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  • 1
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    Cavity Unsteady-Pressure Measurements at Subsonic and Transonic Speeds (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the Langley 8-Foot Transonic Pressure Tunnel to determine the flow characteristics of rectangular cavities with varying relative dimensions at subsonic and transonic speeds. Cavities were tested with width-to-depth ratios of 1, 4, 8, and 16 for length-to-depth ratios l/h of 1 through 17.5. The maximum cavity depth was 2.4 in., and the turbulent boundary layer approaching the cavity was approximately 0.5 in. thick. Unsteady- and mean static-pressure measurements were made at free-stream Mach numbers from 0.20 to 0.95 at a unit Reynolds number per foot of approximately 3 x 10(exp 6); however, only unsteady-pressure results are presented in this paper. Results indicate that as l/h increases, cavity flows changed from resonant to nonresonant with resonant amplitudes decreasing gradually. Resonant spectra are obtained largely in cavities with mean static-pressure distributions characteristic of open and transitional flows. Resonance sometimes occurred for closed flow. Increasing cavity width or decreasing cavity depth while holding l/h fixed had the effect of increasing resonant amplitudes and sometimes induced resonance. The effects due to changes in width are more pronounced. Decreasing Mach number has the effect of broadening the resonances.
    Keywords: Aerodynamics
    Type: NASA-TP-3669 , L-17560 , NAS 1.60:3669
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  • 2
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    The application to airfoils of a technique for reducing orifice-induced pressure error at high Reynolds numbers (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A wind tunnel investigation was conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel to study the effects of porous (sintered metal) plug orifices on orifice-induced static-pressure measurement error at high Reynolds numbers. A NACA airfoil was tested at Mach numbers from 0.60 to 0.80 and at Reynolds numbers from 6 x 1,000,000 to 40 x 1,000,000. Data are included which compare pressure measurements obtained from porous plug orifices and from conventional orifices with diameters of 0.025 cm (0.010 in.) and 0.102 cm (0.040 in.). The two dimensional airfoil code GRUMFOIL was used to calculate boundary layer displacement thickness. The response time and the downstream effect of the porous plug orifice were considered in this investigation. The results showed that the porous plug orifice could be a viable method of reducing pressure error. The data also showed that the pressure measurements obtained with a 0.102-cm-diameter orifice were very close to the measurements obtained with 0.025-cm-diameter orifice over such of the airfoil and that downstream of a shock the orifice size was not critical.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2537 , L-16002 , NAS 1.60:2537
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  • 3
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    Orifice-induced pressure error studies in Langley 7- by 10-foot high-speed tunnel (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: For some time it has been known that the presence of a static pressure measuring hole will disturb the local flow field in such a way that the sensed static pressure will be in error. The results of previous studies aimed at studying the error induced by the pressure orifice were for relatively low Reynolds number flows. Because of the advent of high Reynolds number transonic wind tunnels, a study was undertaken to assess the magnitude of this error at high Reynolds numbers than previously published and to study a possible method of eliminating this pressure error. This study was conducted in the Langley 7- by 10-Foot High-Speed Tunnel on a flat plate. The model was tested at Mach numbers from 0.40 to 0.72 and at Reynolds numbers from 7.7 x 1,000,000 to 11 x 1,000,000 per meter (2.3 x 1,000,000 to 3.4 x 1,000,000 per foot), respectively. The results indicated that as orifice size increased, the pressure error also increased but that a porous metal (sintered metal) plug inserted in an orifice could greatly reduce the pressure error induced by the orifice.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2545 , L-16001 , NAS 1.60:2545
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  • 4
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    Three-Dimensional Cavity Flow Fields at Subsonic and Transonic Speeds (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted to expand the data base and knowledge of flow fields in cavities over the subsonic and transonic speed regimes. A rectangular, 3-D cavity was tested over a Mach number range from 0.30 to 0.95 and at Reynolds numbers per foot from 1 x 10 to the 6th power to 4.2 x 10 to the 6th power. Two sizes of cavities were tested with length-to-height ratios (l/h) of 4.4 and 11.7 and with rectangular and nonrectangular cross-sections. Extensive static pressure data on the model walls were obtained and a complete tabulation of the data are presented. The boundary layer approaching the cavity was turbulent and the thickness was measured with a total pressure rake. The static pressure measurements obtained with the deep cavity configuration (l/h = 4.4) at Reynolds numbers greater than 3.0 x 10 to the 6th power per foot showed large fluctuations during the data sampling time. For the deep cavity, at lower Reynolds numbers, and for all conditions tested with the shallow cavity, the data showed much less unsteadiness. Though mean static pressure distributions have been used in past cavity analysis at transonic free stream conditions, the data presented here indicates that it is necessary to consider the instantaneous pressure distributions. The data also indicated that the shallow cavity static pressure measurements were sensitive to the thickness of the boundary layer entering the cavity.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4209 , L-16760 , NAS 1.15:4209
