Modeling and simulation of primary jet breakup at aircraft engine relevant conditions

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The main goal of the second term of the project is the development of a method to predict the primary breakup of liquid fuel in a realistic airblast atomizer geometry using embedded DNS. The embedded DNS (eDNS) was introduced in the first term of the project and refers to a method in which the primary breakup is computed without underlying simplifying assumptions using a Direct Numerical Simulation (DNS) which is embedded in a Large-Eddy-Simulation (LES) of the whole airblast atomizer. The usage of the computationally expensive DNS is therefore reduced to the most important regions which enables the usage of DNS for realistic technical applications. In the first term of the project, the method was successfully employed to compute a generic geometry. Detailed comparison showed a good agreement of the predicted primary breakup to experimental data. The proposed project will compute the primary breakup at the atomizing edge of a real airblast atomizer. The droplet distributions at aircraft engine relevant conditions are extracted, enabling the transformation in to the Euler-Lagrange description for the subsequent simulation of the combustion, which is not part of the proposed project. The objectives of the work are to generate boundary conditions of the embedded domain (LES of the atomizer), an enhanced resolution of the phase interface through a coupling of VOF- and Level-Set method and the eDNS of the primary breakup. The work of the first term has shown that the complete resolution of the liquid mass is not feasible due to the large proportion of especially small droplets. The two objectives to reconstruct the non-resolved droplets and to evaluate the quality of the reconstruction method follow from this. Another objective is to analyse the physical breakup mechanism, which originate the primary breakup. The work of the second term enables the very first detailed insight into the primary breakup of a realistic airblast atomizer geometry at realistic operating conditions. The gained insights will contribute to significantly improve the capabilities to predict combustion chambers of aircraft engines.