How would we make the Time force profile for a slug loading .

In case of surge ,the time-history profile in tabulated form is like:
time Force factor
0 0
Tr 1
Tr+L/C 1
Tr+L/C+Tr 0

But in case of slug the profile is like below:

time Force factor
0 0
tg O,1
Tg+tl 1,0

tg= time duration of gas
tl = time duration of liquid(slug)
As the profile of the graph has got a slope of 90 deg, it is not possible without assuming a delta time value to make the tabulated form to feed it in Caesar spread sheet.

It can be made like:
time Force factor
0 0
tg 0
Tg+ delta time 1
Tg+ delta time+tl 1
Tg+ delta time+tl+delta time 0

Now the question is: how much should be the delta time? should we assume it as close to zero like 0.1 ms ???? so that Force Time profile resembles the square wave .Or should be consider that the slug leading edge does not perpendicular to the flow so the Force time profile will similar to the profile of surge i.e. trapezoidal .