Impact of Ground Effect on Circulation Controlled Cylindrical Surfaces

Circulation control technology and motion in close proximity to the ground have both shown aerodynamicbenefits in the generation of lift. Recent research efforts at West Virginia University have explored thepotential of merging the two phenomena, in an attempt to enhance both technologies. This paper initiatesthis combined effort by experimentally investigating the impact ground effect has on the separationlocation of a jet blown tangentially over circulation controlled cylindrical surfaces. Previous experimentalresearch 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 effectanalysis by varying the ground height. The experiment investigates some of the variables that individuallyinfluence 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 andvarying the height to radius (h/r) value, there is a large amount of variability in the data, indicating that theproximity of the ground has significant impact on the separation location and consequently influence onthe potential lift characteristics. Furthermore, when this flow rate was analyzed, it was found that at an h/rof approximately 4.8, it appears that an optimal h/r occurs, based on the surface pressure and flowseparation 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 findingsdemonstrate that there is further enhancement potential of the lift generating capability by uniting the liftenhancement 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 alift 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 iscurrently being researched by the authors.