Direct numerical simulations of laminar and transitional flows in diverging pipes
Article dans une revue avec comité de lecture
Purpose: Fluid flows in pipes whose cross-sectional area are increasing in the stream-wise direction are prone to separation of the recirculation region. This paper aims to investigate such fluid flow in expansion pipe systems using direct numerical simulations. The flow in circular diverging pipes with different diverging half angles, namely, 45, 26, 14, 7.2 and 4.7 degrees, are considered. The flow is fed by a fully developed laminar parabolic velocity profile at its inlet and is connected to a long straight circular pipe at its downstream to characterise recirculation zone and skin friction coefficient in the laminar regime. The flow is considered linearly stable for Reynolds numbers sufficiently below natural transition. A perturbation is added to the inlet fully developed laminar velocity profile to test the flow response to finite amplitude disturbances and to characterise sub-critical transition. Design/methodology/approach: Direct numerical simulations of the Navier–Stokes equations have been solved using a spectral element method. Findings: It is found that the onset of disordered motion and the dynamics of the localised turbulence patch are controlled by the Reynolds number, the perturbation amplitude and the half angle of the pipe. Originality/value: The authors clarify different stages of flow behaviour under the finite amplitude perturbations and shed more light to flow physics such as existence of Kelvin–Helmholtz instabilities as well as mechanism of turbulent puff shedding in diverging pipe flows.
Files in this item
Showing items related by title, author, creator and subject.
Article dans une revue avec comité de lectureDMOCHOWSKA, Anna; PEIXINHO, Jorge; SOLLOGOUB, Cyrille; MIQUELARD-GARNIER, Guillaume (American Chemical Society (ACS), 2022-04-01)An experimental investigation is reported on the effect of shear on the bursting of molten ultrathin polymer films embedded in an immiscible matrix. By use of an optical microscope coupled with a shearing hot stage, the ...
Article dans une revue avec comité de lecturePINGULKAR, Hrishikesh; PEIXINHO, Jorge; CRUMEYROLLE, Olivier (American Physical Society, 2020)The stretching of viscoelastic polymer solutions close to breakup can create attached drops on a filament, whose properties and dynamics are little understood. The stretching of capillary bridges and the consecutive filament, ...
Article dans une revue avec comité de lectureKADRI, Kheireddin; PEIXINHO, Jorge; SALEZ, Thomas; MIQUELARD-GARNIER, Guillaume; SOLLOGOUB, Cyrille (Elsevier BV, 2021)The objective of this work is to give new insight into the stability of thin polymer films under shear, in order to pave the way to a better control of the nanolayer coextrusion process. To do so, a finite-difference ...
Article dans une revue avec comité de lectureAGEORGES, Valentin; PEIXINHO, Jorge; PERRET, Gaële; LARTIGUE, Ghislain; MOUREAU, Vincent (MDPI AG, 2021)We present the results of a combined experimental and numerical study of the free-surface flow behind a finite height rigid vertical cylinder. The experiments measure the drag and the wake angle on cylinders of different ...
Article dans une revue avec comité de lecturePINGULKAR, Hrishikesh; PEIXINHO, Jorge; CRUMEYROLLE, Olivier (American Chemical Society (ACS), 2021)Viscoelastic liquid transfer from one surface to another is a process that finds applications in many technologies, primarily in printing. Here, cylindrical-shaped capillary bridges pinned between two parallel disks are ...