Investigation of flow over rough surfaces

Abstract

Reduction of drag in fluid flow has been one of the main objectives of engineers in the field of fluid mechanics. Surfaces with biomimetic and superhydrophobic structures have proven to reduce drag for water and air flow. Superhydrophobic surfaces structure can be created by sanding the surface with sandpaper. However, studies using the combination of both biomimetic and superhydrophobic structures have not been carried out. Thus, this study aims to determine and identify the relationship between the sanded-riblets aluminium surface and the drag reduction in air flow. A total of 26 Aluminium test pieces, including 1 control, was investigated in this study. Test pieces were fabricated into 5 different sets of riblets spacing dimension. Different grits of sandpaper were used to sand the surface of the test pieces. A test rig was designed and fabricated in a way that the pressure drop across the Aluminium test piece can be measured with a differential manometer. Before sanding, among the 5 different sets of riblets spacing dimension, 0.2mm riblets spacing provided the best pressure drop reduction. After sanding with different sandpaper grits designation, sanded 0.5mm riblets spacing Aluminium test piece with sandpaper grits of 120 and sanded 0.4mm riblets spacing Aluminium test piece with sandpaper grits of 60 provided the best pressure drop reduction. Overall, sandpaper grits of 120 and 60 had a significant effect on the riblets Aluminium test piece. Sandpaper grits of 320 and 240 had minor effect on the riblets Aluminium test piece.