SEARCH · Engineering Papers

Results for “flow”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64

All sources NASA NTRS DOE OSTI

NASA NTRS1977

Flow separation detector

An arrangement for sensing the fluid separation along a surface which employs a thermally insulating element having a continuous surface blending into and forming a part of the fluid flow surface is described. A sudden decrease in the temperature of the downstream sensor conductor and concomitant increase in the temperature of the upstream sensor conductor is an indication of the separation. When the temperatures are returned to the state achieved during normal flow, the indicator thereby indicates the normal, attached fluid flow. The conductors may be, for example, wires or thin films, and should be within the viscous sub-layer of the expected fluid flow. A single heater and several pairs of sensors and corresponding sensor conductors may be used to detect not only the fluid flow and the separation, but the direction of the fluid flow, over the fluid flow surface.

Mateer, G. C.↗

NASA NTRS1978

A method of calibrating wind velocity sensors with a modified gas flow calibrator

A procedure was described for calibrating air velocity sensors in the exhaust flow of a gas flow calibrator. The average velocity in the test section located at the calibrator exhaust was verified from the mass flow rate accurately measured by the calibrator's precision sonic nozzles. Air at elevated pressures flowed through a series of screens, diameter changes, and flow straighteners, resulting in a smooth flow through the open test section. The modified system generated air velocities of 2 to 90 meters per second with an uncertainty of about two percent for speeds below 15 meters per second and four percent for the higher speeds. Wind tunnel data correlated well with that taken in the flow calibrator.

Stump, H. P.↗

NASA NTRS1976

Upper-surface-blowing flow-turning performance

Jet exhaust flow-turning characteristics were determined for systematic variations in upper-surface blowing exhaust nozzles and trailing-edge flap configuration variables from experimental wind-off (static) flow studies. For conditions with parallel flow exhausting from the nozzle, jet height (as indicated by nozzle exit height) and flap radius were found to be the most important parameters relating to flow turning. Nonparallel flow from the nozzle, as obtained from an internal roof angle and/or side spread angle, had a large favorable effect on flow turning. Comparisons made between static turning results and wind tunnel aerodynamic studies of identical configurations indicated that static flow-turning results can be indicative of wind-on powered lift performance for both good and poor nozzle-flap combinations but, for marginal designs, can lead to overly optimistic assessment of powered lift potential.

Sleeman, W. C., Jr.↗

NASA NTRS1978

Laser velocimeter application to oscillatory liquid flows

A laser velocimeter technique was used to measure the mean velocity and the frequency characteristics of an oscillatory flow component generated with a rotating flapper in liquid flow system at Reynolds numbers approximating 93,000. The velocity information was processed in the frequency domain using a tracker whose output was used to determine the flow spectrum. This was accomplished with the use of an autocorrelator/Fourier transform analyzer and a spectrum averaging analyzer where induced flow oscillations up to 40 Hz were detected. Tests were conducted at a mean flow velocity of approximately 2 m/s. The experimental results show that the laser velocimeter can provide quantitative information such as liquid flow velocity and frequency spectrum with a possible application to cryogenic fluid flows.

Gartrell, L. R.↗

NASA NTRS1976

Circulation system for flowing uranium hexafluoride cavity reactor experiments

Research related to determining the feasibility of producing continuous power from fissile fuel in the gaseous state is presented. The development of three laboratory-scale flow systems for handling gaseous UF6 at temperatures up to 500 K, pressure up to approximately 40 atm, and continuous flow rates up to approximately 50g/s is presented. A UF6 handling system fabricated for static critical tests currently being conducted is described. The system was designed to supply UF6 to a double-walled aluminum core canister assembly at temperatures between 300 K and 400 K and pressure up to 4 atm. A second UF6 handling system designed to provide a circulating flow of up to 50g/s of gaseous UF6 in a closed-loop through a double-walled aluminum core canister with controlled temperature and pressure is described. Data from flow tests using UF6 and UF6/He mixtures with this system at flow rates up to approximately 12g/s and pressure up to 4 atm are presented. A third UF6 handling system fabricated to provide a continuous flow of UF6 at flow rates up to 5g/s and at pressures up to 40 atm for use in rf-heated, uranium plasma confinement experiments is described.

