100 sec prior to maximum continuum brightness. A series of one-dimensional model atmospheres representing the granule at various stages of its lifetime is presented.

Microscale temperature and velocity spectra in the atmospheric boundary layer

1977 ◽  
Vol 83 (3) ◽  
pp. 547-567 ◽  
Author(s):  
R. M. Williams ◽  
C. A. Paulson
Keyword(s):  
Reynolds Number ◽  
Prandtl Number ◽  
Temperature Fluctuations ◽  
Inertial Subrange ◽  
Velocity Fluctuations ◽  
One Dimensional ◽  
Temperature Spectra ◽  
The Mean ◽  
Velocity Spectra ◽  
The One

High-frequency fluctuations in temperature and velocity were measured at a height of 2 m above a harvested, nearly level field of rye grass. Conditions were both stably and unstably stratified. Reynolds numbers ranged from 370000 to 740000. Measurements of velocity were made with a hot-wire anemometer and measurements of temperature with a platinum resistance element which had a diameter of 0[sdot ]5 μm and a length of 1 mm. Thirteen runs ranging in length from 78 to 238 s were analysed.Spectra of velocity fluctuations are consistent with previously reported universal forms. Spectra of temperature, however, exhibit an increase in slope with increasing wavenumber as the maximum in the one-dimensional dissipation spectrum is approached. The peak of the one-dimensional dissipation spectrum for temperature fluctuations occurs at a higher wavenumber than that of simultaneous spectra of the dissipation of velocity fluctuations. It is suggested that the change in slope of the temperature spectra and the dissimilarity between temperature and velocity spectra may be due to spatial dissimilarity in the dissipation of temperature and velocity fluctuations. The temperature spectra are compared with a theoretical prediction for fluids with large Prandtl number, due to Batchelor (1959). Even though air has a Prandtl number of 0[sdot ]7, the observations are in qualitative agreement with predictions of the theory. The non-dimensional wavenumber at which the increase in slope occurs is about 0[sdot ]02, in good agreement with observations in the ocean reported by Grantet al. (1968).For the two runs for which the stratification was stable, the normalized spectra of the temperature derivative fall on average slightly below the mean of the spectra of the remaining runs in the range in which the slope is approximately one-third. Hence the Reynolds number may not have always been sufficiently high to satisfy completely the conditions for an inertial subrange.Universal inertial-subrange constants were directly evaluated from one-dimensional dissipation spectra and found to be 0[sdot ]54 and 1[sdot ]00 for velocity and temperature, respectively. The constant for velocity is consistent with previously reported values, while the value for temperature differs from some of the previous direct estimates but is only 20% greater than the mean of the indirect estimates. This discrepancy may be explained by the neglect in the indirect estimates of the divergence terms in the conservation equation for the variance of temperature fluctuations. There is weak evidence that the one-dimensional constant, and hence the temperature spectra, may depend upon the turbulence Reynolds number, which varied from 1200 to 4300 in the observations reported.

Analysis of wave action in permeable structures

1976 ◽  
Vol 3 (1) ◽  
pp. 98-106 ◽  
Author(s):  
M. S. Nasser ◽  
J. A. McCorquodale
Keyword(s):  
Wave Motion ◽  
Line Profiles ◽  
Dimensional Model ◽  
Flume Experiments ◽  
Rectangular Section ◽  
One Dimensional ◽  
Wave Flume ◽  
The Face ◽  
The Mathematical Model ◽  
External Wave

This study treats wave motion within rectangular and sloping rockfill embankments with impervious cores. The non-Darcy flow in the rockfill is solved by a finite difference one-dimensional model. The characteristic directions are used to control the discretization of the solution domain. The entrance boundary condition (outcrop point) is computed from the external wave motion on the face of the rockfill. An equivalent rectangular section is used to approximate a sloping embankment, and waves on slopes are classified as 'fast' or 'slow rising.' The mathematical model yields phreatic line profiles with time. The model is supported by several wave flume experiments.

