Theoretical model studies of wave transmission in semicircular canal ducts
Semicircular canal ducts dynamic behavior, using mathematical model for wave transmission of elastic fluid-filled toroidal shell in rigid channel
Anliker, M.↗
SEARCH · Engineering Papers
Results for “ducts”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Study of magnetospheric field oriented irregularities - The mode theory of bell- shaped ducts
Whistler wave propagation along bell shaped ducts of enhanced ionization in magnetosphere
Scarabucci, R. R.↗
The calculation of optimal linings for jet engine inlet ducts
Optimal lining impedance for jet engine inlet duct, yielding discrete frequency, flow velocity and geometry on basis of minimum radiated power
Wilkinson, J. P. D.↗
Initial experience with two arc-heated duct facilities for studying orbital logistic vehicle thermal protection problems
Arc heated duct facilities providing high temperature supersonic turbulent boundary layer flows over large samples for orbital logistic vehicle thermal protection tests
Covington, M. A.↗
Effect of boundary layer on the transmission and attenuation of sound in an acoustically treated circular duct
Boundary layer effect on sound transmission in acoustically treated circular duct with shear flow, reducing governing equations to two-point boundary value problem
Eversman, W.↗
Theoretical and experimental analysis of acoustic linings for ducts with flow
Acoustic linings for attenuation of fan generated noise in turbofan engines, considering interaction between analytical lining performance prediction and flow duct testing
Armstrong, D.↗
Characteristics of magnetospheric ducts observed by the Alouette 2 topside sounder
Magnetospheric conjugate ducts characteristics for HF radio propagation from Alouette 2 topside sounder ionograms analysis
Ramasastry, J.↗
Transmission of spinning acoustic modes in a slightly non-uniform duct
Spinning acoustic modes transmission and backscatter in nonuniform long cylindrical ducts with throat
Tam, C. K. W.↗
Pressure losses for laminar flow in the entrance region of ducts of rectangular and equilateral triangular cross section.
The velocity profiles upon which the pressure-loss calculations are based, are recomputed using the previously described method of reference (1960). The pressure drop is then computed using the energy integral equation; both rectangular and equilateral triangular ducts are considered. It is demonstrated that, using this equation, the pressure-drop parameter can be improved.
Miller, R. W.↗
Effect of duct shape, Mach number, and lining construction on measured suppressor attenuation and comparison with theory
Noise attenuation was measured for several types of cylindrical suppressors that use a duct lining composed of honeycomb cells covered with a perforated plate. The experimental technique used gave attenuation data that were repeatable and free of noise floors and other sources of error. The suppressor length, the effective acoustic diameter, suppressor shape and flow velocity were varied. The agreement among the attenuation data and two widely used analytical models was generally satisfactory. Changes were also made in the construction of the acoustic lining to measure their effect on attenuation. One of these produced a very broadband muffler.
Olsen, W. A.↗
A generalized theory for the design of contraction cones and other low speed ducts
A generalization of the Tsien method of contraction cone design is described. The design velocity distribution is expressed in such a form that the required high order derivatives can be obtained by recursion rather than by numerical or analytic differentiation. The method is applicable to the design of diffusers and converging-diverging ducts as well as contraction cones. The computer program is described and a FORTRAN listing of the program is provided.
Barger, R. L.↗
Brayton cycle heat exchanger and duct assembly (HXDA, preliminary design and technology tests
A preliminary design of the heat exchanger and duct assembly (HXDA) for a 60 kwe, closed loop, Brayton cycle space power system is presented. This system is weight optimized within the constraints imposed by the defined structural and operational requirements. Also presented are the results of several small scale tests, directed to obtaining specific design data and/or the resolution of a design approach for long life Brayton cycle heat exchanger systems.
