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B O Falodun - One of the best experts on this subject based on the ideXlab platform.
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effects of thermal radiation soret and dufour on an unsteady Heat and mass transfer flow of a chemically reacting fluid past a semi infinite vertical plate with viscous dissipation
Journal of the Nigerian Mathematical Society, 2016Co-Authors: F I Alao, Adeyemi Isaiah Fagbade, B O FalodunAbstract:Abstract In this paper, the influence of some thermo-physical properties of fluid on Heat and mass transfer flow past semi-infinite moving vertical plate is considered. The fluid considered is optically thin such that the thermal Radiative Heat Loss on the fluid is modeled using Rosseland approximation. The governing equations representing the physical model is a system of partial differential equations which are transformed into systems of coupled non-linear partial differential equation by introducing non-dimensional variables. The resulting equations are solved using the spectral relaxation method (SRM). The result shows that an increase in Eckert number of the fluid actually increases the velocity and temperature profiles of the flow. Whereas an increase in thermal radiation parameter reduces the temperature distribution when the plate is being cooled. The computational results for velocity, temperature and the concentration profiles are displayed graphically for various flow pertinent parameters.
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effects of thermal radiation soret and dufour on an unsteady Heat and mass transfer flow of a chemically reacting fluid past a semi infinite vertical plate with viscous dissipation
Journal of the Nigerian Mathematical Society, 2016Co-Authors: F I Alao, A I Fagbade, B O FalodunAbstract:Abstract In this paper, the influence of some thermo-physical properties of fluid on Heat and mass transfer flow past semi-infinite moving vertical plate is considered. The fluid considered is optically thin such that the thermal Radiative Heat Loss on the fluid is modeled using Rosseland approximation. The governing equations representing the physical model is a system of partial differential equations which are transformed into systems of coupled non-linear partial differential equation by introducing non-dimensional variables. The resulting equations are solved using the spectral relaxation method (SRM). The result shows that an increase in Eckert number of the fluid actually increases the velocity and temperature profiles of the flow. Whereas an increase in thermal radiation parameter reduces the temperature distribution when the plate is being cooled. The computational results for velocity, temperature and the concentration profiles are displayed graphically for various flow pertinent parameters.
Kaoru Maruta - One of the best experts on this subject based on the ideXlab platform.
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nonlinear evolution of diffusion flame oscillations triggered by Radiative Heat Loss
Combustion and Flame, 2000Co-Authors: Chae Hoon Sohn, Jaeduck Kim, Suk Ho Chung, Kaoru MarutaAbstract:Nonlinear dynamics of radiation-induced oscillatory instability in diffusion flames is numerically investigated by employing a diffusion flame established in stagnant mixing layer with optically thin gas-phase radiation and unity Lewis numbers for all species as a model. Particular attention is focused on the radiation-induced extinction regime that occurs when the Damkohler number is sufficiently large. Transient evolution of the flame, initiated by imposing a Damkohler number perturbation on the steady solution, exhibits three types of flame-evolution behaviors, namely decaying oscillatory solution, diverging solution to extinction, and stable limit-cycle solution. The locus of the critically perturbed Damkohler number, across which diverging solutions are separated from decaying solutions or limit-cycle solutions, is obtained, and it can be used as a dynamic extinction boundary for laminar flamelet library. The bifurcation structure is found to be a double Hopf bifurcation, involving a supercritical Hopf bifurcation and a subcritical Hopf bifurcation. The stable limit-cycle solutions, which occur only in the radiation-induced extinction regime while not observed in the transport-induced extinction regime, are found in a small island-shaped parametric region of Damkohler number and flame temperature, in which the double Hopf bifurcation exists, with perturbation amplitudes smaller than the amplitude of the unstable limit cycle of the subcritical Hopf bifurcation. The stable limit-cycle behavior is implied to be relevant to the remarkably sustainable droplet-flame oscillations observed in the space shuttle experiment.
