A comprehensive study on the flow structure of an ensemble-averaged fluidic precessing jet (FPJ) flow is reported. This study is based on the concepts of critical point theory, previous experimental data and validated simulation results. The unsteady Shear Stress Transport turbulence model was adopted for the simulation, which provided well resolved details of the flow. The numerical model successfully reproduced the four main flow features of the FPJ flow. The predicted precession frequency, the total fluctuation energy, the equivalent diameter and the centreline velocity of the phase-averaged FPJ flow were compared against the measured results and found to give reasonable agreement. The streamlines, velocity and vorticity contours in a series of cross-sectional planes are presented. The calculated streamlines at the surfaces of the nozzle and the centre-body are compared with previously deduced surface flow patterns. With these methods, a vortex skeleton with six main vortex cores of the FPJ flow within the nozzle is identified for the first time. This skeleton, which is illustrated diagramatically, is deduced to be responsible for the jet precession.