• Title/Summary/Keyword: G-Equation

Search Result 1,685, Processing Time 0.033 seconds

Large Eddy Simulation of Turbulent Premixed Flame in Turbulent Channel Flow

  • Ko Sang-Cheol;Park Nam-Seob
    • Journal of Mechanical Science and Technology
    • /
    • v.20 no.8
    • /
    • pp.1240-1247
    • /
    • 2006
  • Large eddy simulation of turbulent premixed flame in turbulent channel flow is studied by using G-equation. A flamelet model for the premixed flame is combined with a dynamic subgrid combustion model for the filtered propagation flame speed. The objective of this work is to investigate the validity of the dynamic subgrid G-equation model to a complex turbulent premixed flame. The effect of model parameters of the dynamic sub grid G-equation on the turbulent flame speed is investigated. In order to consider quenching of laminar flames on the wall, wall-quenching damping function is employed in this calculation. In the present study, a constant density turbulent channel flow is used. The calculation results are evaluated by comparing with the DNS results of Bruneaux et al.

ON THE SUPERSTABILITY OF THE p-RADICAL SINE TYPE FUNCTIONAL EQUATIONS

  • Kim, Gwang Hui
    • The Pure and Applied Mathematics
    • /
    • v.28 no.4
    • /
    • pp.387-398
    • /
    • 2021
  • In this paper, we will find solutions and investigate the superstability bounded by constant for the p-radical functional equations as follows: $f\(\sqrt[p]{\frac{x^p+y^p}{2}}\)^2-f\(\sqrt[p]{\frac{x^p-y^p}{2}}\)^2=\;\{(i)\;f(x)f(y),\\(ii)\;g(x)f(y),\\(iii)\;f(x)g(y),\\(iv)\;g(x)g(y).$ with respect to the sine functional equation, where p is an odd positive integer and f is a complex valued function. Furthermore, the results are extended to Banach algebra.

ON THE DIFFERENCE EQUATION $x_{n+1}=\frac{a+bx_{n-k}-cx_{n-m}}{1+g(x_{n-l})}$

  • Zhang, Guang;Stevic, Stevo
    • Journal of applied mathematics & informatics
    • /
    • v.25 no.1_2
    • /
    • pp.201-216
    • /
    • 2007
  • In this paper we consider the difference equation $$x_{n+1}=\frac{a+bx_{n-k}\;-\;cx_{n-m}}{1+g(x_{n-l})}$$ where a, b, c are nonegative real numbers, k, l, m are nonnegative integers and g(x) is a nonegative real function. The oscillatory and periodic character, the boundedness and the stability of positive solutions of the equation is investigated. The existence and nonexistence of two-period positive solutions are investigated in details. In the last section of the paper we consider a generalization of the equation.

Application of G-equation to large eddy simulation of turbulent premixed flame around a bluff body inside a cylindrical chamber (G 방정식을 이용한 실린더 챔버 내부 둔각물체 주위의 난류 예 혼합 화염 해석)

  • Choi Chang-Yong;Park Nam-Seob;Ko Sang-Cheol
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.29 no.4
    • /
    • pp.391-398
    • /
    • 2005
  • In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.

ON THE CONFORMAL DEFORMATION OVER WARPED PRODUCT MANIFOLDS

  • YOON-TAE JUNG;CHEOL GUEN SHIN
    • The Pure and Applied Mathematics
    • /
    • v.4 no.1
    • /
    • pp.27-33
    • /
    • 1997
  • Let (M = B$\times$f F, g) be an ($n \geq3$ )-dimensional differential manifold with Riemannian metric g. We solve the following elliptic nonlinear partial differential equation (equation omitted). where $\Delta_{g}$ is the Laplacian in the $\Delta$g-metric and ($h(\chi)$) is the scalar curvature of g and ($H(\chi)$) is a function on M.

  • PDF

Empirical Bayes Problem With Random Sample Size Components

  • Jung, Inha
    • Journal of the Korean Statistical Society
    • /
    • v.20 no.1
    • /
    • pp.67-76
    • /
    • 1991
  • The empirical Bayes version involves ″independent″ repetitions(a sequence) of the component decision problem. With the varying sample size possible, these are not identical components. However, we impose the usual assumption that the parameters sequence $\theta$=($\theta$$_1$, $\theta$$_2$, …) consists of independent G-distributed parameters where G is unknown. We assume that G $\in$ g, a known family of distributions. The sample size $N_i$ and the decisin rule $d_i$ for component i of the sequence are determined in an evolutionary way. The sample size $N_1$ and the decision rule $d_1$$\in$ $D_{N1}$ used in the first component are fixed and chosen in advance. The sample size $N_2$and the decision rule $d_2$ are functions of *see full text($\underline{X}^1$equation omitted), the observations in the first component. In general, $N_i$ is an integer-valued function of *see full text(equation omitted) and, given $N_i$, $d_i$ is a $D_{Ni}$/-valued function of *see full text(equation omitted). The action chosen in the i-th component is *(equation omitted) which hides the display of dependence on *(equation omitted). We construct an empirical Bayes decision rule for estimating normal mean and show that it is asymptotically optimal.

