A Study on a Semi-empirical Model for the Local Loss Coefficient of Small Angle Contraction Pipes

The design of contraction pipes for efficient fluid transport and spraying applications requires a deep understanding of fluid dynamics and resistance characteristics. This study utilizes the infinitesimal element method to analyze the fluid motion within the cross-section of a circular contraction pipe and confirms that the wall shear stress is a function of the total pressure gradient and pipe diameter, in accordance with Stokes’ formula. Numerical simulations are employed to investigate the velocity distribution and transverse pressure loss pattern across the cross-section of the pipe. By making reasonable assumptions and conducting data fitting, we present a semi-empirical model that predicts pressure loss and local loss coefficients in small contraction pipes. This model is shown to be simpler, more accurate, and broadly applicable, compared with existing models. This study provides practical guidance for the design of contraction pipes and enhancement of the accuracy of pressure loss calculations, which are crucial for optimizing fluid transport systems.