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  • 5
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    Characterization of cavity flow fields using pressure data obtained in the Langley 0.3-Meter Transonic Cryogenic Tunnel (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Static and fluctuating pressure distributions were obtained along the floor of a rectangular-box cavity in an experiment performed in the LaRC 0.3-Meter Transonic Cryogenic Tunnel. The cavity studied was 11.25 in. long and 2.50 in. wide with a variable height to obtain length-to-height ratios of 4.4, 6.7, 12.67, and 20.0. The data presented herein were obtained for yaw angles of 0 deg and 15 deg over a Mach number range from 0.2 to 0.9 at a Reynolds number of 30 x 10(exp 6) per ft with a boundary-layer thickness of approximately 0.5 in. The results indicated that open and transitional-open cavity flow supports tone generation at subsonic and transonic speeds at Mach numbers of 0.6 and above. Further, pressure fluctuations associated with acoustic tone generation can be sustained when static pressure distributions indicate that transitional-closed and closed flow fields exist in the cavity. Cavities that support tone generation at 0 deg yaw also supported tone generation at 15 deg yaw when the flow became transitional-closed. For the latter cases, a reduction in tone amplitude was observed. Both static and fluctuating pressure data must be considered when defining cavity flow fields, and the flow models need to be refined to accommodate steady and unsteady flows.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4436 , L-17158 , NAS 1.15:4436
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  • 6
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    Measurements of store forces and moments and cavity pressures for a generic store in and near a box cavity at subsonic and transonic speeds (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental force and moment study was conducted in the Langley 8-Foot Transonic Pressure Tunnel for a generic store in and near rectangular box cavities contained in a flat-plate configuration at subsonic and transonic speeds. Surface pressures were measured inside the cavities and on the flat plate. The length-to-height ratios were 5.42, 6.25, 10.83, and 12.50. The corresponding width-to-height ratios were 2.00, 2.00, 4.00, and 4.00. The free-stream Mach number range was from 0.20 to 0.95. Surface pressure measurements inside the cavities indicated that the flow fields for the shallow cavities were either closed or transitional near the transitional/closed boundary. For the deep cavities, the flow fields were either open or near the open/transitional boundary. The presence of the store did not change the type of flow field and had only small effects on the pressure distributions. For transitional or open transitional flow fields, increasing the free-stream Mach number resulted in large reductions in pitching-moment coefficient. Values of pitching-moment coefficient were always much greater for closed flow fields than for open flow fields.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4611 , L-17388 , NAS 1.15:4611
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  • 7
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    Experimental cavity pressure measurements at subsonic and transonic speeds. Static-pressure results (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted to determine cavity flow-characteristics at subsonic and transonic speeds. A rectangular box cavity was tested in the Langley 8-Foot Transonic Pressure Tunnel at Mach numbers from 0.20 to 0.95 at a unit Reynolds number of approximately 3 x 10(exp 6) per foot. The boundary layer approaching the cavity was turbulent. Cavities were tested over a range of length-to-depth ratios (l/h) of 1 to 17.5 for cavity width-to-depth ratios of 1, 4, 8, and 16. Fluctuating- and static-pressure data in the cavity were obtained; however, only static-pressure data is analyzed. The boundaries between the flow regimes based on cavity length-to-depth ratio were determined. The change to transitional flow from open flow occurs at l/h at approximately 6-8 however, the change from transitional- to closed-cavity flow occurred over a wide range of l/h and was dependent on Mach number and cavity configuration. The change from closed to open flow as found to occur gradually. The effect of changing cavity dimensions showed that if the vlaue of l/h was kept fixed but the cavity width was decreased or cavity height was increased, the cavity pressure distribution tended more toward a more closed flow distribution.