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effects of the lewis number and Radiative Heat Loss on the bifurcation and extinction of ch4 o2 n2 he flames
Journal of Fluid Mechanics, 1999Co-Authors: Yiguang Ju, Kaoru MarutaAbstract:Eects of the Lewis number and Radiative Heat Loss on flame bifurcations and extinc- tion of CH 4/O2-N2-He flames are investigated numerically with detailed chemistry. Attention is paid to the interaction between radiation Heat Loss and the Lewis number eect. The Planck mean absorption coecients of CO, CO2, and H2O are calculated using the statistical narrow-band model and compared with the data given by Tien. The use of Tien's Planck mean absorption coecients overpredicts Radiative Heat Loss by nearly 30 % in a counterflow conguration. The new Planck mean absorption coecients are then used to calculate the extinction limits of the planar propagating flame and the counterflow flame when the Lewis number changes from 0.967 to 1.8. The interaction between radiation Heat Loss and the Lewis number eect greatly enriches the phenomenon of flame bifurcation. The existence of multiple flames is shown to be a physically intrinsic phenomenon of radiating counterflow flames. Eight kinds of typical patterns of flame bifurcation are identied. The competition between radiation Heat Loss and the Lewis number eect results in two distinct phenomena, depending on if the Lewis number is greater or less than a critical value. Comparisons between the standard limits of the unstrained flames and the flammability limits of the counterflow flames indicate that the flammability limit of the counterflow flame is lower than the standard limit when the Lewis number is less than the critical value and is equal to the standard limit when the Lewis number is higher than this critical value. Finally, a G-shaped curve and a K-shaped curve which respectively represent the flammable regions of the multiple flames for Lewis numbers lower and higher than the critical value are obtained. The G- and K-shaped curves show a clear relationship between the stretched counterflow flame and the unstrained planar flame. The present results provide a good explanation of the physics revealed experimentally in microgravity.
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extinction of low stretched diffusion flame in microgravity
Combustion and Flame, 1998Co-Authors: Kaoru Maruta, Hongsheng Guo, Masaharu Yoshida, Takashi NiiokaAbstract:Extinction of counterflow diffusion flames of air and methane diluted with nitrogen is studied by drop tower experiments and numerical calculation using detailed chemistry and transport properties. Radiative Heat Loss from the flame zone is taken into consideration. Experimental results identified two kinds of extinction at the same fuel concentration, that is, in addition to the widely known stretch extinction, another type of extinction is observed when the stretch rate is sufficiently low. Consequently, plots of stretch rates versus fuel concentration limits exhibit a C-shaped extinction curve. Numerical calculation including Radiative Heat Loss from the flame zone qualitatively agreed with the experimental results and indicated that the mechanism of counterflow diffusion flame extinction at low stretch rates was Radiative Heat Loss.
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radiation extinction limit of counterflow premixed lean methane air flames
Combustion and Flame, 1997Co-Authors: Yiguang Ju, Kaoru Maruta, Takashi NiiokaAbstract:Abstract The application of the laminar flamelet concept to turbulent flame modeling requires a detailed understanding of stretched laminar flames. In this study, we used numerical methods, including are-length continuation, to simulate the extinction characteristics of counterflow premixed fuel-lean, methane-air flames. Attention was primarily paid to the effect of Radiative Heat Loss on the extinction characteristics of these flames. The results show that at medium to low values of the stretch rate, the Radiative Heat Loss has a particularly strong impact on the counterflow premixed fuel-lean, methane-air flames. It was also found that, in addition to the stretch extinction limit at a high stretch rate, there exits a radiation extinction limit at a low stretch rate. Furthermore, the relationship between these two extinction limits and the equivalence ratio is obtained.
Hiroshi Gotoda - One of the best experts on this subject based on the ideXlab platform.
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chaos of Radiative Heat Loss induced flame front instability
Chaos, 2016Co-Authors: Hikaru Kinugawa, Kazuhiro Ueda, Hiroshi GotodaAbstract:We are intensively studying the chaos via the period-doubling bifurcation cascade in Radiative Heat-Loss-induced flame front instability by analytical methods based on dynamical systems theory and complex networks. Significant changes in flame front dynamics in the chaotic region, which cannot be seen in the bifurcation diagrams, were successfully extracted from recurrence quantification analysis and nonlinear forecasting and from the network entropy. The temporal dynamics of the fuel concentration in the well-developed chaotic region is much more complicated than that of the flame front temperature. It exhibits self-affinity as a result of the scale-free structure in the constructed visibility graph.
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short term prediction of dynamical behavior of flame front instability induced by Radiative Heat Loss
Chaos, 2012Co-Authors: Hiroshi Gotoda, Takuya Ikawa, Koshiro Maki, Takaya MiyanoAbstract:We apply nonlinear forecasting to the time series of the flame front instability induced by Radiative Heat Loss to test for the short-term predictability and long-term unpredictability characteristic of deterministic chaos in flame front instability. Our results indicate that the flame front instability represents high-dimensional chaos generated via the period-doubling cascade process reported in our previous study [H. Gotoda, K. Michigami, K. Ikeda, and T. Miyano, Combust Theory Modell. 14, 479 (2010)], while its short-term behavior is predictable using a local nonlinear predictor based on the Sugihara-May method [H. Gotoda, H. Nikimoto, T. Miyano, and S. Tachibana, Chaos 20, 013124 (2011); G. Sugihara and R. M. May, Nature 344, 734 (1990)] as well as a generalized radial basis function network as a global nonlinear predictor. The feasibility of a new approach based on short-term prediction is also discussed in this work from the practical viewpoint of combustion systems.
