Effect of the hydrodynamic pressure on shaft torque for a 4-blades vane rheometer

Abstract

Vane type geometries are often used in rheometers to avoid slippage between the sample and the solid boundaries. Thus in commercial firms, universities and research institutes, vane type geometries are often applied to obtain accurate isothermal flow parameters. Recently, a detailed analysis of the complex flow phenomena inside such device was made using the finite element method (Nazari et al., 2013). In particular, the shaft torque was calculated at different angular velocities and compared to experimental data. Here, this work is repeated by using the finite volume method. In addition to this, the effect of hydrodynamic pressure on the shaft torque is analyzed separately and compared to the effect generated by viscous stress. This analysis is done for the two Newtonian fluids reported in Nazari et al. (2013), as well as for two cases of viscoplastic Bingham fluids. Including this, mesh independence is also analyzed. The outcome of the overall analysis is that the effect of hydrodynamic pressure constitutes about 2/3 of the shaft torque, leaving only about 1/3 of the torque to viscous stress.