Influence of Computational Domain Size and Spatial Resolution on DNS of Turbulent Channel Flow with Permeable Walls.

2020 ◽  
Vol 2020.69 (0) ◽  
pp. 509
Author(s):  
Masaya KANNO ◽  
Satoshi YOKOJIMA
Keyword(s):  
Channel Flow ◽  
Spatial Resolution ◽  
Domain Size ◽  
Turbulent Channel Flow ◽  
Computational Domain ◽  
Permeable Walls

scholarly journals Large eddy simulation of turbulent channel flow using differential equation wall model

2018 ◽  
Vol 15 (2) ◽  
pp. 75-89
Author(s):  
Muhammad Saiful Islam Mallik ◽  
Md. Ashraf Uddin
Keyword(s):  
Differential Equation ◽  
Flow Field ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Wall Region ◽  
Computational Domain ◽  
Wall Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Near Wall

A large eddy simulation (LES) of a plane turbulent channel flow is performed at a Reynolds number Re? = 590 based on the channel half width, ? and wall shear velocity, u? by approximating the near wall region using differential equation wall model (DEWM). The simulation is performed in a computational domain of 2?? x 2? x ??. The computational domain is discretized by staggered grid system with 32 x 30 x 32 grid points. In this domain the governing equations of LES are discretized spatially by second order finite difference formulation, and for temporal discretization the third order low-storage Runge-Kutta method is used. Essential turbulence statistics of the computed flow field based on this LES approach are calculated and compared with the available Direct Numerical Simulation (DNS) and LES data where no wall model was used. Comparing the results throughout the calculation domain we have found that the LES results based on DEWM show closer agreement with the DNS data, especially at the near wall region. That is, the LES approach based on DEWM can capture the effects of near wall structures more accurately. Flow structures in the computed flow field in the 3D turbulent channel have also been discussed and compared with LES data using no wall model.

Effects of Spatial Resolution and Box Size on Numerical Solutions of Turbulent Flows

2005 ◽  
Author(s):  
Dongmei Zhou ◽  
Kenneth S. Ball
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
Spatial Resolution ◽  
Numerical Solutions ◽  
Velocity Profiles ◽  
Wall Region ◽  
Computational Domain ◽  
Mean Velocity ◽  
Significant Difference ◽  
Near Wall

This paper has two objectives, (1) to examine the effects of spatial resolution, (2) to examine the effects of computational box size, upon turbulence statistics and the amount of drag reduction with and without the control scheme of wall oscillation. Direct numerical simulation (DNS) of the fully developed turbulent channel flow was performed at Reynolds number of 200 based on the wall-shear velocity and the channel half-width by using spectral methods. For the first objective, four different grids were applied to the same computational domain and the biggest impact was observed on the logarithmic law of mean velocity profiles and on the amount of drag reduction with 28.3% for the coarsest mesh and 35.4% for the finest mesh. Other turbulence features such as RMS velocity fluctuations, RMS vorticity fluctuations, and bursting events were either overpredicted or underpredicted through coarse grids. For the second objective, two different minimal channels and one natural full channel were studied and 3% drag reduction difference was observed between the smallest minimal channel of 39.1% and the natural full channel of 36.2%. In the near-wall region, however, the minimal channel flow did not exhibit significant difference in the mean velocity profiles and other lower-order statistics. Finally, from this systematical study, it showed that the accuracy of DNS depends more on the spanwise resolution, and it also confirmed that a minimal channel model is able to catch key structures of turbulence in the near-wall region but is much less expensive.

1518 Dissimilar heat transfer enhancement using permeable walls in turbulent channel flow

2015 ◽  
Vol 2015 (0) ◽  
pp. _1518-1_-_1518-3_
Author(s):  
Hisaaki HASEGAWA ◽  
Yuuki AOKI ◽  
Kousuke ISHIKAWA ◽  
Genta KAWAHARA ◽  
Markus UHLMANN ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Transfer Enhancement ◽  
Permeable Walls

Modeling the Transport of Fuel Mixture Perturbations and Entropy Waves in the Linearized Framework

