Large-eddy simulations of temporally accelerating turbulent channel flow

Talha, Tariq; Chung, Yongmann M.

doi:10.1080/14685248.2015.1052464

Cited by 6 publications

(4 citation statements)

References 29 publications

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“…Taking advantage of the periodic boundary conditions in the two wall-parallel directions, the Poisson equation is solved in the Fourier space with a tridiagonal matrix inversion in the wall-normal direction. The in-house code has been verified extensively in our previous studies (see Chung and Talha 2011;Hurst et al 2014;Talha and Chung 2015).…”

Section: Simulation Setupmentioning

confidence: 99%

Turbulent Drag Reduction by Travelling Waves of Spanwise Lorentz Force

Yang

Chung

2023

Flow Turbulence Combust

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Travelling waves induced by spanwise Lorentz force for skin-friction drag reduction are studied in the present work using direct numerical simulations, with particular focus on the streamwise and spanwise travelling waves. The overall picture of drag reduction in the frequency-wavenumber parameter space, $$\omega -\kappa _x-\kappa _z$$ ω - κ x - κ z is uncovered. It is found that both drag reduction maps for the streamwise and spanwise travelling waves are featured with a drag reduction ($$\mathcal{D}\mathcal{R}$$ D R ) region and a drag increase ($$\mathcal{D}\mathcal{I}$$ D I ) region. For the streamwise travelling wave of spanwise Lorentz force, the $$\mathcal{D}\mathcal{R}$$ D R and $$\mathcal{D}\mathcal{I}$$ D I regions are located in the same parameter regime compared to that of the streamwise travelling wave of spanwise wall velocity, while for the spanwise travelling wave, the $$\mathcal{D}\mathcal{R}$$ D R variation at any fixed $$\kappa _z$$ κ z is similar to that of spanwise oscillating Lorentz force. An exploration of the oblique travelling wave with an angle to the mean flow shows that the optimal drag reduction appears when the wave travels backward relative to the flow direction, and the "ribbon" structure is a general phenomenon appearing in all oblique travelling wave cases. The ensemble averaged positive and negative quasi-streamwise vortices become asymmetric when the travelling wave is imposed, and the near-wall high- and low-speed streaks are significantly tilted in the spanwise direction. Spanwise oscillation, streamwise and spanwise travelling waves share strong similarity in the statistics, energy spectra as well as turbulent structure modulation.

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Section: Simulation Setupmentioning

confidence: 99%

Turbulent Drag Reduction by Travelling Waves of Spanwise Lorentz Force

Yang

Chung

2023

Flow Turbulence Combust

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“…Taking the advantage of the periodic boundary condition in both streamwise and spanwise directions, the Poisson equation is solved in the Fourier space with a tridiagonal matrix inversion in the wall-normal direction. The in-house code has been verified extensively in our previous studies (see Chung and Talha, 2011;Hurst et al, 2014;Talha and Chung, 2015).…”

Section: Simulation Setupmentioning

confidence: 99%

Turbulent Drag Reduction by Travelling Waves of Spanwise Lorentz Force

Yang

Chung

2022

Preprint

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Travelling waves induced by spanwise Lorentz force for skin-friction drag reduction are studied in the present work using direct numerical simulations, with particular focus on the streamwise and spanwise travelling waves. The overall picture of drag reduction in the ω+ − κx+ − κz+ parameter space is uncovered. It is found that both drag reduction maps for the streamwise and spanwise travelling waves are featured with a drag reduction (DR) region and a drag increase (DI) region. For the streamwise travelling wave of spanwise Lorentz force, the DR and DI regions are located in the same parameter regime compared to that of the streamwise travelling wave of spanwise wall velocity, while for the spanwise travelling wave, the DR variation at any fixed κz+ is similar to the spanwise oscillating Lorentz force. An exploration of the oblique travelling wave with an angle to the mean flow shows that the optimal drag reduction appears when the wave travels backward relative to the flow direction, and the “ribbon” structure is a general phenomenon appearing in all oblique travelling wave cases. The ensemble averaged positive and negative quasi-streamwise vortices become asymmetric when the travelling wave is imposed, and the near-wall high- and low-speed streaks are significantly twisted in the spanwise direction. Spanwise oscillation, streamwise and spanwise travelling waves share strong similarity in the statistics, energy spectra as well as turbulent structure modulation.

