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  • 1
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    Study of compressible flow through a rectangular-to-semiannular transition duct (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Detailed flow field measurements are presented for compressible flow through a diffusing rectangular-to-semiannular transition duct. Comparisons are made with published computational results for flow through the duct. Three-dimensional velocity vectors and total pressures were measured at the exit plane of the diffuser model. The inlet flow was also measured. These measurements are made using calibrated five-hole probes. Surface oil flow visualization and surface static pressure data were also taken. The study was conducted with an inlet Mach number of 0.786. The diffuser Reynolds based on the inlet centerline velocity and the exit diameter of the diffuser was 3,200,000. Comparison of the measured data with previously published computational results are made. Data demonstrating the ability of vortex generators to reduce flow separation and circumferential distortion is also presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-4660 , E-9582 , NAS 1.26:4660
    Format: application/pdf
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  • 2
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    A new algorithm for five-hole probe calibration, data reduction, and uncertainty analysis (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new algorithm for five-hole probe calibration and data reduction using a non-nulling method is developed. The significant features of the algorithm are: (1) two components of the unit vector in the flow direction replace pitch and yaw angles as flow direction variables; and (2) symmetry rules are developed that greatly simplify Taylor's series representations of the calibration data. In data reduction, four pressure coefficients allow total pressure, static pressure, and flow direction to be calculated directly. The new algorithm's simplicity permits an analytical treatment of the propagation of uncertainty in five-hole probe measurement. The objectives of the uncertainty analysis are to quantify uncertainty of five-hole results (e.g., total pressure, static pressure, and flow direction) and determine the dependence of the result uncertainty on the uncertainty of all underlying experimental and calibration measurands. This study outlines a general procedure that other researchers may use to determine five-hole probe result uncertainty and provides guidance to improve measurement technique. The new algorithm is applied to calibrate and reduce data from a rake of five-hole probes. Here, ten individual probes are mounted on a single probe shaft and used simultaneously. Use of this probe is made practical by the simplicity afforded by this algorithm.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106458 , E-8319 , NAS 1.15:106458
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  • 3
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    A study of the compressible flow through a diffusing S-duct (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Benchmark aerodynamic data are presented for compressible flow through a representative S-duct configuration. A numerical prediction of the S-duct flow field, obtained from a subsonic parabolized Navier-Stokes algorithm, is also shown. The experimental and numerical results are compared. Measurements of the three-dimensional velocity field, total pressures, and static pressures were obtained at five cross-sectional planes. Aerodynamic data were gathered with calibrated pneumatic probes. Surface static pressure and surface flow visualization data were also acquired. All reported tests were conducted with an inlet centerline Mach number of 0.6. The Reynolds number, based on the inlet centerline velocity and duct inlet diameter, was 2.6 x 10(exp 6). Thin inlet turbulent boundary layers existed. The collected data should be beneficial to aircraft inlet designers and the measurements are suitable for the validation of computational codes. The results show that a region of streamwise flow separation occurred within the duct. Details about the separated flow region, including mechanisms which drive this complicated flow phenomenon, are discussed. Results also indicate that the duct curvature induces strong pressure driven secondary flows. The cross flows evolve into counter-rotating vortices. These vortices convect low momentum fluid of the boundary layer toward the center of the duct, degrading both the uniformity and magnitude of the total pressure profile.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106411 , E-8247 , NAS 1.15:106411
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  • 4
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    A study of high speed flows in an aircraft transition duct (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The study of circular-to-rectangular transition duct flows with and without inlet swirl is presented. A method was devised to create a swirling, solid body rotational flow with minimal associated disturbances. Details of the swirl generator design and construction are discussed. Coefficients based on velocities and total and static pressures measured in cross stream planes at four axial locations within the transition duct along with surface static pressures and surface oil film visualization are presented for both nonswirling and swirling incoming flows. A method was developed to acquire trace gas measurements within the transition duct at high flow velocities. Statistical methods are used to help interpret the trace gas results.
    Keywords: AERODYNAMICS
    Type: NASA-TM-104449 , E-6290 , NAS 1.15:104449
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  • 5
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    The decay of longitudinal vortices shed from airfoil vortex generators (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental study is conducted to examine the crossplane structure and streamwise decay of vortices shed from airfoil-type vortex generators. The vortex generators are set in a counter-rotating array spanning the full circumference of a straight pipe. The span of the vortex generators above the duct surface, h, is approximately equal to the local turbulent boundary layer thickness, delta. Measurement of three-component mean flow velocity in downstream crossplanes are used to characterize the structure of the shed vortices. Measurements in adjacent crossplanes (closely spaced along the streamwise coordinate) characterize the interaction and decay of the embedded vortices. A model constructed by the superposition of Oseen vortices is compared to the data for one test case.
