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Robinson, A. C.

Publications and source records attributed to Robinson, A. C..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Three-dimensional stability of an elliptical vortex in a straining field

The three-dimensional linear stability of a rectilinear vortex of elliptical cross-section existing as a steady state in an irrotational straining field is studied numerically in the case of finite strain. It is shown that the instability predicted analytically for weak strain persists for finite strain and that the weak-strain results continue to be quantitatively valid for finite strain. The dependence of the growth rates of the unstable modes on the strain and the axial-disturbance wavelength is discussed. It is also shown that a three-dimensional instability is always more unstable than a two-dimensional instability in the range of parameters of most interest.

Robinson, A. C.↗
NASA NTRS1984

Stability and structure of stretched vortices

The linear stability of the symmetric Burgers vortex to a class of two-dimensional perturbations is demonstrated. The linear stability of the axially symmetric Burgers vortex to two-dimensional low-Reynolds number disturbances is first discussed. The analysis describes the connection of the normal modes with a classical set of special functions. An expansion in Reynolds number gives the variation of the temporal eigenvalues of the normal modes. Then, Burgers-type solutions are sought where the radially inward-straining field is not axially symmetric. A rational perturbation procedure is used to obtain a new class of nonsymmetric Burgers vortices valid when the Reynolds number and the asymmetry in the external strain are small. Finally, the perturbation solutions are numerically extended to larger values of the parameters.

Robinson, A. C.↗
NASA NTRS1982

Three-dimensional stability of vortex arrays

The stability to three-dimensional disturbances of three classical steady vortex configurations in an incompressible inviscid fluid is studied in the limit of small vortex cross-sectional area and long axial disturbance wavelength. The configurations examined are the single infinite vortex row, the Karman vortex street of staggered vortices and the symmetric vortex street. It is shown that the single row is most unstable to a two-dimensional disturbance, while the Karman vortex street is most unstable to a three-dimensional disturbance over a significant range of street spacing ratios. The symmetric vortex street is found to be most unstable to three-dimensional or two-dimensional symmetric disturbances depending on the spacing ratio of the street. Short remarks are made concerning the relevance of the calculations to the observed instabilities in free shear layer, wake and boundary-layer type flows.

Robinson, A. C.↗
NASA NTRS1981

Comparative analysis of techniques for evaluating the effectiveness of aircraft computing systems

Performability analysis is a technique developed for evaluating the effectiveness of fault-tolerant computing systems in multiphase missions. Performability was evaluated for its accuracy, practical usefulness, and relative cost. The evaluation was performed by applying performability and the fault tree method to a set of sample problems ranging from simple to moderately complex. The problems involved as many as five outcomes, two to five mission phases, permanent faults, and some functional dependencies. Transient faults and software errors were not considered. A different analyst was responsible for each technique. Significantly more time and effort were required to learn performability analysis than the fault tree method. Performability is inherently as accurate as fault tree analysis. For the sample problems, fault trees were more practical and less time consuming to apply, while performability required less ingenuity and was more checkable. Performability offers some advantages for evaluating very complex problems.

Hitt, E. F.↗
NASA NTRS1979

SEASAT demonstration experiments with the offshore oil, gas and mining industries

Despite its failure, SEASAT-1 acquired a reasonable volume of data that can be used by industrial participants on a non-real-time basis to prove the concept of microwave sensing of the world's oceans from a satellite platform. The amended version of 8 experimental plans are presented, along with a description of the satellite, its instruments, and the data available. Case studies are summarized for the following experiments: (1) Beaufort Sea oil, gas, and Arctic operations; (2) Labrador Sea oil, gas, and sea ice; (3) Gulf of Mexico pipelines; (4) U.S. East Coast offshore oil and gas; (5) worldwide offshore drilling and production operations; (6) Equatorial East Pacific Ocean mining; (7) Bering Sea ice project; and (8) North Sea oil and gas.

Mourad, A. G.↗
NASA NTRS1977

Review of current interest and research in water hyacinth-based wastewater treatment

The status of activity in the user community for water hyacinth-based wastewater treatment was evaluated. The principal technique used was that of interviewing people who either (1) were known to be engaged in hyacinth research or development or (2) had made inquiry to NASA about hyacinth systems. About 40 non-research organizations and a similar number of research organizations were contacted. As a result of the interviews and a review of the relevant literature, it was concluded that hyacinth systems have the potential for providing a lower cost way for small cities to meet increasingly stringent effluent requirements. A limited amount of full-scale demonstration of hyacinth systems has been carried out during the past two years, but the yield of design data has been small. Several organizations are currently planning construction of experimental full-scale hyacinth-based wastewater treatment systems during 1977-1978.

Markarian, R. K.↗
NASA NTRS1977

Applications of Seasat to the offshore oil, gas and mining industries

The NASA satellite Seasat-A (to be launched in 1978) has applications to the offshore oil, gas, and mining industries including: (1) improvements in weather and wave forecasting, (2) studies of past wind and wave statistics for planning design requirements, and (3) monitoring ice formation, breakup, and movement in arctic regions. The primary geographic areas which will be monitored by Seasat-A include: the Beaufort Sea, the Labrador Sea, the Gulf of Mexico, the U.S. east coast, West Africa, Equatorial East Pacific, the Gulf of Alaska, and the North Sea. Seasat-A instrumentation used in ocean monitoring consists of a radar altimeter, a radar scatterometer, a synthetic aperture radar, a microwave radiometer, and a visible and infrared radiometer. The future outlook of the Seasat program is planned in three phases: measurement feasibility demonstration (1978-1980), data accessibility/utility demonstration (1980-1983), and operational system demonstration (1983-1985).

Mourad, A. G.↗
NASA NTRS1976

Options for organization and operation of space applications transfer centers

The benefits of developing regional facilities for transfer of NASA developed technology are discussed. These centers are designed to inform, persuade, and serve users. Included will be equipment for applications and demonstrations of the processes, a library, training facilities, and meeting rooms. The staff will include experts in the various techniques, as well as personnel involved in finding and persuading potential users.

Robinson, A. C.↗
NASA NTRS1976

An analysis of the market potential of water hyacinth-based systems for municipal wastewater treatment

The potential U.S. market for tertiary municipal wastewater treatment facilities which make use of water hyacinths was investigated. A baseline design was developed which approximates the "typical" or "average" situation under which hyacinth-based systems can be used. The total market size for tertiary treatment was then estimated for those geographical regions in which hyacinths appear to be applicable. Market penetration of the baseline hyacinth system when competing with conventional chemical and physical processing systems was approximated, based primarily on cost differences. A limited analysis was made of the sensitivity of market penetration to individual changes in these assumptions.

Robinson, A. C.↗
NASA NTRS1971

A proposed criterion for aircraft flight in turbulence

A proposed criterion for aircraft flight in turbulent conditions is presented. Subjects discussed are: (1) the problem of flight safety in turbulence, (2) new criterion for turbulence flight where existing ones seem adequate, and (3) computational problems associated with new criterion. Primary emphasis is placed on catastrophic occurrences in subsonic cruise with the aircraft under automatic control. A Monte Carlo simulation is used in the formulation and evaluation of probabilities of survival of an encounter with turbulence.

Porter, R. F.↗