LIMITATIONS AND EMPIRICAL EXTENSIONS OF THE k-ε MODEL AS APPLIED TO TURBULENT CONFINED SWIRLING FLOWS

Abujelala, M. T.; Lilley, David G.

doi:10.1080/00986448408911152

Cited by 41 publications

(19 citation statements)

References 16 publications

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“…2, No. 4 (2008) axial velocities for strongly swirling flows (Abujelala and Lilley, 1984;Jones and Pascau, 1989). Preliminary CFD results obtained by the author for a simple swirling flow (see below) indicated the tendency of the KEM to produce an excessive solid-body component type of rotation (Fig.…”

Section: Summary Of the Turbulence Models Applicable To Swirling Flowsmentioning

confidence: 90%

“…1). Various modifications to the standard KEM have been proposed, such as Richardson number corrections for streamline curvature, to account for the effect of turbulent anisotropy, which is inherent in swirling flows (see Nallasamy, 1987;Lakshminarayana, 1986;Abujelala and Lilley, 1984;Pourahmadi and Humphrey, 1983;Kim and Chung, 1987 Reynolds Stress Transport or Differential Stress model (DSM) is an implementation based on the solutions of the modeled partial differential equations for the components of the stress. Even though it is complex and computationally expensive, it seems to be the most capable tool for simulation of confined swirling flows since it allows modeling of the anisotropic structure of the flow turbulence without ad hoc modifications.…”

Section: Summary Of the Turbulence Models Applicable To Swirling Flowsmentioning

confidence: 99%

“…Several modifications to the equation of turbulence dissipation are suggested by Launder, Priddin and Sharma (1977), Leschziner and Rodi (1984), and Abujelala and Lilley (1984). Launder, Priddin and Sharma (1977) incorporates streamline curvature effects on the turbulence structure in the k-ε model.…”

Section: Verification Of the Modifiedmentioning

confidence: 99%

“…Abujelala and Lilley (1984) proposed a modified k-ε model where the turbulent constant C 2 is modified by a Richardson number defined as…”

Section: Verification Of the Modifiedmentioning

confidence: 99%

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Simplified Turbulence Models for Confined Swirling Flows

Bui¹

2008

Engineering Applications of Computational Fluid Mechanics

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Turbulent flow in a stirred vessel is distinguished by the domination of the swirl velocity component, which makes the flow turbulence highly anisotropic. As a result, conventional turbulence models based on the eddy viscosity hypothesis provide poor predictions for not only turbulence characteristics, but also velocity distributions. Many suggestions to modify the conventional turbulence models that take into account the effect of flow swirl have been made. Even though a reasonable distribution of the velocity field can be obtained with the modified k-ε turbulence model proposed by Launder, Priddin and Sharma (1977), the approach fails to provide a good prediction for the turbulence characteristics, especially at the core region. The Reynolds stress transport model based on a second-order closure scheme seems to be able to provide much better prediction results without any ad hoc modification. However, the computational complexity with this model is considerable. The ordinary algebraic stress model, which stems from the Reynolds stress transport model, was found not working for the swirling flows in a stirred vessel. In this work, a modification to the algebraic stress model is proposed, which takes into account additional terms arising from the production terms of the Reynolds stress transport equations during the transformation of these equations from Cartesian to cylindrical coordinate system. Comparisons of the prediction results are made with available experimental data and with the results obtained by means of the differential Reynolds stress turbulence model.

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Section: Summary Of the Turbulence Models Applicable To Swirling Flowsmentioning

confidence: 90%

Section: Summary Of the Turbulence Models Applicable To Swirling Flowsmentioning

confidence: 99%

Section: Verification Of the Modifiedmentioning

confidence: 99%

“…Abujelala and Lilley (1984) proposed a modified k-ε model where the turbulent constant C 2 is modified by a Richardson number defined as…”

Section: Verification Of the Modifiedmentioning

confidence: 99%

See 2 more Smart Citations

Simplified Turbulence Models for Confined Swirling Flows

Bui¹

2008

Engineering Applications of Computational Fluid Mechanics

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“…In order to simulate confined swirling flow, various adjustments and tuning to the KEM have been proposed. Khodadadi and Vlachos [8] pointed out that it cannot accurately predict the swirling recirculating flow field for a wide range of swirl numbers, if it only modifies three empirical constants in standard KEM [9]. Some researchers have proposed to take into account the enhanced turbulence diffusion caused by the extra strain rate incorporated with streamline curvature to modify the standard KEM [5,6,10,11].…”

Section: Introductionmentioning

confidence: 99%

3D tangentially injected swirling recirculating flow in a nozzle with a slotted‐tube—Effects of groove parameters

Guo

Chen

2010

Numerical Methods in Fluids

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SUMMARYA numerical prediction for 3D swirling recirculating flow in an air-jet spinning nozzle with a slotted-tube is carried out with the realizable k-ε turbulence model. The effects of the groove parameters on the flow and yarn properties are investigated. The simulation results show that some factors, such as reverse flow upstream of the injector, vortex breakdown downstream of the injector, corner recirculation zone (CRZ) behind the step and vortex ring in the groove caused by the groove geometric variation, are significantly related to fluid flow, and consequently to yarn properties. With increasing groove height, the length of the CRZ increases, while the initial vortex ring in the groove decreases and a same direction rotating vortex forms in the bottom of the groove. Similarly, as the groove width increases, the extent of both vortex breakdown in downstream of the injectors and the vortex ring in the groove increases slightly, whereas the CRZ lengths in stream-wise direction decrease. Some factors, such as the negative tangential velocities, the size of the vortex rings in the grooves and the CRZ, are constant for nozzles with different groove lengths.

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Numerical prediction of a nusselt number equation for stirred tanks with helical coils

Prada

Nunhez

2017

AIChE Journal

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A methodology to obtain a Nusselt correlation for stirred tank reactors is presented. The novelty of the approach is the use of a validated computational model to obtain the heat‐transfer coefficients. The advantages of this new approach are many, including the possibility of testing different heat‐transfer configurations to obtain their Nusselt correlation without performing experimental runs. Physical phenomena involved was represented both qualitatively and quantitatively. The classical experimental work of (Oldshue and Gretton, Chem Eng Prog. 1954;50(12):615–621) illustrates the procedure. A sufficient number of virtual points in the whole range of the Reynolds number should be obtained. Results strongly depend on mesh refinement in the boundary layer, so a procedure is suggested to guarantee heat‐transfer coefficients are accurately estimated. The final Nusselt correlation was compared against all the 107 experimental points of the work by (Oldshue and Gretton, Chem Eng Prog. 1954;50(12):615–621), and an average deviation on the results of 10.7%. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3912–3924, 2017

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LIMITATIONS AND EMPIRICAL EXTENSIONS OF THE k-ε MODEL AS APPLIED TO TURBULENT CONFINED SWIRLING FLOWS

Cited by 41 publications

References 16 publications

Simplified Turbulence Models for Confined Swirling Flows

Simplified Turbulence Models for Confined Swirling Flows

3D tangentially injected swirling recirculating flow in a nozzle with a slotted‐tube—Effects of groove parameters

Numerical prediction of a nusselt number equation for stirred tanks with helical coils

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