Femtosecond laser electronic excitation tagging for velocity measurement in supersonic jet

The velocity profile of supersonic jet measured by femtosecond laser electronic excitation tagging (FLEET) is discussed in order to study the applicability of the FLEET in the supersonic flow field. A femtosecond laser is used to excite nitrogen molecules as tracer molecules in the flow field. The tracer molecules move with the flow field and emit fluorescence, and the velocity is calculated by the ratio of the displacement of fluorescence emission to a certain time. The velocity field of an axisymmetric supersonic free jet is studied. The axial velocity and one-dimensional velocity distribution at different axial heights are obtained. On this basis, the two-dimensional axial velocity profile of the supersonic jet is reconstructed, and the velocity measurement error is given.