No abstract

No abstract

with details of the nature of the infringement. We will investigate the claim and if justified, we will take the appropriate steps.

No abstract

No abstract

No abstract

Pulse-modulated dielectric barrier discharge plasma actuators are applied to the problem of flow separation on a Hermes 450 unmanned air vehicle V-tail panel. Risk-reduction airfoil experiments were conducted followed by full-scale wind tunnel tests. Silicone-rubber based actuators were calibrated and subsequently retrofitted to both the airfoil and the panel. A lightweight (1 kg), flightworthy high-voltage generator was used to drive the actuators. Airfoil and full-scale panel wind tunnel experiments showed a mild sensitivity to actuation reduced frequencies and duty cycles. On the panel, actuation produced a significant effect on post-stall control authority: for 17 • < α < 22 • a 100% increase in the post-stall lift coefficient was achieved; leading edge separation was prevented up to angles of attack of 30 • ; and hysteresis was virtually eliminated. Future research will focus on integrating the actuators into the panel geometry, implementing thicker dielectric materials and flight-testing.

A novel fluidic facemask, or Air-Screen, is described and demonstrated experimentally for protection against virus-laden aerosol and droplet infections, such as COVID-19. The Air-Screen employs a small, high-aspect-ratio, crossflow fan mounted on the visor of a filter-covered cap to produce a rectangular air jet, or screen, in front of the wearer’s face. A theoretical model, based on a weekly-advected jet in a crossflow, indicated its effectiveness against a wide spectrum of virus-laden aerosols and droplets. Qualitative flow visualization experiments, using a mannequin, clearly illustrated the Air-Screen’s ability to effectively block airborne droplets from the wearer’s face. Quantitative experiments to simulate droplets produced during sneezing or a wet cough, were propelled (via a transmitter) at an average velocity of 50 m/s at 1 m from the mannequin or a target. The Air-Screen blocked 62% of all droplets with a diameter of less than 150 µm. With an Air-Screen active on the transmitter, 99% of all droplets were blocked and when both mannequin and transmitter Air-Screens were active, 99.8% all droplets were blocked. In contrast to conventional facemasks, the Air-Screen is remarkably effective in protecting the wearer and others from an infected wearer.