Ambiguity of solution for triple configurations of stationary shocks with negative reflection angle

The theory of interaction of stationary gasodynamic discontinuities points to existence of Mach shock reflection with negative slope angle of the reflected shock. It forms in steady gas flows with large Mach numbers and small adiabatic index. Feasibility of such (“negative”) triple-shock configurations, their stability and unambiguity of corresponding solutions seem traditionally doubtful. In the present study, conditions of existence and solution's unambiguity regarding “negative” configurations are analyzed. In addition, the possibilities of having other shock-wave structures, which can appear at the same parameters of supersonic steady flow and incident shock, are determined analytically. •Triple-shock structures with negative reflected shock slope angle are formally possible.•They appear at Mach reflection in high supersonic gas flows having small adiabatic index.•The feasibility and stability of observing such reflections in steady flows looks doubtful.•Solutions corresponding to Mach reflection with negative slope angle are ambiguous.•Regions of solution ambiguity and types of “alternatives” are found analytically.