Coombs, M. G.↗
Terminal shock position and restart control of a Mach 2.7, two-dimensional, twin duct mixed compression inlet
Experimental results of terminal shock and restart control system tests of a two-dimensional, twin-duct mixed compression inlet are presented. High-response (110-Hz bandwidth) overboard bypass doors were used, both as the variable to control shock position and as the means of disturbing the inlet airflow. An inherent instability in inlet shock position resulted in noisy feedback signals and thus restricted the terminal shock position control performance that was achieved. Proportional-plus-integral type controllers using either throat exit static pressure or shock position sensor feedback gave adequate low-frequency control. The inlet restart control system kept the terminal shock control loop closed throughout the unstart-restart transient. The capability to restart the inlet was non limited by the inlet instability.
Cole, G. L.↗
The effects on cruise drag of installing long-duct refan-engine nacelles on the McDonnell Douglas DC-8-50 and -61
A high-speed wind tunnel test was conducted to determine the effect on cruise performance of installing long-duct refan-engine nacelles on the DC-8-50 and -61 models. Drag data and wing/pylon/nacelle channel pressure data are presented. At a typical cruise condition there exists a very small interference drag penalty of less than one-percent of total cruise data for the Refan installation. Pressure data indicate that some supersonic flow is present in the inboard channel of the inboard refan nacelle installation, but it is not sufficient to cause any wave drag on boundary layer separation. One pylon modification, which takes the form of pylon bumps, was tested. It resulted in a drag penalty, because its design goal of eliminating shock-related interference drag was not required and the bump thus became a source of additional parasite drag.
Callaghan, J. T.↗
Transmission of wave energy in curved ducts
A formation of wave energy flow was developed for motion in curved ducts. A parametric study over a range of frequencies determined the ability of circular bends to transmit energy for the case of perfectly rigid walls.
Rostafinski, W.↗
Zero leakage separable and semipermanent ducting joints
A study program has been conducted to explore new methods of achieving zero leakage, separable and semipermanent, ducting joints for space flight vehicles. The study consisted of a search of literature of existing zero leakage methods, the generation of concepts of new methods of achieving the desired zero leakage criteria and the development of detailed analysis and design of a selected concept. Other techniques of leak detection were explored with a view toward improving this area.
Mischel, H. T.↗
The design and development of an automatic control system for the in-duct cancellation of spinning modes of sound
The reduction is discussed of the discrete tones generated by jet engines which is essential for jet aircraft to meet present and proposed noise standards. The discrete tones generated by the blades and vanes propagate in the inlet and exhaust duct in the form of spiraling acoustic waves, or spinning modes. The reduction of these spinning modes by the cancellation effect of the combination of two acoustic fields was investigated. The spinning mode synthesizer provided the means for effective study of this noise reduction scheme. Two sets of electrical-acoustical transducers located in an equally-spaced circular array simultaneously generate a specified spinning mode and the cancelling mode. Analysis of the wave equation for the synthesizer established the optimum cancelling array acoustic parameters for maximum sound pressure level reduction. The parameter dependence of the frequency ranges of propagation of single, specified circumferential modes generated by a single array, and of effective cancellation of the modes generated by two arrays, was determined. Substantial sound pressure level reduction was obtained for modes within these limits.
Harrington, W. W.↗
A theoretical and experimental study of non-ducted VLF waves after propagation through the magnetosphere.
The nonducted propagation of artificial VLF waves through the magnetosphere has been studied by means of data obtained by the FR-1 satellite experiment, in which fixed frequency (16.8 kHz) waves radiated by a transmitter at the ground (at L equals 2.1) are received by the satellite, at 750 km altitude, both in the zone close to the transmitter and in the conjugate zone. From the wave-normal directions and Doppler shifts measured in the conjugate zone, it has been possible to identify waves that have been propagated from the Northern to the Southern Hemisphere in both ducted and nonducted modes. In this paper, the main features of the nonducted wave have been interpreted by ray tracing in models of the magnetosphere. The results improve our understanding as to why very few whistlers are observed on the ground at low latitudes.
Cerisier, J. C.↗