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  • 1
    Electronic Resource
    Electronic Resource
    FACTORS INFLUENCING THE CHOICE OF FACILITIES AND TECHNIQUES FOR AERONAUTICAL DEVELOPMENT (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 154 (1968), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1968.tb15243.x
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Ground vortex flow field investigation (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Flow field investigations were conducted at the NASA Ames-Dryden Flow Visualization Facility (water tunnel) to investigate the ground effect produced by the impingement of jets from aircraft nozzles on a ground board in a STOL operation. Effects on the overall flow field with both a stationary and a moving ground board were photographed and compared with similar data found in other references. Nozzle jet impingement angles, nozzle and inlet interaction, side-by-side nozzles, nozzles in tandem, and nozzles and inlets mounted on a flat plate model were investigated. Results show that the wall jet that generates the ground effect is unsteady and the boundary between the ground vortex flow field and the free-stream flow is unsteady. Additionally, the forward projection of the ground vortex flow field with a moving ground board is one-third less than that measured over a fixed ground board. Results also showed that inlets did not alter the ground vortex flow field.
    Keywords: AERODYNAMICS
    Type: The 1987 Ground Vortex Workshop; p 61-90
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    An Analysis of the Pressures, Forces and Moments Induced by the Ground Vortex Generated by a Single Impinging Jet (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: When a jet STOVL aircraft is in STOL operation the jets impinge on the ground and generate wall jets flowing radially outward from the points at which the jets impinge. When the forward flowing part of a wall jet meets the free stream flow it is rolled back on itself forming a parabolic shaped ground vortex. Positive pressures are induced on the lower surface of the configuration ahead of the ground vortex and suction pressures are induced over the ground vortex itself. In addition, the suction pressures induced aft of the jet out of ground effect are reduced and lifting pressures are induced on the upper surface. This study analyzes available pressure and force data and develops a method for estimating the forces and moments induced in ground effect. The method includes the effects of configuration variables, height and operating conditions, as well as the effects of the location, deflection and shape of the jet. However, it is limited to single jets at subcritical nozzle pressure ratios. An analysis of the effects of moving over the ground vs. tests over a fixed ground plane is included.
    Keywords: Aerodynamics
    Type: NASA-CR-4765 , NAS 1.26:4765 , A-975988
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    The Effects of Crossflow on the Pressures and Lift Induced by the Fountain Generated Between Two Impinging Jets (1998)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: When a jet STOVL aircraft is hovering, or in a crossflow, while close to the ground wall jets flowing radially outward from the impingement points of the jets are generated. An upflow, or fountain, is generated where the wall jets from adjacent jets meet on the ground surface. The induced lift and suckdown generated by the impingement of the fountain on the lower surface of the configuration has been the subject of previous studies. This study analyzes the limited available pressure and force data on the effect of crossflow on the fountain induced lift and suckdown. The analysis includes the effects of jet spacing, height and operating conditions. However, it is limited to twin jet configurations of circular, vertical jets operating at subcritical nozzle pressure ratios over a fixed ground surface.
    Keywords: Aerodynamics
    Type: NASA/CR-1998-206955 , A-98-09726 , NAS 1.26:206955
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Small-scale experiments in STOVL ground effects (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A series of tests has been 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 cold 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: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: SAE PAPER 901060
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Prediction techniques for jet-induced effects in hover on STOVL aircraft (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Prediction techniques for jet induced lift effects during hover are available, relatively easy to use, and produce adequate results for preliminary design work. Although deficiencies of the current method were found, it is still currently the best way to estimate jet induced lift effects short of using computational fluid dynamics. Its use is summarized. The new summarized method, represents the first step toward the use of surface pressure data in an empirical method, as opposed to just balance data in the current method, for calculating jet induced effects. Although the new method is currently limited to flat plate configurations having two circular jets of equal thrust, it has the potential of more accurately predicting jet induced effects including a means for estimating the pitching moment in hover. As this method was developed from a very limited amount of data, broader applications of the method require the inclusion of new data on additional configurations. However, within this small data base, the new method does a better job in predicting jet induced effects in hover than the current method.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-TM-102818 , A-90146 , NAS 1.15:102818
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    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
  • 8
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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
  • 9
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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
  • 10
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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
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