Identification of the characteristics of incompressible fluid unsteady turbulent flow in round pipes

The object of the study is the unsteady turbulent flow of an incompressible fluid. The main problem of this task is to take into account the shear stresses on the basis of which the boundary value problem is compiled. It is well known that when incompressible fluid experiences unsteady turbulent flow the fluid particles moving in parallel, acquire velocity perpendicular to the direction of flow, which causes turbulent shear stresses to develop between the fluid layers. In order to study the patterns of changes in hydrodynamic parameters in turbulent flow, the calculation of turbulent tangential stresses was performed using the formula proposed by Prandtl, on the basis of which a boundary value problem was formulated and a methodology for solving the problem was developed. The regularities of instantaneous velocity changes in non-stationary turbulent motion were obtained, which make it possible to obtain calculation formulas for individual terms of the momentum, kinetic energy coefficients, tangential stresses, and pressure losses. Based on the general solutions to the problem, the patterns of changes in the hydrodynamic parameters of the accelerating motion of a viscous fluid at rest under the influence of a constant pressure gradient were obtained. Relying on the results of performed computerized experimental studies graphs of the distribution of instantaneous and average velocity, tangential stresses, momentum, and kinetic energy coefficients depending on time and point coordinates have been plotted. The results of the performed studies enable calculation of hydrodynamic parameters of unsteady turbulent flows, which are necessary for engineering calculations