Дослідження коефіцієнта гідравлічного тертя під час руху рідини в напірному трубопроводі

Abstract

UDC 631.3:621.1

INVESTIGATION OF FRICTION FACTOR IN THE HYDRAULIC FLUID FLOW in the pressure pipe

V. Vasilenkov, , A. Nazemtsev

In engineering practice the motion of the fluid in the pipes solving many problems comes down to finding addiction, which determines the change ща speed and pressure along the length of the stream.

Assay head loss is one of the main tasks of hydrodynamics and is an urgent task.

The purpose of the work. Research coefficient of friction when moving hydraulic fluid in the pressure pipe.

Materials and methods of research. Movement of fluid in the pressure pipe. Figure Nikuradze.

Results. Loss of pressure along the length of the pipeline conditioned by the work of friction. When moving the fluid are evenly distributed along the length of the pipeline section and constant increases in proportion to the length of the pipe.

the definition of physical factors affecting its value, and establish methods of determining it was for a long time the subject of extensive theoretical and experimental research.

Modern formulas for determining the λ provide its dependence in general roughness of the pipe walls and the Reynolds number.

To study the factors that affect the value of the coefficient λ, and the development of the theory of the fluid in the pipes, have essential work Prandtl, Karman, Nikuradze and others.

Nikuradze analyzing graphs can capture the region (1, 2, 3, 4), within each of which the dependence of λ on the Reynolds number and relative roughness equivalent     held its special character.

1 - the area between the straight line MN and the origin - region of laminar motion mode (Re <2320). Λ factor in this area is caused by the viscosity of fluid and is independent of the roughness of the pipe walls.

The boundary of this area is the Re = 2320.

2 - the area between the lines MN and KL - region hydraulically smooth pipes. The flow of liquid is already in motion under turbulent regime (Re> 2320), however, near the walls in a viscous layer remains fixed laminar film covering performances roughness rough walls, and the flow moves as if on a hydraulically smooth pipe (the liquid fixed layer). Realized this flow at the Reynolds number, which is within 4000 < Rе < 10.

3 - the area between the lines AB and KL - a transitional area. This region with increasing velocity laminar film thickness on stintsi tube decreases, partially opening speeches roughness. These public appearances and observed disruptions flow generated vortex core. In this flow head loss as stipulated roughness of pipe walls and by the viscosity of the liquid, is the Reynolds number.

4 - area right of the line AB - the area quadratic resistance. The flow rate of the liquid reaches the value at which the pressure loss does not depend on the Reynolds number, but only due to flow friction forces against the pipe walls. Defining parameter here is equivalent to the relative roughness. Wall laminar film fully destroyed, viscosity layer disappears and the flow washed all appearances roughness throughout their height. They formed small scale vortex field, which spreads throughout the flow.

Conclusions

The resulting parameters that affect the coefficient λ in various regions of the fluid, determining factor λ, the equivalent roughness k_E in the laboratory.