Numerical and physical aspects in LES and hybrid LES/RANS of turbulent flow separation in a 3-D diffuser

Jakirlić, Suad; Kadavelil, G.; Kornhaas, Michael; Schäfer, Michael; Sternel, Dörte C.; Tropea, Cameron

doi:10.1016/j.ijheatfluidflow.2010.05.004

Cited by 42 publications

(27 citation statements)

References 24 publications

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“…This §ow presents a challenge for RANS modeling approaches, RANS simulations of this §ow have generally produced nonsatisfactory results [18]. The LES and hybrid RANS LES studies were more successful in predicting §ow behavior for this case [19]. However, when using synthetic turbulence, one usually obtains velocity and Reynolds stresses used to generate the synthetic velocity ¦eld from the RANS solution.…”

Section: Three-dimensional Diffuser Flowmentioning

confidence: 99%

Assessment of an approach to generating inflow synthetic turbulence for large eddy simulations of complex turbulent flows

Adamian

Travin

2013

Progress in Flight Physics

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An approach to generating in §ow synthetic turbulence recently developed by the authors has been applied to zonal Reynolds-Averaged Navier Stokes (RANS) / Large Eddy Simulations (LES) of two complex turbulent §ows: §ow over a wall-mounted hump and hydrofoil trailing edge §ow, and to a LES of a §ow in a three-dimensional (3D) di¨user. The results show that the zonal RANS-LES approach with synthetic turbulence at the interface is in excellent agreement with experimental data for hump and trailing edge §ows. For the di¨user §ow, it is shown that results depend signi¦cantly on the RANS model used to provide averaged velocity and Reynolds stresses at the inlet.

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Section: Three-dimensional Diffuser Flowmentioning

confidence: 99%

Assessment of an approach to generating inflow synthetic turbulence for large eddy simulations of complex turbulent flows

Adamian

Travin

2013

Progress in Flight Physics

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“…Actually one starts from the initially prescribed interface position (being in accordance with the initial instantaneous velocity field) and corrects it appropriately in the course of the computation. More specific details about zonal hybrid LES/RANS procedure including numerical realizations of individual steps can be found in Jakirlic et al (2009Jakirlic et al ( , 2010.…”

Section: Journal Of Fluid Science and Technologymentioning

confidence: 99%

On Interface Issues in LES/RANS Coupling Strategies: A Method for Turbulence Forcing

Jakirlić

Kniesner²,

Kadavelil

2011

JFST

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The present work deals with a computational strategy coupling near-wall, eddyviscosity-based RANS models with LES within a zonal Hybrid LES/RANS (HLR) framework. Key questions concerning the coupling of both methods, the inherently steady RANS method and highly-unsteady LES method, are closely connected to the treatment at the interface separating both sub-regions. Large attention was paid to this problem and following three issues were highlighted: (1) the exchange of the variables across the LES/RANS interface was adjusted by implicit imposition of the condition of equality of the modelled turbulent viscosities (by assuming the continuity of their resolved contributions across the interface), enabling a smooth transition from the near-wall RANS layer to the off-wall LES sub-region; (2) utilisation of a dynamic, flow-dependent interface position in the course of the simulation. The control parameter k * representing the ratio of the modelled (SGS) to the total turbulent kinetic energy in the LES region, averaged over all grid cells at the interface on the LES side, is adopted; (3) the third issue, the present work is focussing on, addresses the usage of a special forcing technique, which compensates the loss of information due to strong damping caused by the presence of the RANS region (the typical outcome of such a circumstance is the so-called velocity mismatch in the region of interface) by creation of artificial and correlated fluctuations using a method originating from a digital-filterbased generation of inflow data for spatially developing DNS and LES due to Klein et al. (2003). Herewith, the recovery of the fluctuations on the LES side of the interface is accelerated and the afore-mentioned velocity bump is eliminated to a largest extent. The performances of the model are illustrated against the available DNS and fine-grid LES of periodic flows in a plane channel and over a 2-D smoothly contoured hill respectively.

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“…In the same study, Schneider et al (2010) performed large-eddy simulation (LES) with near-wall modelling and obtained results that agreed with the experimental data within their accuracy for both D1 and D2. Good results were also reported for D1 employing both wall-resolving LES and a hybrid RANS/LES method (Jakirlić et al 2010). Ohlsson et al (2010) conducted a direct numerical simulation of D1 and observed that streamwise vortices emanating from the corners of the inlet persist into the diffuser.…”

Section: Introductionmentioning

confidence: 97%

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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Numerical and physical aspects in LES and hybrid LES/RANS of turbulent flow separation in a 3-D diffuser

Cited by 42 publications

References 24 publications

Assessment of an approach to generating inflow synthetic turbulence for large eddy simulations of complex turbulent flows

Assessment of an approach to generating inflow synthetic turbulence for large eddy simulations of complex turbulent flows

On Interface Issues in LES/RANS Coupling Strategies: A Method for Turbulence Forcing

A mechanism for control of turbulent separated flow in rectangular diffusers

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