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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Method and Apparatus for Measuring Fluid Flow

Method and apparatus for making measurements on fluids related to their complex permeability are disclosed. A microwave probe is provided for exposure to the fluids. The probe can be non-intrusive or can also be positioned at the location where measurements are to be made. The impedance of the probe is determined. in part. by the complex dielectric constant of the fluids at the probe. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids. Multiple probes may be selectively positioned to monitor the behavior of the fluids including their flow rate. Fluids may be identified as between two or more different fluids as well as multiple phases of the same fluid based on differences between their complex permittivities.

Arndt, G. Dickey↗
NASA NTRS1983

Determination of corrections to flow direction measurements obtained with a wing-tip mounted sensor

The nature of corrections for flow direction measurements obtained with a wing-tip mounted sensor was investigated. Corrections for the angle of attack and sideslip, measured by sensors mounted in front of each wing tip of a general aviation airplane, were determined. These flow corrections were obtained from both wind-tunnel and flight tests over a large angle-of-attack range. Both the angle-of-attack and angle-of-sideslip flow corrections were found to be substantial. The corrections were a function of the angle of attack and angle of sideslip. The effects of wing configuration changes, small changes in Reynolds number, and spinning rotation on the angle-of-attack flow correction were found to be small. The angle-of-attack flow correction determined from the static wind-tunnel tests agreed reasonably well with the correction determined from flight tests.

Moul, T. M.↗
NASA NTRS2002

Flow-Field Measurement of Device-Induced Embedded Streamwise Vortex on a Flat Plate

Detailed flow-field measurements were performed downstream of a single vortex generator (VG) using an advanced Stereo Digital Particle Image Velocimetry system. Thc passive flow-control devices examined consisted of a low-profile VG with a device height, h, approximately equal to 20 percent of the boundary-layer thickness, sigma, and a conventional VG with h is approximately sigma. Flow-field data were taken at twelve cross-flow planes downstream of the VG to document and quantify the evolution of embedded streamwise vortex. The effects of device angle of attack on vortex development downstream were compared between the low-profile VG and the conventional VG. Key parameters including vorticity, circulation, trajectory, and half-life radius - describing concentration, strength, path, and size, respectively--of the device-induced streamwise vortex were extracted from the flow-field data. The magnitude of maximum vorticity increases as angle of attack increases for the low-profile VG, but the trend is reversed for the conventional VG, probably due to flow stalling around the larger device at higher angles of attack. Peak vorticity and circulation for the low-profile VG decays exponentially and inversely proportional to the distance downstream from the device. The device-height normalized vortex trajectories for the low-profile VG, especially in the lateral direction, follow the general trends of the conventional VG. The experimental database was used to validate the predictive capability of computational fluid dynamics (CFD). CFD accurately predicts the vortex circulation and path; however, improvements are needed for predicting the vorticity strength and vortex size.

Yao, Chung-Sheng↗
NASA NTRS1979

Application of laser velocimetry to an unsteady transonic flow

Measurements of mean velocity, turbulent kinetic energy, and turbulent shear stress have been obtained in an unsteady but periodic flow. Polystyrene spheres, 0.35-0.55 microns in diameter, were injected into the tunnel settling chamber to seed the flow for a laser velocimeter. Synchronized counters together with an encoding interface and digital-to-analog converters were used to record the data on an analog tape recorder. Profiles of velocity and turbulence quantities are presented for several times during the periodic flow.

Seegmiller, H. L.↗
NASA NTRS2012

James Webb Space Telescope Integrated Science Instrument Module Calibration and Verification of High-Accuracy Instrumentation to Measure Heat Flow in Cryogenic Testing

The James Webb Space Telescope (JWST) is an upcoming flagship observatory mission scheduled to be launched in 2018, Three of the four science instruments are passively cooled to their operational temperature range of 36K to 40K, and the fourth instrument is actively cooled to its operational temperature of approximately 6K. The requirement for multiple thermal zones results in the instruments being thermally connected to five external radiators via individual high purity aluminum heat straps. Thermal-vacuum and thermal balance testing of the flight instruments at the Integrated Science Instrument Module (ISIM) element level will take place within a newly constructed shroud cooled by gaseous helium inside Goddard Space Flight Center's (GSFC) Space Environment Simulator (SES). The flight external radiators are not available during ISIM-Ievel thermal vacuum/thermal testing, so they will be replaced in test with stable and adjustable thermal boundaries with identical physical interfaces to the flight radiators. Those boundaries are provided on specially designed test hardware which measures the heat flow within each of the five heat straps to an accuracy of less than 2 m W, which is less than 5% of the minimum predicted heat flow values. This is essential to ISIM thermal model correlation, since thermal models are more accurately correlated when temperature data is supplemented by accurate knowledge of heat flows. Devices that measure heat flow in this manner have historically been referred to as "Q-meters". Perhaps the most important feature of the design of the Q-meters is that it does not depend on the absolute accuracy of its temperature sensors, but rather on a difference in heater power, for which a table is empirically developed during a calibration campaign in a small chamber at GSFC. This paper discusses the Q-meter calibration procedure including calibration chamber modifications and accommodations, the handling of differing conditions between calibration and usage, the calibration process itself, and the results of the tests used to determine if the calibration is successful.

