Experimental and Numerical Investigation of the Velocity Profiles through a Porous Medium Downstream of a Sharp Bend

摘要

This paper presents the experimental and numerical investigation of pressure driven flow through an annular porous medium, with fluid flowing through a 180° bend prior to the entrance region of the medium. Porous annuli of different lengths were constructed from foam material of solid volume fraction 0.25 and permeability of 1×10~(-9)m~2. Each model porous medium was positioned in a cylindrical chamber, adjacent to the sharp bend in its circumference. Velocity measurements, performed using particle image velocimetry (PIV), were used to determine the distance a fluid must travel from the 180° bend and through the porous medium before developing a flat velocity profile. This was achieved by measuring the velocity profiles of the fluid as it exited the porous media of different lengths. Optical transparency and refractive index matching techniques were used for visualization of the flow field. The flow field was also simulated using computational fluid dynamics (CFD), and the results were found to be in good agreement with experimental data. The results show that flow around the bend in the cylinders circumference has a significant effect on the velocity profile at the entrance region to the porous medium. A vortex is detected in the open chamber before the porous medium. The entrance velocity profile caused by this vortex affects the flow distribution in the first 9mm of the porous region. Subsequently, the flow becomes fully developed and a flat velocity profile is observed at all other porous material lengths.