IMAGING VELOCITY PROFILES - FLOW THROUGH AN ABRUPT CONTRACTION AND EXPANSION

Dynamic nuclear magnetic resonance (NMR) microscopy has been used to study the laminar flow of water through cylindrical tubes in the vicinity of both an abrupt expansion and an abrupt contraction. Radial profiles of the velocity have been obtained, at a spatial resolution on the order of 20-mu-m, for the velocity components in the axial and transverse directions, both at the junction and at different axial displacements on either side of the junction. The data have been compared with solutions of the Navier-Stokes equations obtained by finite difference numerical methods using a Macintosh personal computer. Excellent agreement is apparent without the need for any adjustable parameters, the numerical solutions depending only on the Reynolds number determined from inlet flow conditions. This study demonstrates the usefulness of dynamic NMR microscopy for the study of the flow of Newtonian fluids in complex geometries. The method can also be applied to the flow of non-Newtonian fluids.