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chaotic oscillation in diffusion flame induced by Radiative Heat Loss
Combustion Theory and Modelling, 2010Co-Authors: Hiroshi Gotoda, Keisuke Michigami, Kota Ikeda, Takaya MiyanoAbstract:We numerically investigate the dynamic behavior of flame front instability in a diffusion flame caused by Radiative Heat Loss from the viewpoint of nonlinear dynamics. As the Damkohler number increases at a high activation temperature, the dynamic behavior of the flame front undergoes a significant transition from a steady-state to high-dimensional deterministic chaos through the period-doubling cascade process known as the Feigenbaum transition. The existence of high-dimensional chaos in flame dynamics is clearly demonstrated using a sophisticated nonlinear time series analysis technique based on chaos theory.
R K Chhajlani - One of the best experts on this subject based on the ideXlab platform.
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effect of finite larmor radius corrections on the thermal instability of thermally conducting viscous plasma with hall current and electron inertia
The Astrophysical Journal, 2016Co-Authors: Shweta Jain, Sachin Kaothekar, Prerana Sharma, R K ChhajlaniAbstract:The thermal instability of an infinite homogeneous, thermally conducting, and rotating plasma, incorporating finite electrical resistivity, finite electron inertia, and an arbitrary Radiative Heat-Loss function in the presence of finite Larmor radius corrections and Hall current, has been studied. Analysis has been made with the help of linearized magnetohydrodynamics (MHD) equations. A general dispersion relation is obtained using the normal mode analysis method, and the dispersion relation is discussed for longitudinal propagation and transverse propagation separately. The dispersion relation has been solved numerically to obtain the dependence of the growth rate on the various parameters involved. The conditions of modified thermal instability and stability are discussed in the different cases of interest.
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jeans instability of self gravitating partially ionized hall plasma with Radiative Heat Loss functions and porosity
PROCEEDING OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN APPLIED PHYSICS AND MATERIAL SCIENCE: RAM 2013, 2013Co-Authors: Sachin Kaothekar, R K ChhajlaniAbstract:The Jeans instability of partially ionized self gravitating plasma is discussed to investigate the effect of the Hall current, Radiative Heat-Loss function, thermal conductivity, collision frequency of neutrals, porosity, finite electrical resistivity and viscosity for the formation of stars in HI and HII regions. The standard Magnetohydrodynamics (MHD) set of equations is used for the present configuration with Radiative Heat-Loss function and thermal conductivity. A general dispersion relation is obtained from perturbation equations using the normal mode analysis method. We find that the Jeans condition of self-gravitational instability is modified due to the presence of neutral particle, Radiative Heat-Loss functions and thermal conductivity. Presence of Hall current, porosity and collision frequency have no effect on Jeans criterion.
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effect of neutral collision and Radiative Heat Loss function on self gravitational instability of viscous thermally conducting partially ionized plasma
AIP Advances, 2012Co-Authors: Sachin Kaothekar, Ghanshyam D Soni, R K ChhajlaniAbstract:The problem of thermal instability and gravitational instability is investigated for a partially ionized self-gravitating plasma which has connection in astrophysical condensations. We use normal mode analysis method in this problem. The general dispersion relation is derived using linearized perturbation equations of the problem. Effects of collisions with neutrals, Radiative Heat-Loss function, viscosity, thermal conductivity and magnetic field strength, on the instability of the system are discussed. The conditions of instability are derived for a temperature-dependent and density-dependent Heat-Loss function with thermal conductivity. Numerical calculations have been performed to discuss the effect of various physical parameters on the growth rate of the gravitational instability. The temperature-dependent Heat-Loss function, thermal conductivity, viscosity, magnetic field and neutral collision have stabilizing effect, while density-dependent Heat-Loss function has a destabilizing effect on the growth rate of the gravitational instability. With the help of Routh-Hurwitz's criterion, the stability of the system is discussed.
