scholarly journals A New Model Approach for Convective Wall Heat Losses in DQMOM-IEM Simulations for Turbulent Reactive Flows

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Yeshaswini Emmi ◽  
Andreas Fiolitakis ◽  
Manfred Aigner ◽  
Franklin Genin ◽  
Khawar Syed
Keyword(s):  
Experimental Data ◽  
Heat Losses ◽  
Reacting Flow ◽  
Jet Flame ◽  
New Model ◽  
Turbulent Reactive Flows ◽  
Novel Method ◽  
The One ◽  
The Impact ◽  
Model Approach

A new model approach is presented in this work for including convective wall heat losses in the direct quadrature method of moments (DQMoM) approach, which is used here to solve the transport equation of the one-point, one-time joint thermochemical probability density function (PDF). This is of particular interest in the context of designing industrial combustors, where wall heat losses play a crucial role. In the present work, the novel method is derived for the first time and validated against experimental data for the thermal entrance region of a pipe. The impact of varying model-specific boundary conditions is analyzed. It is then used to simulate the turbulent reacting flow of a confined methane jet flame. The simulations are carried out using the DLR in-house computational fluid dynamics code THETA. It is found that the DQMoM approach presented here agrees well with the experimental data and ratifies the use of the new convective wall heat losses model.

scholarly journals A New Model Approach for Convective Wall Heat Losses in DQMoM-IEM Simulations for Turbulent Reactive Flows

2018 ◽  
Author(s):  
Yeshaswini Emmi ◽  
Andreas Fiolitakis ◽  
Manfred Aigner ◽  
Franklin Genin ◽  
Khawar Syed
Keyword(s):  
Experimental Data ◽  
Heat Losses ◽  
Reacting Flow ◽  
Jet Flame ◽  
New Model ◽  
Turbulent Reactive Flows ◽  
Novel Method ◽  
The One ◽  
The Impact ◽  
Model Approach

A new model approach is presented in this work for including convective wall heat losses in the Direct Quadrature Method of Moments (DQMoM) approach, which is used here to solve the transport equation of the one-point, one-time joint thermochemical probability density function (PDF). This is of particular interest in the context of designing industrial combustors, where wall heat losses play a crucial role. In the present work, the novel method is derived for the first time and validated against experimental data for the thermal entrance region of a pipe. The impact of varying model-specific boundary conditions is analysed. It is then used to simulate the turbulent reacting flow of a confined methane jet flame. The simulations are carried out using the DLR in-house Computational Fluid Dynamics (CFD) code THETA. It is found that the DQMoM approach presented here agrees well with the experimental data and ratifies the use of the new convective wall heat losses model.

scholarly journals THE IMPACT OF THE SOLAR WALL ON THE EXTERNAL ENVELOPE / SAULĖS SIENOS ĮTAKOS PASTATO ATITVAROMS ANALIZĖ

2014 ◽  
Vol 6 (4) ◽  
pp. 438-443
Author(s):  
Violeta Motuzienė
Keyword(s):  
Experimental Data ◽  
Solar Collector ◽  
Negative Influence ◽  
Positive Influence ◽  
Heat Losses ◽  
Comsol Multiphysics ◽  
Heating Season ◽  
The One ◽  
Solar Wall ◽  
The Impact

The paper analyses the influence of the solar wall (unglazed transpired solar collector) on the external envelope during heating and non-heating seasons. Experiments were performed in two rooms – the one with a solar wall and without it. Based on experimental data, the analysis of the influence of the solar wall on the external envelope was done for two cases: employing air by-pass and refusing it. Also, the numerical simulation of the solar wall employing “COMSOL Multiphysics” software was performed. 8 different alternatives were simulated thus seeking to define the ways to decrease a negative and increase a positive influence of the solar wall on the external envelope of the building both in heating and non-heating seasons. The obtained results have shown that the solar wall makes a negative influence on the envelope during the non-heating season if air by-pass is not used. Heat gains increase by 8–12.2%, compared to the case without the solar wall. It has been also defined that the solar wall protects the envelope from heat gains if air by-pass is applied. During the heating season, the solar wall may decrease heat losses by 25.5%, compared to the case without the wall. Straipsnyje nagrinėjama saulės sienos (neįstiklinto pratakaus saulės kolektoriaus) įtaka išorinei atitvarai šiltuoju ir šaltuoju metų laiku. Eksperimentinis tyrimas buvo atliktas dviejose patalpose: vienoje – išorinė atitvara dengta, o kitoje – nedengta saulės siena. Remiantis gautais eksperimentiniais ir meteorologiniais duomenimis atlikta saulės sienos poveikio atitvarai ir jos priklausomybės nuo saulės spinduliuotės intensyvumo su oro apeiga ir be jos analizė. Saulės siena modeliuota su „COMSOL Multiphysics“ programa. Sumodeliuoti aštuoni skirtingi atitvaros su saulės siena variantai, siekiant nustatyti būdus, kaip sumažinti neigiamą ir padidinti teigiamą įtaką atitvarai šiltuoju ir šaltuoju metų laiku. Nustatyta, kad saulės siena šiltuoju metų laiku, kai oras joje nejuda, daro neigiamą įtaką atitvarai – šilumos pritėkiai padidėja 8–12,2 %, lyginant su nedengta atitvara. Analizė parodė, kad saulės siena apsaugo atitvarą nuo tiesioginės saulės spinduliuotės, jei oras ištraukiamas per apėjimo ortakį. Šaltuoju metų laiku saulės siena šilumos nuostolius sumažina 25,5 %, lyginant su nedengta išorine atitvara.

