REYNOLDS ANALOGY IN TURBULENT FLOWS OVER ROUGH WALLS - A DNS INVESTIGATION

2018 ◽  
Author(s):  
Pourya Forooghi ◽  
Franco Magagnato ◽  
Bettina Frohnapfel
Keyword(s):  
Turbulent Flows ◽  
Reynolds Analogy ◽  
Rough Walls

Investigation of an Algebraic Reynolds Stress Model for Simulation of Wall-Bounded Turbulent Flows With and Without Buoyancy Effects

2020 ◽  
Author(s):  
Tausif Jamal ◽  
D. Keith Walters
Keyword(s):  
Heat Flux ◽  
Turbulent Flows ◽  
Reynolds Stress ◽  
Nuclear Reactor ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Reynolds Analogy ◽  
Suitable Alternative ◽  
Rans Models ◽  
Algebraic Reynolds Stress Model

Abstract Complex turbulent flows such as those encountered in nuclear reactor cooling systems pose considerable challenges for computational fluid dynamics (CFD) simulation using traditional Reynolds-averaged Navier-Stokes (RANS) models based on the linear eddy-viscosity modeling (LEVM) framework. One particular difficulty is the use of low Prandtl number (Pr) fluids such as liquid metal coolants, which considerably alters the fluctuating thermal field and violates the Reynolds analogy upon which turbulent heat flux modeling in LEVMs is based. Although previous studies have shown that Reynolds Stress Models (RSM) offer some improvements over traditional LEVMs for flows containing complex inter-component interaction and Reynolds stress anisotropy, the added complexity, increased computational requirements, and the lack of robustness introduced by traditional RSMs do not always result in an overall improvement. This study evaluates the performance of a newly proposed Algebraic Reynolds Stress Model (ARSM) including an Algebraic Heat Flux Model (AHFM) against two industry standard RANS models, standard k-ε and realizable k-ε model, for a set of canonical test cases relevant to nuclear reactor cooling applications. Numerical simulations using the spectral element code Nek5000 are performed for fully developed channel flows with varying values of Reynolds number (Re) and Pr, both with and without the effects of buoyancy. Results are compared to Direct Numerical Simulation (DNS) data in terms of the velocity and thermal statistics. For all cases investigated, the ARSM model consistently outperforms the other RANS models in this study and it is concluded that the new ARSM model can be a suitable alternative to traditional LEVMs for complex turbulent flows without significant penalty to efficiency and robustness that are commonly associated with traditional RSMs.

Thermal patterns on the smooth and rough walls in turbulent flows

1999 ◽  
Vol 42 (20) ◽  
pp. 3815-3829 ◽  
Author(s):  
G Hetsroni ◽  
A Mosyak ◽  
R Rozenblit ◽  
L.P Yarin
Keyword(s):  
Turbulent Flows ◽  
Rough Walls ◽  
Thermal Patterns

Reynolds Analogy in High-Enthalpy and High-Mach-Number Turbulent Flows

AIAA Journal ◽  
2006 ◽  
Vol 44 (4) ◽  
pp. 917-919 ◽  
Author(s):  
M. V. Suraweera ◽  
D. J. Mee ◽  
R. J. Stalker
Keyword(s):  
Mach Number ◽  
Turbulent Flows ◽  
Reynolds Analogy ◽  
High Enthalpy ◽  
High Mach Number ◽  
High Mach

scholarly journals Heat Transfer and Fluid Mechanics Measurements in Transitional Boundary Layer Flows

1985 ◽  
Vol 107 (4) ◽  
pp. 1007-1015 ◽  
Author(s):  
T. Wang ◽  
T. W. Simon ◽  
J. Buddhavarapu
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Plate Boundary ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Shear Stresses ◽  
Boundary Layer Flows ◽  
Transfer Coefficients ◽  
Reynolds Analogy ◽  
Heat Transfer Coefficients

Experimental results are presented to document hydrodynamic and thermal development of flat-plate boundary layers undergoing natural transition. Local heat transfer coefficients, skin friction coefficients, and profiles of velocity, temperature, and Reynolds normal and shear stresses are presented. A case with no transition and transitional cases with 0.68 percent and 2.0 percent free-stream disturbance intensities were investigated. The locations of transition are consistent with earlier data. A late-laminar state with significant levels of turbulence is documented. In late-transitional and early-turbulent flows, turbulent Prandtl number and conduction layer thickness values exceed, and the Reynolds analogy factor is less than, values previously measured in fully turbulent flows.

scholarly journals Assessment of Solution Algorithms for LES of Turbulent Flows Using OpenFOAM

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 171 ◽  
Author(s):  
Santiago López Castaño ◽  
Andrea Petronio ◽  
Giovanni Petris and Vincenzo Armenio 
Keyword(s):  
Turbulent Flows ◽  
Mixed Model ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Subgrid Scale ◽  
Reynolds Analogy ◽  
Navier Stokes Equations ◽  
Hexahedral Meshes ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