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effect of Radiative Heat Loss function and finite larmor radius corrections on jeans instability of viscous thermally conducting self gravitating astrophysical plasma
International Scholarly Research Notices, 2012Co-Authors: Sachin Kaothekar, R K ChhajlaniAbstract:The effect of Radiative Heat-Loss function and finite ion Larmor radius (FLR) corrections on the self-gravitational instability of infinite homogeneous viscous plasma has been investigated incorporating the effects of thermal conductivity and finite electrical resistivity for the formation of a star in astrophysical plasma. The general dispersion relation is derived using the normal mode analysis method with the help of relevant linearized perturbation equations of the problem. Furthermore the wave propagation along and perpendicular to the direction of external magnetic field has been discussed. Stability of the medium is discussed by applying Routh Hurwitz’s criterion. We find that the presence of Radiative Heat-Loss function and thermal conductivity modify the fundamental Jeans criterion of gravitational instability into Radiative instability criterion. From the curves we see that temperature dependent Heat-Loss function, FLR corrections and viscosity have stabilizing effect, while density dependent Heat-Loss function has destabilizing effect on the growth rate of self-gravitational instability. Our result shows that the FLR corrections and Radiative Heat-Loss functions affect the star formation.
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self gravitational instability of rotating viscous hall plasma with arbitrary Radiative Heat Loss functions and electron inertia
Astrophysics and Space Science, 2010Co-Authors: R P Prajapati, Sachin Kaothekar, R K Pensia, R K ChhajlaniAbstract:The effects of arbitrary Radiative Heat-Loss functions and Hall current on the self-gravitational instability of a homogeneous, viscous, rotating plasma has been investigated incorporating the effects of finite electrical resistivity, finite electron inertia and thermal conductivity. A general dispersion relation is obtained using the normal mode analysis with the help of relevant linearized perturbation equations of the problem, and a modified Jeans criterion of instability is obtained. The conditions of modified Jeans instabilities and stabilities are discussed in the different cases of our interest. We find that the presence of arbitrary Radiative Heat-Loss functions and thermal conductivity modifies the fundamental Jeans criterion of gravitational instability into a Radiative instability criterion. The Hall parameter affects only the longitudinal mode of propagation and it has no effect on the transverse mode of propagation. For longitudinal propagation, it is found that the condition of Radiative instability is independent of the magnetic field, Hall parameter, finite electron inertia, finite electrical resistivity, viscosity and rotation; but for the transverse mode of propagation it depends on the finite electrical resistivity, the strength of the magnetic field, and it is independent of rotation, electron inertia and viscosity. From the curves we find that the presence of thermal conductivity, finite electrical resistivity and density-dependent Heat-Loss function has a destabilizing influence, while viscosity and magnetic field have a stabilizing effect on the growth rate of an instability. The effect of arbitrary Heat-Loss functions is also studied on the growth rate of a Radiative instability.
F I Alao - One of the best experts on this subject based on the ideXlab platform.
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effects of thermal radiation soret and dufour on an unsteady Heat and mass transfer flow of a chemically reacting fluid past a semi infinite vertical plate with viscous dissipation
Journal of the Nigerian Mathematical Society, 2016Co-Authors: F I Alao, Adeyemi Isaiah Fagbade, B O FalodunAbstract:Abstract In this paper, the influence of some thermo-physical properties of fluid on Heat and mass transfer flow past semi-infinite moving vertical plate is considered. The fluid considered is optically thin such that the thermal Radiative Heat Loss on the fluid is modeled using Rosseland approximation. The governing equations representing the physical model is a system of partial differential equations which are transformed into systems of coupled non-linear partial differential equation by introducing non-dimensional variables. The resulting equations are solved using the spectral relaxation method (SRM). The result shows that an increase in Eckert number of the fluid actually increases the velocity and temperature profiles of the flow. Whereas an increase in thermal radiation parameter reduces the temperature distribution when the plate is being cooled. The computational results for velocity, temperature and the concentration profiles are displayed graphically for various flow pertinent parameters.
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effects of thermal radiation soret and dufour on an unsteady Heat and mass transfer flow of a chemically reacting fluid past a semi infinite vertical plate with viscous dissipation
Journal of the Nigerian Mathematical Society, 2016Co-Authors: F I Alao, A I Fagbade, B O FalodunAbstract:Abstract In this paper, the influence of some thermo-physical properties of fluid on Heat and mass transfer flow past semi-infinite moving vertical plate is considered. The fluid considered is optically thin such that the thermal Radiative Heat Loss on the fluid is modeled using Rosseland approximation. The governing equations representing the physical model is a system of partial differential equations which are transformed into systems of coupled non-linear partial differential equation by introducing non-dimensional variables. The resulting equations are solved using the spectral relaxation method (SRM). The result shows that an increase in Eckert number of the fluid actually increases the velocity and temperature profiles of the flow. Whereas an increase in thermal radiation parameter reduces the temperature distribution when the plate is being cooled. The computational results for velocity, temperature and the concentration profiles are displayed graphically for various flow pertinent parameters.
