Crossover behaviour during gelation in shear flow

Gelation in shear flow is studied using a two-dimensional, square lattice cluster-cluster aggregation model. The model is similar to that proposed by Santra and Herrmann (1995); however, the rotation of the clusters is to be taken into account. It was found that this modification of the model alters the behaviour of the aggregating system: under a certain length a(cr), the aggregation is isotropic and above a(cr) it becomes anisotropic. It is shown numerically and theoretically that the crossover length a(cr) depends on the concentration as a(cr) similar to c(1/(D-d)), where d is the dimension of the space and D is the fractal dimension of the clusters.