Comber, Brian↗
NASA NTRS2017

Position Corrections for Airspeed and Flow Angle Measurements on Fixed-Wing Aircraft

This report addresses position corrections made to airspeed and aerodynamic flow angle measurements on fixed-wing aircraft. These corrections remove the effects of angular rates, which contribute to the measurements when the sensors are installed away from the aircraft center of mass. Simplified corrections, which are routinely used in practice and assume small flow angles and angular rates, are reviewed. The exact, nonlinear corrections are then derived. The simplified corrections are sufficient in most situations; however, accuracy diminishes for smaller aircraft that incur higher angular rates, and for flight at high air flow angles. This is demonstrated using both flight test data and a nonlinear flight dynamics simulation of a subscale transport aircraft in a variety of low-speed, subsonic flight conditions.

Grauer, Jared A.↗
NASA NTRS1981

The velocity field near the orifice of a Helmholtz resonator in grazing flow

Measurement of the time-dependent velocities induced inside and outside the opening of acoustically excited, two-dimensional Helmholtz resonator imbedded in a grazing flow are presented. The remarkably clear structure of the perturbation field which evokes a pulsating source and a coherently pulsating vortex-image pair is described. The simple phenomenological "lid-model" which correlates the variation in the components of the acoustic impedance with the velocity of the grazing flow is discussed and extended.

Charwat, A. F.↗
NASA NTRS2008

Flow-Field Measurement of a Hybrid Wing Body Model with Blown Flaps

In this paper we describe flow-field measurements obtained in the wake of a full-span Hybrid Wing Body model with internally blown flaps. The test was performed at the NASA Langley 14 x 22 Foot Subsonic Tunnel at low speeds. Off-body measurements were obtained with a 7-hole probe rake survey system. Three model configurations were investigated. At 0deg angle of attack the surveys were completed with 0deg and 60deg flap deflections. At 10deg angle of attack the wake surveys were completed with a slat and a 60deg flap deflection. The 7-hole probe results further quantified two known swirling regions (downstream of the outboard flap edge and the inboard/outboard flap juncture) for the 60deg flap cases with blowing. Flow-field results and the general trends are very similar for the two blowing cases at nozzle pressure ratios of 1.37 and 1.56. High downwash velocities correlated with the enhanced lift for the 60deg flap cases with blowing. Jet-induced effects are the largest at the most inboard station for all (three) velocity components due in part to the larger inboard slot height. The experimental data are being used to improve computational tools for high-lift wings with integrated powered-lift technologies.

Lin, John C.↗
NASA NTRS1994

Adaptive-wall wind-tunnel research at Ames Research Center: A retrospective

This paper reviews adaptive-wall wind-tunnel research conducted at Ames Research Center between 1978 and 1988. This research focused on developing ways to apply the concept of adaptive walls in transonic test sections with ventilated walls. In the approach pursued at Ames, local mass flow through slotted test-section walls was controlled by adjusting the pressure in compartments of a segmented plenum; the flow measurements required to test compatibility of the wind-tunnel flow with free-air boundary conditions were made using a laser velocimeter; empirical influence coefficients were used to predict how pressure changes in the plenum would effect the flow. Both two- and three-dimensional proof-of-concept experiments were conducted in a small indraft wind tunnel. Subsequently, a two-dimensional test section was demonstrated in the Ames 2x2 ft. Transonic Wind Tunnel-a wind tunnel representative of a production facility. The 2x2 ft.tests showed large reductions of wall interference; however, the time required to make the necessary flow measurements and plenum pressure adjustments far exceeded what would be acceptable for production testing. This was primarily because the imaginary surface where free-air compatibility was tested had to be separated from the test section walls to avoid the complex, viscous flow adjacent to the walls. It is unlikely that the Ames approach to adaptive walls will be applied in production wind tunnels. The two biggest unresolved problems are how to quickly and accurately make the necessary flow measurements and how to predict the effects of wall adjustments. In contrast, flexible-wall technology for two-dimensional testing is ready for application in production wind tunnels. However, neither the ventilated- nor flexible-wall approach has been shown to be a technically viable and cost-effective solution to the three-dimensional adaptive wall problem.

