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The article considers an analytical approach to the relative characteristic parameters determining in the initial hydrodynamically unstabilized sections. Using the momentum equation, analytical equations are obtained for the dynamic boundary layer thickness determining. Laminar and turbulent flow regimes were considered. It is noted that the initial sections are characteristic for the flow around such surfaces as: blades of turbines and centrifugal pumps, nozzle elements, cavities between the casing and the rotor of the turbopump unit. In the flowing parts of liquid propellant rocket engines turbopump units, relatively short spatial channels, characterized by the presence of non-merged dynamic and temperature boundary layers prevail. The initial section significantly affects the flow regime, length loss and heat exchange processes. The analytical dependencies obtained cover a wide range of flow regimes and are in good agreement with the experimental data of other authors. An approach is given to determine the hydrodynamic parameters for the initial sections that affect the overall flow pattern in complex spatial channels with different degrees of curvature in the presence of a pressure gradient.

Calculation of initial dynamically unstabilized sections in the elements of liquid rocket engines turbopump units