### Abstract

For highly non-uniformly flowing fluids, there are contributions to the stress related to spatial variations of the shear rate, which are commonly referred to as non-local stresses. The standard expression for the shear stress, which states that the shear stress is proportional to the shear rate, is based on a formal expansion of the stress tensor with respect to spatial gradients in the flow velocity up to leading order. Such a leading order expansion is not able to describe fluids with very rapid spatial variations of the shear rate, like in micro-fluidics devices and in shear-banding suspensions. Spatial derivatives of the shear rate then significantly contribute to the stress. Such non-local stresses have so far been introduced on a phenomenological level. In particular, a formal gradient expansion of the stress tensor beyond the above mentioned leading order contribution leads to a phenomenological formulation of non-local stresses in terms of the so-called "shear-curvature viscosity". We derive an expression for the shear-curvature viscosity for dilute suspensions of spherical colloids and propose an effective-medium approach to extend this result to concentrated suspensions. The validity of the effective-medium prediction is confirmed by Brownian dynamics simulations on highly non-uniformly flowing fluids.

Original language | English |
---|---|

Article number | 014903 |

Journal | Journal of chemical physics |

Volume | 149 |

Issue number | 1 |

DOIs | |

Publication status | Published - 7 Jul 2018 |

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*Journal of chemical physics*,

*149*(1), [014903]. https://doi.org/10.1063/1.5035268

}

*Journal of chemical physics*, vol. 149, no. 1, 014903. https://doi.org/10.1063/1.5035268

**Non-local stresses in highly non-uniformly flowing suspensions : The shear-curvature viscosity.** / Jin, H.; Kang, K.; Ahn, K.H.; Briels, W.J. (Corresponding Author); Dhont, J.K.G. (Corresponding Author).

Research output: Contribution to journal › Article › Academic › peer-review

TY - JOUR

T1 - Non-local stresses in highly non-uniformly flowing suspensions

T2 - The shear-curvature viscosity

AU - Jin, H.

AU - Kang, K.

AU - Ahn, K.H.

AU - Briels, W.J.

AU - Dhont, J.K.G.

PY - 2018/7/7

Y1 - 2018/7/7

N2 - For highly non-uniformly flowing fluids, there are contributions to the stress related to spatial variations of the shear rate, which are commonly referred to as non-local stresses. The standard expression for the shear stress, which states that the shear stress is proportional to the shear rate, is based on a formal expansion of the stress tensor with respect to spatial gradients in the flow velocity up to leading order. Such a leading order expansion is not able to describe fluids with very rapid spatial variations of the shear rate, like in micro-fluidics devices and in shear-banding suspensions. Spatial derivatives of the shear rate then significantly contribute to the stress. Such non-local stresses have so far been introduced on a phenomenological level. In particular, a formal gradient expansion of the stress tensor beyond the above mentioned leading order contribution leads to a phenomenological formulation of non-local stresses in terms of the so-called "shear-curvature viscosity". We derive an expression for the shear-curvature viscosity for dilute suspensions of spherical colloids and propose an effective-medium approach to extend this result to concentrated suspensions. The validity of the effective-medium prediction is confirmed by Brownian dynamics simulations on highly non-uniformly flowing fluids.

AB - For highly non-uniformly flowing fluids, there are contributions to the stress related to spatial variations of the shear rate, which are commonly referred to as non-local stresses. The standard expression for the shear stress, which states that the shear stress is proportional to the shear rate, is based on a formal expansion of the stress tensor with respect to spatial gradients in the flow velocity up to leading order. Such a leading order expansion is not able to describe fluids with very rapid spatial variations of the shear rate, like in micro-fluidics devices and in shear-banding suspensions. Spatial derivatives of the shear rate then significantly contribute to the stress. Such non-local stresses have so far been introduced on a phenomenological level. In particular, a formal gradient expansion of the stress tensor beyond the above mentioned leading order contribution leads to a phenomenological formulation of non-local stresses in terms of the so-called "shear-curvature viscosity". We derive an expression for the shear-curvature viscosity for dilute suspensions of spherical colloids and propose an effective-medium approach to extend this result to concentrated suspensions. The validity of the effective-medium prediction is confirmed by Brownian dynamics simulations on highly non-uniformly flowing fluids.

UR - http://www.scopus.com/inward/record.url?scp=85049654999&partnerID=8YFLogxK

U2 - 10.1063/1.5035268

DO - 10.1063/1.5035268

M3 - Article

VL - 149

JO - Journal of chemical physics

JF - Journal of chemical physics

SN - 0021-9606

IS - 1

M1 - 014903

ER -