Jaminet, J. F.↗

NASA NTRS1978

Some flow phenomena in a constant area duct with a Borda type inlet including the critical region

Mass limiting flow characteristics for a 55 L/D tube with a Borda type inlet were assessed over large ranges of temperature and pressure, using fluid nitrogen. Under certain conditions, separation and pressure drop at the inlet was sufficiently strong to permit partial vaporization and the remaining fluid flowed through the tube as if it were a free jet. An empirical relation was determined which defines conditions under which this type of flow can occur. A flow coefficient is presented which enables estimations of flow rates over the experimental range. A flow rate stagnation pressure map for selected stagnation isotherms and pressure profiles document these flow phenomena.

Hendricks, R. C.↗

NASA NTRS1977

Similarity laws of lunar and terrestrial volcanic flows

A mathematical model for the terrestrial and lunar volcanic flows is proposed. This mathematical model, which is one-dimensional, steady duct flow of a mixture of a gas and small solid particles (rock), has been analyzed in detail. The similarities and the differences of the essential features of lunar and terrestrial volcanic flows are determined. Numerical results for the equilibrium two-phase flows of lunar and terrestrial volcanics under similar conditions are presented. The main results of the theoretical model are: the lunar crater is much larger than the corresponding terrestrial crater; the exit velocity from the lunar volcanic flow may be higher than the lunar escape velocity but the exit velocity of terrestrial volcanic flow is much less than that of the linear case (this result confirms the hypothesis that Australian tektites came from the moon, as a stream of rock and gas of extremely high speed), and the thermal effects on the lunar volcanic flow are much larger than those in the terrestrial case.

Pai, S. I.↗

NASA NTRS1977

Comparison of numerical and experimental 'conical' flow fields in supersonic corners with compression and/or expansion

The flow field produced by the intersection of two plane solid surfaces in a supersonic stream is a complex interference flow. These flows can be fully compressive, fully expansive, or of mixed compression-expansion nature. This paper presents a comparison of the experimentally obtained flow-field structure in an axial corner with that predicted numerically by using a shock-capturing finite-difference method. The effect of sweep and surface deflection are evaluated, and the general influence of each is presented for the three classes of corner flow. The results show that the numerical method is a valuable aid in understanding the flow structure for simple configurations. In addition, confidence in the numerical method is gained for use in solving more general three-dimensional configurations where the flow is nonconical and several wave interaction may be presented.

Anderson, D. A.↗

NASA NTRS1978

Plasma flows and magnetic field vectors in the plasma sheet during substorms

A detailed study of the plasma flow and the magnetic field vector in the plasma sheet during magnetospheric substorms is made to determine whether plasma flows are field-aligned or crossfield. It is shown that there is generally a large magnetic field-aligned component in the rapid plasma flow observed in the plasma sheet during substorms. In particular, the larger the observed flow speed, the closer the observed flow direction is aligned with the magnetic field line. There is no clear association between the plasma flow direction and the sign of the Bz component of the magnetic field during plasma sheet thinnings at substorms. The rapid plasma flows observed in the magnetotail are predominantly magnetic field-aligned.

Lui, A. T. Y.↗

NASA NTRS1978

A water tunnel flow visualization study of the F-15

Water tunnel studies were performed to qualitatively define the flow field of the F-15 aircraft. Two lengthened forebodies, one with a modified cross-sectional shape, were tested in addition to the basic forebody. Particular emphasis was placed on defining vortex flows generated at high angles of attack. The flow visualization tests were conducted in the Northrop diagnostic water tunnel using a 1/48-scale model of the F-15. Flow visualization pictures were obtained over an angle-of-attack range to 55 deg and sideslip angles up to 10 deg. The basic aircraft configuration was investigated in detail to determine the vortex flow field development, vortex path, and vortex breakdown characteristics as a function of angle of attack and sideslip. Additional tests showed that the wing upper surface vortex flow fields were sensitive to variations in inlet mass flow ratio and inlet cowl deflection angle. Asymmetries in the vortex systems generated by each of the three forebodies were observed in the water tunnel at zero sideslip and high angles of attack.

