Electrostatic effects on resuspension of rigid-link fibers in turbulent flows

Fiber resuspension from smooth surfaces in a turbulent boundary layer flow including electrostatic effects is studied. A rigid-link fiber model which is composed of five rigidly attached ellipsoids is considered. The fiber co ntacts with the wall are modeled as spherical end joints. For an average of the Boltzmann charge distribution, as well as the saturation condition, th e Coulomb, the image, the dielectrophoretic, and the polarization forces ac ting on the fiber in the presence of an imposed electric field are evaluate d. The cases that charges are concentrated on the tip spherical joints, and when they are uniformly distributed along the ellipsoidal links are analyz ed. The interfacial forces at the spherical contact points are determined b y the Johnson-Kendall-Roberts (JKR) adhesion model. The theories of rolling and sliding detachment are used to study the onset of removal of fibers fr om surfaces in an air flow field. The hydrodynamic forces and torques actin g on the fiber attached to a wall, along with the adhesion forces of contac t nodes, are used in the model development. The minimum shear velocities ne eded to detach fibers of different sizes, orientations, and thickness from plane surfaces in the presence of an applied electric field are evaluated a nd discussed. It is shown, for saturation charge condition, the electric fi eld strength significantly affects the critical velocity for removal of fib ers from surfaces. (C) 2000 Elsevier Science B.V. All rights reserved.