University of Illinois Urbana-Champaign

Analysis of diffusion models in high speed reacting flow simulations

Knisely, Andrew

Content Files
Andrew_Knisely.pdf

Permalink

https://hdl.handle.net/2142/42322

Description

Title
Analysis of diffusion models in high speed reacting flow simulations
Author(s)
Knisely, Andrew
Issue Date
2012-12
Director of Research (if dissertation) or Advisor (if thesis)
Austin, Joanna M.
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2013-02-03T19:35:19Z
Keyword(s)
  • High Speed
  • Reactive
  • Simulations
  • Diffusion Models
Abstract
The purpose of this study was to analyze the effect of mass diffusion in a high speed reacting flow field. Diffusion processes have typically been neglected in high speed reacting flows as the time scales associated with convective and reactive processes are found to be much shorter than diffusive time scales. However, diffusion may become important in secondary flow structures such as shear layers. There are several diffusion models that can be used in reactive simulations. The benefits and numerical cost of each model are discussed along with implementations of the models in previous works. The effects of including thermal diffusion into the models are also discussed. Since thermal diffusion effects are expensive to simulate, it is important to know how they affect the accuracy of the simulation results. The High Speed Combustion and Detonation (HSCD) code was used to simulate a two dimensional reflected shock flow field in a reactive H2-O2 mixture. The goal was to evaluate the effect of diffusion on the flow field. The HSCD code was first validated with Cantera by analyzing the mass diffusion flux in a freely propagating flame. When Soret diffusion was included the HSCD code results matched Cantera well. Ignition delay times were compared with experimental results. The ignition delay times were found to be within the error bars of the experimental results. The two modes of ignition, strong and weak, were observed in the simulations. In the simulations, the strong ignition events were unaffected by diffusion effects while the weak ignition events were affected by diffusion. Weak ignition occurred earlier then predicted by constant volume combustion calculations. The diffusion model choice in the HSCD code noticeably changed the values for diffusion flux. The mass diffusion flux due to temperature gradients was found to vary for different temperatures at low initial temperatures while was unaffected by changes in temperature at high initial temperatures.
Graduation Semester
2012-12
Permalink
http://hdl.handle.net/2142/42322
Copyright and License Information
Copyright 2012 Andrew Knisely

Owning Collections

Dissertations and Theses - Aerospace Engineering
Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois