Frontier simulations

The turbomachine group is involved in massively parallel simulation using thousands of computing cores, with the objective to simulate complete multistage machines at design and off-design conditions. Unsteady flows are simulated in a multistage compressor, by taking into account all the blades in the totality of the machine. The major interest from the scientific point of view is to understand the development of aerodynamic instabilities and the impact of rotor-stator interactions in these systems. The prediction of the stability limit (the so-called "surge”" line) is also a design parameter that can not be correctly predicted by current industrial CFD methods such as the mixing plane model coupled with steady RANS simulations. The  computational effort using an unsteady RANS method is increased by a factor 5000 with respect to steady simulations   in order to obtain a correct description of rotor-stator interactions. At near stall conditions (off-design) this computational effort can be increased by an additional factor 10.

Using IBM Blue Gene architectures, the computational time to obtain the solution is 280,000 CPU hours to obtain a periodic solution at design conditions (with 512 computing cores) and 4,000,000 CPU hours at off-design conditions to simulate a rotating stall phenomenon (with 4096 computing cores). The UWC method provides a result at design conditions in 22 days while 40 days are needed at off-design conditions. This demonstrative step will clearly help industries to improve their products efficiency by better predicting multistage interactions and related unsteady effects.

Contacts: Fabien Wlassow, Nicolas Gourdain