Analysis of turbulent flow in a channel roughened by two-dimensional ribs: effect of first rib width
B. Omari, A. Mataoui, A. Salem
University of Science and Technology Houari Boumediene, Algiers, Algeria
Keywords: выступ, ребристая поверхность, коэффициент трения Дарси, коэффициент сопротивления давления, силы сопротивления, турбулентность, forward facing step, ribbed surface, Darcy friction factor, pressure drag coefficient, drag force, turbulence
Abstract
This work investigates the turbulent flow in a channel roughened by seven ribs of rectangular cross section disposed transversely. The flow configurations of identical ribs from the first one generate a large eddy spreading along the top of the two first ribs, trapping the flow of the first cavity. The widening of the first rib may solve this problem. Therefore, this flow configuration might be required in building structure applications necessitating regular structures from the first cavity. Streamlines contours indicates that the first rib behaves as a forward facing step when L1 > 5h (L1 is the first rib width), regular structures of the flow occurs from the first cavity. The effect of wider first rib is highlighted by friction and pressure coefficients profiles and those of the turbulent kinetic energy. Its effect also appears in the Darcy friction factor. The viscous and pressure forces applied on the first rib and the 5th pitch roughness indicate that the pressure force is dominant. Darcy friction factor characterizing the flow and pressure drag coefficient evaluated at the 5th pitch roughness remains independent of Reynolds number, while the drag force applied on the first rib increases when Reynolds number augments.
|
