Linear Reduced-Order Model for Unsteady Aerodynamics of an L-Shaped Gurney Flap

Abstract

Analysis of ballistic capture orbits in Sun–planet systems is conducted in this paper. This mechanism utilizes purely gravitational forces, and may occur in non-Keplerian regimes. Ballistic capture orbits are generated by proper manipulation of sets of initial conditions that satisfy a simple definition of stability. Six Sun–planet systems are considered, including the inner planets, Jupiter, and Saturn. The role of planets orbital eccentricity, their true anomaly, and mass ratios is investigated. Moreover, the influence of the post-capture orbit in terms of inclination and orientation is also assessed. Analyses are performed from qualitative and quantitative perspective. The quality of capture orbits is measured by means of the stability index, whereas the capture ratio gives information on their statistical occurrence. Some underlying principles on the selection of the dynamical model, the initial true anomaly, and inclination are obtained. These provide a reference for practical cases

Numerical Assessment of Virtual Control Surfaces for Load Alleviation on Compressor Blades

“…This effect, which is consistent with the results of Refs. [18,19], may lead to possible drag increases compared to the baseline blade. Nevertheless, it will be hereinafter shown that no significant drag rises are encountered for both the actuated configurations.…”

“…It is worth remarking that these results are in qualitative agreement with the assessments of Refs. [16][17][18][19][20], where the same effects were obtained with a mechanical L-tab deflected downward or upward, installed on a helicopter blade section. Additionally, the computed flow fields are qualitatively consistent with the Particle Image Velocimetry measurements of Feng et al [21] on a low-speed fixed wing section with PS plasma actuation opposite to the freestream direction.…”

“…Both PS and SS actuations provide lift and pitching moment modifications, which are also quantitatively comparable to those of Refs. [16][17][18][19][20], achieved with a mechanical Gurney flap. In particular, PS actuation allows for increasing the lift coefficient without changing the blade angle of attack, and with no significant drawbacks in terms of drag.…”

“…Additionally, the light reductions of drag coefficient relative to the clean blade-encountered with both pressure and SS actuation-are in agreement with other results found in literature on trailing edge devices (see e.g., Refs. [16][17][18][19][20]49]). It is also worth remarking that the present fully-turbulent RANS assessments can't provide a quantitative evaluation of drag.…”

“…Here, plasma actuators are meant to reproduce qualitatively the effect of the mechanical L-tab investigated in Refs. [16][17][18][19][20] for rotorcraft vibration reduction. Specifically, plasma actuation is meant to develop vortical structures and recirculating flow areas similar to those generated by mechanical control surfaces (see, for instance, Ref.…”