Download or read book Non premixed Combustion Full Numerical Simulation of a Coflowing Axisymmetric Jet Inviscid and Viscous Stability Analysis written by Stanford University. Thermosciences Division. Thermosciences Division and published by . This book was released on 1989 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Non premixed Combustion written by Shankar Mahalingam and published by . This book was released on 1989 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Turbulent Nonpremixed Hydrogen Combustion with Different Levels of Modelling and Computation written by Prasad V. R. K. S. Pokkunuri and published by . This book was released on 2007 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Numerical Procedure for an Inviscid Stability Analysis of an Axisymmetric Jet written by Elizabeth F. Moore and published by . This book was released on 1983 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inviscid stability analysis has been applied to the mixing layer profile of an axisymmetric jet and a coflowing stream. A collection of computer subprograms has been developed to solve the resulting eigenvalue problem. The effect of changing the velocity profile and its parameters can be easily assessed. Results for Gaussian profiles are included.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 1990 with total page 796 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studying Turbulence Using Numerical Simulation Databases IV written by Center for Turbulence Research (U.S.) and published by . This book was released on 1992 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studying Turbulence Using Numerical Simulation Databases 4 Proceedings of the 1992 Summer Program written by and published by . This book was released on 1992 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Annual Research Briefs 1993 written by and published by . This book was released on 1993 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Annual Commencement written by Stanford University and published by . This book was released on 1987 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Self similar Compressible Free Vortices written by Karl Von Ellenrieder and published by . This book was released on 1998 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence Transport in Spatially Developing Reacting Shear Layers written by Scott D. Mason and published by . This book was released on 2000 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling and Simulation of Turbulent Combustion written by Santanu De and published by Springer. This book was released on 2017-12-12 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.
Download or read book A 2D local Linear Stability Analysis of Asymptotically expanded Jet in crossflows written by Da Wei David Ren and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The jet-in-crossflow is a critical flowfield for a range of aerospace propulsion systems, both airbreathing and rocket engines. A jet-in-crossflow or transverse jet is typically composed of a jet issuing from a circular outlet perpendicularly to a uniform air crossflow. Previous experiments deploying hot-wire anememetry or laser-based optical diagnostics such as planar laser-induced fluorescence (PLIF) or particle image velocimetry (PIV) have found that there is a transition in the jet's upstream shear layer from convective to absolute instability as the jet-to-crossflow velocity ratio $R$ or momentum flux ratio $J$ decreases. Typically, convectively unstable jets-in-crossflow are correlated with more asymmetric cross-sections while more symmetric jet cross-sections are typically associated with absolutely unstable transverse jets at lower $R$ values, usually below $3$ (Gevorkyan et al., 2016). Besnard et al. (2022) demonstrated that even low-amplitude asymmetric acoustic excitation affected the symmetry of a convectively unstable jet-in-crossflow. Such a finding suggests that there may be a linear origin to symmetry-breaking in the face of a theoretically symmetric flow field. This dissertation describes a numerical investigation of the spatial linear stability characteristics of a jet-in-crossflow for the axisymmetric and helical azimuthal modes using a 2D-local viscous linear stability analysis. This study uses the viscous hyperbolic-tangent (tanh) and uniformly valid asymptotic solution (UVAS) base flows developed by Alves et al. (2008) and Alves & Kelly (2008) as viscous extensions of the cylindrical vortex sheet solution of Coelho & Hunt (1989), who performed asymptotic expansion-based linear stability analyses of the same base flows. This present work may be considered a `fully-coupled' extension of their work because we presently account for all base flow-eigenfunction azimuthal coupling. The eigenspectra from the present fully-coupled linear stability analysis indicate that the axisymmetric mode spatially stabilises as $R$ decreases - in contradiction with experimental measurements (Megerian et al., 2007; Davitian et al., 2010; Shoji et al., 2020a), direct numerical simulation results (Iyer & Mahesh, 2016), and with the prior asymptotic expansion-based linear stability analysis of Alves et al. (2008); Alves & Kelly (2008). The wavenumber and preferred Strouhal number trends, however, are in qualitative agreement with experimental measurements. The first, second, and third helical modes all stabilise as $R$ decreases, with the axisymmetric mode being more unstable than the helical modes. All helical modes exhibit degeneracy-breaking, as was found from multiple mode analysis of an inviscid base flow by Alves et al. (2007); these modes are symmetric or anti-symmetric with respect to the plane of symmetry found in the jet-in-crossflow base flows. A novel upwind-based treatment of the linearised convective term is developed to explore features of the eigenfunctions while eliminating non-physical oscillations in the high Reynolds number regime. This consists of a hybrid central-upwind finite difference discretisation scheme suitable for convection-dominated flows that allows