Comparative Validation Study on Identification of Premixed Flame Transfer Function

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Luis Tay-Wo-Chong ◽  
Sebastian Bomberg ◽  
Ahtsham Ulhaq ◽  
Thomas Komarek ◽  
Wolfgang Polifke
Keyword(s):  
Experimental Data ◽  
Transfer Function ◽  
Turbulent Flame ◽  
Maximum Amplitude ◽  
Quantitative Agreement ◽  
Combustion Model ◽  
Reacting Flow ◽  
Phase Lag ◽  
Dynamics Simulations ◽  
The Impact

The flame transfer function (FTF) of a premixed swirl burner was identified from a time series generated with computational fluid dynamics simulations of compressible, turbulent, reacting flow at nonadiabatic conditions. Results were validated against experimental data. For large eddy simulation (LES), the dynamically thickened flame combustion model with one step kinetics was used. For unsteady simulation in a Reynolds-averaged Navier–Stokes framework (URANS), the Turbulent Flame Closure model was employed. The FTF identified from LES shows quantitative agreement with experiment for amplitude and phase, especially for frequencies below 200 Hz. At higher frequencies, the gain of the FTF is underpredicted. URANS results show good qualitative agreement, capturing the main features of the flame response. However, the maximum amplitude and the phase lag of the FTF are underpredicted. Using a low-order network model of the test rig, the impact of the discrepancies in predicted FTFs on frequencies and growth rates of the lowest order eigenmodes were assessed. Small differences in predicted FTFs were found to have a significant impact on stability limits. Stability behavior in agreement with experimental data was achieved only with the LES-based flame transfer function.

Comparative Validation Study on Identification of Premixed Flame Transfer Function

2011 ◽  
Author(s):  
Luis Tay-Wo-Chong ◽  
Sebastian Bomberg ◽  
Ahtsham Ulhaq ◽  
Thomas Komarek ◽  
Wolfgang Polifke
Keyword(s):  
Experimental Data ◽  
Transfer Function ◽  
Cfd Simulation ◽  
Turbulent Flame ◽  
Maximum Amplitude ◽  
Quantitative Agreement ◽  
Combustion Model ◽  
Reacting Flow ◽  
Phase Lag ◽  
The Impact

The flame transfer function (FTF) of a premixed swirl burner was identified from time series generated with CFD simulation of compressible, turbulent, reacting flow at non-adiabatic conditions. Results were validated against experimental data. For large eddy simulation (LES), the Dynamically Thickened Flame combustion model with one step kinetics was used. For unsteady simulation in a Reynolds-averaged Navier-Stokes framework (URANS), the Turbulent Flame Closure model was employed. The FTF identified from LES shows quantitative agreement with experiment for amplitude and phase, especially for frequencies below 200 Hz. At higher frequencies, the gain of the FTF is underpredicted. URANS results show good qualitative agreement, capturing the main features of the flame response. However, the maximum amplitude and the phase lag of the FTF are underpredicted. Using a low-order network model of the test rig, the impact of the discrepancies in predicted FTFs on frequencies and growth rates of the lowest order eigenmodes were assessed. Small differences in predicted FTFs were found to have a significant impact on stability limits. Stability behavior in agreement with experimental data was achieved only with the LES-based flame transfer function.

