Profiles of the flow velocity v(r) in the observer reference frame (left) and u(x) in the shock reference frame (right) for the three models of SNRs. Upper row: Three SNe models at 500 yr. Lower row: SNIa model at the ages 20, 200, and 1000 yr. On the plots to the left, the explosion centre is at r = 0 with the zero velocity v there. On the plots to the right, the horizontal axes display x = 1 − r/R. Therefore, negative values correspond to the upstream region, whereas positive values correspond to the downstream region. The centre of the explosion on the right-hand side plots is at x = 1, and the velocity u at this point is equal to the upstream velocity u₁. We conducted the numerical simulations for the unmodified shocks, and therefore u is spatially constant upstream. The dashed line represents the velocity profile from the Sedov (1959) solution.