`Demonstration of progressive tank filling where an air bubble
`gets trapped in a portion of the tank.  The portion of the
`tank where the air bubble forms is modeled as a separate tank
`and its load level is calculated with respect to the pressure
`in the air bubble.

project TANKTRAP

enter pm
loa 999
create tank1a.s
 loc @  0 = 0 0, 20,0, 20,30, 10,30, 10,10, 0,10
 loc @ 10 = 0 0, 20,0, 20,30, 10,30, 10,10, 0,10
 tube 5,15,0,  5,15,30
/
create tank1b.s
 loc @  0 = 0 10, 10,10, 0,12
 loc @ 10 = 0 10, 10,10, 0,12
/
write tanktrap.gf
quit pm
display

variable ds, ds1, y, k, v0, dh1, l1

set k = 33.9 times 1.025 `Head of water per atmosphere of pressure.

macro bubble
 `%1 - sounding in main tank
 `%2 - height ABL of bottom of bubble tank
 `%3 - full volume of bubble tank
 set ds = %1 minus %2 minus {ds1} `Effective head above bottom of bubble tank
 if {ds}<0 then load 0 | exit
 set y = {ds} div {k} plus 1 `Pressure in atmospheres
 set y = %3 div {y} `Volume of air V = V0/P
 set y = %3 minus {y} `Volume of water
 load vol:{y}
 set ds1 = minus {height} `Level of water above bubble tank's bottom
/

macro bload1
 `%1 - bubble tank name
 `%2 - height of bottom of bubble tank above bottom of sounding tube
 `%3 - longitudinal center of tank for viewing cross section
 tank %1
 ref bottom
 load 1
 set v0 = {tvolume} `maximum volume of air bubble
 set dh1 = %2
 set l1 = %3
/

macro bload2
 `%1 - sounding
 `%2 - name of main tank
 `%3 - name of bubble tank
 load (%2) snd:%1 `load main portion of tank by sounding
 tank %3
 set ds1=0
 .bubble (3) %1, {dh1}, {v0} `do the bubble macro multiple (3) times to converge ds1
 display (*) status body @ {l1} /yesempty
/

.bload1 tank1b.s, 10, 5
.bload2 (6,4) 9, tank1a.s, tank1b.s

end