The idea of applying dimensional analysis to solve some problems of hydrodynamics associated with convective transport of a liquid medium is presented. In particular, it is the base for deriving equations of continuity, thermal conductivity, diffusion, motion of the ideal (Euler) and viscous fluid (Navier-Stokes), with some supplements from the field of electrohydrodynamics. In addition, the problem of the presence of two forces of viscous friction is solved, those of sliding and deformation (in the case of "compression-stretching" in a compressible fluid). Formulas for these forces are derived.