Numerical simulation of three-dimensional flow field with strong swirl in vortex tube

In order to understand the flow behavior inside the tube distinctly, a three-dimensional physical model of vortex tube is constructed according to flow's movement characteristic and three-dimensional flow field with strong swirl inside the tube is simulated by the usage of practical Realizable k-ε turbulent numerical model. From the simulated velocity field, the distributions of tangential, axial and radial velocity as well as the recirculating flow patterns are investigated. In addition, the strategy of non-dimensional comparisons between numerical results and previous experimental data is applied to validate numerical data indirectly. Satisfactory agreements are observed between them. The numerical results show that flow motion inside the vortex tube presents extraordinary complicated behavior. The swirling flow inside the vortex tube consists of two regions with an outer region of quasi-free vortex flow surrounding an inner region of quasi-forced vortex flow. From view of the composition of axial and swirl motion, the flow inside the tube consists of periphery flow and inner flow. With radial and swirl motion considered, the helical flow exits inside the vortex tube. There is also a recirculating flow inside the tube when the composite motion of radial and axial movement are analyzed. The peripheral and inner flows exchange heat and mass through the enveloping surface of zero axial velocity in the form of recirculating flow because the enveloping surface of zero axial velocity is the interface between peripheral and inner flow.