Evolution of shock waves and the primary vortex loop discharged from a square cross-sectional tube

In this paper, a numerical and experimental investigation of the evolution of a transmitting shuck wave and its associated primary vortex loop, which are discharged from the open end of a square cross-sectional tube, is descr ibed. The experiments were conducted in the square tube connected to a diap hragmless shock tube and the flowfield was visualized from the axial direct ion with diffusive holographic interferometry. The numerical simulations we re carried out by solving the three-dimensional Euler equations with a disp ersion-controlled scheme. The numerical results were displayed in the form of interferograms to compare them with experimental interferograms. Good ag reement between the numerical and experimental results was obtained. More d etailed numerical calculations were carried out, from which the three-dimen sional transition of the shock wave configuration from an initial planar to a spherical shape and the development of the primary vortex loop from a sq uare shaped to a three-dimensional structure were clearly observed and inte rpreted.