Abstract:
In this study, a rotating cylinder is placed in a stream of shear-thinning fluids, flowing
with a uniform velocity. Detailed investigations are performed for the following range of
conditions: Reynolds number 100 Re 500, power-law index 0:2 n 1 and rotational velocity 0 a 5. Flow transitions are observed from steady to unsteady at critical values of the Reynolds number, the rotational velocity, and the power-law index.
Critical values of the Reynolds number Rec have been obtained for varying levels of the
rotational velocity, and the power-law index. Rec varies nonmonotonically with the rotational velocity. At a particular Reynolds number, an increase of the rotational velocity
acts as a vortex suppression technique. For shear-thinning fluids considered here, the
vortex suppression occurs at a larger value of the critical rotational velocity ac, relative
to Newtonian fluids. For the unsteady flow, the lift coefficient versus time curve exhibits
oscillatory behavior, and this has been used to delineate the flow regime as steady or
unsteady flow. For unsteady flow regimes, both the amplitude of the lift coefficient and
the Strouhal number increase with increasing Reynolds numbers. The results presented
in this work for such high Reynolds numbers elucidate the possible complex interplay
between the kinematic and rheological parameters of non-Newtonian fluids. This investigation also complements the currently available low Reynolds number results up
to Re ¼ 140
