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  • 1
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    Tunnel-to-tunnel correlation (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Flow quality is discussed. Incremental comparisons of: (1) the angle of attack, (2) the axial force coefficient, and (3) the base cavity axial force coefficient against the normal force coefficient are presented. Relative blockage determination, relative buoyancy corrections, and boundary layer transition length are discussed. Blockage buoyancy caused by tunnel model wall dynamic interaction is discussed in terms of adaptive walls. The effect of 'transonic turbulence factor' is considered.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center Wind-Tunnel(Flight Correlation, 1981; p 47-63
    Format: text
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  • 2
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    Computer studies of hybrid slotted working sections with minimum steady interference at subsonic speeds (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Currently there is renewed interest in the evaluation and reduction of steady wind tunnel wall interference, especially for large models. Evaluation of previous predictions for perforated and slotted tunnels suggests that a hybrid slotted tunnel (i.e., a slotted tunnel with closed slats and perforated slots) should offer minimum corrections for upwash, flow curvature and solid blockage. This suggestion is confirmed by the present computer studies of a range of rectangular hybrid slotted tunnels. The computer studies are for tunnel working section height to breadth ratios of 0.835 and 0.600 over the Mach number range from 0 to 0.85. Wings swept at 28 deg and 50 deg, with ratios of model span to tunnel breadth varying from 0 to 0.7, are considered. An idealized fuselage shape is used to predict solid and wake blockage corrections for the wall configurations selected on the basis of minimum upwash and curvature interference.
    Keywords: AERODYNAMICS
    Type: Aeronautical Journal (ISSN 0001-9240); 89; 135-148
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  • 3
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    Blockage correction in three-dimensional wind tunnel testing based on the wall signature method (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An improved wall interference assessment and correction method for three-dimensional wind tunnel testing is presented. Blockage corrections on the surface of a test article are calculated based on a limited number of wall pressure measurements. These measurements are combined with a signature analysis procedure and influence functions to determine an equivalent test article and wake representation. Pressure coefficient corrections are calculated based on this equivalent body. The signature analysis procedure is modified to improve the on-line operation of the wall signature method. A new geometry of the equivalent body is introduced which can be combined with existing panel codes more effectively. The calculation of influence functions and the determination of pressure coefficient corrections are based on a panel code. Therefore it is possible to apply the present method to any closed tunnel cross section. A numerical simulation of the idealized flow field of a wing and its wake in a rectangular wind tunnel is used to verify the improved wall signature method. The present method is considered to calculate blockage corrections in the NASA/ARC 12ft Pressure Wind Tunnel.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 92-3925
    Format: text
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  • 4
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    Effects of compressibility and free-stream turbulence on boundary layer transition in high-subsonic and transonic flows (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Based on the existing boundary layer transition data, the effects of compressibility, pressure fluctuations, and free-stream turbulence have been reexamined for subsonic and transonic flow speeds. It is confirmed that the compressibility effects may be adequately expressed in terms of a simple correlation with free-stream Mach number. Pressure fluctuations, especially at low levels, do not seem to significantly affect the transition phenomenon. Effects of free-stream turbulence in high-subsonic and transonic flows are similar to the trends observed for low-speed flows and the transition process is hastened. The trends, as seen from slender cone flow data, seem to suggest power law correlations between transition Reynolds number and free-stream turbulence.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-0764
    Format: text
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  • 5
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    Computer studies of hybrid-slotted working sections with minimum interference at subsonic speeds (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A series of computations on tunnel boundary-interference effects for hybrid-slotted working sections was performed using the WALINT code. The slots were modeled as lines of porosity with linear crossflow characteristics. The basic shape evaluated was for a rectangular section with height-to-width ratio = 0.835 and its companion in the duplex mode (half model testing) with height-to-width ratio = 0.6. A best overall basic configuration was determined with seven slots on each wall with open area ratio on each wall of 17.5%. For both full-span and half-model testing, the optimum solution required closing all but two slots on each of the half-walls parallel to the plane of the wing (equivalent to four slots on the full floor and ceiling). The results are presented here for the best configurations and are shown to be within the figure-of-merit range of + or - 0.04 in upwash, and + or - 0.1 in curvature for the Mach number range 0.6 to 0.85. Blockage effects are shown to be small.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-86002 , A-9845 , NAS 1.15:86002
    Format: application/pdf
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  • 6
