Off design simulations of an S-shaped intermediate compressor duct: Experimental validation of DDES and RANS using G3D::Flow

Paper i proceeding, 2020

A comparison is made between measurements obtained in an experimental test rig at GKN Aerospace and simulations using the CFD solver G3D::Flow, developed and maintained at Chalmers University of Technology. The geometry represents an Intermediate Compressor Duct (ICD) of an aircraft engine. The aim is to validate the different CFD turbulence closure techniques with experimental data and to compare the CFD methods with each other. The turbulence techniques used are RANS, Unsteady-RANS (URANS) and Delayed-Detached Eddy-Simulation (DDES) models. The one-equation turbulence model, developed by Spalart and Allmaras, is used as the main model for the (U)RANS simulations and as the sub-grid-scale model for the DDES. To save computational resources, wall-functions are used to model the boundary layers. Overall, the CFD simulations are in a good agreement with the measured data, where some differences are observed when considering radial profiles of total pressure, downstream of the ICD. Furthermore, there are instabilities present in the DDES simulations at the inner wall of the ICD. Large instabilities were also observed in the experiments, represented by relatively large uncertainties. This behavior was not captured by the (U)RANS simulations. Additionally, the instantaneous DDES is capable of representing the true flow much better (if sufficiently small scales are resolved), where the (U)RANS results will never exist in reality, limiting the information acquired.