The purpose of the research was to consider solid particles moving in part-flow hydrodynamic filters with a rotating perforated baffle and simulate liquid flows in the working zones of filters. The paper introduces the results of the study. Within the research, we determined the averaged values of the tangential, radial and axial components of the movement velocitis depending on the radius of the device, confirmed the validity of using a cylindrical filter wall, and established the presence of low-pressure and pressure modes of liquid cleaning in the filters. We revealed that in the low-pressure mode solid particles move in a typical for centrifuges way, and in the pressure mode the particles movement is characteristic of that of small-sized hydrocyclones. The study introduces a technique for obtaining averaged deterministic characteristics that make up the liquid flow velocity in height, azimuth and radius in the working zones of a hydrodynamic filter and estimates the averaged components of the liquid velocity. Compared to the tangential component, the axial velocity component is one order of magnitude smaller, and the radial component, two orders of magnitude smaller. Findings of the research show that the designs of such hydrodynamic filters implement a four-stage liquid cleaning system and emphasize that in transport equations not only deterministic components but also random components of ongoing processes should be taken into account for particles smaller than 40 μm