  A detailed numerical study on the phenomenon of Shock Wave focusing in air is
carried out. The focusing phenomenon is achieved with the help of a shock tube
and a converging section attached to it. The planar shock generated inside the
shock tube is converted to spherical shock with the help of the converging
section and is focused to a point. High-temperature effects like
temperature-dependent Cp variation and chemical reactions corresponding to
dissociated air are included in the simulation. The chemical reactions
including the dissociation, recombination and ionization of nine species of air
including three ions (N2, O2, N, O, NO, Ar, NO+, O+ and Ar+) are monitored
throughout the simulation. The effect of driven section filling conditions such
as initial pressure and temperature on focusing parameters is studied. The
variation in the initial fill temperature is found to affect the flow
properties much more as compared to the change in initial fill pressure, while
maintaining the same shock strength. The effect of incident shock strength on
shock wave focusing is also investigated. It is observed that as the strength
of the shock increases, the conditions like temperature and pressure at the
focusing point increases and thereby increasing the reaction rate of all the
reactions.
