Velocity-distribution in pressurized pipe flow using CFD: Accuracy and mesh analysis

Abstract The aim of the current paper is the development and application of a systematic and comprehensive approach for obtaining the most efficient meshes, described in terms of dimensionless parameters, for modelling pressurized water flows in pipes using Computational Fluid Dynamics (CFD). This analysis is carried out for the combination of three dimensionless mesh parameters: λ a , the dimensionless mesh size in the axial direction expressed in terms of number of diameters; λ c , the dimensionless mesh size in the circumferential direction expressed in terms of the pipe perimeter; and λ r , the ratio between the first layer thickness (FLT) and the thickness of the viscous sublayer for a specific turbulent flow. A four-step systematic approach has been used to obtained the most efficient meshes: (i) the mesh is generated in a meshing software using the 3-D fluid domain which is defined in a computer-aided design software; (ii) steady state fluid flow is simulated by using the CFD until the convergence criteria is met; (iii) the accuracy of the numerical results is evaluated by comparing the computed velocity profiles with exact or semi-empirical solutions; and (iv) the previous three steps are repeated for different combinations of mesh parameters and for two flows (laminar and turbulent) and the most efficient meshes are obtained by the compromise between the maximum accuracy and the minimum computational effort. The use of the most efficient meshes in other pipe flows is discussed.