Analysis of Combustion LES using an Eulerian Monte Carlo PDF Method.
Technische Universität, Darmstadt
[Ph.D. Thesis], (2011)
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|Item Type:||Ph.D. Thesis|
|Title:||Analysis of Combustion LES using an Eulerian Monte Carlo PDF Method|
The present work focusses on an elaborated analysis of Large Eddy Simulations in the framework of turbulent reacting flows. An Eulerian Monte Carlo PDF transport scheme has been developed and implemented into the existing LES code FLOWSI in order to obtain a sophisticated reference method for detailed investigations of commonly used combustion related LES sub-models. By transporting a statistical representation of sub-filter scalar distributions, additional information for the validation of sub-filter PDF models are provided. The obtained results are used as a basis for model assessments in terms of various modeling aspects in general and in the turbulence-chemistry interaction in particular. The contribution begins with the description of the predominating physical effects corresponding to turbulent combustion and derives the fundamental equations for the mathematical representation of these phenomena. In addition, the basic methods of numerical mathematics are introduced, which serve as an promising tool in the computational fluid dynamics. The described statistical Monte Carlo PDF method is verified and validated employing two generic text cases. Therefore, a pure mixing case as well as a thought experiment including reactive components are considered. The main part of the work is a detailed analysis of a non-premixed turbulent bluff body configuration in terms of model sensitivities and related influences on the results. This includes definitions of inflow boundary conditions, the behavior of the statistical error in Monte Carlo PDF methods and an extensive investigation on the capability of presumed sub-filter PDF approaches. Furthermore, the impact of a more complex chemistry representation employing an additional transported progress variable is evaluated. In this context, an analysis on the statistical independency of the mixture fraction and the reactive progress variable is performed, which is a basic assumption for a multitude of corresponding models. Finally, all constructed hypotheses are proved within two different reactive test cases. These are a Reynolds number variation of the bluff body configuration as well as a non-premixed piloted jet flame. The results obtained in these investigations confirm the assumptions made. On this basis, the achieved knowledge of sensitivities and influences of different approaches and sub-models can be applied as a basis for future model developments in the framework of combustion related Large Eddy Simulations.
|Place of Publication:||Darmstadt|
|Classification DDC:||600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften|
|Divisions:||16 Department of Mechanical Engineering > Institute for Energy and Power Plant Technology (EKT)|
|Date Deposited:||20 Apr 2011 09:23|
|Last Modified:||07 Dec 2012 11:59|
|Referees:||Janicka, Prof. Dr.- Johannes and Chen, Prof. Dr. Jyh-Yuan|
|Refereed:||22 March 2011|