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Johnson, B. V.

Publications and source records attributed to Johnson, B. V..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Mass and Momentum Transport Experiments with Swirling Flow

An experimental study of mixing downstream of axial and swirling coaxial jets is being conducted to obtain data for the evaluation and improvement of turbulent transport models currently employed in a variety of computational procedures used throughout the propulsion community. The axial coaxial jet study was completed under Phase 1. The swirling coaxial jet study, which is the subject of this paper, was conducted under Phase 2 of the contract. A TEACH code was acquired, checked out for several test cases, and is reported. A study to measure length scales and to obtain a limited number of measurements with a blunt trailing edge inlet is being conducted under Phase 3 of the contract.

Johnson, B. V.↗
NASA NTRS1984

Mass and momentum turbulent transport experiments with confined coaxial jets

An experimental study of mixing downstream of coaxial jets discharging into an expanded circular duct was conducted to obtain data for the evaluation and improvement of turbulent transport models. A combination of turbulent momentum transport rate and two components of velocity data were obtained from simultaneous measurements with a two-color LV system. A combination of turbulent mass transport rate, concentration and velocity data were obtained from simultaneous measurements with laser velocimeter (LV) and laser induced fluorescence (LIF) systems.

Johnson, B. V.↗
NASA NTRS1984

Scalar and momentum turbulent transport experiments with swirling and nonswirling flows

Combustor models for the aircraft gas turbine industry have been obtained because of the need to reduce the costs of developing improved performance and more durable engines. A few years ago, it became apparent that the mass concentration and velocity predictions provided by the computer codes were not representing the data measured in some confined recirculating flows. It is pointed out that errors in the mass concentration distribution are an especially serious problem because of their influence on the heat release, temperature, and reactant distributions. Combined mass and momentum turbulent transport experiments with swirling and nonswirling flow have been conducted with the objective to obtain an experimental data base which can be used to evaluate and improve the turbulent transport submodes employed in the aerothermal models. The present paper is mainly concerned with the overall characteristics of the mass turbulent transport processes in complex flows with recirculation and the deficiencies of the conventional models.

Johnson, B. V.↗
NASA NTRS1983

Mass and momentum turbulent transport experiments with confined swirling coaxial jets

Swirling coaxial jets mixing downstream, discharging into an expanded duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used in a variety of computational procedures throughout the combustion community. A combination of laser velocimeter (LV) and laser induced fluorescence (LIF) techniques was employed to obtain mean and fluctuating velocity and concentration distributions which were used to derive mass and momentum turbulent transport parameters currently incorporated into various combustor flow models. Flow visualization techniques were also employed to determine qualitatively the time dependent characteristics of the flow and the scale of turbulence. The results of these measurements indicated that the largest momentum turbulent transport was in the r-z plane. Peak momentum turbulent transport rates were approximately the same as those for the nonswirling flow condition. The mass turbulent transport process for swirling flow was complicated. Mixing occurred in several steps of axial and radial mass transport and was coupled with a large radial mean convective flux. Mixing for swirling flow was completed in one-third the length required for nonswirling flow.

Roback, R.↗
NASA NTRS1983

Mass and Momentum Turbulent Transport Experiments

The downstream mixing of coaxial jets discharging in an expanded duct was studied to improve turbulent transport models which are used in computational procedures throughout the propulsion community for combustor flow modeling. Laser velocimeter (LV) and laser induced fluorescence (LIF) techniques were used to measure velocities and concentration and flow visualization techniques to determine the time dependent characteristics of the flow and the scale of the turbulent structure.

Johnson, B. V.↗
NASA NTRS1983

Statistical characteristics of velocity, concentration, mass transport, and momentum transport for coaxial jet mixing in a confined duct

An experimental study of mixing downstream of coaxial jets discharging into an expanded circular duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used for combustor flow modeling. A combination of turbulent momentum transport rate and two velocity component data was obtained from simultaneous measurements with a two-color LV system. A combination of turbulent mass transport rate, concentration and velocity data was obtained from simultaneous measurements with laser velocimeter (LV) and laser induced fluorescence (LIF) systems. These measurements were used to obtain mean, second central moment, skewness and kurtosis values for three velocity components and the concentration. These measurements showed the existence of countergradient turbulent axial mass transport where the annular jet fluid was accelerating the inner jet fluid. Results from the study are related to the assumptions employed in the current mass and momentum turbulent transport models.

