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Sub-grids, setting of

(see SUBGRD command)

SUBGRD: The SUBGRD extension to GRDPWR

SUBGRD facilitates the distribution of grid intervals for a succession of segments in each direction. All the user has to do is to insert a series of SUBGRD commands.

This feature is especially useful when the grid has to accord with the geometric positions of the corners of solid bodies placed within the flow domain. The user can start by concentrating his attention on these locations, and defining his boundary-condition and source patches in terms of the corner indices, expressed in symbolic terms.

When all that is done, he can consider what values he wishes to ascribe to the indices and exponents in order to produce the required fineness and distribution of grid.

The syntax is : SUBGRD(DIR,L1,L2,DIST,POW)

This sets GRDPWR-type grids over a portion of the grid. DIR is the direction, and may be X,Y,Z or T. L1 and L2 are the first and last cells in the section of sub-grid. L1 must always be (L2+1) of the previous section. SUBGRD automatically resets NX,NY,NZ or LSTEP to the current running total number of cells. DIST is the distance over which the current sub-grid extends. XULAST, YVLAST, ZWLAST or TLAST are reset internally to the new total distance, and the corresponding FRAC array is rescaled to be between 0 and 1.
See GRDPWR for further information.
Symmetrical power-law grids can be obtained by setting L2 to be negative.

SUBGRD has now been superseded by GRDPWR used in conjunction with NREGT and IREGT; however, it is still available, for compatibility with Q1 files written for version 1.5.