Lorincz, D. J.↗

NASA NTRS1979

Laminar and turbulent flows over spherically blunted cone and hyperboloid with massive surface blowing

Numerical solutions are presented for the flow over a spherically blunted cone and hyperboloid with massive surface blowing. Time-dependent viscous shock-layer equations are used to describe the flow field. The boundary conditions on the body surface include a prescribed blowing-rate distribution. The governing equations are solved by a time-asymptotic finite-difference method. Results presented here are only for a perfect gas-type flow at zero angle of attack. Both laminar and turbulent flow solutions are obtained. It is found that the effect of the surface blowing on the laminar flow field is to smooth out the curvature discontinuity at the sphere-cone juncture point, which results in a positive pressure gradient over the body. The shock slope increases on the downstream portion of the body as the surface blowing rate is increased. The turbulent flow with surface blowing is found to redevelop a boundary-layer-like region near the surface. The effects of this boundary-layer region on the flow field and heating rates are discussed.

Kumar, A.↗

NASA NTRS1979

Effect of grazing flow on the acoustic impedance of Helmholtz resonators consisting of single and clustered orifices

A semiempirical fluid mechanical model is derived for the acoustic behavior of thin-walled single orifice Helmholtz resonators in a grazing flow environment. The incident and cavity sound fields are connected in terms of an orifice discharge coefficient whose values are determined experimentally using the two-microphone method. Measurements show that at high grazing flow speeds, acoustical resistance is almost linearly proportional to the grazing flow speed and almost independent of incident sound pressure. The corresponding values of reactance are much smaller and tend towards zero. For thicker-walled orifice plates, resistance and reactance were observed to be less sensitive to grazing flow as the ratio of plate thickness to orifice diameter increased. Loud tones were observed to radiate from a single orifice Helmholtz resonator due to interaction between the grazing flow shear layer and the resonator cavity. Measurements showed that the tones radiated at a Strouhal number equal to 0.26. The effects of grazing flow on the impedance of Helmholtz resonators consisting of clusters of orifices was also studied. In general, both resistance and reaction were found to be virtually independent of orifice relative spacing and number. These findings are valid with and without grazing flow.

Hersch, A. S.↗

NASA NTRS1978

The vibrations of a cylindrical shell in a flowing acoustic media

A mathematical model is presented for the effect of flow on the vibrations of a thin cylindrical shell in a subsonically-flowing acoustic media. The effect of the external acoustic fluid consists of a mass-like term caused by the 'virtual-mass' effect of the fluid and a 'damping-like' term which accounts for the radiation of energy away from the cylinder. For a flowing medium, both of these terms are shown to involve the flow velocity. The effect of flow on the cylinder resonances is examined numerically. While not all modes are affected by the flow, there are some modes which are significantly affected. Usually, the added mass of the fluid increases with flow velocity causing a reduction in the resonant frequency of the shell mode.

Koval, L. R.↗

NASA NTRS1978

Some flow phenomena in a constant area duct with a Borda type inlet including the critical region

Mass limiting flow characteristics for a 55 L/D tube with a Borda type inlet have been assessed over large ranges of temperature and pressure using fluid nitrogen. Under certain conditions, separation and pressure drop at the inlet was sufficiently strong to permit partial vaporization and the remaining fluid flowed through the tube as if it were a free jet. An empirical relation was determined which defines conditions under which this type of flow can occur. A flow coefficient is presented which enables one to estimate flow rates over the experimental range. A flow rate stagnation pressure map for selected stagnation isotherms and pressure profiles document these flow phenomena.

