Anisotropic stresslet and rheology of stick–slip Janus spheres

Premlata, A. R.; Wei, Hsien Hung

doi:10.1017/jfm.2022.481

Cited by 2 publications

(6 citation statements)

References 27 publications

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“…Here, the coefficient h 1 (α) comes from a combination of the surface octupole and dipole, and h 2 (α) is constituted by the surface hexadecapole and quadrupole (Premlata & Wei 2022). These coefficients vary with the stick-slip partition angle α and the average dimensionless slip length (2.19a) according to…”

Section: Stressletmentioning

confidence: 99%

“…For simplicity, we consider a two-faced slip pattern in terms of a partition angle α, such as that sketched in figure 2( a ), to specify The slip length jumps from aλ R on the right face to aλ L on the left face so that the average dimensionless slip length and the strength of the surface quadrupole are Carrying out the integrals in (2.13) (see Appendix C), we can use (2.18) to determine the swimming velocity below after taking a small ε expansion and keeping the terms to O ( ε ) Here, e i is set to be the swimming direction (towards the right in figure 2 a ) of the squirmer without stick-slip disparity. The coefficient f 1 ( α ) is contributed from the surface quadrupole (2.19 b ), and f 2 ( α ) comes from a combination of the surface octupole and dipole (Premlata & Wei 2022). These coefficients vary with the stick-slip partition angle α and the average dimensionless slip length (2.19 a ) according to Note that α = 0 and α = π recover no-slip and uniform-slip squirmers, respectively.…”

Section: Reciprocal Theorem Formulation For a Stick-slip Spherical Sq...mentioning

confidence: 99%

“…For the stick-slip pattern (2.18) considered here, the stresslet calculated from (2.31) (with the details given in Appendix D) is found to be Here, the coefficient h 1 ( α ) comes from a combination of the surface octupole and dipole, and h 2 ( α ) is constituted by the surface hexadecapole and quadrupole (Premlata & Wei 2022). These coefficients vary with the stick-slip partition angle α and the average dimensionless slip length (2.19 a ) according to The limiting cases α = 0 and α = π in (2.33) recover the stresslets for no-slip and uniform-slip squirmers, respectively.…”

Section: Reciprocal Theorem Formulation For a Stick-slip Spherical Sq...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…On the fundamental side, this work is motivated by the fact that a slip asymmetry can break the symmetry of the local hydrodynamic force distribution on the surface of an otherwise no-slip or uniform-slip spherical particle (Premlata & Wei 2021, 2022). It has been shown that a stick-slip sphere can behave quite differently from a no-slip or uniform-slip sphere (Premlata & Wei 2021, 2022). For example, the former can migrate when it is placed at the centre of a purely straining flow field, whereas the latter under this same situation does not migrate at all (Premlata & Wei 2021).…”

Section: Introductionmentioning

confidence: 99%

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Stick-slip squirmers: slip asymmetry can qualitatively change self-swimming characteristics of squirmers

et al. 2023

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A slip asymmetry can break the fore–aft symmetry of the local hydrodynamic force distribution on the surface of an otherwise no-slip or uniform-slip particle. Here, we use the Lorentz reciprocal theorem to demonstrate that such asymmetry, even in a fractional amount, can qualitatively alter the swimming characteristics of a self-propelled spherical squirmer, markedly different from those of no-slip or uniform-slip squirmers. Unlike the usual tangential squirming by the thrust-providing B1 mode and the type-determining B2 mode, we discover two unique features for a stick-slip squirmer. First, the squirmer can acquire a swimming velocity U without the B1 mode but simply by a symmetric extensile/contractile squirming from the B2 mode, which is able to reverse the swimming direction of the squirmer. Second, a stresslet $\boldsymbol{\mathsf{S}}$ can also be induced by a unidirectional squirming from the B1 mode, capable of inverting the squirmer's stresslet from extensile type to contractile type or vice versa to change the squirmer from puller to pusher or in a reverse manner. We further show that the two squirming modes can reinforce or compete with each other to enhance or diminish U and $\boldsymbol{\mathsf{S}}$ due to interplays between the asymmetric squirming forces on the stick and the slip faces. A phase diagram is also established to categorize a variety of newly emerging swimming states, such as an enhanced/degraded puller/pusher and a backward puller/pusher, depending on the relative strength of the squirming modes β = B2/B1, the direction of the stick-slip polarity and the degree of the slip disparity. As a result of such cooperative and competitive natures, a stick-slip squirmer can swim more or less efficiently than no-slip and uniform-slip ones. These distinctive features arising from stick-slip disparity can not only be made geometrically tuneable for steering the motion of a squirmer, but also provide new means for making efficient artificial microswimmers using amphiphilic Janus particles.

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Section: Stressletmentioning

confidence: 99%

Section: Reciprocal Theorem Formulation For a Stick-slip Spherical Sq...mentioning

confidence: 99%

Section: Reciprocal Theorem Formulation For a Stick-slip Spherical Sq...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stick-slip squirmers: slip asymmetry can qualitatively change self-swimming characteristics of squirmers

et al. 2023

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On the Hinch–Kim dualism between singularity and Faxén operators in the hydromechanics of arbitrary bodies in Stokes flows

Procopio,

Giona

2024

Physics of Fluids

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We generalize the multipole expansion and the structure of the Faxén operator in Stokes flows obtained for bodies with no-slip to generic boundary conditions, addressing the assumptions under which this generalization is conceivable. We show that a disturbance field generated by a body immersed in an ambient flow can be expressed, independently on the boundary conditions, as a multipole expansion, the coefficients of which are the moments of the volume forces. We find that the dualism between the operator giving the disturbance field of an nth order ambient flow and the nth order Faxén operator, referred to as the Hinch–Kim dualism, holds only if the boundary conditions satisfy a property that we call Boundary-Condition reciprocity (BC-reciprocity). If this property is fulfilled, the Faxén operators can be expressed in terms of the (m, n)th order geometrical moments of the volume forces (defined in the article). In addition, it is shown that in these cases, the hydromechanics of the fluid-body system is completely determined by the entire set of the Faxén operators. Finally, classical boundary conditions of hydrodynamic applications are investigated in light of this property: boundary conditions for rigid bodies, Newtonian drops at the mechanical equilibrium, porous bodies modeled by the Brinkman equations are BC-reciprocal, while deforming linear elastic bodies, deforming Newtonian drops, non-Newtonian drops, and porous bodies modeled by the Darcy equations do not have this property. For Navier-slip boundary conditions on a rigid body, we find the analytical expression for low order Faxén operators. By using these operators, the closed form expressions for the flow past a sphere with arbitrary slip length immersed in shear and quadratic flows are obtained.

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Anisotropic stresslet and rheology of stick–slip Janus spheres

Cited by 2 publications

References 27 publications

Stick-slip squirmers: slip asymmetry can qualitatively change self-swimming characteristics of squirmers

Stick-slip squirmers: slip asymmetry can qualitatively change self-swimming characteristics of squirmers

On the Hinch–Kim dualism between singularity and Faxén operators in the hydromechanics of arbitrary bodies in Stokes flows

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