Rough Wall Modification of Two-Layer k−ε

Durbin, Paul A.; Medic, Gorazd; Seo, Jongmin; Eaton, John K.; Song, Seok Goo

doi:10.1115/1.1343086

Cited by 101 publications

(48 citation statements)

References 9 publications

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“…Turbulence models have therefore received considerable attention in a great number of publications, e.g. [9,10,20,26,53,57,66,67,72].…”

Section: Turbulence Modelsmentioning

confidence: 99%

Numerical Flow Calculations

Gülich¹

2014

Centrifugal Pumps

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Real flows are described by partial differential equations which cannot be solved analytically in the general case. By dividing a complex flow domain into a multitude of small cells, these equations can be solved in an approximate manner by numerical methods. Because of their wide range of application, numerical flow calculations ("computational fluid dynamics" or "CFD" for short) have become a special discipline of fluid dynamics.The information given in this chapter is intended to help the understanding and interpretation of numerical flow calculations of centrifugal pumps. The focus is on viscous methods since these provide the best chance of describing realistically the boundary layers and secondary flows in decelerated flow on curved paths as encountered in radial and semi-axial pumps. This statement is not meant to preclude that simpler methods may be applied meaningfully to make a first design.The following discussion of CFD methods and possibilities focuses also on limits and uncertainties of CFD modeling as well as on quality criteria and issues in CFD applications, Sects. 8.3.2, 8.3.3, 8.8 and 8.10. OverviewBecause of the complex flow phenomena in centrifugal pumps, the design of impellers, diffusers, volutes and inlet casings is frequently based on empirical data for determining the flow deflection in the impeller and estimating performance and losses. The design of flow channels and blades then relies on experience and coefficients which originate from test data, Chaps. 3 and 7. The availability of relatively inexpensive computers with high computing powers has fostered the development of numerical methods which are able to solve the 3-dimensional Navier-Stokesequations in complex components with reasonable effort. Therefore, numerical methods are used also in the pump industry with the object of optimizing the hydraulic components, to increase the reliability of performance prediction and thus to reduce testing costs. Computational fluid dynamics are still in a phase of development.

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“…Turbulence models have therefore received considerable attention in a great number of publications, e.g. [9,10,20,26,53,57,66,67,72].…”

Section: Turbulence Modelsmentioning

confidence: 99%

Numerical Flow Calculations

Gülich¹

2014

Centrifugal Pumps

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“…Based on the sand grain roughness, Durbin et al (2001) proposed a rough wall modification for the two layer k − ǫ model. An effective displacement of the wall distance origin was introduced and related to the sand grain roughness height through a calibration procedure.…”

Section: Approaches To Calculate a Fully Turbulent Boundary Layer On mentioning

confidence: 99%

An intermittency model for predicting roughness induced transition

Durbin

2015

International Journal of Heat and Fluid Flow

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An intermittency transport equation for RANS modeling, formulated in local variables, is extended for roughness-induced transition. To predict roughness effects in the fully turbulent boundary layer, published boundary conditions for k and ω are used. They depend on the equivalent sand-grain roughness height, and account for the effective displacement of wall distance origin. Similarly in our approach, wall distance in the transition model for smooth surfaces is modified by an effective origin, which depends on equivalent sandgrain roughness. Flat plate test cases are computed to show that the proposed model is able to predict transition onset in agreement with a data correlation of transition location versus roughness height, Reynolds number, and inlet turbulence intensity. Experimental data for turbine cascades are compared to the predicted results to validate the proposed model. AbstractAn intermittency transport equation for RANS modeling, formulated in local variables, is extended for roughness-induced transition. To predict roughness effects in the fully turbulent boundary layer, published boundary conditions for k and ω are used. They depend on the equivalent sand-grain roughness height, and account for the effective displacement of wall distance origin. Similarly in our approach, wall distance in the transition model for smooth surfaces is modified by an effective origin, which depends on equivalent sand-grain roughness. Flat plate test cases are computed to show that the proposed model is able to predict transition onset in agreement with a data correlation of transition location versus roughness height, Reynolds number, and inlet turbulence intensity. Experimental data for turbine cascades are compared to the predicted results to validate the proposed model.

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“…For two-layer k − models, Durbin et al (2001) suggested a quadratic interpolation for the transitional regime between a plane interface where the turbulent kinetic energy is zero (k = 0), and to the fully rough interface. The corresponding boundary condition for the turbulent kinetic energy above and below the interface took the form…”

Section: Application In Turbulence Modelsmentioning

confidence: 99%

“…Many two-phase turbulence models for pipe and channel flow rely on interfacial friction models to predict the turbulent (axial) momentum flux transported over the interface from one fluid to the other. In Reynolds averaged models, such as k − models, one adopts an interfacial friction model that is often modelled in terms of a roughness scale (e.g., Durbin et al, 2001;Berthelsen and Ytrehus, 2005;Biberg, 2007;de Sampaio et al, 2008), and it is of importance to develop reasonable roughness scale models that can respond to the length, time and energy scales of the turbulence near the interface. Perhaps the most obvious natural system where the roughness scale is central, is the coupling between the ocean surface and the overlying wind (e.g., Charnock, 1955;Wu, 1980;Fernando, 1991).…”

mentioning

confidence: 99%

On the interfacial roughness scale in turbulent stratified two-phase flow: 3D lattice Boltzmann numerical simulations with forced turbulence and surfactant

Skartlien

Sollum

Fakharian

et al. 2015

International Journal of Multiphase Flow

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Numerical simulations of turbulent, stratified two-phase flow with a surfactant laden interface were analyzed. The turbulence was forced in the upper and lower liquids to emulate the dynamics of an interface between turbulent fluids, without requiring (prohibitively) large simulation domains. This setup was used to test and develop a phenomenological roughness scale model where we assume that the energy required to deform the interface (buoyancy, interfacial tension, and viscous work) is proportional to the turbulent kinetic energy adjacent to the interface. The addition of surfactant lead to an increased roughness scale (for the same turbulent kinetic energy) due to the introduction of interfacial dilatational elasticity that suppressed horizontal motion parallel to the interface, and enhanced the vertical motion. We foresee that the phenomenological roughness model can be used as a building block for more general interfacial closure relations in Reynolds averaged turbulence models where also mobile surfactant is accounted for. *

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Rough Wall Modification of Two-Layer k−ε

Cited by 101 publications

References 9 publications

Numerical Flow Calculations

Numerical Flow Calculations

An intermittency model for predicting roughness induced transition

On the interfacial roughness scale in turbulent stratified two-phase flow: 3D lattice Boltzmann numerical simulations with forced turbulence and surfactant

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