Session: 34-08 CFD and Modeling Methods

Paper Number: 152540

Zonal Hybrid RANS-LES Simulation of a 1.5-Stage Turbine 

We present a zonal hybrid RANS-LES simulation of a 1.5-stage low aspect ratio turbine, constituted by two stator rows framing one rotor row with Reynolds numbers of 800k, 500k and 300k at the blade row exits, respectively. While the stators are treated as steady wall-resolved RANS domains, a wall-modeled LES is conducted in the rotor of the turbine. To bi-directionally couple these sub-domains of different spectral content, we introduce a new method by extending the classical mixing plane concept. Following the mixing plane approach, adjacent blade rows, here simulated as single passages, exchange circumferentially averaged radial profiles. Instantaneous profiles of the RANS mixing plane sides are used, whereas an exponential moving temporal average technique is applied to the radial profiles obtained at the LES sides of the mixing planes prior to transferring them. Based on the modeled turbulence quantities of the upstream stator, turbulent fluctuations are introduced at the inlet of the LES rotor sub-domain by utilizing a rotational synthetic turbulence generator. At the second mixing plane between the rotor and the downstream stator, modeled turbulence quantities, required as boundary values by the RANS turbulence model in the downstream stator, are reconstructed at the outlet of the LES sub-domain. Furthermore, the method features the combination of implicit pseudo time integration in the RANS sub-domains and explicit time integration in the LES sub-domain. The analysis of the flow simulation focuses on the feasibility of conducting an embedded LES in the confined space of the rotor. The influence of the type of turbulence model used in the upstream RANS sub-domain on the LES sub-domain is investigated. Additionally, the effect of the LES sub-domain on the surrounding RANS sub-domains is examined by comparing against experimental references and numerical results obtained from a pure RANS simulation.

Presenting Author: Jonas Buchmeier German Aerospace Center, Institute of Test and Simulation for Gas Turbines

Presenting Author Biography: Jonas Buchmeier is a postdoctoral researcher at the German Aerospace Center (DLR) working on the development of hybrid RANS-LES methods for turbomachinery applications. Prior to joining the DLR, he received a Ph.D. in aerospace engineering at the University of Southern California, where his research focused on the development of post-processing tools for scale-resolving CFD simulations.

Authors:

Jonas Buchmeier German Aerospace Center, Institute of Test and Simulation for Gas Turbines
Christian Morsbach German Aerospace Center, Institute of Propulsion Technology
Patrick Bechlars MTU Aero Engines AG