Influence of the inlet velocity profile on the flow stability in a symmetric channel expansion

Debuysschère, Robin; Siconolfi, Lorenzo; Rimez, Bart; Gallaire, François; Scheid, Benoît

doi:10.1017/jfm.2020.912

Cited by 6 publications

(9 citation statements)

References 31 publications

(53 reference statements)

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“…As presented in table 3, the results closely match. We also present the critical Reynolds number obtained for both geometric configurations in table 4, which is in good agreement with the direct numerical simulation (DNS) and LSA results of Debuysschère et al (2021). , 2, 4, 6, 10, 25).…”

Section: Grid Independence Study and Validationsupporting

confidence: 82%

“…For validation, we compare the length of the recirculation region obtained from our simulations using a steady inlet against that of Debuysschère et al. (2021). As presented in table 3, the results closely match.…”

Section: Resultsmentioning

confidence: 99%

“…Drikakis (1997) also examined various numerical schemes in their ability to predict Re c and found that higher-order finite-difference schemes accurately predict symmetry-breaking phenomena. Recently, Debuysschère et al (2021) investigated the influence of inlet velocity profiles on flow stability in a sudden expansion channel. Their inlet profiles varied from plug to Poiseuille profiles, with several intermediate ones.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Debuysschère et al. (2021) investigated the influence of inlet velocity profiles on flow stability in a sudden expansion channel. Their inlet profiles varied from plug to Poiseuille profiles, with several intermediate ones.…”

Section: Introductionmentioning

confidence: 99%

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Periodic flow features in a planar sudden expansion with pulsatile inflow velocity

Sarkar,

Roy

2024

J. Fluid Mech.

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Flow through sudden expansion finds its application in several engineering and biological processes. Though the stability of flow through steady sudden expansion has garnered much attention, little to none is given to the pulsatile flow through sudden expansion. Hence, in the present work we study the influence of inflow pulsatility on flow characteristics in a sudden expansion. The inflow velocity is a sinusoidal waveform that is modulated to encompass a wide range of amplitudes, ${{a}}$ , and reduced velocities, ${{U_{r}}}$ . We report four different modes, namely, synchronized growth of the recirculation region (at high ${{U_{r}}}$ ), necking and diffusion of the recirculation region (at moderately high ${{U_{r}}}$ ), splitting and convection of the recirculation region (at moderate ${{U_{r}}}$ ) and inverse growth of the recirculation region (at low ${{U_{r}}}$ ). In each mode, the symmetry-breaking critical Reynolds number is obtained through numerical experiments and compared with those of Floquet stability analysis. We found that diffusion and the convection mode of the recirculation region increases the stability of the flow while the inverse growth mode of the recirculation region decreases the same. The effect of the expansion ratio, ${{ER}}$ , is also explored, and we found that as ${{ER}}$ increases, the absolute stability of flow decreases, but relative stability between the modes remains similar. Finally, we explain the dynamics of the modes by using terms involving the vorticity transport equation.

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Section: Grid Independence Study and Validationsupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Periodic flow features in a planar sudden expansion with pulsatile inflow velocity

Sarkar,

Roy

2024

J. Fluid Mech.

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“…The length of the recirculation zone L C , which is defined as the maximum distance between the pinch outlet and the x-position of the area where the longitudinal flow speed u x = 0 (Debuysschère et al 2020), is illustrated in the inset of Fig. 6 for Re = 96 .…”

Section: Flow Descriptionmentioning

confidence: 99%

Enhanced pinch flow fractionation using inertial streamline crossing

Timary

Cappello

Scheid

2022

Microfluid Nanofluid

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In this work, we study the influence of inertia on the dynamics of neutrally buoyant spherical microbeads of varying diameter in a Pinch Flow Fractionation device. To that aim, we monitor their trajectory over an unprecedented wide range of flow rates and flow rate ratios. Our experimental results are supplemented by a depth-averaged 2D-model where the flow is described using the Navier-Stokes equation coupled with the shallow channel approximation and where particles trajectories are computed from Newton's second law of motion with a particle tracing model. Above a certain flow rate, we show that particles inertia enables them to cross streamlines in response to an abrupt change of direction. These streamline crossing events combined with the increasing effect of the inertial lift forces drive particles to deviate from the inertialess trajectory. The amplitude of the resulting inertial deviation increases both with the particles diameter and the total flow rate before reaching a plateau. Consequently, based on our numerical and experimental results, we determine the optimal flow conditions to shift the particles distribution to significantly enhance their size-based separation.

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Mathematical model and analysis method for flowfield separation and transition

Peng

Xiao

et al. 2021

Physics of Fluids

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Transition and separation are difficult but important problems in the field of fluid mechanics. Hitherto, separation and transition problems have not been described accurately in mathematical terms, leading to design errors and prediction problems in fluid machine engineering. The nonlinear uncertainty involved in separation and transition makes it difficult to accurately analyze these phenomena using experimental methods. Thus, new ideas and methods are required for the mathematical prediction of fluid separation and transition. In this article, after an axiomatic treatment of fluid mechanics, the concept of an excited state is derived by generating a fluctuation velocity, and it is revealed that fluid separation and transition are special forms of this excited state. This allows us to clarify the state conditions of fluid separation and transition. Mathematical analysis of the Navier–Stokes equations leads to a general excited state theorem suitable for flowfields. Finally, the conditions of separation and transition are derived, and the corresponding general laws are established. The results presented in this article provide a foundation for future research on the mechanism of turbulence and the solution of engineering problems.

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Influence of the inlet velocity profile on the flow stability in a symmetric channel expansion

Abstract: Abstract

Cited by 6 publications

References 31 publications

Periodic flow features in a planar sudden expansion with pulsatile inflow velocity

Periodic flow features in a planar sudden expansion with pulsatile inflow velocity

Enhanced pinch flow fractionation using inertial streamline crossing

Mathematical model and analysis method for flowfield separation and transition

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