Hendricks, R. C.↗

NASA NTRS1980

Viscous-inviscid calculations of jet entrainment effects on the subsonic flow over nozzle afterbodies

A viscous-inviscid interaction model was developed to account for jet entrainment effects in the prediction of the subsonic flow over nozzle afterbodies. The model is based on the concept of a weakly interacting shear layer in which the local streamline deflections due to entrainment are accounted for by a displacement-thickness type of correction to the inviscid plume boundary. The entire flow field is solved in an iterative manner to account for the effects on the inviscid external flow of the turbulent boundary layer, turbulent mixing and chemical reactions in the shear layer, and the inviscid jet exhaust flow. The components of the computational model are described, and numerical results are presented to illustrate the interactive effects of entrainment on the overall flow structure. The validity of the model is assessed by comparisons with data obtained form flow-field measurements on cold-air jet exhausts. Numerical results and experimental data are also given to show the entrainment effects on nozzle boattail drag under various jet exhaust and free-stream flow conditions.

Wilmoth, R. G.↗

NASA NTRS1980

Investigation of the flow field surrounding circular-arc boattail nozzles at subsonic speeds

The effects of jet exhaust on the subsonic flow field surrounding boattail nozzles with attached and separated boundary layers were investigated. Measurements of local Mach numbers and flow angles were made at free-stream Mach numbers of 0.60 and 0.80 at an angle of attack of 0 deg. Jet exhaust flow was simulated with a solid cylindrical sting and with high pressure air at jet-nozzle total pressure ratios of 2.9 and 5.0. Results show strong effects of the jet-wave structure on the external flow field. The predicted local Mach numbers and flow angles for attached-flow nozzles with solid jet simulators obtained by using subsonic inviscid/viscous-flow theory are in good agreement with experimental data. Prediction of nozzle surface pressure distributions which include jet-entrainment effects also agree with experimental data for attached-flow nozzles with high pressure air jets.

Abeyounis, W. K.↗

NASA NTRS1980

Space shuttle orbiter flow visualization study

The vortex flows generated at subsonic speed during the final portion of atmospheric reentry were defined using a 0.01 scale model of the orbiter in a diagnostic water tunnel. Flow visualization photographs were obtained over an angle-of-attack range to 40 deg and sideslip angles up to 10 deg. The vortex flow field development, vortex path, and vortex breakdown characteristics were determined as a function of angle-of-attack at zero sideslip. Vortex flows were found to develop on the highly swept glove, on the wing, and on the upper surface of the fuselage. No significant asymmetries were observed at zero sideslip in the water tunnel tests. The sensitivity of the upper surface vortex flow fields to variations in sideslip angle was also studied. The vortex formed on the glove remained very stable in position above the wing up through the 10 deg of sideslip tested. There was a change in the vortex lifts under sideslip due to effective change in leading-edge sweep angles. Asymmetric flow separation occurred on the upper surface of the fuselage at small sideslip angles. The influence of vortex flow fields in sideslip on the lateral/ directional characteristics of the orbiter is discussed.

Lorincz, D. J.↗

NASA NTRS1980

Investigations of eddy coherence in jet flows

In turbulent shear flow the term coherent structures refers to eddies which are both spatially coherent, i.e., large eddies, aand also temporally coherent, i.e., they retain their identities for times which are long compared with their time scales in fixed point measurements. In transitional flows, the existence of such structures is evident from flow visualizations. In many other flows, such structures are not so evident. The reasons for the existence of these two classes of flows are discussed and attention is focused upon the more difficult flows, where coherent structures are not so evident. Techniques by which the existence (or nonexistence) of such structures in these flows can be established from point measurements, are also discussed. A major problem is shown to be the need to discriminate between real losses in eddy coherence and apparent losses in coherence introduced by phase scrambling effects which 'smear' multipoint correlations. The analysis of multiprobe time dependent data in cold and reacting round turbulent jets is described and it is shown how evidence of strong eddy coherence can be extracted from data.

Yule, A. J.↗