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  • 1
    Publication Date: 2009-11-23
    Keywords: AERODYNAMICS
    Type: NAS 1.26:184996 , NASA-CR-184996
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  • 2
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    In:  CASI
    Publication Date: 2009-11-16
    Description: Aeroelasticity and unsteady flow problems of aircraft
    Keywords: AERODYNAMICS
    Type: PERFORMANCE AND DYN. OF AEROSPACE VEHICLES 1971; P 289-374
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  • 3
    Publication Date: 2011-08-24
    Description: An analytic solution of the thickness problem of a rectangular wing with parabolic airfoil section in three-dimensional flow is presented. The free-air solution is obtained by integrating the equation of the axial perturbation velocity. The Prandtl-Glauert rule can be used to derive the subsonic solution. Parts of the free-air solution are verified by taking the limit of the axial peturbation velocity on the model surface as the wing span goes to infinity. Pressure coefficients are studied for a selected wing geometry in the flow field. The solution of the thickness problem of a rectangular wing in a rectangular wind tunnel is derived using the free-air solution and the method of images.
    Keywords: AERODYNAMICS
    Type: ; : Algorithmic trends
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  • 4
    Publication Date: 2011-08-24
    Description: Unsteady flowfields around oscillating Boeing VR7 airfoil with and without a leading-edge slat were numerically investigated by a novel zonal method using a conformal mapping technique. Numerical aero-dynamic hysteresis loops show that the leading-edge slat prevents the airfoil dynamic stall at reduced frequency of 0.15, Reynolds number of 1 million, and the oscillation range of 5 deg to 25 deg.
    Keywords: AERODYNAMICS
    Type: ; : Algorithmic trends
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  • 5
    Publication Date: 2011-08-24
    Description: Fixed-wing code development is now aimed primarily at the solution of problems dominated by separation--based on the assumptions that the ability to solve such problems implies the ability to solve all other problems and that present inviscid method are already adequate for most other problems. Neither of the above assumptions are correct for rotary wing problems. This is because of the unique and overriding importance of wake modeling to rotor problems and also due to the well-known numerical diffusion problems which convectional Eulerian Computational fluid dynamics (CFD) method encounter when called on to convect strong vortical regions for long distances. The need for accurate wake analyses is probably the most fundamental difference between rotory and fixed-wing aerodynamics. In addition, rotary wing complexity requires a much more intimate relationship between test and analysis than is common in fixed-wing work. With these issues in mind, this paper will review some of our recent experience in using a unique-Eulerian-Lagrangian Computational fluid dynamics (CFC) method for the solution of a critical rotor-wake problem--the prediction of hover performance.
    Keywords: AERODYNAMICS
    Type: ; : Algorithmic trends
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  • 6
    Publication Date: 2011-08-24
    Description: A method for analyzing the mutual aerodynamic interaction between a rotor and an airframe model has been developed. This technique models the rotor implicitly through the source terms of the momentum equations. A three-dimensional, incompressible, laminar, Navier-Stokes solver in cylindrical coordinates was developed for analyzing the rotor-airframe problem. The calculations are performed on a simplified rotor-airframe model at an advance ratio of 0.1. The airframe surface pressure predictions are found to be in good agreement with wind tunnel test data. Results are also presented for velocity and pressure field distributions in the wake of the rotor.
    Keywords: AERODYNAMICS
    Type: American Helicopter Society, Journal (ISSN 0002-8711); 40; 2; p. 57-67
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  • 7
    Publication Date: 2011-08-24
    Description: An assessment is given of existing shock wave/tubulent boundary-layer interaction experiments having sufficient quality to guide turbulence modeling and code validation efforts. Although the focus of this work is hypersonic, experiments at Mach numbers as low as 3 were considered. The principal means of identifying candidate studies was a computerized search of the AIAA Aerospace Database. Several hundred candidate studies were examined and over 100 of these were subjected to a rigorous set of acceptance criteria for inclusion in the data-base. Nineteen experiments were found to meet these criteria, of which only seven were in the hypersonic regime (M is greater than 5).
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 32; 7; p. 1377-1383
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  • 8
    Publication Date: 2011-08-24
    Description: The objective of the present investigation is to assess the effect of the spatial order of accuracy used for the evaluation of the inviscid fluxes on the resolution of higher order quantitites, such as velocity gradients. The viscous terms are computed as second-order accurate with central difference formulas, even though for the explicit part of the algorithm higher order approximations may be used. A viscous/inviscid method is used, and the outer part of the flowfield is computed with the inviscid flow equations. The viscous boundary-layer type flow region close to the body surface is computed with an algebraic eddy viscosity model. Results obtained with the conservative and nonconservative formulations and the viscous/inviscid approach are compared with available experimental data. The effect of grid refinement on the accuracy of the solution is also presented.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 32; 12; p. 2471-2474
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  • 9
    Publication Date: 2010-11-08
    Description: Stability derivatives have been computed for twisted wings of different planforms that include variations in both the wing taper and the aspect ratio. Taper ratios of 1.0, 0.50, and 0.25 are considered for each of three aspect ratios: 6, 10, and 16. The specific derivatives for which results are given are the rolling moment and the yawing moment derivatives with respect to rolling velocity, yawing velocity, and angle of sideslip. In addition to the stability derivatives, results are included for determining the theoretical rolling moment due to aileron deflection and a series of influence lines is given by which the loading across the span may be determined for any angle-of-attack distribution that may occur on the wing planforms considered.
    Keywords: AERODYNAMICS
    Type: REPT-635 , Collected Works of Robert T. Jones; p 147-165
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  • 10
    Publication Date: 2010-11-08
    Description: The two control operation of a conventional airplane is treated by means of the theory of disturbed motions. The consequences of this method of control are studied with regard to the stability of the airplane in its unconstrained components of motion and the movements set up during turn maneuvers. It is found that the motion of a conventional airplane is more stable when an arbitrary kinematic constraint is imposed in banking than when such constraint is imposed in yawing. Several hypothetical assumptions of piloting procedure, each of which is considered to represent a component of the actual procedure, are studied. Different means of two control operation are also discussed and it is concluded that a reliable rolling moment control that does not give the usual adverse secondary yawing moment should be most satisfactory.
    Keywords: AERODYNAMICS
    Type: REPT-579 , Collected Works of Robert T. Jones; p 73-90
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