| Description |
There are numerous applications in engineering in which the effects of roughness on fluid flow efficiency are important. This work is focused on better understanding the effects of roughness on the flow field downstream of a cambered (nonsymmetric) hydrofoil in a confined channel. Experiments were conducted using three different hydrofoils each having different levels of roughness and tested at three different angles of attack (0°, 10°, and 17°). Particle Image Velocimetry (PIV) was used to capture twodimensional vector fields. These data were used to estimate mean vorticity, terms of the Reynolds stress tensor, and terms of the Reynolds Averaged Navier-Stokes (RANS) equations. The work was exploratory in nature and did not give definitive answers to the questions posed. The results suggested that findings from experiments involving airfoils in unconfined environments and those involving hydrofoils near an air/water surface should not be generally applied to a confined environment. The experiments indicate that the effects of roughness are highly dependent on angle of attack. For the 0° experiments, roughness delayed separation and dampened turbulence intensity observed outside of the boundary layer. However, for the 10° and 17° experiments, flow over rougher hydrofoils separated earlier, while the effects on turbulence intensity were mixed-there was not any discernible monotonic pattern from the smoothest to roughest cases, with the middle roughness often being higher or lower than either of the other two. However, these findings are inconclusive due to the fact that the roughness profile was somewhat different, even though the equivalent sand grain roughness value was appropriate. All of the flow quantities calculated are shown graphically in the thesis and the appendices, and many additional observations were made beyond the scope of this abstract. The results of this work make a strong argument for further investigation of the effects of roughness on many flow quantities in confined flow, suggesting that the vast research done on hydrofoils in open flow-or potentially any objects-is not necessarily applicable. |
