UNSTEADY INTERACTION OF SHOCK WAVE DIFFRACTING AROUND A CIRCULAR CYLINDER IN AIR

The reflection and diffraction of a planar shock wave around a circular cylinder are a typical problem ofthe complex nonlinear shock wave phenomena in literature.It has long been studied experimentally,analytically as wellas numerically.Takayama in 1987 obtained clear experimental pictures ofisopycnics in shock tube under the condi-tion that the impinging shock wave propagates as far as 3 diameters away from the cylinder.To know more complete-ly the whole unsteady process,it is desirable to get experimental results in a region which is more than 10 diametersaway from the cylinder.This is what has been done in this paper by using the pulsed laser holographic interferometryfor several shock Mach numbers of the impinging shock. Results for several moments are shown,giving more know-ledge about the whole unsteady flow field.This is useful for a reliable and complete understanding of the changingforce acting on the cylinder,and provides interesting data to check the performance of many recently developed highresolution numerical methods for unsteady shock wave calculation.