Effects Of Boundary Layer Flow Research Articles

Numerical analysis for the effects of boundary layer flow over an exponentially stretching cylinder embedded in a porous medium moving with nonlinear velocity

The objective of this study is to probe the effects of boundary layer flow over an exponentially stretching cylinder having nonlinear velocity placed in a porous medium. The modeled partial differential equations are transformed into nonlinear ordinary differential equations by applying suitable similarity transformations. A numerical solution is attained using the finite difference Keller–Box method. The physical parameters and skin friction coefficients are studied on the velocity profile. The fluid velocity and skin friction coefficient decrease with the increase in Re and κ, while a reverse behavior is reported for ɛ.

Thermal and Entropy generation analysis of magnetohydrodynamic tangent hyperbolic slip flow towards a stretching sheet

This article examined the effects of boundary layer flow and heat transport of a two-dimensional incompressible magnetohydrodynamic tangent hyperbolic fluid under slip boundary conditions and variable thermal conductivity. The entropy generation model is also analysed for the said fluid. Non-similarity transformations transformed the governing equations of the fluid and entropy generation model into dimensionless form. Maple software is used to solve the transformed equations numerically. Effects of different dimensionless parameters on entropy generation rate, Bejan number, velocity and temperature fields are studied thoroughly through graphs. It is observed that for higher values of velocity slip parameter and power-law index, the entropy generation rate decreases while the Bejan number increases. Also, for the Hartmann number, Weissenberg number and Brinkman number, we found an increase in the entropy generation rate, and reverse behaviour is observed for the Bejan number. Nusselt number, temperature profile and Bejan’s number increase with an increase in variable thermal conductivity.

Transition of MHD boundary layer flow past a stretching sheet

In this paper a study is carried out to understand the transition effect of boundary layer flow: (1) due to a suddenly imposed magnetic field over a viscous flow past a stretching sheet and (2) due to sudden withdrawal of magnetic field over a viscous flow past a stretching sheet under a magnetic field. In both the cases the sheet stretches linearly along the direction of the fluid flow. Governing equations have been non-dimensionalised and the non-dimensionalised equations have been solved using the implicit finite difference method of Crank–Nicholson type. Comparison between the steady state exact solutions and the steady state computed solutions has been carried out. Graphical representation of the dimensionless horizontal velocity, vertical velocity and local skin friction profiles of the steady state and unsteady state has been presented. Computation has been carried out for various values of the magnetic parameter M. The obtained results has been interpreted and discussed.

The effect of boundary layer flow on incinerator efficiency

Incinerators operating with excess air, a core temperature of about 1100K, and a residence time of 1–2s should give essentially complete destruction of all organic pollutants exposed to these conditions. However, about 1% of the gas flows in the cooler boundary layer near the wall, where reaction occurs at a much lower rate. The decrease in reaction rate is partially offset by the lower velocity and by mass transfer of pollutant from the boundary layer to the core, but the overall effect is still a significant increase in the amount of unreacted pollutant. The effects of wall and core temperature and mass transfer from the boundary layer on incinerator efficiency were examined by computer simulation using toluene vapor in air as an example of a polluted stream.

Heterogeneous/homogeneous reactions and transport coupling for catalytic combustion systems: a review of model alternatives

In applying catalysis to real combustor applications the modeling of transport and chemistry interactions can be key to understanding combustion characteristics. For example the effect of boundary-layer flow and heterogeneous /homogeneous chemistry can determine product selectivity for catalytically promoted oxidation of chlorinated hydrocarbons. In this paper we discuss parameter regions where different flow models including lumped-parameter-transport laminar boundary-layer and full twodimensional models can be used for obtaining design insights. The degree of detail required in the gas phase chemistry models and surface chemistry models depends both on the system and the properties to be predicted. Definition of different regimes of operation and limits of applicability for parameric scaling relationships are key to the design of catalytic combustors for incineration or power generation. In addition, a theoretically-based rational strategy for applying catalytic boundary conditions in turbulent flow models would provide a valuable design tool. Examples of alternative modeling strategies are given below along with possible applications for the design of practical catalytic combustion systems.

