This work reports aerodynamic testing of two spanwise-oscillating surfaces fabricated out of electroactive polymers (EAPs) in the dielectric form of actuation (DEA), and of an electromagnetic-driven linear motor. Hot-wire and PIV measurements of velocity and direct measurement of friction drag using a drag balance are presented. A maximum of 16% surface friction reduction, as calculated by the diminution of the wall-normal streamwise velocity gradient was obtained. Among other quantities, the spatial dependence of the drag reduction was investigated. When this spatial transient and portions which are static are accounted for, the direct drag measurements complement the hot-wire data. PIV measurements where the laser beam was parallel to the oscillating surface at y + ≈ 15, support the hot-wire data. The two actuators are original in design and significant contributions have been made to the development of EAPs. This experiment is the first to aerodynamically test EAP actuators at such a large scale and at a relatively moderate Re.
This paper describes experiments relating to the buffet response and control of a section of a long-span suspension bridge deck elastically mounted as part of a wind tunnel experiment. The bridge section is subject to grid generated flow turbulence. Two grids are used -one is a standard biplanar grid, while the second is a new design that provides larger turbulence length scales. The buffet response results are compared with admittances calculated using unsteady, three-dimensional, lifting-surface theory that extends standard two-dimensional Sears' theory. The bridge deck heave and pitch responses are predicted with comparisons made with wind tunnel measurements. In order to suppress buffeting, and increase the deck's critical flutter speed, the deck model is fitted with controllable leading-and trailing-edge flaps. Two sets of passive controllers, which use the flap angles as the control inputs, are demonstrated and evaluated for their capability to suppress the buffet response of the deck and increase its critical flutter speed. The first set of controllers sense the deck's position (pitch angle and heave, or pitch angle alone), whilst the second set (which are mechanical controllers) sense the vertical velocity of the flap hinge points. The control system design problem is solved as a mixed H 2 /H ∞ optimisation problem. The wind tunnel experPreprint submitted to Fluids and Structures June 14, 2016 iments show that these control systems can reduce considerably the deck's buffet response, whilst simultaneously increasing its critical flutter speed.
Novel methods were applied to investigate the temporal profiles of nasal inspiration. Characteristic features of the profile were identified and found to be significantly different between inspiration at rest and sniffing. Decongestion was found to have little effect on the temporal profiles for the flow regimes studied.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.