The radius r_sh of the shell as a function of time, calculations of the RING code, the evolution without the external gravitational potential. Black and green lines correspond to the evolution in the homogeneous medium, blue and red lines to the evolution in the Gaussian disc with the thickness of 200 pc. Black line is the basic model, green lines (dashed and dotted, respectively) correspond to models with 10x higher and smaller energy inputs with adequately higher and smaller densities (L/n are the same for all models). Blue lines show the radius of the shell in the plane (solid) and the z-extent (dash-dotted) for the basic model. Red and orange lines again correspond to models with higher and smaller energy inputs and densities, respectively.