Johnson, B. V.↗
NASA NTRS1981

Mass and Momentum Turbulent Transport Experiments with Confined Coaxial Jets

Downstream mixing of coaxial jets discharging in an expanded duct was studied to obtain data for the evaluation and improvement of turbulent transport models currently used in a variety of computational procedures throughout the propulsion community for combustor flow modeling. Flow visualization studies showed four major shear regions occurring; a wake region immediately downstream of the inlet jet inlet duct; a shear region further downstream between the inner and annular jets; a recirculation zone; and a reattachment zone. A combination of turbulent momentum transport rate and two velocity component data were obtained from simultaneous measurements with a two color laser velocimeter (LV) system. Axial, radial and azimuthal velocities and turbulent momentum transport rate measurements in the r-z and r-theta planes were used to determine the mean value, second central moment (or rms fluctuation from mean), skewness and kurtosis for each data set probability density function (p.d.f.). A combination of turbulent mass transport rate, concentration and velocity data were obtained system. Velocity and mass transport in all three directions as well as concentration distributions were used to obtain the mean, second central moments, skewness and kurtosis for each p.d.f. These LV/LIF measurements also exposed the existence of a large region of countergradient turbulent axial mass transport in the region where the annular jet fluid was accelerating the inner jet fluid.

Johnson, B. V.↗
NASA NTRS1973

Noise and wake structure measurements in a subsonic tip speed fan

The results of an experimental program are reported which show the effect of blade angle, tip speed, fan pressure ratio, and thrust on noise of a model fan of 0.457m (18 inches) diameter operating at subsonic tip speeds at pressure ratios between 1.06 and 1.15. The fan used in this study had 12 blades, 7 stator vanes, and a spacing between the rotor and stator of 1.85 blade chords. This fan was originally designed for aerodynamic testing and was considered a good performer. It was used in the noise test program as it incorporated features found to reduce noise in an earlier analytical parametric study. For a given pressure ratio the fan was shown to exhibit minimum noise at the blade angle and tip speed near that of maximum aerodynamic efficiency. Also, the noise level and spectrum character of this fan showed excellent correlation with scaled data of a similar larger diameter fan. Results of the program confirm the trends shown in the earlier analytical parametric study which showed that fan noise could be reduced for a given thrust and pressure ratio by increasing fan solidity, improving fan aerodynamic design, and operating the fan at an optimum subsonic tip speed. In addition to noise, the blade wake characteristics at the leading edge of the stator were measured in this program. At root and tip sections some difference between predicted and measured wakes was found. However comparisons between predicted and measured wakes at mid span locations was found to be good.

Magliozzi, B.↗
NASA NTRS1973

Experimental and analytical study of one- and two-component flows in spherical chambers

A study was conducted to evaluate techniques for obtaining high inner-gas concentrations in a spherical cavity for application to the open-cycle gaseous-core nuclear rocket. The study included flow visualization tests with water and gases as the working fluids, calculations of the streamline distribution, and calculation and measurement of the inner-gas concentration with air and Freon-11 as the inner-stream gases. The cavity shape, the outer-stream injection conditions, the turbulent transport coefficients, and the buoyancy effects were found to affect the inner-stream flow patterns.

Johnson, B. V.↗
NASA NTRS1973

Noise and wake structure measurements in a subsonic tip speed fan: Tabulation and plots of test data

Noise and wake structure measurements in a ducted fan were conducted. The tip speed was kept at subsonic levels. The anechoic platform used during the test is described. The following conditions are reported: (1) one third octave band analyses of the fan noise data, (2) narrow band analyses of the fan noise for selected test conditions, (3) narrow band sound power level data for all fan test conditions, and (4) velocity and air angle evaluation of blade wake data.

Magliozzi, B.↗
NASA NTRS1972

Exploratory study of the effects of injection configurations and inlet flow conditions on the characteristics of flow in spherical chambers

Flow visualization studies were conducted to evaluate techniques for injecting simulated-fuel and simulated-propellant gases into a spherical cavity for application to open-cycle gaseous-core nuclear rockets. Preliminary studies were conducted with six simulated-fuel injectors and eight simulated-propellant injection configurations. Additional tests were conducted with the best configuration to determine the effect of weight-flow ratio, gas density ratio, injector location, and flow distribution on the simulated-fuel containment characteristics.

Johnson, B. V.↗
NASA NTRS1971

Experimental study of the effects of injection conditions on the flow in cylindrical and spherical chambers.

Fluid mechanics experiments were performed in cylindrical and spherical chambers to evaluate the simulated-fuel containment resulting from various injection geometry and inlet flow conditions for application to the open-cycle GNR. A preliminary study in the cylindrical chamber was directed toward developing inlet flow conditions which minimize mixing between the simulated fuel and propellant. Gas concentration measurements were obtained at several outer-stream to inner-stream weight flow and density ratios for the best inlet configuration tested in the preliminary study. The spherical cavity flow study was conducted to evaluate techniques for injecting simulated-fuel and propellant into a cavity.

Johnson, B. V.↗