Impact of Ground Effect on Circulation Controlled Cylindrical Surfaces

摘要

Circulation control technology and motion in close proximity to the ground have both shown aerodynamic benefits in the generation of lift. Recent research efforts at West Virginia University have explored the potential of merging the two phenomena, in an attempt to enhance both technologies. This paper initiates this combined effort by experimentally investigating the impact ground effect has on the separation location of a jet blown tangentially over circulation controlled cylindrical surfaces. Previous experimental research on circulation controlled cylinders found an optimal radius of curvature and volumetric flow rate; whose model and optimal findings are built upon by this work through the addition of ground effect analysis by varying the ground height. The experiment investigates some of the variables that individually influence circulation control and ground effect; the variables are the radius of curvature, velocity of the jet, and the height from the ground. Data analysis revealed that for a constant volumetric flow rate and varying the height to radius (h/r) value, there is a large amount of variability in the data, indicating that the proximity of the ground has significant impact on the separation location and consequently influence on the potential lift characteristics. Furthermore, when this flow rate was analyzed, it was found that at an h/r of approximately 4.8, it appears that an optimal h/r occurs, based on the surface pressure and flow separation from the cylinders when not influenced by the ground. The data also found that at both radii, 0.520 and 0.659 inches, showed benefit when tested in close proximity to the ground. The findings demonstrate that there is further enhancement potential of the lift generating capability by uniting the lift enhancement of circulation control methodology with the ground effect flight regime. This effort is a preliminary study of a larger effort to determine if merging the two phenomena indicates a lift enhancement. This model does not have a free stream velocity, and subsequently does not measure lift, however, the findings depicted in this effort indicate that there is potential for enhancement, which is currently being researched by the authors.