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  • 1
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    Effect of upstream sidewall boundary layer removal on an airfoil test (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Sidewall boundary layer effects were investigated by applying partial upstream sidewall boundary layer removal in the Langley 0.3-m transonic cryogenic tunnel. Over the range of sidewall boundary layer displacement thickness of these tests the influence on pressure distribution was found to be small for subcritical conditions; however, for supercritical conditions the shock position was affected by the sidewall boundary layer. For these tests (with and without boundary layer remove) comparisons with predictions of the GRUMFOIL computer code indicated that Mach number corrections due to the sidewall boundary layer improve the agreement for both subcritical and supercritical conditions. The results also show that sidewall boundary layer removal reduces the magnitude of the sidewall correction; however, a suitable correction must still be made.
    Keywords: AERODYNAMICS
    Type: Wind Tunnel Wall Interference Assessment and Correction, 1983; p 143-163
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    A PC-based simulation of the National Transonic Facitity's safety microprocessor (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A brief study was undertaken to demonstrate the feasibility of using a state-of-the-art off-the-shelf high speed personal computer for simulating a microprocessor presently used for wind tunnel safety purposes at Langley Research Center's National Transonic Facility (NTF). Currently, there is no active display of tunnel alarm/alert safety information provided to the tunnel operators, but rather such information is periodically recorded on a process monitoring computer printout. This does not provide on-line situational information nor permit rapid identification of safety operational violations which are able to halt tunnel operations. It was therefore decided to simulate the existing algorithms and briefly evaluate a real-time display which could provide both position and trouble shooting information.
    Keywords: COMPUTER SYSTEMS
    Type: NASA-TM-109003 , NAS 1.15:109003
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Control of large cryogenic tunnels (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: For the efficient and economic operation of large cryogenic wind tunnels, automatic control is necessary to precisely regulate the temperature, pressure, and Mach number. The features of the control system currently in operation at the U.S. National Transonic Facility are presented. Some unique features of the tunnel temperature control law are the automatic tunnel cool down utilizing structural temperature feedback and the fan power based liquid nitrogen nozzle switching logic that have played a key role in realizing good automatic tunnel control.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 92-3930
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Development and validation of a hybrid-computer simulator for a transonic cryogenic wind tunnel (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study was undertaken to model the cryogenic wind tunnel process, to validate the model by the use of experimental data from the Langley 0.3 Meter Transonic Cryogenic Tunnel, and to construct an interactive simulator of the cryogenic tunnel using the validated model. Additionally, this model was used for designing closed loop feedback control laws for regulation of temperature and pressure in the 0.3 meter cryogenic tunnel. The global mathematical model of the cryogenic tunnel that were developed consists of coupled, nonlinear differential governing equations based on an energy state concept of the physical cryogenic phenomena. Process equations and comparisons between actual tunnel responses and computer simulation predictions were examined. Also included are the control laws and simulator responses obtained using the feedback schemes for closed loop control of temperature and pressure were also included.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: NASA-TP-1695 , L-13691
    Format: application/pdf
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  • 5
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    Studies of sidewall boundary layer in the Langley 0.3 meter transonic cryogenic tunnel with and without suction (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Boundary layer measurements on the sidewalls of the Langley 0.3 Meter Transonic Cryogenic Tunnel were made to determine the effectiveness of the passive boundary layer bleed system over a Reynolds number range from 20 to 200 x 10 to the sixth power per meter at Mach numbers from 0.30 to 0.76. The tunnel sidewall boundary layer displacement thickness was about 2 percent of the width of the test section without the boundary layer bleed. Measured velocity profiles correlated well with the defect law of Hama. With the boundary layer bleed equivalent to about 2 percent of the test section mass flow, the boundary layer displacement thickness reduced to about 1 percent of the test section width, which is generally considered acceptable for testing airfoils. It was also noticed that effectiveness of the bleed was nearly independent of the Mach number and Reynolds number over the range of conditions tested. A comparison of the measured suction effectiveness of the bleed with the finite difference and integral methods of boundary layer calculation showed good agreement.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-2096 , L-15437 , NAS 1.60:2096
    Format: application/pdf
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  • 6
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    Flight investigation of manual and automatic VTOL decelerating instrument approaches and landings (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A flight investigation was undertaken to study the problems associated with manual and automatic control of steep, decelerating instrument approaches and landings under simulated instrument conditions. The study was conducted with a research helicopter equipped with a three-cue flight-director indicator. The scope of the investigation included variations in the flight-director control laws, glide-path angle, deceleration profile, and control response characteristics. Investigation of the automatic-control problem resulted in the first automated approach and landing to a predetermined spot ever accomplished with a helicopter. Although well-controlled approaches and landings could be performed manually with the flight-director concept, pilot comments indicated the need for a better display which would more effectively integrate command and situation information.
