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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1953

Analytical Investigation of Icing Limit for Diamond-Shaped Airfoil in Transonic and Supersonic Flow

Calculations have been made for the icing limit of a diamond airfoil at zero angle of attack in terms of the stream Mach number, stream temperature, and pressure altitude. The icing limit is defined as a wetted-surface temperature of 320 F and is related to the stream conditions by the method of Hardy. The results show that the point most likely to ice on the airfoil lies immediately behind the shoulder and is subject to possible icing at Mach numbers as high as 1.4.

Callaghan, Edmund E.↗
NASA NTRS1985

Impact of airfoil profile on the supersonic aerodynamics of delta wings

A nonlinear flow model was employed to predict the flowfield, pressure and force data for delta wings at supersonic speeds. The goal of the study was to investigate the influence the airfoil profiles has on the wing aerodynamics. The analysis covers wing aspect ratios from 0.5-3.0 with leading edge sweep of 0.5-4.0 on diamond, circular arc and NACA modified 4-digit airfoils. Nonlinear aerodynamics are approximated with nonlinear zero-lift wave drag curves, yielding results significantly different from those obtained from linear calculations. The analytical technique, useful in preliminary design studies, indicates in all cases that 90 percent of wave drag is generated at the wing apex and trailing edge.

Wood, R. M.↗
NASA NTRS2014

Flight Tests of a Supersonic Natural Laminar Flow Airfoil

IR thermography was used to characterize the transition front on a S-NLF test article at chord Reynolds numbers in excess of 30 million Changes in transition due to Mach number, Reynolds number, and surface roughness were investigated - Regions of laminar flow in excess of 80% chord at chord Reynolds numbers greater than 14 million IR thermography clearly showed the transition front and other flow features such as shock waves impinging upon the surface A series of parallel oblique shocks, of yet unknown origin, were found to cause premature transition at higher Reynolds numbers. NASA has a current goal to eliminate barriers to the development of practical supersonic transport aircraft Drag reduction through the use of supersonic natural laminar flow (S-NLF) is currently being explored as a means of increasing aerodynamic efficiency - Tradeoffs work best for business jet class at M<2 Conventional high-speed designs minimize inviscid drag at the expense of viscous drag - Existence of strong spanwise pressure gradient leads to crossflow (CF) while adverse chordwise pressure gradients amplifies and Tollmien-Schlichting (TS) instabilities Aerion Corporation has patented a S-NLF wing design (US Patent No. 5322242) - Low sweep to control CF - dp/dx < 0 on both wing surfaces to stabilize TS - Thin wing with sharp leading edge to minimize wave drag increase due to reduction in sweep NASA and Aerion have partnered to study S-NLF since 1999 Series of S-NLF experiments flown on the NASA F-15B research test bed airplane Infrared (IR) thermography used to characterize transition - Non-intrusive, global, good spatial resolution - Captures significant flow features well

laminar flow↗
NASA NTRS1950

The reversibility theorem for thin airfoils in subsonic and supersonic flow

A method introduced by Munk is extended to prove that the light-curve slope of thin wings in either subsonic flow or supersonic flow is the same when the direction of flight of the wing is reversed. It is also shown that the wing reversal does not change the thickness drag, damping-in-roll parameter or the damping-in-pitch parameter.

Brown, Clinton E↗
NASA NTRS1951

Theoretical characteristics of two-dimensional supersonic control surfaces

The "Busemann second-order-approximation theory" for the pressure distribution over a two-dimensional airfoil in supersonic flow was used to determine some of the aerodynamic characteristics of uncambered symmetrical parabolic and double-wedge airfoils with leading-edge and trailing-edge flaps. The characteristics presented and discussed in this paper are: flap effectiveness factor, rate of change of hinge-moment coefficient with flap deflection, rate of change of the pitching-moment coefficient with flap deflection, rate of change of the pitching-moment coefficient about the mid chord with flap deflection, and the location of the center of pressure of the airfoil-flap combination.

MACH NUMBER EFFECTS - WING SECTIONS↗
NASA NTRS1975

Noncompact source effect on the prediction of tone noise from a fan rotor

A comparison is made between the conventional compact source prediction for airfoil sound radiation and the rigorous prediction based on distributed sources along the airfoil chord. The theoretical analysis performed is for a single airfoil and cascaded airfoils immersed in a sinusoidally varying convected gust field. The pressure field around a single airfoil in supersonic gust flows is also studied. In subsonic flows the phase change of unsteady lift along the chord of a single airfoil reduces the sound radiation significantly in the upstream direction and increases the downstream radiation compared to the compact source prediction. In supersonic flows the compact source prediction gives substantial error in the region just behind the Mach wedge originating from the leading edge, while it approaches the noncompact source results far downstream from the airfoil. In the case of cascaded airfoils the compact source prediction overestimates the upstream radiation by as much as 20 dB depending on frequency and interblade phase.

Kaji, S.↗