Schairer, Edward T.↗
NASA NTRS1999

Aerodynamic Flow Field Measurements for Automotive Systems

The design of a modern automotive air handling system is a complex task. The system is required to bring the interior of the vehicle to a comfortable level in as short a time as possible. A goal of the automotive industry is to predict the interior climate of an automobile using advanced computational fluid dynamic (CFD) methods. The development of these advanced prediction tools will enable better selection of engine and accessory components. The goal of this investigation was to predict methods used by the automotive industry. To accomplish this task three separate experiments were performed. The first was a laboratory setup where laser velocimeter (LV) flow field measurements were made in the heating and air conditioning unit of a Ford Windstar. The second involved flow field measurements in the engine compartment of a Ford Explorer, with the engine running idle. The third mapped the flow field exiting the center dashboard panel vent inside the Explorer, while the circulating fan operated at 14 volts. All three experiments utilized full-coincidence three-component LV systems. This enabled the mean and fluctuating velocities to be measured along with the Reynolds stress terms.

Hepner, Timothy E.↗
NASA NTRS2005

Molecular Rayleigh Scattering Techniques Developed for Measuring Gas Flow Velocity, Density, Temperature, and Turbulence

Nonintrusive optical point-wise measurement techniques utilizing the principles of molecular Rayleigh scattering have been developed at the NASA Glenn Research Center to obtain time-averaged information about gas velocity, density, temperature, and turbulence, or dynamic information about gas velocity and density in unseeded flows. These techniques enable measurements that are necessary for validating computational fluid dynamics (CFD) and computational aeroacoustic (CAA) codes. Dynamic measurements allow the calculation of power spectra for the various flow properties. This type of information is currently being used in jet noise studies, correlating sound pressure fluctuations with velocity and density fluctuations to determine noise sources in jets. These nonintrusive techniques are particularly useful in supersonic flows, where seeding the flow with particles is not an option, and where the environment is too harsh for hot-wire measurements.

Mielke, Amy F.↗
NASA NTRS1995

Multiwire Thermocouples in Reversing Flow

Measurements are recorded for multiwire thermocouples consisting of either two or three wires of unequal diameters. Signals from the multiwire probe are recorded for a reversing gas flow with both a periodic temperature and time constant fluctuation. It is demonstrated that the reconstructed signal from the multiwire thermocouple requires no compensation provided omega/omega(sub 1) less than 2.3 for two wires or omega/omega(sub 1) less than 3.6 for three wires where omega(sub 1) (= 2(pi)f) is the natural frequency of the smaller wire based on the maximum gas velocity. The latter results were possible provided Fourier transformed data from the wires were used and knowledge of the gas velocity phase angle was available.

Forney, L. J.↗
NASA NTRS2020

Multi-Point Line Focused Laser Differential Interferometer for High-Speed Flow Fluctuation Measurements

A multi-point focused laser differential interferometer (FLDI) has been developed to measure density fluctuations at 16 points along a line. A pair of cylindrical lenses on the transmitter side of a conventional single-point FLDI instrument form two closely spaced (≤200 μm), orthogonally polarized, parallel laser lines at the instrument’s focus. On the receiver side of the instrument, the interference of the beams on a 16-element photodiode array results in a single line of measurements. The further addition of a Nomarski prism creates two separate measurement lines, and the addition of a second photodiode array to the instrument enables simultaneous measurements of density fluctuations along the two lines separated by several millimeters. These two lines of measurement can be conveniently oriented at any azimuthal angle relative to the instrument’s optical axis on the measurement plane, coinciding with the instrument’s focus. Two experiments were performed to demonstrate the capabilities of the instrument. In the first experiment, a laser-induced breakdown spark generated a traveling spherical shock wave, and measurements of the resulting density disturbance and wave velocity were obtained. These results were compared to high-speed schlieren images of the shock wave acquired at 400 kHz. In the second experiment, the multi-point FLDI instrument was used to measure density disturbances in the boundary layer of a flat plate in a Mach 6 freestream flow. The measurements were made along two lines, both approximately 6 mm in length, extending from the surface of the plate through the boundary layer. High-speed schlieren images were acquired at 100 kHz during separate wind tunnel runs at matching unit Reynolds numbers to visualize the unsteady boundary layer flow and compare to the FLDI measurements.

