Desempenho E Precisão De Equações Explícitas Do Coeficiente De Perda De Carga Em Regime De Fluxo Turbulento

Abstract

A equação de Colebrook-White é amplamente utilizada para dimensionamento do coeficiente de perda de carga (f) de Darcy-Weisbach, sendo estipulada como padrão. Por ser uma formulação implícita, com soluções iterativas, diversas equações explícitas foram desenvolvidas para calcular o "f". O objetivo desse estudo foi avaliar o desempenho dessas aproximações, através do índice de desempenho (Id) e a precisão, através da média do erro relativo (MER), das equações explícitas em relação a implícita padrão, variando-se o intervalo do número de Reynolds de 4x10³ ≤ Re ≤ 10 8 e da rugosidade relativa de 10-6 ≤ Ɛ/D ≤ 5x10-2. As equações de Chen (3), Sonnad e Goudar (8), Buzzelli (9), Vantankhah e Kouchakzadeh (10), Fang et al. (11) e Offor e Alabi (13) apresentaram elevado Id, classificando-as como "Excelente" e elevada precisão quando comparadas com a aproximação de Colebrook

Simplified Scobey formula for determining head loss in pressurized pipes

“…Table 5 shows the Willmott's index of agreement (d), correlation coefficient (r) and performance index (P), to compare the results obtained by the Darcy-Weisbach equation (reference values) and by the simplified Scobey equation (estimated values), for different diameters and internal wall roughness of the pipes. The comparison between the values of head loss by the simplified equation and the Universal equation (Darcy-Weisbach), for pipes with the respective values of diameter and roughness (Table 5), showed high agreement, high degree of correlation and Performance Index considered as "Excellent" (PIMENTA et al, 2018).…”

“…Continuous head loss in irrigation systems occurs due to friction between the particles of the fluid itself, kinematic viscosity, and also the friction of the liquid with the internal wall of the pipe (MIRANDA, 2016). It can be estimated through several equations (PIMENTA et al, 2018), allowing the designer to choose which head loss equation to use, provided that the situation meets the assumptions of use. Inadequate choice can lead to significant errors in the definition of pipe diameter and, consequently, throughout the hydraulic structure of the project (SOUSA, 2018).…”

“…Simplified Scobey formula for determining head loss in pressurized pipes Revista Brasileira de Agricultura Irrigada v.16, p.31-41, 2022 Source:Pimenta et al (2018) …”

Implementation of the Green-Ampt Infiltration Model: Comparative between different numerical solutions

“…The Relative Percent Error, also called Relative Error, is a simple metric used to evaluate the error between values closest to reality, in this case the values measured in the field, with the values obtained by the numerical model [3,4,6,27,32]. The RPE varies between 0 and 100% and its tolerance usually varies according to the characteristics of the data used.…”