An Aerodynamic Assessment of Micro-Drag Generators (MDGs)
Commercial transports as well as fighter aircraft of the future are being designed with very low drag (friction and pressure). Concurrently, commuter airports are being built or envisioned to be built in the centers of metropolitan areas where shorter runways and/or reduced noise footprints on takeoff and landing are required. These requirements and the fact that drag is lower on new vehicles than on older aircraft have resulted in vehicles that require a large amount of braking force (from landing-gear brakes, spoilers, high-lift flaps, thrust reversers, etc.). Micro-drag generators (MDGs) were envisioned to create a uniformly distributed drag force along a vehicle by forcing the flow to separate on the aft-facing surface of a series of deployable devices, thus, generating drag. The devices are intended to work at any speed and for any type of vehicle (aircraft, ground vehicles, sea-faring vehicles). MDGs were applied to a general aviation wing and a representative fuselage shape and tested in two subsonic wind tunnels. The results showed increases in drag of 2 to 6 times that of a "clear" configuration.
Aircraft Excrescence Drag
Abstract : A review has been undertaken of the available data on the subject of the drag of excrescences on aircraft surfaces. Information from this review has been summarized and presented in a way that is readily usable for prediction and design purposes. The basic characteristics of boundary layers are discussed and, where possible, the drag of excrescences is related to those characteristics. In particular, because the size of many types of surface imperfection is small in comparison with boundary layer thicknesses, the drag of such imperfections can be correlated in terms of the properties of inner regions of the boundary layer. Several previously published analyses of this type are highlighted and, where possible, extensions to other data sources or other types of excrescence are presented. The practical problems of applying these data in the varying velocity gradients existing on aircraft surfaces are treated and one section is devoted to the drag of auxiliary air inlet and exit openings. Gaps in existing data which offer opportunities for research effort are pointed out.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.