Abstract
This paper outlines a method used to generate a three dimensional, periodic, annular mesh for a large diameter, low solidity, axial flow fan. The meshing methodology generates a 2-D airfoil mesh at specified radial stations along the blade span. The 2-D airfoil meshes are stacked and wrapped to create the mesh of the axial flow fan. The 2-D airfoil meshing methodology inserts a blunt trailing edge to more closely match a physical fan blade where the trailing edge is not infinitely thin. The airfoil meshing algorithm uses airfoil characterisation, using Bezier spline regions, and extrusion to create a highly orthogonal near-wall mesh. A versatile spline relaxation method is developed to relax the mesh from the near-wall region to the far field geometry. The meshing tool is used to conduct an incompressible, steady state, Computational Fluid Dynamics (CFD) study of the B2a-fan using OpenFOAM. Correction factors are used to correct for the absence of the tip gap in the domain modelling. The corrected pressure characteristic was most accurate at the design point volume flow rate, attaining a deviation of 2.5% with a Grid Convergence Index (GCI) of 3.6%. The static efficiency was predicted with a deviation of 5% at the design point flow rate. The deviation in efficiency is caused by an increased static pressure rise due to domain simplifications leading to a lower blade torque. The blade swirl velocity showed good correlation with reference data with small deviations toward the blade tip.
