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  • 1
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    A three-dimensional viscous flow analysis for the helicopter tip vortex generation process about square and round tipped blades (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The tip vortex flow field occurring in the vicinity of the tip region of a helicopter rotor blade is a very complicated three-dimensional, viscous flow phenomenon. The details of the flow in the tip region can have a major effect in determining the generated rotor noise and can significantly effect the performance and dynamic loading of the rotor blade. The three-dimensional viscous subsonic tip vortex generation processes is investigated by a numerical procedure which allows spatial forward-marching integration, utilizing flow approximations from the velocity-decomposition approach of Briley and McDonald. The approach has been applied to compute the laminar and turbulent tip vortex flows for a constant thickness slab airfoil with a square tip, a constant thickness slab airfoil with a half round tip and a NACA 0012 airfoil with a half round tip. The basic mechanism of the tip vortex generation process as well as the prediction of vortex appearance, strength and secondary flow shown by the calculations are in qualitative agreement with experimental results.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-0560
    Format: text
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  • 2
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    Numerical study of three-dimensional turbulent flow interactions between blockage models and wind tunnels including longitudinally slotted test sections (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A spatial forward-marching approach is applied to compute three-dimensional turbulent flows for several blockage models in free flight, in a solid wall wind tunnel, and in a wind tunnel with longitudinal slots in the test section. The effects of area blockage in the tunnel, model growth and tunnel wall boundary layers, and of the slots are included. The large blockage models are found to have significant wall interference effects which can be reduced by the slots. The effects of the latter are confined to the region near the tunnel wall. Model/wall interference effects are not limited to the effects of area blockage; in particular, boundary layer profile shapes for a wind tunnel model in a tunnel are different from shapes for a model in free flight even when slots are used. This indicates that the flow responds differently in these two cases with the same pressure gradient.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-5017
    Format: text
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  • 3
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    Unsteady aerodynamics of rotor-stator interaction in a turbine stage (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The two-dimensional, compressible, unsteady, thin-layer Navier-Stokes equations have been used to study the turbulent flow field of a turbine rotor/stator configuration in the high pressure oxidizer turbopump of the Space Shuttle main engine. The calculations were performed on a system of patched and overlaid grids. The grid system consists of 'O-' and 'H-' grids, with the inner 'O-'grid enclosing the blade surface for an accurate resolution of the leading and trailing edges, while the outer 'H-'grid makes the treatment of boundary conditions easier. The integration scheme used is an iterative, factored, implicit method with numerical fluxes evaluated by the third-order accurate upwind-biased Osher scheme. Computed results in the form of pressure contours, Mach number contours, time-averaged surface pressure, unsteady pressure amplitude and unsteady velocity vectors are presented. Many flow phenomena, such as wake cutting by rotor airfoils and evolution of unsteady passage vortices, are discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0360
    Format: text
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  • 4
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    A three-dimensional viscous flow analysis for the helicopter tip vortex generation problem (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The tip vortex flow field occurring in the vicinity of the tip region of a a helicopter rotor blade is a very complicated three-dimensional, viscous flow phenomenon. The details of the flow in the tip region can have a major effect in determining the generated rotor noise and can significantly affect the performance and dynamic loading of the rotor blade. The three-dimensional viscous subsonic tip vortex generation processes is investigated by a numerical procedure which allows spatial forward-marching integration, utilizing flow approximations from the velocity-decomposition approach of Briley and McDonald. The approach has been applied to compute the laminar and turbulent tip vortex flows for a constant thickness slab airfoil with a square tip, a constant thickness slab airfoil with a half round tip and a NACA 0012 airfoil with a half round tip. The basic mechanism of the tip vortex generation process as well as the prediction of vortex appearance, strength and secondary flow shown by the calculations are in qualitative agreement with experimental results.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3906 , NAS 1.26:3906
    Format: application/pdf
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  • 5
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    Numerical study of laminar and turbulent flows inside a turnaround duct with and without guide vanes (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The purpose of this study is to examine in detail incompressible laminar and turbulent flows inside a turnaround duct with and without guide vanes and to investigate the effects of vanes on the flow characteristics. To perform this study, an implicit finite difference code cast in general curvilinear coordinates is further developed. The code is based on the method of pseudo-compressibility and utilize ADI or implicit approximate factorization algorithm to achieve computational efficiency. Method of segmental sweeping is developed to overcome the multiple-zone problem due to imposition of guide vanes. In the present study, several test cases have been computed. These test cases include laminar and turbulent flows inside a turnaround duct without and with two or three guide vanes. The study reveals that: (1) there exists large recirculation zones inside the duct if no vanes are present; (2) properly shaped and positional guide vanes are effective in eliminating flow separation; and (3) laminar and turbulent flows have similar flow features. But turbulent flow has less total pressure drop.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0365
    Format: text
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  • 6
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    Tip vortex computer code SRATIP. User's guide (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This User's Guide applies to the three dimensional viscous flow forward marching analysis, PEPSIG, as used for the calculation of the helicopter tip vortex flow field. The guide presents a discussion of the program flow and subroutines, as well as a list of sample input and output.
    Keywords: AERODYNAMICS
    Type: NASA-CR-172603 , NAS 1.26:172603
    Format: application/pdf
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