Engineering Papers⌕ Search

Engineering topics

Collins, D. J.

Publications and source records attributed to Collins, D. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Chapter 2: Optical Properties of the Water Column

In this chapter, and in chapter 29, the basic inter-relationship between the flux of radiant energy through the water column and the fixation of carbon by the phytoplankton in the ocean through processes of photosynthesis or primary production will be discussed.

photosynthesis↗
NASA NTRS1986

The Spacelab 2 superfluid helium experiment

An experiment to investigate the properties of superfluid helium in a microgravity environment flew on the Shuttle on the Spacelab 2 mission in July and August of 1985. This paper summarizes the flight experiment and describes the preliminary results. The experiment comprised an investigation of long-wavelength third-sound waves in micron-thick films, a study of the motions of superfluid helium under milli-g and micro-g accelerations, and measurements of the fluctuations in temperature associated with the small motions of the bulk helium. An additional accomplishment was to qualify and characterize a reflyable, space compatible cryostat.

Mason, P. V.↗
NASA NTRS1986

Preliminary results of the Spacelab 2 superfluid helium experiment

An experiment to investigate the properties of superfluid helium in a microgravity environment flew on the Shuttle on the Spacelab 2 mission in July and August of 1985. This paper summarizes the flight experiment and describes some preliminary results. The experiment comprised an investigation of long-wavelength third-sound waves in micron-thick films, a study of the motions of superfluid helium under milli-g and micro-g accelerations, and measurements of the fluctuations in temperature associated with the small motions of the bulk helium. An additional objective was to qualify and characterize a reflyable, space-compatible cryostat.

Mason, P. V.↗
NASA NTRS1985

The role of reabsorption in the spectral distribution of phytoplankton fluorescence emission

A theoretical model has been developed to describe an experimentally observed spectral shift in the fluorescence emission from phytoplankton as a result of the internal reabsorption of that emission. This model accounts for both the absorption of the primary excitation and the modification of the fluorescence through the reabsorption of the emitted light by the chloroplast and by the surrounding medium. Comparisons are made between the results of the theoretical model and data derived from experiments using a number of different phytoplankton species, each adapted to varying light conditions. The details of the model are discussed, and the consequences of its interpretation on the spectral distribution of the fluorescence emission from phytoplankton are examined.

Collins, D. J.↗
NASA NTRS1984

Recent progress in the measurement of temperature and salinity by optical scattering

Recent progress is described in the use of Brillouin and Raman scattering for the measurement of temperature and salinity in the ocean. The use of Brillouin scattering is described for the measurement of the sound velocity, and the use of Raman scattering is described for the independent measurement of the temperature and salinity. Coupling these techniques permits the assessment of both temperature and salinity. The experimental techniques are described together with the results of recent experiments and an assessment of the errors to be expected.

Collins, D. J.↗
NASA NTRS1982

LIDAR and acoustics applications to ocean productivity

The requirements for the submersible, the instrumentation necessary to perform these measurements, and the optical and acoustical technology required to develop the ocean color scanner instrumentation are described. The development of a second generation ocean color scanner produced the need for coincident in situ scientific measurements which examine the primary productivity of the upper ocean on time and space scales which are large compared to the environmental scales. The vertical and horizontal variability of the biota, including the relationship between chlorophyll and primary productivity, the productivity of zooplankton, and the dynamic interaction between phytoplankton and zooplankton, and between these populations and the physical environment are investigated. A towed submersible will be constructed which accommodates both an underwater LIDAR instrument and a multifrequency sonar.

Collins, D. J.↗
NASA NTRS1979

Measurements in the Turbulent Boundary Layer at Constant Pressure in Subsonic and Supersonic Flow. Part 2: Laser-Doppler Velocity Measurements

A description of both the mean and the fluctuating components of the flow, and of the Reynolds stress as observed using a dual forward scattering laser-Doppler velocimeter is presented. A detailed description of the instrument and of the data analysis techniques were included in order to fully document the data. A detailed comparison was made between the laser-Doppler results and those presented in Part 1, and an assessment was made of the ability of the laser-Doppler velocimeter to measure the details of the flows involved.

Dimotakis, P. E.↗
NASA NTRS1979

Laser Doppler velocity measurements in subsonic, transonic, and supersonic turbulent boundary layers

Recent measurements have used laser Doppler velocimetry to make direct measurements of the Reynolds stress in turbulent boundary layers in the Mach number range 1.5 to 3.0. A serious anomaly, however, is exhibited in these measurements in that the maximum of -u-prime v-prime occurs much farther from the wall than is reasonable for flow at constant pressure. The purpose of the present experiments was to obtain redundant data over a substantial range of Mach numbers (0.1-2.2) in an effort to resolve the anomaly in turbulent shearing stress.

Dimotakis, P. E.↗
NASA NTRS1978

Measurements in the turbulent boundary layer at constant pressure in subsonic and supersonic flow. Part 1: Mean flow

Experiments were carried out to test the accuracy of laser Doppler instrumentation for measurement of Reynolds stresses in turbulent boundary layers in supersonic flow. Two facilities were used to study flow at constant pressure. In one facility, data were obtained on a flat plate at M sub e = 0.1, with Re theta up to 8,000. In the other, data were obtained on an adiabatic nozzle wall at M sub e = 0.6, 0.8, 1.0, 1.3, and 2.2, with Re theta = 23,000 and 40,000. The mean flow as observed using Pitot tube, Preston tube, and floating element instrumentation is described. Emphasis is on the use of similarity laws with Van Driest scaling and on the inference of the shearing stress profile and the normal velocity component from the equations of mean motion. The experimental data are tabulated.

Collins, D. J.↗
NASA NTRS1974

Laminar viscous-inviscid interactions at transonic speeds

Some aspects of the laminar viscous-inviscid interaction at transonic speeds are discussed by examining data obtained on a 6% thick biconvex circular-arc airfoil and comparing the results with the predictions of Klineberg and Steger (1972). The results obtained from experiments are compared for Re = 140,000 and for Re = 40,000. It is clear that the theoretical results overestimate the effects of viscosity and consequently predict values for the pressure coefficient which lie below the experimental data over the range of Mach numbers given.

Collins, D. J.↗
NASA NTRS1973

An inexpensive technique for the fabrication of two-dimensional wind tunnel models.

Description of a new and inexpensive method for fabricating thin, two-dimensional, spanwise-uniform airfoil models with a high density of instrumentation for aerodynamic testing at transonic speeds. The models are produced by casting an epoxy fairing, which provides the desired aerodynamic properties, around a central spar on which all instrumentation has been mounted.

Collins, D. J.↗
NASA NTRS1973

Experimental and theoretical investigations in two-dimensional transonic flow.

Experimental and theoretical results are presented from a study of the flow over a family of transonically scaled circular-arc bodies mounted in a solid-wall wind tunnel. Data are presented for Reynolds numbers between 30,000 and 3,600,000, based on chord. The high Reynolds number results are compared with computations based on inviscid theory, and are used to investigate transonic similarity and the behavior of the flow near choking. The results at low Reynolds number are used to demonstrate the effect of viscosity on the overall flowfield, and comparisons are made with existing laminar viscous/inviscid interaction theory.

Collins, D. J.↗