Effect of Eccentricity on Pipe Boundary Layer Growth for Flows in Annulus

Laminar vortex rings are produced in the laboratories using a piston/cylinder arrangement. The dynamics of these rings are being extensively studied over the last couple of decades. Research has shown that the most important flow feature which describes the generation and propagation of these rings is the boundary layer growth. The present study focuses on the effect of eccentricity on the pipe boundary layer growth for flows in annulus. Two geometries with different eccentricities are modeled and numerically solved using commercial CFD package. The results are then compared with a concentric geometry. The results indicate toward a faster flow development in eccentric annulus. As vortex rings are generated when the boundary layer is still developing, eccentricity adversely effects the production of laminar vortex rings. This faster flow development hints towards a faster transition of Navier-Stokes equation’s solution from Rayleigh to Blasius.