Transition Zone NTRANS
When the entire surface or edge of a system is not a design zone and both design and non-design regions exist adjacent to one another, a transition zone can be defined using NTRANS which helps to smooth out the transition. Sharp changes can occur in the design region during optimization and the sections of the design region closest to the non-design region are designated as a transition zone where the corresponding location of the adjacent non-design region is taken into consideration allowing for a smoother transition from the design to non-design region. NTRANS defines the number of design grid layers in the transition zone to non-design area, where additional treatment will be applied to produce smooth transition.
NTRANS = 3
Side Constraints
Side constraints allow the deformation space to be defined as a coordinate range. Similar to the maximum shrinkage and growth parameters as defined on the PERT continuation line, it is possible to limit the extent of the total deformation of the design region by way of side constraints. Side constraints allow the deformation space to be defined as a coordinate range; that is, between (x1, y1, z1) and (x2, y2, z2). These ranges may be with reference to rectangular, cylindrical or spherical systems.
Move Factor MVFACTOR
The maximum allowable movement in one iteration of the grids defining a free-shape design region is specified as: MVFACTOR * mesh_size. The default value of MVFACTOR is 0.5. A smaller MVFACTOR will make free-shape optimization run slower but with more stability. Conversely, a larger MVFACTOR will make free-shape optimization run faster but with less stability.
Number of Layers for Mesh Smoothing NSMOOTH
With free-shape optimization, internal grids adjacent to those grids defining the design region are moved to avoid mesh distortion. The number of layers of grids to be included in the mesh smoothing buffer may be defined by the NSMOOTH field on the PERT continuation line of the DSHAPE entry. The default value of NSMOOTH is 10. A larger NSMOOTH will give a larger smoothing buffer, and consequently will work better in avoiding mesh distortion; however, it will result in a slower optimization.
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