The exact regularized point particle method is used to characterize the turbulence modulation in two-way momentum-coupled direct numerical simulations of a turbulent pipe flow. The turbulence modification is parametrized by the particle Stokes number, the mass loading, and the particle-to-fluid density ratio. The data show that in the wide region of the parameter space addressed in the present paper, the overall friction drag is either increased or unaltered by the particles with respect to the uncoupled case. In the cases where the wall friction is enhanced, the fluid velocity fluctuations show a substantial modification in the viscous sub-layer and in the buffer layer. These effects are associated with a modified turbulent momentum flux toward the wall. The particles suppress the turbulent fluctuations in the buffer region and concurrently provide extra stress in the viscous sub-layer. The sum of the turbulent stress and the extra stress is larger than the Newtonian turbulent stress, thus explaining the drag increase. The non-trivial turbulence/particles interaction turns out in a clear alteration of the near-wall flow structures. The streamwise velocity streaks lose their spatial coherence when two-way coupling effects are predominant. This is associated with a shift of the streamwise vortices toward the center of the pipe and with the concurrent presence of small-scale and relatively more intense vortical structures near the wall.

Drag increase and turbulence augmentation in two-way coupled particle-laden wall-bounded flows / Battista, Francesco; Gualtieri, Paolo; Mollicone, JEAN-PAUL; Salvadore, Francesco; Casciola, Carlo Massimo. - In: PHYSICS OF FLUIDS. - ISSN 1527-2435. - 35:4(2023). [10.1063/5.0141964]

Drag increase and turbulence augmentation in two-way coupled particle-laden wall-bounded flows

Battista Francesco
;
Gualtieri Paolo;Mollicone Jean-Paul;Casciola Carlo Massimo
2023

Abstract

The exact regularized point particle method is used to characterize the turbulence modulation in two-way momentum-coupled direct numerical simulations of a turbulent pipe flow. The turbulence modification is parametrized by the particle Stokes number, the mass loading, and the particle-to-fluid density ratio. The data show that in the wide region of the parameter space addressed in the present paper, the overall friction drag is either increased or unaltered by the particles with respect to the uncoupled case. In the cases where the wall friction is enhanced, the fluid velocity fluctuations show a substantial modification in the viscous sub-layer and in the buffer layer. These effects are associated with a modified turbulent momentum flux toward the wall. The particles suppress the turbulent fluctuations in the buffer region and concurrently provide extra stress in the viscous sub-layer. The sum of the turbulent stress and the extra stress is larger than the Newtonian turbulent stress, thus explaining the drag increase. The non-trivial turbulence/particles interaction turns out in a clear alteration of the near-wall flow structures. The streamwise velocity streaks lose their spatial coherence when two-way coupling effects are predominant. This is associated with a shift of the streamwise vortices toward the center of the pipe and with the concurrent presence of small-scale and relatively more intense vortical structures near the wall.
2023
engineering controlled terms buffer layers; channel flow; drag; friction; numerical methods; turbulent flow; wall flow engineering uncontrolled terms coupled particles; particle methods; particle-laden; poin-particles; regularized point; turbulence modulation; turbulent stress; two ways; viscous sublayer; wall bounded flows engineering main heading turbulence
01 Pubblicazione su rivista::01a Articolo in rivista
Drag increase and turbulence augmentation in two-way coupled particle-laden wall-bounded flows / Battista, Francesco; Gualtieri, Paolo; Mollicone, JEAN-PAUL; Salvadore, Francesco; Casciola, Carlo Massimo. - In: PHYSICS OF FLUIDS. - ISSN 1527-2435. - 35:4(2023). [10.1063/5.0141964]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1689873
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