Non-linear and Unsteady Aerodynamic Responses of a Rolling 65-degree Delta Wing PDF Download
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Author: Alexander H. Hsia
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Languages : en
Pages :
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Author: Alexander H. Hsia
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Languages : en
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Author: Gregory A. Addington
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Category : Aerodynamic load
Languages : en
Pages : 38
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Recent analysis has shown that nearly every high-performance tactical aircraft in the inventory of American and allied air forces has experienced some sort of unexpected controlled-flight departure in the early stages of flight testing. Most, if not all, of these in-flight departures had characteristics which lead to the conclusion that they were the result of critical state encounters. Critical states are discrete flight mechanical state vector values where the aerodynamic response loses its analytic dependence on one or more of the variables in that state vector. Critical states manifest themselves as discontinuities in either magnitude or slope in static force and moment data, and as dynamic responses which may be nonlinear with respect to either geometric parameters and/or time. This report presents two analysis procedures which have shown promise in the detection of critical states. First, spectral analysis of data ensembles acquired during wind tunnel tests of two 65 degree delta wings has shown that changes in these spectra signal the presence of some critical states. Further, the nature of these spectra have in some instances provided insight into the nature of the dynamic response. The second analysis procedure involves comparing the static experimental data to a simple potential-flow-based numerical model. It was found that when the experimental dataset diverged from the numerical simulation, critical states were present. Both of these analysis procedures required no additional data to be acquired and minimal analytical effort. Therefore, they provide a cost-effective means for adverting the effects of critical states during early air vehicle test-and-evaluation programs.
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Languages : en
Pages : 13
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Since the need for improvements in high angle-of-attack maneuverability of aircraft's in transonic flight was of concern, a model was rotated around its longitudinal body axis with a dimensionless rolling rate of pi = 0.0762 (10 Hz), resulting in flow conditions with extensive vortical behavior and strongly non-linear, wing/vortex interference effects. This paper deals with validation experiments performed at the DLR Goettingen. The objective of this activity was to provide experimental data for comparison with numerical calculations performed within the international WEAG TA 15 group: Alenia (Italy), DERA (United Kingdom), DLR and EADS (Germany), and NLR (The Netherlands). A special 65 delta wing, the DLR PSP-model, was designed, manufactured and finally tested in the transonic 1mx 1m wind tunnel DNW-TWG in Goettingen. A rolling apparatus was built up to enable roll rates up to 10 Hz. A new sting concept was developed as elastic simulations showed dangerous problems associated with the rolling model exposed to the periodic aerodynamic load. The experiments were carried out at angles of attack alpha=10 and 17, M=0.8, Reynolds number of 5.3 Mio in the case of steady and 2.2 Mio for unsteady conditions. The model was equipped with only a few pressure taps for PSI and Kulite sensors, as surface pressure distributions of the model should be obtained using the pressure sensitive paint (PSP) technique, to measure the pressure all over the whole surface of the model. As the model was rotating an unsteady PSP technique had to be applied. Several steps had to be considered in order to finally use the measured pressure distributions for comparison with numerical predictions. In the case of steady conditions the results compare quite well with the conventional pressure taps and numerical calculations, in the case of the spinning model discrepancies between Kulite values and PSP as well as numerical results could be stated.
Author: X. Z. Huang
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Category :
Languages : en
Pages : 24
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This data set is selected from an extensive set of experimental results obtained for configurations with a 650 delta wing under static as well as large-amplitude high-rate rolling or pitching conditions at high incidence. The experiments were performed under a joint research program on "Non-Linear Aerodynamics under Dynamic Maneuvers" by the National Research Council of Canada (NRC (IAR)), the U.S. Air Force (USAF (AFOSR, AFRL)) and the Canadian Dept. for National Defence (DND). NASA Ames informally participated in the program through its substantial CFD work on specific test conditions. The experimental results provide both detail pressure measurements and a wide range of flow conditions covering from simple attached flow, through fully developed vortex and vortex burst flow, up to fully-stalled flow at very high incidence. Since this data set includes different levels of physical difficulty, the computational researchers wording in unsteady aerodynamics can use it as a staircase approach to the problem of validating their corresponding code Four schematic and representative configurations' were selected in the experiments (Fig. 1 to Fig. 3).
Author: Gregory A. Addington
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Category : Science
Languages : en
Pages : 200
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A static wind tunnel test of the Innovative Controls Effectors (ICE 101) conceptual aircraft configuration was conducted in the Air Force Research Laboratory's Vertical Wind Tunnel. This entry characterized the increments to the aerodynamic loading provided by the various control surfaces while using a more finely-resolved test matrix in angle of attack and sideslip than typically seen in wind tunnel testing. The purpose for obtaining these data was to determine the effect which control surface deflection had on critical state locations in preparation for the test of a second ICE model built with remotely- actuated control surfaces. (Critical states are discrete flight mechanical states where the aerodynamic response looses its analytic dependence on one or more state variables.) These data demonstrate that the aerodynamic increments are in many cases at minimum nonlinear functions of the surface deflection angle, and strongly suggest that some critical states do shift in angle of attack and/or sideslip with changing deflection angle.
Author:
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Category : Aeronautics
Languages : en
Pages : 756
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Category : Aeronautics
Languages : en
Pages : 740
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Category : Aeronautics
Languages : en
Pages : 544
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Author:
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Category : Aeronautics
Languages : en
Pages : 836
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Author: Gregory Addington
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Category :
Languages : en
Pages :
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