Wagging regime

Mewis, J.M. Vermant, J. Moldenaers, P. Experimental evidence for the existence of a wagging regime in polymeric liquid crystals. Macromolecules 1997, 30 (5), 1323-1328. 

Larson s results [154] are divided into the three shear rate regimes - tumbling, wagging, and steady-state - as explained below. He chose the strength of mean-field potential 2L2dc in Eq. (41) to be 10.67, which corresponds to the concentration cA of the nematic phase coexisting with the isotropic phase (in the second virial approximation), and expressed the shear rate in terms of T defined by... 

Model input parameters were based on independent field and laboratory observations that used subsurface media similar to that at the WAG 5 field facility. The mean pore-water velocity (v) of the fracture regime was estimated from measured... 

The dynamics of the dipole-dipole interaction tensor was averaged over each proton of the complex, and had a correlation time around 50 ps. Due to the rigidity of the complex, the decay in the TCP was caused by reorientation of the whole complex and the wagging motion of the water molecules. The fluctuations of symmetry was studied both from the individual water molecules distortion from their ideal symmetry positions and from the symmetry modes of the complex. The symmetry modes were well defined for the oxygen atoms in the water molecule, which show small distortions. The orientations of the water molecules, on the other hand, were too widely distributed from such an analysis to be meaningful. The time scale of the symmetry modes was in the sub-picosecond regime, much too fast to be correlated to the dipole-dipole interaction tensor. Hence, the decomposition of the total TCP into a spin part and a space part is well motivated. 

This fine study by Marucci and coworkers was extended in subsequent work to consider polydomain fluids and higher shear rates [62,63]. The and viscosity predictions obtained are shown in Figure 11.14. Note that not only are all three regimes of well captured by the model, but the hesitation or dip in viscosity is also obtained at the transition from tumbling to wagging behavior. 

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