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“…1990; Lozano-Durán et al. 2020), flows with streamwise acceleration or deceleration (He, Ariyaratne & Vardy 2008, 2011; He & Ariyaratne 2011; Jung & Chung 2012; He & Seddighi 2013, 2015; Talha & Chung 2015; Jung & Kim 2017; Sundstrom & Cervantes 2018 c ; de Wiart, Larsson & Murman 2018), and flows with a streamwise oscillating pressure gradient (Tardu, Binder & Blackwelder 1994; Scotti & Piomelli 2001; Weng, Boij & Hanifi 2016; Sundstrom & Cervantes 2018 b ; Cheng et al. 2020).…”

Section: Introductionmentioning

confidence: 99%

“…While in general non-equilibrium may refer to any flow where the time derivative and/or nonlinear advection terms in the ensemble-averaged momentum balance are non-negligible, in this work we consider only non-stationary flows. Examples considered previously in the direct numerical simulations (DNS), LES and experimental literature include flows with spanwise wall movements in time such as wall oscillations (Jung, Mangiavacchi & Akhavan 1992;Quadrio & Ricco 2003;Ricco et al 2012;Yao, Chen & Hussain 2019), flows where a spanwise pressure gradient is applied suddenly (Moin et al 1990;Lozano-Durán et al 2020), flows with streamwise acceleration or deceleration (He, Ariyaratne & Vardy 2008Jung & Chung 2012;He & Seddighi 2013Talha & Chung 2015;Jung & Kim 2017;Sundstrom & Cervantes 2018c;de Wiart, Larsson & Murman 2018), and flows with a streamwise oscillating pressure gradient (Tardu, Binder & Blackwelder 1994;Scotti & Piomelli 2001;Weng, Boij & Hanifi 2016;Sundstrom & Cervantes 2018b;Cheng et al 2020).…”

Section: Introductionmentioning

confidence: 99%

A multi-time-scale wall model for large-eddy simulations and applications to non-equilibrium channel flows

Fowler,

Zaki,

Meneveau

2023

J. Fluid Mech.

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The recent Lagrangian relaxation towards equilibrium (LaRTE) approach (Fowler et al., J. Fluid Mech., vol. 934, 2022, A44) is a wall model for large-eddy simulations (LES) that isolates quasi-equilibrium wall-stress dynamics from non-equilibrium responses to time-varying LES inputs. Non-equilibrium physics can then be modelled separately, such as the laminar Stokes layers that form in the viscous region and generate rapid wall-stress responses to fast changes in the pressure gradient. To capture additional wall-stress contributions due to near-wall turbulent eddies, a model term motivated by the attached eddy hypothesis is proposed. The total modelled wall stress thus includes contributions from various processes operating at different time scales (i.e. the LaRTE quasi-equilibrium plus laminar and turbulent non-equilibrium wall stresses) and is called the multi-time-scale (MTS) wall model. It is applied in LES of turbulent channel flow subject to a wide range of unsteady conditions from quasi-equilibrium to non-equilibrium. Flows considered include pulsating and linearly accelerating channel flow for several forcing frequencies and acceleration rates, respectively. We also revisit the sudden spanwise pressure gradient flow (considered in Fowler et al., J. Fluid Mech., vol. 934, 2022, A44) to review how the newly introduced model features affect this flow. Results obtained with the MTS wall model show good agreement with direct numerical simulation data over a vast range of conditions in these various non-equilibrium channel flows. To further understand the MTS model, we also describe and test the instantaneous-equilibrium limit of the MTS wall model. In this limit, good wall-stress predictions are obtained with reduced model complexity but providing less complete information about the wall-stress physics.

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Large-eddy simulations of temporally accelerating turbulent channel flow

Cited by 6 publications

References 29 publications

Turbulent Drag Reduction by Travelling Waves of Spanwise Lorentz Force

Turbulent Drag Reduction by Travelling Waves of Spanwise Lorentz Force

Turbulent Drag Reduction by Travelling Waves of Spanwise Lorentz Force

A multi-time-scale wall model for large-eddy simulations and applications to non-equilibrium channel flows

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