The unsteady motion of a sphere in a viscoelastic fluid

摘要: The motion of a sphere accelerating from rest along the center line cylindrical tube filled with polyisobutylene (PIB) Boger fluid is examined both experimentally, using digital imaging system, and numerically via Lagrangian finite element method for single multimode Oldroyd models including inertia. Spheres diameter 2.54 cm varying densities are released in radius 5.23 cm. Deborah numbers range 0.4≤De≤11.7 obtained, experimental results show transient velocity overshoots up to 50% before spheres approach their final constant settling velocity. Independent measurements this indicate significant drag increases at high De. numerical calculations compared data, markedly improved agreement obtained simulations.