4,277 research outputs found
Overview of NASA PTA propfan flight test program
The progress is covered of the NASA sponsored Propfan Test Assessment (PTA) flight test program. In PTA, a 9 ft. diameter propfan was installed on the left wing of a Gulfstream GII executive jet and is undergoing extensive flight testing to evaluate propfan structural integrity, near and far field noise, and cabin interior noise characteristics. This research testing includes variations in propeller tip speed and power loading, nacelle tilt angle, and aircraft Mach number and altitude. As a result, extensive parametric data will be obtained to verify and improve computer codes for predicting propfan aeroelastic, aerodynamic, and aeroacoustic characteristics. Over 600 measurements are being recorded for each of approx. 600 flight test conditions
Second order mean field games with degenerate diffusion and local coupling
We analyze a (possibly degenerate) second order mean field games system of
partial differential equations. The distinguishing features of the model
considered are (1) that it is not uniformly parabolic, including the first
order case as a possibility, and (2) the coupling is a local operator on the
density. As a result we look for weak, not smooth, solutions. Our main result
is the existence and uniqueness of suitably defined weak solutions, which are
characterized as minimizers of two optimal control problems. We also show that
such solutions are stable with respect to the data, so that in particular the
degenerate case can be approximated by a uniformly parabolic (viscous)
perturbation
Summary of recent investigations of inlet flow distortion effect on engine stability
A review is presented of recent experimental results, analytical procedures and test techniques employed to evaluate the effects of inlet flow distortion on the stability characteristics of representative afterburning turbofan and turbojet compression systems. Circumferential distortions of pressure and temperature, separately and in combination are considered. Resulting engine sensitivity measurements are compared with predictions based on simplified parallel compressor models and with several distortion descriptor parameters
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