Numerical Solution for Two-Dimensional Elastic Wave Propagation in Finite Bars

1967 ◽  
Vol 34 (3) ◽  
pp. 725-734 ◽  
Author(s):  
L. D. Bertholf
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Numerical Solutions ◽  
Step Change ◽  
Two Dimensional ◽  
One Dimensional ◽  
Elastic Bar ◽  
The One ◽  
The Impact

Numerical solutions of the exact equations for axisymmetric wave propagation are obtained with continuous and discontinuous loadings at the impact end of an elastic bar. The solution for a step change in stress agrees with experimental data near the end of the bar and exhibits a region that agrees with the one-dimensional strain approximation. The solution for an applied harmonic displacement closely approaches the Pochhammer-Chree solution at distances removed from the point of application. Reflections from free and rigid-lubricated ends are studied. The solutions after reflection are compared with the elementary one-dimensional stress approximation.

scholarly journals Quantifying the Impact of the Covid-19 Lockdown Measures on Nitrogen Dioxide Levels throughout Europe

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 131
Author(s):  
Sverre Solberg ◽  
Sam-Erik Walker ◽  
Philipp Schneider ◽  
Cristina Guerreiro
Keyword(s):  
Nitrogen Dioxide ◽  
Temporal Trends ◽  
Measurement Data ◽  
Additive Model ◽  
Generalised Additive Model ◽  
The Difference ◽  
The One ◽  
The Impact ◽  
Good Agreement ◽  
Model Approach

In this paper, the effect of the lockdown measures on nitrogen dioxide (NO2) in Europe is analysed by a statistical model approach based on a generalised additive model (GAM). The GAM is designed to find relationships between various meteorological parameters and temporal metrics (day of week, season, etc.) on the one hand and the level of pollutants on the other. The model is first trained on measurement data from almost 2000 monitoring stations during 2015–2019 and then applied to the same stations in 2020, providing predictions of expected concentrations in the absence of a lockdown. The difference between the modelled levels and the actual measurements from 2020 is used to calculate the impact of the lockdown measures adjusted for confounding effects, such as meteorology and temporal trends. The study is focused on April 2020, the month with the strongest reductions in NO2, as well as on the gradual recovery until the end of July. Significant differences between the countries are identified, with the largest NO2 reductions in Spain, France, Italy, Great Britain and Portugal and the smallest in eastern countries (Poland and Hungary). The model is found to perform best for urban and suburban sites. A comparison between the found relative changes in urban surface NO2 data during the lockdown and the corresponding changes in tropospheric vertical NO2 column density as observed by the TROPOMI instrument on Sentinel-5P revealed good agreement despite substantial differences in the observing method.

scholarly journals THE ANALYSIS OF THE VILLAGE LAW IMPLEMENTATION POLICY BY USING EDWARD III MODEL APPROACH IN GARUT

2019 ◽  
Author(s):  
Ikeu Kania ◽  
Gugun Geusan ◽  
Leadya Raturahmi ◽  
Aceng Ulumudin ◽  
Erna Rustiana ◽  
...  
Keyword(s):  
Analysis Technique ◽  
Edward Iii ◽  
Bureaucratic Structure ◽  
The One ◽  
Lack Of Commitment ◽  
And Function ◽  
The Impact ◽  
The Village ◽  
Goals And Objectives ◽  
Model Approach

The equitable, prosperous, and independent village development that have not realized is the main problem of this study. The existence of Law no 6 of 2014 on Villages on the one hand is a hope but on the other hand becomes a challenge that must be built in a collaborative synergy between stakeholders or the elements of society in order to achieve the vision and mission of community independence and prosperity. In Karangpawitan Subdistrict there are several obstacles in implementing Law No. 6 of 2014 on Villages. The obstacles are the lack of human resource who understands the laws, the lack of conducive communication, and complicated and unclear bureaucratic structure and disposition of the main duties and functions of each village officials which make the impact on nontransparent and unaccountable public service. The method research used was qualitative approach with case study. The data was collected by doing observation and deep interview with the informant. The data analysis technique was Edward III Model approach by analyzing the factors that influence the implementation of policies, such as: (1) Communication; (2) Resources; (3) Disposition; and (4) Bureaucratic Structure. The result of this research showed that there were several factors that should be improved and noticed in Dimension of Communication. The factors were goals and objectives, understanding and socialization form in order to achieve the goals and objectives that have been made. Furthermore, the Dimensions of Resources related to the competence of the village officials is the main problem and financial resources. The dimension of disposition is the character and characteristics possessed by implementers, such as lack of commitment, honesty, and ways of accepting the others’ opinions. The last is the dimension of bureaucratic structure. It is the task, principal and function of the village officials which have not been optimal. Keywords: Public Policy, Village Development, Public Welfare

A Novel Method for the Rapid Purification of Human and Rat Fibrin(OGEN) Degradation Products in High Yields

