The flow in the neighborhood of a rotating disk is of great practical importance particularly in connexion with rotary machines. It becomes turbulent at larger Reynolds numbers, R > 3 x 105, in the same way as the flow about a plate. In this article we consider o motion of incompressible fluid that is always turbulent in circular direction (Reynolds number based on circular velocity R > 3 x 105) and is of both of kinds in radial direction, i e. laminar (Reynolds number based on radial velocity Rr < 3 x 105) and turbulent ( Rr > 3 x 105). The equations of analyticity of functions of spatial complex variable (shortly, the equations of tunnel mathematics) affords a possibility to seek the solutions of steady Navier-Stokes equation in view of elementary functions. All vector fields, including those obeying the Navier-Stokes equation, satisfy to the equations of tunnel mathematics. The Navier-Stokes equations themselves are afterwards applied for verification of obtained solutions and calculation the pressure. Obtained formulae for pressure allow to visualize the presence of the boundary layer and estimate its thickness for laminar and turbulent flows. We use the Prandtl`s concept of considering of fluids with small viscosities, i. e. we suppose that Reynolds number is enough large and the viscosity has in important effect on the motion of fluid only in a very small region near the disk (boundary layer). We also suppose that the fluid and the disk had at beginning the same temperatures and the energy dissipation occurs only by means internal friction.