FORCED-CONVECTION FROM A SURFACE COVERED WITH FLEXIBLE FIBERS

The heat transfer, friction and mechanical (elastic) interaction betwe en an external laminar flow and a solid surface covered by a layer of fibers is investigated numerically. The flow is initially perpendicula r to the surface, and the fibers can bend. The study has two parts. In the first part it is assumed that the fibers are inflexible. It is sh own that the effect of the fiber layer on the overall heat transfer ca n be correlated in terms of the fraction of the external flow that pen etrates into the fiber layer. The second part focuses on the effect of fiber bending, which is described by a new dimensionless group: the s tiffness number S = EI/(rho U2(INF)L4). It is shown that the wall heat transfer, friction and fiber layer flow fraction exhibit a sudden dec rease when S drops below a critical value, S(c). The critical stiffnes s number can be correlated as S(c) = C(H/L)5(D/H)2/(1-phi), where C is a constant of order 0.4, H and D are the fiber length and diameter, L is the half-length of the solid wall, and phi is the porosity of the fiber layer.