A pressure profile input file must consist of two lines:

the first line must begin with time and should be followed by space-separated real scalars, giving the times (in s after the start of the simulation) of the pressure set points — the times must be in increasing order
the second line must begin with pressure and should be followed by space-separated real scalars, giving the pressures (in Pa) at the corresponding times

The pressure profile is linearly interpolated between the specified times, while before the first time it takes the first pressure value and after the last time it takes the last pressure value.

Example:

 time      0    600  1800  # time (in s) after simulation start
 pressure  1e5  9e4  7.5e4 # pressure (in Pa)

Here the pressure starts at 1e5 Pa at the start of the simulation, decreases to 9e4 Pa after 10 min, and then decreases further to 7.5e4 Pa at 30 min. Between these times the pressure is linearly interpolated, while after 30 min it is held constant at 7.5e4 Pa.