  • PDF

ON THE SUPERSTABILITY OF SOME PEXIDER TYPE FUNCTIONAL EQUATION II

  • Kim, Gwang-Hui
    • The Pure and Applied Mathematics
    • /
    • v.17 no.4
    • /
    • pp.397-411
    • /
    • 2010
  • In this paper, we will investigate the superstability for the sine functional equation from the following Pexider type functional equation: $f(x+y)-g(x-y)={\lambda}{\cdot}h(x)k(y)$ ${\lambda}$: constant, which can be considered an exponential type functional equation, the mixed functional equation of the trigonometric function, the mixed functional equation of the hyperbolic function, and the Jensen type equation.

High-resolution Capacitive Microaccelerometers using Branched finger Electrodes with High-Amplitude Sense Voltage (고감지전압 및 가지전극을 이용한 고정도 정전용량형 미소가속도계)

  • 한기호;조영호
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.28 no.1
    • /
    • pp.1-10
    • /
    • 2004
  • This paper presents a navigation garde capacitive microaccelerometer, whose low-noise high-resolution detection capability is achieved by a new electrode design based on a high-amplitude anti-phase sense voltage. We reduce the mechanical noise of the microaccelerometer to the level of 5.5$\mu\textrm{g}$/(equation omitted) by increasing the proof-mass based on deep RIE process of an SOI wafer. We reduce the electrical noise as low as 0.6$\mu\textrm{g}$/(equation omitted) by using an anti-phase high-amplitude square-wave sense voltage of 19V. The nonlinearity problem caused by the high-amplitude sense voltage is solved by a new electrode design of branched finger type. Combined use of the branched finger electrode and high-amplitude sense voltage generates self force-balancing effects, resulting in an 140% increase of the bandwidth from 726㎐ to 1,734㎐. For a fixed sense voltage of 10V, the total noise is measured as 2.6$\mu\textrm{g}$/(equation omitted) at the air pressure of 3.9torr, which is the 51% of the total noise of 5.1$\mu\textrm{g}$/(equation omitted) at the atmospheric pressure. From the excitation test using 1g, 10㎐ sinusoidal acceleration, the signal-to-noise ratio of the fabricated microaccelerometer is measured as 105㏈, which is equivalent to the noise level of 5.7$\mu\textrm{g}$/(equation omitted). The sensitivity and linearity of the branched finger capacitive microaccelerometer are measured as 0.638V/g and 0.044%, respectively.

Prediction of the % Hardness Curve of Cellulose Acetate Mono Filters (셀룰로오스 아세테이트 모노 필터의 경도 예측)

  • Kim Jong-Yeol;Kim Soo-Ho;Shin Chang-Ho;Park Jin-Won;Lim Sung-Jin;Kim Chung-Ryul;Rhee Moon-Soo
    • Journal of the Korean Society of Tobacco Science
    • /
    • v.28 no.1
    • /
    • pp.43-50
    • /
    • 2006
  • The objective of the present study is to induct the regression equation for the hardness prediction of cellulose acetate filter which was manufactured by the domestic cellulose acetate tow manufacturer. As a result of our study, the hardness of filter was increased with increasing the plasticizer content and packing density as major factors affecting to the filter hardness. As a result which was obtained by the three dimensional response surface methodology in STATISTIC A program, the hardness prediction value well fitted with experiment result on the high plasticizer content. To make up for the this equation, the new modified fraction of solid factors which was contained the mono denier factor was introduced to the hardness prediction equation, and this third regression equation which was sufficient for the wide plasticizer content, was obtained by the three dimensional response surface methodology in STATISTICA. This results indicated that the third regression equation which was obtained this study was applicable for the hardness prediction of cellulose acetate filter which was manufactured by the domestic cellulose acetate tow manufacturer.

SOLUTIONS AND STABILITY OF TRIGONOMETRIC FUNCTIONAL EQUATIONS ON AN AMENABLE GROUP WITH AN INVOLUTIVE AUTOMORPHISM

  • Ajebbar, Omar;Elqorachi, Elhoucien
    • Communications of the Korean Mathematical Society
    • /
    • v.34 no.1
    • /
    • pp.55-82
    • /
    • 2019
  • Given ${\sigma}:G{\rightarrow}G$ an involutive automorphism of a semigroup G, we study the solutions and stability of the following functional equations $$f(x{\sigma}(y))=f(x)g(y)+g(x)f(y),\;x,y{\in}G,\\f(x{\sigma}(y))=f(x)f(y)-g(x)g(y),\;x,y{\in}G$$ and $$f(x{\sigma}(y))=f(x)g(y)-g(x)f(y),\;x,y{\in}G$$, from the theory of trigonometric functional equations. (1) We determine the solutions when G is a semigroup generated by its squares. (2) We obtain the stability results for these equations, when G is an amenable group.