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  • 1
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    A numerical and experimental investigation of electrothermal aircraft deicing (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Experimental data were obtained for the deicing characteristics of a stationary UH-1H helicopter blade which had been fitted with an electrothermal deicer assembly. The tests were run in the NASA Lewis Icing Research Tunnel, and yielded transient temperature responses for the substrate, heater and abrasion shield at selected positions around the blade. The data at the abrasion shield-ice interface clearly documented when melting, shedding or refreezing occurred. Comparisons were made between the experimental data and a one-dimensional numerical model. The agreement was generally very good, with the simulations being shown to be capable of predicting the transient temperature responses along with phase change and ice shedding. At many blade positions, the model was capable of accurately simulating the thermal response of the electrothermal deicer assembly.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Format: text
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  • 2
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    Effect of type and location of oil groove on the performance of journal bearings (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A numerical study is performed of oil groove type (circumferential and axial), groove number (single and double) and groove location on journal bearing performance. The analysis involves the use of a cavitation algorithm. The interaction between cavitation phenomena and grooving is determined. Quantitative information is provided which will aid designers to better locate oil feed grooves.
    Keywords: MECHANICAL ENGINEERING
    Type: STLE Tribology Transactions (ISSN 0569-8197); 35; 98-106
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  • 3
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    An LDA (Laser-Doppler Anemometry) investigation of three-dimensional normal shock wave boundary-layer interactions (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Nonintrusive measurements were made of a normal shock wave/boundary layer interaction. Two dimensional measurements were made throughout the interaction region while 3-D measurements were made in the vicinity of the shock wave. The measurements were made in the corner of the test section of a continuous supersonic wind tunnel in which a normal shock wave had been stabilized. Laser Doppler Anemometry, surface pressure measurement and flow visualization techniques were employed for two freestream Mach number test cases: 1.6 and 1.3. The former contained separated flow regions and a system of shock waves. The latter was found to be far less complicated. The results define the flow field structure in detail for each case.
    Keywords: AERODYNAMICS
    Type: NASA, Langley Research Center, Transonic Symposium: Theory, Application, and Experiment, Volume 1, Part 2; p 741-764
    Format: application/pdf
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  • 4
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    Cascade flutter analysis with transient response aerodynamics (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Two methods for calculating linear frequency domain aerodynamic coefficients from a time marching Full Potential cascade solver are developed and verified. In the first method, the Influence Coefficient, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier Transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 41; 5, 19; 1073-108
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  • 5
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    Numerical simulation of icing, deicing, and shedding (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An algorithm has been developed to numerically model the concurrent phenomena of two-dimensional transient heat transfer, ice accretion, ice shedding and ice trajectory which arise from the use of electrothermal pad. The Alternating Direction Implicit method is used to simultaneously solve the heat transfer and accretion equations occurring in the multilayered body covered with ice. In order to model the phase change between ice and water, a technique was used which assumes a phase for each node. This allows the equations to be linearized such that a direct solution is possible. This technique requires an iterative procedure to find the correct phase at each node. The computer program developed to find this solution has been integrated with the NASA-Lewis flow/trajectory code LEWICE.
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: AIAA PAPER 91-0665
    Format: text
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  • 6
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    The effects of strong shock loading on coupled bending-torsion flutter of tuned and mistuned cascades (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper presents an investigation of the effects of strong in-passage shock waves on coupled bending-torsion flutter of both tuned and mistuned cascades. The aerodynamic and inertial coupling between the bending and torsional motions of each blade are included in the analytical model. Analysis revealed (1) that the shock loading has a beneficial effect on torsional flutters of both tuned and mistuned cascades and (2) that alternating bending mistuning has a beneficial effect on shock load induced bending flutter. The latter finding becomes important when shock induced bending flutter is a problem.
    Keywords: AIRCRAFT PROPULSION AND POWER
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  • 7
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    Numerical analysis of a thermal deicer (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An algorithm has been developed to numerically model the concurrent phenomena of two-dimensional transient heat transfer, ice accretion and ice shedding which arise from the use of an electrothermal pad. The Alternating Direction Implicit method is used to simultaneously solve the heat transfer and accretion equations occurring in a multilayered body covered with ice. In order to model the phase change between ice and water, a technique was used which assumes a phase for each node. This allows the equations to be linearized such that a direct solution is possible. This technique requires an iterative procedure to find the correct phase at each node. The computer program developed to find this solution has been integrated with the NASA/Lewis flow/trajectory code LEWICE.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 92-0527
    Format: text
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  • 8
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    An experimental investigation of the effect of test-cell pressure on the performance of resistojets (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The effect of test-cell pressure on the performance of two resistojets was investigated. Tests were conducted in a vacuum facility at pressures ranging from 0.000043 to 0.54 torr for two resistojet configurations: a laboratory model and an engineering model for the Space Station. The tests showed that for each thruster there was a decline in performance when tested in vacuum pressures above 0.001 torr. Measurements were made of surface temperature, thrust, and exit-plane pitot pressure over the range of test-cell pressures. From these measurements, the decline in performance of the laboratory-model resistojet at higher cell pressures was attributed to heat losses due to convection. For the engineering-model resistojet, the decline in performance was found to be a combination of heat loss and an effect of cell pressure on the nozzle flow.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 88-3286
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  • 9
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    Transient two-dimensional heat transfer through a composite body with application to deicing of aircraft components (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Nine different numerical methods are examined for their ability to model the process of the melting and removal of ice from an airfoil using electrothermal heaters. A technique is presented for modeling the phase change which assumes a phase for each node. The technique allows solvers such as Alternating Direction Implicit, Alternating Direction Explicit, and Strongly Implicit Procedure to find a solution which can then be iterated to find the correct phase of each node. Comparisons made for a standard deicer pad comprised of five layers showed the ADI method to be superior to the other methods considered.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-0358
    Format: text
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  • 10
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    Extension of transonic flow computational concepts in the analysis of cavitated bearings (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An analogy between the mathematical modeling of transonic potential flow and the flow in a cavitating bearing is described. Based on the similarities, characteristics of the cavitated region and jump conditions across the film reformation and rupture fronts are developed using the method of weak solutions. The mathematical analogy is extended by utilizing a few computational concepts of transonic flow to numerically model the cavitating bearing. Methods of shock fitting and shock capturing are discussed. Various procedures used in transonic flow computations are adapted to bearing cavitation applications, for example, type differencing, grid transformation, an approximate factorization technique, and Newton's iteration method. These concepts have proved to be successful and have vastly improved the efficiency of numerical modeling of cavitated bearings.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 90-TRIB-40
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