Shalaby H., Thévenin D., Bui P., Schröder W., Meinke M.

A hybrid DNS/CAA method is used to simulate acoustic wave propagation caused by thermoacoustic sources. The numerical approach is a two-step method, the first step of which is based on a direct numerical simulation (DNS), followed by the computational aeroacoustic using the acoustic perturbation equations for reactive flows (APE-RF). The combustion configuration considered is a fully premixed methane/air flame at an equivalence ratio of Á = 1:59, atmospheric pressure, and fresh gas temperature of 298 K. A perfectly spherical laminar flame kernel is initialized at zero velocity and superposed with a field of synthetic homogeneous isotropic turbulence, corresponding to a von K´arm´an spectrum with Pao correction for near-dissipation scales. In order to describe the chemical processes the DNS code relies on the FPI method (Flame Prolongation of ILDM). As a whole, this method leads to a pre-tabulation of all species values and of their thermodynamic coefficients as a function of a reduced number of coordinates. Then, the DNS results are employed in order to evaluate the source terms of the APE-RF system. Using a detailed description of the flow based on the DNS solution, a detailed analysis of the sources in terms of the radiated acoustic field is possible. The DNS grids have been interpolated onto the CAA grids by using a multi-linear algorithm.