Use of the equation for turbulent viscosity to describe the flow near a rough surface

Лебедев, А. Б.; Sekundov, A. N.

doi:10.1007/bf01015444

Cited by 5 publications

(5 citation statements)

References 3 publications

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“…In the same term we have taken into account the effect of the wall roughness, which requires [3] a change in the boundary condition for the turbulent viscosity from the trivial condition vt=O to avt/igniw=O, where n is the normal to the wall. This boundary condition is more universal.…”

Section: Formulation Of the "*:92" Modelmentioning

confidence: 99%

“…Pi,j,e is the experimental value of the parameter, and Pi~ is the experimental value for flows 6 and 7 in the wake of a sphere and the cylinder. We define the quality of the model as the percentage mean error for the j-th flow 3 Here, sign(E3j) denotes the sign of the error in predicting the maximum value of the turbulent viscosity. If there are no data on the error E/j for any values of i andj it is assumed that the corresponding value EG=I2.…”

Section: Evaluation Of the "Quality" And Universality Of The Modelmentioning

confidence: 99%

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A universal one-equation model for turbulent viscosity

Gulyaev¹,

Kozlov²,

Sekundov³

1993

Fluid Dyn

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In the eighties, thanks to progress in computational mathematics and the appearance of supercomputers, it seemed that the problems of turbulence would soon be solved either by direct numerical solution of the complete Navier--Stokes equations or by large-scale modeling (solution of the filtered Navier--Stokes equations). For a series of reasons (impossibility of assigning the initial data, nonuniversality of the small-scale part of the spectrum of turbulence, etc.) these hopes were not realized. Now, as before, differential turbulence models are the main tool for solving problems of complex turbulent flow. This applies especially to engineering problems, where the possibility of carrying out a large volume of computations in a short time plays an important part.Modem turbulence models must possess universality, invariance under transformations of the coordinate system, adaptability to numerical methods, and simplicity. At present, there is no model that satisfies all these requirements.In this study the development of a universal one-equation model for the turbulent viscosity v t is continued. The first variant of this model was proposed by Kovasznay [1]. Subsequently, in [2--6] the model was modified and improved. One of the modifications of the model "vt-90" was involved in the "collaborative testing of turbulence models-1990/91" organized by Stanford University [7]. Almost half the hundred participants in this testing program used modifications of the well-known "k--e model" [8]. Many participants used models containing equations for all the components of the Reynolds stress tensor. The inauspicious result of this international effort is the conclusion that none of the models, including the complex multi-equation models, describes the entire spectrum of flows chosen by the organizers (P. Bradshaw, B. Launder, and J. Lumley) for model testing purposes.In this connection, it is desirable to employ the models which are simplest and most economical as regards machine time. The authors of [9], in which a new interesting variant of the turbulent viscosity model is proposed, came to the same conclusion. Discussion of the models with one of the authors of that study --Professor P. Spalart --led to intensification of the work on the new improved variant "vt-92" described below. In addition, a methodology reflecting the views of the authors on how to obtain a quantitative estimate of the accuracy and universality with which a particular model describes real flows is presented. PRELIMINARY REMARKSThe "collaborative testing of turbulence models-1990/91" [7] This model is distinguished by the attempt to take into account the effects associated with the axisymmetry of the flow. For this purpose a correction function, which depends on the parameter r2r 1/vt, where r is determined in accordance with the following rules, is introduced. In the neighborhood of the point x o we introduce a surface A: ~t(x) =const=vt(Xo). We construct a plane B comaining the vectors grad(vt) and curl U. We define r as the radius of curvature of t...

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Section: Formulation Of the "*:92" Modelmentioning

confidence: 99%

Section: Evaluation Of the "Quality" And Universality Of The Modelmentioning

confidence: 99%

A universal one-equation model for turbulent viscosity

Gulyaev¹,

Kozlov²,

Sekundov³

1993

Fluid Dyn

Self Cite

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“…Flow in a channel with rough galls . In [25] it is shown that the one-parameter model [23], with transport equation for the turbulent viscosity v" can be successfully used for calculating flows in channels with rough walls . The particular feature of the problem in this case is that on the rough walls a boundary condition for v, is specified .…”

Section: Channel Flowsmentioning

confidence: 99%

“…In nonequilibrium flows it is necessary to introduce differential equations either for the turbulent viscosity v, (where there are sharp longitudinal variations of the boundary conditions but no regions of negative turbulent viscosity) or for the shear stress s=-(u 'v '). Such models were proposed in [23][24][25][26][27] (equation for v,) and in [6,7] (equation for s) .…”

Section: The Physical Basis Of the Construction Of Mathematical Modmentioning

confidence: 99%

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Turbulent flows. Models and numerical investigations. A review

Luschik¹,

Pavel'ev²,

Yakubenko³

1994

Fluid Dyn

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Russian papers on differential models of turbulence and numerical simulation of nonequilibrium turbulent flows of liquids, gases, and conducting media, published for the most part in this journal over the last 10-15 years, are reviewed .The turbulence models considered in this review are based on Kolmogorovt ideas, which generated a new approach to the mathematical modeling of turbulent flows consisting in the use of transport equations for the turbulence properties . The subsequent development of these models was due to the emergence of computers which made it possible to change over from a qualitative analysis in particular regions to obtaining quantitative results with the influence of viscosity and also such effects as diffusion and convection, taken directly into account in the mathematical simulation of turbulent flows .In this review the models are selected in accordance with the following criteria . 1 . Only differential models are considered, that is models in which transport equations are used for the main turbulence properties : the turbulence energy, shear stress or the turbulent viscosity and a parameter involving the integral turbulence scale . According to the number of the transport equations the models are classified as one-, two-, or three-parameter. The application of the models is restricted to flows for which the boundary layer approximation holds true .2 . The models must have been put to practical use in the analysis of particular flows, and their most efficient areas of application specified . The models must have been tested by comparison with the most reliable experimental data . The models must be highly universal, thus making it possible, without adjusting the constants entering into the model, to take into account the inlet and boundary conditions, the variations of the physical properties of the medium, and external influences .The review aims to demonstrate the potential of the turbulence models considered in relation to a wide variety of flows in boundary layers and channels, and also to draw them to the attention of users and researchers developing scientific and applied computational programs for the description and control of devices with complicated working processes in aviation and space technology, and other areas.

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Developed flow and drag in planar channel with rough walls

Povarnitsyn

1978

Fluid Dyn

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Use of the equation for turbulent viscosity to describe the flow near a rough surface

Cited by 5 publications

References 3 publications

A universal one-equation model for turbulent viscosity

A universal one-equation model for turbulent viscosity

Turbulent flows. Models and numerical investigations. A review

Developed flow and drag in planar channel with rough walls

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