CFD Simulations AC6-14
Swirling flow in a conical diffuser generated with rotor-stator interaction
Application Challenge AC6-14 © copyright ERCOFTAC 2024
Overview of CFD Simulations
A series of numerical simulations was undertaken to study a highly swirling turbulent flow generated by rotor-stator interaction in a swirl generator \cite{Javadi2015c}. The purpose was to assess the applicability of different turbulence models in a swirling flow with a high level of unsteadiness and a significant production and dissipation of turbulence in the flow away from the wall. Nine turbulence models are compared: four high-Reynolds number models URANS, two low-Reynolds number models URANS and three hybrid URANS-LES models. These are the standard $k-\epsilon$, SST $k-\omega$, realizable $k-\epsilon$, RNG $k-\epsilon$, Launder-Sharma $k-\epsilon$, Lien-Cubic $k-\epsilon$, delayed DES Spalart-Allmaras \cite{Spalart2006}, DDES SST $k-\omega$ \cite{Gritskevich2012} and improved DDES-SA \cite{Shur2008} models. The URANS models are capable of capturing the main unsteady feature of this flow, the so-called helical vortex rope, which is formed by the strong centrifugal force and an on-axis recirculation region. However, the size of the on-axis recirculation region is overestimated by the URANS models. Although the low-Reynolds number URANS formulations resolve the boundary layers in the runner and the draft tube more accurately, they still encounter difficulties in predicting the main flow features in the adverse pressure gradient region in the draft tube. It is shown that a more detailed resolution, which is provided by the hybrid URANS-LES methods, is necessary to capture the turbulence and the coherent structures.
SIMULATION CASE CFD1
Solution Strategy
Computational Domain
Boundary Conditions
Application of Physical Models
Numerical Accuracy
CFD Results
References
SIMULATION CASE CFD2
(as per CFD 1)
Contributed by: A. Javadi, A. Bosioc, H Nilsson, S. Muntean, R. Susan-Resiga — Chalmers University of Technology
© copyright ERCOFTAC 2024