for surgical suppression of non-physical numerical oscillations while still yielding similar eigenvalues to purely central difference schemes. Given that only the near-wake region needed this winding, the overall scheme consists of a $4^{\mathrm{th}}$-order central finite difference for all non-convective terms, a hybrid $2^{\mathrm{nd}}$-$1^{\mathrm{st}}$-order scheme for the near-wake region and a hybrid $4^{\mathrm{th}}$-$3^{\mathrm{rd}}$-order scheme elsewhere. A linear activation function is used to smooth the transition from one regime to another. This approach was effective in both Cartesian and polar coordinates. Given that the primary difference between the present fully-coupled and prior asymptotic expansion-based linear stability analyses lies in the number of supported base flow-eigenfunction azimuthal couplings, a weakly-coupled discrete Fourier-transformed linear stability analysis is developed to allow an exploration of the effect of base flow-eigenfunction azimuthal couplings on the eigenvalues. This weakly-coupled approach can highlight the essential velocity eigenfunctions or azimuthal interactions that affect the eigenvalues the most and may be considered as a sort of reduced-order model. By reproducing the base flow-eigenfunction couplings as closely as possible without repeating the same approach, the weakly-coupled linear stability analysis yields quantitatively similar axisymmetric eigenvalues as Alves & Kelly (2008). That is to say, the UVAS base flow spatial destabilises as $R$ decreases. As the number of Fourier modes $N_f$ increases, and therefore the number of base flow-eigenfunction couplings supported, the axisymmetric mode appears to become more similar to the fully-coupled results, with stabilisation as $R$ decreases. Hence, a mechanism is proposed wherein an inadequately-expanded asymptotic base flow leads to incomplete base flow-eigenfunction couplings that deleteriously affect the eigenvalues. Without those couplings, the surviving terms may contribute to eigenvalue stabilisation. To explore this hypothesis further, a spatial kinetic energy budget analysis is developed, showing the contribution of various physical mechanisms (`Advection', `Production', and `Pressure-velocity') to the spatial growth of the kinetic energy. The `Pressure-velocity' correlation term is unique to the spatial formulation. Typically, for example, for a one-dimensional parallel Blasius boundary layer, the `Pressure-velocity' term suppresses the energy when the disturbance is destabilising and supplies the energy when the disturbance is stabilising, per Hama et al. (1980). This implies that the `Pressure-velocity' term becomes an increasing percentage of the total energy budget as the flow destabilises. Indeed, in the present analysis for the jet-in-crossflow, the axisymmetric mode from the fully-coupled analysis exhibits a decreasing contribution from the `Pressure-velocity' term, consistent with our observed stabilisation when R is decreased. In contrast, the spatial kinetic energy budget for the weakly-coupled analysis found that the 'Pressure-velocity' contribution increases substantially for low R, suggesting destabilisation. All mode coupling terms are negative contributions to the energy budget - supporting the proposed mechanism. Based on the present studies, it is clear that future directions for research would include obtaining a more representative jet-in-crossflow base flow by extending the tanh or UVAS base flows to higher orders of $1/R$ or from using time-averaged experimental or numerical simulation data. Such a base flow could also be used to inform non-modal stability or resolvent analyses to better match impulsively or harmonically forced jets-in-crossflow. The wavemaker (in a 2D-local sense) could also be found, which may synergise with the passive tab disturbance of the jet-in-crossflow.
Download or read book Numerical Approaches to Combustion Modeling written by Elaine S. Oran and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 1991 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Simulation of Low speed Non premixed Combustion Using a Pre conditioning Technique written by V. Bellucci and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulent Combustion Modeling written by Tarek Echekki and published by Springer Science & Business Media. This book was released on 2010-12-25 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent combustion sits at the interface of two important nonlinear, multiscale phenomena: chemistry and turbulence. Its study is extremely timely in view of the need to develop new combustion technologies in order to address challenges associated with climate change, energy source uncertainty, and air pollution. Despite the fact that modeling of turbulent combustion is a subject that has been researched for a number of years, its complexity implies that key issues are still eluding, and a theoretical description that is accurate enough to make turbulent combustion models rigorous and quantitative for industrial use is still lacking. In this book, prominent experts review most of the available approaches in modeling turbulent combustion, with particular focus on the exploding increase in computational resources that has allowed the simulation of increasingly detailed phenomena. The relevant algorithms are presented, the theoretical methods are explained, and various application examples are given. The book is intended for a relatively broad audience, including seasoned researchers and graduate students in engineering, applied mathematics and computational science, engine designers and computational fluid dynamics (CFD) practitioners, scientists at funding agencies, and anyone wishing to understand the state-of-the-art and the future directions of this scientifically challenging and practically important field.
Download or read book Numerical Simulation of Non premixed Turbulent Combustion written by Stephen M. De Bruyn Kops and published by . This book was released on 1999 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt:
