In this work we present a detailed study of supersonic flow that originates behind the shock wave after its discharge from the shock tube channel. In our experiments initially flat shock waves with Mach numbers 1.3-1.9 propagated through the low-pressure chamber of the shock tube with a rectangular cross-section of 24×48 mm2, and then diffracted on its open end. For experimental visualization of the subsequent flow we employed PIV (particle image velocimetry) and BOS (background oriented schlieren) techniques. This set-up allowed capturing main structural elements of the flow, including the diffracted shock wave, the contact surface, the vortex loop and the jet flow. The flow was also investigated by means of CFD, the code based on solving the non-stationary Navier-Stokes system of equations. The numerical modeling shows good agreement with experimental data.