    Keywords: AERODYNAMICS
    Type: NASA-CR-198356 , E-9730 , NAS 1.26:198356 , AIAA PAPER 95-1797 , Applied Aerodynamics Conference; Jun 19, 1995 - Jun 22, 1995; San Diego, CA; United States
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  • 6
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    Improving Diffusing S-duct Performance by Secondary Flow Control (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The objective of this research was to study ways to reduce inlet flow distortion (i.e., total pressure nonuniformity) and improve total pressure recovery in a diffusing S-duct. This was accomplished by controlling the development of secondary flows within the duct through the use of tapered-fin type vortex generators. Reported are results for the bare duct and seven different configurations of vortex generators. Data presented for each configuration include surface static pressure, surface flow visualization, and exit plane total pressure and transverse velocity. The performance of each configuration was assessed by calculating total pressure recovery and inlet distortion descriptors from the data and comparing them to the values for the bare duct. The best configuration tested reduced distortion (as measured by the DC(45) and DC(90) descriptors) by more than 50 percent while improving total pressure recovery by 0.5 percent. These results should provide valuable guidance in designing vortex generator installations in ducts and for assessing the accuracy of computational fluid dynamics (CFD) methods to calculate duct flows with installed vortex generators.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106492 , E-8479 , NAS 1.15:106492 , AIAA PAPER 94-0365 , Aerospace Sciences Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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  • 7
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    Ethylene Trace-gas Techniques for High-speed Flows (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Three applications of the ethylene trace-gas technique to high-speed flows are described: flow-field tracking, air-to-air mixing, and bleed mass-flow measurement. The technique involves injecting a non-reacting gas (ethylene) into the flow field and measuring the concentration distribution in a downstream plane. From the distributions, information about flow development, mixing, and mass-flow rates can be dtermined. The trace-gas apparatus and special considerations for use in high-speed flow are discussed. A description of each application, including uncertainty estimates is followed by a demonstrative example.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106491 , AIAA PAPER 94-0733 , E-8478 , NAS 1.15:106491 , Aerospace Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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  • 8
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    Uncertainty of Five-Hole Probe Measurements (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-10
    Description: A new algorithm for five-hole probe calibration and data reduction using a non-nulling technique was developed, verified, and reported earlier (Wendt and Reichert, 1993). The new algorithm's simplicity permits an analytical treatment of the propagation of uncertainty in five-hole probe measurement. The objectives of the uncertainty analysis are to quantify the uncertainty of five-hole probe results (e.g., total pressure, static pressure, and flow direction) and to determine the dependence of the result uncertainty on the uncertainty of all underlying experimental and calibration measurands. This study outlines a general procedure that other researchers may use to determine five-hole probe result uncertainty and provides guidance for improving the measurement technique.
    Keywords: Instrumentation and Photography
    Type: E-9328 , Fluid Measurement and Instrumentation 1994; Proceedings of the Forum, 1994 ASME FED Summer Meeting; Lake Tahoe, NV; United States|; 39-44
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  • 9
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    An experimental investigation of S-duct flow control using arrays of low-profile vortex generators (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental investigation was undertaken to measure the effect of various configurations of low-profile vortex generator arrays on the flow in a diffusing S-duct. Three parameters that characterize the vortex generator array were systematically varied to determine their effect: (1) the vortex generator height; (2) the streamwise location of the vortex generator array; and (3) the vortex generator spacing. Detailed measurements of total pressure at the duct exit, surface static pressure, and surface flow visualization were gathered for each vortex generator configuration. These results are reported here along with total pressure recovery and distortion coefficients determined from the experimental data. Each array of vortex generators tested improved total pressure recovery. The configuration employing the largest vortex generators was the most effective in reducing total pressure recovery. No configuration of vortex generators completely eliminated the flow separation that naturally occurs in the S-duct, however the extent of the separated flow region was reduced.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106030 , E-7595 , NAS 1.15:106030 , Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States
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  • 10
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    An experimental investigation of the flow in a diffusing S-duct (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Compressible, subsonic flow through a diffusing S-duct has been experimentally investigated. Benchmark aerodynamic data are presented for flow through a representative S-duct configuration. The collected data would be beneficial to aircraft inlet designers and is suitable for the validation of computational codes. Measurements of the 3D velocity field and total and static pressures were obtained at five cross-sectional planes. Surface static pressures and flow visualization also helped to reveal flow field characteristics. All reported tests were conducted with an inlet centerline Mach number of 0.6 and a Reynolds number, based on the inlet centerline velocity and duct inlet diameter, of 2.6 x 10(exp 6). The results show that a larger region of streamwise flow separation occurred within the duct. Details about the separated flow region, including mechanisms which drive this complicated flow phenomenon, are discussed. Transverse velocity components indicate that the duct curvature induces strong pressure driven secondary flows, which evolve into a large pair of counter-rotating vortices. These vortices convect the low momentum fluid of the boundary layer towards the center of the duct, degrading both the uniformity and magnitude of the total pressure profile.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-105809 , E-7240 , NAS 1.15:105809 , AIAA PAPER 92-3622 , Joint Propulsion Conference and Exhibit; Jul 06, 1992 - Jul 08, 1992; Nashville, TN; United States
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