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  • 1
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    Axisymmetric inviscid swirling flows produced by bellmouth and centerbody (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The effect of large deformation in the flow between the bellmouth and centerbody is considered analytically for application to studies of vortex breakdown in a pipe. Basic equations are defined for axisymmetric inviscid swirling flows at the inflow and outflow sections. Axial and circumferential velocity component profiles are presented, and comparisons are made with trials involving vane angles of 42 deg and Re of 2300. Axial components of the prediction matched well in the inner half of the pipe radius and not well with the outer, while circumferential predictions were good only at the axis. A lack of viscosity was concluded to result in the inaccuracies near the wall.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 20; Apr. 198
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Numerical simulation of vortex breakdown by the vortex-filament method (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The vortex filament method was applied to the simulation of vortex breakdown. The principal vortex region was represented by multiple filaments, and an axial velocity component was induced by a spiral winding of the filaments. First, an accuracy check was performed for a cylindrical swirling flow with simple analytical expressions for the axial and theta velocities. The result suggests that the flow field is simulated to any accuracy by increasing the number of filaments. Second, an axisymmetric type vortex breakdown was simulated, with experimental data serving as upstream conditions. The calculated axial and theta velocity contours show the breakdown of the vortex, including a rapid change in the vortex core, followed axially by a recovery zone and then a second breakdown. When three dimensional initial data are used the second breakdown appears to be of the spiral type in correspondence with experimental observations. The present method is easily used to simulate other types of vortex breakdown or other vortex flows with axial velocity.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-84334 , A-9263 , NAS 1.15:84334 , AGARD Symp. on Aerodyn. of Vortical Type Flows in Three Dimensions
    Format: application/pdf
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  • 3
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    Vortex simulation of an inviscid shear layer (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The accuracy of the vortex-blob method was tested by simulating a free-shear-layer instability, Kirchhoff's elliptical vortex, and a circular vortex. The main numerical parameters in the vortex-blob method are the density of the vortices, and the distribution of vorticity within each vortex core. The growth rate of a periodic unstable mode of the shear layer was calculated numerically and compared with the exact result. The error is only a few percent for about 10 rows of vortex blobs. The error is reduced by decreasing the spacing between vortices and, correspondingly, the core size. In the simulation of the motion of the elliptical vortex, the rotation of the boundary, without change of shape, and the circular particle paths of the vortical fluid were well simulated. For the circular vortex, optimum sets of parameters were obtained by comparing them with the exact velocity. The results are consistent with convergence theories of the vortex-blob method. In particular, second-order convergence is observed with a Gaussian core from velocity calculation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 82-0948 , Joint Thermophysics, Fluids, Plasma and Heat Transfer Conference; Jun 07, 1982 - Jun 11, 1982; St. Louis, MO
    Format: text
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  • 4
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    Turbulent boundary layer around a group of obstacles in the direction of flow (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Results of an investigation of a boundary layer in a turbulent flow on the surface of a wall having a group of obstacles on the path of flow are presented with regard to the mean velocity field, velocity distribution of the two dimensional flow, wall surface shear stresses and Reynolds stresses measured in a downstream cross section where an interference of boundary layers takes place in a flow around adjacent obstacles arranged on the path of flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77016 , NAS 1.15:77016
    Format: application/pdf
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