Translating and squirming cylinders in a viscoplastic fluid

Supekar, Rohit; Hewitt, Duncan R.; Balmforth, N. J.

doi:10.1017/jfm.2019.812

Cited by 5 publications

(8 citation statements)

References 30 publications

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“…As our results suggest that higher-order odd modes become more effective at driving microswimmer propulsion as higher Bi, this insinuates the possibility that H. Pylori incorporates a modified mode of locomotion to more effectively swim through the stomach mucus. Related to this, results of two-dimensional squirmers showed that coupling treadmill and mixing modes achieved maximum propulsion at an intermediate Bi value [21]. Finally, real gastric mucus is chemically changed by the bacteria itself.…”

Section: Discussionmentioning

confidence: 76%

“…the Herschel-Bulkley model; here, we use a Bingham fluid model [19] for simplicity while retaining the key viscoplastic component relevant to our biological motivation. Previous studies on swimming in Bingham fluids have been confined to two dimensions [20,21] or for slender bodies [22]. Here, we extend these studies and consider an idealized steady spherical squirmer that employs tangential motions on its boundary.…”

Section: Introductionmentioning

confidence: 95%

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Squirmer locomotion in a yield stress fluid

Eastham¹,

Hadi²,

Shoele³

2022

Preprint

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An axisymmetric squirmer in a Bingham viscoplastic fluid is studied numerically to determine the effect of a yield stress environment on locomotion. The nonlinearity of the governing equations necessitates numerical methods, which is accomplished by solving a variable-viscosity Stokes equation with a Finite Element approach. The effects of stroke modes, both pure and combined, are investigated and it is found that for the treadmill or "neutral" mode, the swimmer in a yield stress fluid has a lower swimming velocity and uses more power. However, the efficiency of swimming reaches its maximum at a finite yield limit. In addition, for higher yield limits, higher stroke modes can increase the swimming velocity and hydrodynamic efficiency of the treadmill swimmer. The higher-order odd-numbered squirming modes, particularly the third stroke mode, can generate propulsion by themselves that increases in strength as the viscoplastic nonlinearity increases till a specific limit. These results are closely correlated with the confinement effects induced by the viscoplastic rigid surface surrounding the swimming body, showing that swimmers in viscoplastic environments, both biological and artificial, could potentially employ other non-standard swimming strategies to optimize their locomotion.

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Section: Discussionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 95%

Squirmer locomotion in a yield stress fluid

Eastham¹,

Hadi²,

Shoele³

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Also Supekar et al. (2020) have shown that the Martin & Randolph (2006) solution is indeed superior compared with the lower bound solution.…”

Section: Methodology and Benchmarkingmentioning

confidence: 99%

“… and directions) are the characteristic lines of the hyperbolic momentum equations in a 2-D flow, known as the sliplines. Finding the sliplines does not require extensive computational effort and therefore this theory has been developed to compare with the viscoplastic ‘yield limit’ for many different problems such as particle sedimentation (Hewitt & Balmforth 2018; Chaparian & Frigaard 2017 a , b ; Chaparian & Tammisola 2021); swimming (Hewitt & Balmforth 2017; Supekar, Hewitt & Balmforth 2020); and different studies in slump/dam-break type problems (Dubash et al. 2009; Liu et al.…”

Section: Methodology and Benchmarkingmentioning

confidence: 99%

Flow onset for a single bubble in a yield-stress fluid

et al. 2021

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We use computational methods to determine the minimal yield stress required in order to hold static a buoyant bubble in a yield-stress liquid. The static limit is governed by the bubble shape, the dimensionless surface tension ( $\gamma$ ) and the ratio of the yield stress to the buoyancy stress ( $Y$ ). For a given geometry, bubbles are static for $Y > Y_c$ , which we determine for a range of shapes. Given that surface tension is negligible, long prolate bubbles require larger yield stress to hold static compared with oblate bubbles. Non-zero $\gamma$ increases $Y_c$ and for large $\gamma$ the yield-capillary number ( $Y/\gamma$ ) determines the static boundary. In this limit, although bubble shape is important, bubble orientation is not. Two-dimensional planar and axisymmetric bubbles are studied.

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“…the Herschel–Bulkley model; here, we use a Bingham fluid model (Saramito 2016) for simplicity while retaining the key viscoplastic component relevant to our biological motivation. Previous studies on swimming in Bingham fluids have been confined to two dimensions (Hewitt & Balmforth 2017; Supekar, Hewitt & Balmforth 2020) or for slender bodies (Hewitt & Balmforth 2018). Here, we extend these studies and consider an idealized steady spherical squirmer that employs tangential motions on its boundary.…”

Section: Introductionmentioning

confidence: 99%

Squirmer locomotion in a yield stress fluid

2022

View full text Add to dashboard Cite

An axisymmetric squirmer in a Bingham viscoplastic fluid is studied numerically to determine the effect of a yield stress environment on locomotion. The nonlinearity of the governing equations necessitates numerical methods, which are accomplished by solving a variable-viscosity Stokes equation with a finite element approach. The effects of stroke modes, both pure and combined, are investigated, and it is found that for the treadmill or ‘neutral’ mode, the swimmer in a yield stress fluid has a lower swimming velocity and uses more power. However, the efficiency of swimming reaches its maximum at a finite yield limit. In addition, for higher yield limits, higher stroke modes can increase the swimming velocity and hydrodynamic efficiency of the treadmill swimmer. The higher-order odd-numbered squirming modes, particularly the third stroke mode, can generate propulsion by themselves that increases in strength as the viscoplastic nonlinearity increases to a specific limit. These results are closely correlated with the confinement effects induced by the viscoplastic rigid surface surrounding the swimming body, showing that swimmers in viscoplastic environments, both biological and artificial, could potentially employ other non-standard swimming strategies to optimize their locomotion.

show abstract

Translating and squirming cylinders in a viscoplastic fluid

Cited by 5 publications

References 30 publications

Squirmer locomotion in a yield stress fluid

Squirmer locomotion in a yield stress fluid

Flow onset for a single bubble in a yield-stress fluid

Squirmer locomotion in a yield stress fluid

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