15,584 research outputs found
A geometry package for generation of input data for a three-dimensional potential-flow program
The preparation of geometric data for input to three-dimensional potential flow programs was automated and simplified by a geometry package incorporated into the NASA Langley version of the 3-D lifting potential flow program. Input to the computer program for the geometry package consists of a very sparse set of coordinate data, often with an order of magnitude of fewer points than required for the actual potential flow calculations. Isolated components, such as wings, fuselages, etc. are paneled automatically, using one of several possible element distribution algorithms. Curves of intersection between components are calculated, using a hybrid curve-fit/surface-fit approach. Intersecting components are repaneled so that adjacent elements on either side of the intersection curves line up in a satisfactory manner for the potential-flow calculations. Many cases may be run completely (from input, through the geometry package, and through the flow calculations) without interruption. Use of the package significantly reduces the time and expense involved in making three-dimensional potential flow calculations
Calculation of compressible flow in and about three-dimensional inlets with and without auxiliary inlets by a higher-order panel method
A three dimensional higher order panel method was specialized to the case of inlets with auxiliary inlets. The resulting program has a number of graphical input-output features to make it highly useful to the designer. The various aspects of the program are described instructions for its use are presented
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Volumetric velocimetry study in a transitional wall jet flow with passive flow control via flaps
Birds are remarkably good flyers and show very special adaptations in their wings for stall delay. The pop-up of some cover feathers during starting and landing gave the idea for the present study to investigate the influence on a wall jet when inserting an array with flaps made of elastomer foil. In a wall jet with Re = 420 a flat plate and two different flap arrays (with a foil thickness of 100 and 200 µm) are measured by a time resolved 3D scanning PIV with 20 laser sheets. 2-dimensional analyses show the forming rolers between the jet flow and the surrounding fluid with a fundamental frequency of 13-14 Hz and the characteristically vortex pairing. By inserting the flap array the jet wallnormal spreading gets intensified and the vortex interaction process results in cooperative formation of larger vortices. The 3-dimensional analyses verify these results and show high 3-dimensional vortical structures which are growing when passing over a flap array. In case of the inserted flap array the vortex pairing process was delayed and accumulation of spanwise vorticity was forced to happen over the first rows of flaps, thus forming the larger structures. Already the used flap array configurations showed a significant impact influence on the jet evolution and the non-linear instabilities. Further investigations will analyze the influence of more parameters as the flap geometry or the distance to the jet flow and nozzle outlet
An Isotopic analysis of the hydrology and riparian vegetation water sources on Bishop Creek
Five power generation plants along an eleven kilometer stretch divert Bishop Creek water for hydro-electric power. Stream diversion may be adversely affecting the riparian vegetation. Stable isotopic analysis is employed to determine surface water/ground-water interactions along the creek. surface water originates primarily from three headwater lakes. Discharge into Bishop Creek below the headwaters is primarily derived from ground water. The average δD and δ18O values are significantly different for surface water and ground water that an isotopic analysis can delineate between these two components of flow. Therefore isotopic shifts along the creek can determine gaining reaches. In addition, by knowing the isotopic signatures of various waters in the watershed, it may be possible to examine tree waters to determine their water source(s)
Investigation of the potentialities of photochemical laser systems. Part I - Survey and analysis Final report, 1 Feb. 1966 - 31 Jan. 1967
Photodissociative laser systems used to convert solar radiation to monochromatic coherent emission - excitation mechanisms, spectroscopy of gases absorbing light, and chemical processe
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Seasonal changes in the transport of pollutants into the Arctic troposphere-model study
Turbojet blade vibration data acquisition design and feasibility testing
A turbojet blade vibration data acquisition system was designed to allow the measurement of blade vibration. The data acquisition system utilizing 96 microprocessors to gather data from optical probes, store, sort and transmit to the central computer is described. Areas of high technical risk were identified and a two-microprocessor system was breadboarded and tested to investigate these areas. Results show that the system was feasible and that low technical risk would be involved in proceeding with the complete system fabrication
Passive propellant system
The system utilizes a spherical tank structure A separated into two equal volume compartments by a flat bulkhead B. Each compartment has four similar gallery channel legs located in the principal vehicle axes, ensuring that bulk propellant will contact at least one gallery leg during vehicle maneuvers. The forward compartment gallery channel legs collect propellant and feed it into the aft compartment through communication screens which protrude into the aft compartment. The propellant is then collected by the screened gallery channels in the aft compartment and supplied to the propellant outlet. The invention resides in the independent gallery assembly and screen structure by means of which propellant flow from forward to aft compartments is maintained. Liquid surface tension of the liquid on the screens is used to control liquid flow. The system provides gas-free propellants in low or zero-g environments regardless of axial accelerations and propellant orientation in bulk regions of the vessel
Calculation of compressible flow about three-dimensional inlets with auxiliary inlets, slats and vanes by means of a panel method
An efficient and user oriented method was constructed for calculating flow in and about complex inlet configurations. Efficiency is attained by: (1) the use of a panel method; (2) a technique of superposition for obtaining solutions at any inlet operating condition; and (3) employment of an advanced matrix iteration technique for solving large full systems of equations, including the nonlinear equations for the Kutta condition. User concerns are addressed by the provision of several novel graphical output options that yield a more complete comprehension of the flowfield than was possible previously
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