TY - JOUR

T1 - Rheology of a dense suspension of spherical capsules under simple shear flow

AU - Matsunaga, D.

AU - Imai, Y.

AU - Yamaguchi, T.

AU - Ishikawa, T.

N1 - Publisher Copyright:
© © 2015 Cambridge University PressA.

PY - 2015/11/30

Y1 - 2015/11/30

N2 - We present a numerical analysis of the rheology of a dense suspension of spherical capsules in simple shear flow in the Stokes flow regime. The behaviour of neo-Hookean capsules is simulated for a volume fraction up to by graphics processing unit computing based on the boundary element method with a multipole expansion. To describe the specific viscosity using a polynomial equation of the volume fraction, the coefficients of the equation are calculated by least-squares fitting. The results suggest that the effect of higher-order terms is much smaller for capsule suspensions than rigid sphere suspensions; for example, terms account for only 8A % of the specific viscosity even at for capillary numbers . We also investigate the relationship between the deformation and orientation of the capsules and the suspension rheology. When the volume fraction increases, the deformation of the capsules increases while the orientation angle of the capsules with respect to the flow direction decreases. Therefore, both the specific viscosity and the normal stress difference increase with volume fraction due to the increased deformation, whereas the decreased orientation angle suppresses the specific viscosity, but amplifies the normal stress difference.

AB - We present a numerical analysis of the rheology of a dense suspension of spherical capsules in simple shear flow in the Stokes flow regime. The behaviour of neo-Hookean capsules is simulated for a volume fraction up to by graphics processing unit computing based on the boundary element method with a multipole expansion. To describe the specific viscosity using a polynomial equation of the volume fraction, the coefficients of the equation are calculated by least-squares fitting. The results suggest that the effect of higher-order terms is much smaller for capsule suspensions than rigid sphere suspensions; for example, terms account for only 8A % of the specific viscosity even at for capillary numbers . We also investigate the relationship between the deformation and orientation of the capsules and the suspension rheology. When the volume fraction increases, the deformation of the capsules increases while the orientation angle of the capsules with respect to the flow direction decreases. Therefore, both the specific viscosity and the normal stress difference increase with volume fraction due to the increased deformation, whereas the decreased orientation angle suppresses the specific viscosity, but amplifies the normal stress difference.

KW - boundary integral methods

KW - capsule/cell dynamics

KW - suspensions

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U2 - 10.1017/jfm.2015.666

DO - 10.1017/jfm.2015.666

M3 - Article

AN - SCOPUS:84949489021

SN - 0022-1120

VL - 786

SP - 110

EP - 127

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

ER -