The spectrum of temperature fluctuations in turbulent flow

1968 ◽  
Vol 34 (3) ◽  
pp. 423-442 ◽  
Author(s):  
H. L. Grant ◽  
B. A. Hughes ◽  
W. M. Vogel ◽  
A. Moilliet
Keyword(s):  
Power Spectra ◽  
Temperature Fluctuations ◽  
Inertial Subrange ◽  
Velocity Fluctuations ◽  
One Dimensional ◽  
Open Sea ◽  
Spectrum Function ◽  
Velocity Spectra ◽  
The One ◽  
Rate Of Dissipation

Temperature and velocity fluctuations have been recorded in the open sea and in a tidal channel, and power spectra have been determined from the records. The one-dimensional spectra of temperature fluctuations are found to have an inertial subrange. At larger wave-numbers the data can be fitted by Batchelor's spectrum function for the viscous-convective range. The spectra are inconsistent with the form proposed by Pao for the viscous-convective range.Estimates are given for the constants in Batchelor's spectrum function, but these depend upon knowledge of the rate of dissipation of kinetic energy, which is determined from the velocity spectra. There is doubt about the validity of some of the velocity spectra, and in other cases there is reason to suspect that the turbulence is not locally isotropic.

The thermal insulation properties of oak (Quercus mongolica) bark and the applicability of stem heating models

2019 ◽  
Vol 28 (12) ◽  
pp. 969 ◽  
Author(s):  
Rui Wei ◽  
Guang Yang ◽  
Jili Zhang ◽  
Xiaohong Wang ◽  
Xin Zhou
Keyword(s):  
Thermal Insulation ◽  
Relative Importance ◽  
Dimensional Model ◽  
Quercus Mongolica ◽  
One Dimensional ◽  
Low Intensity ◽  
Surface Fires ◽  
Time Required ◽  
Mongolian Oak ◽  
Better Than

The survival probability of a tree exposed to surface fire varies widely depending on its bark. To advance the understanding of insulation properties of bark, mean thickness (BT), moisture content (MCb), surface structure (BS) and density (ρb) of bark samples of Mongolian oak (Quercus mongolica) (n=395) for four diameter classes were investigated. In addition, data from 158 heating experiments simulating low-intensity surface fires in the laboratory were used to assess the relative importance of these properties affecting thermal insulation and evaluate the applicability of two stem heating models, an analytical, one-dimensional model and the FireStem2D model. Overall, BT is the best predictor of bark insulation capacity and MCb only contributes significantly to explain the residence time of cambial temperature >60°C (τ>60), whereas ρb and BS have minor effects. Although the two stem heating models overestimate the time required for cambium temperatures to reach 60°C (τ60), FireStem2D performed better than analytical model. Furthermore, FireStem2D provides good predictions of τ>60 and maximal cambial temperature (Tmax). In addition, errors in FireStem2D may be driven mainly by the errors in temperature measurement and the limitation of a two-dimensional model. The study provides a better knowledge of interactions between bark properties and heat transfer, which may improve the predictability of fire-caused stem injury for Mongolian oak and other species with similar bark properties.

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

Modelling Techniques in Applied Glaciology: Numerical Modelling of Avalanches

1983 ◽  
Vol 4 ◽  
pp. 297-297
Author(s):  
G. Brugnot
Keyword(s):  
Finite Difference Method ◽  
Transverse Velocity ◽  
Longitudinal Velocity ◽  
Momentum Conservation ◽  
Dimensional Model ◽  
One Dimensional ◽  
Modelling Techniques ◽  
Reference Grid ◽  
The One ◽  
Near Future

We consider the paper by Brugnot and Pochat (1981), which describes a one-dimensional model applied to a snow avalanche. The main advance made here is the introduction of the second dimension in the runout zone. Indeed, in the channelled course, we still use the one-dimensional model, but, when the avalanche spreads before stopping, we apply a (x, y) grid on the ground and six equations have to be solved: (1) for the avalanche body, one equation for continuity and two equations for momentum conservation, and (2) at the front, one equation for continuity and two equations for momentum conservation. We suppose the front to be a mobile jump, with longitudinal velocity varying more rapidly than transverse velocity.We solve these equations by a finite difference method. This involves many topological problems, due to the actual position of the front, which is defined by its intersection with the reference grid (SI, YJ). In the near future our two directions of research will be testing the code on actual avalanches and improving it by trying to make it cheaper without impairing its accuracy.

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