Laser beam shaping↗
NASA NTRS1996

NMRI Measurements of Flow of Granular Mixtures

We investigate complex 3D behavior of granular mixtures in shaking and shearing devices. NMRI can non-invasively measure concentration, velocity, and velocity fluctuations of flows of suitable particles. We investigate origins of wall-shear induced convection flow of single component particles by measuring the flow and fluctuating motion of particles near rough boundaries. We also investigate if a mixture of different size particles segregate into their own species under the influence of external shaking and shearing disturbances. These non-invasive measurements will reveal true nature of convecting flow properties and wall disturbance. For experiments in a reduced gravity environment, we will design a light weight NMR imager. The proof of principle development will prepare for the construction of a complete spaceborne system to perform experiments in space.

Nakagawa, Masami↗
NASA NTRS2012

Subsurface Supergranular Vertical Flows as Measured Using Large Distance Separations in Time-Distance Helioseismology

As large-distance rays (say, 10-24 deg) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large separation travel times associated with upergranulation cannot be studied using the standard phase-speed filters of time-distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations,reduce the resultant travel time signal by at least an order of magnitude at some distances. More effective filters are derived. Modeling suggests that the center-annulus travel time difference in the separation range 10-24 deg is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a constant signal from the vertical flow. Our measurement of this quantity for the average supergranule, 5.1 s, is constant over the distance range. This magnitude of signal cannot be caused by the level of upflow at cell centers seen at the photosphere of 10 m/s extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of 240 m/s at a depth of 2.3 Mm and a peak horizontal flow of 700 m/s at a depth of 1.6 Mm.

Duvall, T. L., Jr.↗
NASA NTRS2012

Subsurface Supergranular Vertical Flows as Measured Using Large Distance Separations in Time-Distance Helioseismology

As large-distance rays (say, 10 - 24deg) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large-separation travel times associated with supergranulation cannot be studied using the standard phase-speed filters of time-distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations, reduce the resultant travel time signal by at least an order of magnitude at some distances. More effective filters are derived. Modeling suggests that the center-annulus travel-time difference [outward-going time minus inward-going time] in the separation range delta= 10 - 24deg is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a constant signal from the vertical flow. Our measurement of this quantity, 5.1+/-0.1 seconds, is constant over the distance range. This magnitude of the signal cannot be caused by the level of upflow at cell centers seen at the photosphere of 10 ms(exp−1) extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of 240 ms(exp−1) at a depth of 2.3 Mm and a peak horizontal flow of 700 ms(exp−1) at a depth of 1.6 Mm.

convection↗
NASA NTRS2002

Laser Light Scattering Diagnostic for Measurement of Flow Velocity in Vicinity of Propagating Shock Waves

A laser light scattering diagnostic for measurement of dynamic flow velocity at a point is described. The instrument is being developed for use in the study of propagating shock waves and detonation waves in pulse detonation engines under development at the NASA Glenn Research Center (GRC). The approach uses a Fabry-Perot interferometer to measure the Doppler shift of laser light scattered from small (submicron) particles in the flow. The high-speed detection system required to resolve the transient response as a shock wave crosses the probe volume uses fast response photodetectors, and a PC based data acquisition system. Preliminary results of measurements made in the GRC Mach 4, 10 by 25 cm supersonic wind tunnel are presented. Spontaneous condensation of water vapor in the flow is used as seed. The tunnel is supplied with continuous air flow at up to 45 psia and the flow is exhausted into the GRC laboratory-wide altitude exhaust system at pressures down to 0.3 psia.

Seasholtz, Richard G.↗
NASA NTRS1975

Detailed transonic flow field measurements about a supercritical airfoil section

The transonic flow field about a Whitcomb-type supercritical airfoil profile was measured in detail. In addition to the usual surface pressure distributions and wake surveys, schlieren photographs were taken and velocity vector profiles were determined in the upper surface boundary layer and in the near wake. Spanwise variations in the measured pressures were also determined. The data are analyzed with the aid of an inviscid transonic finite-difference computer program as well as with boundary layer modeling and calculation schemes.

Hurley, F. X.↗