

Artikel
Stability of Fluids with ShearDependent Viscosity in the LidDriven Cavity
Författare: 
Haque, S., Lashgari, I., Giannetti, F., Brandt, L.B. 
Dokumenttyp: 
Artikel 
Tillstånd: 
Publicerad 
Tidskrift: 
J. NonNewtonian Fluid Mech. 
Volym: 
173174
4961 
År: 
2012 
AbstractThe classical problem of the liddriven cavity extended infinitely in the spanwise direction is considered for nonNewtonian shearthinning and shearthickening fluids, where the viscosity is modeled by the Carreau model. Linear stability is used to determine the critical Reynolds number at which the two dimensional baseflow becomes unstable to threedimensional spanwiseperiodic disturbances. We con sider a square cavity, characterized by steady unstable modes, and a shallow cavity of aspect ratio 0.25, where oscillating modes are the first to become unstable for Newtonian fluids. In both cases, the critical Reynolds number first decreases with decreasing powerindex n (from shearthickening to shearthin ning fluids) and then increase again for highly pseudoplastic fluids. In the latter case, this is explained by the thinner boundary layers at the cavity walls and less intense vorticity inside the domain. Interest ingly, oscillating modes are found at critical conditions for shearthickening fluids in a square cavity while the shallow cavity supports a new instability of lower frequency for large enough shearthinning. Analysis of kinetic energy budgets and structural sensitivity are employed to investigate the physical mechanisms behind the instability.

