scholarly journals A Model for Fuel Spray Formation with Atomizing Air

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 20
Author(s):  
David J. Schmidt ◽  
William Kvasnak ◽  
Goodarz Ahmadi
Keyword(s):  
Swirling Flow ◽  
Shape Change ◽  
Fluid Velocity ◽  
Time Averaging ◽  
Mean Square ◽  
Spray Formation ◽  
Fuel Droplets ◽  
Mean Square Fluctuation ◽  
The Mean ◽  
Probability Density Function Pdf

The formation of a liquid spray emanating from a nozzle in the presence of atomizing air was studied using a computational model approach that accounted for the deformation and break up of droplets. Particular attention was given to the formation of sprays under non-swirling flow conditions. The instantaneous fluctuating fluid velocity and velocity gradient components were evaluated with the use of a probability density function (PDF)-based Langevin equation. Motions of atomized fuel droplets were analyzed, and ensemble and time averaging were used for evaluating the statistical properties of the spray. Effects of shape change of droplets, and their breakup, as well as evaporation, were included in the model. The simulation results showed that the mean-square fluctuation velocities of the droplets vary significantly with their size and shape. Furthermore, the mean-square fluctuation velocities of the evaporating droplet differed somewhat from non-evaporating droplets. Droplet turbulence diffusivities, however, were found to be close to the diffusivity of fluid point particles. The droplet velocity, concentration, and size of the simulated spray were compared with the experimental data and reasonable agreement was found.

Liquid Sheet Disintegration and Atomization Process on a Simplified Airblast Atomizer

1993 ◽  
Vol 115 (3) ◽  
pp. 461-466 ◽  
Author(s):  
G. Lavergne ◽  
P. Trichet ◽  
P. Hebrard ◽  
Y. Biscos
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Video Camera ◽  
Frequency Instability ◽  
Liquid Sheet ◽  
Processing Unit ◽  
Spray Formation ◽  
High Speed Video Camera ◽  
The Mean ◽  
Component Phase

Liquid sheet break-up in coflowing shear flow is the mean by which liquids are atomized in practical injectors for gas turbine combustors. The present study explores experimentally the mechanisms of liquid sheet instabilities and spray formation. Experiments are conducted on four airblast geometries. A high-speed video camera associated with an image processing unit was used to study the liquid sheet instabilities. A microphone and a frequency analyzer were used to track the disintegration frequency. Instability amplitude and disintegration length of the liquid sheet were measured. A two-component Phase Doppler Particle Analyzer was used to characterize the resultant spray. The spatial distribution of the particle size is influenced by the swirling flow field. These experimental results will be used to assess models of fuel sheet instabilities and disintegration.

Fluctuations in aqueous methanol, ethanol, and propan-1-ol: amplitude and wavelength of fluctuation

1999 ◽  
Vol 77 (12) ◽  
pp. 2039-2045 ◽  
Author(s):  
Y Koga
Keyword(s):  
Isentropic Compressibility ◽  
Volume Effect ◽  
Mean Square ◽  
Aqueous Methanol ◽  
Mean Square Fluctuation ◽  
Volume Entropy ◽  
The Mean ◽  
Excess Partial Molar Enthalpy ◽  
Derivatives Of ◽  
Alcohol Alcohol

Density, heat capacity, and isentropic compressibility data for aqueous methanol, ethanol, and propan-1-ol by Benson's group were used to evaluate two kinds of fluctuations; mean-square fluctuation densities; and (mean-square) normalized fluctuations, respectively, in volume, entropy, and cross (entropy/volume) effect. The mean-square fluctuation densitiesprovide measures for the amplitude (intensity) of the fluctuation, while the normalized fluctuations contain information regarding the wavelength (extensity) of the fluctuation. Furthermore, their composition derivatives, the partial molar fluctuationsof alcohols were calculated. These quantities signify the effect of additional solute on the respective fluctuations. These data were interpreted in terms of mixing schemes learned earlier in this laboratory by using the data of excess partial molar enthalpy, entropy, and volume, and the respective alcohol-alcohol interaction functions, i.e., the composition derivatives of partial molar quantities. Key words: aqueous methanol, ethanol, and propan-1-ol;fluctuation density; normalized fluctuation; partial molar fluctuations of alcohol.