1979 ◽  
Author(s):  
W. Nieuwenhuizen ◽  
I. A. M. van Ruijven-Vermeer ◽  
F. Haverkate ◽  
G. Timan
Keyword(s):  
Degradation Products ◽  
Complete Separation ◽  
Purification Method ◽  
Amino Terminal ◽  
Novel Method ◽  
Rapid Purification ◽  
The One ◽  
High Yields ◽  
Size Heterogeneity ◽  
D Dimer

A novel method will be described for the preparation and purification of fibrin(ogen) degradation products in high yields. The high yields are due to two factors. on the one hand an improved preparation method in which the size heterogeneity of the degradation products D is strongly reduced by plasmin digestion at well-controlled calcium concentrations. At calcium concentrations of 2mM exclusively D fragments, M.W.= 93-000 (Dcate) were formed; in the presence of 1OmM EGTA only fragments M.W.= 80.000 (D EGTA) were formed as described. on the other hand a new purification method, which includes Sephadex G-200 filtration to purify the D:E complexes and separation of the D and E fragments by a 16 hrs. preparative isoelectric focussing. The latter step gives a complete separation of D (fragments) (pH = 6.5) and E fragments (at pH = 4.5) without any overlap, thus allowing a nearly 100% recovery in this step. The overall recoveries are around 75% of the theoretical values. These recoveries are superior to those of existing procedures. Moreover the conditions of this purification procedure are very mild and probably do not affect the native configuration of the products. Amino-terminal amino acids of human Dcate, D EGTA and D-dimer are identical i.e. val, asx and ser. in the ratgly, asx and ser were found. E 1% for rat Dcate=17-8 for rat D EGTA=16.2 and for rat D- dimer=l8.3. for the corresponding human fragments, these values were all 20.0 ± 0.2.

Static and Dynamic Studies of Gasoline in View of its Octane Number and its Toxic Effect

2013 ◽  
Vol 12 (7) ◽  
pp. 451-459
Author(s):  
Ashraf Yehia El-Naggar ◽  
Mohamed A. Ebiad
Keyword(s):  
Toxic Effect ◽  
Aromatic Hydrocarbons ◽  
Octane Number ◽  
Liquid Fuel ◽  
Positive Impact ◽  
Hydrocarbon Composition ◽  
Different Temperatures ◽  
Different Seasons ◽  
The One ◽  
The Impact

Gasoline come primarily from petroleum cuts, it is the preferred liquid fuel in our lives. Two gasoline samples of octane numbers 91 and 95 from Saudi Arabia petrol stations were studied. This study was achieved at three different temperatures 20oC, 30oC and 50oC representing the change in temperatures of the different seasons of the year. Both the evaporated gases of light aromatic hydrocarbons (BTEX) of gasoline samples inside the tank were subjected to analyze qualitatively and quantitatively via capillary gas chromatography. The detailed hydrocarbon composition and the octane number of the studied gasoline samples were determined using detailed hydrocarbon analyzer. The idea of research is indicating the impact of light aromatic compounds in gasoline on the toxic effect of human and environment on the one hand, and on octane number of gasoline on the other hand. Although the value of octane number will be reduced but this will have a positive impact on the environment as a way to produce clean fuel.

Near-Perfect Reconstruction Oversampled Nonuniform Cosine-Modulated Filter Banks Based on Frequency Warping and Subband Merging

2012 ◽  
Vol 58 (2) ◽  
pp. 177-192 ◽  
Author(s):  
Marek Parfieniuk ◽  
Alexander Petrovsky
Keyword(s):  
Group Delay ◽  
Filter Banks ◽  
Main Idea ◽  
Perceptual Processing ◽  
Perfect Reconstruction ◽  
Frequency Warping ◽  
Small Loss ◽  
Novel Method ◽  
The One ◽  
Near Perfect Reconstruction

Near-Perfect Reconstruction Oversampled Nonuniform Cosine-Modulated Filter Banks Based on Frequency Warping and Subband MergingA novel method for designing near-perfect reconstruction oversampled nonuniform cosine-modulated filter banks is proposed, which combines frequency warping and subband merging, and thus offers more flexibility than known techniques. On the one hand, desirable frequency partitionings can be better approximated. On the other hand, at the price of only a small loss in partitioning accuracy, both warping strength and number of channels before merging can be adjusted so as to minimize the computational complexity of a system. In particular, the coefficient of the function behind warping can be constrained to be a negative integer power of two, so that multiplications related to allpass filtering can be replaced with more efficient binary shifts. The main idea is accompanied by some contributions to the theory of warped filter banks. Namely, group delay equalization is thoroughly investigated, and it is shown how to avoid significant aliasing by channel oversampling. Our research revolves around filter banks for perceptual processing of sound, which are required to approximate the psychoacoustic scales well and need not guarantee perfect reconstruction.

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