A Theoretical Investigation on the Structure of Fan Wakes

1978 ◽  
Vol 100 (1) ◽  
pp. 113-119 ◽  
Author(s):  
R. Raj ◽  
J. L. Lumley
Keyword(s):  
Decay Rate ◽  
Theoretical Investigation ◽  
Axial Velocity ◽  
Analytical Study ◽  
Turbulence Structure ◽  
Relative Order ◽  
Turbulent Characteristics ◽  
Order Of Magnitude ◽  
The Mean ◽  
Insight Into

An analytical study is presented of the mean and turbulent characteristics of axial turbulent wakes behind a rotating fan. Simplified solutions are presented governing the mean radial and axial velocity profiles and their decay rate. An estimate is made of the relative order of magnitude of various turbulence quantities. The effect of rotation on the turbulence structure is described. Sufficient physical interpretations and explanations are presented for insight into and formulation of the problem.

Some Explicit Results for the Mean Spherical Approximation for Mixtures of Yukawa Fluids

2008 ◽  
Vol 73 (3) ◽  
pp. 424-438 ◽  
Author(s):  
Douglas J. Henderson ◽  
Osvaldo H. Scalise
Keyword(s):  
Integral Equation ◽  
Spherical Approximation ◽  
Mean Spherical Approximation ◽  
Inverse Temperature ◽  
Temperature Expansion ◽  
Yukawa Fluid ◽  
The Mean ◽  
Full Solution ◽  
Insight Into ◽  
Reasonable Model

The mean spherical approximation (MSA) is of interest because it produces an integral equation that yields useful analytical results for a number of fluids. One such case is the Yukawa fluid, which is a reasonable model for a simple fluid. The original MSA solution for this fluid, due to Waisman, is analytic but not explicit. Ginoza has simplified this solution. However, Ginoza's result is not quite explicit. Some years ago, Henderson, Blum, and Noworyta obtained explicit results for the thermodynamic functions of a single-component Yukawa fluid that have proven useful. They expanded Ginoza's result in an inverse-temperature expansion. Even when this expansion is truncated at fifth, or even lower, order, this expansion is nearly as accurate as the full solution and provides insight into the form of the higher-order coefficients in this expansion. In this paper Ginoza's implicit result for the case of a rather special mixture of Yukawa fluids is considered. Explicit results are obtained, again using an inverse-temperature expansion. Numerical results are given for the coefficients in this expansion. Some thoughts concerning the generalization of these results to a general mixture of Yukawa fluids are presented.

SET-VALUED PERFORMANCE APPROXIMATIONS FOR THE QUEUE GIVEN PARTIAL INFORMATION

2020 ◽  
pp. 1-23
Author(s):  
Yan Chen ◽  
Ward Whitt
Keyword(s):  
Steady State ◽  
Decay Rate ◽  
Waiting Time ◽  
Partial Information ◽  
Upper And Lower Bounds ◽  
Interarrival Time ◽  
Limited Information ◽  
Wide Range ◽  
The Mean ◽  
Third Moment

In order to understand queueing performance given only partial information about the model, we propose determining intervals of likely values of performance measures given that limited information. We illustrate this approach for the mean steady-state waiting time in the $GI/GI/K$ queue. We start by specifying the first two moments of the interarrival-time and service-time distributions, and then consider additional information about these underlying distributions, in particular, a third moment and a Laplace transform value. As a theoretical basis, we apply extremal models yielding tight upper and lower bounds on the asymptotic decay rate of the steady-state waiting-time tail probability. We illustrate by constructing the theoretically justified intervals of values for the decay rate and the associated heuristically determined interval of values for the mean waiting times. Without extra information, the extremal models involve two-point distributions, which yield a wide range for the mean. Adding constraints on the third moment and a transform value produces three-point extremal distributions, which significantly reduce the range, producing practical levels of accuracy.

scholarly journals Relaxation Times in Strictly Disk Systems

1971 ◽  
Vol 10 ◽  
pp. 15-19
Author(s):  
George B. Rybicki
Keyword(s):  
Numerical Experiments ◽  
Relaxation Times ◽  
Galactic Structure ◽  
Large Numbers ◽  
Order Of Magnitude ◽  
Vlasov Limit ◽  
The Mean ◽  
Gravitating Systems

AbstractIt is shown that the time of relaxation by particle encounters of self-gravitating systems in the plane interacting by 1/r2 forces is of the same order of magnitude as the mean orbit time. Therefore such a system does not have a Vlasov limit for large numbers of particles, unless appeal is made to some non-zero thickness of the disk. The relevance of this result to numerical experiments on galactic structure is discussed.

