Micro-turbulence of the stream and its connection with the roughness of the pipeline inner surface

Hydraulics and Engineering Hydrology

This study has been aimed at investigating the problems of a fluid stream flowing in an open chute, which imitates a small-diameter gravity pipeline (up to 150 mm) at low rates of sewage. The works on a specially developed hydraulic bench have enabled determination of the conditions of the flow vortex formation (micro-turbulence) by changing the geometric shape of the internal surface of the pipe by placing artificial protrusions (obstacles) on it, which can help to prevent deposition of suspended particles on the pipeline surface and facilitate their efficient removal. The technique of carrying out hydraulic experiments on the bench has been developed. Several types of artificial obstacles have been studied to investigate their activity in creation of micro-turbulence phenomena on the inner surface of the chute near the frontal surface of streamlined obstacles that can contribute to the stable transport capacity of suspended solids in the flow of a moving fluid. As obstacles, provision has been made of single and grouped bars made of metal and polymeric materials in the form of a parallelepiped and a cylinder, a polyhedron in the form of a prism and screw-nuts, as well as obstacles in the form of an inverted spherical segment, etc. Based on the results of study of the fluid stream flow in an open chute, as well as the location of obstacles, the nature of the vortex formation before and after them was revealed, the optimal geometric dimensions of the obstacles have been got and the areas of disturbance zones at low water flow rates (less than 0.4 m/s) have been determined.