On the inverse kinetic energy cascade in premixed isotropic turbulent flames

2021 ◽  
pp. 2250015
Author(s):  
Xiang Qian ◽  
Hao Lu ◽  
Chun Zou ◽  
Hong Yao
Keyword(s):  
Energy Transfer ◽  
Kinetic Energy ◽  
A Priori ◽  
Reacting Flows ◽  
Turbulent Flames ◽  
Energy Cascade ◽  
Positive Pressure ◽  
Turbulent Reacting Flows ◽  
Using Data ◽  
Stress Models

The understanding of energy transfer in fluids is important for the accurate modeling of turbulent reacting flows. In this study, we investigate interscale kinetic energy transfer and subgrid-scale (SGS) backscatter using data from direct numerical simulations (DNSs) of premixed isotropic turbulent flames. Results reveal that in the examined premixed flames, the pressure transfer term appearing in the transport equation of turbulent kinetic energy dominates the nonlinear advection and the dissipation at large scales, and noticeably contributes to the inverse kinetic energy cascade. Filtered DNS data show that SGS backscatter is correlated with the appearance of positive pressure-dilatation work, i.e. thermal expansion. A priori test results of three SGS stress models reveal that the Smagorinsky stress model is unable to capture SGS backscatter, but that two nonlinear structural stress models are able to predict SGS backscatter.

scholarly journals Spectral kinetic energy transfer in turbulent premixed reacting flows

2016 ◽  
Vol 93 (5) ◽  
Author(s):  
C. A. Z. Towery ◽  
A. Y. Poludnenko ◽  
J. Urzay ◽  
J. O'Brien ◽  
M. Ihme ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Kinetic Energy ◽  
Reacting Flows ◽  
Kinetic Energy Transfer ◽  
Turbulent Premixed

SELECTION OF COINCIDENCE ELECTRON-PROTON EVENTS IN NUCLEI INTERACTION

2019 ◽  
Vol 53 (1 (248)) ◽  
pp. 53-59
Author(s):  
D.A. Martiryan
Keyword(s):  
Electron Beam ◽  
Energy Transfer ◽  
Kinetic Energy ◽  
Energy Distribution ◽  
Momentum Distribution ◽  
Virtual Photon ◽  
Kinetic Energy Distribution ◽  
Coordinate Frame ◽  
Using Data ◽  
Selection Of

The main goal of this analysis is to study momentum (or kinetic energy) distribution of the backward going protons using data from CLAS EG2 experiment at Jefferson Lab. In this experiment scattering of a 5.014 GeV electron beam off various nucleus targets, ranging from deuterium to lead, have been recorded. The analysis includes selection of events in the reaction $ A(e, e^{\prime}, P_{back}) X $, where $ P_{back} $ is a proton scattered above 90° either in the lab coordinate frame or with respect to the direction of the interacting virtual photon, then performing required corrections and studying the protons momentum distribution as a function of energy transfer. In this paper identification of electron-proton events is presented.

Importance of Turbulence-Radiation Interactions in Turbulent Reacting Flows

2002 ◽  
Author(s):  
Genong Li ◽  
Michael F. Modest
Keyword(s):  
Theoretical Work ◽  
Reacting Flows ◽  
Turbulent Flames ◽  
Radiative Properties ◽  
Nonlinear Dependence ◽  
Turbulent Reacting Flows ◽  
Radiative Fluxes ◽  
Strongly Nonlinear ◽  
Complete Absorption ◽  
Function Correlation

Traditional modeling of radiative transfer in reacting flows has ignored turbulence-radiation interactions (TRI). Radiative fluxes, flux divergences and radiative properties have been based on mean temperature and concentration fields. However, both experimental and theoretical work have suggested that mean radiative quantities may differ significantly from those predictions based on the mean parameters because of their strongly nonlinear dependence on the temperature and concentration fields. The composition PDF method is able to consider many nonlinear interactions rigorously, and the method is used here to study turbulence-radiation interactions. This paper tries to answer two basic questions: (1) whether turbulence-radiation interactions are important in turbulent flames or not; (2) if they are important, then what correlations need to be considered in the simulation to capture them. After conducting many flame simulations, it was observed that, on average, TRI effects account for about 1/3 of the total drop in flame peak temperature caused by radiative heat losses. In addition, this study shows that consideration of the temperature self correlation alone is not sufficient to capture TRI, but that the complete absorption coefficient–Planck function correlation must be considered.

scholarly journals Numerical Simulation of Turbulent Flames based on a Hybrid RANS/Transported-PDF Method and REDIM Method

2018 ◽  
Vol 20 (1) ◽  
pp. 23 ◽  
Author(s):  
Chunkan Yu ◽  
Felipe Minuzzi ◽  
Ulrich Maas
Keyword(s):  
Chemical Kinetics ◽  
Reaction Diffusion ◽  
Reacting Flows ◽  
Computational Effort ◽  
Turbulent Flames ◽  
Moderate Degree ◽  
Turbulent Reacting Flows ◽  
Detailed Chemical Kinetics ◽  
Pdf Model ◽  
Detailed Chemical

A hybrid RANS/Transported-PDF model for the simulation of turbulent reacting flows based on automatically reduced mechanisms for the chemical kinetics (reaction-diffusion manifold, REDIM) is presented in this work. For modelling of turbulent reacting flows, chemistry is a key problem and affects largely the accuracy. The PDF method has been widely used since the chemical source term is in a closed form, without any modelling. Despite of this advantage of PDF method, detailed chemical kinetics is not desired due to its heavy computational effort. From this aspect, the detailed chemical kinetics is simplified by the reaction-diffusion manifold (REDIM) method. The hybrid RANS/Transported-PDF model based on REDIM reduced kinetics is applied to simulate the Sandia piloted Flame E, which has a moderate degree of local extinction. The numerical results are validated through comparison with experimental data and show good qualitative and quantitative agreements.

Recognizing Job Apathy Patterns of Iraqi Higher Education Employees Using Data Mining Techniques

2019 ◽  
Vol 54 (4) ◽  
Author(s):  
Mustafa S. Abd ◽  
Suhad Faisal Behadili
Keyword(s):  
Higher Education ◽  
Data Mining ◽  
Psychiatric Patients ◽  
Human Life ◽  
A Priori ◽  
Psychological Research ◽  
Attribute Selection ◽  
Specific Class ◽  
Data Mining Techniques ◽  
Using Data

Psychological research centers help indirectly contact professionals from the fields of human life, job environment, family life, and psychological infrastructure for psychiatric patients. This research aims to detect job apathy patterns from the behavior of employee groups in the University of Baghdad and the Iraqi Ministry of Higher Education and Scientific Research. This investigation presents an approach using data mining techniques to acquire new knowledge and differs from statistical studies in terms of supporting the researchers’ evolving needs. These techniques manipulate redundant or irrelevant attributes to discover interesting patterns. The principal issue identifies several important and affective questions taken from a questionnaire, and the psychiatric researchers recommend these questions. Useless questions are pruned using the attribute selection method. Moreover, pieces of information gained through these questions are measured according to a specific class and ranked accordingly. Association and a priori algorithms are used to detect the most influential and interrelated questions in the questionnaire. Consequently, the decisive parameters that may lead to job apathy are determined.

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