> > A user would like to know where to find the definitions for
> > the COMMON blocks, internal parameters for STRMLN in version 3.1.
>
You could perhaps add to Don Ellison's comments.
The 4.0 'compatibility' version of strmln.f contains a discussion of
all the internal parameters of the old STRMLN routine, as follows:
C
COMMON /STR02/ EXT , SIDE , XLT , YBT
C
COMMON /STR03/ INITA , INITB , AROWL , ITERP , ITERC , IGFLG
+ , IMSG , UVMSG , ICYC , DISPL , DISPC , CSTOP
-----------------------
C
C INTERNAL PARAMETERS
C
C NAME DEFAULT FUNCTION
C ---- ------- --------
C
C EXT 0.25 Lengths of the sides of the
C plot are proportional to
C IPTSX and JPTSY except in
C the case when MIN(IPTSX,JPT)
C / MAX(IPTSX,JPTSY) .LT. EXT;
C in that case a square
C graph is plotted.
C
C SIDE 0.90 Length of longer edge of
C plot. (See also EXT.)
C
C XLT 0.05 Left hand edge of the plot.
C (0.0 = left edge of frame)
C (1.0 = right edge of frame)
C
C YBT 0.05 Bottom edge of the plot.
C (0.0 = bottom ; 1.0 = top)
C
C (YBT+SIDE and XLT+SIDE must
C be .LE. 1. )
C
C INITA 2 Used to precondition grid
C boxes to be eligible to
C start a streamline.
C For example, a value of 4
C means that every fourth
C grid box is eligible ; a
C value of 2 means that every
C other grid box is eligible.
C (see INITB)
C
C INITB 2 Used to precondition grid
C boxes to be eligible for
C direction arrows.
C If the user changes the
C default values of INITA
C and/or INITB, it should
C be done such that
C MOD(INITA,INITB) = 0 .
C For a dense grid try
C INITA=4 and INITB=2 to
C reduce the CPU time.
C
C AROWL 0.33 Length of direction arrow.
C For example, 0.33 means
C each directional arrow will
C take up a third of a grid
C box.
C
C ITERP 35 Every 'ITERP' iterations
C the streamline progress
C is checked.
C
C ITERC -99 The default value of this
C parameter is such that
C it has no effect on the
C code. When set to some
C positive value, the program
C will check for streamline
C crossover every 'ITERC'
C iterations. (The routine
C currently does this every
C time it enters a new grid
C box.)
C Caution: When this
C parameter is activated,
C CPU time will increase.
C
C IGFLG 0 A value of zero means that
C the sixteen point Bessel
C Interpolation Formula will
C be utilized where possible;
C when near the grid edges,
C quadratic and bi-linear
C interpolation will be
C used. This mixing of
C interpolation schemes can
C sometimes cause slight
C raggedness near the edges
C of the plot. If IGFLG.NE.0,
C then only the bilinear
C interpolation formula
C is used; this will generally
C result in slightly faster
C plot times but a less
C pleasing plot.
C
C IMSG 0 If zero, then no missing
C U and V components are
C present.
C If .NE. 0, STRMLN will
C utilize the
C bi-linear interpolation
C scheme and terminate if
C any data points are missing.
C
C UVMSG 1.E+36 Value assigned to a missing
C point.
C
C ICYC 0 Zero means the data are
C non-cyclic in the X
C direction.
C If .NE 0, the
C cyclic interpolation
C formulas will be used.
C (Note: Even if the data
C are cyclic in X, leaving
C ICYC = 0 will do no harm.)
C
C DISPL 0.33 The wind speed is
C normalized to this value.
C (See the discussion below.)
C
C DISPC 0.67 The critical displacement.
C If after 'ITERP' iterations
C the streamline has not
C moved this distance, the
C streamline will be
C terminated.
C
C CSTOP 0.50 This parameter controls
C the spacing between
C streamlines. The checking
C is done when a new grid
C box is entered.
C
C DISCUSSION OF Assume a value of 0.33 for DISPL. This
C DISPL,DISPC means that it will take three steps to move
C AND CSTOP across one grid box if the flow was all in the
C X direction. If the flow is zonal, then a
C larger value of DISPL is in order.
C If the flow is highly turbulent, then
C a smaller value is in order. The smaller
C DISPL, the more the CPU time. A value
C of 2 to 4 times DISPL is a reasonable value
C for DISPC. DISPC should always be greater
C than DISPL. A value of 0.33 for CSTOP would
C mean that a maximum of three stream-
C lines will be drawn per grid box. This max
C will normally only occur in areas of singular
C points.
C
C ***************************
C Any or all of the above
C parameters may be changed
C by utilizing common blocks
C STR02 and/or STR03
C ***************************
C
C UXSML A number which is small
C compared to the average
C normalized u component.
C Set automatically.
C
C NCHK 750 This parameter is located
C in STDRAW. It specifies the
C length of the circular
C lists used for checking
C for STRMLN crossovers.
C For most plots this number
C may be reduced to 500
C or less and the plots will
C not be altered.
C
C ISKIP Number of bits to be
C skipped to get to the
C least two significant bits
C in a floating point number.
C The default value is set to
C I1MACH(5) - 2 . This value
C may have to be changed
C depending on the target
C computer; see subroutine
C STDRAW.
C
C --------------------------------------------------------------------
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