The hydraulic resistance paradox in rapid narrow pipe waterflow

Richard Dvorský,Jiří Bednář,Ladislav Svoboda

doi:10.1038/s41598-020-78109-4

Richard Dvorský, Jiří Bednář + Show 1 more

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https://doi.org/10.1038/s41598-020-78109-4

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Journal: Scientific Reports	Publication Date: Dec 1, 2020
License type: open-access

Affiliation: Technical University of Ostrava

Abstract

In this work we present experimental results of cross-sectional speed of water flow in narrow cylindrical metal tubes at high pressure gradients up to 1.1 GPacdotm−1. The measurement draws attention to the paradoxical behaviour of flowing water in internal diameters less than 250 upmum. At constant pressure gradient, its cross-section speed decreases with decreasing diameter in accordance with the classical hydrodynamic prediction for turbulent flow in rough cylindrical tube. However for very low diameters below 250 upmum, the cross-section speed rises again and reaches almost the maximum theoretical value of the outflow speed for the appropriate pressure without energy loss caused by contraction or hydraulic friction. Our contribution describes mainly experimental character of the new phenomenon and its motivation is to promptly provide the material for further study to the professional public.

Highlights

In this work we present experimental results of cross-sectional speed of water flow in narrow cylindrical metal tubes at high pressure gradients up to 1.1 GPa·m−1
In our previous w ork[3], we observed a significant deviation from the predictions of classical hydrodynamics for turbulent flow during technical use of extreme hydraulic impacts in fast moving water (v > approx. 50 ms−1) in cylindrical metallic pipe
Based on it we conducted a new experiment, which systematically mapped the dependence of the cross-sectional speed of water flow on the inside diameter d of the tube in the region (0.13 ≤ d ≤ 0.50) mm

Summary

Introduction

In this work we present experimental results of cross-sectional speed of water flow in narrow cylindrical metal tubes at high pressure gradients up to 1.1 GPa·m−1. Based on it we conducted a new experiment, which systematically mapped the dependence of the cross-sectional speed of water flow on the inside diameter d of the tube in the region (0.13 ≤ d ≤ 0.50) mm.

Results

Conclusion