The paper is devoted to the numerical study of the effect of air injection into the hydrodynamic vortex chamber at the flow characteristics with precessing vortex core. The calculation results are in good agreement with the experimental data obtained at the Institute of Thermophysics SB RAS. Obtained numerical data confirm the effect of the decrease of the vortex precession frequency at low amount of air and further smooth growth of the precession frequency with increasing gas flow rate in the stream.