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  • 1
    facet.materialart.
    Unknown
    Forces and pressures induced on circular plates by a single lifting jet in ground effect (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: NASA Ames is conducting a program to develop improved methods for predicting suckdown and hot-gas ingestion on jet V/STOL aircraft when they are in ground effect. As part of that program a data base is being created that provides a systematic variation of parameters so that current empirical prediction procedures can be modified. The first series of tests in this program is complete. This report is one of three that presents the data obtained from tests conducted at Lockheed Aeronautical Systems - Rye Canyon Facility and the High Bay area of the 40 by 80 foot Wind Tunnel at Ames Research Center. Suckdown on two circular plates is examined.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102816 , A-90142 , NAS 1.15:102816
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    On the estimation of jet-induced fountain lift and additional suckdown in hover for two-jet configurations (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Currently available methods for estimating the net suckdown induced on jet V/STOL aircraft hovering in ground effect are based on a correlation of available force data and are, therefore, limited to configurations similar to those in the data base. Experience with some of these configurations has shown that both the fountain lift and additional suckdown are overestimated but these effects cancel each other for configurations within the data base. For other configurations, these effects may not cancel and the net suckdown could be grossly overestimated or underestimated. Also, present methods do not include the prediction of the pitching moments associated with the suckdown induced in ground effect. An attempt to develop a more logically based method for estimating the fountain lift and suckdown based on the jet-induced pressures is initiated. The analysis is based primarily on the data from a related family of three two-jet configurations (all using the same jet spacing) and limited data from two other two-jet configurations. The current status of the method, which includes expressions for estimating the maximum pressure induced in the fountain regions, and the sizes of the fountain and suckdown regions is presented. Correlating factors are developed to be used with these areas and pressures to estimate the fountain lift, the suckdown, and the related pitching moment increments.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102268 , A-90040 , NAS 1.15:102268
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Dynamic response of induced pressures, suckdown, and temperatures for two tandem jet STOVL configurations (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: NASA Ames Research Center has been conducting a program to improve the methods for predicting the jet-induced lift loss (suckdown) and hot gas ingestion on jet Short Takeoff and Vertical Landing (STOVL) aircraft during hover near the ground. As part of that program, small-scale hover tests were conducted to expand the current data base and to improve upon the current empirical methods for predicting jet-induced lift loss and hot gas ingestion (HGI) effects. This report is one of three data reports covering data obtained from hover tests conducted at Lockheed Aeronautical Systems, Rye Canyon Facility. It will include dynamic (time dependent) test data for both lift loss and HGI parameters (height, nozzle temperature, nozzle pressure ratio, and inlet location). The flat plate models tested were tandem jet configurations with three planform variations and variable position side-by-side sucking inlets mounted above the planform. Temperature time lags from 8-15 seconds were observed before the model temperatures stabilize. This was larger than the expected 1.5-second lag calculated from literature. Several possible explanations for the flow temperatures to stabilize may include some, or all, of the following: thermocouple lag, radiation to the model surface, and heat loss to the ground board. Further investigations are required to understand the reasons for this temperature lag.
