Numerical and experimental study of separated flow in a plane asymmetric diffuser

Gullman-Strand, Johan; Törnblom, Olle; Lindgren, Björn; Amberg, Gustav; Johansson, A.

doi:10.1016/j.ijheatfluidflow.2004.02.012

Cited by 32 publications

(21 citation statements)

References 13 publications

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“…In (13), n indicates the respective outward normal vector of unit length to i . The characteristic length scale h chosen in LESs is usually considerably larger than the smallest length scale of the problem under investigation (i.e., by far not all scales of the problem can be resolved).…”

Section: Problem Statement and Variational Finite Volume Formulationmentioning

confidence: 99%

“…Experimental studies of turbulent flow in a planar asymmetric diffuser were presented, for instance, in [2,36], and recently in [13]. A DNS of the flow at this Reynolds number in the present diffuser configuration is still prohibitively expensive.…”

mentioning

confidence: 97%

“…Large eddy simulations were conducted in [26] and recently in [40]. Numerical investigations of this case using simulations based on the Reynolds-averaged NavierStokes equations were described in [1,7,13], and [22]. The diffuser problem was also a test case at a workshop [17] in 1999.…”

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confidence: 99%

“…However, the most obvious failure of NM is its clear overestimation of the recirculating velocity in the outlet channel. Thus, it does not provide a reasonable approximation of the flow separation as well as the reattachment point, which should be expected at x 1 ≈ 52 according to the Buice-experiment.The profiles for the root-mean-square velocity in streamwise direction are shown in Figs 13,14,15,. and 16.…”

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confidence: 99%

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Variational Multiscale Large Eddy Simulation of Turbulent Flow in a Diffuser

Gravemeier

2006

Comput Mech

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In the present study, variational multiscale large eddy simulation (LES) is applied to turbulent flow in a diffuser, which represents a challenging test case due to the appearance of flow separation and subsequent reattachment. Two different scale-separating operators based on multigrid operators are used for separating large and small resolved scales. Dynamic as well as constant-coefficient-based subgrid-scale modeling are employed in the variational multiscale LES. The results show that the variational multiscale LES with a simple constant-coefficient Smagorinsky model using a projective scale-separating operator yields a very good prediction of most of the crucial flow features. Furthermore, it turns out to be by far the most computationally efficient approach, resulting in a computing time reduction of about 18% compared to the traditional LES with a dynamic Smagorinsky model. The variational multiscale LES with a dynamic Smagorinsky model does not prove to be a superior approach.

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Section: Problem Statement and Variational Finite Volume Formulationmentioning

confidence: 99%

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confidence: 97%

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confidence: 99%

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confidence: 99%

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Variational Multiscale Large Eddy Simulation of Turbulent Flow in a Diffuser

Gravemeier

2006

Comput Mech

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“…The diffuser wall is inclined at the diverging angle of 10 • . Recently, new experimental data for the asymmetric diffuser have been obtained by Törnblom [27] (see also [7]) for slightly different conditions. These authors used an increased inflow Reynolds number of Re b = 20,000 and a decreased opening angle of 8.5 • .…”

Section: Introductionmentioning

confidence: 99%

Simulations of Turbulent Flow in a Plane Asymmetric Diffuser

Herbst

Schlatter

Henningson

2007

Flow Turbulence Combust

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Large-eddy simulations (LES) of a planar, asymmetric diffuser flow have been performed. The diverging angle of the inclined wall of the diffuser is chosen as 8.5 • , a case for which recent experimental data are available. Reasonable agreement between the LES and the experiments is obtained. The numerical method is further validated for diffuser flow with the diffuser wall inclined at a diverging angle of 10 • , which has served as a test case for a number of experimental as well as numerical studies in the literature (LES, RANS). For the present results, the subgrid-scale stresses have been closed using the dynamic Smagorinsky model. A resolution study has been performed, highlighting the disparity of the relevant temporal and spatial scales and thus the sensitivity of the simulation results to the specific numerical grids used. The effect of different Reynolds numbers of the inflowing, fully turbulent channel flow has been studied, in particular, Re b = 4,500, Re b = 9,000 and Re b = 20,000 with Re b being the Reynolds number based on the bulk velocity and channel half width. The results consistently show that by increasing the Reynolds number a clear trend towards a larger separated region is evident; at least for the studied, comparably low Reynolds-number regime. It is further shown that the small separated region occurring at the diffuser throat shows the opposite behaviour as the main separation region, i.e. the flow is separating less with higher Re b . Moreover, the influence of the Reynolds number on the internal layer occurring at the non-inclined wall described in a recent study has also been assessed. It can be concluded that this region close to the upper, straight wall, is more distinct for larger Re b . Additionally,

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