NUMERICAL SMOOTHING OF FLOW PATTERNS

Two strategies are presented for smoothing the flow patterns obtained from grids photographically deposited on aluminium that is extruded through wedge shaped dies. The objective of the numerical procedures is to remove small irregularities from the flow and so smooth the data sufficiently to permit reasonably accurate computations of the strain-rates, total strains and directions of maximum shear strain-rate for use in further investigations of the flow fields. The strategies are based on the equalisation of the curvilinear quadrilateral areas which make up the flow pattern. In the first, the areas are computed using spline approximations to the segments of streamlines and transverselines whilst in the second the data sets are augmented by interpolating additional streamlines and transverselines between the original areas, and the areas computed using straight line approximations. Results from 30 and 60 degree half die angle extrusions are analysed and the strategies are shown to effectively smooth the flow as indicated by several quantitative and qualitative measures. The distributions of strain-rate, total strain and directions of maximum shear strain rate are more readily interpreted and applicable for further analysis. © 1979.