    Keywords: NAVIGATION
    Type: NASA-TN-D-7524 , L-9311
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Modeling and control of a LN2-GN2 operated closed circuit cryogenic wind tunnel (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An explicit but simple lumped parameter nonlinear multivariable model of a LN2-GN2-operated closed circuit cryogenic wind tunnel has been developed and its basic features have been experimentally validated. The model describes the mass-energy interaction involved in the cryogenic tunnel process and includes the real gas properties of nitrogen gas.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: International Symposium on Cryogenic Wind Tunnels; Apr 03, 1979 - Apr 05, 1979; Southampton
    Format: text
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  • 8
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    Sensitivity analysis of cool-down strategies for a transonic cryogenic tunnel (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Guidelines and suggestions substantiated by real-time simulation data to ensure optimum time and energy use of injected liquid nitrogen for cooling the Langley 0.3-Meter Transonic Cryogenic Tunnel (TCT) are presented. It is directed toward enabling operators and researchers to become cognizant of criteria for using the 0.3-m TCT in an energy- or time-efficient manner. Operational recommendations were developed based on information collected from a validated simulator of the 0.3-m TCT and experimental data from the tunnel. Results and trends, however, can be extrapolated to other similarly constructed cryogenic wind tunnels.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: NASA-TM-84527 , L-14366 , NAS 1.15:84527
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Cooldown Strategy for Cryogenic Wind Tunnels (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Criteria substantiated by experimental and real-time simulation data ensure optimal utlization of liquid nitrogen injected for cooling a 0.3-m transonic cryogenic tunnel (TCT). Research includes simulated cooldowns using procedures normally employed by each of several TCT operators, simulated cooldowns at constant mach number, simulated cooldowns at various constant fan speeds and cooldowns at constant metal-to-gas temperature differences.
    Keywords: MECHANICS
    Type: LAR-13012 , NASA Tech Briefs (ISSN 0145-319X); 8; 2; P. 238
    Format: text
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  • 10
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    Effect of gyro verticality error on lateral autoland tracking performance for an inertially smoothed control law (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of a simulation study performed to determine the effects of gyro verticality error on lateral autoland tracking and landing performance are presented. A first order vertical gyro error model was used to generate the measurement of the roll attitude feedback signal normally supplied by an inertial navigation system. The lateral autoland law used was an inertially smoothed control design. The effect of initial angular gyro tilt errors (2 deg, 3 deg, 4 deg, and 5 deg), introduced prior to localizer capture, were investigated by use of a small perturbation aircraft simulation. These errors represent the deviations which could occur in the conventional attitude sensor as a result of the maneuver-induced spin-axis misalinement and drift. Results showed that for a 1.05 deg per minute erection rate and a 5 deg initial tilt error, ON COURSE autoland control logic was not satisfied. Failure to attain the ON COURSE mode precluded high control loop gains and localizer beam path integration and resulted in unacceptable beam standoff at touchdown.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TM-X-3545 , L-11428
    Format: application/pdf
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