Vertical distribution and longitudinal dispersion of gyrotactic microorganisms in a horizontal plane Poiseuille flow

Wang, Bohan; Jiang, Weiquan; Chen, Guoqian; Tao, Lan; Li, Zhi

doi:10.1103/physrevfluids.6.054502

Cited by 14 publications

(10 citation statements)

References 62 publications

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“…The equations governing the local moments have been solved by making an eigenfunction expansion and applying a biorthogonal expansion to the eigenfunctions. A constant settling speed, which was not included in Jiang & Chen (2021), is assumed in some cases, and the associated boundary conditions are derived by analysing the fluxes balance. We use the reflective boundary conditions to derive the corresponding basis functions, thus all information of the boundary conditions in the phase space is retained.…”

Section: Discussionmentioning

confidence: 99%

“…(2.19) For cases without sedimentation, i.e. Pe d = 0, the complete reflective boundary conditions are obtained by combining (2.17) and (2.19) , 2020Wang et al 2021):…”

Section: Boundary Conditions and Initial Conditionmentioning

confidence: 99%

“…Following Barton (1983) and Jiang & Chen (2021), we write the transformed local moments G r n in the form of eigenfunction expansion: (2.44) where −λ i and f i are the eigenvalues and eigenfunctions of operator L r with λ i sorted in an ascending order. Here p ni are the undetermined expansion coefficients, λ 1 = 0 and the corresponding eigenfunction f 1 characterises the steady state, which has been discussed in , 2020 and Wang et al (2021).…”

Section: Eigenfunction Expansion Of Local Momentsmentioning

confidence: 99%

“…Long-time asymptotic solution can be obtained with the new GTD method, referred to as 'one-step GTD method'. For the transient dispersion process, Jiang & Chen (2021) derived the time-dependent local moments of probability density function (p.d.f.) of micro-swimmers in the positional-orientational space, by following the expansion of moments derived by Barton (1983) and resorting to the biorthogonal expansion method to the eigenfunctions (Strand, Kim & Karrila 1987;Brezinski 1992).…”

Section: Introductionmentioning

confidence: 99%

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Gyrotactic trapping of micro-swimmers in simple shear flows: a study directly from the fundamental Smoluchowski equation

2022

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Thin phytoplankton layers with vertically compressed structures found in stratified lakes and coastal water bodies have been a hot-spot in marine science and fluid mechanics. Although extensive efforts have been made to explore gyrotactic trapping as a possible mechanism, obvious inconsistencies remain there between the generalised Taylor dispersion method and individual-based model. In this work, a study directly from the fundamental Smoluchowski equation is carried out on the gyrotactic trapping mechanism in representative simple shear flows. With no approximation made to the fundamental equation and applying a biorthogonal expansion to the local moments of the probability density function, the evolution and steady state of the transport process are in good agreement with results of individual-based model, thus removing the gap between the continuum approach and individual-based model. The influences of strongly varying shear rate and boundary effect are reasonably scrutinised. The average swimming orientation with fixed local shear is highlighted as time-dependent rather than steady as previously assumed. The variations of characteristic time of the transient thin layer as functions of the flow intensity, gyrotaxis intensity and swimming ability are characterised. Sedimentation of the micro-swimmers is considered in some cases to reflect that micro-organisms are possibly negatively buoyant, with corresponding boundary conditions devised. A steady thin layer can be realised in the solution by adding a small settling speed to counteract the gravitactic focusing at the upper surface.

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Section: Discussionmentioning

confidence: 99%

“…(2.19) For cases without sedimentation, i.e. Pe d = 0, the complete reflective boundary conditions are obtained by combining (2.17) and (2.19) , 2020Wang et al 2021):…”

Section: Boundary Conditions and Initial Conditionmentioning

confidence: 99%

Section: Eigenfunction Expansion Of Local Momentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gyrotactic trapping of micro-swimmers in simple shear flows: a study directly from the fundamental Smoluchowski equation

2022

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“…In laminar flows, spherical cells accumulate in the center of downwelling vertical pipe flows 4,10 , become trapped in a thin layer of high shear in horizontal shear flows 11,12 . Gyrotactic swimmers are found to accumulate due to gravitactic focusing and wall accumulation in channel Poiseuille flows 13,14 . In turbulent flows, gyrotactic motility can generate small-scale clusters that are dynamically evolving, both when the effect of the fluid acceleration is included or not [15][16][17] .…”

Section: Introductionmentioning

confidence: 99%

Accumulation and alignment of elongated gyrotactic swimmers in turbulence

Liu,

Jiang,

Sun

2022

Preprint

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We study the dynamics of gyrotactic swimmers in turbulence, whose orientation is governed by gravitational torque and local fluid velocity gradient. The gyrotaxis strength is measured by the ratio of the Kolmogorov time scale to the reorientation time scale due to gravity, and a large value of this ratio means the gyrotaxis is strong. By means of direct numerical simulations, we investigate the effects of swimming velocity and gyrotactic stability on spatial accumulation and alignment. Three-dimensional Voronoï analysis is used to study the spatial distribution and time evolution of the particle concentration. We study spatial distribution by examing the overall preferential sampling and where clusters and voids (subsets of particles that have small and large Voronoï volumes respectively) form. Compared with the ensemble particles, the preferential sampling of clusters and voids is found to be more pronounced. The clustering of fast swimmers lasts much longer than slower swimmers when the gyrotaxis is strong and intermediate, but an opposite trend emerges when the gyrotaxis is weak. In addition, we study the preferential alignment with the Lagrangian stretching direction, with which passive slender rods have been known to align. We show that the Lagrangian alignment is reduced by the swimming velocity when the gyrotaxis is weak, while the Lagrangian alignment is enhanced for the regime in which gyrotaxis is strong.

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Analysis of environmental transport of suspended sediment particles in a tidal wetland flow under the effect of floating vegetation absorption

Das,

Dhar,

Kairi

et al. 2024

Communications in Nonlinear Science and Numerical Simulation

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Vertical distribution and longitudinal dispersion of gyrotactic microorganisms in a horizontal plane Poiseuille flow

Cited by 14 publications

References 62 publications

Gyrotactic trapping of micro-swimmers in simple shear flows: a study directly from the fundamental Smoluchowski equation

Gyrotactic trapping of micro-swimmers in simple shear flows: a study directly from the fundamental Smoluchowski equation

Accumulation and alignment of elongated gyrotactic swimmers in turbulence

Analysis of environmental transport of suspended sediment particles in a tidal wetland flow under the effect of floating vegetation absorption

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