Experimental Study of Flow Crisis and Flow Structure in Ranque–Hilsch Vortex Tube

The work investigates the relationship between the energy separation in a Ranque–Hilsch tube and flow crisis manifestation in a translational swirling flow. The laser Doppler anemometry was used for the measurement of the transverse profiles of circumferential and longitudinal velocities in the mid-section along the entire length of the working channel in a vortex tube with a square cross-section. Analysis of the experimental data revealed signs of a series of hydraulic jumps that realize structural transitions from supercritical flow regimes of a near-wall swirl flow with longitudinal velocity exceeding the critical one to subcritical regimes, the longitudinal velocity in which is less than the critical one. The identified features suggest that there may be an increase in temperature in the near-wall flow due to the conversion of excess kinetic energy released during hydraulic jumps into heat, while conserving the momentum flow. A number of phenomena associated with the Ranque effect are discussed within the concept of crisis of a translational swirling flow and the more general concept of vortex breakdown.