MAE 298 Seminar: Stochastic simulation of turbulent reacting flows using reduced dimensional models–One Dimensional Turbulence (ODT) and Heirarchical Parcel Swapping (HiPS)
Department of Chemical Engineering
Brigham Young University
Abstract: Turbulent flows are ubiquitous in nature and widely studied in science and engineering. Modeling and simulation of turbulent flows are extremely challenging due to the wide range of time and length scales. Reacting flows that are especially important in combustion add an extra layer of complexity. Only direct numerical simulations (DNS) are able to resolve all flow and reactive structures but computational constraints limit simulations to canonical configurations at relatively low Reynolds numbers. Flows of interest in engineering require models for unresolved flow structures. These subgrid structures involve complex and nonlinear interactions including detailed reaction chemistry, multicomponent mass transfer, radiative heat transfer and multiphase flow. This places a high burden on modeling and there are no models that can capture all phenomena in all flow regimes. For instance, in combustion, one modeling approach may be used for premixed flames and another for nonpremixed flames. The One-Dimensional Turbulence (ODT) model captures all physical phenomena, resolving all scales in a physical coordinate and in a computationally-efficient manner by considering only one spatial coordinate. This is sufficient for boundary-layer flows like jets and near wall flows. Turbulence is modeled by stochastic domain mapping processes. The ODT model is presented with comparisons to experiments and DNS data for several cases including soot formation and flame extinction and reignition. ODT is shown to reproduce many key quantities available only to DNS at a fraction of the cost. The Hierarchical Parcel Swapping (HiPS) method will also introduced. This is a stochastic model of turbulent mixing that is based on a binary tree structure. HiPS can be considered an optimum between turbulence abstraction and reproduction of physical phenomena and is an ideal candidate for Lagrangian mixing models in transported probability density function (PDF) simulations. HiPS will be presented with application to differentially-diffusing species, including scalar energy spectra, Richardson dispersion and scalar dissipation rate PDFs. Both HiPS and ODT can be used as subgrid formulations in three-dimensional simulations and efforts in this area are underway.
Bio: Lignell received his B.S. in chemical engineering from the University of Utah in 2001. He then worked for Reaction Engineering International doing model development, consulting and engineering analysis of energy systems including coal furnaces, gas cleanup units, and integrated gasification combined cycle (IGCC) processes. He recieved a Ph.D. in chemical engineering from the University of Utah in 2008 working with Philip Smith. His graduate research was conducted at the Combustion Research Facility (CRF) at Sandia National Laboratories in Livermore, California, where he worked with Jacqueline Chen on large-scale direct numerical simulations (DNS) of soot formation in turbulent nonpremixed ethylene jet flames. Lignell worked as a post-doc at the CRF with Alan Kerstein where he developed a modern implementation of the one-dimensional turbulence (ODT) model. He joined Brigham Young University (BYU) in January 2009. Lignell’s research has focused on modeling and simulation of turbulent reacting flows using large-eddy simulation (LES) along with significant development of stochastic turbulence models including ODT and the hierarchical parcel swapping (HiPS) model. He has taught classes in fluid mechanics, combustion, programming and numerical methods. Lignell has served on the board of the Western States Section of the Combustion Institute (WSSCI) since 2010 and served as Program Chair from 2014-2021. He is currently the chair of the Western States Section of the Combustion Institute and on the board of the U.S. Sections of the Combustion Institute. At BYU he served as associate chair for six years and is currently the chair of the ChemE department Advancement and Alumni Committee. Lignell also advises the BYU student chapter of the American Institute for Chemical Engineers. As an undergraduate his peers voted him ”most likely to keep his AIChE membership,” which he has.