APPLYING HYPOTHESIS OF SELF-SIMILARITY FOR FLOW-RESISTANCE LAW OF SMALL-DIAMETER PLASTIC PIPES

In this paper the writer reports the results of an investigation carri ed out to test the applicability of the self-similarity hypothesis for determining the flow-resistance law in small-diameter plastic pipes. The incomplete self-similarity (ISS) hypothesis is applied for establi shing both the flow-resistance law and the velocity distribution. The analysis shows that the head loss per unit length can be accurately es timated using a theoretical approach based on the ISS hypothesis for t he velocity profile in a circular smooth pipe. A new relationship betw een the Gamma coefficient of the power-velocity profile and the flow R eynolds number, based on previous measurements carried out in plastic polyethylene (PE) pipes with nominal diameter equal to 16, 20, and 25 mm and for flow Reynolds numbers ranging from 3,037 to 36,112, is also established.