Insight into the existing form of glycolaldehyde in methanol solution: an experimental and theoretical investigation

2021 ◽  
Author(s):  
Ce Hao ◽  
Yuehui Li ◽  
Yantao Shi ◽  
Xuedan Song ◽  
Zhengyan Zhao ◽  
...  
Keyword(s):  
Theoretical Investigation ◽  
Methanol Solution ◽  
Aldehyde Groups ◽  
Existing Form ◽  
Insight Into

Glycolaldehyde (HOCH2CHO, GA), the simplest molecule containing both hydroxyl and aldehyde groups, is structurally the most elementary member of the monosaccharide sugars, which may provide new clues for probing the...

A reduced-peak equivalence for queues with a mixture of light-tailed and heavy-tailed input flows

2003 ◽  
Vol 35 (03) ◽  
pp. 793-805 ◽  
Author(s):  
Sem Borst ◽  
Bert Zwart
Keyword(s):  
Service Rate ◽  
Opposite Case ◽  
Peak Rate ◽  
Workload Distribution ◽  
The Mean ◽  
Heavy Tailed ◽  
Insight Into

We determine the exact large-buffer asymptotics for a mixture of light-tailed and heavy-tailed input flows. Earlier studies have found a ‘reduced-load equivalence’ in situations where the peak rate of the heavy-tailed flows plus the mean rate of the light-tailed flows is larger than the service rate. In that case, the workload is asymptotically equivalent to that in a reduced system, which consists of a certain ‘dominant’ subset of the heavy-tailed flows, with the service rate reduced by the mean rate of all other flows. In the present paper, we focus on the opposite case where the peak rate of the heavy-tailed flows plus the mean rate of the light-tailed flows is smaller than the service rate. Under mild assumptions, we prove that the workload distribution is asymptotically equivalent to that in a somewhat ‘dual’ reduced system, multiplied by a certain prefactor. The reduced system now consists of only the light-tailed flows, with the service rate reduced by the peak rate of the heavy-tailed flows. The prefactor represents the probability that the heavy-tailed flows have sent at their peak rate for more than a certain amount of time, which may be interpreted as the ‘time to overflow’ for the light-tailed flows in the reduced system. The results provide crucial insight into the typical overflow scenario.

The influence of the singlet radical-pair decay rate on RYDMR and SNP spectra, and the mean RP lifetime

1990 ◽  
Vol 175 (5) ◽  
pp. 467-471 ◽  
Author(s):  
I.V. Koptyug ◽  
N.N. Lukzen ◽  
E.G. Bagryanskaya ◽  
A.B. Doctorov
Keyword(s):  
Decay Rate ◽  
Radical Pair ◽  
The Mean

scholarly journals Using the SWEPT Methodology for a Preliminary Wind Potential Estimation

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Jean-Luc Menet
Keyword(s):  
Wind Turbine ◽  
Characteristic Curve ◽  
Rayleigh Distribution ◽  
Mean Velocity ◽  
Technical Data ◽  
Wind Potential ◽  
Order Of Magnitude ◽  
General Data ◽  
The Mean ◽  
A Site

The implantation of wind turbines generally follows a wind potential study which is made using specific numerical tools; the generated expenses are only acceptable for great projects. The purpose of the present paper is to propose a simplified methodology for the evaluation of the wind potential, following three successive steps for the determination of (i) the mean velocity, either directly or by the use of the most occurrence velocity (MOV); (ii) the velocity distribution coming from the single knowledge of the mean velocity by the use of a Rayleigh distribution and a Davenport-Harris law; (iii) an appropriate approximation of the characteristic curve of the turbine, coming from only two technical data. These last two steps allow calculating directly the electric delivered energy for the considered wind turbine. This methodology, called the SWEPT approach, can be easily implemented in a single worksheet. The results returned by the SWEPT tool are of the same order of magnitude than those given by the classical commercial tools. Moreover, everybody, even a “neophyte,” can use this methodology to obtain a first estimation of the wind potential of a site considering a given wind turbine, on the basis of very few general data.

