Characterization of Time-Averaged Turbulence Statistics for Shear Thinning Fluid in Horizontal Concentric Annulus Using RANS Based CFD Simulation

2016 ◽  
Author(s):  
Xiao Xiong ◽  
Mohammad Azizur Rahman ◽  
Yan Zhang
Keyword(s):  
Cfd Simulation ◽  
Model Simulation ◽  
Polymer Concentration ◽  
Shear Thinning ◽  
Turbulent Shear ◽  
Wall Region ◽  
Turbulence Statistics ◽  
Concentric Annulus ◽  
Sst Model ◽  
Shear Thinning Fluid

A RANS based shear stress transportation (SST) model was employed in this study to validate experimental results from a recent literature, which investigated the fully developed turbulent flow for a non-Newtonian shear thinning fluid, containing drag reduction polymer additives in a horizontal concentric annulus (inner to outer radio θ = 0.4). The polymer concentration varied from 0.07% V/V to 0.12% V/V and three mass flow rates from 3.92 kg/s to 5.95 kg/s were analyzed. The viscous property of the fluid was modeled by the power-law model. Simulation performed with the commercial code of ANSYS-CFX indicated that the SST model with default model constants overestimated the turbulence statistics of shear thinning flow in the near wall region where y+<60. As an effort to improve simulation accuracy, one of the model constants α1 was tuned in this study for the first time. Simulation results obtained from the modified model showed better agreement with experimental data compared to those from the default one. The present study represents a successful benchmark task for simulating turbulent shear thinning flow in concentric annuli with modified turbulence model constants.

A CFD Simulation of Near Wall Turbulent Flow in Concentric Annulus

2013 ◽  
Author(s):  
Aziz Rahman ◽  
Fabio Ernesto Rodriguez Corredor ◽  
Majid Bizhani ◽  
Ergun Kuru
Keyword(s):  
Experimental Data ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Water Flow ◽  
Simulation Study ◽  
Cfd Simulation ◽  
Concentric Annulus ◽  
Sst Model ◽  
Cfd Analyses ◽  
Near Wall

A CFD simulation study was conducted to analyse the near wall turbulence characteristics of water flow through concentric annulus. The continuity and momentum equations were solved by using a commercial CFD package (CFX 14) with the Shear-Stress-Transport (SST) model option. The simulation results were compared to the experimental data obtained by using high resolution Particle Image Velocimetry (PIV) analyses of water flow in a horizontal concentric annulus. A fully developed turbulent flow of water through a horizontal flow loop (ID = 9.5 cm) with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was used for comparison purpose. Reynolds number ranged from 17,500 to 68,500. Annular velocity profile obtained from simulation study showed good agreement with the experimental data. Near wall velocity profile obtained from CFD simulation followed the universal wall law (u+ = y+) up to y+ = 11. CFD analyses using the SST model resulted a good number of velocity data up to y+ = 11, which is normally a very difficult task to achieve experimentally. The CFD analyses using SST model is computationally inexpensive and therefore, can be conveniently used for investigating the near wall turbulent characteristics of flow in concentric annulus.

scholarly journals Soft Matter Emerging Investigators Issue 2021 - "Propulsion of an elastic filament in a shear-thinning fluid at low Reynolds numbers"

Soft Matter ◽  
2021 ◽  
Author(s):  
Ke Qin ◽  
Zhiwei Peng ◽  
Ye Chen ◽  
Herve Nganguia ◽  
Lailai Zhu ◽  
...  
Keyword(s):  
Soft Matter ◽  
Reynolds Numbers ◽  
Shear Thinning ◽  
Low Reynolds Numbers ◽  
Elastic Filament ◽  
Low Reynolds ◽  
Micro Organisms ◽  
Surrounding Fluid ◽  
Shear Thinning Fluid ◽  
Flexible Appendages

Some micro-organisms and artificial micro-swimmers propel at low Reynolds numbers (Re) via the interaction of their flexible appendages with the surrounding fluid. While their locomotion have been extensively studied with...

scholarly journals Swimming efficiency in a shear-thinning fluid

2017 ◽  
Vol 96 (6) ◽  
Author(s):  
Herve Nganguia ◽  
Kyle Pietrzyk ◽  
On Shun Pak
Keyword(s):  
Shear Thinning ◽  
Swimming Efficiency ◽  
Shear Thinning Fluid

The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 2—Fluctuation Quantities

1996 ◽  
Vol 118 (4) ◽  
pp. 728-736 ◽  
Author(s):  
S. P. Mislevy ◽  
T. Wang
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Transition Region ◽  
Boundary Layers ◽  
Reynolds Shear Stress ◽  
Turbulent Shear ◽  
Wall Region ◽  
Pressure Gradients ◽  
Baseline Case ◽  
Near Wall

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6 percent. Boundary layer measurements were conducted for two constant-K cases, K1 = −0.51 × 10−6 and K2 = −1.05 × 10−6. The fluctuation quantities, u′, ν′, t′, the Reynolds shear stress (uν), and the Reynolds heat fluxes (νt and ut) were measured. In general, u′/U∞, ν′/U∞, and νt have higher values across the boundary layer for the adverse pressure-gradient cases than they do for the baseline case (K = 0). The development of ν′ for the adverse pressure gradients was more actively involved than that of the baseline. In the early transition region, the Reynolds shear stress distribution for the K2 case showed a near-wall region of high-turbulent shear generated at Y+ = 7. At stations farther downstream, this near-wall shear reduced in magnitude, while a second region of high-turbulent shear developed at Y+ = 70. For the baseline case, however, the maximum turbulent shear in the transition region was generated at Y+ = 70, and no near-wall high-shear region was seen. Stronger adverse pressure gradients appear to produce more uniform and higher t′ in the near-wall region (Y+ < 20) in both transitional and turbulent boundary layers. The instantaneous velocity signals did not show any clear turbulent/nonturbulent demarcations in the transition region. Increasingly stronger adverse pressure gradients seemed to produce large non turbulent unsteadiness (or instability waves) at a similar magnitude as the turbulent fluctuations such that the production of turbulent spots was obscured. The turbulent spots could not be identified visually or through conventional conditional-sampling schemes. In addition, the streamwise evolution of eddy viscosity, turbulent thermal diffusivity, and Prt, are also presented.

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