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    Correlation of Preston-tube data with laminar skin friction (Log No. J12984) (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Preston tube data within laminar boundary layers obtained on a sharp ten-degree cone in the NASA Ames eleven-foot transonic wind tunnel are correlated with the corresponding values of theoretical skin friction. Data were obtained over a Mach number range of 0.30 to 0.95 and unit Reynolds numbers of 9.84, 13.1, and 16.4 million per meter. The rms scatter of skin friction coefficient about the correlation is of the order of one percent, which is comparable to the reported accuracy for calibrations of Preston tubes in incompressible pipe flows. In contrast to previous works on Preston tube/skin friction correlations, which are based on the physical height of the probe's face, this satisfactory correlation for compressible boundary layer flows is achieved by accounting for the effects of a variable "effective" height of the probe. The coefficients, which appear in the correlation, are dependent on the particular tunnel environment. The general procedure can be used to define correlations for other wind tunnels.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-84827 , NAS 1.15:84827 , LOG-J12984
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  • 7
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    On boundary layer transition in high-subsonic and transonic flow under the influence of acoustic disturbances and free-stream turbulence (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The existing data base which quantifies the roles played by the Mach number, turbulence level, and acoustic noise in the flow quality of wind tunnels is reviewed. Attention is given to the effects on end (ET) and beginning (BT) transitions in flows over a 10 deg cone in transonic channels. The Re of both ET and BT flows were significantly affected by the Mach number, acoustic noise level and the noise frequency content. A unit increment in the Mach number increased the Re beyond 3,000,000, while noise below the 1 percent level in the rms pressure coefficient did not alter the transition phenomenon. More data are required on the effects of turbulence, which was a significant factor, and in the settling chamber, test section, plenum and diffuser to trace the locations and magnitudes of the acoustic sources.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-0082
    Format: text
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  • 8
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    Pressure data from a 64A010 airfoil at transonic speeds in heavy gas media of ratio of specific heats from 1.67 to 1.12 (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A NACA 64A010 pressure-instrumented airfoil was tested at transonic speeds over a range of angle of attack from -1 to 12 degrees at various Reynolds numbers ranging from 2 to 6 million in air, argon, Freon 12, and a mixture of argon and Freon 12 having a ratio of specific heats corresponding to air. Good agreement of results is obtained for conditions where compressibility is not significant and for the air and comparable argon-Freon 12 mixture. Comparison of heavy gas results with air, when adjusted for transonic similarity, show improved, but less than desired agreement.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-62468 , A-6225
    Format: application/pdf
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  • 9
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    Correlation of Preston-tube data with laminar skin friction (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Preston-tube data have been obtained on a sharp ten-degree cone in the NASA Ames Eleven-Foot Transonic Wind Tunnel. Data were obtained over a Mach number range of 0.30 to 0.95 and unit Reynolds numbers of 9.84, 13.1, and 16.4 million per meter. The portions of these data, that were obtained within laminar boundary layers, have been correlated with the corresponding values of theoretical skin friction. The rms scatter of skin-friction coefficient about the correlation is of the order of one percent, which is comparable to the reported accuracy for calibrations of Preston-tubes in incompressible pipe-flows. In contrast to previous works on Preston-tube/skin-friction correlations, which are based on the physical height of the probe's face, this very satisfactory correlation for compressible boundary-layer flows is achieved by accounting for the effects of a variable 'effective' height of the probe. The coefficients, which appear in the correlation, are dependent on the particular tunnel environment. The general procedure can be used to define correlations for other wind tunnels.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 82-0591 , In: Aerodynamic Testing Conference; Mar 22, 1982 - Mar 24, 1982; Williamsburg, VA
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  • 10
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    The effect of ejector augmentation on test-section flow quality in the Calspan 8-ft transonic wind tunnel (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Tests to determine the flow disturbances effects of four ejectors located in the corners just downstream of the diffuser in the Calspan wind tunnel are described. The flow quality in the nonejector mode is employed as the base-line configuration, and operating parameters are compared with data from other wind tunnels. During tests with the ejectors working, fluctuation levels increased between Mach 0.4-0.6, while temperature and vorticity levels remained constant. The ejector exhibited broad spectrum noise typical of free jet noise, yet static pressure measurements revealed only a slight increase in the broadband rms levels with the ejectors on, indicating negligible disturbances upstream caused by the ejectors. Choking the diffuser eliminated the jet noise, and the use of ejectors in the Mach range considered is concluded to cause no significant degradation in the Calspan tunnel flow quality.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 82-0571 , In: Aerodynamic Testing Conference; Mar 22, 1982 - Mar 24, 1982; Williamsburg, VA
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