Liquid Sheet Disintegration and Atomization Process on a Simplified Airblast Atomizer

1992 ◽  
Author(s):  
G. LaVergne ◽  
P. Trichet ◽  
P. Hebrard ◽  
Y. Biscos
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Video Camera ◽  
Frequency Instability ◽  
Liquid Sheet ◽  
Processing Unit ◽  
Spray Formation ◽  
High Speed Video Camera ◽  
The Mean ◽  
Component Phase

Liquid sheet break-up in co flowing shear flow is the mean by which liquids are atomized in practical injectors for gas turbine combustors. The present study explores experimentally the mechanisms of liquid sheet instabilities and spray formation. Experiments are conducted on four airblast geometries. A high speed video camera associated to an image processing unit was used to study the liquid sheet instabilities. A microphone and a frequency analyzer were used to track the disintegration frequency. Instability amplitude and disintegration lenght of the liquid sheet were measured. A two component Phase Doppler Particle Analyzer was used to characterize the resultant spray. The spatial distribution of the particle size is influenced by the swirling flow field. These experimental results will be used to assess models of fuel sheet instabilities and disintegration.

scholarly journals On fluctuations in electromagnetic radiation

1939 ◽  
Vol 170 (941) ◽  
pp. 252-265 ◽  
Keyword(s):  
Quantum Theory ◽  
Energy Density ◽  
Electromagnetic Radiation ◽  
Photoelectric Effect ◽  
Mean Square ◽  
Light Quanta ◽  
Mean Square Fluctuation ◽  
The Mean ◽  
General Thermodynamics

The question of fluctuations in electromagnetic radiation played an important part during the first period of the development of quantum theory. After having introduced (Einstein 1905) the conception of light quanta or photons in order to explain the observed phenomena of the photoelectric effect, Einstein (1909) considered the consequences of this idea for other properties of the radiation. Planck’s formula for the energy density of radiation implies, by arguments of general thermodynamics and statistics, the following expression for the mean square fluctuation of the energy contained in a volume v in terms of the mean energy Ē v .

Response Statistics of a Beam-Mass Oscillator Under Combined Harmonic and Random Excitation

1995 ◽  
Vol 1 (2) ◽  
pp. 225-247 ◽  
Author(s):  
Stephen Ekwaro-Osire ◽  
Atila Ertas
Keyword(s):  
Steady State ◽  
Harmonic Component ◽  
Stochastic Averaging ◽  
Random Excitation ◽  
Stochastic Averaging Method ◽  
Time Averaging ◽  
Mean Square ◽  
Mean Square Response ◽  
The Mean ◽  
Non Gaussian

In the present study, the response statistics of a beam-mass oscillator under combined harmonic and random excitation were investigated. The Gaussian and non-Gaussian closure schemes, in conjunction with the stochastic averaging method, were used to solve for the mean square response. The influence of the oscillator parameters on the response statistics was studied. The harmonic component of the excitation was observed to manifest itself, as an oscillation, in the steady-state mean square response. Results obtained showed that the non-Gaussian solution yields higher steady-state mean square responses than those obtained from the Gaussian solution. It was further shown that the harmonic time-varying properties of the oscillator are preserved by omitting the time-averaging in the stochastic averaging procedure.

Experimental Investigation of Confined Swirling Flow and Its Interaction With a Bluff Body

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Zhang Tianxing ◽  
Mohamed Alshehhi ◽  
Lyes Khezzar ◽  
Yakang Xia ◽  
Nabil Kharoua
Keyword(s):  
Flow Structure ◽  
Pipe Flow ◽  
Laser Doppler Velocimetry ◽  
Bluff Body ◽  
Swirling Flow ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Doppler Velocimetry ◽  
Mean Square ◽  
The Mean

Abstract Detailed laser Doppler velocimetry (LDV) measurements of profiles of mean axial and tangential velocities and their corresponding root-mean-square (RMS) components in confined turbulent swirling pipe flow with and without the presence of a conical bluff body have been conducted. The working fluid was water and the Reynolds number based on the bulk velocity inside the pipe was equal to 40,850. The main focus of the study was to document the interaction between turbulent swirling flow inside a pipe and in the presence of a conical bluff body. The flow structure was found in all cases to be composed of a forced-free vortex. The swirl decay was exponential for Reynolds numbers of 40,850 and 14,450. The effect of the presence of the bluff body on the flow is limited to a short region upstream of it; so that the effect on the flow structure and strength of swirl upstream can be considered negligible. The flow around the bluff body adopts a different structure where the mean axial and tangential velocities tend to assume uniform profiles with turbulence activity limited to the region close to the surface of the bluff body.

