LES/PDF approach for turbulent reacting flows

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dc.contributor.advisorRaman, Venkaten
dc.contributor.committeeMemberClemens, Noelen
dc.contributor.committeeMemberEzekoye, Ofodikeen
dc.contributor.committeeMemberGoldstein, Daviden
dc.contributor.committeeMemberMoser, Roberten
dc.creatorDonde, Pratik Prakashen
dc.date.accessioned2013-02-15T17:27:21Zen
dc.date.accessioned2017-05-11T22:31:20Z
dc.date.available2017-05-11T22:31:20Z
dc.date.issued2012-12en
dc.date.submittedDecember 2012en
dc.date.updated2013-02-15T17:27:22Zen
dc.descriptiontexten
dc.description.abstractThe probability density function (PDF) approach is a powerful technique for large eddy simulation (LES) based modeling of turbulent reacting flows. In this approach, the joint-PDF of all reacting scalars is estimated by solving a PDF transport equation, thus providing detailed information about small-scale correlations between these quantities. The objective of this work is to further develop the LES/PDF approach for studying flame stabilization in supersonic combustors, and for soot modeling in turbulent flames. Supersonic combustors are characterized by strong shock-turbulence interactions which preclude the application of conventional Lagrangian stochastic methods for solving the PDF transport equation. A viable alternative is provided by quadrature based methods which are deterministic and Eulerian. In this work, it is first demonstrated that the numerical errors associated with LES require special care in the development of PDF solution algorithms. The direct quadrature method of moments (DQMOM) is one quadrature-based approach developed for supersonic combustion modeling. This approach is shown to generate inconsistent evolution of the scalar moments. Further, gradient-based source terms that appear in the DQMOM transport equations are severely underpredicted in LES leading to artificial mixing of fuel and oxidizer. To overcome these numerical issues, a new approach called semi-discrete quadrature method of moments (SeQMOM) is formulated. The performance of the new technique is compared with the DQMOM approach in canonical flow configurations as well as a three-dimensional supersonic cavity stabilized flame configuration. The SeQMOM approach is shown to predict subfilter statistics accurately compared to the DQMOM approach. For soot modeling in turbulent flows, an LES/PDF approach is integrated with detailed models for soot formation and growth. The PDF approach directly evolves the joint statistics of the gas-phase scalars and a set of moments of the soot number density function. This LES/PDF approach is then used to simulate a turbulent natural gas flame. A Lagrangian method formulated in cylindrical coordinates solves the high dimensional PDF transport equation and is coupled to an Eulerian LES solver. The LES/PDF simulations show that soot formation is highly intermittent and is always restricted to the fuel-rich region of the flow. The PDF of soot moments has a wide spread leading to a large subfilter variance. Further, the conditional statistics of soot moments conditioned on mixture fraction and reaction progress variable show strong correlation between the gas phase composition and soot moments.en
dc.description.departmentAerospace Engineeringen
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/2152/19481en
dc.language.isoen_USen
dc.subjectProbability density function approachen
dc.subjectLarge eddy simulationen
dc.subjectSupersonic combustion modelingen
dc.subjectSoot modelingen
dc.subjectTurbulent reacting flowsen
dc.subjectDirect quadrature method of momentsen
dc.subjectSemi-discrete quadrature method of momentsen
dc.subjectQuadrature based methodsen
dc.subjectLagrangian Monte Carlo methodsen
dc.subjectSupersonic combustorsen
dc.subjectFlame stabilizationen
dc.subjectPolycyclic aromatic hydrocarbonsen
dc.subjectSoot-turbulence-chemistry interactionsen
dc.subjectShock-turbulence-chemistry interactionsen
dc.titleLES/PDF approach for turbulent reacting flowsen

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