1,721,048 research outputs found
Investigation of the effect of two-dimensional cavities on boundary layers in an adverse pressure gradient
Get PDFThe present investigation evaluated one aspect of the feasibility of the use of multiple cavities as an airfoil high-lift device. The effects of cavities on the boundary layer characteristics in several pressure gradients were determined experimentally and computationally. Experimentally, it was found that up to four cavities could be deployed with only a small change to the boundary layer profiles downstream of the cavities and without significantly modifying the resultant streamwise pressure distribution. From the computational results for both of the wind tunnel test section lengths used in the experimental investigation, it was found that a grid which provided a converged solution in less than a few hundred iterations was needed before a reasonable comparison with experimental data could obtained. It was also found for these converged solutions that the appropriate grid clustering and density as well as the cell size required for a satisfactory solution was not always apparent before comparing computational results with experimental data. Overall, the investigation results show that a multiple cavity high-lift concept may be feasible.Approved for public release; distribution is unlimited.NANational Aeronautics and Space Administration author (civilian).;NASA authorhttp://archive.org/details/investigationofe109453217
Numerical investigation of subsonic flow over bodies of revolution and a typical missile forebody
Get PDFIt was the objective of this investigation to study the subsonic flow over a missile forebody. To this end, the NASA Ames developed OVERFLOW, three dimensional, Navier-Stokes Code was applied and detailed results were obtained for the missile forebody. The flow conditions were set at a Mach Number of 0.3 and Reynolds Number of two million for each angle of attack at 0, 2, 6, 10, and 14 degrees. These viscous flow solutions were compared with three inviscid flow solutions, namely Slender Body Theory, von Karman's Method, and the NASA Ames Panel Code called PMARC. As expected, the OVERFLOW and PMARC solutions were in good agreement at zero and small angles of attack. As the angle of attack was increased, the OVERFLOW solution showed the development of the vortical flow separation on the leeward side of the body.U.S. Army (USA) authorhttp://archive.org/details/numericalinvesti109453516
Evaluation of the NASA-Ames panel method (PMARC) for aerodynamic missile design
Get PDFThe NASA Ames Research Center developed panel code (PMARC) is investigated to explore its suitability for aerodynamic missile design. To this end, PMARC is first assessed by applying it to several problems for which other solutions and experimental data are available, i.e., steady flow past a wing-body configuration, delta wings, biplane wings, wings in ground effect, and unsteady flow of pitching and impulsively started wings. Good agreement is found in all cases. PMARC is then applied to two missile configurations. Again, encouraging agreement with available experimental data is found provided the wake shedding from the missile body is modeled properly. Subject Terms: PMARC, Panel methods, Aerodynamic coefficients, Potential flow, Missile aerodynamic design.U.S. Navy (U.S.N.) author.http://archive.org/details/evaluationofnasa10945757
Investigation of incompressible cascade flows using a viscous/inviscid interactive code.
Get PDFhttp://archive.org/details/investigationofi109452305
Computational investigation of low speed flow over low aspect ratio aircraft configurations
Get PDFThe objective of this thesis was to contribute to the development of a second-order approximation to the steady and oscillatory lifting flow past low aspect ratio wings by establishing the validity of a NASA-Ames developed incompressible three-dimensional flow panel code named PMARC, which would subsequently be used to test the range of validity of this second-order theory. The steady state configurations modelled in the validation process include swept back, delta and rectangular wings, an F5 wing and three equivalent bodies of revolution. Oscillatory cases were also run with one delta and the F5 wings and their respective equivalent bodies of revolution, as well as with one spindle. In steady state, comparison with experimental and theoretical data proved PMARC to be very accurate for lift and pressure calculations, but revealed a discrepancy in the velocity distribution calculation around delta wings. This finding was corroborated by applying the slender body/slender wing theory (Oswatitsch-Keune theory) to the delta wing. The unsteady state results are presented, but their validation is left for future work. As part of its primary objective, this thesis also presents a computer code that generates the F5 wing equivalent body of revolution from its chordwise section definition. In order to be used as base software to the second-order theory, PMARC will have to be corrected, or a new software will have to be validated.NANACanadian Armed Forces author.http://archive.org/details/computationalinv109453128
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Experimental and computational analysis of separation bubble behavior for compressible, steady and oscillatory flows over a NACA 0012 airfoil at M=0.3 and a reynolds number of 540,000.
Get PDFIn this thesis, the separation bubble behavior and its effect on the steady and dynamic stall characteristics of a thin airfoil in a compressible flow at a transitional Reynolds number was studied. For such flows, laminar separation occurs near the airfoil leading edge, but turbulent reattachment occurs within a short distance downstream, forming a separation bubble in the underlying region. Two experimental techniques, point diffraction interferometry (PDI) and laser doppler velocimetry (LDV), were used to acquire detailed flowfield information that showed the development of the leading-edge separation bubble and its subsequent bursting at higher angles of attack. The initiation of the stall process from the leading-edge separation bubble as opposed to trailing-edge flow reversal pointed to the need for transitional flow analysis. Both in the boundary layer and Reynolds-averaged, Navier-Stokes (N-S) analysis methods, transition models were incorporated to determine the location and extent of the transition zone that best modeled the measured separation bubble behavior. Computed results for steady flow gave remarkable agreement with the measurementsApproved for public release; distribution is unlimited.Aeronautical Engineer, Naval Air Warfare Center, Weapons Divisionhttp://archive.org/details/experimentalndco10945836
Evaluation of the Boeing PAN AIR technologies code (A502i) through prediction of separation forces on the GBU-24
Get PDFThe Boeing PAN AIR Technologies code (A502i) is investigated to explore its suitability for determination of separation forces on ordnance. To this end, A502i is first assessed by applying it to three problems for which other solutions and experimental data are available, i.e. steady flow past a rectangular, parabolic arc wing and a delta wing at both subsonic and supersonic conditions. Good agreement is found in all cases. A502i is then applied to the GBU-24's being in two configurations for a subsonic case and a supersonic case. Good agreement is found with data obtained from wind tunnel experiments for low angles of attackU.S. Navy (U.S.N.) author.http://archive.org/details/evaluationofboei10945832
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
