Scrutinizing URANS in Shedding Flows: The Case of Cylinder in Cross-Flow in the Subcritical Regime

Palkin, Egor; Mullyadzhanov, R. I.; Hadžiabdić, M.; Hanjalić, K.

doi:10.1007/s10494-016-9772-z

Cited by 52 publications

(25 citation statements)

References 47 publications

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“…It may lead to the conclusion that the characteristic length and time scales do not correspond to appropriate sub-grid scales when the model is operating as sub-grid scale model, mainly due to the lack of direct tie to the grid. This is consistent with the discussion provided in [22,26] regarding uncertainties concerning the seamless hybrid methods when operating in scale-resolving mode. They cannot be considered systematic eddy-resolving methods and therefore, may produce unrealistic spectrum in some situations.…”

Section: Methodssupporting

confidence: 91%

“…It is generally expected that the hybrid models can reliably be applied to flow configurations with sufficiently strong instability available in the base flow (flows with strong swirl/separation) [18]. However, there is no guarantee that the models always deliver accurate results since non of these models qualify for a systematic eddy resolving approach and therefore, they should be applied only to flows for which they have been extensively tested [26]. In the following, we will shortly describe each approach focusing mainly on the triggering mechanisms used in each approach to make a transition from URANS to scale-resolving mode.…”

Section: Hybrid Turbulence Modelsmentioning

confidence: 99%

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Assessment of predictive capability of hybrid URANS/LES methods in residence time calculation

Mehdizadeh

Doost

Sadiki

et al. 2018

Chemical Engineering Science

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The present study aims to assess capability of mostly used hybrid URANS/LES methods in dealing with a complex swirled configuration/reactor when the residence time characteristics need to be predicted at acceptable level of accuracy and fidelity. The configuration is quite complex and out of reach of the classical RANS turbulence models as it consists of different, partly swirled inlet channels and a large variety of time and length scales. In this work only the flow field is considered and is investigated using three different hybrid URANS/LES simulation methods. The models: the Scale Adaptive Simulation (SAS), the Improved Delayed Detached Eddy Simulation(SA-IDDES) and the k − ω − DES, use different triggering mechanisms and underlying RANS models. The results of the flow field, the residence time characteristics and all related quantities are compared with both the Large Eddy Simulation (LES) and experimental data reported in Doost et.al [17]. It turns out that none of the considered hybrid methods is able to predict the residence time characteristics as well as LES does mainly due to the inaccurate prediction of the flow field. It was found that there is a need to improve the hybrid approaches by addressing the shortcomings, particularly those regarding triggering mechanism to make hybrid approaches a reliable computational tool for study complex turbulent flows inside full scale configurations where LES can be prohibitively expensive.

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Section: Methodssupporting

confidence: 91%

Section: Hybrid Turbulence Modelsmentioning

confidence: 99%

Assessment of predictive capability of hybrid URANS/LES methods in residence time calculation

Mehdizadeh

Doost

Sadiki

et al. 2018

Chemical Engineering Science

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“…The direct comparison with PIV experiments showed very good agreement of the position of main time-averaged vortices. We find that the recirculating bubble manifests low-frequency oscillations similar to the unconfined case [1,3]. Further work will be devoted to studying the elongated vortical structures found also in confined turbulent jets [4][5][6][7] and their role in heat transfer across the channel.…”

Section: Resultsmentioning

confidence: 65%

“…The presence of walls strongly affects dynamics of the flow resulting in the change of time-averaged characteristics. Figure 3 (left) shows the comparison of the time-averaged axial velocity and streamlines for the confined (present) case in the mid-plane (z=0.5H=0.2D) and without walls from previous simulations [1]. While the pattern is the same, the recirculating bubble shrinks and becomes narrower in the presence of walls.…”

Section: Resultsmentioning

confidence: 88%

Vortical structures in a shallow wake of the flow around a confined cylinder at Re=3750

Palkin

Mullyadzhanov

2017

EPJ Web Conf.

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Abstract. We study the flow over a cylinder placed between two parallel rigid walls using Large-eddy simulations. The Reynolds number based on the inflow velocity and diameter of the cylinder is 3750 corresponding to the subcritical regime with laminar separation. The comparison of the timeaveraged flow patterns shows very good agreement with experiments. The unsteadiness of the recirculating bubble features the low-frequency modulation observed for the first time.

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“…In such configurations a horseshoe vortex system appears prior to a bluff body increasing the local shear stress and heat transfer [1] while the flow is characterized by periodic shedding of large-scale vortices behind the body that form the Kármán vortex street. Low-frequency modulations of the recirculating zone are detected for various configurations such as a cylinder [2,3], disk and sphere [4], prism [5], bullet [6], among others. The period is typically 10 ÷ 100 times lower compared to the main vortex shedding frequency.…”

Section: Introductionmentioning

confidence: 99%

Flow around a confined cylinder: LES and PIV study

et al. 2017

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Abstract. We study the flow over a cylinder placed between two parallel rigid walls using Large-eddy simulations and Particle Image Velocimetry. The Reynolds number based on the inflow velocity and diameter of the cylinder is 3750 corresponding to the subcritical regime with laminar separation. Three-dimensional visualization shows the presence of the horseshoe vortex system prior to the cylinder. The comparison of timeaveraged velocity fields and fluctuations shows good agreement between simulations and experiments. Spectral analysis suggests the presence of low-frequency modulations of the recirculating bubble.

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Scrutinizing URANS in Shedding Flows: The Case of Cylinder in Cross-Flow in the Subcritical Regime

Cited by 52 publications

References 47 publications

Assessment of predictive capability of hybrid URANS/LES methods in residence time calculation

Assessment of predictive capability of hybrid URANS/LES methods in residence time calculation

Vortical structures in a shallow wake of the flow around a confined cylinder at Re=3750

Flow around a confined cylinder: LES and PIV study

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