We validate and test two algorithms for the time integration of the Boussinesq form of the Navier—Stokes equations within the Large Eddy Simulation (LES) methodology for turbulent flows. The algorithms are implemented in the OpenFOAM framework. From one side, we have implemented an energy-conserving incremental-pressure Runge–Kutta (RK4) projection method for the solution of the Navier–Stokes equations together with a dynamic Lagrangian mixed model for momentum and scalar subgrid-scale (SGS) fluxes; from the other side we revisit the PISO algorithm present in OpenFOAM (pisoFoam) in conjunction with the dynamic eddy-viscosity model for SGS momentum fluxes and a Reynolds Analogy for the scalar SGS fluxes, and used for the study of turbulent channel flows and buoyancy-driven flows. In both cases the validity of the anisotropic filter function, suited for non-homogeneous hexahedral meshes, has been studied and proven to be useful for industrial LES. Preliminary tests on energy-conservation properties of the algorithms studied (without the inclusion of the subgrid-scale models) show the superiority of RK4 over pisoFoam, which exhibits dissipative features. We carried out additional tests for wall-bounded channel flow and for Rayleigh–Bènard convection in the turbulent regime, by running LES using both algorithms. Results show the RK4 algorithm together with the dynamic Lagrangian mixed model gives better results in the cases analyzed for both first- and second-order statistics. On the other hand, the dissipative features of pisoFoam detected in the previous tests reflect in a less accurate evaluation of the statistics of the turbulent field, although the presence of the subgrid-scale model improves the quality of the results compared to a correspondent coarse direct numerical simulation. In case of Rayleigh–Bénard convection, the results of pisoFoam improve with increasing values of Rayleigh number, and this may be attributed to the Reynolds Analogy used for the subgrid-scale temperature fluxes. Finally, we point out that the present analysis holds for hexahedral meshes. More research is need for extension of the methods proposed to general unstructured grids.

A generalized Reynolds analogy for compressible wall-bounded turbulent flows

2013 ◽  
Vol 739 ◽  
pp. 392-420 ◽  
Author(s):  
You-Sheng Zhang ◽  
Wei-Tao Bi ◽  
Fazle Hussain ◽  
Zhen-Su She
Keyword(s):  
Mach Number ◽  
Prandtl Number ◽  
Boundary Layers ◽  
Turbulent Flows ◽  
Wall Temperature ◽  
Velocity Fields ◽  
Recovery Factor ◽  
Mean Velocity ◽  
Reynolds Analogy ◽  
The Mean

AbstractA generalized Reynolds analogy (GRA) is proposed for compressible wall-bounded turbulent flows (CWTFs) and validated by direct numerical simulations. By introducing a general recovery factor, a similarity between the Reynolds-averaged momentum and energy equations is established for the canonical CWTFs (i.e. pipes, channels, and flat-plate boundary layers that meet the quasi-one-dimensional flow approximation), independent of Prandtl number, wall temperature, Mach number, Reynolds number, and pressure gradient. This similarity and the relationships between temperature and velocity fields constitute the GRA. The GRA relationship between the mean temperature and the mean velocity takes the same quadratic form as Walz’s equation, with the adiabatic recovery factor replaced by the general recovery factor, and extends the validity of the latter to diabatic compressible turbulent boundary layers and channel/pipe flows. It also derives Duan & Martín’s (J. Fluid Mech., vol. 684, 2011, pp. 25–59) empirical relation for flows at different physical conditions (wall temperature, Mach number, enthalpy condition, surface catalysis, etc.). Several key parameters besides the general recovery factor emerge in the GRA. An effective turbulent Prandtl number is shown to be the reason for the parabolic profile of mean temperature versus mean velocity, and it approximates unity in the fully turbulent region. A dimensionless wall temperature, that we call the diabatic parameter, characterizes the wall-temperature effects in diabatic flows. The GRA also extends the analysis to the fluctuation fields. It recovers the modified strong Reynolds analogy proposed by Huang, Coleman & Bradshaw (J. Fluid Mech., vol. 305, 1995, pp. 185–218) and explains the variation of the temperature–velocity correlation coefficient with wall temperature. Thus, the GRA unveils a generalized similarity principle behind the complex nonlinear coupling between the thermal and velocity fields of CWTFs.

scholarly journals Entropy Generation Assessment for Wall-Bounded Turbulent Shear Flows Based on Reynolds Analogy Assumptions

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1157 ◽  
Author(s):  
Matthias Ziefuss ◽  
Nader Karimi ◽  
Florian Ries ◽  
Amsini Sadiki ◽  
Amirfarhang Mehdizadeh
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Entropy Generation ◽  
Shear Flows ◽  
Turbulent Heat Transfer ◽  
Turbulent Shear ◽  
General Notion ◽  
Turbulent Heat ◽  
Reynolds Analogy ◽  
Transfer Models

Heat transfer modeling plays a major role in design and optimization of modern and efficient thermal-fluid systems. Further, turbulent flows are thermodynamic processes, and thus, the second law of thermodynamics can be used for critical evaluations of such heat transfer models. However, currently available heat transfer models suffer from a fundamental shortcoming: their development is based on the general notion that accurate prediction of the flow field will guarantee an appropriate prediction of the thermal field, known as the . In this work, an assessment of the capability of the in predicting turbulent heat transfer when applied to shear flows of fluids of different Prandtl numbers will be given. Towards this, a detailed analysis of the predictive capabilities of the concerning entropy generation is presented for steady and unsteady state simulations. It turns out that the provides acceptable results only for mean entropy generation, while fails to predict entropy generation at small/sub-grid scales.

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