High Pressure Torsion (HPT) is historically the first and is currently most common process of the severe plastic deformation (SPD). HPT is used for producing nanocrystalline structures in metals and alloys, as well as for cold welding of powders. The result of the HPT treatment is determined by the flow kinematics and the stress state of a material under deformation. P. Bridgman proposed a simple model for the initial assessment of shear strain in the sample during HPT. A number of recent investigations show that the true plastic flow during HPT can differ significantly from the simple model. We present in our report results of the FEM investigation of different types of flow during HPT. We propose a hypothesis that the vortex formation during the SPD process is caused by the local blocking of simple shear in a material under deformation.