Moritz Merk successfully defends his dissertation

12.02.2025

Moritz Merk defended his dissertation "Comprehensive and consistent models for the linear analysis of thermoacoustic phenomena". A 20 min SlideCast is available at the TFD YouTube Channel.

Thanks to Yang Dong (SUSTech) for serving as external examiner. Hans Jakob Kaltenbach chaired the defense.

Moritz made several remarkable contributions to the field:

He formulated in collaboration with Alexander J. Eder a framework for analyzing thermoacoustic sources in motion, such as the reaction zone of a premixed flame placed in an acoustic field. An Arbitrary Lagrangian-Eulerian (ALE) reference frame tracks perturbation sources consistently. This framework helps to analyze sources of acoustic, entropic, vortical, and compositional perturbation and provides insights into the underlying interaction mechanisms. The ALE framework can also help to identify spurious disturbances resulting from inappropriate modeling assumptions. (DOI 10.1016/j.combustflame.2024.113334)

In collaboration with Felix Schily, Moritz also proposed and validated a Jacobian-based framework for deriving comprehensive thermoacoustic jump conditions. The procedure takes in to consideration acoustic, entropic, and compositional perturbations and minimizes assumptions during derivation, making the jump conditions applicable to a wide range of cases. The framework has been used to derive and validate jump conditions for a lean premixed flame and a lean hydrogen-vitiated air autoignition flame. (DOI 10.1016/j.combustflame.2024.113958)

In collaboration with Alexander J. Eder as well as Claus Lahiri and André Fischer (Rolls-Royce Germany), Moritz also developed a model-based inference method in order to determine flame transfer function from experimental measurements in test rigs with complex features, such as bypass annulus, effusion holes, or changes in combustion chamber cross section – such as the SCARLET (Scaled Acoustic Rig for Low Emission Technology) rig at DLR Cologne. (DOI 10.1115/1.4066366)

In collaboration with Philip Erik Buschmann and Jonas Moeck (NTNU), Moritz also evaluated various strategies for solving the thermoacoustic eigenvalue problem, in particular contour integration and methods that approximate and reformulate the problem as a linear eigenvalue problem (DOI 10.1115/1.4055583)