Infrared spectra, rotational correlation functions, and intermolecular mean squared torques in compressed gaseous methane

1968 ◽  
Vol 46 (11) ◽  
pp. 1331-1340 ◽  
Author(s):  
R. L. Armstrong ◽  
S. M. Blumenfeld ◽  
C. G. Gray
Keyword(s):  
Correlation Functions ◽  
Theoretical Calculations ◽  
Dominant Contribution ◽  
Dispersion Interactions ◽  
Fundamental Vibration ◽  
Order Of Magnitude ◽  
The Mean ◽  
Vibration Rotation ◽  
Experimental Values ◽  
Rotational Correlation

Extensive measurements of the methane ν3 and ν4 fundamental vibration–rotation bands in CH4–He mixtures and the ν3 band in CH4–He, CH4–N2, and CD4–He mixtures have been carried out in infrared absorption at 295 °K to pressures of 3000 atm. Some profiles of the ν3 band in CH4–Ar mixtures and in pure CH4 have also been obtained. Rotational correlation functions, band moments, and intermolecular mean squared torques have been determined from the ν3 band profiles. Theoretical calculations of the mean squared torque due to anisotropic multipolar, induction and dispersion interactions have been carried out. The theoretical and experimental torques are in order-of-magnitude agreement for the CH4–N2 and CH4–CH4 systems; for CH4–He, CD4–He, and CH4–Ar the theoretical values are two to three orders of magnitude too small to account for the experimental values, indicating that in these cases the dominant contribution to the torques is given by the anisotropic overlap forces.

scholarly journals Relationship between Body Mass Index and Tooth Decay in a Population of 3–6-Year-Old Children in Iran

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Leila Shafie Bafti ◽  
Maryam Alsadat Hashemipour ◽  
Hamidreza Poureslami ◽  
Zeinab Hoseinian
Keyword(s):  
Body Weight ◽  
Analytical Study ◽  
Deciduous Teeth ◽  
Tooth Decay ◽  
Cross Sectional ◽  
Dmft Index ◽  
The Mean ◽  
Iranian Children ◽  
The Relationship

The aim of the present study was to evaluate the relationship between BMI and tooth decay in a population of Iranian children. In this cross-sectional descriptive/analytical study, 1482 children were selected from kindergartens and preschool centers in Kerman, Iran. The children underwent examination of deciduous teeth (using the dmft index) after determination of height and weight for calculation of BMI. The relationship between BMI (after adjustment for age) and dmft was determined using Poisson’s regression model. The mean of dmft in children with normal BMI was 1.5-fold that in subjects with extra body weight. Age had a significant effect on dmft. In addition, dmft was higher in boys compared to girls. The results of the present study showed that caries rate in the deciduous teeth of 3–6-year-old children decreases with an increase in body weight.

Study of the Mechanisms of Vortex Variability in the Lofoten Basin Based on the Energy Analysis

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
V. S. Travkin ◽  
◽  
T. V. Belonenko ◽  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Baroclinic Instability ◽  
Positive Trend ◽  
Barotropic Instability ◽  
Available Potential Energy ◽  
Conversion Rates ◽  
Order Of Magnitude ◽  
The Mean ◽  
Mean Kinetic Energy

Purpose. The Lofoten Basin is one of the most energetic zones of the World Ocean characterized by high activity of mesoscale eddies. The study is aimed at analyzing different components of general energy in the basin, namely the mean kinetic and vortex kinetic energy calculated using the integral of the volume of available potential and kinetic energy of the Lofoten Vortex, as well as variability of these characteristics. Methods and Results. GLORYS12V1 reanalysis data for the period 2010–2018 were used. The mean kinetic energy and the eddy kinetic one were analyzed; and as for the Lofoten Vortex, its volume available potential and kinetic energy were studied. The mesoscale activity of eddies in winter is higher than in summer. Evolution of the available potential energy and kinetic energy of the Lofoten Vortex up to the 1000 m horizon was studied. It is shown that the vortex available potential energy exceeds the kinetic one by an order of magnitude, and there is a positive trend with the coefficient 0,23⋅1015 J/year. It was found that in the Lofoten Basin, the intermediate layer from 600 to 900 m made the largest contribution to the potential energy, whereas the 0–400 m layer – to kinetic energy. The conversion rates of the mean kinetic energy into the vortex kinetic one and the mean available potential energy into the vortex available potential one (barotropic and baroclinic instability) were analyzed. It is shown that the first type of transformation dominates in summer, while the second one is characterized by its increase in winter. Conclusions. The vertical profile shows that the kinetic energy of eddies in winter is higher than in summer. The available potential energy of a vortex is by an order of magnitude greater than the kinetic energy. An increase in the available potential energy is confirmed by a significant positive trend and by a decrease in the vortex Burger number. The graphs of the barotropic instability conversion rate demonstrate the multidirectional flows in the vortex zone with the dipole structure observed in a winter period, and the tripole one – in summer. The barotropic instability highest intensity is observed in summer. The baroclinic instability is characterized by intensification of the regime in winter that is associated with weakening of stratification in this period owing to winter convection.

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