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  • Other Sources  (15)
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  • 1
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    Investigations of scaling laws for jet impingement (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The statistical properties of tangential flows over surfaces were investigated by two techniques. In one, a laser-Doppler velocimeter was used in a smoke-laden jet to measure one-point statistical properties, including mean velocities, turbulent intensities, intermittencies, autocorrelations, and power spectral densities. In the other technique, free stream and surface pressure probes connected to 1/8 inch microphones were used to obtain single point rms and 1/3 octave pressures, as well as two point cross correlations, the latter being converted to auto spectra, amplitude ratios, phase lags, and coherences. The results of these studies support the vortex model of jets, give some insights into the effects of surface impingement, and confirm that jet diameter and velocity are the scaling parameters for circular jets, while Reynolds number is relatively unimportant.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 445-463
    Format: application/pdf
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  • 2
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    Turbulent two-dimensional jet flow and its effect on laser beam degradation (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An experiment in which visible wavelength lasers traversed a well-documented two dimensional jet was conducted. Temperature perturbations varied from 0.25 to 1.80 K and velocity fluctuations ranged from 9.2 to 30.8 m/sec. Measured central spot intensities were as low as 18% of the undisturbed beam, depending on jet Mach number, beam position theory and experiment was two percent in terms of far field intensity. To supplement the flow field information, a laser Doppler velocimeter was developed to measure both mean and fluctuating velocities and a photo correlator was used as a signal processor.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 1-33
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  • 3
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    An experimental investigation of an axisymmetric jet in a coflowing airstream (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The flow development of an axisymmetric jet exhausting into a moving airstream has been studied. The jet has a Reynolds number of 22,600, and the ratio of the jet velocity to the wind tunnel velocity is 5.1 to 1. The flow field of the axisymmetric jet was examined at locations varying from approximately zero to eight diameters downstream of the orifice. Of primary concern at each downstream location was the mapping of the one point statistical properties of the flow, including mean velocity, turbulent intensity, and intermittency. Autocorrelations and power spectral density curves were determined for both the fluctuating velocity field and the concentration signal at various distances from the jet's center line for different downstream locations. A laser Doppler velocimeter, using a phase locked loop processor, was used to make the desired velocity field measurements which were compared with hot wire anemometer and pressure probe data.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-143104 , ESS-4043-106-75-REV
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  • 4
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    Pressure and velocity measurements in a three dimensional wall jet (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A flat plate and a curved wall surface, intended to model a wing-flap combination in a high V/STOL configuration, were used to measure pressure and flow velocity in a freely expanding coflowing jet and a three dimensional wall jet. The effects of increasing the velocity ratio of the jet exit plane velocity to the free stream velocity were investigated. Velocity measurements were made using a two color laser Doppler velocimeter with a phase-locked loop processor. Fluctuating pressures were monitored with condenser-type microphones. Quantities measured include the width of the mixing region, the mean velocity field, turbulent intensities, and time scales. Wall and static pressure-velocity correlations and coherences are presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-157918
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  • 5
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    The deflection of a jet by confining surfaces (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Thrust vectoring can be provided by the turning of a jet exhaust by the presence of confining surfaces. This approach is analogous to the upper surface blowing (USB) concept. Mean velocities, velocity autocorrelations, and pressure-velocity correlations are measured. From the autocorrelation curves, the Taylor microscales and the integral length scales are calculated. Convection velocities are calculated from the velocity space-time correlations. Two different confining surfaces (one flat, one with large curvature) are placed adjacent to the lip of a circular nozzle, and the resultant effects on the flow field are determined. In addition, two velocity ratios (exit plane velocity to ambient stream velocity) are examined. The velocity measurements were made with a laser Doppler velocimeter in conjunction with a phase locked-loop processor. Pressure measurements were made using a 1/8th inch condensor type microphone.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: APL The 1981 JANNAF Propulsion Meeting, Vol 2; p 49-66
    Format: text
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  • 6
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    An experimental investigation of a three-dimensional wall jet (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: An experimental investigation of the effects of a curved and flat wall surface on the flow development of an axisymmetric jet exhausting into a moving airstream has been made. Of primary concern was the comparison of the one-point statistical properties of the unconfined jet to the quantities measured in the flows over a flat plate and a curved wall surface. Quantities measured in this investigation included mean velocities in all three directions, turbulent intensities, autocorrelations, power spectral densities, and intermittencies. The investigation was confined to the near field of the turbulent jet. The curved wall (flap) was found to have a very large effect on both the mean velocity and the turbulent velocity components of the flowfield. The potential core region of the jet was found to break up most rapidly for the flow over the flap. A laser-Doppler velocimeter, using a phase locked-loop processor, was used to make the desired velocity field measurements. To determine the intermittency profiles, a laser light scattering technique was employed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 15; Aug. 197
    Format: text
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  • 7
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    Unsteady loads due to propulsive lift configurations (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The flow of a jet over an airfoil representative of upper surface blowing was studied using laser techniques. Experimental techniques were developed for the investigation of unsteady pressures behind a cold model jet. Construction of a 1/4 scale model of the 'Beach' test configuration was completed along with construction of a portable detector. The portable detector is used in conjunction with a laser to measure jet flows during tests on the 'Beach' facility. The detector incorporates both optical and electronic components.
    Keywords: AERODYNAMICS
    Type: NASA-CR-143454 , ESS-4043-108-75 , QPR-7
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  • 8
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    Unsteady loads due to propulsive lift configurations. Part B: Pressure and velocity measurements in a three dimensional wall jet (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of increasing the velocity ratio, lambda sub j were explored. The quantities measured include the width of the mixing region, the mean velocity field, turbulent intensities and time scales. In addition, wall and static pressure velocity correlations and coherences are presented. The velocity measurements were made using a laser Doppler velocimeter with a phase locked loop processor. The fluctuating pressures were monitored using condenser type microphones.
    Keywords: AERODYNAMICS
    Type: NASA-CR-156121 , UVA/526033/MAE78/101-PT-B , UVA/528095/MAE78/115-PT-B
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  • 9
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    Measurements in the mixing region of a turbulent jet in a coflowing airstream (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The mixing region of a turbulent jet is an important example of an intermittent turbulent shear flow. There are a great deal of interest in this region because of interest in jet noise and STOL aircraft which use upper surface blowing or externally blown flap configurations to increase lift. A detailed study of the one point statistical properties of a smoke laden jet was made using a combination of a laser velocimeter and a light scattering system. The jet, with a 14 to 1 contraction, was placed inside a wind tunnel where the ratio of the jet exit velocity to free stream was 5.1 to 1. All measurements are made for a jet Reynolds number of 22,600. Among the quantities measured are mean axial and radial velocities, axial and radial intensities, power spectra, mean smoke concentration, concentration intensities, concentration spectra, intermittencies and velocity-concentration correlations. The results are compared with hot-wire data where available.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Inst. Franco-Allemend de Rech. de Saint-Louis Proc. of the ISL(AGARD Workshop on Laser Anemometry; p 269-297
    Format: text
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  • 10
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    Some two-point statistical properties of a three-dimensional wall jet (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The effects of both a straight and a curved wall on the two-point space-time velocity correlations of a turbulent jet are documented. From the correlations, isocorrelation contours are constructed which allow a picture of the various flow patterns to be determined. Autoand cross-correlations of the fluctuating concentration field are also obtained for the different flow configurations. The confining surfaces served to radically change the flow pattern for the freely expanding turbulent jet. The velocity measurements are made with a laser Doppler velocimeter in conjunction with a phase locked-loop processor, while the concentration field is monitored with a laser light-scattering technique.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 16; July 197
    Format: text
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