In the past, much attention was given to the diffraction of a shock wave over various geometries; extensively explored through experimentation and simulation, and by many others. Some aspects from a study of expansion wave diffraction over a convex 90° degree corner, in absence of rig dependent effects resulting from wall reflections, are discussed. Two independent parameters were considered for this study to investigate their effect on the evolution of the flow field at the 90° corner upon expansion wave diffraction. These parameters were: 1) the diaphragm pressure ratio (P41) used to generate a one-dimensional expansion wave and 2) the distance between the diaphragm and the diffraction corner (D), to vary the expansion waves width prior to diffraction. A variety of P41 and D values were considered between experiment and simulation for subsonic flow through the expansion wave, which occurs for P41 ＜ 10.4 for air (γ= 1.4) at approximate atmospheric conditions (P_(atm) = 83400 kPa and T_(atm) = 288 K). Upon diaphragm rupture, the expansion wave propagates upstream into the high pressure region (driver) therefore a viewing window and test-piece were required in this region which led to the development of an unusual shock tube. In typical shock diffraction studies, these elements are located in the low pressure region (driven). The present study was considered novel as no information was found in the literature similar to the diffraction of an expansion wave over large angles except for a computational study by which considered expansion wave diffraction over a rigid boundary slightly inclined to the flow direction.
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