Abstr:AC6-14: Difference between revisions
| Line 24: | Line 24: | ||
Nine turbulence models are compared: four high-Reynolds number URANS, | Nine turbulence models are compared: four high-Reynolds number URANS, | ||
two low-Reynolds number URANS and three hybrid URANS-LES models. | two low-Reynolds number URANS and three hybrid URANS-LES models. | ||
The URANS models are capable of capturing the main unsteady feature of this flow, | 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 | the so-called helical vortex rope, which is formed by the strong centrifugal force and | ||
Revision as of 07:03, 11 April 2016
Swirling flow in a conical diffuser generated with rotor-stator interaction
Application Area 6: Turbomachinery Internal Flow
Application Challenge AC6-14
Abstract
The flow unsteadiness generated in a swirl apparatus is investigated experimentally
and numerically.
The swirl apparatus, shown in figure below, is designed and measured in
Timi\c{s}oara, Romania.
The LDA measurements are performed along three survey axes in the test section to
provide the characteristics of the swirling flow in the conical diffuser.
The swirling flow configuration corresponds to part load operation of a Francis turbine.
A series of numerical simulations is undertaken to study a highly swirling turbulent
flow generated by rotor-stator interaction in a swirl generator.
The purpose is to assess the applicability of different turbulence models in 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 URANS,
two low-Reynolds number URANS and three hybrid URANS-LES 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.
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.
The flow contains a strong disintegration of the vortex rope which is predicted well by
the hybrid URANS-LES models.
The hybrid methods also capture the blade wakes better than the other models,
elucidating the wake interaction with the vortex rope.
The frequency of the vortex rope is predicted well and the total turbulence
(resolved and modeled), suggested by the hybrid method, corresponds reasonably well to
the experimental results.
Contributed by: A. Javadi, A. Bosioc, H Nilsson, S. Muntean, R. Susan-Resiga — Chalmers University of Technology
© copyright ERCOFTAC 2011