A new supersonic ejector nozzle with clamshell doors is proposed as a noise suppression jet engine exhaust system. A design table driven, parametric nozzle geometry was designed. The experimental and numerical studies of its flow field were carried out. Cases with and without clamshells were considered and their mean velocity flow fields were compared. The experimental investigation involved the testing of the nozzle in a wind tunnel and the measurements were taken using a seven-hole probe, mounted on an automated 2-axis traverse instrument. Various flow visualization techniques such as the fluorescent oil flow, surface sediment traces, smoke wand and surface tuft were also implemented to capture the flow physics on the inside of the clamshells. Numerical simulations were performed using the commercially available finite volume-based computational fluid dynamic code FLUENT. The computational results are in good agreement with the experimental measurements at different axial locations downstream of the nozzle throat. A zone of flow separation and recirculation is captured at the inner surface of the clamshells in both the experimental investigation and numerical computation.