scholarly journals Fluctuating Order Parameter in Doped Cuprate Superconductors

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3607-3611 ◽  
Author(s):  
V. M. Loktev ◽  
Yu. G. Pogorelov ◽  
V. M. Turkowski
Keyword(s):  
Doping Level ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
Superconducting Order Parameter ◽  
Mean Square ◽  
Spatial Correlations ◽  
In Doping ◽  
Mean Square Fluctuation ◽  
The Mean ◽  
D Wave

We discuss the static fluctuations of the d-wave superconducting order parameter Δ in CuO 2 planes, due to quasiparticle scattering by charged dopants. The analysis of two-particle anomalous Green functions at T = 0 permits to estimate the mean-square fluctuation δ2 = <Δ2> - <Δ>2, averaged in random dopant configurations, to the lowest order in doping level c. Since Δ is found to saturate with growing doping level while δ remains to grow, this can explain the collapse of Tc at overdoping. Also we consider the spatial correlations <Δ(0)Δ(R)> for order parameter in different points of the plane.

Experiments and Large Eddy Simulation of Swirling Flow in a Pipe

2018 ◽  
Author(s):  
Zhang Tianxing ◽  
Nabil Kharoua ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Shrinivas Bojanampati
Keyword(s):  
Kinetic Energy ◽  
Large Eddy Simulation ◽  
Swirling Flow ◽  
Fluid Velocity ◽  
Tangential Velocity ◽  
Scale Model ◽  
Axial Distance ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean

Swirling flows in pipes are encountered in several industrial applications for separation or mixing purposes. In this work turbulent swirling flow is generated using a new swirl generator in the form of thick-walled pipe with multi-radial holes which is lodged inside a larger cylindrical housing, called the Swirl Cage. The swirling flow exiting from the Swirl Cage feeds into a long pipe where the Reynolds number based on the pipe diameter and average velocity is equal to 40836.67. Large Eddy Simulation (LES) is used to calculate the swirling flow and explore its characteristics in conjunction with the Dynamic Kinetic Energy Subgrid-Scale model. Experiments were conducted using LDV and the results are used for validation purposes and for the discussion of the flow features. The results are discussed in relation with the mean fluid velocity and its RMS component. Profiles of the mean tangential velocity reveal a Rankine vortex swirling flow type along the whole axial distance. The core flow was slightly oscillating exhibiting a processing vortex behavior reflected by the radial velocities at the centerline. The profiles of the turbulent kinetic energy were characterized by a peak at the centerline increasing in magnitude with the axial distance. The swirl number decayed from 1.5 right at the outlet of the swirl cage to unity close to the outlet of the pipe.

Asymmetric X-ray line broadening of plastically deformed crystals. I. Theory

1988 ◽  
Vol 21 (1) ◽  
pp. 47-54 ◽  
Author(s):  
I. Groma ◽  
T. Ungár ◽  
M. Wilkens
Keyword(s):  
Dislocation Density ◽  
Mean Square ◽  
Line Profiles ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Dislocation Density ◽  
Mean Square Fluctuation ◽  
The Mean ◽  
Dipole Polarization

X-ray diffraction line profiles of plastically deformed Cu single crystals orientated for ideal multiple slip were recently found to be markedly asymmetric. A theory is developed to interpret this kind of asymmetric line broadening in terms of the average dislocation density, the dipole polarization of the dislocation structure and the mean square fluctuation of the dislocation density.

CORRELATIONS OF PITCHES IN MUSIC

Fractals ◽  
1996 ◽  
Vol 04 (04) ◽  
pp. 547-553 ◽  
Author(s):  
YU SHI
Keyword(s):  
Power Spectrum ◽  
Long Range ◽  
Power Law ◽  
Piano Music ◽  
Fundamental Principle ◽  
Mean Square ◽  
Scaling Exponents ◽  
One Dimensional ◽  
Mean Square Fluctuation ◽  
The Mean

We investigate correlations among pitches in several songs and pieces of piano music. Real values of tones are mapped to positions within a one-dimensional walk. The structure of music, such as beat, measure and stanza, are reflected in the change of scaling exponents of the mean square fluctuation. Usually the pitches within one beat are nearly random, while nontrivial correlations are found within duration around a measure; for longer duration the mean square fluctuation is nearly flat, indicating exact 1/f power spectrum. Some interesting features are observed. Correlations are also studied by treating different tones as different symbols. This kind of correlation cannot reflect the structure of music, though long-range power-law is also discovered. Our results support the viewpoint that the fundamental principle of music is the balance between repetition and contrast.

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