PhD Defense : Benjamin MARTIN – “Numerical methods and boundary conditions for Large-Eddy Simulation of turbomachinery multi-component coupling “
Large-Eddy Simulation (LES) of multiple turbomachinery components is a powerful tool with considerable potential to study their coupling and performance in a real configuration. Unfortunately, the cost of such simulations is still highly prohibitive today to be used in the majority of industrial applications. This thesis presents different numerical methods to lower their cost while retaining results in adequacy with LES requirements. Computation of convective terms is a key issue to ensure the accuracy and robustness of a LES. After describing the numerical schemes for convection already available in the AVBP code, improvements and optimizations are suggested, especially to improve their behavior on perturbed meshes as commonly found in industrial simulations. The AVBP code is already used in Safran's design offices for the development of modern combustion chambers and its use is gradually being extended to turbomachinery stages. An improvement in the efficiency and robustness of the code can therefore have a direct impact on its application in an industrial environment. To this end, a new family of schemes using the Petrov-Galerkin formalism is introduced to overcome known problems regarding mesh sensitivity of the existing schemes, while allowing an increase of accuracy. The use of local time-stepping methods is also an option to consider in order to reduce the cost of a coupled simulation. One of such approach is validated on academical configurations before being applied to more complex configurations to demonstrate its potential gains. Finally, more realistic boundary conditions can also be considered to reproduce the coupling between multiple components in a turbomachinery. This new type of boundary conditions, built from the modal decomposition of a database recorded at the chamber/turbine interface, is compared to typical boundary conditions in the case of an isolated turbine simulation.
|Franck NICOUD||Université de Montpellier||Member|