Dynamic fluid–structure interaction of an elastic capsule in a viscous shear flow at moderate Reynolds number

• Published in: Journal of fluids and structures Vol. 27; no. 3; pp. 438 - 455
• Main Authors: Song, Chanyi, Shin, Soo Jai, Sung, Hyung Jin, Chang, Keun-Shik
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.04.2011; Elsevier
• Subjects: Capsule membrane; Computational fluid dynamics; Computational methods in fluid dynamics; Couette flow; Dynamics; Elastic capsule; Exact sciences and technology; Flows in ducts, channels, nozzles, and conduits; Fluid dynamics; Fluid flow; Fluid-structure interaction; Fluids; Fundamental areas of phenomenology (including applications); Immersed boundary method; Mathematical analysis; Membranes; Physics; Pulsatile shear; Reynolds number; Shear flow; Simple shear; Solid mechanics; Static elasticity (thermoelasticity...); Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Elastic capsule; Capsule membrane; Couette flow; Simple shear; Pulsatile shear; Immersed boundary method; Transient response; Membranes; Phase shift; Shear flow; Reynolds number; Cyclic loads; Fluid-structure interactions; Vibrations; Subharmonic; Capsules; Pulsatile flow; Inertia; Modelling; Viscous fluids; Structural analysis; Viscous flow; Mechanical tension
• ISSN: 0889-9746; 1095-8622
• DOI: 10.1016/j.jfluidstructs.2010.11.011

The unsteady behavior of a 2-D circular elastic capsule was investigated in three viscous shear flows. An immersed boundary method (IBM) has been used to solve the dynamic fluid–structure interaction of the capsule. Computations were carried out in finite parameter ranges where the Reynolds number is Re=1–40 and the capillary number is Ca=0.0005–0.05, which is the ratio of the external viscous shear stress to the resistant elastic tensions of the membrane. For the simple shear flow, the effect of inertia on the transient behavior of the capsule was studied. For the pulsatile shear flow, two values of the peak fluid strain, T f =1 and 5, were considered for the quasi-steady capsule mechanics. The capsule shows a cyclic structural response that includes subharmonics as the Reynolds number is elevated to 10 and 40. The capsule dynamic response includes a phase lag, which is a function of the capillary number, the Reynolds number, and the peak fluid strain. Finally, the capsule flowing in the Couette flow shows lateral migration due to the transient lift force, which is higher for lower Ca and higher Re. When capsules with diverse elasticity are dispersed along the velocity gradient, the capsule with a hard membrane experienced greater lift than the one with a soft membrane.