Variation of the Solar He I 10830 A Line: 1977 - 1980

Daily measurements of the equivalent width of the 10830 A He I line integrated over the visible disk show: (1) an increase from about 32 to about 74 mA in the monthly mean values from the minimum to the maximum of the current solar cycle; (2) the monthly mean values are more smoothly varying than most other indices of solar activity; (3) rotation modulates the daily values in a highly variable manner with amplitudes as large as plus or minus 20%; (4) the apparent synodic rotation period is 29 days rather than the expected 27 days associated with active regions; (5) despite great differences in the appearance of the sun in 3933 A Ca I and 10830 A He I, the central intensity of the former correlates with the equivalent width of the latter with a value r = 0.97

Future regional/commuter challenges

Technological advances in the next ten years will represent a continuum of the steady improving state-of-the-art in all the major disciplines. In the past there was a number of step changes in technology, but no known really large quantum jumps are envisioned at present which could be readily applied to short haul aircraft. The one exception in the field of aerodynamics might be the application of natural laminar flow on short haul and laminar flow control on long haul aircraft. The aim in the 1990's will be to single out the major areas where advances will contribute to overcome important constraints such as fuel conservation, noise, airspace and airport saturation, and surface transportation competition

Effect of rod gap spacing on a suction panel for laminar flow and noise control in supersonic wind tunnels

Results are presented of a coordinated experimental and theoretical study of a sound shield concept which aims to provide a means of noise reduction in the test section of supersonic wind tunnels at high Reynolds numbers. The model used consists of a planar array of circular rods aligned with the flow, with adjustable gaps between them for boundary layer removal by suction, i.e., laminar flow control. One of the basic requirements of the present sound shield concept is to achieve sonic cross flow through the gaps in order to prevent lee-side flow disturbances from penetrating back into the shielded region. Tests were conducted at Mach 6 over a local unit Reynolds number range from about 1.2 x 10 to the 6th power to 13.5 x 10 to the 6th power per foot. Measurements of heat transfer, static pressure, and sound levels were made to establish the transition characteristics of the boundary layer on the rod array and the sound shielding effectiveness

The Resurrection as taught by early Friends

Writings from such early Friends as George Fox, and William Penn.https://digitalcommons.georgefox.edu/quakerbooks/1053/thumbnail.jp

The effect of cyclic feathering motions on dynamic rotor loads

The dynamic loads of a helicopter rotor in forward flight are influenced significantly by the geometric pitch angles between the structural axes of the hub and blade sections and the plane of rotation. The analytical study presented includes elastic coupling between inplane and out-of-plane deflections as a function of geometric pitch between the plane of rotation and the principal axes of inertia of each blade. The numerical evaluation is based on a transient analysis using lumped masses and elastic substructure techniques. A comparison of cases with and without cyclic feathering motion shows the effect on computed dynamic rotor loads

Influence of free-stream disturbances on boundary-layer transition

Considerable experimental evidence exists which shows that free stream disturbances (the ratio of root-mean-square pressure fluctuations to mean values) in conventional wind tunnels increase with increasing Mach number at low supersonic to moderate hypersonic speeds. In addition to local conditions, the free stream disturbance level influences transition behavior on simple test models. Based on this observation, existing noise transition data obtained in the same test facility were correlated for a large number of reference sharp cones and flat plates and are shown to collapse along a single curve. This result is a significant improvement over previous attempts to correlate noise transition data

Instrument accurately measures small temperature changes on test surface

Calorimeter apparatus accurately measures very small temperature rises on a test surface subjected to aerodynamic heating. A continuous thin sheet of a sensing material is attached to a base support plate through which a series of holes of known diameter have been drilled for attaching thermocouples to the material