    Keywords: AERODYNAMICS
    Type: NASA-TM-103934 , A-90290 , NAS 1.15:103934
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    On the anomalies in single-jet hover suckdown data (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The data from nine different investigations of the suckdown induced in ground effect by a single jet issuing from plates of various sizes and shapes have been examined and compared. The results show that the generally accepted method for estimating suckdown significantly underestimated the suckdown for most of the configurations. The study identified several factors that could contribute to the differences. These include ground board size, plate edge effects, jet flow quality, jet impingement angle, the size of the chamber in which the tests were run, and obstructions in the region above the model. Most of these factors have not been investigated and in many cases items such as the size of the test chamber, jet flow quality, ground board size, etc., have not even been shown in the documents reporting the investigation. A program to investigate the effects of these factors is recommended.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102261 , A-90021 , NAS 1.15:102261
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
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    Jet-induced ground effects on a parametric flat-plate model in hover (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The jet-induced forces generated on short takeoff and vertical landing (STOVL) aircraft when in close proximity to the ground can have a significant effect on aircraft performance. Therefore, accurate predictions of these aerodynamic characteristics are highly desirable. Empirical procedures for estimating jet-induced forces during the vertical/short takeoff and landing (V/STOL) portions of the flight envelope are currently limited in accuracy. The jet-induced force data presented significantly add to the current STOVL configurations data base. Further development of empirical prediction methods for jet-induced forces, to provide more configuration diversity and improved overall accuracy, depends on the viability of this STOVL data base. The data base may also be used to validate computational fluid dynamics (CFD) analysis codes. The hover data obtained at the NASA Ames Jet Calibration and Hover Test (JCAHT) facility for a parametric flat-plate model is presented. The model tested was designed to allow variations in the planform aspect ratio, number of jets, nozzle shape, and jet location. There were 31 different planform/nozzle configurations tested. Each configuration had numerous pressure taps installed to measure the pressures on the undersurface of the model. All pressure data along with the balance jet-induced lift and pitching-moment increments are tabulated. For selected runs, pressure data are presented in the form of contour plots that show lines of constant pressure coefficient on the model undersurface. Nozzle-thrust calibrations and jet flow-pressure survey information are also provided.
    Keywords: AERODYNAMICS
    Type: NASA-TM-104001 , A-93040 , NAS 1.15:104001
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Unknown
    Suckdown, fountain lift, and pressures induced on several tandem jet V/STOL configurations (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: As part of a program to improve the methods for predicting the suckdown and hot gas ingestion for jet V/STOL aircraft in ground effect, a data base is being created that provides a systematic variation of parameters so that a new empirical prediction procedure can be developed. The first series of tests in this program was completed. Suckdown, fountain lift, and pressures induced on several two-jet V/STOL configurations are described. It is one of three reports that present the data obtained from tests conducted at Lockheed Aeronautical Systems-Rye Canyon Facility and in the High Bay area of the 40 by 80 foot wind tunnel complex at NASA Ames Research Center.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102817 , A-90144 , NAS 1.15:102817
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Postflight aerothermodynamic analysis of Pegasus(tm) using computational fluid dynamic techniques (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The objective was to validate the computational capability of the NASA Ames Navier-Stokes code, F3D, for flows at high Mach numbers using comparison flight test data from the Pegasus (tm) air launched, winged space booster. Comparisons were made with temperature and heat fluxes estimated from measurements on the wing surfaces and wing-fuselage fairings. Tests were conducted for solution convergence, sensitivity to grid density, and effects of distributing grid points to provide high density near temperature and heat flux sensors. The measured temperatures were from sensors embedded in the ablating thermal protection system. Surface heat fluxes were from plugs fabricated of highly insulative, nonablating material, and mounted level with the surface of the surrounding ablative material. As a preflight design tool, the F3D code produces accurate predictions of heat transfer and other aerodynamic properties, and it can provide detailed data for assessment of boundary layer separation, shock waves, and vortex formation. As a postflight analysis tool, the code provides a way to clarify and interpret the measured results.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186017 , H-1765 , NAS 1.26:186017
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Small-scale experiments in STOVL ground effects (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A series of tests was completed in which suckdown and fountain forces and pressures were measured on circular plates and twin-tandem-jet generic STOVL (short takeoff and vertical landing) configurations. The tests were conducted using a small-scale hover rig, for jet pressure ratios up to 6 and jet temperatures up to 700 F. The measured suckdown force on a circular plate with a central jet was greater than that found with a commonly used empirical prediction method. The present data showed better agreement with other sets of data. The tests of the generic STOVL configurations were conducted to provide force and pressure data with a parametric variation of parameters so that an empirical prediction method could be developed. The effects of jet pressure ratio and temperature were found to be small. Lift improvement devices were shown to substantially reduce the net suckdown forces.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102813 , A-90137 , NAS 1.15:102813 , RAS International Powered Life Conference; Aug 01, 1990; London
    Format: application/pdf
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