Diffusers with Three-Dimensional Separation as Test Bed for Hybrid LES/RANS Methods

Terzi, Dominic von; Schneider, Hayder; Fröhlich, Jochen

doi:10.1007/978-3-642-04665-0_26

Cited by 3 publications

(7 citation statements)

References 6 publications

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“…The derived setup was largely motivated by the experiments, but included several modifications. The influence of the modifications on the results was extensively examined in the previous studies, that is, during the two ERCOFTAC workshops (Jakirlić et al 2011), and, von Terzi, Schneider & Fröhlich (2010), von Terzi, and Schneider et al (2011). These studies included a qualitative and quantitative assessment of the effect of domain extent, grid resolution, averaging time, and the inflow generation method on the LES results.…”

Section: The Numerical Experimentsmentioning

confidence: 99%

A mechanism for control of turbulent separated flow in rectangular diffusers

et al. 2011

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The turbulent separated flow through an asymmetric diffuser with and without manipulation of incoming turbulence-driven mean secondary vortices (MSVs) from a rectangular duct is investigated by large-eddy simulations. The simulations carried out for two diffuser geometries reveal that by introducing a small amount of meanflow kinetic energy via the MSVs into the flow, the complex three-dimensional separation behaviour and pressure recovery can be effectively controlled. Manipulated MSVs were found to enhance cross-sectional transport of high-momentum fluid, which determined the location, shape, and size of the separation bubble. The integral effect was a delay or expedition in the onset of separation. This change strongly affected the conversion of mean-flow kinetic energy to pressure, in particular for the front part of the diffuser. In addition, a substantial reduction in total pressure loss could be achieved. The manipulation of the MSVs is an efficient mechanism for performance enhancement in the cases investigated. The results have important implications for both control and statistical modelling of turbulent separated flow in rectangular diffusers.

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Section: The Numerical Experimentsmentioning

confidence: 99%

A mechanism for control of turbulent separated flow in rectangular diffusers

et al. 2011

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“…Jakirlić et al [39] LES, Hybrid RANS/LES Reasonable results obtained with both methods. Von Terzi et al [40] LES, RANS (k − ω ) RANS fails to accurately predict velocity profiles and the separation. LES shows reasonable agreement with the experiment.…”

Section: Cherry Et Al [23]mentioning

confidence: 99%

“…The three-dimensional diffuser experiment offers further numerical challenge in predicting the separation and testing model sensitivity to slight changes in diffuser expansion angles. In addition to the experimental measurements, data from a DNS [38] and several LES simulations [39,40] are available for model validation.…”

Section: Three-dimensional Separated Diffuser Simulationsmentioning

confidence: 99%

“…The inability of the RANS approach to predict such complex separated flows was shown in the works of Von Terzi et al [40] and Cherry et al [23]. In [40], they performed an incompressible flow simulation using a finite volume solver [62] with a second-order accuracy spatial approximation (central difference scheme for viscous fluxes and an upwind scheme for convective fluxes) and a second-order implicit multi-step method for time advancement; mass conservation was achieved by the SIMPLE algorithm, with the pressurecorrection equation being solved by the strongly implicit procedure (SIP) of Stone. They applied the standard Wilcox k-ω [63] turbulence model and tested two different inlet conditions: uniform inlet velocity profile (simulation Ia) and fully developed channel flow profile (simulation Ib).…”

Section: Three-dimensional Separated Diffuser Simulationsmentioning

confidence: 99%

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A Review of the Computational Studies on the Separated Subsonic Flow in Asymmetric Diffusers Focused on Turbulence Modeling Assessment

2023

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Separated turbulent diffuser flows have long been an object of experimental and computational investigations due to their wide use in engineering applications and fundamental importance for understanding turbulent effects. The accuracy of simulating such flows depends mainly on turbulence modeling subtleties, numerical method, and the correspondence between the boundary conditions and the experimental set-up. The current review of selected articles focuses on revealing some of the computational challenges that may occur while modeling asymmetric subsonic diffuser flows. These challenges include the influence of sidewalls on the separation, issues with grid convergence, and the definition of boundary conditions. Several known experimental test cases and attempts at simulating them are studied. The novelty of this paper is in the fact that it is focused on a specific type of diffusers (asymmetric and subsonic) and based on relatively recent data. It is concluded that for all the test cases considered, Reynolds stress models and hybrid eddy-resolving methods are the most appropriate tools for obtaining reasonable results.

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“…However, lengthening the domain by adding a RANS zone and hence including the downstream effects may be an attractive alternative to more complex boundary conditions [4]. Another example is the flow in three-dimensional asymmetric diffusers that are prone to flow separation [5].…”

Section: Introductionmentioning

confidence: 99%