2020 ◽  
Author(s):  
Thomas Ludwig Kaiser ◽  
Kilian Oberleithner
Keyword(s):  
Turbulent Flows ◽  
Channel Flow ◽  
Turbulent Mixing ◽  
Equivalence Ratio ◽  
Stokes Equations ◽  
Turbulent Channel Flow ◽  
Passive Scalar ◽  
Computational Domain ◽  
Reynolds Stresses ◽  
Mean Flow

Abstract In this paper a new method is introduced to model the transport of entropy waves and equivalence ratio fluctuations in turbulent flows. The model is based on the Navier-Stokes equations and includes a transport equation for a passive scalar, which may stand for entropy or equivalence ratio fluctuations. The equations are linearized around the mean turbulent fields, which serve as the input to the model in addition to a turbulent eddy viscosity, which accounts for turbulent diffusion of the perturbations. Based on these inputs, the framework is able to predict the linear response of the flow velocity and passive scalar to harmonic perturbations that are imposed at the boundaries of the computational domain. These in this study are fluctuations in the passive scalar and/or velocities at the inlet of a channel flow. The code is first validated against analytic results, showing very good agreement. Then the method is applied to predict the convection, mean flow dispersion and turbulent mixing of passive scalar fluctuations in a turbulent channel flow, which has been studied in previous work with Direct Numerical Simulations (DNS). Results show that our code reproduces the dynamics of coherent passive scalar transport in the DNS with very high accuracy and low numerical costs, when the DNS mean flow and Reynolds stresses are provided. Furthermore, we demonstrate that turbulent mixing has a significant effect on the transport of the passive scalar fluctuations. Finally, we apply the method to explain experimental observations of transport of equivalence ratio fluctuations in the mixing duct of a model burner.

Direct numerical simulation of turbulent channel flow with permeable walls

2002 ◽  
Vol 450 ◽  
pp. 259-285 ◽  
Author(s):  
SEONGHYEON HAHN ◽  
JONGDOO JE ◽  
HAECHEON CHOI
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Direct Numerical Simulation ◽  
Channel Flow ◽  
Reynolds Shear Stress ◽  
Turbulent Channel Flow ◽  
Permeable Wall ◽  
Brinkman Equation ◽  
Navier Stokes Equation ◽  
Permeable Walls

The main objectives of this study are to suggest a proper boundary condition at the interface between a permeable block and turbulent channel flow and to investigate the characteristics of turbulent channel flow with permeable walls. The boundary condition suggested is an extended version of that applied to laminar channel flow by Beavers & Joseph (1967) and describes the behaviour of slip velocities in the streamwise and spanwise directions at the interface between the permeable block and turbulent channel flow. With the proposed boundary condition, direct numerical simulations of turbulent channel flow that is bounded by the permeable wall are performed and significant skin-friction reductions at the permeable wall are obtained with modification of overall flow structures. The viscous sublayer thickness is decreased and the near-wall vortical structures are significantly weakened by the permeable wall. The permeable wall also reduces the turbulence intensities, Reynolds shear stress, and pressure and vorticity fluctuations throughout the channel except very near the wall. The increase of some turbulence quantities there is due to the slip-velocity fluctuations at the wall. The boundary condition proposed for the permeable wall is validated by comparing solutions with those obtained from a separate direct numerical simulation using both the Brinkman equation for the interior of a permeable block and the Navier–Stokes equation for the main channel bounded by a permeable block.

scholarly journals Problems of an experimental study of a reverse flow in the turbulent channel flow

2021 ◽  
Vol 2057 (1) ◽  
pp. 012097
Author(s):  
D I Zaripov
Keyword(s):  
Experimental Study ◽  
Measurement Error ◽  
Channel Flow ◽  
Spatial Resolution ◽  
High Speed ◽  
High Spatial Resolution ◽  
Reverse Flow ◽  
Turbulent Channel Flow ◽  
Measurement Methods ◽  
Piv Measurements

Abstract The problems of experimental study of the near-wall reverse flow (NWRF) phenomenon observed in a turbulent channel flow are discussed. Until now, the problem of detecting the NWRF events has been associated with the lack of spatial resolution of measurement methods. The present study, using the example of high-speed PIV measurements, shows that problems associated with the influence of the measurement error arise even when a high spatial resolution is achieved.

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