Computation of laminar and turbulent flow in 90 deg square duct and pipe bends using the Navier-Stokes equations

Three dimensional laminar and turbulent flow within 90-degree bends of strong curvature and both circular and square cross section are studied by numerical solution of the compressible Reynolds-averaged Navier-Stokes equations. The governing equations are expressed in a body-fitted orthogonal coordinate system and then solved using a consistently-split linearized block implicit (LBI) algorithm. The turbulence model and computational mesh provides for resolution of the viscous sublayer and employs an isotropic eddy viscosity based on solution of the turbulence kinetic energy equation and a specified length scale. Six different flow cases are considered, and the developing flow structure and its dependence on geometric and flow parameters is examined. The computed results are compared with available experimental measurements, and the sequence of comparisons helps to establish the accuracy with which these flows can be predicted by the present method using moderately coarse grids (approx = 10,000 points).