Assessment of Shear Stress Transport Model with Its Variant for Heat Transfer Problems

2020 ◽  
Vol 34 (3) ◽  
pp. 640-649
Author(s):  
M. M. Rahman
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Transport Model ◽  
Shear Stress Transport ◽  
Shear Stress Transport Model ◽  
Transfer Problems

scholarly journals MODELING HEAT EXCHANGE DEPENDING ON THE PRANDTL NUMBER FOR VARIOUS GEOMETRIC AND REGIME PARAMETERS

2020 ◽  
Vol 46 (4) ◽  
pp. 91-101
Author(s):  
I. E. Lobanov
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Prandtl Number ◽  
Energy Equation ◽  
Transport Model ◽  
Reynolds Numbers ◽  
Structured Grids ◽  
Shear Stress Transport Model ◽  
Small Reynolds Numbers ◽  
Prandtl Numbers

Objectives. The aim is to study the dependency of the distribution of integral heat transfer during turbulent convective heat transfer in a pipe with a sequence of periodic protrusions of semicircular geometry on the Prandtl number using the calculation method based on a numerical solution of the system of Reynolds equations closed using the Menter’s shear stress transport model and the energy equation on different-sized intersecting structured grids.Method. A calculation was carried out on the basis of a theoretical method based on the solution of the Reynolds equations by factored finite-volume method closed with the help of the Menter shear stress transport model, as well as the energy equation on different-scaled intersecting structured grids (fast composite mesh method (FCOM)).Results. The calculations performed in the work showed that with an increase in the Prandtl number at small Reynolds numbers, there is an initial noticeable increase in the relative heat transfer. With additional increase in the Prandtl number, the relative heat transfer changes less: for small steps, it increases; for median steps it is almost stabilised, while for large steps it declines insignificantly. At large Reynolds numbers, the relative heat transfer decreases with an increase in the Prandtl number followed by its further stabilisation.Conclusion. The study analyses the calculated dependencies of the relative heat transfer on the Pr Prandtl number for various values of the relative h/D height of the turbulator, the relative t/D pitch between the turbulators and for various values of the Re Reynolds number. Qualitative and quantitative changes in calculated parameters are described all other things being equal. The analytical substantiation of the obtained calculation laws is that the height of the turbuliser is less for small Reynolds numbers, while for large Reynolds numbers, it is less than the height of the wall layer. Consequently, only the core of the flow is turbulised, which results in an increase in hydroresistance and a decrease in heat transfer. In the work on the basis of limited calculation material, a tangible decrease in the level of heat transfer intensification for small Prandtl numbers is theoretically confirmed. The obtained results of intensified heat transfer in the region of low Prandtl numbers substantiate the promising development of research in this direction. The theoretical data obtained in the work have determined the laws of relative heat transfer across a wide range of Prandtl numbers, including in those areas where experimental material does not currently exist. 

A Comparative Analysis of Turbulence Models Utilised for the Prediction of Turbulent Airflow through a Sudden Expansion

2015 ◽  
Vol 16 ◽  
pp. 64-78 ◽  
Author(s):  
Karinate Valentine Okiy
Keyword(s):  
Shear Stress ◽  
Convergence Rate ◽  
Transport Model ◽  
Turbulence Models ◽  
Sudden Expansion ◽  
Circular Duct ◽  
Shear Stress Transport ◽  
Shear Stress Transport Model ◽  
Turbulent Airflow ◽  
Recirculation Length

The turbulent airflow in a circular duct with sudden expansion was investigated utilizing three turbulence models. The turbulence models chosen are: the k-epsilon model, the shear stress transport model and the Reynolds-stress model. The performance of the models was investigated with respect to the flow parameter-recirculation length. The turbulent kinetic energy and velocity predictions were compared between the turbulence models and with experimental data, then interpreted on the basis of the recirculation length. From the results, the shear stress transport model predictions of recirculation length had the closest agreement with the experimental result compared to the other model. Likewise, the convergence rate for the shear stress transport model was reasonable compared to that of the Reynolds model which has the slowest convergence rate. In light of these findings, the shear stress transport model was discovered to be the most appropriate for the investigation of turbulent air flow in a circular duct with sudden expansion. Keywords: Turbulence, recirculation length, sudden expansion, Turbulence models.

Roughness Corrections for the k–ω Shear Stress Transport Model: Status and Proposals

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
B. Aupoix
Keyword(s):  
Shear Stress ◽  
Transport Model ◽  
Wall Region ◽  
Large Set ◽  
Transition Regime ◽  
Wall Roughness ◽  
Shear Stress Transport ◽  
Sst Model ◽  
Shear Stress Transport Model ◽  
Simplified Analysis

Various corrections were previously proposed to account for wall roughness with the k–ω and shear stress transport (SST) models. A simplified analysis, based upon the wall region analysis, is proposed to characterize the behavior of these roughness corrections. As this analysis points out some deficiencies for each correction, two new corrections are proposed for the SST model, to reproduce different behaviors, mainly in the transition regime. The correction development is based upon a previously developed strategy. A large set of boundary layer experiments is used to compare the different roughness corrections, confirm the failures of previous proposals, and validate the present ones. Moreover, it assesses the proposed simplified analysis. It also evidences the difficulty to determine the equivalent sand grain roughness for a given surface. The Colebrook based correction is recommended while the Nikuradse based one can add information about the envelope of possible behaviors in the transition regime.

Numerical investigation of V-shaped riblets and an improved model of riblet effects

2017 ◽  
Vol 232 (9) ◽  
pp. 1622-1631 ◽  
Author(s):  
Yu Yang ◽  
Zhang Ming-Ming ◽  
Li Xue-Song
Keyword(s):  
Shear Stress ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Turbulence Models ◽  
Friction Reduction ◽  
Group Model ◽  
Shear Stress Transport ◽  
Shear Stress Transport Model ◽  
Skin Friction Reduction ◽  
Improved Model

Symmetric V-shaped riblets are simulated by using the computational fluid dynamic method to understand the riblet effects on the turbulent boundary layer and the skin friction reduction. Three classical turbulence models, namely Spalart–Allmaras, shear stress transport, and re-normalization group k-epsilon models, are investigated under different grid densities. The re-normalization group model produces good results consistent with the experiment, as compared with the existing theoretical and experimental drag results of the flat plate and the V-shaped riblets with different sizes. Simulating V-shaped riblets yield the unexpected discovery that the shear stress transport model produces large errors, and the Spalart–Allmaras model even produces results of qualitative errors. Another finding is that von Kármán’s constants can no longer meet the requirement of describing velocity profiles in the logarithmic law layer. Aside from the traditional shift of the logarithmic law’s intercept, the slope is also changed by riblet height and spacing. Therefore, an improved model of riblet effects is proposed by redefining von Kármán’s constants.

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