    Keywords: AERODYNAMICS
    Type: NASA-TP-3358 , L-17157 , NAS 1.60:3358
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  • 8
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    Measurements of fluctuating pressure in a rectangular cavity in transonic flow at high Reynolds numbers (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experiment was performed in the Langley 0.3 meter Transonic Cryogenic Tunnel to study the internal acoustic field generated by rectangular cavities in transonic and subsonic flows and to determine the effect of Reynolds number and angle of yaw on the field. The cavity was 11.25 in. long and 2.50 in. wide. The cavity depth was varied to obtain length-to-height (l/h) ratios of 4.40, 6.70, 12.67, and 20.00. Data were obtained for a free stream Mach number range from 0.20 to 0.90, a Reynolds number range from 2 x 10(exp 6) to 100 x 10(exp 6) per foot with a nearly constant boundary layer thickness, and for two angles of yaw of 0 and 15 degs. Results show that Reynolds number has little effect on the acoustic field in rectangular cavities at angle of yaw of 0 deg. Cavities with l/h = 4.40 and 6.70 generated tones at transonic speeds, whereas those with l/h = 20.00 did not. This trend agrees with data obtained previously at supersonic speeds. As Mach number decreased, the amplitude, and bandwidth of the tones changed. No tones appeared for Mach number = 0.20. For a cavity with l/h = 12.67, tones appeared at Mach number = 0.60, indicating a possible change in flow field type. Changes in acoustic spectra with angle of yaw varied with Reynolds number, Mach number, l/h ratios, and acoustic mode number.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4363 , L-16859 , NAS 1.15:4363
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  • 9
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    Status of orifice induced pressure error studies (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The construction of high Reynolds number facilities, such as the National Transonic Facility (NTF) and the 0.3-m Transonic Cryogenic Tunnel (TCT), has stimulated interest again in the study of orifice induced static pressure. In a high Reynolds number facility, the orifice will have a much larger effect on the boundary layer than in a conventional wind tunnel. The present investigation was performed in the 0.3-m TCT at Mach numbers in the range from 0.60 to 0.80 and Reynolds numbers in the range from 6,000,000 to 40,000,000 with the objective to compare the porous plug orifices to conventional 0.025 cm orifices in a high Reynolds number environment. It was found that there was an error at high Reynolds numbers which could not be neglected and that the use of a porous metal disk in a conventional orifice could virtually eliminate the orifice induced pressure error.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-0245
    Format: text
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  • 10
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    Tests of a NACA 65(sub 1)-213 airfoil in the NASA Langley 0.3-meter transonic cryogenic tunnel (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A wind-tunnel investigation was conducted to study the two dimensional aerodynamic characteristics of the NACA 65 sub 1-213 airfoil over a wide range of Reynolds numbers. Test temperature ranged from ambient to about 100K at pressures ranging from about 1.2 to 6.0 atm. Mach number was varied from 0.22 to 0.80 and Reynolds number (based on airfoil chord) from 3 million to 40 million. Data are included which demonstrate the effects of fixed transition, Mach number, and Reynolds number on the aerodynamic characteristics of the airfoil. A sample of data showing the effects of angle of attack on the pressure distribution is also given. The data are presented in an uncorrected form with no analysis.
    Keywords: AERODYNAMICS
    Type: NASA-TM-85732 , NAS 1.15:85732
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