A 3D numerical simulation software was developed to calculate the tip-clearance flow of ATS-2

a high-loading transonic compressor

and the results were compared with the experiments.The results of numerical simulation are in accordance with that of experiments.The comparison between the viscous and non-viscous simulations shows that the intensive blockage area is caused by shock-leakage flow interaction.The viscosity weakens the blockage area

both in size and intensity.With the increase of the tip-clearance

the blockage area grows in the radial and axial directions with the total pressure ratio

efficiency and mass flow decreasing.