KAJIAN FENOMENA SEPARASI ALIRAN DAN SECONDARY FLOW PADA RECTANGULAR BEND 90⁰ UNTUK ANGKA REYNOLDS 68400

Abstract

Characteristics of flow through curved channels is very complicated. In the curved channel is formed due to secondary flow boundary layer interaction on the corner region. Effects caused by this secondary flow is blocked the flow, thereby reducing the flow effective area. The blockage of the flow will decrease the flow rate. In addition to the secondary flow, in curved channel occurs also separation flow. Separation process begins with the existence of a continuous fluid flow against the friction and obstacles in the form of adverse pressure gradient. Adverse pressure gradient on the fluid flow can cause the momentum of the flow decreases. If the flow does not have enough momentum to overcome the adverse pressure gradient, then this flow will separated and reverse direction from its main flow. In this Final Project research was carried out with experimental and numerical simulation methods. Studies carried out on rectangular bend 90°, at the Reynolds number 68400 (velocity inlet of fluid 15 m/s). The variables measured were the pressure on outer wall, inner wall, and radial section to obtain the pressure coefficient (Cp). Then the results pressure coefficient (Cp) experimental compared with simulations. In this simulation, Computational Fluid Dynamics (CFD) is used to predict the phenomenon of separation flow and secondary flow occurring. In this study indicated the phenomenon of secondary flow moves from the outer to the inner side and cause the blockage effect. In the experiments obtained discharge coefficient (Cd) = 1.040917, theoretical debit = 0.071958 m3/s, actual debit = 0.074902 m3/ s. And in the simulations obtained discharge coefficient (Cd) = 1,017981, theoretical debit = 0,073579 m3/s, actual debit = 0.074902 m3/ s.