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  • 1
    Publication Date: 2013-08-31
    Description: The application of stability theory in Laminar Flow Control (LFC) research requires that density and velocity profiles be specified throughout the viscous flow field of interest. These profile values must be as numerically accurate as possible and free of any numerically induced oscillations. Guidelines for the present research project are presented: develop an efficient and accurate procedure for solving the 3-D boundary layer equation for aerospace configurations; develop an interface program to couple selected 3-D inviscid programs that span the subsonic to hypersonic Mach number range; and document and release software to the LFC community. The interface program was found to be a dependable approach for developing a user friendly procedure for generating the boundary-layer grid and transforming an inviscid solution from a relatively coarse grid to a sufficiently fine boundary-layer grid. The boundary-layer program was shown to be fourth-order accurate in the direction normal to the wall boundary and second-order accurate in planes parallel to the boundary. The fourth-order accuracy allows accurate calculations with as few as one-fifth the number of grid points required for conventional second-order schemes.
    Keywords: AERODYNAMICS
    Type: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 517-545
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-28
    Description: Numerical solutions of the three-dimensional, compressible laminar boundary-layer equations for a general aviation fuselage are presented. The numerical procedure is second-order accurate and independent of the cross-flow velocity direction. Numerical results are presented for a Mach number and unit Reynolds number of 0.3 and 7 x 10 to the 6th/m, respectively, for angles of attack of 0 and 3 deg. Comparisons are made between results obtained using a general nonorthogonal curvilinear body oriented coordinate system and a streamline coordinate system. Axisymmetric analogue results are also compared with the three-dimensional solutions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 90-0305
    Format: text
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  • 3
    Publication Date: 2019-06-28
    Description: Laminar flow control and drag reduction research requires accurate boundary layer solutions as input to the three-dimensional stability analysis procedures currently under development. In support of these major programs, a fourth-order accurate finite difference scheme for solving the three-dimensional, compressible boundary layer equations has been developed and is presented in this paper. The method employs a two-point scheme in the wall normal direction and second order zigzag scheme in the cross flow direction. Accurate procedures to interface with the inviscid results are also presented. The results of applying the procedure to laminar flow on wings and fuselages are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0130
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  • 4
    Publication Date: 2019-07-12
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 861-868
    Format: text
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  • 5
    Publication Date: 2019-08-28
    Description: In spite of many attempts at modeling natural transition, it has not been possible to predict the streamwise intensities. A procedure is developed which incorporates some results of linear stability theory into one-equation and stress model formulations. The stresses resulting from fluctuations in the transitional region have turbulent, laminar (nonturbulent) and large eddy components. Comparison with Schubauer and Klebanoff's experiments have shown that the nonturbulent and large eddy components have a large influence on the streamwise intensities and little influence on the shear stress. Finally, predictions of the one-equation model were as good as those obtained by the stress model.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-2669 , AIAA Applied Aerodynamics Conference; Jun 22, 1992 - Jun 24, 1992; Palo Alto, CA; United States
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  • 6
    Publication Date: 2019-08-28
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 31; 4; p. 629-636.
    Format: text
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  • 7
    Publication Date: 2019-07-13
    Description: It is well known that current k-epsilon models cannot predict the flow over a flat plate and its wake. In an effort to address this issue and other issues associated with turbulence closure, a new approach for turbulence modeling is proposed which exploits similarities in the flow field. Thus, if we consider the flow over a flat plate and its wake, then in addition to taking advantage of the log-law region, we can exploit the fact that the flow becomes self-similar in the far wake. This latter behavior makes it possible to cast the governing equations as a set of total differential equations. Solutions of this set and comparison with measured shear stress and velocity profiles yields the desired set of model constants. Such a set is, in general, different from other sets of model constants. The rational for such an approach is that if we can correctly model the flow over a flat plate and its far wake, then we can have a better chance of predicting the behavior in between. It is to be noted that the approach does not appeal, in any way, to the decay of homogeneous turbulence. This is because the asymptotic behavior of the flow under consideration is not representative of the decay of homogeneous turbulence.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-191621 , NAS 1.26:191621 , AIAA Fluid Dynamics Conference; Jul 06, 1993 - Jul 09, 1993; Orlando, FL; United States
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  • 8
    Publication Date: 2019-07-12
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 27; 253-261
    Format: text
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