Modeling heterogeneous/homogeneous reactions and transport coupling for catalytic combustion of methyl chloride over a Mn-based catalyst

The effect of boundary-layer flow and heterogeneous/homogeneous reaction chemistry in determiningproduct selectivity for catalytically promoted oxidation of ultralean CH 3 Cl over a Mn-based catalyst was investigated numerically. This work has relevance to modeling of more general catalytic combustion systems in defining the importance of transport and chemistry interactions. In this study, we find that the presence of Mn-based catalyst can significantly decrease the temperature necessary to achieve a given conversion of CH 3 Cl. The numerical study of the experiment used plug-flow, lumped-parameter transport, and laminar-flow models with detailed gas-phase chemistry. These flow models coupled with gas-phase reaction mechanisms from the literature and an experimentally determined surface reaction rate were used to illustrate heterogeneous/homogeneous reaction coupling and how it is influenced by transport. Kinetic modeling shows that the heterogeneous and homogeneous interaction occurs through CH 3 Cl decomposition on the surface that initiates gas-phase reaction. For the slower velocity, there is small difference in plug-flow model and detailed laminar boundary-layer model predictions. The difference in prediction between flow models becomes larger at the high velocity, with shorter residence time, where the higher surface temperature needed for equivalent conversion causes surface reaction products to be converted before they can be transported to the bulk. The important parameter for modeling heterogeneous/homogeneous interactions is the Damköhler number with respect to gas-phase consumption of species produced by surface reaction.

Thermal Decomposition Properties of a Twelve Component Organic Mixture

Hazardous Waste and Hazardous MaterialsVol. 3, No. 4 Thermal Decomposition Properties of a Twelve Component Organic MixtureDOUGLAS L. HALL, BARRY DELLINGER, JOHN L. GRAHAM, and WAYNE A. RUBEYDOUGLAS L. HALLSearch for more papers by this author, BARRY DELLINGERSearch for more papers by this author, JOHN L. GRAHAMSearch for more papers by this author, and WAYNE A. RUBEYSearch for more papers by this authorPublished Online:10 Apr 2009https://doi.org/10.1089/hwm.1986.3.441AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited byOxidation of trichloroethene in stagnation flows over inert and catalytic heated ceramic surfacesCombustion and Flame, Vol. 131, No. 4Selective Detection of Dibenzodioxin, Dibenzofuran and Some Small Polycyclic Aromatics22 September 2010 | Combustion Science and Technology, Vol. 134, No. 1-6Sonochemical degradation of carbon tetrachloride in aqueous solution at two frequencies: 20 kHz and 500 kHzUltrasonics Sonochemistry, Vol. 3, No. 2The effect of boundary layer flow on incinerator efficiencyJournal of Hazardous Materials, Vol. 45, No. 2-3Surrogate Detection for Continuous Emission Monitoring by Resonance IonizationCombustion Science and Technology, Vol. 101, No. 1-6Chapter 8: IncinerationRegulatory Toxicology and Pharmacology, Vol. 20, No. 1Emissions of Metal and Organic Compounds from Cement Kilns Using Waste Derived Fuels ADEL F. SAROFIM, DAVID W. PERSHING, BARRY DELLINGER, MICHAEL P. HEAP, and WARREN D. OWENS10 April 2009 | Hazardous Waste and Hazardous Materials, Vol. 11, No. 1Detection of Toxic Emissions from Incinerators8 May 2010 | Berichte der Bunsengesellschaft für physikalische Chemie, Vol. 97, No. 12Observations on Waste Destruction in Liquid Injection IncineratorsCombustion Science and Technology, Vol. 74, No. 1-6Mechanisms for the Formation and Destruction of Chlorinated Organic Products of Incomplete CombustionCombustion Science and Technology, Vol. 74, No. 1-6Profiles of Laminar Carbon Tetrachloride/Methane/Air FlamesCombustion Science and Technology, Vol. 66, No. 1-3 Volume 3Issue 4Jan 1986 To cite this article:DOUGLAS L. HALL, BARRY DELLINGER, JOHN L. GRAHAM, and WAYNE A. RUBEY.Thermal Decomposition Properties of a Twelve Component Organic Mixture.Hazardous Waste and Hazardous Materials.Jan 1986.441-449.http://doi.org/10.1089/hwm.1986.3.441Published in Volume: 3 Issue 4: April 10, 2009PDF download

圧縮性乱流境界層におけるエネルギー方程式の特解の拡張について

The problems concerning the curvature effects of boundary layer flow along a curved solid surface have been found in many papers. The curvature effects of compressible turbulent boundary layer flow, however, have been scarcely investigated because of its complexity. In the present paper, the effects of curvature on compressible turbulent boundary layer flow are investigated and the conditions, under which the particular solutions of energy equation exist, are derived.To describe a boundary layer flow along a curved solid surface, orthogonal curvilinear coordinates (α, β) are introduced, where α and β are the coordinates along and normal to the curved solid surface, respectively. Applying the boundary layer approximation to the basic equations of compressible turbulent flow expressed in orthogonal curvilinear coordinates, the boundary layer equations in compressible turbulent flow are derived. Introducing eddy viscosity and eddy thermal conductivity, the particular solutions of energy equation are integrated under certain conditions. It is found that the particular solutions can be obtained, when Prandtl number and turbulent Prandtl number are both unity and the α coordinate along the curved solid surface is straight line.