The pair annihilation of straight line defects with strength $\pm 1/2$ in bulk nematic systems is studied numerically, considering a full coupling of orientational degrees of freedom and hydrodynamics. This work is based on the generalization of the Ericksen-Leslie theory to the tensor order parameter as proposed by Qian and Sheng [T. Qian and P. Sheng, Phys. Rev. E 58, 7475 (1998)]. The approach is particularly suited for the late stages of the annihilation process. It is confirmed that the $+1/2\mathrm{}$ disclination line moves considerably faster than the $-1/2$ one (e.g., twice as fast) due to the hydrodynamic flow. Symmetries of the important stress tensor terms upon inverting the sign of the winding number and performing a homogeneous in-plane rotation of the $\mathsf{Q}$-tensor eigensystem are discussed. The stress tensor terms that dominantly contribute to the advective flow and to the flow asymmetry are identified.

• Received 24 April 2002

DOI:https://doi.org/10.1103/PhysRevE.66.021712