Irregular wedge shock wave reflection (2400m/s). On the right is a shaded photograph of the process, on the left - the distribution of the first density derivative obtained by means of the GDT package

     Wedge shock wave diffraction is quite a many-sided physical phenomenon. Effects of regular and irregular (Machovsky) wedge reflection, formation of two triple points, interaction of a boundary layer and a complex non-stationary system of gas-dynamic breaks - these are just a few of the many interesting phenomena, analysis of which is of great importance for practical work as well as for the science of mechanics of continua.
     This interesting problem was solved to verify the GDT package. A good coincidence of computational results and experimental results is obvious.

Angle shock wave diffraction. The figure on the left represents the distribution of the second density derivative obtained by means of GDT, on the right - a shaded photograph (Van Dyke 1982)

     The figure presents comparison of the second density derivative distribution obtained by means of GDT and a shaded photograph given the strong right angle shock wave diffraction (M=7). This photograph shows the main attributes of the phenomenon - deceleration wave, vortex at its lower edge, the first and last characteristics of the discharge fan, contact area and glide line. The package displays properly not only spatial arrangement and shape of these formations, but also their strength.

Computation results (on the left) and a schlieren photography (Ritzerfeld E. et al., 1991) of the angle blast wave diffraction process (on the right)

     The figure represents simulation of a similar process with a smaller degree of strength of a diffracting shock wave. With the wave Mach number of 1.5, as in this experiment, no deceleration wave is generated, and the flow forms a typical spiral structure.

Diagrammatic representation of the initial and the diffracted shock waves in the process of a 3D edge diffraction

Semi-transparent isosurfaces of pressure distribution

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    The above described problem has been also solved in a 3D statement. The results are represented on the figure.

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     The figure represents the computation results for the interaction of shock waves with obstacles. This class of flows is a relatively easy one to explore with the help of experimental optic methods and is traditionally considered to be a reliable method for testing the efficiency of the computational approaches. Here is the comparison of the shaded photograph (on the right) and the numerical simulation results for the process of the propagation of a blast wave through a series of obstructions. Despite mipmaps and the presence of high-gradient areas, vortices and other non-linear formations in the flow region, the program ensures congruence of the fracture layout, which testifies to the correct specification of the space distribution for all gas-dynamic parameters and the laws of their dynamic development. Shaded photographs present information not about the density distribution itself but about fracture layout of its distribution, and, thus, it makes sense to compare experimentally obtained data and calculations of absolute density derivatives.

    Propagation of a shock wave through a flat curved channel. The right side of the figure represents the interferogram, the left side - the computation results obtained with the help of the GDT package. Density isolines are represented by means of the color corresponding to the value of the horizontal velocity component. The red color corresponds to the zero value, the violet color - to the maximum value.