DETERMINATION OF THRESHOLD VALUES OF TURBULENCE ZONE FOR CONDUCTING HYDRAULIC EXPERIMENTS ON PIPELINES WITH TEXTURED INNER SURFACE

Subject: the article is devoted to the study of the processes of vortex formation (microturbulence) in non-pressure pipelines of drainage systems with a corrugated surface during transportation of liquid through them. The results of experiments on the study of microturbulence and carrying capacity of water flow at small fillings and velocities in an open tray are described for the flow past point and linearly elongated obstacles. On the basis of semi-phenomenological theory of turbulence with the use of universal indicator, expressed as a criterion of turbulence, theoretical derivations are presented for determination of zone of conducting subsequent experiments in the corresponding ranges of velocities at different heights of obstacles. The assumption is made that it is necessary to theoretically study the dependence of roughness coefficient on the ratio of obstacle height to pipe diameter in a wide range of fillings. The article presents the results of field experiments to identify the efficiency of pipeline network carrying capacity as a function of the filling value at a certain character of artificial obstacles. Research objectives: theoretical and experimental study of vortex formation processes and carrying capacity of fluid flow as it moves along a non-pressure tray with a textured surface to identify the optimal regime of pipeline operation. Materials and methods: literature sources were analyzed, stands for conducting field experiments were developed. We conducted a series of experiments and set forth theoretical propositions and possibilities for improvement of transporting capacity of the flow as it moves along the gravity pipeline with different textured inner surface. To determine the flow rate, a volumetric method was used, and the degree of turbulence was estimated using photo and movie equipment based on the use of black and white effect. Results: formation of flow microturbulence during placement of single or group obstacles in an open tray was investigated, graphs were constructed and mathematical dependences of the roughness coefficient on the ratio of obstacle height to pipe diameter were obtained for different filling values. A comparison of the values of the roughness coefficient was made for real sewer pipes made of different materials with artificial roughness generated on the experimental setup. The practical absence of discrepancies between artificial and natural roughnesses in the range of self-cleaning rates of water flow and normative fillings is established. Conclusions: studies have shown that the presence of artificial roughness in the form of various types of obstacles on the inner surface of the pipeline (by height, pitch, configuration) noticeably affects the transporting capacity of water flow. This makes it possible to use a textured surface in the form of polymer hoses applied to the inner surface of pipelines during their trenchless renovation to ensure self-cleaning of pipes and improve efficiency of sediments transportation.