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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Hot-wire coil probe for high-speed flows

Small-diameter-wire coil probes developed for use in a hypersonic helium tunnel are discussed. The springlike properties of the coil minimize strain-gauge effects, and allow to use a higher length-to-diameter ratio for a given flow. In addition, the coil is more rugged for sudden flow changes, and since it can be mounted straight across the support tips, there is less support interference in cross flows. In addition to measuring fluctuating quantities in a boundary layer, the probes were used with a constant temperature anemometer for measuring mean mass flow profiles, and with a constant current anemometer for measuring mean total temperature profiles.

Weinstein, L. M.↗
NASA NTRS1975

A hot-wire surface gage for skin friction and separation detection measurements

A heated-element, skin-friction gage employing a very low thermal conductivity support is described. It is shown that the effective dimension of the gage in the stream direction in only 0.06 mm, including the effects of heat conduction in the supporting material. Because of its small size, the calibration of the gage is independent of the kind of boundary-layer flow (whether laminar or turbulent) and is insensitive to pressure gradients. Construction tolerances can be maintained so that a single universal calibration can be applied. Multiple gages, sufficiently closely spaced so as to interfere with each other, are shown to provide accurate determinations of the locations of the points of boundary-layer separation and reattachment.

Rubesin, M. W.↗
NASA NTRS1976

Hot-wire probe

High-temperature platinum probe measures turbulence and Reynolds shear stresses in high-temperature compressible flows. Probe does not vibrate at high velocities and does not react like strain gage on warmup.

Mikulla, V.↗
NASA NTRS1977

All-nickel hot-wire probe

Device operates in supersonic and hypersonic wind tunnels at temperatures of 700 to 760 C.

Lemos, F. R.↗
NASA NTRS1977

Hot-wire tile removal tool

Cheesecutterlike device uses electrically heated wire to slice through thermosetting embedment. Technique does not damage tile or create unwanted debris in work area.

Holt, J. W.↗
NASA NTRS1975

Flush-mounted hot-wire gage for skin friction and separation detection measurements

A heated-element skin-friction gage employing a very low thermal-conductivity support is described. It is shown that the effective dimension of the gage in the stream direction is only 0.06 mm, including the effects of heat conduction in the supporting material. Because of its small size, the calibration of the gage is independent of the kind of boundary-layer flow (whether laminar or turbulent) and is insensitive to pressure gradients. Construction tolerances can be maintained so that a single universal calibration can be applied. Multiple gages, sufficiently closely spaced so as to interfere with each other, are shown to provide accurate determinations of the location of the points of boundary-layer separation and reattachment.

Rubesin, M. W.↗
NASA NTRS1977

A hot wire radiant energy source for mapping the field of view of a radiometer

The design and performance of a calibration device that allows the measurement of a radiometer's field of view are described. The heart of the device is a heated 0.0254-mm (0.001-inch) diameter filament that provides a variable, isothermal line source of radiant energy against a cold background. By moving this discrete line source across the field of view of a radiometer, the radiometer's spatial response can be completely mapped. The use of a platinum filament provides a durable radiation source whose temperature is stable and repeatable to 10 K over the range of 600 to 1200 K. By varying the energy emitted by the filament, the field of view of radiometers with different sensitivities (or multiple channel radiometers) can be totally mapped.

Edwards, S. F.↗
NASA NTRS1983

Ignition of confined gaseous mixtures by hot surfaces and hot wires

Ignition times and spatial and temporal variations of temperature and concentration in gaseous mixtures confined between two infinite parallel walls or two infinite cylinders have been obtained by numerical integration of the appropriate conservation equations written in Lagrangian coordinates. Ignition times and ignition energies are presented for the case of an isothermal wall in terms of the initial mixture pressure and equivalence ratio for both one and two-step chemical reaction mechanisms. The numerical results indicate that there is a critical mixture pressure for which the ignition time is minimum. The values of this critical pressure are larger (smaller) than 1 atm for the one- (two-) step reaction mechanism. The critical pressure for the ignition time is not equal to the critical pressure for the ignition energy. The ignition time and energy decrease with the equivalence ratio within a certain range and then remain constant.

Ramos, J. I.↗
NASA NTRS1985

Hot-Wire Probe for Compressible Subsonic Flow

Probe measures velocity, density, and total temperature fluctuations. Three-wire probe used with each wire operating at different overheat ratio. Technique extendable into transonic and low supersonic flow regimes without difficulty except for those problems usually associated with lengthy calibration and possible wire breaking.

Stainback, P. C.↗
NASA NTRS1984

Turbulence measurements in a complex flowfield using a crossed hot-wire

An X-wire probe was used to measure the time-mean and fluctuating velocities and shear stress in nonswirling nonreacting confined jet flows. Data were taken from an axisymmetric confined jet with an expansion ratio of 2 and an expansion angle of 90 deg, and from the same segment with a contraction nozzle. Velocity profiles developed faster in the confined jet than in the free jet, with the former experiencing higher turbulence levels and larger time-mean velocities. The X-wire is concluded to furnish more accurate results for the turbulent shear stress than a multioriented single-wire technique.

Lilley, D. G.↗
NASA NTRS1986

Transverse vorticity measurements using an array of four hot-wire probes

A comprehensive description of the technique used to obtain a time series of the quasi-instantaneous transverse vorticity from a four wire array of probes is presented. The algorithmic structure which supports the technique is described in detail and demonstration data, from a large plane shear layer, are presented to provide a specific utilization of the technique. Sensitivity calculations are provided which allow one contribution to the inherent uncertainty of the technique to be evaluated.

Foss, J. F.↗
NASA NTRS1986

Hot-wire measurements of a single lateral jet injected into swirling crossflow

In the present experiments documenting the time-mean and turbulent flowfield of a deflected turbulent jet in a combined, swirling crossflow, attention is given to a jet-to-crossflow velocity ratio of 4 at swirler vane angles of 45 and 70 deg. The results obtained are presented in the form of r-x plots in order to aid in three-dimensional flowfield visualization. The time-mean velocity measurements were found to closely correspond to pitot-probe data obtained in identical flow conditions. The lateral jet was found to deflect the axis of the precessing vortex core.

Lilley, D. G.↗