Two dislocations of opposite signs interacting via their elastic fields are consider. They move in parallel
slip planes in a PSB channel. Initially they are kept apart in straight screw positions. The walls of the
channel are simulated as the elastic eld of rigid edge dipoles. The dislocations are modeled as plane
curves. A special computer program based on the owing volume method and the method of lines is
employed. Assuming an over-damped motion, we consider a linear relationship between the force acting
on the dislocation and the velocity magnitude. The computation simulates the shape changes of the
dislocations during their passing. The passing stress for various distances between the slip planes and for
various channel width is compared with the bowing stress. The stress and strain controlled regimes of
the dislocation motion are analyzed.