Turbulent Channel Flow with Spatially-Dependent Viscosity: A Numerical Study

2021 ◽  
Author(s):  
Victor Coppo Leite ◽  
Elia Merzari
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Variable Viscosity ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Turbulent Channel Flow ◽  
Viscosity Change ◽  
Dependent Viscosity

Abstract In the present study, we examine in detail the effect of spatially dependent viscosity on wall-bounded flow. For this purpose, Direct Numerical Simulations (DNS) are performed considering a channel flow with a viscosity change along the streamwise direction. The DNS were performed using Nek5000, a computational fluid dynamic code developed at Argonne National Laboratory. The channel is divided in three different regions: in the first one, the flow is at a constant Reynolds number of Re = 5000; in the second region, the Reynolds number is imposed to linearly increase as viscosity decreases through a ramp; finally, in the third region the flow is again at a constant Reynolds number, this time at Re = 10000. Since the temperature field is not evaluated, the proposed set up is a simplification of a heated channel. Nevertheless, the outcomes of this study may be valuable for future works considering variable-viscosity effects, especially for cooling and heating applications. Four test cases with different ramp inclinations were analyzed. The results from the present study were compared with a correlation available in the literature for the friction Reynolds number as a function of the Reynolds number. We observe that in all cases the ramp does not cause an immediate change in the characteristics of turbulent structures and a delay is in fact observed in both wall shear and friction. Finally, in order to characterize and understand these effects, streaks from the viscous region and turbulence statistics for the turbulent kinetic energy budget terms are analyzed.

Numerical study of high-order Lagrangian structure functions in a turbulent channel flow with low Reynolds number

2010 ◽  
Vol 22 (S1) ◽  
pp. 215-218 ◽  
Author(s):  
Jian-ping Luo ◽  
Zhi-ming Lu ◽  
TatsLo Ushijima ◽  
Osami Kitoh ◽  
Xiang Qiu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Turbulent Channel Flow ◽  
Structure Functions ◽  
High Order ◽  
Low Reynolds

Direct numerical simulation of turbulent channel flow up to

2015 ◽  
Vol 774 ◽  
pp. 395-415 ◽  
Author(s):  
Myoungkyu Lee ◽  
Robert D. Moser
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Mean Velocity ◽  
Layer Structures ◽  
High Reynolds

A direct numerical simulation of incompressible channel flow at a friction Reynolds number ($\mathit{Re}_{{\it\tau}}$) of 5186 has been performed, and the flow exhibits a number of the characteristics of high-Reynolds-number wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Kármán constant ${\it\kappa}=0.384\pm 0.004$. There is also a logarithmic dependence of the variance of the spanwise velocity component, though not the streamwise component. A distinct separation of scales exists between the large outer-layer structures and small inner-layer structures. At intermediate distances from the wall, the one-dimensional spectrum of the streamwise velocity fluctuation in both the streamwise and spanwise directions exhibits $k^{-1}$ dependence over a short range in wavenumber $(k)$. Further, consistent with previous experimental observations, when these spectra are multiplied by $k$ (premultiplied spectra), they have a bimodal structure with local peaks located at wavenumbers on either side of the $k^{-1}$ range.

Evolution of wall shear stress with Reynolds number in fully developed turbulent channel flow experiments

2019 ◽  
Vol 4 (7) ◽  
Author(s):  
Pierre-Alain Gubian ◽  
Jordan Stoker ◽  
James Medvescek ◽  
Laurent Mydlarski ◽  
B. Rabi Baliga
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Wall Shear ◽  
Flow Experiments

Deposition of Small Particles From Turbulent Flows

2003 ◽  
Author(s):  
Z. Wu ◽  
J. B. Young
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Numerical Study ◽  
Turbulent Channel Flow ◽  
Brownian Diffusion ◽  
Small Particles ◽  
Two Fluid

This paper deals with particle deposition onto solid walls from turbulent flows. The aim of the study is to model particle deposition in industrial flows, such as the one in gas turbines. The numerical study has been carried out with a two fluid approach. The possible contribution to the deposition from Brownian diffusion, turbulent diffusion and shear-induced lift force are considered in the study. Three types of turbulent two-phase flows have been studied: turbulent channel flow, turbulent flow in a bent duct and turbulent flow in a turbine blade cascade. In the turbulent channel flow case, the numerical results from a two-dimensional code show good agreement with numerical and experimental results from other resources. Deposition problem in a bent duct flow is introduced to study the effect of curvature. Finally, the deposition of small particles on a cascade of turbine blades is simulated. The results show that the current two fluid models are capable of predicting particle deposition rates in complex industrial flows.

Small-scale anisotropy in turbulent boundary layers

2016 ◽  
Vol 804 ◽  
pp. 5-23 ◽  
Author(s):  
Alain Pumir ◽  
Haitao Xu ◽  
Eric D. Siggia
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Isotropic Turbulence ◽  
Turbulent Channel Flow ◽  
Statistical Properties ◽  
Simultaneous Action ◽  
Large Reynolds Number ◽  
Small Scale ◽  
Velocity Fluctuations ◽  
Scale Properties

In a channel flow, the velocity fluctuations are inhomogeneous and anisotropic. Yet, the small-scale properties of the flow are expected to behave in an isotropic manner in the very-large-Reynolds-number limit. We consider the statistical properties of small-scale velocity fluctuations in a turbulent channel flow at moderately high Reynolds number ($Re_{\unicode[STIX]{x1D70F}}\approx 1000$), using the Johns Hopkins University Turbulence Database. Away from the wall, in the logarithmic layer, the skewness of the normal derivative of the streamwise velocity fluctuation is approximately constant, of order 1, while the Reynolds number based on the Taylor scale is $R_{\unicode[STIX]{x1D706}}\approx 150$. This defines a small-scale anisotropy that is stronger than in turbulent homogeneous shear flows at comparable values of $R_{\unicode[STIX]{x1D706}}$. In contrast, the vorticity–strain correlations that characterize homogeneous isotropic turbulence are nearly unchanged in channel flow even though they do vary with distance from the wall with an exponent that can be inferred from the local dissipation. Our results demonstrate that the statistical properties of the fluctuating velocity gradient in turbulent channel flow are characterized, on one hand, by observables that are insensitive to the anisotropy, and behave as in homogeneous isotropic flows, and on the other hand by quantities that are much more sensitive to the anisotropy. How this seemingly contradictory situation emerges from the simultaneous action of the flux of energy to small scales and the transport of momentum away from the wall remains to be elucidated.

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