Experimental and numerical study on the boundary layer flow over a flat plate with a semi-circular bump with and without a transversal wire

Abstract

Flow behavior over a bump attached on a flat plate has significant effect on the total drag. The drag comprises of pressure and friction or viscous drags. Attaching a disturbance on the bump surface affects significantly on the contribution of pressure and viscous drag. This study is intended to examine the effect of a small wire (tripping wire) attachment on a semi-circular bump surface on the flow characteristics over the semi-circular bump. Special attention of this study is to examine the drag characteristics, pressure distribution, and boundary layer separation point from the bump surface. The study was conducted using experimental and numerical methods. The experiments were conducted in a low-speed wind tunnel at a freestream velocity of 16.5 m/s, corresponding to the flow Reynolds number (Re) of approximately 2.1 × 105. Flat plates with a semi-circular bump with and without wire were attached in the wind tunnel test section used as model tests. The wire is attached at three different angle (θ) locations of the bump surface, namely θ = 30 deg, 40 deg, and 50 deg. The pressure distribution on the plate surface as well as on the bump surface is measured using static pressure taps connected to U-tube manometer. From the pressure distribution, then the pressure drag is obtained from the integration of pressure distribution on the surface. Fluid velocity is measured using a Pitot static tube. Numerical studies was conducted using a commercial software the Fluent. A 2-D, steady flow turbulent model k-ω shear-stress transport (SST) was used in this study. In the numerical simulation, the grid independency test is performed to ensure better results. The results of the study show that the presence of a small wire attached on the bump surface increases to the total drag of the model for all values of θ. Also, the boundary layer separation point on the bump surface for all values of θ occurs at smaller angle comparing to that of the bump without wire. Results from the experimental study compare very well to the results obtained from the numerical simulations with a maximum difference of approximately 5 percent. In this study, the maximum drag occurs for the bump with the tripping wire attached at θ = 50 deg.Flow behavior over a bump attached on a flat plate has significant effect on the total drag. The drag comprises of pressure and friction or viscous drags. Attaching a disturbance on the bump surface affects significantly on the contribution of pressure and viscous drag. This study is intended to examine the effect of a small wire (tripping wire) attachment on a semi-circular bump surface on the flow characteristics over the semi-circular bump. Special attention of this study is to examine the drag characteristics, pressure distribution, and boundary layer separation point from the bump surface. The study was conducted using experimental and numerical methods. The experiments were conducted in a low-speed wind tunnel at a freestream velocity of 16.5 m/s, corresponding to the flow Reynolds number (Re) of approximately 2.1 × 105. Flat plates with a semi-circular bump with and without wire were attached in the wind tunnel test section used as model tests. The wire is attached at three different angle (θ) loca...