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``` TALK=F;RUN(1,1)

TEXT( Library case Y601: TIME STEP CALCULATIONS

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PLANT information :
* Data input groups used:  2, 19
* Ground groups planted :  1, 2, 19-3
* Functions used : SUM
* Commands used  : IF, REGION, TEXT.

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GROUP 2. Transience; time-step specification
LSTEP=2
TLAST=GRND
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The above three lines will instruct EARTH to perform 2 time steps,
the size of which being determined by the settings PLANTed in group
2.
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** Ask PLANT to introduce first time step, 5 seconds.
DT=5.
REGION(1,1,1,1,1,1,1,1)
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REGION command is used to control this simple setting. Its first six
arguments limit DO loop to perform single action over first time
step defined by the last argument pair.
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** Choose the smallest cell size at the start of each iz-slab
for the last sweep of the first time step.
RG(1)=GREAT
DXG2D - cell size in X-direction,
DYG2D - cell size in Y-direction,
DZWNZ - cell size in Z-direction,
RG(1)=AMIN1(RG(1),DXG2D,DYG2D,DZWNZ)
IF(ISTEP.EQ.1.AND.ISWEEP.EQ.LSWEEP)
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Command IF restricts the whole-domain-default extents of PLANT
statement. The arguments of IF command instruct PLANT to introduce
the logical conditions of the bracketed expression. The execution of
the statement returns the auxilliary variable, RG(1), with the
smallest cell size over the whole domain.
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** Output of smallest cell size using summation in one cell
at 1st time step, last sweep  for checking.
SIZMIN=SUM(RG(1))
TEXT(Smallest cell size)
REGION(1,1,1,1,1,1,1,1) /ISWEEP.EQ.LSWEEP
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The function SUM is used in above three lines just to dump into
globcalc file the value of RG(1) headed by the character arguments
of TEXT command.
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** Choose the largest velocity value just before the second
time step calculation
RG(2)=AMAX1(RG(2),U1,V1,W1)
IF(ISTEP.EQ.2)
** Output the largest velocity using summation in one cell
at 2nd time step for checking.
VELMAX=SUM(RG(2))
TEXT(Largest velocity)
REGION(1,1,1,1,1,1,2,2)
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Auxiliary variable, RG(2), will be the largest velocity value as
result of the above statements at the second time moment. It will be
dumped in globcalc file and appropriately headed.
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DT=SIZMIN/VELMAX
REGION(1,1,1,1,1,1,2,2)
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The final stage of time step settings: second time step size, DT, is
set as division of smallest size by largest velocity.
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** The simple non-uniform grid with smallest cell size of 1 m.
GROUP 3. X-direction grid specification
GRDPWR(X,2,2.,1.)
GROUP 4. Y-direction grid specification
GRDPWR(Y,2,4.,1.)
GROUP 5. Z-direction grid specification
GRDPWR(Z,2,6.,1.)
GROUP 7. Variables stored, solved & named
SOLVE(H1)
STORE(U1,V1,W1)
GROUP 11. Initialization of variable or porosity fields
** The simple non-uniform velocity field with maximum
value, 10.0m/s, at east-south-high corner of the domain.